Gastrointestinal & Hepatic · Topic 23 of 27

GI & Bariatric Surgery Complications

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Gastrointestinal · surgical complications

GI & Bariatric Surgery Complications

After bariatric surgery, unexplained tachycardia may be the only sign of a leak, and a negative CT excludes neither a leak nor an internal hernia.

01 · Bariatric leakTachycardia may be the only early sign

02 · Hernia after bypassCT often misses it: low threshold to re-explore

03 · Dumping timingEarly within 1 h, late at 1–3 h after a meal

Bariatric leak: what you'll see

Body habitus makes the abdominal exam unreliable

Tachycardia may be the only early sign of anastomotic leak early

Severe abdominal or shoulder-tip pain with tachycardia is ominous

Hiccups with tachycardia are ominous

Typical: tachycardia, leukocytosis, high CRP

Presents at an average of 9.5 ± 7.4 days, well after usual discharge

Follows about 1.6% of Roux-en-Y gastric bypasses

Most often at the gastrojejunal anastomosis

Diagnosis: leak and internal hernia

A negative CT excludes neither

Stable, suspected leak: order CT with IV and oral contrast

A negative CT does not exclude a leak

Persistent unexplained tachycardia may still warrant surgical exploration

Bypass with intermittent cramping or left upper quadrant pain: suspect internal hernia

CT often misses internal hernia: keep a low threshold to re-explore

Endoscopy is not indicated for internal hernia

Red flags

Instability or generalized peritonitis from a leak urgent OR

Persistent unexplained tachycardia despite a negative CT consider exploration

Stoma ischemia at or below the fascia re-explore, revise

Perforated marginal ulcer surgical repair

Prolonged vomiting: thiamine deficiency, Wernicke encephalopathy parenteral thiamine

IV dextrose before thiamine can precipitate Wernicke thiamine first

See The Acute Abdomen & Perforation and Metabolic & Toxic Encephalopathy.

Treatment

Suspected leak: right now

Resuscitate, give broad-spectrum antibiotics

→

Unstable or generalized peritonitis: urgent operative source control

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Stable: CT with IV and oral contrast

Stable leakmay avoid the OR

Antibiotics, image-guided drainage, endoscopic therapy, nutritional support

With bariatric input

Ulcermarginal

High-dose PPI Sucralfate

Confirm by upper endoscopy; high-dose liquid or open-capsule PPI, with or without sucralfate

Stop NSAIDs. Drivers: H. pylori, smoking, diabetes, NSAIDs

Strictureendoscopic

Balloon dilation to at least 8 mm

Look for an ulcer as well

Thiamineprolonged vomiting

Parenteral thiamine

Give parenteral thiamine

A carbohydrate load such as IV dextrose can precipitate Wernicke

Rarer surgical complications

Parastomal hernia is common: over 50% of colostomies followed beyond 5 yearsUsually well tolerated; obstruction and strangulation are rare but need surgery

Stomal varices form in portal hypertensionPortosystemic collaterals in peristomal skin, a peristomal caput medusa; bleeding can be profound

Adjustable gastric band urgencies: slippage, erosion with perforationSlippage: first aspirate the band fluid; if decompression fails, the band must be surgically removed

Portomesenteric vein thrombosis: abdominal pain, nausea, intermittent emesisOrder abdominal CT, rehydrate, anticoagulate; reserve exploration for suspected bowel compromise

Rapid weight loss promotes gallstones; standard ERCP may be impossible after bypassLaparoscopic-assisted ERCP through the remnant stomach is often preferred in the emergent setting

Pancreatic fistula: drain amylase above 3 times the serum upper limit of normalClinically relevant with a related clinical condition; without clinical impact it is a biochemical leak

Persistent vomiting and marginal ulcer

Later prolonged vomiting: anastomotic stenosis or small bowel obstruction

Stricture: gastrojejunal lumen under about 6 mm

Marginal ulcer forms at the gastrojejunal anastomosis

The 6 mm definition is from one 2025 gastroenterology review; definitions vary.

Why dumping happens

Rapid emptying causes early and late dumping

Rapid emptying: fluid shifts into the gut (early); GLP-1 surges insulin (late)

Hyperosmolar content in the small intestine shifts plasma fluid into the lumen, causing tachycardia, hypotension and cramps (early dumping). High glucose delivery triggers an exaggerated GLP-1-driven insulin response and reactive hypoglycemia (late dumping).

Early or late dumping?

	Early dumping	Late dumping
Timing after a meal	Within 1 hour	1–3 hours
Mechanism	Hyperosmolar food shifts fluid into the bowel	Incretin-driven insulin surge causes hypoglycemia
Symptoms	Cramps, diarrhea, flushing, palpitations	Sweating, tremor, confusion, syncope
Glucose tolerance test	Hematocrit rise over 3% or pulse rise over 10 bpm at 30 minutes	Nadir glucose under 50 mg/dL

Dumping: test and treat

A modified glucose tolerance test diagnoses dumping

Gastric emptying testing is unhelpful

First: dietary adjustment, such as frequent small meals

Late dumping symptoms: add acarbose

Failed diet and acarbose: somatostatin analogue, such as octreotide

Stoma ischemia and timing

Ischemia at or below the fascia needs immediate re-exploration and revision

Dusky stoma: lubricated test tube and flashlight assess the distal 5–6 cm of mucosa

Endoscopy shows the proximal extent

Emergency stoma creation raises necrosis risk

Early (first 30 days): ischemia or necrosis, retraction

Early (first 30 days): mucocutaneous separation, parastomal abscess

Late: parastomal hernia, prolapse, retraction, varices

High-output stoma and fistula

Manage as high-output when output stays above about 1,500 mL/day; no volume is agreed

First exclude intra-abdominal sepsis and obstruction

First exclude enteritis, including C. difficile

First exclude sudden steroid or opioid withdrawal

Replace losses with IV fluid

Limit hypotonic drinks to 1 L/day; use oral rehydration solution

Stop laxatives and prokinetics

After a baseline ECG: loperamide 4 mg four times daily before meals

Enterocutaneous fistula over 500 mL/day is high-output: may need PN

Low-output fistula with controlled drainage: often oral or enteral feeding

No agreed volume: sources cite > 1,000, > 1,500 or > 2,000 mL/day, and a 2025 expert forum says volume alone should not define it. One UK protocol (NHS Lanarkshire 2026) requires more than 3 days; its doses are the ones here, and it also starts a PPI to cut secretions and titrates loperamide up to 8 mg four times daily.

VTE prophylaxis

DVT and PE are recognized complications of bariatric surgery

Fixed enoxaparin 40 mg daily underdoses severe obesity

BMI ≥ 40: enoxaparin 40 mg twice daily (review-based, not a trial)

The AAGBI/SOBA table doses by weight instead: 40 mg twice daily at 100–150 kg, 60 mg twice daily above 150 kg. See Severe Obesity in Acute Care.

Long-term follow-up

Monitor B12, iron, folate, vitamin D, calcium, parathyroid hormone

Monitor thiamine when indicated

Bone density after sleeve or bypass

Reassess antihypertensive and diabetes drugs during rapid weight loss

Pearl

A heart rate that will not settle after bariatric surgery is a leak until proven otherwise, even with a normal CT.

Sources · Merck Manual Professional — Metabolic and Bariatric Surgery (updated Feb 2026) · Kodilinye SM, Kumbhari V, Badurdeen D. Complications of Metabolic and Bariatric Surgery for the Gastroenterologist. Gastroenterol Hepatol 2025;21(2) · Altieri MS et al. Bariatric emergencies for the general surgeon (ASMBS). Surg Obes Relat Dis 2023;19(5):421–433 · Scarpellini E et al. International consensus on the diagnosis and management of dumping syndrome. Nat Rev Endocrinol 2020 · Krishnamurty DM, Blatnik J, Mutch M. Stoma Complications. Clin Colon Rectal Surg 2017;30(3) · Merck Manual Professional — Wernicke Encephalopathy (Jun 2025) · NHS Lanarkshire. Management of High Output Stoma Guideline, v3 (May 2026) · Carr M, Caers F et al. Redefining the High-Output Stoma and Its Bearing on Clinical Practice: Results of an International Consensus Panel. J Wound Ostomy Continence Nurs 2025 · Kumpf VJ, Yeh DD et al. Use of parenteral nutrition in the management of enterocutaneous fistula. Nutr Clin Pract 2024 · Nightingale CE et al. Peri-operative management of the obese surgical patient 2015 (AAGBI/SOBA). Anaesthesia 2015 · Bassi C et al. The 2016 update of the ISGPS definition and grading of postoperative pancreatic fistula. Surgery 2017 · Sebaaly J, Covert K. Enoxaparin dosing at extremes of weight: literature review and dosing recommendations. Ann Pharmacother 2018;52(9):898–909 · Agosta M et al. Infectious Complications in Metabolic and Bariatric Surgery: A Comprehensive Narrative Review. Life (Basel) 2026 · Docquity. ASMBS Guidelines for General Surgeons: Bariatric Emergency Management (2023 summary of Altieri et al.) · Early and Late Complications After Sleeve Gastrectomy and Roux-en-Y Gastric Bypass: A Narrative Review. J Metab Bariatr Surg 2026 · Hussain A, EL-Hasani S. Bariatric emergencies: current evidence and strategies of management. World J Emerg Surg 2013;8:58 · Follow your institution's protocols.