Unusually rapid growth of bilateral endometriomas and acute bilateral hydronephrosis.

Ultrasonography can detect ovarian endometriomas, but negative findings cannot exclude other localizations of endometriosis, especially in symptomatic patients. We describe a case of sudden development of large bilateral endometriomas after a series of negative ultrasound scans, causing bilateral hydronephrosis. Our patient is a 32-year-old nulligravida with long-lasting dysmenorrhea, urinary symptoms, and familiarity for endometriosis, who had voluntarily discontinued oral contraceptives. Various pelvic scans had not shown pathological findings. Five months following the last negative scan, she presented with pain and increase of abdominal girth. Ultrasonography and computed tomography showed large ovarian cysts (16 cm right - 10 cm left) and hydronephrosis bilaterally. She underwent conservative surgery followed by GnRH analogs. At a 6-months follow-up, she was symptom-free and ultrasonography showed no recurrence. Endometriosis has still an unknown mechanism of proliferation and its clinical behavior or progression is highly unpredictable. Severe uropathy is commonly related to direct ureteral involvement, but can also depend on an ab-extrinseco compression by large, rapidly growing endometriomas. Women at risk of endometriosis, who are not receiving empirical medical treatment, should be adequately and regularly assessed via pelvic ultrasonography and/or submitted to diagnostic laparoscopy in order to prevent serious consequences such as silent renal loss.