Bladder response to outflow obstruction.

The response of the detrusor muscle to the increased work load associated with outflow obstruction varies over time.

Early obstruction. At this stage, the detrusor undergoes hyperplasia, and bladder contractility may be normal or slightly impaired. The bladder is able to empty completely or nearly completely; however, bladder instability is likely to develop in 60% to 80% of patients. Unstable bladder contractions are involuntary contractions that are difficult to inhibit. Such contractions produce the sensation of urgency even at low volumes and account for symptoms such as urinary frequency and urgency and nocturia.

Late obstruction. The bladder is unable to empty completely, and postvoiding residual urine is present. Detrusor muscle contractility is significantly impaired. At this stage, residual urine results as much from poorly sustained bladder contractions as from inadequate detrusor pressure. The patient notes urinary hesitancy and intermittency and a weak stream and may complain of a sensation of incomplete voiding. With severe obstruction, the patient may use abdominal straining to void, and many male patients will sit to void to increase abdominal voiding pressure.

Decompensation. The ability of the detrusor muscle to contract is severely impaired to the point that little effective pressure is generated. The bladder may empty by frequent, ineffective voiding or by dribbling (overflow or paradoxical incontinence).

Siroky, Mike B.; Oates, Robert D.; Babayan, Richard K. Handbook of Urology: Diagnosis & Therapy, 3rd Edition. Boston : Lippincott Williams & Wilkins, 2004. ebook. Diakses 10 februari 2015.