INTRODUCTION — Early morbidity and mortality rates that occur ≤30 days after the operation are generally low and vary with surgical approach as there are fewer complications and less mortality with the laparoscopic than with the open approach [1,2]. Most patients have been discharged from the hospital during this one-month interval after the operation [2]. As with any surgical procedure, the occurrence of an adverse intraoperative event (AIE) also increases the risk of a serious postoperative complication [3].

This topic will review the early (≤30 day) serious postoperative complications that can occur after hospital discharge of the more common bariatric surgical procedures, including laparoscopic Roux-en-Y gastric bypass (LRYGB) and open Roux-en-Y gastric bypass (ORYGB), laparoscopic adjustable gastric band (LAGB), laparoscopic sleeve gastrectomy (LSG), and biliopancreatic diversion with duodenal switch (BPD-DS).

A description of bariatric procedures, indications and preoperative management, and intraoperative and in-hospital complications are reviewed as separate topics.

●(See "Bariatric procedures for the management of severe obesity: Descriptions".)

●(See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

●(See "Bariatric operations: Perioperative morbidity and mortality".)

●(See "Laparoscopic Roux-en-Y gastric bypass".)

●(See "Laparoscopic sleeve gastrectomy".)

THIRTY-DAY POSTOPERATIVE MORBIDITY — Early morbidity and mortality data include the time period between hospital discharge through day 30 after the operation. Based upon the retrospective review of the Longitudinal Assessment of Bariatric Surgery (LABS) database that included 4776 bariatric surgery patients, the rate of failure to be discharged from the hospital within 30 days was 4.1 percent [2].

Serious complications that occur during the in-hospital admission can also occur after discharge, such as a leak, a pulmonary embolus, or a myocardial infarction. The overall morbidity rate for serious complications ranges from approximately 3.4 to 12 percent [2-13] and varies with operative procedure (eg, Roux-en-Y gastric bypass [RYGB], laparoscopic adjustable gastric band [LAGB]), operative approach (open versus laparoscopic), patient age, body mass index (BMI), and comorbid illnesses. Overall complication rates have decreased over time from 2005 to 2006 (4.6 percent) to 2013 (3.0 percent) [14]. (See "Bariatric operations: Perioperative morbidity and mortality".)

The type of operative procedure affects the morbidity rate [15]. For example, the morbidity associated with LAGB is less than is seen with laparoscopic Roux-en-Y gastric bypass (LRYGB). A one-year analysis of 4756 patients from the American College of Surgeons' National Surgical Quality Improvement Program (ACS NSQIP) database showed that LAGB carried a lower 30 day rate of major complications compared with LRYGB (1.0 versus 3.3 percent), fewer return visits to the operating room (0.9 versus 3.6 percent), and shorter postoperative stay (median one versus two days) [1].

Similarly, analysis of the ACS NSQIP database showed that patients who had an open Roux-en-Y gastric bypass (ORYGB) compared with an LRYGB had significantly higher morbidity (7.4 versus 3.4 percent), more return visits to the operating room (4.9 versus 3.6 percent), and longer postoperative length of stay (median three versus two days) than patients who had laparoscopic RYGB [1]. The biliopancreatic diversion with duodenal switch (BPD-DS) appears to be the riskiest procedure with the highest 30 day mortality of 1.2 percent and the one associated with the most complications and highest morbidity rates [5].

Types of complications

Leaks — Anastomotic leaks or staple line leaks are a dreaded complication after bariatric procedures. From an RYGB, they can happen at the gastrojejunal or jejunojejunal anastomosis at a rate of approximately 1.0 percent [16]. From a sleeve gastrectomy (SG), they can happen from the staple line at a rate of up to 7 percent, but generally the rate has decreased to around 1.5 percent [17]. From a BPD-DS, they can happen from the anastomoses or from the long stomach staple line at a rate of 5 percent [18].

More contemporary data from 133,478 patients who underwent laparoscopic sleeve gastrectomy (n = 92,495 [69.3 percent]) and LRYGB (n = 40,983 [30.7 percent]) were analyzed from the MBASQIP database in 2018 [19]. The overall leak rate was 0.7 percent (938 of 133,478). Laparoscopic sleeve gastrectomy was associated with a lower risk of leak (adjusted odds ratio [AOR] 0.52; 95% CI 0.44-0.61) compared with LRYGB. Factors associated with increased risk for leak were oxygen dependency (AOR 1.97), hypoalbuminemia (AOR 1.66), sleep apnea (AOR 1.52), hypertension (AOR 1.36), and diabetes (AOR 1.18).

Typically, leaks will occur within the first week after bariatric surgery. The most important aspect of treatment is early recognition. Patients who present with a persistent heart rate above 120 beats per minute and dyspnea are very concerning for a leak. Other symptoms include fevers, abdominal pain, oral intolerance, and a "feeling of doom." Computed tomography (CT) scans with oral contrast and fluoroscopy exams can help confirm the diagnosis, but negative studies should not preclude an operative exploration. Patient with sustained tachycardia above 120 beats per minute should at the very least be admitted to the hospital, fluid resuscitated, and closely observed for worsening tachycardia, the development of sepsis, or hemodynamic instability, all conditions that would prompt surgical exploration with possible intraoperative endoscopy to rule out the leak definitively.

For hemodynamically abnormal patients, an operative exploration should be done expeditiously. The tenets of the operation include primary repair or a buttressing with omentum, washout, extensive drainage, and feeding tube placement. This can be done laparoscopically. For hemodynamically normal patients who have a small contained leak, radiology-guided placement of drainage catheters or endoscopic placement of clips, fibrin glue, stents, or negative pressure suction have all been used with success [20]. (See "Gastrointestinal endoscopy in patients who have undergone bariatric surgery".)

Leaks from a sleeve gastrectomy generally take a longer time to close than leaks from other bariatric procedures. The sleeved stomach is a high-pressure system due to the presence of sphincters at both ends. The pressure may cause a leak to persist. Additionally, the leak may be caused by a stenosis in the sleeve, a kink in the sleeve's course, or a twist in the sleeve. Consequently, leaks may not close without alleviating the partial obstruction from these entities, which may ultimately require a reoperation [21].

Marginal ulcers — Marginal ulcers typically occur within 30 days after the RYGB operations at the gastrojejunal anastomosis (picture 1) [22] and at the gastroileal junction following a BPD-DS [23], despite bypass or removal of most of the acid-secreting cells of the stomach. The risk of a marginal ulcer following bariatric operations based upon a retrospective review of the Bariatric Outcomes Longitudinal Database (BOLD) was 1.2 percent [5]. However, in a prospective study of 81 patients undergoing an LRYGB, upper endoscopy at one month after surgery identified a marginal ulcer in 12 (12.3 percent) [22]. In comparison, marginal ulcers occurred late (17 months) in only 0.6 percent. In addition, based upon a retrospective review of 1300 obese patients undergoing BPD-DS, the incidence of a marginal ulcer following a BPD-DS was 0.3 percent [23] while the incidence of a marginal ulcer following a BPD only was 3 percent [24].

The clinical presentation of marginal ulcers includes melena, hematochezia, hematemesis, or pain and obstructive symptoms as the swollen mucosa can occlude the anastomosis to the small intestine [25]. Early ulceration most likely is related to ischemia, too large of a pouch, or undiagnosed Helicobacter pylori infection. (See "Bacteriology and epidemiology of Helicobacter pylori infection" and "Indications and diagnostic tests for Helicobacter pylori infection in adults".)

Risk factors for late presentation of a marginal ulcer include smoking, nonsteroidal anti-inflammatory drugs (NSAIDs), and gastrogastric fistula formation. Most surgeons will place their patients on a proton-pump inhibitor for 3 to 12 months after surgery to help prevent the occurrence of marginal ulcers. Lifetime avoidance of smoking and NSAIDs is advised in RYGB and BPD-DS patients. If NSAIDs are necessary, a short course and concomitant use of a proton pump inhibitor are advised. (See "Gastrointestinal endoscopy in patients who have undergone bariatric surgery" and "Proton pump inhibitors: Overview of use and adverse effects in the treatment of acid related disorders" and "Medical management of gastroesophageal reflux disease in adults".)

Stenosis — Stenosis occurs when the gastrojejunal anastomosis of an RYGB or gastroileal anastomosis of a BPD-DS becomes occluded secondary to tissue edema or a narrow anastomosis. Following a laparoscopic sleeve gastrectomy (LSG), stenosis can occur if the sleeve narrows, kinks, or twists. A retrospective review of 230 patients found that the risk of stenosis following an LRYGB, BPD-DS, or LSG is approximately 3.3, 1.2, and 3.5 percent, respectively [26].

The clinical presentation is consistent with an obstruction and includes nausea, vomiting, abdominal pain, and dysphagia. Endoscopic balloon dilation of the stenotic structures, including those resulting from an SG, is the first management option. [20]. (See "Gastrointestinal endoscopy in patients who have undergone bariatric surgery".)

Small bowel obstruction — A small bowel obstruction (SBO) can occur following any intra-abdominal procedure. SBO can occur from misconstruction during RYGB or BPD-DS operations, internal herniation, adhesion formation (in both open and laparoscopic procedures), or port site hernia, although uncommon within 30 days of surgery. Early SBO is usually caused by a technical error such as the failure to reapproximate the fascia from a port site or potential internal hernia sites.

In a prospective study that included 2126 patients undergoing LRYGB, SBO following bariatric procedures occurred in approximately 0.5 percent of patients [27]. Other retrospective reviews report a range of SBO in 0 to 8 percent of patients [28-30]. After an RYGB, an internal hernia can occur through the mesentery of the jejunojejunal anastomosis and posterior to the gastrojejunal anastomosis. If a retrocolic approach is used, an internal hernia can occur through the transverse mesocolon defect and through Petersen’s defect, which is the space between the transverse mesocolon and the Roux limb as it passes through the mesocolon [31].

The clinical presentation and management of a small bowel obstruction are reviewed elsewhere. (See "Etiologies, clinical manifestations, and diagnosis of mechanical small bowel obstruction in adults" and "Management of small bowel obstruction in adults".)

Nausea, vomiting, and poor oral intake — After bariatric surgery, it is not unusual for patients to experience some extent of nausea, vomiting, and mild food intolerance [32]. Generally, though, if patients can stay hydrated and tolerate a thin liquid diet, they will not need readmission or workup for the aforementioned causes of early morbidity. Patients with mild gastrointestinal symptoms are generally kept on a liquid diet for one to two weeks after the operation and slowly transition to more solid forms of food over the next one to two months. Surgical edema is typically the cause of these symptoms, which should be self-limited. Patients who continue to present with recurring or worsening symptoms should undergo further workup for more serious complications as discussed above.

Stomal obstruction — Acute stomal obstruction is an early complication that can occur in up to 14 percent of LAGB patients [11,33,34]. Obstruction is usually caused by inclusion of excess perigastric fat, use of a band of insufficient diameter for the thickness of the tissue, or significant tissue edema. Patients usually present with persistent nausea, vomiting, and inability to tolerate secretions or oral intake. The diagnosis is confirmed with an upper gastrointestinal series demonstrating no passage of contrast beyond the band.

Acute stomal obstruction due to edema can initially be treated conservatively with nasogastric tube decompression until the edema subsides, although a potential for aspiration pneumonia and gastric ischemia exists [35]. Persistent obstruction requires surgical revision or removal of the band. Meticulous removal of excess perigastric fat at the time of initial band placement may help prevent this complication [36]. The use of larger-diameter bands may also help to reduce the incidence of acute postoperative obstruction.

Venous thromboembolism/pulmonary embolism — The risk of a venous thromboembolism (VTE) or pulmonary embolus (PE) extends past the 30 day postoperative period. The overall risk of a VTE within 90 days after surgery was 0.42 percent; 27 percent occurred before discharge from the hospital and 73 percent of these events occurred after discharge, most within 30 days after surgery [37]. There is no clear benefit of long-term chemoprophylaxis to prevent VTEs [38].

Portal, splenic, and mesenteric vein thrombosis — Portomesenteric vein thrombosis is a rare complication of laparoscopic bariatric surgery, most commonly after LSG. The risk is about 0.4 percent, and it may lead to increased mortality. Patients typically present with abdominal pain, nausea, vomiting, fevers, tachycardia, and a leukocytosis. Diagnosis can be made by CT scan of the abdomen [39-41]. Therapy typically consists of anticoagulation therapy. (See "Laparoscopic sleeve gastrectomy", section on 'Portal vein thrombosis'.)

Pulmonary complications — Based upon the ACS NSQIP database of 32,889 bariatric patients, the overall 30 day risk of postoperative pneumonia or respiratory failure is 6.4 percent and accounts for 18.7 percent of all early postoperative complications [42].

Risk factors for early postoperative complications — A few studies have assessed specific risk factors for specific complications [8,43-47]. In a retrospective review of the Bariatric Outcomes Longitudinal Database (BOLD) that contained 73,921 bariatric surgical patients, the most common risk factors and the associated risks for a VTE included [37]:

●RYGB versus adjustable gastric banding (0.55 versus 0.16 percent)

●Open versus laparoscopic approach (1.54 versus 0.34 percent)

●Men versus women (hazard ratio [HR] 2.32, 95% CI 1.81-3.98)

●Black versus white race (HR 1.65, 95% CI 1.19-2.29)

●Previous VTE (HR 4.96, 95% CI 3.58-6.88)

●Inferior vena cava filter usage (HR 7.66, 95% CI 4.55-12.91)

●Lower extremity edema (HR 2.23, 95% CI 1.75-2.85)

●Pulmonary hypertension (HR 1.80, 95% CI 1.14-2.84)

Similarly, risk factors for pulmonary disease based upon the findings from the National Inpatient Sample database that included 304,515 patients included open procedures and comorbid illnesses that included heart failure, chronic renal failure, gastric bypass, peripheral vascular disease, males, patients older than 50 years, alcohol abusers, smokers, chronic lung disease, and diabetics [48]. Patients undergoing a revision bariatric procedure also have a high risk of morbidity.

Patients with sleep apnea and gastroesophageal reflux disease were 24 percent more likely to develop an anastomotic complication, such as leaks and stenosis, 24 percent more likely to develop sepsis, and 28 percent more likely to develop dumping syndrome [47]. (See "Postprandial (reactive) hypoglycemia".)

Laparotomy versus laparoscopy approaches — The ACS NSQIP database showed that patients who had undergone a laparotomy approach to an RYGB had significantly higher morbidity than those who underwent a laparoscopic one [1,14]. The patients who had undergone a laparotomy had higher rates of major complications (7.4 versus 3.4 percent), more return visits to the operating room (4.9 versus 3.6 percent), and longer postoperative length of stay (median three versus two days) than patients who had laparoscopic RYGB [1].

Type of procedure — The morbidity rate is also dependent upon the type of procedure performed [1,5,9,49-59].

The following retrospective studies illustrate these differences between select procedures:

●Adjustable gastric band versus RYGB − The morbidity associated with LAGB appears to be less than the laparoscopic RYGB. A one-year analysis of 4756 patients from the ACS NSQIP database showed that LAGB carried a lower 30 day rate of major complications than laparoscopic RYGB (1 versus 3.3 percent), fewer return visits to the operating room (0.9 versus 3.6 percent), and shorter postoperative stay (median one versus two days) [1]. However, there was no difference in the 30 day mortality between the two procedures.

●SG versus RYGB − SG was not associated with fewer major complications when compared with the RYGB procedure. In a review of 117 patients undergoing an RYGB procedure and 121 undergoing an SG procedure, patients undergoing an SG had similar rates of major complications compared with patients undergoing an RYGB (6 versus 9 percent) [49]. However, patients undergoing an SG had a lower rate of minor complications (7 versus 17 percent).

●Biliopancreatic diversion – The BPD-DS is associated with more complications than RYGB or SG. In a review of 507 patients undergoing a bariatric operation, patients undergoing BPD-DS (n = 59) were significantly more likely to develop postoperative complications compared with patients undergoing RYGB (n = 360) [9]. There was no difference in complication rates between patients undergoing RYGB and SG.

Risk reduction approaches

Venous thromboembolic prophylaxis — Prophylaxis against VTE following bariatric operations is discussed separately. (See "Bariatric operations: Perioperative morbidity and mortality", section on 'Venous thromboembolism'.)

Preoperative weight loss — The data are conflicting regarding the benefits of a 14 day preoperative very low calorie diet (VLCD) to reduce the risks of 30 day postoperative complications [60,61]. A multicenter randomized trial that included 298 morbidly obese patients found that patients treated with a preoperative VLCD had significantly fewer early postoperative complications compared with patients who had no dietary restriction (8 versus 18 percent) [60]. There was no difference in the rate of intraoperative complications. However, a systematic review of two randomized trials, five prospective studies, and 14 retrospective reviews that included 6686 patients found little evidence to support or refute the benefit of preoperative VLCD to reduce the risk of early postoperative complications [61].

Enhanced recovery after surgery protocol — Enhanced recovery after surgery (ERAS) protocols, also called fast-track protocols, are associated with shorter length of hospital stay and lower postoperative morbidity for patients undergoing colorectal surgery [62,63]. (See "Enhanced recovery after colorectal surgery".)

However, the effectiveness of ERAS in the clinical setting of bariatric surgery is less well defined. In a randomized trial that included 78 patients undergoing bariatric surgery, patients treated using ERAS protocols had a similar rate of complications compared with patients receiving standard care but had a significantly shorter duration of hospital stay (one versus two days, p <0.001) [64].

A feasibility study assessed the practicality and benefits of shortened preoperative fasts, intraoperative humidification, early mobilization and feeding, avoidance of fluid overload, incentive spirometry, and pharmacologic therapy with prokinetics and laxatives interventions on early hospital discharge. Based upon 226 patients, the rate of discharge on postoperative day 1 for patients undergoing a gastric banding, RYGB, or sleeve gastrectomy procedure was 37, 28, and 48 percent, respectively [65]. Thirty-day hospital readmission occurred in six (2.7 percent) patients. Applying an ERAS protocol was feasible, safe, and associated with low morbidity, acceptable length of stay, and low 30 day readmission rates. The presence of multiple medical comorbidities should not preclude use of an ERAS protocol within bariatric patients. (See 'Rehospitalization and reoperation rates' below.)

Many ERAS protocols have the added benefit of avoiding the use of narcotics for postoperative pain control [66,67].

MORTALITY — The overall 30 day postoperative mortality rate ranges from approximately 0.2 to 0.6 percent in most contemporary series [2,3,8,9,18,28,37,42,49,68-79]. This compares favorably with the hospital mortality of other frequently performed major surgical procedures, including hip replacement (0.3 percent), abdominal aneurysm repair (3.9 percent), craniotomy (10.7 percent), esophageal resection (9.1 percent), and pancreatic resection (8.3 percent) [73].

Predicting mortality — Risk assessment and stratification is important in the decision to perform a bariatric operation. A scoring system to predict mortality in patients undergoing gastric bypass procedures has been derived and then validated in a separate population [80-82]. Using body mass index (BMI), male gender, hypertension, pulmonary embolus risk, and age, patients were grouped into three risk categories: low (Class A), intermediate (Class B), and high (Class C). The mortality rate among the three risk classes was significant: Class A: 0.3 percent, Class B: 1.9 percent, and Class C: 7.6 percent.

Medical and technical risk factors — Mortality rates are higher for patients undergoing more complex operative procedures or those who sustain adverse intraoperative events or serious in-hospital complications (such as pulmonary embolism [PE] or acute respiratory failure [ARF]) as well as those with a BMI ≥50 kg/m², older age, and medical comorbidities [1,6,42,43,74,75,77,80,81,83-92]. In addition, based upon the data from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) Participant Use File (PUF), the mortality rate was greater for patients undergoing an open procedure compared with a laparoscopic procedure (0.79 versus 0.17 percent) [1].

For example, higher mortality rates were identified for patients undergoing the more complex biliopancreatic diversion with duodenal switch (BPD-DS) compared with adjustable gastric banding (AGB) (1.2 versus 0.3 percent) [6]; however, a retrospective review of 4756 identified an equivalent 30 day mortality rate for patients undergoing a laparoscopic Roux-en-Y gastric bypass (LRYGB) compared with laparoscopic adjustable gastric band (LAGB) (0.14 versus 0.09 percent) [1].

Higher mortality rates are also identified for patients with postoperative PE (7.1 percent) [37], pneumonia (4.3 percent) or respiratory failure (13.7 percent) [42], or sepsis (n = 6; 33 percent of all deaths) [77] with respect to those patients without such complications. In addition, comorbid illnesses (eg, diabetes, coronary interventions, dyspnea, cirrhosis) and complications of an anastomotic leak also increase the risk of postoperative mortality [42]. If not diagnosed in a timely fashion, the mortality rate from an anastomotic leak can be as high as 15 percent [93].

The most common causes of death varied with the series [42,77,83-86] but generally include PE, sepsis, complications of anastomotic leak, cardiac events, and small bowel obstruction [42,77,83-86]. PE is the most frequent cause of mortality in most studies.

A 2018 analysis of the Bariatric Outcomes Longitudinal Database (BOLD) reported that the 30 day and one-year mortality rates for LRYGB were 0.13 and 0.23 percent, respectively, and for laparoscopic sleeve gastrectomy (LSG) were 0.06 and 0.11 percent, respectively [94]. Complications associated with one-year mortality included the presence of 30 day leak (LRYGB: adjusted odds ratio [AOR] 25.4; LSG: AOR 35.8), 30 day PE (LRYGB: AOR 34.5; LSG: AOR 252), and 30 day hemorrhage (LRYGB: AOR 2.34).

A Swedish database study reported that the one-year cumulative mortality was 0.38 percent [95]. The main causes of death included cardiopulmonary complications (myocardial infarction [n = 14; 16 percent], PE [n = 12; 14 percent], sudden cardiac arrest [n = 11; 13 percent]) and anastomotic leak (n = 12; 14 percent).

Based upon retrospective reviews of United States (US) national databases and other series, the following examples illustrate specific risk factors for mortality:

●Male gender – Data from the National Inpatient Sample database on 304,515 patients showed that male gender (odds ratio 1.7), age >50 years (odds ratio 3.8), heart failure (odds ratio 9.5), peripheral vascular disease (odds ratio 7.4), chronic renal failure (odds ratio 2.7), and open surgery (odds ratio 5.5) were associated with greater mortality [87]. Ethnicity, hypertension, diabetes, liver disease, chronic lung disease, sleep apnea, and alcohol abuse had no significant association with mortality. These factors should be considered when counseling patients preoperatively.

Male gender is also a risk factor for mortality within the first year after surgery. In the Medicare study discussed below, men had higher rates of early death than women at 30 days (3.7 versus 1.5 percent), 90 days (4.8 versus 2.1 percent), and one year (7.5 versus 3.7 percent) [75]. Similar results have been reported in a large population-based study [89].

●Older age – Higher mortality rates have been reported in patients over the age of 65 years. A study of 16,155 Medicare beneficiaries (mean age, 47.7 years) who underwent bariatric procedures reported 30 day, 90 day, and one-year mortality rates of 2.0, 2.8, and 4.6 percent, respectively [75]. Mortality rates were significantly higher for those aged 65 and older compared with younger patients (4.8 versus 1.7 percent at 30 days, 6.9 versus 2.3 percent at 90 days, and 11.1 versus 3.9 percent at one year). Similar results were reported in a second study of a similar population [88]. This is also confirmed by the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database analysis of over 266,000 patients [96].

In the 65 and older population, the 30 day mortality rate (4.8 percent) was higher than has been described with coronary revascularization (approximately 2 percent) or hip replacement (approximately 1 percent).

●Excessive obesity – There are conflicting reports relating excessive (or super) obesity to postoperative mortality. In a retrospective review of 856 patients undergoing bariatric surgery, patients who died (n = 54) were more likely to be super obese (BMI ≥50 kg/m²) compared with patients who survived (30/54 patients [55.6 percent] versus 278/802 patients [34.7 percent], hazard ratio [HR] 1.8, 95% CI 1.01-3.09) [43].

However, in another retrospective review, BMI ≥60 kg/m² was not a risk factor for postoperative mortality. A review of 3692 patients undergoing a bariatric operation found that 291 super-obese patients had a similar in-hospital mortality rate compared with patients with a BMI <60 kg/m² (0.34 versus 0.12 percent) [44].  

●Comorbid illnesses – A diagnostic cost group (DCG) score is a risk adjustment measure that reflects the level of medical comorbidities and one-year mortality rates and predicts health expenditures in US veterans [90-92]. In the retrospective study previously described [43], DCG score ≥2 (higher than average expected expenditures) was significantly associated with an increased risk of death after bariatric surgery compared with a DCG score <2 (HR 3.4, 95% CI 1.8-6.5). Metabolic syndrome is associated with three times the mortality compared with patients who do not have metabolic syndrome [97,98]. Cirrhosis is also associated with an increased risk of mortality. Based upon the US Nationwide Inpatient Sample, patients without cirrhosis had significantly lower mortality rates compared with patients with compensated and decompensated cirrhosis (0.3 versus 0.9 versus 16.3 percent) [99].

●Poor functional status – Functional status is an underappreciated comorbidity of obesity as well as a predictor of postoperative complications. Functional status can be described as independent, partially dependent, and completely dependent. A totally dependent person needs assistance for all activities of daily living. A retrospective review of 44,408 bariatric surgery patients from the ACS NSQIP database from 2007 to 2009 found the overall mortality rate was 0.14 percent [100]. For patients with partially dependent preoperative function, the adjusted odds ratio (AOR) for 30 day mortality was increased 2.6-fold while totally dependent patients had a very high risk with an increased AOR of 27.6.

●Low-volume surgeons and hospitals – Increased mortality is associated with low surgeon and hospital volume of bariatric procedures. Both in-hospital and 30 day mortality are decreased when bariatric surgery is performed by surgeons and hospitals that perform more than 100 procedures a year [74,89]. For these reasons, volume is one of the criteria utilized by the American Society of Metabolic and Bariatric Surgery and the American College of Surgeons for the accreditation of bariatric center of excellence (COE) programs. Currently, a minimum of 25 stapling cases per year is required to be certified as a comprehensive bariatric COE by the governing bodies [101].

●Surgical approach – Improvements in perioperative mortality have been documented with the introduction of laparoscopic and robot-assisted techniques [1,102-104]. Most series report a lower mortality rate with a laparoscopic versus an open approach, although mortality rates for both are less than 1 percent [1]. The increased mortality with the open approach may be related to technical challenges that made the patient ineligible for the laparoscopic approach, adverse intraoperative events, and/or laparoscopic expertise of the surgeon [105]. There is no difference between a laparoscopic and a robot-assisted laparoscopic approach in terms of morbidity and mortality.

REHOSPITALIZATION AND REOPERATION RATES — Complications from bariatric operations may lead to rehospitalization and reoperation. Early postoperative complications, including risk of surgical site infection and/or fascial dehiscence, pulmonary infections, length of hospital admission, and rate of hospital readmission, are higher with an open intra-abdominal procedure and are associated with an increased rate of readmission [1,4,5,106,107].

Given the large numbers of bariatric procedures performed, rehospitalization and reoperation for bariatric surgery represent significant costs for hospitals and insurance companies [70,108,109]. In a report from the American Society for Metabolic and Bariatric Center of Excellence facilities that included 235 accredited hospitals and 66,339 procedures, the readmission rate was 5 percent [110]. Another study based upon data from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP; 2005 to 2013) reported an identical readmission rate [14].

The rate of reoperation within 30 days of the initial procedure ranges from 0.7 to 7.6 percent [5,6,8,28,105,110]. The reoperation rates tend to be higher with more complicated procedures, such as biliopancreatic diversion with duodenal switch (BPD-DS) versus Roux-en-Y gastric bypass (RYGB; 3.3 versus 1.5 percent) [5], and in the laparoscopic versus the open approach (7.6 versus 6.6 percent) [6].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bariatric surgery".)

SUMMARY AND RECOMMENDATIONS

●The overall morbidity rate for serious complications ranges from approximately 3.4 to 12 percent and varies based upon the procedure performed. (See 'Thirty-day postoperative morbidity' above.)

●Serious postoperative complications that can occur within 30 days after bariatric surgery include leaks, marginal ulcers, stenosis, and venous thromboembolism. (See 'Types of complications' above.)

●Overall 30 day mortality for bariatric surgical procedures is less than 1 percent. (See 'Mortality' above.)

●The most common causes of early mortality are pulmonary emboli and complications related to leaks. (See 'Medical and technical risk factors' above.)

●Early postoperative complications, including risk of surgical site infection and/or fascial dehiscence, pulmonary infections, length of hospital admission, and rate of hospital readmission, are higher with an open intra-abdominal procedure and are associated with an increased rate of readmission. (See 'Rehospitalization and reoperation rates' above.)