Mechanisms, causes, investigation and management of vomiting disorders in cats: a literature review

Abstract

Vomiting is a common presenting complaint in feline practice. This article differs from previous reviews in that it is an evidence-based review of the mechanisms, causes, investigation and management of vomiting in the domestic cat. Published evidence was reviewed, and then used to make recommendations for clinical assessment, diagnosis, antiemetic drug treatment, dietary management and monitoring of cats presenting with vomiting. The strength of the evidence on which recommendations are made (and areas where evidence is lacking for cats) has been highlighted throughout.

Introduction

Vomiting is a common presenting complaint in feline practice and occurs in an enormous range of disease processes. It is amongst the most common clinical signs reported in cats examined at private veterinary practices. ¹ The aim of this study was to perform an evidence-based review of the mechanisms, causes, investigation and management of vomiting in the domestic cat. In each area recommendations have been made, and the strength of the published literature, upon which the recommendations were based, has been presented.

Methods

A systematic literature search was performed in PubMed using the search terms [(‘vomit*’ OR ‘emesis’) AND (‘cat’ OR ‘feline’)] and [‘antiemetic*’ AND (‘cat’ OR ‘feline’)]. All articles relevant to domestic cats were collected, ignoring those dealing solely with captive large felids. Only articles relevant to actual vomiting (defined for these purposes as the forceful ejection of stomach contents via the mouth) were considered; any articles that dealt solely with nausea were not included. Similar searches were made in the Centre for Agricultural Bioscience International database (CAB direct), Google Scholar and Web of Science, identifying additional references not listed in PubMed. To indicate the strength of available evidence in support of the statements and recommendations made, references were assigned a level of evidence (LOE), and an overall evidence grade (OEG) for each aspect was also assigned (Table 1), as described previously. ²

Table 1.

Scheme used to grade level of evidence for individual references and overall level of evidence (adapted)^2,255

(a) Study type	Level of evidence
Systematic review (with homogeneity) of randomised controlled clinical trials (RCT)	1a
Individual RCT (with narrow confidence interval)	1b
All or none*	1c
Systematic review (with homogeneity) of cohort studies	2a
Individual cohort study (including low quality RCT, eg, <80% follow-up) or well-controlled laboratory study	2b
‘Outcomes’ research; ecological studies	2c
Systematic review (with homogeneity) of case-control studies	3a
Individual case-control study or weak laboratory study	3b
Case series >50 cases	4a
Case series 20–50 cases	4b
Case series <20 cases	4c
Single published case report	4d
Expert opinion without explicit critical appraisal, or based on physiology, bench research or ‘first principles’	5
(b) Types of study	Overall evidence grade
Consistent RCT, cohort study, all or none,* decision rule validated in different populations	A
Consistent retrospective cohort, exploratory cohort, ecological study, outcomes research, good laboratory study, case-control study, or extrapolations from level A studies	B
Case series study or extrapolations from level B studies	C
Expert opinion without explicit critical appraisal, or based on physiology, bench research or first principles	D

^*The all or none principle is met when all patients died before the treatment became available, but some now survive on it; or when some patients died before the treatment became available, but none now die on it

The emetic reflex and causes of vomiting

Vomiting in cats is a complex reflex involving the gastrointestinal system, respiratory and abdominal muscles, and changes in posture [2b^3–6]. Some of these coordinated reflex events are a reduction in gastric motility, retrograde movement of gut contents from the proximal intestine to the stomach, and relaxation of the gastro-oesophageal junction followed by expulsion of gastric contents brought about by forceful contractions of the diaphragm and abdominal muscles, and closure of the glottis [2b^3,5–13] [OEG B].

Vomiting may be triggered by peripheral stimuli, such as afferent neural input from the gastrointestinal tract or other visceral organs, or central stimuli, such as circulating toxins that activate the central nervous system (CNS) via the area postrema (AP) [2b^8,13,14]. The AP is a bilateral structure adjacent to the fourth ventricle, considered to be outside the CNS because it lacks a blood–brain barrier [2b ¹⁵ ]. It is a chemoreceptive area that triggers vomiting, and its ablation abolishes the emetic response to most (but not all) emetogens [2b^16–19]. Vestibular stimuli (motion sickness) can also cause vomiting in cats, although susceptibility varies between individuals [2b^20,21]. The AP is not involved in motion sickness [2b^22,23]. As in other species, input from midbrain or forebrain structures also may trigger vomiting [2b^6,13] [OEG B].

Regardless of how it is triggered, the motor act of vomiting is coordinated at the level of the brainstem by the same set of structures [2b ⁶ ]. In cats, vomiting is coordinated by a distributed control system, not a discrete vomiting centre: neurons activated during vomiting are distributed in the brainstem in an area extending from the AP and dorsal motor nucleus of the vagus through the nucleus of the solitary tract (NTS) and lateral tegmental field of the reticular formation to the region of the retrofacial nucleus in the ventrolateral medulla [2b^18,19,24]. This area also contains neurons controlling related functions, such as respiration, cranial nerve integration, swallowing and salivation [2b ¹⁹ ]. The NTS is thought to be the beginning of a final common pathway by which different triggers produce vomiting, and receives inputs from sources that can trigger vomiting, such as the vagus nerve, the AP, and vestibular and limbic systems [2b^{6,18,23,25–27}] [OEG B].

The conditions that have been reported to be associated with vomiting in cats are listed in Tables 2–4, mostly at LOE grade 4 or 5. Based upon these reports, the most common causes include adverse reactions to food [4b ²⁸ , 4c^29–33], infectious agents (such as feline panleukopenia virus [4b ³⁴ ] and feline infectious peritonitis virus [4c ³⁵ ]), and acute self-limiting emesis of undetermined cause (so-called ‘acute gastritis’)[5]. Compared with other veterinary species, cats frequently vomit trichobezoars (hairballs) [4c ³⁶ ], probably because of their fastidious grooming behaviour. They do not commonly ingest foreign bodies, but when they do, linear foreign bodies (string, sewing thread) are often reported [4a ³⁷ , 4b ³⁸ ]. Furthermore, cats frequently vomit after administration of α² adrenergic drugs [2b^21,39–42, 4a ⁴³ ], reflecting the importance of these receptors in the brainstem areas controlling vomiting. The most common causes of chronic vomiting in cats seem to be idiopathic inflammatory gastritis or enteritis (‘inflammatory bowel disease’) [4a ⁴⁴ , 4b^45–47, 4c^29,48,49], adverse reactions to food [4b ²⁸ , 4c^29–32], liver disease [2b ⁵⁰ , 4a^51,52, 4b^53–55, 4c^56–62, 4d^{56,58,63–70}] and uraemia [2b ⁷¹ , 4a^72,73, 4b^74,75, 4c ⁷⁶ , 4d^77,78]. Hyperthyroidism is common in cats and is also associated with vomiting [4a^79,80] [OEG D].

Table 2.

Alimentary tract conditions that have been associated with vomiting in cats

Disorder	Processes	Level of evidence and reference(s)	Overall evidence grade
Colonic obstruction		4c 256 , 4d 257 , 5 166	C
Congenital abnormalities		4d 119	D
Dietary	Food sensitivity Refeeding/enteral tube feeding Dietary indiscretion	4b 28 , 4c29–32 4a217,218,258, 4b 259 4c 33	C
Feline acute haemorrhagic vomiting syndrome	Syndrome of self-limiting acute vomiting often with fresh blood, occurring in outbreaks in rescue shelters and catteries; recently recognised in the UK, aetiology not yet known	5 260	D
Foreign body	Linear foreign bodies Trichobezoars Enterolithiasis	4a 37 , 4b 38 4c 36 4d 261	C
Gastric entrapment	Diaphragmatic rupture Gastro-oesophageal intussusception Gastric dilatation/volvulus Hiatal hernia	4c 262 , 4d 263 4d137,138,264 4c 265 4c266–268, 4d 269	C
Gastritis	Acute Lymphocytic-plasmacytic Eosinophilic Parasitic Associated with spiral bacteria Associated with foreign body Gastroduodenal ulceration Hyperplastic gastropathy	5201,202 4d 141 4d 270 4c146,271,272, 4d 273 4c117,118 4c 156 4d 274	D
Inflammatory bowel disease		4a 44 , 4b45–47, 4c29,48,49	C
Infection	Coronavirus Intestinal mural lesions caused by feline infectious peritonitis Feline panleukopenia virus Bacterial Yeasts Ollulanus tricuspis Other parasites	4c125,274 4b 275,276 4b 34 , 5 122 4a 277 , 4c 278 4d 279 4c 271 4a123,280,281, 4c 146 , 4d 224	C
Intestinal strangulation		4d 282	D
Intussusception		4b120,121, 4c 283	C
Neoplasia	Gastric polyps Gastric neoplasia Intestinal neoplasia	4d 284 4b 285 , 4c126,145 4d143,232,233,286,287 4b142,164, 4c128,131,165 4d144,151,157	C
Pyloric stenosis/dysfunction		4c129,130,288,289	C
Small bowel infarction		4d290,291	D
Zollinger–Ellison syndrome		4d236,292	D

Table 3.

Non-alimentary tract abdominal disease conditions that have been associated with vomiting in cats

Disorder	Process	Level of evidence and reference(s)	Overall evidence grade
Adrenal gland tumour	Adrenocortical tumour Extra-adrenal phaeochromocytoma	4d 81 4d 293	D
Hepatobiliary disease	Chronic hepatitis Cholangitis/cholecystitis Extrahepatic biliary tract obstruction Cysts Neoplasia Hepatic lipidosis Peritoneopericardial diaphragmatic hernia Biliary atresia Biliary cirrhosis Liver flukes	4d 56 4c, 57 4d 58 2b 50 , 4b53,54, 4c59,159,223,294, 4d63–65 4c60,229, 4d 66 4b 55 , 4c 61 , 4d67,68 4a 51 , 4d69,158 4d 295 4d 70 4c 62 4a 52 , 4c 223	B
Mesothelioma		4d 296	D
Pancreatic disease	Pancreatitis Cyst Neoplasia Exocrine pancreatic insufficiency Pancreatic fluke	2b 153 , 4a 297 , 4c 298 , 4d299–301 4d 152 4c 150 4c 302 4d 303	B
Peritonitis	Bacterial Mycobacterial Actinomycetoma Parasitic Sclerosing peritonitis Haemoperitoneum	4a 304 , 4b155,163 4d 305 4d 306 4d 307 4d 161 4a 162	C
Renal disease	Neoplasia Cysts	4d82,83 4c 229	C
Splenic disease	Neoplasia Foreign body	4c 91 4d 92	C
Steatitis		4d 308	D
Urogenital disease	Uroperitoneum Ureteroliths/ureteral obstruction Herniated bladder Urethral obstruction Congenital abnormalities Endometrial polyps Uterine adenomyosis Uterine rupture Pyometra Prostatic abscess	4c 160 4a 309 , 4d 310 4d 148 2b 71 , 4d 134 4d132,225 4c 311 4d 133 4d 312 4a 313 , 4c 314 4d 110	C

Table 4.

Systemic and other disease conditions that have been associated with vomiting in cats

Disorder	Process	Level of evidence and reference(s)	Overall evidence grade
Cardiorespiratory	Chronic nasal disease Heartworm disease (Dirofilaria immitis) Hypertrophic cardiomyopathy Pyothorax Thoracic tumours Aortic thromboembolism Bronchial disease	4a 111 4a 315 , 4b 316 , 4c 317 , 5 230 4d 289 4b 112 4d234,237,318,319 4b 113 , 4c 114 4a 115 , 4b 116	C C C C C C C
Drug-induced	Xylazine Medetomidine Cancer chemotherapeutics NSAIDs Cabergoline Glipizide Digitalis Ciclosporin Numerous others	2b21,39–41 2b 42 , 4a 43 2b178,221,239,240,245,252, 4a 240 4b 320 , 4c246,247,321 4b322,323 2b 324 4a 325 2b 326 4b 327	B B B C B C B C
Infection	Virulent calicivirus FeLV FIV FIP Disseminated mycobacterial infection Toxoplasmosis Anaplasma phagocytophilum Trypanosoma evansi Tularaemia Ehrlichiosis Histoplasmosis	4b 93 , 4c 94 4d 95 4a 96 4c 35 4c 97 , 4d98–100 4d269,101,102 4d 103 3b 104 4c 105 4b 106 , 4d 107 4d108,109	C D C C C C C C C C D
Metabolic	Acute uraemia — vomiting frequently seen Chronic uraemia — vomiting seen in <1/3 of cases Ketoacidosis Hyperthyroidism Hepatic encephalopathy Hypoadrenocorticism Hypercalcaemia Hypocalcaemia Hyperkalaemia Septicaemia/enterotoxaemia Vitamin D deficiency Hyperviscosity	2b 71 , 4b 74 , 4c 76 4a72,73, 4b 75 , 4d77,78 4a 147 4a79,80 5 4c 328 , 4d 329 4c 236 , 4d149,228,238,330–332, 5 333 4a 335 4c 335 4a 336 , 4c 337 4d 338 4c 339	B C C C D C C C C C D C
Neoplastic	Leukaemia Histiocytic disease Hypereosinophilic syndrome Lymphoma Systemic mastocytosis	4d84,85 4d 86 4c 87 , 4d88–90 4b 127 , 4c 340 , 4d 341 4c 342 , 4d343,344	C D C C C
Neurological disorders	Motion sickness Vestibular disease Dysautonomia Brain lesions	2b20,180,184,187,345 4a 346 4c347,348 4d349,350	B C C D
Parenteral nutrition		3b 351	B
Radiation-induced emesis		2b 352	B
Snake envenomation		4b 353 , 4d 354	C
Toxic	Lilies Lead Others	2b 226 4a 355 4c 356 , 4d 357	B C
Transfusion reaction		2b 358	B

NSAIDs = non-steroidal anti-inflammatory drugs; FeLV = feline leukaemia virus; FIV = feline immunodeficiency virus; FIP = feline infectious peritonitis

Although most causes of vomiting are likely to be the result of the diseases listed above, clinicians should be aware of the many other conditions where vomiting has also been reported (Tables 2–4). Most notably, vomiting has been associated with many non-alimentary diseases, either involving other abdominal organs (Table 3) or other systemic conditions (Table 4), including various types of neoplasia [4c ⁸⁷ , 4d^81–90], splenic disease [4d^91,92], many infectious disorders [3b ¹⁰⁴ , 4a ⁹⁶ , 4b ⁹³ , ¹⁰⁶ , 4c ³⁵ ,^94,105, 4d ⁹⁵ ], prostatic abscessation [4d ¹¹⁰ ], chronic nasal disease [4a ¹¹¹ ], pyothorax [4b ¹¹² ], aortic thromboembolism [4b ¹¹³ , 4c ¹¹⁴ ] and bronchial disease [4a^115,116]. While these tables can serve as a broad indication of possible differential diagnoses, associations should be made cautiously. In this respect, most of these reports are from isolated case series or single case reports and, as a result, it is impossible to determine the relative importance of these disease associations. Furthermore, the reason for the vomiting is often not explored in detail and may, in fact, have been incidental to the case. For example, two reported infectious causes of vomiting are gastric spiral organisms^117,118 and Ollulanus tricuspis, ²⁷¹ although the evidence in support of a causal link is weak. Indeed, in one of the articles regarding gastric spiral organisms, the authors highlight the fact that other reasons for vomiting were not adequately excluded. ¹¹⁷ Furthermore, in the single article reporting an association between O tricuspis infection and vomiting [OEG 4c ²⁷¹ ], only two of the four cats vomited, and both of these cats responded to dietary manipulation.

Clinical presentation and initial assessment

During the initial assessment of cats with vomiting, the severity of the disease process should be determined, with the aim of differentiating those cats that need limited further examination and can be treated symptomatically from those that need extensive investigations or therapy. Although not its primary purpose, the initial assessment may also give a clear indication as to the underlying cause of the vomiting [OEG D].

Assessment starts with the age, breed and gender of the cat, along with presence of signs in other cats in the household. Age is important because some diseases are more common in young cats, such as ingestion of foreign bodies [4a ³⁷ ], intussusception [4b ¹²⁰ , 4c ¹²¹ ] or infectious diseases, such as panleukopenia virus [5 ¹²² ], parasites [4a^123,124] or coronavirus enteritis [4c ¹²⁵ ], while other diseases, such as hyperthyroidism or gastrointestinal or hepatobiliary neoplasia, are more common in older cats [4b ⁵⁵ , ¹²⁷ , 4c ¹²⁶ , ¹²⁸ ] [OEG C]. Breed is an important consideration: Siamese cats are predisposed to gastrointestinal adenocarcinoma [4c ¹²⁶ ] and to pyloric stenosis [4c^129,130]; lymphoplasmacytic gastroenteritis is more commonly seen in purebred cats [4c ⁴⁸ ]; and adenomatous polyps of the duodenum are seen more in cats of Asian ancestry [4c ¹³¹ ] [OEG C]. Adenomatous polyps of the duodenum are more commonly seen in castrated males [4b ¹³¹ ] and, not surprisingly, some disorders only affect one gender, such as uterine abnormalities [4d^132,133] or prostatic disease [4d^110,134] [OEG C].

A complete history is essential for evaluation of a vomiting cat. Information that should be obtained is listed in Table 5. The distinction between vomiting and regurgitation is less clear in cats than in dogs, and cats with megaoesophagus, oesophagitis or hiatal hernia are often reported as vomiting [4b ¹³⁵ , 4c ¹³⁶ , 4d^137–139]. A sudden onset of vomiting can suggest dietary indiscretion [4c ¹⁴⁰ ]. Acute onset of vomiting is also seen with intestinal foreign bodies in cats, and the vomiting tends to be persistent and severe [4a ³⁷ ]. Furthermore, in approximately one third of cases, the owner either reports seeing the foreign body or it is identified during the physical examination (at the mouth or anus) [4b ³⁸ ]. Intermittent vomiting or recurrent episodes more often suggests a chronic alimentary tract disorder, for example, inflammatory bowel disease (IBD) [4d ¹⁴¹ ], gastrointestinal neoplasia [4b ¹⁴² , 4d^143,144] or hepatobiliary disease [4b ⁵⁵ ]. Furthermore, when haematemesis or melaena are present, gastric adenocarcinoma [4c ¹⁴⁵ ], gastric ulceration [5], Physaloptera preputialis infection [4c ¹⁴⁶ ] or gastrointestinal polyps [4c ¹³¹ ] should be considered; in contrast, haemorrhagic diarrhoea (large volumes of fresh blood) can indicate panleukopenia infection [5 ¹²² ] and, occasionally, linear foreign bodies [4b ³⁸ ]. Given the wide array of possible causes of vomiting (Tables 2–4), clinicians should also pay attention to the presence of other clinical signs. For instance, polydipsia may suggest a systemic disorder, such as renal disease [4d^77,78], hyperthyroidism [4a^79,80] or diabetes mellitus [4a ¹⁴⁷ ], while lower urinary tract disorders should be considered if there is dysuria, pollakiuria or stranguria [4d^134,148,149]. In such cases, there may also be associated physical examination findings, such as a distended painful bladder in cases of urethral obstruction [4d ¹³⁴ ].

Table 5.

History taking for the vomiting cat

A thorough history should be obtained during the initial assessment, including the following:	Rationale [level of evidence/reference]	Overall evidence grade
Distinguish vomiting from regurgitation	Not always easy in cats. The presence of regurgitation suggests oesophageal disease [4b 135 ]	C
Onset and progression of signs	Sudden onset can suggest ingestion of foreign body or dietary indiscretion [4c 140 ] Chronic or recurrent vomiting may indicate the presence of a chronic gastrointestinal problem, eg, intestinal adenocarcinoma [4b 142 ], other intestinal tumour [4d 144 ], gastrinoma [4d 292 ], gastric carcinoid [4d 143 ] or a hepatobiliary mass [4b 55 ] Persistent vomiting can be seen in cats which have ingested thread and sewing needles [4a 37 ] Chronic intermittent vomiting can be seen with IBD, eg, lymphoplasmacytic gastritis [4d 141 ]	C
Description of the vomitus	Presence of bile suggests patent pylorus [5] Faecal odour may suggest obstruction [5]	D
Haematemesis	Can be seen with gastric adenocarcinoma [4c 145 ], gastric ulceration [5], intestinal polyps [4c 131 ] and feline acute haemorrhagic vomiting syndrome [5 260 ]	C
Relationship to eating	Vomiting food >12 h after eating suggests delayed gastric emptying [5]	D
Concurrent constipation and tenesmus	Can be found in cats with colonic adenocarcinoma [5 166 ], megacolon [5 359 ] or other gastrointestinal obstruction [4c 255 ] Tenesmus may be seen with prostatic disease or sublumbar masses [4d110,134,257]	C
Presence of diarrhoea	Diarrhoea may suggest concurrent intestinal disease [4c48,121,128, 4d 151 , 5 122 ]	C
Bloody diarrhoea	Can be seen in feline panleukopenia infections [5 122 ] Can be seen in some cats with linear foreign body [4b 38 ]	C
Melaena	Can be seen with gastric adenocarcinoma [4c 145 ] Can be seen in cats with Physaloptera preputialis nematodes [4c 146 ]	C
Appetite, nutritional status and weight loss	Weight loss associated with gastrointestinal tumour [4c 126 ], intussusception [4b 120 ], chronic diaphragmatic hernia [4c 262 ], hepatic lipidosis [4a 51 ], various malignancies (including intestinal adenocarcinoma [4b 142 ] and lymphoma [4c 128 , 4d 151 ]), parasitic infestation of the stomach [4c146,271,360] and Mycobacterium species infection [4d 305 ], many other diseases	C
Fluid intake (increased, decreased or normal)	Polydipsia may be seen with kidney disease [4d77,78], hyperthyroidism [4a79,80] or diabetes mellitus [4a 147 ]	C
Micturition behaviour, dysuria, anuria	May be a sign of feline lower urinary tract disease, including urethral obstruction or herniation of the urinary bladder in the inguinal canal [4d134,148,149] Anuria can be seen in rupture of bladder or urethra [4b 160 ]	C
Presence of abdominal pain	Abdominal pain can be seen in pancreatitis [2b 153 ] or with intussusception [4b 120 ]	B
Diet changes, recent drug therapy, access to toxins or foreign bodies	Change in diet can cause vomiting [5] Trichobezoars can cause vomiting [4c 36 ] Scavenging on chicken remnants can cause enterotoxaemia [4c 361 ] The owner observes the linear foreign body in a third of cases [4b 38 ] Postoperative vomiting reported after extrahepatic biliary tract surgery [4c 362 ] and ovariohysterectomy (if concurrent ureteral obstruction or section [4d 310 ])	C
Vaccination status	Feline panleukopenia virus enteritis more likely to be seen in unvaccinated cats than in vaccinated cats [5 122 ]	D
Concurrent dermatological signs	Concurrent occurrence of gastrointestinal and dermatological signs can suggest an adverse reaction to food [4c30,31]	C
History of hypertrophic cardiomyopathy and aortic thromboembolism	Secondary small bowel infarction [4d 290 ]	D
Ptyalism and depression	Can be seen in hepatoencephalopathy [4a 51 ] Depression is mentioned in many disease conditions	C
Outdoor cat	This may suggest trauma leading to diaphragmatic hernia, septic peritonitis, bladder rupture [4b 155 ]	C
Hormonal treatment for oestrus prevention	Uterine abnormalities such as pyometra [4c 314 ]	D
Vaginal bleeding, vulvar discharge	Can be seen with endometrial polyps [4c 311 ] and pyometra [4c 314 ]	C

Physical examination is important and should include assessment of the features shown in Table 6. Abdominal palpation is of particular importance given the multitude of abdominal disorders in which vomiting is seen (Tables 2 and 3). In cats, gastrointestinal mass lesions [4b ¹⁴² , 4c ¹²⁶ ], pancreatic masses [4c^128,150, 4d^82,151,152] and hepatomegaly [4a ⁵¹ , 4c ⁶¹ ] can be identified readily, and can help to narrow the list of possible differential diagnoses and refine the diagnostic approach. Further, gastrointestinal obstructive disorders commonly have abnormalities identified on physical examination [4b^38,120, 4c ¹²¹ ]. However, while abdominal pain has been reported in cases of pancreatitis [2b ¹⁵³ ], it is suggested to be less consistent than in dogs with pancreatitis [2b ¹⁵³ , 5^154,59] and is seen with other disorders, including cholecystitis or cholangitis [4c ⁵⁷ ], septic peritonitis, [4b ¹⁵⁵ ] and gastroduodenal ulceration [4c ¹⁵⁶ ]. When icterus is seen in vomiting cats, it tends to be due to hepatic and post-hepatic diseases (rather than prehepatic causes), including extrahepatic biliary obstruction [4b^53,54,59, 4d^65,157], cholecystitis or cholangitis/cholangiohepatitis [4c ⁵⁷ , 4d ⁵⁸ ], hepatic lipidosis [4a ⁵¹ , 4d^69,158], cholelithiasis [4c ¹⁵⁹ ], and hepatobiliary neoplasia [4c ⁶¹ ]. Finally, careful palpation of the cervical area should be performed in all older cats with chronic vomiting, given that a palpable goitre is usually noted when hyperthyroidism is present [4a ⁸⁰ ].

Table 6.

Important considerations in the physical examination of the vomiting cat

Physical examination of the vomiting cat should include assessment of:	Rationale [level of evidence/reference]	Overall evidence grade
Abdominal palpation	Intestinal thickening and mesenteric lymph node enlargement may be caused by lymphoma [4c 128 , 4d 151 ] Palpable abdominal mass may be found with intussusception [4b 120 , 4c 121 ], gastrointestinal adenocarcinoma [4b142, 4c126], pancreatic cysts [4d 152 ], encapsulated peritonitis (eg, isolated abdominal fat necrosis) [4d161,308] Gastrointestinal obstruction is usually recognised by abdominal palpation [4b 38 , 5 359 ] Cranial abdominal pain can be seen in cholecystitis or cholangitis [4c 57 ], acute pancreatitis [2b 153 ], septic peritonitis [4b 155 ], uterine adenomyosis [4d 133 ] and gastroduodenal ulceration [4c] 156 Large, painful bladder in urethral obstruction [4d134,148,149] Hepatomegaly could indicate hepatic lipidosis [4d 139 ] or hepatobiliary tumour [4c 61 ] Other palpable abnormalities include enlarged mesenteric lymph nodes [4d 305 ], splenic haemangiosarcoma [4c 91 ], perirenal (pseudo-) cyst [4d 82 ], pancreatic tumours [4c 150 ] and intra-abdominal actinomycetoma [4d 306 ]	C
Rectal temperature	Pyrexia can be seen with panleukopenia virus [5 122 ], cholecystitis or cholangitis/cholangiohepatitis [4c57, 4d58], acute pancreatitis [2b 153 ], chronic hepatitis [4d 56 ], prostatic abscess [4d 110 ] and Mycobacterium species infection [4d 305 ]	C
Oral examination, inspection of anus	Ingestion of thread and sewing needle can be diagnosed with abdominal palpation and oral examination [4a 37 ] Linear foreign body is visible at mouth or anus in one-third of cases [4b 38 ]	C
Abdominal distension/effusion	Seen in uroperitoneum [4b 160 ], septic peritonitis [4d 92 ], sclerosing encapsulating peritonitis [4d 161 ], chronic hepatitis and cirrhosis [4d 56 ] and uterine enlargement [4a 309 , 4d 225,312 ]	C
Dehydration, pale mucous membranes, hypothermia, tachycardia	Can be with intussusception [4b 120 ] and haemoperitoneum [4c 91 ] Fluid therapy should be given to a dehydrated cat [5]	C
Dyspnoea	Diaphragmatic hernia and accompanying gastric dilatation-volvulus causes severe dyspnoea and needs to be treated without delay [4c 265 ] Can be seen with haemoperitoneum [4c 91 ]	C
Icterus	Can be seen in extrahepatic biliary obstruction [4b53,54,59, 4d65,157], cholecystitis or cholangitis/cholangiohepatitis [4c 57 , 4d 58 ], hepatic lipidosis [4a 51 , 4d58,69], cholelithiasis [4c 159 ], hepatobiliary tumour [4c 61 ], biliary mucocoele and pancreatic tumour [4c 150 ]	C
Size of the bladder	May see distended urinary bladder in urethral obstruction [4d 134 ]	D
Lymph node enlargement	Can occur in Mycobacterium species infection [4d 305 ] and lymphoma	D
Palpation of cervical area	Palpable goitre can be noted with hyperthyroidism [4a 80 ] or hyperparathyroidism [4c 149 ]	C
Skin fragility	Reported in cholangiohepatitis and hepatic lipidosis [4d 158 ]	D
Nasal discharge	Vomiting is commonly associated with nasal disease [4a 111 ]	C
Vaginal discharge	Pyometra can cause vomiting [4c 314 ]	C
Neurological examination	Central nervous system disease can cause vomiting [5]	D

From the signalment, history and physical examination, the clinician should be able to categorise the patient as systemically ‘well’ (stable patient with no criteria for further assessment or treatment; Table 7) or ‘unwell’ (unstable patient with one or more criteria for intervention), establish a problem list, and identify appropriate diagnostic investigations and therapy [OEG D].

Table 7.

Criteria suggesting the need for further intervention in vomiting cats

A number of findings might indicate need for further investigation	Rationale [level of evidence/reference]	Overall evidence grade
Nature of the vomiting
Frequent acute vomiting, vomiting large volumes, vomiting contents of a fetid nature	May be a sign that inpatient care is needed [5] Needs investigation in case surgical intervention is required (eg, intestinal obstruction) [5]	D
Haematemesis	Can be seen in cats with gastric adenocarcinoma [4c 145 ], intestinal polyps [4c 131 ] and gastric ulceration [4c 156 ]	C
Other gastrointestinal signs
Melaena	Can be seen in cats with gastric adenocarcinoma [4c 145 ] Can be seen in cats with Physaloptera preputialis nematodes [4c 146 ]	C
Abdominal pain	Can be seen with gastrointestinal ulceration [4c 156 ] or peritonitis [4d 161 ], although other causes are possible [5]. However, it is less commonly seen in cats with pancreatitis than dogs with pancreatitis [2b 153 , 5 154 ]	C
Abdominal swelling or free fluid	Can be a sign of peritonitis [4b 163 ], haemoperitoneum [4a 162 ], hypoalbuminaemia, FIP, hepatic disease and other diseases requiring further investigation [5]	C
Weight loss/failure to thrive	Suggests chronic disease process requiring further investigation [5] Severe recent weight loss associated with hepatic lipidosis [4a 51 ] Can be associated with malignancies [4b142,164, 4c 128 , 4d 151 ]	C
Other clinical signs
Pyrexia	Can be seen in cats with panleukopenia virus [5 122 ], cholangitis/cholangiohepatitis [4c 57 ], acute pancreatitis [2b 153 ] and other diseases requiring further investigation [5]	C
Severe dehydration/hypovolaemia/ hypothermia/shock	Fluid therapy indicated [5]	D
PU/PD	Seen in renal disease [4b 75 ], diabetes mellitus [4a 147 ], hyperthyroidism [4a 80 ], hypoadrenocorticism [4c 328 ] and other diseases [5]. However, unlike dogs, hypercalcaemic cats infrequently present with PU/PD [4a 363 , 4b 364 , 4c 365 ]	C
Bradycardia (absolute or relative to volume status)	Can be seen in hypoadrenocorticism [4c 328 ] and electrolyte abnormalities [2b 71 ]	C
Marked malaise	Rarely seen in mild, self-limiting diseases [5]	D
Other abnormal physical examination findings, eg, pale mucous membranes, jaundice, neurological signs, dysrhythmias, palpably enlarged thyroid	May indicate a specific disease requiring investigation and intervention	D
Timeframe and response to therapy
Chronicity (>2 weeks duration)	Suggests the disease process is not self-limiting and that further investigation is needed [5]	D
Failure of symptomatic treatment	Needs further investigation [5]	D

PU/PD = polyuria/polydipsia; FIP = feline infectious peritonitis

Diagnostic approach

Cats with simple, mild, acute self-limiting emesis do not need further investigation, and can be treated symptomatically (see below) or simply monitored [OEG D]. In such cases, signs resolve after 1–2 days, with or without symptomatic and supportive therapy. However, this syndrome of acute and self-limiting emesis, a common reason for dogs presenting to veterinary surgeons, is probably less common in cats, and cats that are presented are relatively more likely than dogs to require treatment and investigation [OEG D]. Suggested criteria, whereby further assessment and management should strongly be considered when identified in a cat that is vomiting, are shown in Table 7 [OEG D]. These include: frequent acute vomiting [4a ³⁷ , 4c ¹⁴⁰ ], the presence of blood in the vomitus or melaenic faeces [4c^{131,145,146,156}], abdominal pain [2b ¹⁵³ , 4b ¹⁶⁰ , 4c ¹⁵⁶ , 4d ^92,161 ], abdominal distension [4a^120,162, 4b ¹⁶³ ] and pyrexia [2b ¹⁵³ , 4c ⁵⁷ , 5 ¹²² ]. Other criteria that suggest the need for further intervention include severe dehydration, signs of shock, a history of vomiting for more than 2 weeks or persistent vomiting despite symptomatic treatment [5]. All of these latter criteria have been suggested by expert opinion; although we would agree that these criteria are sensible, no objective information in support of their use could be identified.

Where signs of dehydration, shock or hypothermia are present, intravenous fluid resuscitation should be a priority and further examinations should also be considered, including haematological examination, a biochemistry profile and urinalysis [5]. If no abnormalities are discovered by abdominal palpation, it is appropriate to await the results of haematological examination, biochemistry profile and urinalysis [5]. In cats >6 years old, total T₄ measurement should be considered in addition to routine clinicopathological assessments, given the possibility of hyperthyroidism [4a^79,80] [OEG D].

Thoracic radiographs are indicated if the cat is dyspnoeic, tachypnoeic, has abnormalities on auscultation or if there is a suspicion of oesophageal disease based on the presenting history [4b ¹³⁵ , 4c ¹³⁶ , 4d^137–139]. Diagnostic imaging of the abdomen should be considered in any vomiting cat, especially if abnormalities are found on abdominal palpation (eg, abdominal pain, mass, thickened intestines) [4a ⁵¹ , 4b ¹⁴² , 4c^{61,126,128,150}, 4d^82,151,152]: ultrasonography is the most appropriate imaging modality in many cases, but the information obtained is often complemented by the findings of radiography. Contrast radiography, endoscopy, exploratory coeliotomy or laparoscopy may also be considered (Table 8). If the cat is icteric, hepatic ultrasonography (with liver fine needle aspiration cytology, biopsy and/or cholecystocentesis) is indicated [OEG D].

Table 8.

Diagnostic tests used in the investigation of cats with vomiting

Diagnostic test	Information obtained	Overall evidence grade
Tests commonly used in current clinical practice
Elimination diet
	Use in the diagnosis of adverse reactions to food [4c30,31]	C
Haematology
	Anaemia can be seen with IBD [4b 366 ], nematode infection [4c 146 ], intestinal polyps [4c 131 ], acute pancreatitis [2b 153 ] and primary hyperparathyroidism [4c 149 ] Leukocytosis can be seen with IBD [4b 366 ], Mycobacterium species [4d 305 ], lymphoma [4c 165 ] and pancreatic tumour [4c 150 ] Leukopenia can be seen with IBD [4b 366 ] and FPLV [5 122 ] Large granular lymphocytes can be seen with intestinal lymphoma [4c 165 ] Eosinophilia can be seen with intestinal lymphoma [4d 151 ], food allergy [4c 31 ], hypereosinophilic syndrome [4c 87 ] and nematode infection [4c 146 ] Dehydration and haemoconcentration are possible consequences of vomiting [5] Erythrocytosis-induced hyperviscosity causes vomiting [4c 339 ]	C
Clinical biochemistry
Urea and creatinine	Azotaemia seen in renal disease [4b 75 ], urinary tract obstruction, dehydration, hypercalcaemia and uroperitoneum	C
Total protein, albumin	Hyperproteinaemia seen in IBD [4b 366 ] and many other conditions Hypoproteinaemia seen in IBD [4b 366 , 4c 48 ], lymphoma [4c 267 ], Mycobacterium species infection [4d 305 ], septic peritonitis [4b 155 ] and many other conditions	C
Hepatic enzymes and bilirubin	Can be increased in cats with IBD [4c 48 ], lymphoma [4c 165 ], hepatic lipidosis [4a 51 , 4d 69 ], extrahepatic biliary obstruction [2b 50 , 4b 54 , 4c53,59,223, 4d63,65], cholangitis [4d 158 ], hepatobiliary masses [4c 55 ], pancreatic tumour [4c 150 ] and hyperthyroidism (liver enzymes not bilirubin) [4a 367 ]	C
Blood glucose	Diagnosis of diabetes mellitus [4a 147 ]	C
Cholesterol	Hypocholesterolaemia can be seen in IBD [4b 366 ]	C
Sodium, potassium and chloride	Electrolyte changes are a common consequence of vomiting [5] Hyperkalaemia seen in urethral obstruction [2b 71 ] Hyperkalaemia and hyponatraemia are occasionally seen in hypoadrenocorticism [4c 327 ], but also with other conditions, including gastrointestinal disease, renal disease, cardiorespiratory disease and body cavity effusions [4b 368 ]	C
Calcium and phosphate	Diagnosis of hypercalcaemia [4a 308 , 4c 235 , 4d149,228,238]	C
Urinalysis
	Can assist in the diagnosis of kidney disease and lower urinary tract disease [5]
		D
Faecal analyses
	Flotation for Isospora species, Giardia species cysts, Cryptosporidium species oocysts, coccidial oocysts and Cyniclomyces guttulatus [4a123,124,281, 4d 279 ] Bacterial culture for Salmonella species [4a 277 ] SNAP test for Giardia species [4a123,369]	C
Specific gastrointestinal tests
Cobalamin	Cobalamin deficiency occurs with diseases in the intestines, pancreas or hepatobiliary system [4b 370 , 4c 302 ] Identify need for supplementation which can ameliorate signs of severe hypocobalaminaemia [4b 370 , 4c 371 ]	C
Lipase fTLI fPLI	Increased in experimental pancreatitis [2b 153 ], but can be unhelpful in clinical cases [5169,372] Increased in pancreatitis [4d 69 , 5154,169], but false-positives and false-negatives occur [3b372,373] Decreased in EPI [4d 301 , 5 154 ] Increased in pancreatitis [3b 374 ], but can get mild increases in some cats without pancreatitis signs [3b 375 ]	C C B
Diagnostic imaging
Thoracic radiography	For diagnosis of diaphragmatic hernia [4c 262 , 4d 263 ] Megaoesophagus, gastro-oesophageal intussusception [4d 137,138 ] Lymphadenopathy in Mycobacterium species infection [4d 305 ] Metastases, eg, in pancreatic tumours [4c 150 ] Bronchogenic adenocarcinoma [4d 238 ]	C
Abdominal radiography	Usually normal in cats with IBD [4b 366 ] Diagnosis of obstruction or linear foreign body [4a 37 , 4b38,120, 4c 126 ], intestinal neoplasia (including colonic adenocarcinoma) [4b 142 , 4c 256 ], mesenteric lymphadenopathy [4d 305 ], pancreatic masses caused by neoplasia, cysts or pseudocysts [4c 150 , 4d152,299], uterine enlargement [4d 133 ], ureteral calculi [4a 309 ], calcium oxalate urolithiasis [4d 149 ], splenic tumour and haemoperitoneum [4c 91 ]	C
Abdominal ultrasonography	Ultrasonographic findings may correlate with histological grade of IBD in cats [4b 366 ] Intussusception can be diagnosed with ultrasonography [4b 120 ] Luminal narrowing or a colonic mass can be seen in cats with colonic adenocarcinoma [4c 256 ] Can identify gastric wall thickening [4d232,268], ileocaecocolic abnormalities [4b 376 ], linear foreign bodies [4b 38 ], extrahepatic biliary obstruction [4b53,54, 4c 223 , 4d63,65,157], small bowel infarction and local peritonitis [4d 289 ], pancreatitis [5 154 ], pancreatic cysts [4d 152 ], pancreatic tumours [4c 150 ], liver disease [4d58,69], uterine abnormalities [4a309,313, 4d132,133], ureteral calculi [4a 309,313 ], diaphragmatic hernia [4c 262 ], prostatic abscess [4d 110 ], splenic masses [4c 91 ], hepatobiliary tumours [4c 61 ], renal and perirenal cysts, and pseudocysts [4c 229 , 4d 82 ]	C
Ultrasound-guided FNA Cytology	Alimentary lymphoma [4b 164 ] Prostatic abscess [4d 110 ] Useful to investigate abnormalities in many organs [5]	C
Biopsy collection and examination
Endoscopy	Severity and type of inflammation in IBD [4b 366 ] Hyperaemia, haemorrhage, and roughened or cobblestone mucosa in LPE [4c 48 ] Identification of oesophageal, gastric and duodenal abnormalities [4c 131 , 4d 232 , 5 377 ]	C
Exploratory coeliotomy	Diagnosis of abdominal disorders such as intestinal obstruction (including Taenia taeniaeformis) [4d 224 ], pancreatitis [4d 294 ], chronic hepatitis and cirrhosis [4d 56 ], septic peritonitis [4b 155 ], prostatic carcinoma [4d 134 ], multiple cystic intestinal duplications [4d 119 ] and many other abnormalities	C
Liver biopsy	Liver disease [4a 51 ]	C
Histopathology	Diagnosis of IBD and neoplasia (including lymphoma) [4b47,164, 4c 128 , 4d141,143] Identify Ollulanus tricuspis [4c271,360] Diagnosis of pancreatitis, chronic hepatitis and cirrhosis [4c 298 , 4d 56 ]	C
Tests used occasionally
Examination of the vomitus	Can reveal O tricuspis or Physaloptera preputialis nematodes [4c146,271,360]	C
Blood pressure	Hypertension can be associated with renal disease or hyperthyroidism [4c 229 ]	C
Electrocardiography	Dysrhythmias or bradycardia in cardiac disease or metabolic disturbances (eg, hyperkalaemia) [4c 335 ]	C
Coagulation tests	Required prior to liver biopsy [5]. Can be abnormal in cats with hepatic lipidosis [4a 51 ]	C
ACTH stimulation test	Hypoadrenocorticism can cause vomiting [4c 328 ]	C
Blood gas analysis	Guides fluid therapy [5]	D
Lactate	Increased in septic peritonitis [4b 155 ]	C
Heartworm (Dirofilaria immitis) testing: antigen, antibody	In endemic areas. Vomiting is a frequent sign in D immitis infection in cats [4a 315 , 4b 316 , 5 230 ]	C
Cholecystocentesis	Bacterial culture of bile to diagnose cholecystitis or cholangitis [4c 57 , 4d 58 ] Identification of liver fluke (Platynosomum concinnum) [4c 223 ]	C
Cytology/bacterial culture of peritoneal effusion	Peritonitis (including septic peritonitis) [4b155,163, 4c 164 , 4d92,161,305] and haemoperitoneum [4a 162 , 4c 91 ]	C
Creatinine and potassium (in peritoneal effusion)	Indicator of uroperitoneum suggesting leakage from urinary tract [4c 160 ]	C
Laparoscopy	Can be used to evaluate the pancreas [4c 378 ]	C
Tests not commonly used or limited in their availability
Gastrin	Increased in several diseases; suggestive of gastrinoma [4d 292 ]	D
Contrast radiography	Identify gastrointestinal lesions, including IBD [4c 365 ], gastric neoplasia [5 377 ], megaoesophagus [4d 263 ] and duodenal polyps [4c 131 ] Positive contrast radiography to check for rupture of urinary bladder or urethra [4b 160 ] Excretory urography for ureter dissection [4d 308 ]	C
CT scan	Evaluate abdominal organs; not yet proven to be useful in the diagnosis of feline pancreatitis [3b 374 ]	D
CT scan and labelled leukocytes	Can be used in diagnosis of pancreatitis [4d 299 ]	D
MRI	Evaluation of CNS disease [5]	D
Endoscopic aspiration of intestinal contents	To identify Giardia species trophozoites (if zinc flotation of faeces is negative and the cat is not on treatment) [4a 379 ]	C
Immunohistochemistry	Coronavirus enteritis [4c 125 ] Immunological markers aid in characterisation of IBD in the research setting [4b 45 ] Classify alimentary lymphoma and distinguish lymphoma from intestinal inflammation [4b 46 ,4d 151 ]	C
PCR or Warthin-Starry staining on gastric mucosa	Infection with Helicobacter species [4b 118 ]	C
FISH in tissue biopsies	Gastric Helicobacter heilmannii infections are associated with gastric MALT lymphoma [4b 285 ] Can be used to identify Helicobacter species in cats with gastritis [4c 117 ]	C
PCR on tissue biopsies	Can reveal Anaerobiospirillum species in cats with ileocolitis [4c 278 ]	C

fTLI = feline trypsin-like immunoreactivity; fPLI = feline pancreatic lipase immunoreactivty; FNA = fine needle aspirate; ACTH = adrenocorticotropic hormone; CT = computed tomography; MRI = magnetic resonance imaging; PCR = polymerase chain reaction; FISH = fluorescent in situ hybridisation; IBD = inflammatory bowel disease; FPLV = feline panleukopenia virus; SNAP = SNAP Giardia test; EPI = exocrine pancreatic insufficiency; LPE = lymphoplasmacytic enteritis; CNS = central nervous system; MALT = mucosa-associated lymphoid tissue

There are numerous causes of gastrointestinal obstruction in small animals, but several are more commonly seen in cats, namely linear foreign bodies [4a ³⁷ , 4b ³⁸ ], trichobezoars [4c ³⁶ ], focal intestinal neoplasia [4b^142,164, 4c^128,131,165, 4d^144,151,157] and megacolon [5 ¹⁶⁶ ] [OEG D]. When diagnostic imaging findings suggest obstruction, exploratory coeliotomy should be performed [OEG D].

In those cases where further investigation is considered necessary or abnormalities are identified on initial diagnostic tests, a variety of other diagnostic tests may be indicated (Table 8). Additional tests to be considered include other blood tests (eg, trypsin-like immunoreactivity, pancreatic lipase, folate and cobalamin, lactate, coagulation tests), serology (eg, testing for feline leukaemia virus, feline immunodeficiency virus and coronavirus), faecal examinations [for flotation, culture, cytology and/or polymerase chain reaction (PCR)], examination of the vomitus, examination of peritoneal or thoracic effusion, fine needle aspiration cytology of any abnormal organs or masses found, testing for heartworm infection (in endemic areas), advanced imaging and an elimination diet trial. Furthermore, either endoscopy or exploratory coeliotomy can be used to examine the alimentary tract directly and to collect biopsies. Biopsies can then be used for histopathology, immunohistochemistry (to identify cell lineages and Coronavirus), fluorescence in situ hybridisation (to identify invasive bacteria), bacterial culture or PCR, if indicated by specific findings in the history or physical examination, and depending on availability [OEG D]. When endoscopy is performed, either the upper alimentary tract (eg, oesophagus, stomach and duodenum) the lower gastrointestinal tract (eg, rectum, colon, caecum and ileum) or both can be examined. Recent evidence suggests that, for some causes of vomiting (eg, IBD), both regions should be examined because the results of histopathological examination may not correlate [4a ¹⁶⁷ ]. Exploratory coeliotomy may be more suitable in some cases of vomiting because of the frequency with which lesions outside the gastrointestinal tract are noted in cats with gastrointestinal signs [4b^168] [OEG C]. These recommendations are made based on the available evidence but, as shown in Table 8, this evidence is frequently only of level 4 or 5. For example, it has long been accepted that assays for total amylase and total lipase are not useful in the investigation of pancreatitis in cats. While this may be true, the only objective evidence currently available for this supposition is a meeting abstract [5 ¹⁶⁹ ].

Treatment

Vomiting is unpleasant for cats and distressing to owners, and can be associated with adverse consequences, including anorexia, weight loss, food aversion and disturbances of fluid, acid–base and electrolyte balance. It may also cause aspiration pneumonia in severely sick cats [OEG D]. Although most cases of acute vomiting are likely to resolve without specific treatment, no objective data are available to determine the likelihood of this happening. When vomiting does not resolve spontaneously, a diagnosis should be sought to allow specific treatment of the underlying cause. Pending results of investigations, supportive care for the vomiting cat can include fluid and electrolyte therapy, and antiemetics (see below). However, antiemetics may be contraindicated where there is gastrointestinal obstruction [OEG D].

Antiemetic therapy

To date, there are no published clinical trials of antiemetics in naturally occurring cases of emesis in cats. Therefore, information on antiemetic efficacy must be drawn from experimental studies. In interpreting the results of these studies, consideration should be given to the emetic stimulus used in the study and, therefore, the likely emetic pathways involved. Certain important differences exist between dogs, cats and ferrets — the three species most commonly used in experimental emesis research and, therefore, extrapolating the results of experiments in different species to cats must be undertaken with caution. For example, D₂ dopamine receptors in the AP are much less important in cats than in dogs, explaining the comparative resistance to apomorphine-induced vomiting cats [2b^17,170]. In contrast, α₂ adrenergic receptors are important in the areas of the cat brainstem controlling vomiting, explaining why the α₂ agonist xylazine is an effective emetic agent in cats [2b^171–173]. A schematic diagram showing the various receptors implicated in emesis in cats is shown in Figure 1 [OEG B].

Figure 1.

Schematic diagram showing receptor types potentially involved in emetic pathways in the cat [OEG B]. 5HT = serotonin (5-hydroxytryptamine); α² receptor = alpha-2 adrenergic receptor; ACh = acetyl choline; CRTZ = chemoreceptor trigger zone; H1 receptor = histamine type 1 receptor; NK₁ = neurokinin 1

The antiemetics available in veterinary practice, and evidence of efficacy, are shown in Table 9. As mentioned above, published evidence in support of their use in this species is limited. The most effective antiemetics for cats appear to be those that work via NK₁ (eg, maropitant) or serotonin (5-hydroxytryptamine, 5HT₃) (eg, ondansetron) receptors [OEG B]. Drugs with α₂ antagonist activity are anecdotally reported to be effective antiemetics in cats, but robust evidence to support their use is lacking [OEG D].

Table 9.

Antiemetic drugs in cats

Drug	Dose	Receptor pharmacology	Pathways inhibited	Other actions	Adverse effects and contraindications	Level of evidence and reference(s)	Overall evidence grade (antiemetic action)
Phenothiazines
Chlorpromazine	0.3–0.5 mg/kg IM q8h	α2 antagonist D2 antagonist H1 antagonist 5HT3 antagonist Muscarinic ACh antagonist	Central emetogens? Motion sickness?	α1 antagonist	Prelicensing safety studies not performed Decrease blood pressure, especially if dehydrated Sedative effects Behavioural effects May potentiate movement disorders associated with metoclopramide	3b 174	– (Not effective against centrally acting emetogens in this study)
Prochlorperazine	0.1−0.5 mg/kg SC, IM, IV q6–8h or 0.5–1.0 mg/kg PO q8–12h					No published data to support its use as an antiemetic in the cat	–
Metoclopramide	0.2–0.5 mg/kg IM, SC, PO q6–8h or 1–2 mg/kg IV over 24 h as CRI	D2 antagonist 5HT3 antagonist at higher dose	D2 receptors not thought to be important in central vomiting pathways in cats	Variable prokinetic effect may contribute to antiemetic effect	Prelicensing safety studies not performed Movement disorders/frenzied behaviour Reduce dose by 50% in renal failure Contraindicated in intestinal obstruction May reduce the frequency of emetic events after xylazine administration	3b40,175	C
Selective 5HT3 antagonists
Ondansetron	0.5 mg/kg IV loading dose followed by 0.5 mg/kg IV infusion for 6 h or 0.5–1.0 mg/kg PO q12–24h	5HT3 antagonist	Work well vs cisplatin-induced emesis, especially the acute phase (relatively ineffective against the delayed phase)		Prelicensing safety studies not performed. Contraindicated in intestinal obstruction Considered safe — headaches and CNS signs reported in humans QT segment alterations reported in humans after dolasetron use	2b 181	– (Reduced the severity of dexmedetomidine-induced nausea and vomiting in healthy cats, but only if given with the dexmedetomidine)
Granisetron	1 mg/kg IM q8h					2b 178	B
Dolasetron	0.6–1.0 mg/kg IV or PO q24h					5 179	D
Maropitant	1 mg/kg SC or PO q24h	NK1 antagonist	Broad spectrum antiemetic Effective vs peripheral and central emetogens and prevents vomiting induced by motion sickness		Pain on injection (may be reduced by refrigerating the solution) Highly protein-bound; use with caution in hypoproteinaemia or when giving with other highly protein-bound drugs	2b 184	B

5HT₃ = serotonin (5-hydroxytryptamine); CRI = constant rate infusion; ACh = acetylcholine; NK₁ = neurokinin 1; CNS = central nervous system

Chlorpromazine was not effective against emetogens working via the AP in cats [3b ¹⁷⁴ ], and there are no published reports on the use of prochlorperazine as an antiemetic in cats.

Although often listed as a first line antiemetic, metoclopramide, a D₂ antagonist, is of questionable use as a central antiemetic in cats, and it failed to block the emetic response to dopamine administration in cats [2b ¹⁷³ ]. Administration of metoclopramide to cats prior to xylazine injection reduced the frequency of emetic events in one study, but not in another [3b^40,175]. The possibility that tolerance to xylazine caused the reduction in emetic events was not adequately excluded in that study. ⁴⁰ Metoclopramide may be used in some circumstances where a gastrointestinal prokinetic action is desired, for example for ileus or delayed gastric emptying, but its prokinetic action is weak in the cat [2b^176,177] [OEG B].

The 5HT₃ receptor antagonist granisetron was effective against the acute phase of cisplatin-induced emesis (peripheral emetogen) in cats [2b ¹⁷⁸ ], and there are anecdotal reports that the related drug dolasetron is also effective in this species [5 ¹⁷⁹ ]. In laboratory studies 5HT₃ receptor antagonists prevented cisplatin-induced vomiting, but not vomiting induced by xylazine or motion [2b ¹⁸⁰ ]. Ondansetron reduced the severity of dexmedetomidine-induced nausea and vomiting in healthy cats, but only if given at the time of dexmedetomidine administration [2b ¹⁸¹ ]. These drugs appear to act via peripheral 5HT₃ receptors, although action at central sites may contribute to their efficacy [2b^{178,180,182,183}] [OEG B].

Maropitant is a potent, highly selective NK₁ receptor antagonist, which is well tolerated and safe in cats [2b184]. In a preliminary study, at the dose used in dogs (1 mg/kg SC), maropitant was effective in preventing xylazine-induced emesis (central emetogen) and motion sickness-induced vomiting in cats [4d ¹⁸⁴ ]. It was effective when given subcutaneously or orally, and had a half-life in the cat suitable for once-daily dosing. However, use in larger numbers of cats is needed before strong recommendations can be made for its efficacy and to identify any uncommon adverse effects [OEG B].

For the treatment or prevention of motion sickness in cats, NK₁ receptor antagonists are effective in the laboratory setting.^184,185 Antihistamines are thought to be effective against motion sickness in some species. However, in cats, although an irreversible inhibitor of histamine synthesis prevented motion sickness, an H₁ antagonist did not [OEG B] [2b ¹⁸⁶ ].

5HT_1A receptor agonists were shown to be effective against a range of emetic stimuli in the cat, but have not found their way into the clinic [2b^187–190]. In particular, many cats showed marked defensive behaviour with these drugs, limiting their use [OEG B].

A variety of other drugs have been assessed for antiemetic effects in cats, but are not likely to be useful antiemetics in a clinical setting [OEG B] [2b^191–200].

Dietary management

Many vomiting cats are systemically well and have self-limiting conditions, for example acute gastroenteritis. Dietary recommendations for this group are commonplace in review articles, but have little scientific basis [5^201,202]. Nonetheless, the self-limiting nature of clinical signs in these cases, and absence of evidence to the contrary, mean that these practices will likely continue for the current time.

The standard dietary recommendation for cats with acute gastrointestinal disorders is to withhold food for 24–48 h, followed by administration of small quantities of a bland, highly digestible diet three or four times per day for 3–7 days [5^203,204]. Such short-term fasting is said to provide ‘bowel rest’, thereby reducing gastrointestinal secretions and bacterial numbers, while avoiding the adverse effects of non-absorbed, osmotically-active food particles [5^203,204]. Arguably, the bowel can also be ‘rested’ if a highly digestible diet is fed, as this is assimilated rapidly in the proximal small bowel [5 ²⁰¹ ] [OEG D].

In contrast, in human gastroenterology there is strong evidence in favour of feeding during gastroenteritis [2b ²⁰⁵ ]. Unfortunately, there are no equivalent published studies in cats. Some authors have argued that continuing to feed may exacerbate vomiting. Further, if present, diarrhoea may be exacerbated by the osmotic action of luminal food particles. For these reasons, food withholding is likely to remain as the most widely adopted strategy. That said, care must be taken in sick cats, especially if they are obese, given concerns over invoking hepatic lipidosis, a consequence of starvation in an obligate carnivore [2b^206–208] [OEG C].

The term ‘bland diet’ is used commonly but defined rarely. Arguably, most canned foods are ‘bland’ because of their easy assimilation, while dry foods may be less suitable [5 ²⁰¹ ]. Many clinicians advocate switching to a diet containing a novel protein source, given concerns in humans that food allergies can develop to proteins eaten during a bout of acute gastroenteritis and delay recovery [2b ²⁰⁹ ]. However, no similar evidence is available in cats. Although a reaction to the novel ingredient could occur, adverse reactions to foodstuffs not typically part of the normal diet (eg, poultry meat) may be easier to manage than for a constituent of a commercially available pet food [OEG D].

Gastric emptying is slower for foods with greater fat content, so fat restriction is commonly advocated. That said, the response in cats with chronic gastrointestinal signs is similar when using diets of differing fat content [2b ²¹⁰ ]. Diets with greater liquid content also empty faster: fully-liquid diets are quickest, followed by canned food, and dry kibbled diets are slowest [5 ²⁰² ]. Finally, fibre content may also influence emptying [5 ²⁰² ]. The feline stomach is less distensible than that of other species as their alimentary tracts are adapted to small, frequent meals [5 ²⁰² ]. As a result, large-volume meals may provoke further vomiting. Taken together, this would suggest that a moderately energy dense, low fibre, wet (or liquid) diet should be used in small meals frequently [5 ²⁰² ]. However, there has been no critical appraisal of this advice [OEG D].

Adverse reactions to food are reportedly a common cause of chronic gastrointestinal signs, including vomiting [2b^28,30], with at least 50% of such cases responding when a diet based on novel ingredients is fed [2b ²⁸ ]. Some have suggested favourable responses when using hydrolysed protein diets [4c ²⁹ ], but no controlled studies exist. Nonetheless, favourable results were reported in a recent controlled trial assessing efficacy of hydrolysed protein diets for management of canine chronic enteropathy [2b ²¹¹ ] [OEG B].

In contrast to stable acute vomiting cases with self-limiting disease, nutritional requirements for hospitalised cats are different, and withholding food is not usually recommended. In humans, enteral feeding methods are superior to parenteral nutrition in critically ill patients [1b ²¹² ]. Such an approach improves survival, decreases infection rate, decreases bacterial translocation, has fewer complications and enables earlier discharge from hospital. There may be similar benefits in dogs, with experimental studies suggesting advantages of enteral nutrition over parenteral nutrition in a model of acute pancreatitis [2b^213,214]. These findings are supported by two randomised controlled clinical studies comparing the efficacy of enteral nutrition in severe cases of gastroenteritis [2b^215,216]. By extrapolation such strategies may be preferable in sick vomiting cats and may also reduce the likelihood of hepatic lipidosis [2b^206–208] [OEG B].

A number of studies have provided information on the methods, applications and benefits of enteral nutrition [4a ²¹⁷ , 4b ²¹⁸ ]. Further, complications are well established, with vomiting being a prominent side effect [4a^218,219]. There are also two experimental studies in cats assessing the benefits of enteral nutrition in cats given methotrexate chemotherapy [2b^221,222]. These studies concluded that feeding a complex diet, containing intact protein as the nitrogen source, was preferable to the use of ‘elemental’ diets containing free amino acids as the only nitrogen source. While these findings may be most relevant to cats receiving chemotherapy, the conclusions may be pertinent to cats with other gastrointestinal disorders [OEG C].

In conclusion, limited information is available on appropriate nutritional management of vomiting cats. For those requiring hospitalisation, published studies in other species support the use of early enteral feeding. Enteral nutrition would also be favoured in cats with severe acute pancreatitis, although the only veterinary data would suggest that jejunostomy tube feeding is suitable. There is no direct evidence to support or refute the use of early enteral feeding in acutely vomiting cats that are managed as outpatients.

Monitoring

There are no published studies specifically addressing the most appropriate methods for monitoring vomiting cats. Most case series and reviews mentioning monitoring recommend using techniques appropriate to the underlying disease, including frequent clinical assessment during hospitalisation (especially postoperatively) [4b^53,163, 4c ²²³ , 4d^224,225], laboratory investigations [4a^226,227], [4a^226,227, 4b ¹⁵⁵ , 4d_64,228], indirect blood pressure measurement [4b ²²⁹ ], and diagnostic imaging [5^230,231] [OEG C].

The optimal timeframe for reassessment has also not been addressed specifically; when symptomatic treatment is administered to a vomiting cat suspected to have self-limiting disease, an initial maximum of 24 h antiemetic treatment is the usual recommendation. If vomiting continues beyond this time, if other signs have not improved, or if new signs are evident (eg, deterioration in appetite or general demeanour, or appearance of diarrhoea), we recommend that reassessment should occur no more than 48 h after the first visit. Owners should be warned that the use of an antiemetic drug can mask signs of vomiting associated with an underlying disease and should be asked to return sooner if there is no improvement or there is any clinical deterioration. At revisit, the cat should be reassessed for criteria that may necessitate further assessment or management (Table 7), and further treatment and investigations should be performed as appropriate (see above) [OEG D].

Vomiting in cats with cancer

Cats with benign or malignant tumours may vomit because of the presence of the tumour (eg, in the alimentary tract [4b^{46,127,142,164}, 4c^{126,128,131,145,165}, 4d^{86,143,157,232–234}]; in the hepatobiliary system [4b^53,55, 4c ⁶¹ ]; affecting the pancreas [4c ¹⁵⁰ ], or present systemically [4c ⁸⁷ , 4d^84–86]) or because of paraneoplastic effects [4c ²³⁵ , 4d^{149,228,236–238}] [OEG B].

Cancer chemotherapy also is associated with vomiting and nausea in cats, and can lead to adverse consequences, including anorexia [2b ²³⁹ , 4b ²⁴⁰ ]. Data from other species suggest that some anticancer drugs are more likely to cause vomiting than others [3a^2,241], but similar data are not available for the cat. Anticancer drugs that have been associated with vomiting in tumour-bearing cats include cyclophosphamide [2b ²⁴² ] ifosfamide (vomiting was mild and self-limiting) [2b^243,244], doxorubicin [2b^245,246], methotrexate [2b^221,222], vincristine/cyclophosphamide combined [4b ²⁴⁷ ], mitoxantrone [4b ²⁴⁰ ], idarubicin [4b ²⁴⁸ ], chlorambucil (NB, treated cats had alimentary lymphoma) [4c ¹²⁸ ] and vincristine [5 ²⁴⁹ ]. Vomiting occurred in 16% of cats receiving piroxicam, more often when the cat was also receiving cancer chemotherapy, particularly doxorubicin or carboplatin [4a ²⁵⁰ ]. However, carboplatin did not cause vomiting in nine healthy cats [3b ²³⁹ ]. Cisplatin is used frequently in experimental emesis research and causes vomiting in cats [2b^178,251], associated with serotonin release from the intestine [2b ²⁵² ], but the mechanism of cisplatin-induced vomiting in the cat may be different to other species [2b ¹⁴ ]. Cisplatin is not used clinically in cats because of extreme toxicity in this species [2b^178,251] [OEG B].

There are no published studies of antiemetic use in tumour-bearing cats receiving cancer chemotherapy. Some antiemetics that have been evaluated for protecting against chemotherapy-induced vomiting are not likely to be useful in the clinic [2b^{187,190–192}]. 5HT₃ antagonists have shown some efficacy against cisplatin-induced vomiting in the cat [2b^178,180], but, as mentioned above, this is not directly relevant to chemotherapy in the cat because cisplatin should not be used. Anecdotally, dolasetron combined with metoclopramide could reduce the emetic potential of many drugs [5 ¹⁷⁹ ] [OEG D]. While maropitant has demonstrated efficacy in preventing and treating nausea and vomiting induced by cisplatin in dogs, ²⁵⁴ there is no available evidence in cats.

Discussion

The current study is the first to attempt a comprehensive review the available evidence for causes, consequences, diagnosis and management of vomiting in the cat. The main aim of such a systematic review was, as far as possible, to present the available published evidence without prejudice or bias. For instance, it was necessary to report all the conditions where the published evidence suggests that it is a clinical sign. This can be helpful as it emphasises the necessity for keeping an open mind when investigating cats with signs of vomiting. Nonetheless, it is accepted that many clinicians may have their own opinions as to the validity of some of the reported associations. In this respect, the pathogenetic mechanisms for many of the conditions listed may not be clear and associations may actually be indirect (eg, disease A causes condition B which causes the vomiting). As a result, we have also attempted to highlight the most important causes of vomiting, especially those conditions that are especially important in cats. Such information represents our opinion, albeit after detailed review of the available literature and, thus, should be considered cautiously. It is possible that such information will need to be revised should new information become available in the future. In a similar manner, a wide array of diagnostic tests has been reported in the literature, yet many are uncommonly used in clinical practice owing to cost, availability or the fact that they have been superseded by better techniques. Again, therefore, we have highlighted those tests that we think to be of most use, based upon current knowledge, but recognise that opinions may change in time.

As is the case with many systematic reviews, a key study finding is that, despite the availability of numerous relevant publications, much of the evidence is weak (eg, LOE 4 or weaker, OEG C or D). The main exception is the information available on the emetic reflex in cats, largely as a result of the fact that much of the fundamental physiological knowledge has been derived from work in this species. While the relative dearth of more robust evidence, in other areas of the review, does not mean that the data available are invalid, it highlights the limit to our current knowledge and the need for further studies to be performed at more robust evidence levels. In our opinion, many areas require further study, including the need to clarify which historical and physical examination findings are most useful in determining the need for further intervention, and which novel tests will be of use for vomiting cases. However, most important is the need for more objective clinical evidence on the efficacy of the various treatments for vomiting in cats, including the potential benefits of nutritional support, antiemetic drugs and ancillary therapies. This last area is likely to provide the greatest benefit to feline patients.

One limitation of the study is the methodology used, namely limiting the information reported to that identified on literature searches using terms to describe vomiting (eg, vomit, emesis, antiemetic, etc). Although this enables much of the relevant literature to be identified, we recognise that some publications may be missed, for instance if they did not mention a relevant term in the title, abstract or keywords. Nonetheless, arguably, limiting the review in such a way ensures that the most relevant articles are used, as the vomiting is more likely to be a significant part of the disease condition reported. Such missing information is better identified by performing further evidence-based reviews but from the perspective of specific conditions. These approaches are complementary and would be the best way to ensure that no gaps in knowledge are left.

Conclusions

This systematic review of the literature relating to causes, diagnosis and management of vomiting in cats has identified and summarised a large body of information. This review highlights the unfortunate fact that much of what we consider standard practice for cats is based on limited scientific evidence, on evidence extrapolated from other species or on expert opinion alone. Nonetheless, in some areas good evidence does exist, most notably concerning the mechanisms of vomiting. It is hoped that further research will improve knowledge in other areas, most notably concerning therapy for vomiting cats.