Diagnostic and Clinical Course of Small Colon Recurrent Impaction Associated with Severe Myenteric Ganglionopathy in A Mare

A 10-year-old Koninklijk Warmbloed Paardenstamboek Nederland (KWPN, Netherlands-based organiza- tion for registration of the Dutch Warmblood horses) mare was evaluated three times over four months because of recurrent colic. At every referral, a physical examination revealed a small colon impaction, which partially responded to food deprivation and oral administration of water and magnesium sulphate. Due to the recurrent nature of the small colon impaction, several differential diagnoses were considered: inflammatory bowel disease (IBD), chronic salmonellosis and myenteric ganglionopathies. At first admis- sion, an exploratory laparotomy was proposed, but the owner declined. On the second hospitalisation, the mare underwent a standing exploratory laparoscopy, but no abnormality related to the small colon was detected and resolved with a soap-based enema. At the third hospitalisation, the owner agreed to the exploratory laparotomy, which allowed surgical biopsies of the caecum and the large and small colon. Lymphomonocytic enteritis and mild myenteric ganglionitis were diagnosed. After laparotomy, the mare regularly fed and defecated, but a few days later, tachycardia, fever and abun- dant gastric reflux occurred. As the clinical condition rapidly deteriorated, the owner elected for euthana- sia. A post-mortem histological examination showed severe chronic lymphocytic enterocolitis and typhli- tis associated with the marked depletion of myenteric ganglion bodies. Small colon impaction is a very common disorder of the small colon in horses. In the presence of myen- teric ganglionopathies, this case proposes the controversial matter of primary or secondary disorders of enteric neuromuscular function as the base of repeated small colon impactions of the horse. In this mare, recurrent small colon impaction was considered secondary to severe myenteric ganglionopathy associated with chronic intestinal pseudo-obstruction.