A critical reappraisal of cystometry in neurogenic bladder diseases.

Repeated cystometry was performed over an eight hour period in 14 patients with detrusor hyperreflexia. Volumes at first contraction, and at bladder capacity and also bladder compliance showed significant differences within individual variances and an increase in standard deviation in relation to increase in mean value. Amplitude of contractions showed equal variances in all patients. After a logarithmic transformation of the measurements the volume at first bladder contraction showed a significant increase (p less than 0.02) from the first to the second investigation performed an hour later. Determination of sample size in clinical trials using the pooled estimate of the standard deviations is discussed.