Renal Endometriosis in a Postmenopausal Female Mimics Renal Cell Carcinoma

A 61-year-old postmenopausal female with a past medical history of type 2 diabetes, nephrolithiasis, and recurrent urinary tract infections presented to an outpatient urology clinic with a chief complaint of urinary frequency, urgency, and burning after micturition. Associated symptoms included nausea, a low-grade fever with chills, and right flank pain. After treatment with antibiotics did not relieve all of her symptoms, imaging was obtained, showing a cystic mass with calcifications in the right kidney. Following laparoscopic partial right nephrectomy and total hysterectomy with bilateral salpingo-oophorectomy, pathological examination of the right kidney mass highlighted endometrial stromal cells consistent with endometriosis of the right kidney. The left ovary also contained endometrial stromal cells, confirming another diagnosis of endometriosis of the left ovary. This case highlights the importance of considering renal endometriosis in the differential diagnosis of renal masses in women, even if they are postmenopausal.