Bariatric Surgery Basics
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Direct answer
Bariatric (metabolic) surgery is indicated, on standard criteria, at body mass index of 40 or above, or 35 and above with obesity-related comorbidity, while Asian-population consensus including India uses lower cut-offs — commonly 37.5 alone, or 32.5 with comorbidities such as type 2 diabetes. The operations work by restriction, malabsorption or combined mechanisms plus neurohormonal changes: Roux-en-Y gastric bypass creates a small pouch draining into a Roux limb, sleeve gastrectomy resects most of the stomach including ghrelin-rich fundus, and the adjustable gastric band and biliopancreatic diversion with duodenal switch complete the list. Sleeve gastrectomy is now the most commonly performed procedure; classic exam complications are anastomotic leak (unexplained tachycardia earliest), dumping syndrome, internal hernia, marginal ulcer and lifelong micronutrient deficiency.
What you must remember
- Indications: BMI 40 or more, or 35 or more with comorbidity, on standard criteria; Indian and Asia-Pacific consensus uses 37.5 or more alone and 32.5 or more with comorbidity for Asian populations; commitment to lifelong follow-up is a prerequisite.
- Roux-en-Y gastric bypass: combined restrictive and malabsorptive; small pouch with gastrojejunostomy and Roux limb; the reference operation with strong metabolic effects on type 2 diabetes.
- Laparoscopic sleeve gastrectomy: resection of about 75–80 per cent of the stomach along a bougie, removing ghrelin-producing fundus; staple-line leak and bleeding are chief complications.
- The adjustable gastric band is least invasive but carries the highest reoperation rate (slippage, erosion); biliopancreatic diversion with duodenal switch is the most malabsorptive, with the greatest weight loss but the highest risk of protein-calorie malnutrition.
- Early leak sign after any bariatric operation: unexplained tachycardia (commonly over 120 per minute) with tachypnoea — re-explore rather than observe when suspected.
- Dumping syndrome: early postprandial vasomotor symptoms (palpitations, sweating, cramps, diarrhoea) within about 30 minutes of hyperosmolar food; late dumping from reactive hypoglycaemia 1–3 hours after meals.
- Long-term issues: internal herniation through mesenteric defects (Petersen's space), marginal ulcer and gallstones from rapid weight loss; lifelong supplementation of iron, B12, folate, calcium, vitamin D and thiamine — deficiency with persistent vomiting risks Wernicke's encephalopathy.
Common confusion
Candidates quote only Western BMI thresholds and miss that Indian practice follows lower Asian cut-offs, an exam favourite. The second confusion is mechanism: sleeve gastrectomy is not purely restrictive — ghrelin reduction and altered gut hormone profiles give metabolic benefits approximating bypass. Finally, dumping syndrome is often mislabelled as an allergy or intolerance; it is a physiological consequence of rapid delivery of hyperosmolar food into the small intestine.
Exam-focused takeaway
Questions ask which procedure matches which mechanism or complication: band with slippage and erosion, bypass with internal hernia and marginal ulcer, sleeve with staple-line leak and ghrelin, duodenal switch with malnutrition. Clinical stems feature a post-bypass patient with intermittent colicky obstruction and a 'normal' plain film (internal hernia) or tachycardia on day 3 (leak until proven otherwise). Also learn the Asian BMI cut-offs and the micronutrient list with thiamine as the emergency deficiency.
Frequently asked questions
What BMI thresholds apply to Indian patients?
Per Indian and Asia-Pacific consensus, surgery at BMI 37.5 or above alone, or 32.5 or above with metabolic comorbidities such as type 2 diabetes — lower than Western thresholds because metabolic risk begins at lower BMI in Asians.
Why does sleeve gastrectomy improve diabetes early?
Removing the ghrelin-rich fundus and accelerated nutrient transit raise incretin (GLP-1) secretion, improving glycaemia within days, before substantial weight loss.
What is the earliest warning of an anastomotic leak?
Unexplained sinus tachycardia with tachypnoea and feeling of impending doom after bariatric surgery; urgent contrast imaging or re-exploration follows, since delay is lethal.
Which supplements must be monitored lifelong after bypass?
Iron, B12, folate, calcium and vitamin D at minimum, with thiamine during prolonged vomiting to prevent Wernicke's encephalopathy.