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Comparative Gastroenterology

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BACKGROUND
A fifteen year old Tennessee Walking Horse mare (intact female) presents to your clinic for acute colic (abdominal pain) that could not be controlled with xylazine (Rompun®). The mare had suffered intermittent colic episodes over the last 6 months that resolved with hand walking and administration of the non-steroidal anti-inflammatory agent, flunixin meglumine (Banamine®). On physical examination the mare was comfortable, had a heart rate of 48 (normal range 20-50 b/min), rectal temperature of 99.0 F (99 – 101 F), and normal respiratory rate. Capillary refill time was <2 sec (normal <2 sec) and the horse had pink mucus membranes. There was spontaneously gastric reflux from both nostrils. Nasogastric intubation produced 6 liters of fluid with a pH <3.0. Abdominocentesis, CBC, serum chemistry, and a rectal exam were unremarkable. Percutaneous ultrasonographic examination of the abdomen with a 3.5 mHz curvilinear probe showed the structure above (see image 1) in the left cranial abdomen at the level of the 13th intercostals space. Endoscopic examination of the stomach showed the above Image 2. While being fasted the mare would remain comfortable, however, when allowed access to food or water, the mare would become painful and produce gastric reflux.
 
Authors:
Drs. Benjamin Buchanan, Frank Andrews, and Robert Donnell
The University of Tennessee
College of Veterinary Medicine

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DIAGNOSIS

This mare had a pyloric-duodenal intussusception secondary to caudal movement of a pyloric mass. The characteristic target sign was obtained by imaging through the apex of the intussusception where the intussusceptum is surrounded by fluid and the intussuscipiens. In this case, the classic target sign was imaged in the 13th ICS at 10-19 cm of depth and the intussusceptum could be followed caudally to the right 14th ICS. The duodenum in the 15th ICS was fluid filled and slightly dilated with a 6 mm wall. When followed cranially from the 13th ICS, the characteristic ring sign was lost and the duodenum appeared dilated with a solid intraluminal mass surrounded by fluid. This appearance was consistent as far cranially as the duodenum could be imaged. This intussusception most likely cause of the pyloric outflow obstruction and the source of gastric reflux. Gastroscopy twelve hours after presentation showed a tight stricture of the glandular mucosa close to the lesser curvature, obscuring any view of the pylorus (Image 2). Attempts to pass the endoscope down the center of the stricture were met with resistance. After three days with no improvement or worsening, the mare was scheduled for standing laparoscopic surgery to evaluate the duodenum and determine if a correction was possible. During the course of the surgery, the mare died of complications. A post mortem examination found a 16 X 7 X 3.5 grey to green polypoid mass originating from glandular region of the stomach protruding through the pyloric antrum, producing a 20 cm intussusception of the pylorus into the proximal duodenum (Image 3). At intussusception, the opposing surfaces of the mass and the proximal duodenum were multifocally ulcerated and adhesed. Histologicallly, this mass was consistent with an adenomatous polypoid gastric hyperplasia. This condition is rare in the horse and only one referenced case has been reported. This case will appear in JAVMA later this year as What’s your diagnosis?

 
 



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