Detrusor after-contractions in children with normal urinary tracts

To assess the clinical significance of after-contractions (A-Cs) in children with normal urinary tracts.

Urodynamic records obtained in 315 children with urinary infection or enuresis were reviewed retrospectively; 184 were selected for analysis of A-Cs. All patients had normal urinary tracts and none showed signs of an overt neuropathy. The urodynamic method comprised standard measurements of pressures and flowmetry (42 had video-urodynamic studies).

After-contractions occurred in 151 of the 184 patients; the incidence tended to decrease with age. The mean amplitude of the A-Cs was 77.9 cmH2O; in 36% of the records it was higher than the voiding contraction. Residual urine was found in 12 of 151 records with A-Cs, but in only one patient was such residual urine confirmed in control voids. The patterns were assessed in 131 patients: in 36% they resembled stop-test responses, in 31% they were preceded by brief peaks of pressure or had jagged limbs, and in 33% they were grossly irregular. In 137 records the content of the bladder was estimated at the start of A-Cs; in 51% the bladder was empty or had evacuated >95% of its content, in 39% 95-80% and in 10% <80%. In only 7% of the patients had the A-Cs started after the voiding contraction had completely subsided. There was no difference in the incidence of A-Cs in girls with enuresis (84%) and girls with a history of urinary infections (85%). Detrusor instability was detected in 81% of the children with A-Cs and in 70% of those without; there was no correlation between the amplitudes of uninhibited detrusor contractions and of A-Cs. Characteristic images of external sphincter activity were found in only three of 14 video-urodynamic recordings with A-Cs.

After-contractions are common in children with normal urinary tracts but they tend to disappear with age. In clinical urodynamics they are of limited practical use because their appearance is unpredictable and there are artefacts related to recording the final phase of micturition. The relationship with detrusor instability may be explained as a coincidence of two common but unrelated findings, and A-Cs are unrelated to urinary infection. External sphincter activity is not the only cause of A-Cs and when it occurs it does not alter the course of voiding, as it does in neuropathic dysfunctions. As their clinical significance is uncertain, treatment of A-Cs is not advocated.