Detrusor after-contraction: a new insight

Abstract

Aims: Detrusor after-contractions (DAC) are non-common in adults. Both definition (nothing in ICS reports) and significance (artefact, link with detrusor overactivity (DO) or bladder outlet obstruction (BOO)) remain discussed. Our purpose was to carry out an analysis of the urodynamic parameters during voidings with DAC and, using the VBN model, to simulate pathophysiological conditions able to explain both voiding phase and DAC.

Materials and methods: From large urodynamic database of patients referred for evaluation of lower urinary tract dysfunction, DAC were observed in 60 patients (5.7%). Criteria for DAC were post-void residual <30mL and increase of detrusor pressure >10cmH(2)O. VBN model was used for analysis of both pressure and flow curves, and simulations of pathophysiological conditions.

Results: Onset of DAC (ODAC) occurred when Q=7.3±5.7mL/s and bladder volume=17.9±15.4mL. Urgency-frequency syndrome and urodynamic diagnosis of DO were the more frequent scenarios associated with DAC. ODAC was associated to an inversion of the slope of detrusor pressure curve without any perturbation in flow curve. Among tested pathophysiological hypothesis (great, abnormal, detrusor force, sphincter contraction), none allowed restoring all recorded curves (flow rate, voiding pressure and DAC).

Conclusion: No urodynamic characteristic of the first part of voiding is an index of occurrence of DAC. ODAC is a significant phenomenon linked with the bladder collapse. DAC is not associated with BOO but more probably with DO and appears as the result of local conditions in an almost empty bladder (concentration of stresses around a transducer); thus DAC seems of weak clinical significance.

Figure 1. Recording of a typical example of detrusor after-contraction (DAC) observed during intubated flow of a female patient. From top to bottom: detrusor pressure (p_det), urethral pressure (p_ura), vesical pressure (p_ves), rectal pressure (p_rec) and flow rate (Q). Note the high amplitude of DAC compared with pdet during voiding.

Figure 2. Four examples of VBN analysis of voidings followed by detrusor after-contraction (DAC) in female patients. The description only concerns the lower register (flow and pressures): Q (recd) (red)= recorded Q; Q (comp) (blue)= computed Q; p_det (recd) (fuchsia)= recorded p_det; p_det (comp) (grey) =computed p_det; p_abd.eff (comp) (green) = computed p_abd.eff.