Enteroliths in horses--a retrospective study of 30 cases.

In a retrospective study of selected cases, abdominal colic in 30 horses was attributed to enterolith obstructions of the large intestine. Obstructions caused by "true" enteroliths were confined to horses more than four years old. Prominent clinical features were recurrent mild abdominal pain, inappetance, gaseous distension and minimal intestinal motility. The various aspects of the clinical syndrome, including diagnostic problems and clinical management, are discussed. Most obstructing enteroliths were found near the beginning of the small colon and most horses contained only a single major concretion. Enteroliths were formed by mineral deposition in concentric layers about a central nidus of ingested material and were spherical or tetrahedral in shape. Intestinal concretions were found to consist primarily of ammonium magnesium phosphate.