Urethral Diverticula in Women: Discrepancies Between Magnetic Resonance Imaging and Surgical Findings

Purpose: Some groups consider magnetic resonance imaging the gold standard to diagnose urethral diverticula with up to 100% reported sensitivity. We describe cases contradicting this paradigm and identify reasons for discrepancies. Materials and Methods: We searched a database for women who underwent urethral diverticulum surgery from 1998 to 2008 and also underwent preoperative magnetic resonance imaging. Images were reviewed by a blinded panel of urologists and a radiologist. They came to consensus on the presence or absence, site and anatomy of urethral diverticulum or cancer, and compared operative findings. Discrepancies were classified as errors in urethral diverticulum or cancer diagnosis and errors in urethral diverticulum anatomy or site. Results: Of 76 patients who underwent diverticulectomy 41 also underwent magnetic resonance imaging, of whom 10 (24.4%) had a discrepancy between magnetic resonance imaging and surgical findings. In 6 of these cases there were diagnosis errors and diverticula were not seen on magnetic resonance imaging in 3. One urethral diverticulum each was misdiagnosed as Bartholin's cyst and as a typical post-collagen injection appearance. A sterile abscess was incorrectly diagnosed as a urethral diverticulum. In 2 patients magnetic resonance imaging did not detect cancer within the diverticulum. A major discrepancy in anatomy made intraoperative decision making difficult in 2 patients. Conclusions: In cases clinically suspicious for urethral diverticulum magnetic resonance imaging had a 24.4% error rate. Serious consequences are failure to detect cancer and suboptimal treatment for urethral diverticulum. The reason for the high magnetic resonance imaging accuracy rate in other series may be that in the absence of radiological confirmation some surgeons may choose not to perform surgery. Magnetic resonance imaging is useful to assess urethral diverticula but physicians should be aware of its limitations.