Identifying low bladder compliance before renal transplant: cystometrogram versus cystogram.

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Background:
End Stage Renal Disease (ESRD) patients with low compliance bladders may be at risk for graft failure. Current screening methods for identifying low bladder compliance in this population include cystometrogram and cystography. We evaluated ESRD for low bladder compliance using both cystometrogram pressures and cystography and compared detection rates.
Methods:
ESRD patients awaiting renal transplant were prospectively screened for history of urologic anatomic abnormalities, urine output < 300cc/24 hour, symptoms of lower urinary tract dysfunction (> 6 voids/ 3 hours), or low capacity (> 6 voids/ 3hours, capacity < 200 cc). Complex cystometrogram (CMG) and voiding pressure studies were performed using a standardized urodynamic protocol. A voiding cystourethrogram (VCUG) using anterior/posterior and lateral views were also performed during the testing. Bladder compliance was calculated as infused volume over change in bladder detrusor pressure (cc/cm H20) and low compliance was defined as < 20 cc/cm H20 change during the filling phase on CMG. Bladder outlet obstruction was defined as voiding pressures > 40 cm H20 and a maximum urinary flow rate of < 10 cc/ second. VCUG studies with evidence of bladder diverticulum or vesico-ureteral reflux before an infused volume of <100 cc were defined as low compliance studies.
Results:
Thirty seven studies were performed on 35 patients (28 males, 7 females). Mean age was 57 years (Range 23 73). Median bladder compliance was 10 cc/cm H20 (Mean = 34.2 cc/cm H20; Range 0.3 - 200.0 cc/ cm H20), with 23 of the 37 studies (62%) meeting the CMG low compliance definition. In addition, bladder outlet obstruction was diagnosed in 14 patients during voiding pressure evaluation. When using the cystogram criteria for low bladder compliance, only 13 of 37 studies (35%) demonstrated low compliance findings, three of which did not meet CMG criteria for low bladder compliance. Median bladder compliance of the 13 abnormal VCUG studies was 9.3 cc/cm H20 (Mean = 33.9, Range 0.3- 100 cc/ cm H20). Compared to CMG criteria, cystogram showed a 56% sensitivity and 82% specificity for detecting low bladder compliance. Bladder outlet obstruction could not be objectively determined on any voiding cystourethrogram.
Conclusions:
Cystometrogram testing was superior to VCUG alone in identifying patients at risk for low bladder compliance. These data suggest that urodynamics may be helpful in pretransplant planning for selected patients.

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