Gastrointestinal Complications of Obesity Surgery

John E. Pandolfino, MD; Brintha Krishnamoorthy, BS; Thomas J. Lee, MD

In This Article

Gastrointestinal Complications of Bariatric Surgery

Complications of bariatric surgery can be separated into "true" complications associated with the operation and "side effects" associated with the alteration in the upper gastrointestinal anatomy ( Table 1 ). The perioperative mortality of bariatric surgery is less than 1%[2,8] and is usually associated with anastomotic leaks with peritonitis (75%) or pulmonary embolism (25%).[2] Symptoms of an anastomotic leak can be overt with frank peritoneal signs or vague, with symptoms of mild abdominal pain, shoulder pain, back pain, unexplained tachycardia, or alteration in urination and bowel frequency. Given the devastating outcome of anastomotic leaks, there should be a low threshold for evaluation with water-soluble contrast agents and surgical exploration. Another early complication of gastric bypass surgery is acute gastric distention secondary to edema and obstruction at the enteroenterostomy. This complication may lead to staple line dehiscence or gastroenterostomic leaks. Acute gastric distention can be treated with radiographic-guided percutaneous gastrostomy or reoperation with tube gastrostomy.

Given the alteration in the upper gastrointestinal anatomy, certain side effects of bariatric surgery can be expected and ameliorated through patient education and postoperative treatment. In addition, patients with gastric bypass surgery should also be monitored for nutritional deficiencies and should take a multivitamin containing B-12 and folate, along with a calcium supplement.[2] Many patients experience symptoms of iron deficiency and anemia; these are potentially serious problems after gastric bypass, particularly in women who are menstruating. Combined with blood loss during menses, duodenal bypass and surgery-induced iron malabsorption make these women particularly susceptible to iron-deficiency anemia. Prophylactic oral iron supplementation is recommended for these patients.[33]

Nausea and Vomiting

Nausea and vomiting are the most common complaints after bariatric surgery, and they are typically associated with inappropriate diet and noncompliance with a gastroplasty diet (ie, eat undisturbed, chew meticulously, never drink with meals, and wait 2 hours before drinking after solid food is consumed). If these symptoms are associated with epigastric pain, significant dehydration, or not explained by dietary indiscretions, an alternative diagnosis must be explored. One of the most common complications causing nausea and vomiting in gastric bypass patients is anastomotic ulcers, with and without stomal stenosis. Ulceration or stenosis at the gastrojejunostomy of the gastric bypass has a reported incidence of 3% to 20% (Figure 5 A,B).[8,15,34] Although no unifying explanation for the etiology of anastomotic ulcers exists, most experts agree that the pathogenesis is likely multifactorial. These ulcers are thought to be due to a combination of preserved acid secretion in the pouch, tension from the Roux limb, ischemia from the operation, nonsteroidal anti-inflammatory drug (NSAID) use, and perhaps Helicobacter pylori infection.[35] Evidence suggests that little acid is secreted in the gastric bypass pouch; however, staple line dehiscence may lead to excessive acid bathing of the anastomosis. Treatment for both marginal ulcers and stomal ulcers should include avoidance of NSAIDs, antisecretory therapy with proton-pump inhibitors, and/or sucralfate. In addition, H pylori infection should be identified and treated, if present.

Figure 5.

Anastomotic ulcers: (A) gastric and (B) jejunal or marginal ulcer.

Stomal stenosis after gastric bypass may respond to endoscopic dilation with through-the-scope balloon dilators and, thus, may obviate the need for surgical revision.[36] Patients with restrictive procedures, such as VBG, may also develop nausea and vomiting secondary to stomal stenosis, erosion of the restrictive band or ring, and increased gastroesophageal reflux. Treatment is dependent on the etiology, and it is unlikely that these patients will respond to balloon dilation secondary to the noncompliant ring or band. Severe gastroesophageal reflux disease may also be associated with VBG and, if present, may require proton-pump inhibitor therapy or conversion to a gastric bypass.

Another cause of mechanical obstruction in gastric bypass patients is internal hernia. This may occur where the Roux limb passes through the transverse mesocolon or at the mesenteric defect at the jejunojejunostomy. This problem is extremely difficult to diagnose because symptoms are nonspecific (cramping, periumbilical pain with or without nausea, and vomiting), and diagnostic radiographic studies can be normal.[37] If symptoms persist or become severe, surgical exploration is indicated to rule out internal hernia.


In addition to the obstructive complications, patients may also develop symptoms related to increased transit of ingested food directly into the small bowel ("dumping syndrome"). Symptoms related to dumping syndrome are increased with food containing a high sugar content and high osmotic activity. Patients may present with symptoms of nausea, bloating, abdominal pain, and lightheadedness. These symptoms generally improve with fasting and are a deterrent to overeating. Diarrhea is another component of dumping syndrome that will also improve with fasting. If a patient has greater than 3 watery stools per day despite fasting and dietary restriction, stool studies should be obtained. Because gastric bypass patients may be predisposed to bacterial overgrowth and the blind loop syndrome, empiric antibiotics should be considered in patients who show no improvement with fasting in the context of negative stool studies.

Gastrointestinal Bleeding

Gastrointestinal bleeding is an uncommon complication of bariatric surgery.[38,39] In general, gastrointestinal bleeding in patients with VBG or gastric bypass should be evaluated similarly to how one would evaluate patients without surgery. However, anatomic considerations pose both diagnostic and therapeutic dilemmas in patients with gastric bypass. Upper gastrointestinal bleeding in patients who have undergone gastric bypass surgery may occur in the esophagus, gastric pouch, and Roux limb just distal to the anastomosis. Fortunately, these areas are readily accessible to standard upper endoscopy and therapy. Although present in up to 20% of patients after gastric bypass, anastomotic ulceration is a rare cause of bleeding and is typically associated with concomitant NSAID use. Whether H pylori infection is an important risk factor for anastomotic ulceration is somewhat controversial. However, given the increased lifetime risk for peptic ulceration, it is not unreasonable to test patients preoperatively and institute treatment if they are H pylori-positive to avoid future complications.

The distal stomach and proximal duodenum may not be accessible to endoscopy -- but bleeding from these areas is rare because of low-acid secretory states secondary to vagal interruption, lack of antral distention, and restricted contact with food. Patients are still susceptible to NSAID-related complications and should avoid these medications if at all possible. If bleeding from the distal stomach or proximal small bowel is suspected, a pediatric colonoscope or enteroscope may be used to evaluate the area. In addition, interventional angiography may be able to both locate and treat bleeding lesions in this area. Performance of colonoscopy is unchanged in patients who have undergone obesity surgery -- however, care should be given to the preparation because these individuals are unable to tolerate large volumes orally.[36]


Obesity and rapid weight loss are known risk factors for gallstone formation, and thus, it is no surprise that approximately one third of patients may develop gallstones after bariatric surgery. Furthermore, 10% to 15% of all patients will require cholecystectomy for complaints related to gallstones.[40,41,42,43,44] Some centers routinely perform cholecystectomies with bariatric procedures to prevent complications of cholelithiasis, whereas other centers choose to administer ursodiol as prophylaxis for 6 months postoperatively. Two controlled trials[40,45] demonstrated the efficacy of 6 months of ursodiol therapy in decreasing the incidence of gallstone formation. Cholelithiasis was detected in 22% to 32% of controls vs in 2% to 3% of treated patients at 6-12 months.[40,45] Clinicians against prophylactic cholecystectomy suggest that the operation may increase the overall operative time and length of hospital stay and that a cholecystectomy may be easier to perform after weight loss has occurred.[46]


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