The reliability of cysto-urethrographic signs in the diagnosis of detrusor instability in children

OBJECTIVE: To assess whether the signs associated with detrusor instability (DI), as assessed by video-urodynamic studies, can be evaluated by conventional voiding cysto-urethrography (VCUG). PATIENTS AND METHODS: Fifty-nine children who underwent cystometry and VCUG were reviewed and divided into two groups; group 1 comprised 51 neurologically normal children who had DI (47 girls and four boys, mean age 7.9 years, range 4-14), with no malformations or previous surgery. Most had mixed symptoms, including urinary tract infections (44) and nocturnal enuresis with daytime symptoms (20); group 2 (control) comprised eight children (seven girls, mean age 9.7 years, range 6-15) with a stable bladder and the same clinical presentation. The interval between VCUG and cystometry ranged from 1 day to 5 months (mean 47 days) and was similar in both groups. Signs considered suspicious of DI were sought in the findings of VCUG. RESULTS: In group 1, VCUG was normal or showed no specific signs (only vesico-ureteric reflux or vaginal voiding) in 25 (49%) of patients, whereas 26 (51%) had some signs suspicious of DI. Suspicious signs were urethral ballooning (in 11), bladder trabeculation or a constricting ring (eight), a 'spinning-top' urethra (three), urethral notching (two) and Mercier's bar (one). In group 2, five patients had no abnormal findings on VCUG and three had suspicious signs. The positive predictive value of VCUG was high (0.89) but the diagnostic yield of suspicious signs was low, because the sensitivity (0.5), specificity (0.62) and overall accuracy (0.52) were low. CONCLUSION: Radiological signs suspicious of DI cannot be regarded as such in conventional VCUG, as although they were detected in half the patients with DI, they also occurred in three of eight children with a stable bladder.