The presence in the hind gut of enteroliths or ‘stones’ comprised of hard mineral material called Struvite, chemically magnesium ammonium phosphate. The stones vary from pea sized to grapefruit size and often form around small indigestible objects like metal, rubber bands, baling twine, small pebbles, or hair and can develop slowly over a period of years. They develop in the large colon and may move to the small colon causing obstruction. Enteroliths are associated with diets high in Magnesium and protein, particularly Lucerne rich diets and with certain breeds like Arabians, Morgan’s, and American Saddlebred. The disease is encountered worldwide but seems to be more common in America, with high incidence in Florida & California. Cases are comparatively rare in Australia.
The symptoms relate to the size of the enteroliths and their position in the hind gut. Small stones may be expelled in the manure, but large ones can cause bowel obstruction and colic. The signs may be intermittent and resolve spontaneously only to recur later. Diagnosis can be difficult and rectal examination and radiography may be used to confirm the presence of stones. Treatment is by surgical removal of the enterolith.