The two sites of anastomoses (gastrojejunostomy and jejunojejunostomy) may serve as a potential source of complications. Anastomotic leak risks range from 0.8 to 6 %, with most generally occurring within 1 week of surgery, but may occur up to 1 month postoperatively. The patient presentation may include signs such as low-grade fevers, respiratory distress and/or tachycardia (greater than 120 beats per minute). If a leak is suspected clinically, even if imaging is negative, emergent surgical exploration is indicated, and is often done laparoscopically. To test for a possible leak intraoperatively, methylene blue or endoscopy may be utilized. For evaluation with the dye test, methylene blue with saline is injected via a nasogastric tube while a bowel clamp is placed distal to the gastrojejunostomy. To evaluate endoscopically, saline is used to submerge the gastrojejunostomy while the roux-limb is clamped and the pouch is insufflated via the endoscope. Air bubbles present in the saline around the pouch may indicate the presence of a leak. Treatment for an anastomotic leak includes drainage, broad-spectrum antibiotic coverage and identification/repair of the defect when feasible. A gastric tube may be placed for feeding or intravenous feedings may be used.

Stomal stenosis is a stricture that may form at the gastrojejunal anastomosis. Incidence of stomal stenosis after RGYBP is reported to be between 3.1 and 15.7 %. The etiology of stenosis may be related to the method used for anastomosis, with the greatest risk seen in the use of a 21 mm circular staple, followed in order by a 25 mm circular stapler, linear stapler, and hand-sewn anastomosis [2]. Patients present 1–2 months postoperatively with nausea, vomiting, dysphagia, and/or gastroesophageal reflux, with ultimate progression of intolerance of oral intake. Diagnosis is made by endoscopy or upper GI series. Treatment is endoscopic dilation as the preferred and less invasive option. A therapeutic endoscope is inserted through the gastrojejunostomy along with a balloon dilator which is pneumatically insufflated based on the stoma size. The complication rate is about 3 %, and repeated dilation may be required for some patients. Surgical revision is reserved for patients who have persistent stenosis despite repeated endoscopic dilations .

Marginal ulcers are mucosal erosions that occur at the gastrojejunal anastomosis, most commonly on the jejunal side. The ulcers typically occur when the gastric remnant is stapled but not divided. The incidence is reported to be between 0.6 and 16 %. Possible etiologies of marginal ulcers include nonsteroidal anti-inflammatory (NSAID) drug use, Helicobacter pylori (H. pylori) infection, smoking, poor tissue perfusion secondary to excess tension or ischemia at the anastomosis, increased exposure to acid in the gastric pouch due to gastrogastric fistula formation, and presence of foreign material (suture or staples). Patient presentation includes nausea, pain, with possible bleeding and/or perforation. Diagnosis is made by upper endoscopy. Initial management includes medical treatment with gastric acid suppression (proton pump inhibitors) with or without sucralfate. Patients should be strongly encouraged to stop NSAID use and smoking. Patients with H. pylori colonization should be treated with triple therapy (proton pump inhibitor, clarithromycin and amoxicillin).

Cholelithiasis may develop in up to 38 % of patients undergoing gastric bypass surgery, and up to 41 % of these patients become symptomatic. Rapid loss of weight can contribute to the formation of gallstones by increasing the lithogenicity of bile. This risk can be significantly reduced to 2 % when patients are postoperatively treated with a 6 month course of ursodeoxycholic acid [3]. Unfortunately compliance with ursodeoxycholic acid prophylaxis may be poor due to gastrointestinal side effects of the medication. Symptomatic patients should be evaluated preoperatively or intraoperatively for cholelithiasis and should have a cholecystectomy performed at the time of gastric bypass if gallstones are present. Asymptomatic patients may be managed expectantly as a minority will come to cholecystectomy during follow-up.

Dumping syndrome is a well-known physiologic phenomenon associated with gastric bypass, as it occurs in procedures that involve partial or complete gastrectomy. Dumping typically occurs when patients ingest high levels of simple carbohydrates. Hormones thought to be involved in this mechanism include enteroglucagon, vasoactive intestinal peptide (VIP), peptide YY (PYY), pancreatic polypeptide, and neurotensin. Dumping may be divided into early and late phenomena. Early dumping occurs within 15–30 min of ingestion and is due to rapid gastric emptying. The high osmolality of the food causes rapid fluid shifts from the plasma into the bowel, which leads to hypotension and reflex sympathetic nervous system activation. Patients will present with symptoms of colicky abdominal pain, diarrhea, nausea, and tachycardia. Late dumping occurs 1–3 h after meal ingestion, and presents with symptoms of hypoglycemia (dizziness, fatigue, diaphoresis, weakness, confusion). Rapid gastric emptying leads to a high glucose concentration, which is rapidly absorbed and triggers insulin secretion, leading to the signs and symptoms of hypoglycemia. Sigstad’s scoring system may be used for diagnosing dumping syndrome, where a score greater than seven is suggestive of dumping, and a score less than four suggests other diagnoses. To avoid dumping, patients are advised to avoid foods high in simple carbohydrates, and are encouraged to eat diets with high fiber content, complex carbohydrates, and high protein content. Furthermore, patients are instructed to eat small, frequent meals (up to six per day), and to avoid drinking with meals or in the first 2 h after a meal. If these first line measures fail, somatostatin analogue use may be considered, which are administered subcutaneously three times a day or intramuscularly once every 2–4 weeks. Although dumping is an unpleasant consequence that patients may have to withstand, the condition actually aids the patient in adhering to the prescribed dietary restrictions by acting as negative feedback to the ingestion of sugar [4].

Changes in nutritional needs are important to be considered when managing a post-gastric bypass patient. Patients are advised to obtain a significant amount of their daily calories from protein (50–60 g per day). Daily supplementation also includes 500 μg of vitamin B12, 1200 mg of calcium, and a multivitamin tablet. Women who menstruate are also asked to take 650 mg of ferrous sulfate daily. Serum levels of these supplements should be checked during regular clinic appointments [5].