Validation of the Balloon Evacuation Test: Reproducibility and Agreement With Findings From Anorectal Manometry and Electromyography

BACKGROUND & AIMS: The balloon evacuation test (BET) measures the time required to evacuate a balloon filled with 50 mL water; it has been incorporated into many algorithms for diagnosis of pelvic floor dyssynergia. We aimed to assess the reproducibility of the BET, determine the upper limit of normal, and assess its concordance with evaluation of pelvic floor dyssynergia by anorectal manometry (ARM) and pelvic floor surface electromyography (EMG). METHODS: The BET was tested in 286 consecutive patients with chronic constipation (mean age, 44 years; 91% female) before and after 30 days of conservative treatment at a tertiary gastroenterology clinic in Italy from March 2010 through May 2012. The BET was tested twice, 7 days apart, in 40 healthy individuals (controls: mean age, 38 years; 92% female). The 238 constipated patients who responded incompletely to conservative therapy were examined by ARM, EMG, and digital rectal examination. Forty-seven patients with conflicting ARM and BET results underwent defecography. RESULTS: The balloon was evacuated within 1 minute by 37 controls (93%; 3 individuals required 1-2 minutes). Among patients with constipation, 148 (52%) passed the balloon within 5 minutes (110 passed the balloon in 1 minute, 35 passed it in 1-2 minutes, and 3 passed it in 2-5 minutes). The BET showed perfect reproducibility in 280 of the patients with constipation (98%) when a time less than 2 minutes was set as abnormal. The level of agreement between BET and ARM for dyssynergia was 78%, and between BET and EMG it was 83%. Thirty-two patients had abnormal results from the BET but normal results from ARM; 31 cases had inadequate straining (n = 11) or anatomic defects (n = 20), which could account for the abnormal findings from BET. CONCLUSIONS: The BET is reliable for analysis of pelvic floor dyssynergia; the optimal upper limit of normal is 2 minutes. Findings from the BET have a high level of agreement with those from ARM and EMG.