A clinical observation of retroperitoneal abscess simulating extrapulmonary tuberculosis is described. Medical imaging methods (ultrasound, MSCT) determined the presence of purulent process in the retroperitoneum with the presence of a dense round-shaped mass (calcified lymph node?) and ureterohydronephrosis on the right side, which raised suspicion of extrapulmonary tuberculosis. In the history, appendectomy was performed 16 years ago. The patient underwent surgery, opening and drainage of retroperitoneal space on the right side. After histopathologic examination, tuberculous etiology was rejected. Intraoperative picture, conversation with the patient already in the postoperative period, detailed analysis of the disease history before the patient’s admission to the clinic allowed us to assume that during the operation of appendectomy, a stone – fecolith – was probably left in the retroperitoneal space, which 16 years later became the cause of abscess formation. The patient did not report any pain or discomfort for a prolonged period of more than 16 years. This rare clinical observation showed the difficulty of diagnosis and insidiousness of the disease, which mimicked extrapulmonary tuberculosis. Surgical treatment with drainage of the abscess was the key to a favorable outcome.