Introduction & objectives. Until recently, there remain many unresolved issues in terms of differential diagnosis and choice of treatment methods for bladder endometriosis. We performed a study of the effectiveness of using modern methods of diagnosis and treatment of some atypical anatomical and morphological lesions of bladder endometriosis. Material & Methods Studies were performed in two patients with atypical anatomical and morphological lesions of the bladder by endometriosis. According to MRI of the pelvic organs, CT of the kidneys with contrast, and cystoscopy, the diagnosis was made: bladder neoplasm, involving the intramural section of the right ureter and stage II right ureterohydronephrosis. In the second case, patient S., 41 years old, chronic cystitis was diagnosed and had been treated unsuccessfully in outpatient settings for two years. According to MRI of the pelvic organs, cytological examination and cystoscopy, the patient was previously diagnosed with a tumor (bullous edema) of the posterior wall of the urinary bladder. Results In the first clinical case, the patient underwent surgical intervention - resection of the bladder wall with a neoplasm and resection of the lower half of the right ureter. Express histological examination didn’t confirm the malignant tumor. The morphologist concluded that the intramural part of the ureter and the bladder wall were affected by endometriosis. The patient underwent excision of visible endometrioid foci of the bladder and paravesical tissue, and ureterocystoanastomosis was performed into the repositioned bladder wall using the Psoas hitch method. In the second clinical case transurethral electroresection of the affected area with muscle tissue has been performed, as well as laser ablation using a holmium laser. Histological examination revealed bladder endometriosis. In the first and second clinical cases it was impossible to assess the depth and area of bladder wall damage intraoperatively, both patients were prescribed conservative treatment with the hormonal progestin dienogest by the gynecologist. The course of treatment was carried out continuously for 10 months. During the follow-up examination of patients after the end of the treatment course and one year after discontinuation of dienogest, no recurrence of bladder endometriosis was detected. Conclusions The presented clinical cases of endometriosis of the urinary bladder prove the complexity of its differential diagnosis with tumor lesions. Radical surgical removal of endometrioid foci in combination with long-term adjuvant therapy with progestogens is a more effective method of treating endometriosis of the urinary bladder.

Bladder Endometriosis, Progestin, Ureterohydronephrosis