Short pelvic floor electromyographic lag time: a novel noninvasive approach to document detrusor overactivity in children with lower urinary tract symptoms.

PURPOSE

Noninvasive uroflow with simultaneous electromyography can measure electromyographic lag time, ie the interval between the start of pelvic floor relaxation and the start of urine flow (normally 2 to 6 seconds). Intuitively one would expect that in patients experiencing urgency secondary to detrusor overactivity the lag time would be short or even a negative value. We studied whether short electromyographic lag time on uroflow with electromyography actually correlates with documented detrusor overactivity on urodynamics.

MATERIALS AND METHODS

We reviewed 2 separate and distinct cohorts of 50 neurologically and anatomically normal children with persistent lower urinary tract symptoms who were evaluated by uroflow with simultaneous electromyography and videourodynamics. Group 1 consisted of 30 boys and 20 girls (mean age 7.8 years, range 4 to 19) selected based on electromyographic lag time of 0 seconds or less on screening uroflow with electromyography who subsequently underwent videourodynamics. Group 2 consisted of 14 boys and 36 girls (median age 8.4 years, range 5 to 18) selected based on the presence of detrusor overactivity on videourodynamics whose screening uroflow with electromyography was then reviewed. Correlations between short electromyographic lag time and videourodynamically proved detrusor overactivity were analyzed.

RESULTS

For group 1 urodynamics confirmed the presence of detrusor overactivity in all patients with an electromyographic lag time of 0 seconds or less. For group 2 mean ± SD electromyographic lag time was 0.1 ± 1.7 seconds, and 35 patients (70%) with urodynamically proved detrusor overactivity had a lag time of 0 seconds or less.

CONCLUSIONS

In patients with lower urinary tract symptoms an electromyographic lag time of 0 seconds or less is 100% predictive of detrusor overactivity. This short electromyographic lag time has 100% specificity and 70% sensitivity for diagnosing detrusor overactivity (88% if less than 2 seconds). Thus, diagnosing the presence or absence of detrusor overactivity in most children with lower urinary tract symptoms and a quiet pelvic floor during voiding can be done reliably via uroflow with simultaneous electromyography.