VARIABILITY OF PRESSURE-FLOW ANALYSIS PARAMETERS IN REPEATED CYSTOMETRY IN PATIENTS WITH BENIGN PROSTATIC HYPERPLASIA

Urodynamic investigation becomes increasingly important in the diagnos is of bladder outflow obstruction in patients with benign prostatic hy perplasia. To date, different methods for evaluation of the pressure-f low relationship and quantification of the grade of obstruction are av ailable. Models for pressure-flow analysis are briefly explained. The variability of the parameters is investigated by evaluation of 75 pati ents in whom 2 sequential voidings during urodynamic investigation wer e analyzed. The results showed that in 87% of these patients individua l maximum flow differences of first and second voidings were less than 2 ml. per second. Individual detrusor pressure at maximum flow differ ences were less than 15 cm. water in 80% of these patients, while in 8 0% the intra-individual variation of the pressure-flow results was les s than 15 cm. water for the minimal voiding pressure parameters (minim al urethral opening detrusor pressure and urethral resistance factor). For the pressure-flow parameter that defines the theoretical urethral lumen during voiding, the variation was less than 1.5 mm.(2) in 84% o f the patients. Patients with larger intra-individual differences are discussed. We concluded that the observed, aforementioned differences can be regarded as an indication of normal intra-individual variabilit y of voiding during urodynamic investigation. This intra-individual va riability, however, seldom leads to a change in the clinical grade of bladder outflow obstruction. We conclude that investigators involved i n therapeutic trials of benign prostatic hyperplasia must be aware of this intra-individual variability of micturition, since this variabili ty is greater than the refined scale of the pressure-flow analysis mod els.