Bouveret syndrome is caused by a large stone passing through a bilioduodenal fistula causing gastric outlet obstruction. Morbidity and mortality rates have decreased in recent years but remain high, estimated at 60% and 12% to 30%, respectively. Unfortunately, the chance of misdiagnosis is still high due to non-specific symptoms and laboratory findings.
Bouveret syndrome is the most infrequent variant of gallstone ileus, with a little over 300 cases in literature since its first description in 1654 through 2008. It results from a gallstone entering the intestinal lumen and causing obstruction at the gastric outlet and occasionally in other portions of the intestine as well. The entry point is typically a fistula between the gallbladder and a portion of the stomach or intestine.
The risk factors for Bouveret syndrome are similar to the risk factors of gallstones since gallstones play an integral role in the etiology of Bouveret syndrome. These risk factors for gallstones can be remembered using the 5-F rule mnemonic: fair (more prevalent in white populations), fat (body mass index (BMI) greater than 30), female gender, fertile (one or more children) and forty (age older than 40). The well-studied risk factors for Bouveret Syndrome include a history of cholelithiasis, stones greater than 2 cm to 8 cm, female gender, and age older than 60 years. It has been reported that approximately 43% to 68% of patients have a history of recurrent biliary colic, jaundice, or acute cholecystitis. Unfortunately, mortality ranges from 12% to 27% partially because of misdiagnosis and delayed discovery and partly because the symptoms at presentation are often non-specific as are biochemical investigations.
Bouveret syndrome typically occurs secondary to recurrent inflammation of the gallbladder as it abuts a portion of the gastrointestinal (GI) tract in the formation of adhesions between the two tissues or large stones that form necrosis along the gallbladder, which can eventually form a fistula between the two. In 60% of the cases, the fistula is cholecystoduodenal, but less common variants are cholecystocolic (17%), cholecystogastric (5%), and choledochoduodenal (5%). The biliodigestive fistula allows the passage a large gallstone, usually resulting in gastric outlet obstruction due to the most common location. The gallstones that cause obstruction are usually more than 2.5 cm, as those smaller than 2.5 cm usually pass through spontaneously and are managed conservatively.
The presentation Bouveret syndrome is typically non-specific, and often with waxing and waning symptoms of nausea, vomiting, abdominal distension and pain due to the varying positions of the gallstone. The patient may also exhibit epigastrium and right hypochondrium pain, along with signs of dehydration and weight loss. Less frequently, Bouveret syndrome may present with hematemesis secondary to duodenal and celiac artery erosions or with the expulsion of stones in his or her vomitus. Usually, the symptoms begin 5 to 7 days before a medical consultation. Importantly, the intensity of the pain often does not correlate with the underlying anatomic alteration.
A physical exam is also non-specific, although one may appreciate dry mucous membranes, abdominal distension, abdominal tenderness, high-pitched bowel sounds, and obstructive jaundice.
Unfortunately, laboratory studies are typically non-specific. Labs may show jaundice and hepatic enzyme alterations, but this only encompasses one-third of the patients with Bouveret syndrome. Leucocytosis, hydroelectrolytic, acid-base alterations and renal failure may also be present, but the grade depends on the comorbidity, the intensity of the inflammatory response and the compensatory mechanisms of the individual. As far as imaging is concerned, the constellation of pneumobilia, bowel obstruction, and an aberrant gallstone is highly suggestive of Bouveret syndrome but is only found in 40% to 50% of cases. Ultrasound may be useful, showing possible cholecystitis, dilated stomach, pneumobilia, and ectopic location of gallstone, yet bowel gas makes it suboptimal. Also when the gallbladder is contracted, it may be difficult to detect the exact location of the stone (orthotopic or ectopic) with ultrasound.
Abdominal radiographs can also be used. These can show pneumobilia, intestinal obstruction, an aberrantly located gallstone, air-fluid levels in the right upper quadrant due to air in gallbladder or stomach dilation, and a change in location of a previously observed stone. However, abdominal radiographs are only diagnostic in 21% of Bouveret’s syndrome cases. CT is the imaging modality of choice, with an overall 93% sensitivity, 100% specificity, and 99% diagnostic accuracy. In addition to its higher accuracy compared to plain radiograph or ultrasound, it can also provide important information about the presence of a fistula, presence of abscess, inflammatory state of the surrounding lumen and tissue, size of gallstone, and the number of gallstones. In patients unable to tolerate oral contrast or with intense emesis, as well as in cases with isoattenuating stones, magnetic resonance cholangiopancreatography (MRCP) can be utilized, as it distinguishes stones from fluid, visualizes the fistula with major precision, and does not require the use of oral contrast material. The disadvantage is the difficulty in interpretation as concernments and difficult to differentiate. Esophagogastroduodenoscopy (EGD) is another option, which advantages being the visualization of stone and simultaneous removal of stone with visualization, but this is only successful in the minority of cases and can be associated with further complications. In about 20% to 40% of total cases, the final diagnosis is established intra-operatively when a patient is undergoing laparotomy for small bowel obstruction of unknown origin. This applies in particular to the 15% to 25% of gallstones that are isoattenuating and not visible on CT scan.
Given the advanced age and extensive comorbidities of the typical patient with this syndrome, many have advocated for endoscopic or percutaneous approaches such as laser or extracorporeal shockwave lithotripsy initially. Approximately 91% of patients fail this procedure and require surgical treatment. The surgical options are the one-stage procedure (enterolithotomy to relieve bowel obstruction, cholecystectomy, and repair of chole-enteric fistula), the two-stage procedure (enterolithotomy and interval cholecystectomy) and enterolithotomy alone. The laparoscopic approach typically fails in approximately 50% of cases. Although the best method is still controversial, surgical management with enterolithotomy is the most common treatment, with only 5% of patients developing biliary symptoms and 10% requiring an unplanned reoperation. Supporters of this method believe that the spontaneous fistula closure occurs in more than 50% of cases, and that enterolithotomy alone has fewer complications.
Despite the fact that a large gallstone is the cause of the gastric outlet obstruction, a history of prior gallstone disease is only present in a few patients. Nevertheless, the condition should be considered in elderly patients who have a history of chronic cholecystitis and who present with repeated episodes of hematemesis or vomiting.