**Background:** Laparoscopic sleeve gastrectomy (LSG) is the most commonly performed bariatric and metabolic surgery worldwide, accounting for 92.7% of the 985 bariatric procedures performed in Japan in 2022. Staple line leakage ('sleeve leakage') is a rare but serious complication, with an international incidence of 0.7–5% and a reported incidence of 0.5% in Japan. Approximately 75–85% of leaks occur at the proximal third of the greater curvature staple line, typically on postoperative day 5 or later. The upper sleeved stomach has lower blood flow and thinner walls, and factors such as excessive dissection near the angle of His, thermal injury, staple misalignment, and distal stenosis with increased intragastric pressure contribute to leakage. Symptoms include abdominal pain, back pain, fever ≥38°C, and tachycardia >120 bpm. Leaks are classified as early (days 1–3), intermediate (days 4–7), or late (day 8 or later).
**Methods:** This is a narrative review of peer-reviewed literature and selected gray literature on the pathogenesis and treatment of sleeve leakage after LSG, with a focus on the Japanese healthcare context.
**Key Results:** The review describes multiple treatment modalities. Initial management includes nil per os, intravenous fluids, broad-spectrum antibiotics, and drainage (CT-guided or laparoscopic). Conservative treatments following initial drainage include: (1) Kangaroo™ W-ED tube (US$17), a Japanese-developed double-lumen tube allowing simultaneous drainage and enteral nutrition; (2) Over-The-Scope Clip (OTSC®, US$600 per clip), which provides stronger tissue capture than conventional clips; (3) endoscopic balloon dilation for distal stenosis, requiring balloons >30 mm diameter (achalasia balloon, US$990; hand pump, US$245); (4) self-expandable removable stents (e.g., HANAROSTENT®, Niti-S®, US$960), with a success rate up to 80% and standard placement duration of 6–8 weeks, but not covered by Japanese NHI for this indication; (5) percutaneous transesophageal gastro-tubing (PTEG, US$500 per kit), which can provide both drainage and jejunal nutrition; and (6) endoscopic vacuum therapy (EVAC, Endo-SPONGE®, US$220 per set), which promotes granulation tissue formation with healing typically within ~2 weeks but is unavailable in Japan. When conservative treatment fails, revisional surgery is considered after approximately 12 weeks of persistent leak. Surgical options include fistulo-jejunostomy (Roux-en-Y patch) and total or proximal gastrectomy with esophagojejunostomy or double-tract reconstruction.
**Clinical Implications:** Sleeve leakage remains a challenging complication with no high-evidence treatment algorithm due to its low incidence. Personalized treatment is required based on timing, location, size of the leak, presence of distal stenosis, and available resources. In Japan, strict NHI regulations limit access to some effective devices (e.g., esophageal stents for leaks), while the W-ED tube (US$17) offers a uniquely cost-effective option. The authors emphasize that surgeons must maintain a high index of suspicion for leaks, prioritize drainage and nutritional support throughout treatment, and consider revisional surgery before chronic inflammation (beyond 12 weeks) increases surgical risk. Mortality from sleeve leaks is possible, and as the number of LSG procedures increases in Japan, familiarity with the full range of treatment options is essential.