Q1. Correct answer: B. Expulsion of water-filled balloon in 3 minutes.
Rationale
The balloon expulsion test is highly suggestive of dyssynergia. A balloon expulsion time of greater than 2 minutes is abnormal. An absent RAIR can be seen in Hirschsprung's disease or megarectum. Defecation index equals maximum rectal pressure during attempted defecation divided by minimum anal residual pressure during attempted defecation. A normal defecation index is greater than 1.5. Decreased anal sphincter pressure during simulated defecation is normal and therefore not consistent with dyssynergic defecation.
References
Wald A et al. Am J Gastroenterol. 2014 Aug;109(8):1141-57.
Bharucha AE et al. Gastroenterology. 2013 Jan;144(1):218-38.