Although immediate postoperative complication rates in bariatric surgery are relatively low, they are potentially lethal. In the morbidly obese person, symptoms of a complication may be subtle and extremely difficult to diagnose often yielding a delay in treatment. The physician caring for these patients should be aware of the potential complications and their presentation, however subtle they may be. Recent litigation would indicate that even surgeons who do not perform bariatric surgery are required to understand and be aware of the complications of bariatric surgery if they see surgical consults involving bariatric patients in the emergent setting [7, 8].

For any operation involving suture or staple lines (i.e., RYGBP, BPD, SG), one worries about leakage from a suture line. Leak from a suture line can produce a collection of findings that are associated with sepsis. Mental changes (agitation, disorientation), sustained tachycardia (p  >  120/min), fever, and renal failure are all manifestations of a suture line leak. These symptoms often occur without overt signs of peritonitis secondary to the difficulty of the abdominal exam in the morbidly obese [9]. The patient often presents with only one or two of these manifestations, so the physician must have a high index of ­suspicion. When recognized early and treated promptly, the patient usually survives with little morbidity. If diagnosis is delayed until the patient becomes overtly septic (i.e., hypotensive, in respiratory and renal failure), the prognosis is much worse, and in some instances will lead to death. If one suspects a suture line leak and the patient is stable, the leak can be confirmed or excluded by computed tomography (CT) scan with oral contrast. Anastomotic breaches may also be investigated with an endoscopic approach. If the leak is noted at the time of endoscopy, there have been numerous reports of covered metal stents across the leak with initiation of oral nutrition leading to closure of the leak [10–12]. This study has been shown to be effective in up to 81% of patients (17 of 21) [13]. Recent studies have shown leaks with fistualization can also be treated endoscopically [14].

If the surgeon is relatively sure that a leak is present and the patient is unstable, the patient should be taken to the operating room for exploratory laparoscopy or laparotomy. Commonly, intraoperative endoscopy is helpful in finding the location of small areas of leak from the staple lines. Operative treatment of the leak consists of irrigation, reinforcement of the suture line, and wide drainage [9, 15, 16]. With this treatment, the leak often stops or an enterocutaneous fistula occurs along the drain tract. If the fistula is resulting from a small leak, it will commonly close with conservative management. With larger leaks, a secondary surgery will be required for closure several months later. Attempting to do major reconstructive surgery in the face of a leak and infection is fraught with complications and results in anastomotic failure commonly [9]. While surgery with drainage is the mainstay of therapy, their stable patients can be managed non-operatively as long as adequate drainage can be assured.

Fortunately, leakage from a suture or staple line occurs in less than 2% of patients undergoing a primary bariatric procedure. Again, the patient’s obesity and recent surgery makes the abdominal exam much less reliable in diagnosing postoperative leaks. Therefore, the surgeon or emergency department physician must have a high level of suspicion and rely on evaluating multiple criteria (e.g., pulse rate, respiratory status, temperature, white blood cell count, etc.), which could help determine evidence of leak.

Other acute complications in bariatric surgery populations that occur in the immediate postoperative period are similar to those non-obese patients undergoing abdominal major surgery with the exception of wound infection, which occurs in 20–30% of obese patients undergoing an open (non-laparoscopic) bariatric procedure [17]. Wound infections should be treated as any other post-op wound infections with the caveat that the risk of deep fluid/purulent collections that are inadequately drained are more common than in the lower body mass index (BMI) patient [18]. Bariatric surgeons are concerned about the potential for post-op thrombophlebitis and pulmonary embolus in these patients; and prophylactic low molecular weight heparin, as well as anti-embolus stockings, is recommended in the postoperative period. The reported incidence of clinical pulmonary embolus is low (0.3–0.6%) and compares with the incidence in non-obese patients [19]. Pulmonary embolus often presents as persistent O₂ desaturation as measured by pulse oximeter or arterial blood gas. When suspected, pulmonary embolus (PE) should be excluded with a pulmonary angio CT scan, and if PE is present, the patient should be fully anticoagulated for 6 weeks.

Most bariatric patients are thoroughly assessed for coronary artery and pulmonary disease preoperatively; and consequently, the incidence of postoperative respiratory failure, heart failure, or pneumonia is extremely low [20].

Lap bands have the potential to develop a unique set of postoperative complications, including band slippage, unrecognized perforation of the esophagus, infection, and erosion into the stomach. Bands can “slip” in the acute setting following surgery or long after the initial procedure. The slippage occurs when the band “slips” more distal along the greater or lesser curvature and the distal stomach herniates through the band. This complication is usually manifested by the inability to tolerate anything by mouth and rather severe abdominal pain [21]. The diagnosis is made by a contrast swallow. Water soluble contrast is suggested as the first attempt; and if no leaks are present, barium can be used to better define the anatomy [22]. A slipped band should be acutely repositioned surgically; this can usually be done laparoscopically. If adequately skilled bariatric surgical support is unavailable to reposition the band should be removed. This procedure can be usually be done by freeing up the band cautiously with cautery then when adequately exposed just cut the band and remove. If concern for gastric injury exists, the band removal can be combined with endoscopy to evaluate for small leaks. Allowing the slipped portion of the stomach to remain for prolonged periods will often result in ischemia and full thickness necrosis of the herniated segment of stomach [23]. (See “Band Slippage” in next section.)

Long-term complications in bariatric patients fall into three groups: post-op adhesions, metabolic complications, and complications which are procedure specific.

As with any intra-abdominal surgery, postoperative adhesions causing bowel obstruction are a risk when bariatric procedures are performed. Most bariatric procedures are now performed laparoscopically, and there are minimal adhesions following laparoscopic procedures.

Postoperative incisional hernias are very common (up to 30%) following open bariatric procedures [24, 25]. Trocar site hernias following laparoscopic bariatric procedures are reported to occur between 0 and 5.2% of the time [26, 27]. Patient risk factors for trocar site hernias are older age and higher body mass index. Technical risk factors for trocar site hernias are related to the design and size of trocars [26].

Both biliopancreatic diversion with or without duodenal switch and gastric bypass are procedures that employ Roux-en-Y reconstruction; and with this reconstruction, the patients can develop internal hernias. Three types of internal hernias make up the majority of these herniations following bariatric procedures. These include (1) hernia through the transverse mesocolon into the lesser sac, (2) internal rotation of the biliary limb under the Roux-en-Y limb (often called Petersen Hernia), and (3) herniation through the divided leaves of the mesentery where the jejunojejunostomy was performed [4, 28]. The usual presentation for internal hernias is quite variable. The presentation can be from subtle vague intermittent cramping epigastric pain to severe unrelenting constant abdominal pain making this diagnosis very difficult. It may present as closed loop bowel obstruction with ischemia or necrosis of the loop [29]. One must remember also that with the Roux-en-Y reconstruction, the biliary limb can become obstructed without having the alimentary limb obstructed; and thus a standard upper gastrointestinal (GI) series with small bowel follow-through may appear normal when the biliary limb is obstructed. CT scan is the best test to diagnose obstruction of the biliary limb and internal hernia in general [29, 30]. When a patient presents with post-gastric bypass abdominal pain or has abdominal pain from biliary pancreatic diversion, a CT scan should be performed to help rule out obstruction of the biliary limb; the scan will sometimes diagnose internal hernias. If the CT is negative, laparoscopy or laparotomy may be required to rule out internal hernia.

Roux-en-Y reconstruction consists of anastomosing jejunum to gastric pouch (in RYGBP) or duodenum (in BPD). This reconstruction is ulcerogenic, as the jejunum is without buffering components from pancreatic and biliary secretions, so marginal ulcers can occur after these two procedures [31, 32]. If the ulceration occurs on the jejunal side, it is most likely secondary to acid exposure and will most likely respond to treatment with H₂ receptor antagonists or proton pump inhibitors. However, if the ulcer occurs on the gastric pouch side of the anastomosis, it is most likely due to ischemia in that part of the pouch and may need resection. The majority of these patients will respond to treatment with proton pump inhibitors (PPI), which confirms that unbuffered acidity is the major cause of these lesions. The incidence of anastomotic ulcers varies from 3 to 12%. These ulcers may be under diagnosed since a substantial (>5%) number may be asymptomatic. The majority of these ulcers occur acutely, that is within 1 year from surgery [33, 34]. The development of marginal ulcers is higher in patients who had history of H. pylori infections even when eradication has been attempted [35]. Marginal ulcer formation is also common source of blood loss. Most bleeds can be managed conservatively with proton pump inhibitors (PPI) via IV or infusion and blood transfusion; however, if the bleeding remains persistent, endoscopic evaluation is warranted. When source of bleeding is noted, hemostasis should be achieved with the use of endoscopic clips over cautery or epinephrine injection as the clips do not produce additional tissue injury [36]. Although most marginal ulcerations heal with PPI therapy, there will be some that are recalcitrant to PPI therapy or that result in an anastomotic stricture not amenable to dilatation. These ulcers are treated with resection of the gastrojejunostomy with formation of a new gastrojejunostomy [37].

Anastomotic strictures can be secondary to technical problems constructing the anastomosis, chronic inflammation of the tissue around the anastomosis, an ulcer at the anastomosis, or ischemia. Strictures are primarily treated with PPIs and balloon dilation up to 15–18 mm. This has been shown to have a success rate of up to 93% in symptom resolution and subsequent resumption in weight loss [38]. It is often necessary to dilate multiple times, but if the stricture recurs following the third dilatation, it is usually an indication for elective resection and making a new anastomosis. Like marginal ulcers, strictures occur rather acutely following surgery, and it is unusual to see a new stricture forming after 1 year. Anastomotic strictures following bariatric surgery occur about 3% of the time, and it is often difficult to determine the exact etiology (i.e., technical versus ulcer or ischemia [39]). The symptoms produced by marginal ulcers or anastomotic strictures are chronic epigastric pain and often symptoms of gastric outlet obstruction. The diagnosis is made endoscopically, and the treatment is proton pump inhibitors at least initially [40].

Patients following Roux-en-Y gastric bypass are also known to have a higher incidence of intussusception of small intestine [41, 42]. When a patient who has had a Roux-en-Y gastric bypass presents with bowel obstruction and epigastric pain, one must consider intussusception as a possible cause. The bloody or “currant jelly” stools often seen in ileocolic intussusception is not commonly seen in intussusception following gastric bypass surgery [43].

Surgeons and emergency department (ED) physicians are often presented with a patient who has had RYGH or BPD who presents with abdominal pain or symptoms suggestive of bowel obstruction; one must consider not only adhesions as the cause, but also internal hernia and intussusception. In someone presents with epigastric pain or occult hemorrhage and possible symptoms of gastric outlet obstruction, marginal ulcer or stricture is a probable diagnosis.

Those patients with LAB have minimal to no problems with adhesions or internal hernias since their anatomy has not been altered. Their problems are related to the band and its attachments (i.e., tubing and reservoir). These problems are principally slippage of the band, erosion of the band, infection of the port site, and malfunction of the insufflation system (leakage from the port, tubing, or the balloon on the inside of the band [44–46]).

Symptoms of slippage are often manifested by symptoms of gastric outlet obstruction; that is, early satiety, nausea, and vomiting. This slippage occurs when the posterior and greater curvature aspects of the stomach herniate through the band, placing a significantly greater amount of stomach on the proximal or cephalad side of the band. Slippage can occur acutely or gradually. The diagnosis is best made with an upper GI (UGI) series, which will demonstrate the herniated stomach with limited or no passage of contrast beyond the band [22]. A plain film of the abdomen may show the band at an inappropriate angle or tilt [22]. When this problem occurs acutely, it is an emergency and should be treated promptly because the herniated stomach may be at risk for ischemia and perforation [22]. Repositioning of the band with reduction of the hernia can often be done; however, occasionally, it is necessary to remove the band. These procedures can virtually always be performed laparoscopically unless it is associated with band erosion [22].

Band erosion occurs when the band erodes through part or all of the gastric wall. This process occurs gradually and most commonly does not produce peritonitis from free leakage of gastric content into the peritoneal cavity [47]. The erosion may be asymptomatic and manifest by weight gain, as the constrictive effect of the band can be lost [47]. Another common manifestation of transmural band erosion is infection of the port site on the abdominal wall. As the contamination from gastric contents seeds the exposed gastric band, it forms a biofilm containing viable bacteria along the length of the tubing to the port [45, 48]. Upper GI hemorrhage, often acute and severe, can also occur secondary to band erosion [49, 50]. When band erosion is suspected for any of these symptoms, endoscopy should be performed, and a segment of the band will most often be seen on the luminal side of the stomach. If on plain X-ray of the abdomen the band is unusually angled, this also would suggest erosion.

CT is very helpful in making diagnoses of the more subtle band erosions. It will usually show the change in angulation and often show air outside the lumen of the stomach at the site of the band erosion [51].

In virtually all cases of transmural erosion, the band should be removed because it has the potential to produce infectious complications (i.e., infection of the extra-gastric parts of the band and local abscesses and hemorrhage) and because it usually loses its effectiveness in weight loss. Eroded bands can sometimes be removed endoscopically when the buckle has eroded into the stomach [52, 53]. They are most often removed laparoscopically and can in some cases be removed endoscopically [54]. Following removal the surgeon must insure that no unsecured or unrecognized defects in the gastric wall remain. This is done by combining endoscopy with air insufflation watching for leaks. Once removed and leaks are ruled out, the patient usually can undergo a subsequent bariatric procedure such as sleeve gastrectomy or gastric bypass.

Rapid weight loss that occurs following bariatric procedures leads to gallstone formation in up to 50% of patients [55]; however, only 10% will develop symptomatic gallstones, and these patients can be treated with cholecystectomy [56, 57]. Treatment with Ursodiol for 6 months postoperatively will lower the incidence of gallstones by as much as 50% [58]; therefore, the most common algorithm in performing bariatric surgery is to not perform cholecystectomy in the patient who is asymptomatic at the time of his or her bariatric procedure and to prophylactically treat with Ursodiol for 6 months postoperatively. However, these patients are at risk to develop cholecystitis in the future and should have cholecystectomy when and if they become symptomatic. To evaluate a symptomatic patient for the presence of stones magnetic resonance imaging in the form of magnetic resonance cholangiopancreatography (MRCP) or computed tomography is preferred to ultrasound because body fat can distort imaging leading to missed diagnosis [59, 60]. Proven gallstones via imaging should still be approached with endoscopy. Given the complex postsurgical anatomy Laparoscopic-assisted and enteroscopy with either balloon or rotational device have been used to achieve stone extraction prior to cholecystectomy [61].

Restrictive and malabsorptive bariatric surgery significantly alters anatomical space and digestive physiology commonly prompting certain nutritional deficiencies and metabolic complications. Globally in bariatric surgery, the most common nutritional deficits encountered are iron, protein, calcium, vitamin B12, and vitamin D deficiencies. Complications after the restrictive/malabsorptive (RYGPB) and malabsorptive (BPD, BPD-DS) procedures contribute to the majority of observed short-term and long-term metabolic imbalances and overt deficiencies (Table 33.2). More specific nutritional complications are observed after restrictive procedures (banding); however, these deficits are much less common and usually related to changes in dietary patterns, food choices and noncompliance with the post-op nutritional supplement recommendations.