by Cindy Lockworth
In the veterinary team of a biomedical research facility, we strive to maintain the health and welfare of animals, as healthy animals produce valid and valuable data needed for vital research studies. Occasionally, we encounter unanticipated clinical cases that can be both challenging and interesting. This occurred during a recent study involving swine in our facility.
Due to their size and their specific anatomic and physiologic characteristics, swine have become extremely valuable in the field of biomedical research as surgical models, as well as research models for specific diseases such as atherosclerosis and septic shock. Pigs utilized in research are generally obtained from a range of health status levels which may include open/closed herds, high health herds or specific pathogen free sources. Thus, variations in management practices and the overall susceptibility of swine to certain conditions persist.
Recently, we had a 9 month old castrated Yorkshire enrolled in an IACUC approved study. The pig was part of a study involving two surgical procedures that did not require body cavity penetration. Following a single instance of regurgitation 3 months after surgery, the pig was clinically normal in appearance until 5 months post-op, at which time the pig began a 3 week period of repeated incidents of regurgitation.
Prior to the onset of clinical signs, the pig was well conditioned, active, and growing. During the 3 weeks of regurgitation, the pig was observed to have a voracious appetite, yet began a slow and consistent decline in weight. The pig remained adequately hydrated. With the exception of declining body condition, no other abnormalities were noted upon physical exam.
From the onset of regurgitation until euthanasia, the pig was treated medically. Omeprazole and ondansetron were administered. Simplicef was given for a 6 day duration due to nasal discharge. Feed was modified in frequency, volume, and consistency; consistency ranged from thick gruels to liquid soy protein diet.
As is commonly the case in the research environment, no diagnostic work-up was performed in life. However, differentials for regurgitation included stricture, esophagitis, megaesophagus, or mass/tumor. Necropsy and histopathology investigations were performed. Gross examination confirmed the diagnosis of chronic gastroesophageal stricture with acquired megaesophagus.
Ulceration of the pars oesophagea region of the stomach has been described since the 1950’s in swine. Studies have shown that 32-65% of slaughter pigs have evidence of gastric ulcers. The pathogenesis remains unknown.
In this unusual and interesting case, the pig developed a persistent ulcer in the region of the gastroesphageal junction. Chronic inflammation and fibrosis caused a stricture of the lumen, resulting in a 4 mm diameter lumen which allowed only water to pass from the esophagus into the stomach. Although the differential diagnoses for gastric ulceration includes various infectious agents, in the research setting, stress is presumed to be a leading cause.