Bladder base insufficiency. Radiological, urodynamic, and clinical aspects.

Among 420 consecutive patients referred for voiding cystourethrography 26% presented the picture of bladder base insufficiency (b.b.i.). The examination was carried out as a colpo-cysto-urethrography. A urodynamic and gynecological examination was performed in each patient. The characteristic morphological features were: Anterior and inferior displacement of the bladder neck and a pointed bladder base. The position and form of the vagina was normal. Radiological signs of detrusor function were weak and opening of the bladder neck was characterized by funneling. Urodynamically the patients with b.b.i. showed low opening and low detrusor contraction pressures. The flows were highly varying. Very high flows were seen in a few patients but the more common pattern was slightly reduced maximum flow rates. Opening of the internal urethral orifice is known to be caused by detrusor contraction. Closing is passive, caused by elastic properties in the tissues. In b.b.i. intravesical pressures during micturition were low and radiological signs of detrusor contraction were weak, indicating that the bladder neck was easily opened. This, on the other hand, means that the bladder neck was insufficiently closed during bladder reservoir function, and may explain the main symptom, stress incontinence, which was present in 84% of the patients. The underlying pathology in anatomical support and suspension of the bladder base is discussed.