The purpose of the study was to analyze the characteristics of the course and outcome in patients with diffuse peritonitis, depending on the methods of repeated sanitation and drainage of the abdominal cavity and ultrasound monitoring. The authors carried out a retro-spective analysis of the results of treatment of 102 patients. All patients were divided into 2 groups depending on the method of treatment, with randomization by extent and phase of peritonitis. In the group 1, a semi-open method of treatment was used: sanitation and drainage of the abdominal cavity with continuous peritoneal lavage, and staged relaparotomy according to indications. In the group 2, video laparoscopic sanitation and drainage of the abdominal cavity on demand were applied. In this group, with the Mannheim Peritonitis Index below 15 points, drainage was not performed. With the Mannheim index below 20 points, 1–2 drains were installed, when above 25 points — 3–4 drains. Postoperative complications in patients of the group 1 were found in 40.9%. In the group 2, there were fewer complications compared the group 1. This was due not only to fewer local complications, but also intra-abdominal complications, which were almost 2 times fewer. Thus, video laparoscopic sanitation is the method of choice for planned repeated sanitation of the abdominal cavity. Relaparotomy should be performed only with strict indications in the event of intra-abdominal complications and if video laparoscopic sanitation cannot be performed. Ultrasound monitoring in the post-operative period makes it possible to timely identify postoperative complications, differentiate their nature and exact localization.