Veterinary Diagnostic Imaging

History and clinical signs

A 10-year-old, spayed female, Yorkshire terrier was admitted to North Town Veterinary Hospital with the history of vomiting 12 times over the past 3 d. On presentation, she was clinically lethargic, anorexic, and 5% dehydrated. On abdominal palpation, she had marked cranial ventral pain and possible splenomegaly.

A complete blood (cell) count (CBC) indicated leukocytosis 22.5 × 10⁹/L (reference range, 6.0–17.0 × 10⁹/L) with a neutrophil count of 19.9 × 10⁹/L (reference range, 3.0–11.5 × 10⁹/L) that represented 88.5% of the differential’s total count. The hematocrit was 0.35 L/L (reference range, 0.39 to 0.69 L/L) with a red blood cell count of 5.3 × 10¹²/L (reference range, 5.5–8.5 × 10¹²/L) (Vita-Tech, Markham, Ontario). Results from a biochemical profile demonstrated an elevation in alkaline phosphatase (ALP) 648 U/L (reference range, 24–141 μmol/L), total bilirubin 5.8 μmol/L (reference range, 0.0–5.0 μmol/L), conjugated bilirubin 3.3 μmol/L (reference range, 0.0–2.0 μmol/L), creatinine kinase 364 U/L (reference range, 5–235 U/L), amylase 12 010 U/L (reference range, 150–1350 U/L), lipase 11 690 U/L (reference range, 0–900 U/L), and an increased sodium/potassium (Na/K) ratio of 45 (reference range, 25–40) (Vita-Tech, Markham).

An abdominal radiograph (Sedecal; Horizon Medical Services, Mississauga, Ontario) showed the presence of hepatomegaly, splenomegaly, fluid-filled intestinal loops, and the loss of radiographic detail in the cranial ventral quadrant, consistent with inflammation. An abdominal ultrasonograph (ATL HDI 5000; Philips Medical Systems, Markham, Ontario) showed the following: a thickening of the duodenum; a small resolving pancreatic abscess; inflammation near the insertion point of the major duodenal papilla into the duodenum; hypoechoic pancreatic inflammation near the head of the pancreas, as well as hyperechoic densities surrounding the adjoining adipose tissues (Figure 1); and finally, a normal diameter for the left branch of the pancreatic duct. Hepatomegaly and splenomegaly were also confirmed by ultrasonography, as was a suspicion of the presence of a cholelith within the gallbladder.

Figure 1.

a) An ultrasonographic image of the duodenum from an axial plane in the right cranial ventral part of the abdomen. This projection demonstrates an area of multiple mixed echogenic densities that represent both the head of the pancreas (curved arrow) and the insertion of the pancreatic duct and major duodenal papilla into the duodenum (thick arrow). Note the thickened appearance of the papilla within the wall of the duodenum, which represents inflammation. The hyperechoic areas around the pancreas are associated with peripancreatic fat necrosis and pancreatic fibrosis (asterix); b) A lateral view of the same area of the duodenum (thin arrow) outlines an irregular contour of the head of the pancreas (large arrow). On both images the duodenum is clearly thickened.

The dog was diagnosed as having an acute episode of pancreatitis and was treated with the following medications: Cefazolin (Novopharm, Toronto, Ontario), 20 mg/kg bodyweight (BW), IV, q8h; butorphanol (Torbugesic; Wyeth Canada, Guelph, Ontario), 0.3 mg/kg BW, IV, prn; diphenhydramine (Benadryl; Sandoz, Boucherville, Quebec), 2 mg/kg BW, IM, q12h; metro-nidazole (Hospira Healthcare Corporation, Montreal, Quebec), 10 mg/kg BW, IV, q12h; and IV fluids (P148; Baxter, Toronto, Ontario).

Over the next 48 h, the dog improved clinically and became bright and responsive, even playful. The lipase level returned to almost normal at 2180 U/L, but the ALP increased to 1825 U/L and total bilirubin escalated to 178 μmol/L (Vettest; Idexx, Toronto, Ontario). During the following few days, several attempts at swallowing small amounts of fluids resulted in the dog vomiting everything within a few hours. Repeat ultra-sonographic examinations did demonstrate a patent pancreatic duct (Figures 2 and 3). The inflammation near the head of the pancreas continued to lessen on ultrasonographic evaluation, even though it was difficult to clearly outline the periphery of the entire organ. At this point, the owner informed us that the dog had been refusing meals with increasing frequency during the past few months. Armed with this new information and the fact that the dog had maintained a bright demeanor throughout her stay in hospital, the possibility that she had a chronic pancreatic condition, or even worse, a neoplastic invasion, began to seem more probable.

Figure 2.

An ultrasonographic image illustrating the left lobe of the pancreas (large arrow). The organ is viewed ventral to the gastric wall. The left branch of the pancreatic duct is visualized within its center (arrow heads). The lack of dilatation indicates that the duct is still patent and functionally draining near the head of the pancreas, where the lesions appear at their worst.

Figure 3.

A series of ultrasonographic images demonstrating both the extremity of the right and left lobes of the pancreas plus their associated duct branches. In these 3 images, the pancreatic duct (white arrow) is within normal limits and measures from 1.2 to 0.8 mm in diameter.

A contrast enhanced (Omnipaque 350; Amersham Health, Oakville, Ontario) spiral computed tomography (CT) (Toshiba Express CT Scanner; Toshiba Medical Systems, Markham, Ontario) examination of the cranial portion of the abdomen was performed to evaluate the surrounding inflammation and the viability of the pancreas (Figure 4). Two different radiolucent areas localized at the head of the pancreas, along with the presence of a small resolving pancreatic abscess, were apparent; an 0.8-cm diameter cholelith was also identified within the gallbladder. The distal segments of each pancreatic lobe also appeared to be relatively normal and their associated pancreatic ducts were not distended. Very little active peripancreatic inflammation was apparent along the surface of the organ.

Figure 4.

A contrast-enhanced axial CT image of the pancreas near its point of attachment to the duodenum (thick arrow). Both the left and right lobes of the organ are outlined by an arrowhead on these images. A long arrow denotes a very radiolucent area that demarks an avascular zone within the pancreas that has been infiltrated with fat. This interpretation was confirmed by measuring its Hounsfield or CT number. The asterix identifies a 2nd area of decreased perfusion that represents pancreatic fibrosis and necrosis. Very little evidence of acute inflammation is visualized in the form of fibrin tags surrounding the diseased areas, suggesting that this is a more of a chronic lesion then first believed.

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Discussion

Our clinical diagnosis was chronic pancreatitis resulting in marked infiltrative fibrosis and necrosis near the head of the organ. This dog also periodically had repetitive episodes of acute flare-ups, most of which were subclinical and undetected. Pancreatic fibrosis in canine models has been shown to be characterized by interlobular fibrosis that creates cirrhosis-like visualization, as noted in humans (1). In cases of acute pancreatitis, the area of inflammation usually occurs as a single discrete area within the pancreas, as opposed to a generalized distribution (2). The location of these lesions seems to be randomly distributed throughout the pancreas in most cases.

The primary concern for this animal was whether the pancreatic duct and its associated major duodenal papilla were patent. Even though, at first, the total bilirubin values were increasing at a dramatic rate, it was decided to treat the dog medically, since she was exhibiting only a mild degree of morbidity. In dogs where illness has become complicated with the expression of a significant level of cholestasis, one of the following interventions could be attempted: an ultrasonographic guided cholecystocenthesis (3), if the animal was clinically jaundiced, yet still bright, or a gallbladder transposition to the jejunum, if the animal became clinically depressed and life threateningly toxic. The most sensitive way to evaluate the patency of the pancreatic duct is through the use of endoscopic retrograde pancreatography (4). When the duct has been shown to be effectively obstructed, the placement of a short-term stent has been useful, but in as little as 1 wk after the insertion of a stent, fibrosis and damage to the duct can occur (5,6). In other nonresolving cases, a pancreatojejunal anastomosis sealed with fibrin tissue glue has been successful (7).

In this example, multiple consecutive images of the distal portion of the pancreatic duct done over several days, using a linear L12-5 ultrasound probe (HDI 5000 with Sono CT® and X-Res ® resolution; Phillips Medical, Markham, Ontario) showed it to be patent, even when the total bilirubin values continued to rise. Color Doppler imaging (HDI 5000; Phillips Medical, Markham, Ontario) also confirmed the viability of the organ, at least over the 80% of its surface that could be visualized (Figure 5). At the same time, the common bile duct was found to be nondistended. The contrast enhanced CT scans over the pancreas confirmed the chronic nature of the condition and identified the location and severity of the pancreatic fibrosis (8), thereby ruling out the possibility of any neoplastic invasion.

Figure 5.

Color Doppler ultrasonographic perfusion image of the left branch of the pancreas confirming its viability and potential for recovery.

Despite normal serum lipase/amylase values and a bright demeanor, the dog continued to vomit all ingested fluids and light ingesta over the following 5 d. At this point, the owner agreed to allow the placement of a jejunostomy tube in order to initiate enteric feeding (Rebound; Rebound Animal Health, Atlanta, Georgia, USA), while the pancreatic crisis fully resolved. A modified 6 French Mila urinary catheter (Mila International, Florence, Kentucky, USA) was surgically implanted into the proximal part of the jejunum (9) over a length of 16 cm. A Trucut biopsy of the pancreas taken at the time of surgery confirmed the presence and severity of the pancreatic fibrosis indicated by the CT examination. This fibrosis could not be verified by ultrasonography alone. The progression of the dog’s condition was monitored following the reduction of the total bilirubin values. The bilirubin values returned to normal by the 10th day. At that point, the pancreatic duct had improved concurrently and sufficiently enough to slowly resume small gastric feedings in increasing portions. The dog continued to make a full recovery, eating normal daily portions of a low fat food (Royal Canine–Low Fat, Royal Canine, Bolton, Ontario), all within 1 wk. The jejunostomy tube was removed 2–3 wk later.

In this particular and interesting case, the use of diagnostic imaging helped to clearly identify not only the dog’s ailment but, more importantly, the overall prognosis of the patient, and whether it was ethically justified to pursue treatment. The images indicated that the condition of the pancreatic duct would probably resolve with time, allowing the clinician to follow an appropriate course of action, and achieve a positive outcome.