MAGNETIC RESONANCE IMAGING OF A "SADDLE BAG" URETHRAL DIVERTICULUM

A woman presented with pelvic pain and recurrent urinary tract infections 2 years after transvaginal repair of a urethral diverticulum, Martius flap, and pubovaginal fascial sling. Physical examination revealed a tender 2-cm anterior vaginal wall mass. Voiding cystourethrography (VCUG) demonstrated a urethral diverticulum with possible circumferential involvement of the urethra (“saddlebag”diverticulum)(Fig.1).Cystourethroscopy demonstrated a wide diverticular neck at the 4 o’clock position in the urethral lumen, approximately 1.5 cm from the bladder neck. Magnetic resonance imaging (MRI) with an endovaginal coil was performed to evaluate the postsurgical anatomy as well as the anterior extent of the diverticulum relative to the urethral lumen. There was no evidence of the previously placed fascial sling or Martius fat pad on the MRI scan. The fluid-filled diverticulum (Fig. 2, open arrows) was seen completely encircling the urethra, with the inner mucosal lining of the diverticulum adherent to the outer wall of the urethra. Figure 2 demonstrates the usual anatomic location of urethral diverticula, which often dissect between the two leaves of fascia comprising the urethropelvic ligament1 (Fig. 2, large solid arrows). The junction of the urethral lumen and the diverticular cavity (neck of the diverticulum [Fig. 2, small arrow]) is seen as a disruption in the circumferential continuity of the spongy tissue of the urethra in approximately the same location as seen on cystourethroscopy. In the sagittal plane (Fig. 3), the diverticulum appears to extend anterior and posterior to the urethra (large arrow) from near the bladder neck to beyond the midurethra in close proximity to both sphincteric areas. The potential compromise or damage to both proximal and distal continence mechanisms was an important consideration during the planned excision and reconstruction of this complex urethral diverticulum. The patient underwent transvaginal excision of the diverticulum with a partial urethrectomy, urethral reconstruction, Martius flap, and pubovaginal fascial sling. At exploration, the diverticulum was noted to completely encircle the urethra and was tightly adherent to the urethral wall, as noted on the MRI scan. Fortunately, the MRI scan predicted this occurrence, and a portion of the dorsal diverticular wall was preserved to facilitate construction of a segment of neourethra. Although the true incidence is unknown, urethral diverticula may occur in up to 1% to 6% of the population.1 Presentation is nonspecific but may include pain, dyspareunia, anterior vaginal wall mass, and recurrent urinary tract infection.2 The sensitivity and specificity of VCUG and MRI in the diagnosis of urethral diverticula have not been clearly delineated; however, MRI may be more sensitive in the diagnosis of complex urethral abnormalities.3 In cases where the diverticular neck is narrowed, inflamed, or edematous, or when the diverticulum is loculated, VCUG may underestimate the size and/or extent of the diverticulum because the contrast medium may not flow freely From the Division of Urology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania Reprint requests: Daniel S. Blander, M.D., Department of Urology, University of Texas-Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75235-9110 Submitted: February 2, 1998, accepted: September 18, 1998 FIGURE 1. Right posterior oblique voiding image demonstrating a urethral diverticulum with possible circumferential involvement of the urethra. IMAGES IN CLINICAL UROLOGY