Simultaneous urodynamic and anorectal manometry studies in children: insights into the relationship between the lower gastrointestinal and lower urinary tracts

Abstract

Background: Children with urinary incontinence (UI) have associated functional constipation (FC) and fecal incontinence (FI). The physiology between lower urinary tract (LUT) and anorectum in children has not been elucidated.

Aims: Observe the effect of rectal distention (RD) on LUT function, and bladder filling and voiding on anorectal function.

Methods: Children with voiding dysfunction referred to Boston Children's Hospital were prospectively enrolled in combined urodynamic (UDS) and anorectal manometry (ARM). Anorectal and urodynamic parameters were simultaneously measured. Patients underwent two micturition cycles, first with rectal balloon deflated and second with it inflated (RD). Lower urinary tract and anorectal parameters were compared between cycles.

Key results: Ten children (seven UI, four recurrent UTIs, nine FC ± FI) were enrolled. Postvoid residual (PVR) increased (p = 0.02) with RD. No differences were observed in percent of bladder filling to expected bladder capacity, sensation, and bladder compliance with and without RD. Bladder and abdominal pressures increased at voiding with RD (p < 0.05). Intra-anal pressures decreased at voiding (p < 0.05), at 25% (p = 0.03) and 50% (p = 0.06) of total volume of bladder filling.

Conclusions & inferences: The PVR volume increased with RD. Stool in the rectum does not alter filling cystometric capacity but decreases the bladder's ability to empty predisposing patients with fecal retention to UI and UTIs. Bladder and abdominal pressures increased during voiding, demonstrating a physiological correlate of voiding dysfunction. Intra-anal pressures decreased during bladder filling and voiding. This is the first time intra-anal relaxation during bladder filling and voiding has been described.

Keywords: anorectal manometry; bowel and bladder dysfunction; children; constipation; fecal incontinence; urodynamics; voiding dysfunction.

FIGURE 1

A: Study Protocol consisting of 3 phases (Standard UDS, ARM, UDS with rectal balloon inflation). Standard UDS: Following placement of urodynamic and anorectal catheters 1^st bladder filling was started with rectal balloon deflated and cystometric and abdominal pressures measured to obtain subtracted detrusor pressure. ARM: After the patient voided and the bladder was emptied standard ARM was performed with serial balloon distensions. The smallest volume during the serial balloon inflation that produced the maximum IAS relaxation but a minimum of 60mL, if tolerated, was used for each patient. If the patient experienced pain, the volume of maximum relaxation for that specific patient for rectal distention was used during the 2^nd filling phase of the study. UDS with rectal balloon inflation: After rectal balloon inflation the 2^nd filling phase was begun with the same pressure recordings obtained. B: Customized interface where urodynamic and intra-anal pressure parameters are simultaneously depicted. This allows the dynamic changes in pressures between the bladder and the anorectum as the bladder is filled, during the act of voiding, and with distention of the rectal balloon to be seen. After total volume of bladder filling was completed in each patient, the volume was divided into 4 quartiles and cystometric and anorectal pressures were noted at the end of each quartile. Start of filling is represented at 0%, 25% as 1^st quartile, 50% as 2^nd quartile, 75% as 3^rd quartile, and 100% as 4^th quartile as maximum volume of instilled water.

FIGURE 1

A: Study Protocol consisting of 3 phases (Standard UDS, ARM, UDS with rectal balloon inflation). Standard UDS: Following placement of urodynamic and anorectal catheters 1^st bladder filling was started with rectal balloon deflated and cystometric and abdominal pressures measured to obtain subtracted detrusor pressure. ARM: After the patient voided and the bladder was emptied standard ARM was performed with serial balloon distensions. The smallest volume during the serial balloon inflation that produced the maximum IAS relaxation but a minimum of 60mL, if tolerated, was used for each patient. If the patient experienced pain, the volume of maximum relaxation for that specific patient for rectal distention was used during the 2^nd filling phase of the study. UDS with rectal balloon inflation: After rectal balloon inflation the 2^nd filling phase was begun with the same pressure recordings obtained. B: Customized interface where urodynamic and intra-anal pressure parameters are simultaneously depicted. This allows the dynamic changes in pressures between the bladder and the anorectum as the bladder is filled, during the act of voiding, and with distention of the rectal balloon to be seen. After total volume of bladder filling was completed in each patient, the volume was divided into 4 quartiles and cystometric and anorectal pressures were noted at the end of each quartile. Start of filling is represented at 0%, 25% as 1^st quartile, 50% as 2^nd quartile, 75% as 3^rd quartile, and 100% as 4^th quartile as maximum volume of instilled water.

FIGURE 2. Post Void Residual (PVR) volume with and without RD

There was an increase in PVR volumes with RD.

FIGURE 3. Bladder pressures (PVes) and abdominal pressures (PAbd) with (solid line) and without (staggered line) RD at different quartiles of bladder filling and during voiding

Decline in bladder pressures at 75 % of bladder filling (3^rd quartile) when the rectum was distended (P=0.047). Increase in bladder (P=0.04) and abdominal (P=0.047) pressures during voiding with RD. □ - abdominal, ** - bladder

FIGURE 4. Intra-anal pressures with (solid line) and without (staggered line) (RD) at different quartiles of bladder filling and during voiding

During bladder filling there was an overall decrease in intra-anal pressures from start of bladder fill to void, with and without RD. ^{^}- significant difference in IAS pressures during bladder filling and voiding with and without RD. * - significant difference in IAS pressures from start of bladder fill to different quartiles of bladder fill and during voiding when the rectum is not distended. + - significant difference in IAS pressures from start of bladder fill to different quartiles of bladder fill and during voiding when the rectum is distended.