BackgroundA subset of patients with chronic constipation display a relatively high manometric rectal pressure on strain. We hypothesized that these patients represent a unique phenotype of functional defecatory disorder (FDD) and would benefit from undergoing anorectal biofeedback (BF). MethodsOf 138 consecutive patients with chronic constipation and symptoms of FDD, 19 were defined as having a high rectal pressure on strain, using a statistically derived cut-off of 78mm Hg. This subset was compared with remaining patients in regard to baseline clinical profile and physiology, and outcome of BF. Key ResultsThere was a greater representation of males in the high rectal pressure group. Their constipation score, impact of bowel dysfunction on quality of life and satisfaction with bowel habits did not differ from the remaining patients. Eighty-four percent of patients in the high group successfully expelled the rectal balloon and 95% displayed paradoxical anal contraction on strain (P<.05 compared with the remaining patients). Following BF, 89% of patients in the high group reduced their rectal pressure to normal. End of BF treatment outcomes improved significantly, and to a similar degree, in both groups. Conclusions & InferencesWe have identified a subgroup of patients with dyssynergic symptoms but without a formal Rome III diagnosis of FDD, who were characterized by a high straining rectal pressure. Although these patients displayed some physiological differences to the patients with lower straining rectal pressure, they suffer similarly. Importantly, we have shown that these patients can respond favorably to anorectal BF.