Urinary retention in a female patient caused by a urethral venous thrombus with massive edema.

Female urinary retention is rarely caused by an unknown condition. In such a case, common causes including neurogenic, anatomical, traumatic and iatrogenic voiding dysfunction are excluded. Both the radiological and histological findings specific to the condition remain unclear. We herein report a 75-year-old woman in whom a large venous mass and massive edema at the proximal urethra caused urinary outlet obstruction based on magnetic resonance images and histological findings. Ultrasonography and cystoscopy showed a urethral mass lesion protruding into the bladder neck. Fat-suppressed T2-weighted and gadolinium-enhanced T1-weighted magnetic resonance images suggested thrombosed veins with massive edema under the urethral mucosa. Transurethral resection of the mass lesion was carried out, and histopathological analysis proved the presence of thrombosed large veins. The patient regained normal urination, and the mass lesion did not recur. Thrombosed venous mass with edema at the proximal urethra might be an important cause of atypical urinary retention in women.