[Diagnostic utility of cuff flowmetry in lower urinary tract obstruction in men]

to investigate the usefulness of cuff flowmetry for the diagnosis of lower urinary tract obstruction in males.

1) To investigate the relationship between isovolumetric pressure (Piso) and bladder contractility. 2) To investigate the relationship between the type of flow curves obtained by this method and the type of lower urinary tract obstruction, and previous history of prostate surgery.

We perform a cohort study in a series of 93 consecutive males (mean age 54.1 yr.) referred with functional lower urinary tract symptoms. They were interviewed about history of prostatic surgery, and they underwent isovolumetric pressure measurements (Piso), and corresponding flow (Qiso) by means of cuff flowmetry. From these parameters we calculated the Riso parameter, defined as Piso/(Qiso)2. A conventional pressure/flow study was performed afterwards, with computer calculation of urethral resistance parameters--footpoint and PURR curvature--, and the bladder contractility parameter Wmax.

The diagnostic efficiency curve for the Riso parameter showed that the ideal cutpoint corresponded to a value of 1.29 cm H2O/(ml/sec)2. For this value the sensitivity for the diagnosis of lower urinary tract obstruction was lower than 78% and specificity was 73%. We elaborated a nomogram for the relationship between Piso and Qiso using a logistic regression model. This nomogram was divided in three areas (obstructive, equivocal, and not obstructive). If patients within the equivocal area (9.7% of the sample) were excluded, then the nomogram had a sensitivity of 84% and a specificity of 73% for the diagnosis of obstruction. We observed a significant association between flow curves with an absent initial peak morphology and obstruction of the constrictive type. No relationship was demonstrated between history of prostate surgery and type of curve.

Cuff flowmetry has an acceptable sensitivity and specificity for the diagnosis of lower urinary tract obstruction. However, our study did not demonstrate its usefulness for the determination of the detrusor contractile capacity. Piso and Qiso parameters would be urethral resistance parameters.