Abomasal ulceration and abomaso-pleural fistula in an 11-month-old beefmaster bull

Abstract

An 11-month-old, beefmaster bull presented with anorexia and signs of respiratory disease. Physical examination, thoracic ultrasonography and radiography, and pleural fluid analysis indicated pericarditis and septic neutrophilic pleuropneumonia. Postmortem findings were abomasal adherence to the diaphragm, a fibrotic fistulous tract connecting the abomasum and pleural cavity, granulomatous abomasitis, granulomatous pericarditis, and fibrinonecrotic pleuritis.

An 11-month-old, beefmaster bull intended for show and subsequent breeding use was referred to the Veterinary Teaching Hospital and Clinics at Louisiana State University with a history of decreased appetite and weight loss for 1 mo. During the final week, the bull exhibited complete anorexia, intermittent bloat, and decreased fecal output. One week prior to referral, the bull was treated with antibiotics (ceftiofur, 2.2 mg/kg body weight (BW), IM, q24h) for the pneumonia and rumen trocarization for the intermittent bloat. The continued anorexia prompted modification of antibiotic therapy; oxytetracycline (11 mg/kg BW, IM, q24h) was administered for 2 d with no clinical improvement.

The significant physical findings upon presentation included lethargy, reluctance to move, fever (rectal temperature 40.5°C), tachycardia (132 beats/min), increased respiratory rate (32 breaths/min), and labored breathing. Thoracic auscultation and percussion revealed splashing fluid sounds associated with heart sounds, and tympany was detected in the dorsal right hemithorax. Moderate distension and tympany in the area of the left paralumbar fossa and pain in the region of the xiphoid process were found on initial physical examination. There were no significant findings on rectal examination. Laboratory results, which revealed leukocytosis (46 000 × 10⁹ white blood cells/L; reference range, 4000 to 12 000 × 10⁹/L); neutrophilia with a left shift (40 600 × 10⁹ neutrophils/L; reference range, 600 to 4000 × 10⁹, and 500 × 10⁹ bands/L; reference range, 0 to 100 × 10⁹/L), monocytosis (2100 × 10⁹ monocytes/L; reference range, 0 to 800 × 10⁹/L), and hyperfibrinogenemia (fibrinogen, 13 g/L; reference range, 3 to 7 g/L), indicated a severe, chronic, septic inflammation. Abnormal serum biochemical values included mild hyperglycemia (glucose, 6.9 mmol/L; reference range, 3.3 to 5.5 mmol/L), slight hypokalemia (potassium, 3.1 mmol/L; reference range 3.9 to 5.8 mmol/L), mild hypochloremia (chloride, 92 mmol/L; reference range, 95 to 110 mmol/L), metabolic alkalosis (total CO₂, 50.2 mmol/L; reference range, 21 to 31 mmol/L), and hypoalbuminemia (albumin, 21 g/L; reference range, 31 to 40 g/L). On ultrasonographic examination of the thorax, a number of abnormalities were noted, including a hyperechoic area measuring 10 cm × 12 cm on the right apical lobe of the lung, approximately 6 cm dorsal to the point of the shoulder; right-sided pneumothorax; minimal pleural fluid; and hyperechoic pericardial fluid. Pleural effusion, unilateral pneumothorax, pulmonary bullae, and an abscess in conjunction with bronchopneumonia were seen radiographically (Figure 1). No other abnormalities or any metallic foreign bodies were evident in the cranial part of the abdomen. Pneumoperitoneum was believed to be secondary to the previous rumen trocarizations. Results from the analysis of abdominal fluid were normal.

Figure 1. Continued.

Figure 1. Standing thoracic radiographs taken at the time of initial physical examination. a) Right lateral view of the cranial ventral part of the lung. Note the horizontal fluid-air interface in the ventral aspect (black arrows); the atelectic lung, secondary to unilateral pneumothorax (white arrows); and the abscess (A, arrowheads). b) Right lateral view of the caudodorsal part of the lung depicting the bronchopneumonia, unilateral pneumothorax, the pleural fluid line, and the abscess (A, arrowheads) at the level of the vena cava.

Initial antibiotic therapy included procaine penicillin (34 000 IU/kg BW, SC, q12h) and tilmicosin (10 mg/kg BW, SC, q72h). An indwelling chest tube was placed in the dorsal part of the right thorax to facilitate removal of pleural air. Exploratory rumenotomy failed to identify foreign bodies or abnormalities of the rumen and reticulum. A temporary rumenostomy was placed in the left paralumbar fossa for relief of the intermittent bloat and to provide a route for transfaunation and forced feeding.

The bull appeared slightly brighter 24 h postoperatively but remained febrile (rectal temperature 40°C), tachycardic (128 beats/min), and tachypneic (32 breaths/ min), and had a labored respiration. Ruminal distension was not present. Thoracic auscultation revealed muffled cardiac and respiratory sounds over the ventral part of the right hemithorax. Large quantities of pleural fluid, with moderate echogenicity, were noted on ultrasonographic examination. Thoracocentesis yielded a large amount of yellow cloudy fluid containing fibrin and plant fibers, prompting placement of an indwelling chest tube in the ventral part of the right hemithorax. The pleural fluid had a low nucleated cell count (1100 × 10⁹/L) and protein concentration (< 25 g/L). Cytologic evaluation of the pleural fluid revealed degenerative neutrophils and a mixed population of bacteria and yeast, suggestive of septic inflammation associated with presence of gastrointestinal contents. The leukogram abnormalities (35 000 × 10⁹ leukocytes/L, 27 500 × 10⁹ neutrophils/L, 500 × 10⁹ bands/L, and 3300 × 10⁹ monocytes/L) and hyperfibrinogenemia (12 g/L) persisted.

The owners elected to continue treatment, despite a grave prognosis. The pleural cavity was lavaged with sterile polyionic crystalloid solution twice daily. Antibiotic therapy, an indwelling chest tube with a one-way valve, and the rumenostomy for forced feeding and transfaunation were continued. Treatment was continued for 6 additional days. Further deterioration in the bull's condition necessitated humane euthanasia. Postmortem lesions included cranial displacement of the abomasum, a chronic fibrotic adhesion of the abomasum to the diaphragm, and localized chronic fibrotic peritonitis and diaphragmitis. Additionally, a fibrotic fistulous tract connecting the abomasal lumen and the right caudoventral quadrant of the pleural cavity was identified. Chronic-active granulomatous abomasitis with multiple mucosal ulcerations, fibrinous parietal and visceral pleuritis with pleural fibrosis, atelectic and fibrotic right lung lobes were also present. Granulomatous pericarditis accompanied the fibrinonecrotic pleural inflammation. A disseminated necrotizing hepatitis and multifocal splenitis were also noted.

Primary abomasal fistulas are not commonly reported. Most reported cases of abomasal fistula are postsurgical complications, typically following right paramedian abomasopexy or percutaneous abomasopexy (1,2,3). Two cases of postsurgical abomaso-umbilical fistula have been described in calves (4,5). Only 3 cases of abomaso-pleural fistula, 1 acute and 2 peracute, were reported in 70 cases of abomasal fistulas associated with abomasal ulcers in calves (6). Hemmingsen (6) describes a scenario where, initially, the perforating abomasal ulcers resulted in localized peritonitis with adhesion of abomasum to the diaphragm and formation of a fistula with the pleural cavity. To our knowledge, no cases of a subchronic or chronic abomaso-pleural fistula have been previously reported in the literature.

In the present case, the abomaso-pleural fistula was associated with cranial displacement of the abomasum. Abomasal displacement is seen more commonly in mature periparturient dairy cows and less commonly in first-calf heifers and male cattle (7). Abomasal adhesions were reported in only 10% of animals (33/310) with abnormalities affecting the abomasum evaluated in a postmortem survey (8). Sixty-six percent (20/33) of these abomasal adhesions involved the diaphragm (8). Primary abomasal ulcerations and localized or generalized peritonitis have been reported with abomasal displacements (9,10,11,12,13,14,15). Abomasal atonicity, increased acid secretion, gastritis, and physical abrasion of the mucosa by coarse ingested material are thought to lead to abomasal ulceration (7). In contrast, fatal abomasal ulcers are often single lesions, most frequently observed in suckling calves (16,17). These fatal abomasal ulcers of unknown etiology have been sometimes associated with copper deficiency (16,17).

The sequence of events that led to cranial displacement of the abomasum, diaphragmatic adhesion, and formation of the communicating abomaso-pleural fistula could not be determined. A foreign body was not detected radiographically or at postmortem; therefore, a perforating foreign body was considered unlikely. However, a nonmetallic foreign body could have been associated with the original lesion, and then dissolved by the acidic pH of the abomasum. Abomasal displacement has been associated with abomasal ulceration (9). We speculate that, in this young bull, type III (perforated) abomasal ulcerations and localized peritonitis were associated with cranial displacement of the abomasum, which resulted in fibrosis and adhesion of the abomasum to the diaphragm. The ulcerations may have then progressed to form an abomasal fistula with the pleural cavity. The fistula had a smooth appearance, indicating chronicity. The progressively decreased appetite may have limited the volume of ingesta leaking into the pleural cavity, allowing the condition to have a prolonged or chronic duration. However, several hours following the transfaunation, the pleural cavity filled with gastric contents, precipitating the rapid clinical deterioration. The present report is the first case of subchronic to chronic abomaso-pleural fistula associated with abomasal ulcers in a young bull. CVJ