Background and Aims Postoperative intra-abdominal infection (PIAI) is a common postoperative complication in abdominal surgery and a challenging issue worldwide, with a treatment failure rate of 68.3% and an in-hospital mortality rate as high as 40.8%. The key to managing this condition is early control of the infection source, debridement and adequate drainage. Delayed control of the infection source is an independent risk factor for predicting treatment failure. Many PIAI lesions are located deep within the abdominal cavity, lacking optimal routes for percutaneous drainage, and the risks and difficulties of reoperation are significant. Thus, controlling the infection source in PIAI is a difficult task. Here, the authors report the management of 4 PIAI patients treated with nephroscopic debridement and catheter irrigation and drainage via the sinus tract, aiming to provide clinical insights and references.Methods The clinical data of 4 patients undergoing nephroscopic debridement, catheter irrigation and drainage for PIAI from October 2020 to September 2022 in the Department of Hepatobiliary and Pancreatic Surgery of the Second Affiliated Hospital of Guilin Medical University were retrospectively analyzed. Key techniques of nephroscopic management of PIAI were summarized and contextualized with relevant literature.Results The 4 PIAI cases included a right-sided retroperitoneal abscess after catheter drainage for severe acute pancreatitis, a hepatic abscess at the liver raw surface after right hemihepatectomy, bile leakage and secondary duodenal fistula after laparoscopic choledocholithotomy and T-tube drainage, and a pancreatic abscess at the pancreatic raw surface after distal pancreatectomy with splenectomy. All patients underwent nephroscopic debridement and catheter irrigation and drainage via the sinus tract: guidewires were inserted into the drainage sinus tract, followed by a minimally invasive expansion drainage kit and nephroscopy; pus was irrigated out, and pus moss was clamped out with foreign body forceps under nephroscopy. Then, irrigation drainage tubes were placed under the guidance of the guidewire, and continuous irrigation and drainage were performed. The 4 patients underwent a total of 5 nephroscopic debridement and catheter irrigation and drainage procedures, with one case requiring two operations. The preoperative catheterization time ranged from 14 to 58 d, with an average of 38.4 d. One patient concurrently underwent choledochoscopy for stone extraction and biliary drainage via the T-tube sinus tract. The operative time ranged from 30 to 115 min, with an average of 67.4 min. Aside from one case of minor intraoperative bleeding, which stopped after injecting diluted norepinephrine solution into the sheath and blocking the sheath, there were no surgical complications in the other three cases. The postoperative drainage tube duration ranged from 7 to 30 d, with an average of 20.75 d. After treatment, all PIAI lesions disappeared, and no recurrence was observed during follow-up, which ranged from 16 to 40 months.Conclusion Nephroscopic debridement and catheter irrigation and drainage via the sinus tract for PIAI is simple, feasible, and safe, allowing for direct visualization to avoid organ damage. It is effective in removing pus and necrotic tissue, replacing drainage tubes, and can be repeatedly performed with high efficiency and remarkable results. This method is particularly suitable for patients with postoperative abdominal drainage tube obstruction combined with encapsulated intra-abdominal fluid collections.