Urodynamic risk factors for renal dysfunction in men with obstructive and nonobstructive voiding dysfunction

Urodynamic investigation of men with lower urinary tract symptoms, usually attributed to benign prostatic hyperplasia, often reveals bladder outlet obstruction, detrusor instability and/or diminished vesical compliance. We investigated whether these urodynamic abnormalities alone or in combination contribute to renal dysfunction.

A total of 161 men with lower urinary tract symptoms was evaluated by urodynamics, and outlet obstruction, detrusor instability and decreased compliance (30 ml./cm. water or less) were noted. Serum blood urea nitrogen (BUN) and creatinine were measured. Cases were categorized according to the urodynamic diagnosis. Mean values of serum BUN and creatinine as well as the incidence of elevated BUN and creatinine were compared among groups.

Of the cohort 54 men (34%) had elevated BUN and 19 (12%) had elevated serum creatinine. No significant correlation was found between the degree of obstruction and BUN or creatinine level. Mean serum BUN and creatinine, and the incidence of abnormal laboratory tests did not significantly differ among those with outlet obstruction, detrusor instability, both conditions or neither condition. However, in patients with outlet obstruction and detrusor instability there was a significantly increased incidence of azotemia in the subgroup with diminished compliance (78%) versus the subgroup with normal compliance (36%).

In men with voiding dysfunction of a nonneurogenic etiology outlet obstruction with or without detrusor instability does not appear to be a risk factor for elevated BUN and creatinine. However, when decreased bladder compliance is associated with a combination of outlet obstruction and detrusor instability, this risk is substantially increased.