Petrographic and geochemic evaluation of equine enteroliths.
OBJECTIVE
To characterize the texture, mineralogic features, and chemical features of enteroliths obtained from horses.


METHODS
Enteroliths from 13 horses with colic.


METHODS
Enteroliths were harvested from 13 horses that underwent ventral midline celiotomy for treatment of colic or necropsy because of colonic obstruction and rupture caused by enteroliths. Dietary and environmental history were determined via questionnaires or evaluation of medical records. In 7 horses that underwent surgical treatment for enterolithiasis, samples of colonic contents were obtained via an enterotomy in the pelvic flexure. Colonic concentrations of magnesium (Mg), phosphorus (P), sulfur (S), sodium (Na), calcium (Ca), and potassium (K) were determined. Enteroliths were analyzed via electron microprobe analysis and X-ray diffraction.


RESULTS
Enteroliths varied widely regarding degree of porosity, presence and distribution of radiating texture, and composition and size of the central nidus. A distinct concentric banding was identifiable in all enteroliths. Struvite was the predominant component of all enteroliths, although Mg vivianite was identified in 5 enteroliths, and there were variable quantities of Na, S, K, and Ca in the struvite within enteroliths. Despite an abundance of Ca in colonic fluids, Mg-phosphate minerals were preferentially formed, compared with Ca-phosphates (apatite), in equine enteroliths.


CONCLUSIONS
Enteroliths comprise 2 major Mg phosphates: struvite and Mg vivianite. There is wide variability in macrotexture and ionic concentrations between and within enteroliths.
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, College of Letters & Science, University of California, Davis 95616, USA.
D M
DM
Hassel
P S
PS
Schiffman
J R
JR
Snyder
D000818:Animals; D002137:Calculi / Q000737:chemistry / Q000662:veterinary*; D003085:Colic / Q000209:etiology / Q000378:metabolism / Q000662:veterinary; D003108:Colonic Diseases / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D004577:Electron Probe Microanalysis / Q000662:veterinary; D005766:Gastrointestinal Contents / Q000737:chemistry; D006734:Horse Diseases / Q000378:metabolism* / Q000473:pathology; D006736:Horses; D007415:Intestinal Obstruction / Q000209:etiology / Q000378:metabolism / Q000662:veterinary; D017616:Magnesium Compounds / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D000069877:Struvite; D014961:X-Ray Diffraction
D017616:Magnesium Compounds; D010710:Phosphates; D000069877:Struvite