Enterolith

Equine enteroliths are found by walking pastures or turning over manure compost piles to find small enteroliths, during necroscopy, and increasingly, during surgery for colic. Therefore, the incidence of asymptomatic enteroliths is unknown.

Equine enteroliths are typically smoothly spherical or tetrahedral, consist mostly of the mineral struvite{{cite journal| author = Blue MG| title = Enteroliths in horses--a retrospective study of 30 cases| journal = Equine Veterinary Journal| volume = 11| issue = 2| pages = 76–84|date=April 1979| pmid = 477649| doi = 10.1111/j.2042-3306.1979.tb01307.x}}{{cite journal|vauthors=Blue MG, Wittkopp RW | title = Clinical and structural features of equine enteroliths| journal = Journal of the American Veterinary Medical Association| volume = 179| issue = 1| pages = 79–82|date=July 1981| pmid = 7251465}} (ammonium magnesium phosphate), and have concentric rings of mineral precipitated around a nidus.{{cite journal|vauthors=Lloyd K, Hintz HF, Wheat JD, Schryver HF | title = Enteroliths in horses| journal = The Cornell Veterinarian| volume = 77| issue = 2| pages = 172–86|date=April 1987| pmid = 3552440}}

Enteroliths in horses were reported widely in the 19th century, infrequently in the early 20th century, and now increasingly. They have also been reported in zebras: five in a zoo in California{{cite journal|vauthors=McDuffee LA, Dart AJ, Schiffman P, Parrot JJ | title = Enterolithiasis in two zebras| journal = Journal of the American Veterinary Medical Association| volume = 204| issue = 3| pages = 430–2|date=February 1994| doi = 10.2460/javma.1994.204.03.430| pmid = 8150704}} and one in a zoo in Wisconsin.{{cite journal|vauthors=Decker RA, Randall TL, Prideauz JW | title = Enterolithiasis in a confined Hartman's mountain zebra| journal = Journal of Wildlife Diseases| volume = 11| issue = 3| pages = 357–9|date=July 1975| pmid = 1152174| doi = 10.7589/0090-3558-11.3.357| s2cid = 2419057| url = http://www.jwildlifedis.org/cgi/pmidlookup?view=long&pmid=1152174}} Struvite enteroliths are associated with elevated pH and mineral concentrations in the lumen.{{cite journal|vauthors=Hassel DM, Rakestraw PC, Gardner IA, Spier SJ, Snyder JR | title = Dietary risk factors and colonic pH and mineral concentrations in horses with enterolithiasis| journal = Journal of Veterinary Internal Medicine| volume = 18| issue = 3| pages = 346–9| year = 2004| pmid = 15188822| doi = 10.1111/j.1939-1676.2004.tb02556.x| doi-access = free}} In California, struvite enteroliths are associated also with a high proportion of alfalfa in the feed and less access to grass pasture. This association has been attributed to the cultivation of alfalfa on serpentine soils, resulting in high concentrations of magnesium in the alfalfa.{{Citation needed|date=October 2008}}

In humans, enteroliths are rare and may be difficult to distinguish from gall stones. Their chemical composition is diverse, and rarely can a nidus be found. A differential diagnosis of an enterolith requires the enterolith, a normal gallbladder, and a diverticulum.{{cite journal|vauthors=Yang HK, Fondacaro PF | title = Enterolith ileus: a rare complication of duodenal diverticula| journal = The American Journal of Gastroenterology| volume = 87| issue = 12| pages = 1846–8|date=December 1992| pmid = 1449155}}{{cite journal|vauthors=Chuang JH, Chan HM, Huang YS, Hsieh JS, Huang TJ | title = Enterolith ileus as a complication of duodenal diverticulosis--one case report and review of the literature| journal = Gaoxiong Yi Xue Ke Xue Za Zhi| volume = 9| issue = 8| pages = 488–93|date=August 1993| pmid = 8230370}}

An enterolith typically forms within a diverticulum. An enterolith formed in a Meckel's diverticulum sometimes is known as a Meckel's enterolith. Improper use of magnesium oxide as a long-term laxative has been reported to cause enteroliths and/or medication bezoars.{{cite journal |vauthors=Tatekawa Y, Nakatani K, Ishii H, etal | title = Small bowel obstruction caused by a medication bezoar: report of a case| journal = Surgery Today| volume = 26| issue = 1| pages = 68–70| year = 1996| pmid = 8680127| doi = 10.1007/BF00311997| s2cid = 24976010}}

Most enteroliths are not apparent and cause no complications. However, any complications that do occur are likely to be severe. Of these, bowel obstruction is most common,{{cite journal|vauthors=Gamblin TC, Glenn J, Herring D, McKinney WB | title = Bowel obstruction caused by a Meckel's diverticulum enterolith: a case report and review of the literature| journal = Current Surgery| volume = 60| issue = 1| pages = 63–4| year = 2003| pmid = 14972313| doi = 10.1016/S0149-7944(02)00650-5}} followed by ileus{{cite journal|vauthors=Steenvoorde P, Schaardenburgh P, Viersma JH | title = Enterolith ileus as a complication of jejunal diverticulosis: two case reports and a review of the literature| journal = Digestive Surgery| volume = 20| issue = 1| pages = 57–60| year = 2003| pmid = 12637808| doi = 10.1159/000068852| s2cid = 20592835}} and perforation. Bowel obstruction and ileus typically occur when a large enterolith is expelled from a diverticulum into the lumen. Perforation typically occurs within the diverticulum.{{citation needed|date=August 2020}}

On plain X-rays, the visibility of the enterolith depends on its calcium content. Calcium-rich stones usually demonstrate a radiodense rim and a relatively radioluscent core. Choleic acid stones are almost always radiolucent. They sometimes can be visualized on CT scans without contrast; presence of contrast in the lumen may reveal the enterolith as a void. Most often, they are visualized using ultrasound.{{cn|date=October 2023}}

Although recent surveys of enterolith composition are lacking, one early review notes struvite (as in equines), calcium phosphate, and calcium carbonate and reports choleic acid.{{cite journal| author = Raper HS| title = A Human Enterolith containing Choleic Acid| journal = The Biochemical Journal| volume = 15| issue = 1| pages = 49–52| year = 1921| pmid = 16742974| pmc = 1258956| doi = 10.1042/bj0150049}} Deoxycholic acid and cholic acid have also been reported.{{cite journal|vauthors=Fantl P, Rollo AJ, Strosberg H | title = Chemical analysis of an enterolith| journal = Gut| volume = 6| issue = 4| pages = 384–6|date=August 1965| pmid = 4953381| pmc = 1552302| doi = 10.1136/gut.6.4.384}}

In simple cases of obstruction, where there are no complications, a variety of non-surgical and surgical techniques are used to remove the enterolith. These include crushing the enterolith and milking it back to the stomach or forward to the colon, surgical removal via an uninvolved segment of the gastrointestinal tract, and resection of the involved segment.{{citation needed|date=August 2020}}

• Acid-base physiology
• Bezoar

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| ICD10 = {{ICD10|K|56|4}}

| ICD9 = {{ICD9|560.39}}

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| SNOMED CT = 40515007

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{{wiktionary|enterolith|nidus}}

Category:Rare diseases

Category:Gastrointestinal tract disorders