Anorectal Manometry and Balloon Expulsion Testing in Chronic Constipation: Concordance, Manometric Predictors of Dyssynergic Defecation, and Implications for Biofeedback Referral
Orrin Wilson, Jason Goldenberg, Zachary Wilmer Reichenbach, Henry P. ParkmanABSTRACT
Background
Anorectal manometry (ARM) and the balloon expulsion test (BET) are recommended for evaluating dyssynergic defecation, but neither is a reference standard. We quantified ARM‐BET concordance across four categories defined by the Rao pattern and BET result and tested whether continuous physiologic measures predict BET better than the Rao classification.
Methods
We reviewed 133 consecutive high‐resolution ARM studies (modified London Protocol) in patients referred for chronic constipation. Seated BET (50 mL, abnormal > 60 s) followed ARM. Concordance used Cohen's kappa and McNemar's test. The rectoanal gradient and defecation index were tested against BET, and multivariable regression against dyssynergic pattern.
Key Results
Of 133 patients (100 women, mean age 46), 84 (63%) had a dyssynergic pattern and 54 (41%) a prolonged BET. Agreement was slight (56%, kappa 0.17): 30% were abnormal on both tests, 44% on one test, and 26% normal on both. The rectoanal gradient predicted abnormal BET better than the Rao classification; among dyssynergic‐pattern patients an abnormal BET was associated with a more negative gradient (−29 vs. −3 mmHg, p = 0.001). Lower resting anal sphincter pressure was independently associated with the dyssynergic pattern (adjusted odds ratio 0.50 per 10 mmHg) but not BET. Biofeedback improved symptoms in 19 of 21 patients.
Conclusions and Inferences
ARM‐BET agreement is slight, and either test alone misclassifies patients. Continuous physiologic measures discriminate evacuation better than the Rao classification and account for much of the discordance. Lower resting pressure characterizes the dyssynergic phenotype without predicting evacuation. Biofeedback response was high if either test was positive.