Leak, bleeding, clot and stricture are the four that matter. Here is how likely each is and how they are prevented.
The most serious early complication, occurring in roughly 1% of sleeve cases. Prevention: careful technique, reinforcement where indicated, and a leak test before discharge. Detection: tachycardia and pain, which is why we keep patients 2–3 nights rather than one.
Bleeding affects around 1–2% and is usually managed conservatively. Venous thromboembolism is rarer but more dangerous — prevented with compression, blood thinners and, most importantly, walking within hours of surgery.
Narrowing at the sleeve or anastomosis causes persistent vomiting and is treated endoscopically. Reflux develops or worsens in a minority after sleeve, which is why existing GERD pushes the decision toward bypass.
Predictable and preventable: B12, iron, calcium and vitamin D. It is not a complication of surgery so much as a consequence of not taking supplements — which is why annual bloods are part of the programme, not an optional extra.
Large series report bariatric surgery mortality comparable to gallbladder removal — lower than the long-term mortality risk of untreated severe obesity.