Idiopathic muscular hypertrophy of the ileum in horses: Nine cases (2013‒2023)

This case series describes idiopathic muscular hypertrophy of the ileum in nine horses, focusing on clinical presentation, histopathological findings, treatment and outcomes. The median age of horses was 9 years (range: 2‒18 years), with no breed or sex predisposition. The clinical signs were nonspecific. A definitive diagnosis was established with histopathological examination, which revealed hypertrophy of the inner circular layer of the tunica muscularis . All horses exhibited concurrent inflammatory bowel disease. One horse presented with ileal pseudodiverticula. Three horses were euthanased before hospital discharge and two horses were euthanased 11 days and 6 years, respectively, after diagnosis. One horse returned successfully to work, and the others were lost to follow‐up. In conclusion, ileal idiopathic muscular hypertrophy is an uncommon disease with a still poorly understood pathophysiology. The prognosis is variable and further studies are needed to more accurately evaluate the long‐term outcome and the possibility of medical and dietary management of this affection.