Complications of Bariatric (Weight Loss) Surgery

Overall Risk Profile

• Perioperative mortality: <0.5% overall (LAGB 0.06%, LRYGB 0.1–0.3%, BPD/DS ~1.1%)
• Overall complication rate: 4%–25% depending on procedure and patient factors
• Major adverse outcome rate at 30 days (LABS Study): 4.1% (composite of death, VTE, reintervention, or prolonged hospitalization)

I. Early / Perioperative Complications (Shared by All Procedures)

II. Procedure-Specific Complications

A. Roux-en-Y Gastric Bypass (LRYGB)

• Anastomotic leak from gastrojejunostomy (most common and most dangerous) or jejunojejunostomy; rate <1.0% with modern technique
• Marginal ulcer at the gastrojejunal anastomosis — related to smoking, NSAIDs, H. pylori, or ischemia
• Dumping syndrome — early (osmotic) or late (reactive hypoglycemia); common and can be disabling; a 2023 systematic review confirms its significant role in weight reduction but also as a morbidity driver
• Internal hernia — through Petersen's space or mesenteric defect; presents as intermittent small bowel obstruction; risk persists lifelong
• Anastomotic stricture at the gastrojejunostomy — treated with endoscopic dilation
• Gastrogastric fistula — abnormal communication between the gastric pouch and remnant
• Nutritional deficiencies (see below) — iron, B12, folate, calcium, thiamine

B. Sleeve Gastrectomy (LSG)

• Staple-line leak (~0.3–0.5%): most often at the gastroesophageal junction or angle of His; early leaks (within 48 hrs) are due to stapler misfire; late leaks (1–4 weeks) due to ischemia and distal stenosis
• Gastric stenosis / stricture (<1%): usually at the incisura angularis; presents as obstructive symptoms; managed with serial endoscopic dilation or conversion to RYGB
• GERD / reflux exacerbation: a major long-term issue — LSG creates a high-pressure tubular system that worsens reflux; in the SLEEVEPASS 10-year study, 49% had worsened GERD, and 11.6% required conversion to RYGB
• Twisting/kinking of the gastric sleeve

C. Laparoscopic Adjustable Gastric Banding (LAGB)

• Band slippage — gastric prolapse through the band; acute obstruction
• Band erosion / migration — band migrates intragastrically; presents insidiously
• Port/tubing problems — disconnection, leakage, infection
• Esophageal dilation / pseudoachalasia / megaesophagus — abnormal peristalsis found in ~75% of patients undergoing band removal; can be irreversible
• Failure of weight loss — high long-term failure rate; 20% require band removal, 71% require revisional surgery by 7 years in French national data
• Overall: LAGB has fallen out of favor due to high long-term complication and reoperation rates

D. BPD/DS (Biliopancreatic Diversion with Duodenal Switch)

• Highest perioperative mortality (~1.1%)
• Severe malabsorption of fat-soluble vitamins (A, D, E, K), protein, iron, and calcium
• Protein malnutrition — can be life-threatening
• Metabolic bone disease (osteoporosis, osteomalacia)

III. Long-Term / Late Complications

Nutritional & Metabolic

Neurological

• Polyneuropathy, polyradiculoneuropathy — multiple nutritional deficiencies implicated
• Myelopathy — often vitamin B12 or copper deficiency; typically manifests ~10 years post-surgery
• Encephalopathy — thiamine deficiency (Wernicke's)
• Optic neuropathy

Gastrointestinal

• Small bowel obstruction — internal hernia (RYGB), adhesions; can occur months to years later
• Cholelithiasis / gallstones — rapid weight loss promotes gallstone formation; cholecystectomy sometimes done concurrently
• GERD — primarily after LSG (see above); can also improve after RYGB
• Bowel habit changes, diarrhea — especially after malabsorptive procedures

Psychological / Behavioral

• Alcohol use disorder — substance addiction transfer; increased risk post-RYGB due to altered alcohol metabolism
• Depression / psychiatric complications — preoperative mental health is a key predictor
• Eating disorders — night eating, binge eating recurrence

Other

• Ventral/incisional hernia — after any open or laparoscopic approach
• Excess skin / body dysmorphism — requires cosmetic/reconstructive surgery in many patients
• Renal oxalate stones — increased enteric oxalate absorption after bypass procedures
• Hypoglycemia — post-gastric bypass hypoglycemia (nesidioblastosis); late complication of RYGB

Summary by Severity