A retroperitoneal abscess is a limited accumulation of pus located between the posterior leaf of the peritoneum and the intraperitoneal fascia. Ulcers can be single, reaching significant amounts at the same time, or multiple. Diagnosis of the latter is difficult due to the small size of the formations and the erased clinical picture [3]. Abscesses can form as a result of injuries, surgical intervention, perforation of the organ canopy and metastasis of infection from neighboring structures. Ulcers appear in 0.8% of cases after elective abdominal surgery, and in 1.5% after emergency surgery. The disease occurs mainly in people aged 20-40 years [4,7].

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