The pathophysiology of large capacity bladder.

PURPOSE We describe the pathophysiology, differential diagnosis and urodynamic findings in patients with a large capacity bladder. MATERIALS AND METHODS This was a retrospective, observational study of 100 consecutive patients with voiding dysfunction and a cystometric bladder capacity of greater than 700 ml. Clinical data, cystometric bladder capacity and other urodynamic findings were evaluated. Bladder outlet obstruction and impaired detrusor contractility were defined by the Schaefer nomogram in men and the Blaivas-Groutz nomogram in women. RESULTS A total of 56 men and 44 women 36 to 97 years old (median age 75, mean 71.2) with a bladder capacity of 700 to 5,013 ml (median 931, mean 1,091) were studied. The primary pathophysiological diagnoses were bladder outlet obstruction in 48% of cases, impaired detrusor contractility in 11%, absent detrusor contractility in 24% and normal detrusor pressure/uroflow study in 17%. Bladder outlet obstruction was attributable to anatomical obstruction in 34% of patients, acquired voiding dysfunction in 11% and detrusor-external sphincter dyssynergia in 3%. In patients with detrusor contractions the initial contraction occurred at a median of 1,000 ml (mean 1,154, range 86 to 5,000). Associated diagnoses in men included benign prostatic enlargement in 52% and neurological disease in 14%, and in women they were pelvic organ prolapse in 27%, stress incontinence in 18% and neurological disorders in 9%. CONCLUSIONS The etiology of large capacity bladder is multifactorial and often a potentially remediable underlying condition exists. A large capacity bladder may be accompanied by bladder outlet obstruction, impaired or absent detrusor contractions, or normal detrusor pressure/uroflow studies. When detrusor contractions are present, they usually occur only at large bladder volumes. Therefore, it is important during cystometry to fill the bladder until capacity is achieved.