Equine Enterolithiasis Study Guide

Overview and Clinical Importance

Enterolithiasis refers to the formation and presence of mineral concretions (enteroliths) within the gastrointestinal tract, specifically the large colon of horses. These intestinal stones are composed primarily of struvite (magnesium ammonium phosphate) and form around a central nidus such as a pebble, piece of metal, baling twine, or other ingested foreign material. Enterolithiasis represents a significant cause of surgical colic, particularly in endemic regions such as California, Florida, and the southwestern United States.

The condition is clinically important because enteroliths can cause partial or complete intestinal obstruction, leading to colic of varying severity. At endemic referral hospitals like UC Davis, enterolithiasis accounts for approximately 15% of colic admissions and 28% of surgical colic cases. Early recognition and surgical intervention before intestinal rupture are critical for favorable outcomes.

Etiology and Pathophysiology

Formation Mechanism

Enteroliths form through a process of concentric mineral deposition around a central nidus over months to years. The process is analogous to pearl formation in oysters. The nidus can be any small ingested foreign object including pebbles, sand grains, metal fragments, rubber pieces, hair, or baling twine.