Phenotypic identification and classification of functional defecatory disorders using high-resolution anorectal manometry

Abstract

Background & aims: Disordered defecation is attributed to pelvic floor dyssynergia. However, clinical observations indicate a spectrum of anorectal dysfunctions. The extent to which these disorders are distinct or overlap is unclear; anorectal manometry might be used in diagnosis, but healthy persons also can have abnormal rectoanal pressure gradients during simulated evacuation. We aimed to characterize phenotypic variation in constipated patients through high-resolution anorectal manometry.

Methods: We evaluated anorectal pressures, measured with high-resolution anorectal manometry, and rectal balloon expulsion time in 62 healthy women and 295 women with chronic constipation. Phenotypes were characterized by principal components analysis of high-resolution anorectal manometry.

Results: Two healthy persons and 71 patients had prolonged (>180 s) rectal balloon expulsion time. A principal components logistic model discriminated healthy people from patients with prolonged balloon expulsion time with 75% sensitivity and a specificity of 75%. Four phenotypes discriminated healthy people from patients with abnormal balloon expulsion times; 2 phenotypes discriminated healthy people from those with constipation but normal balloon expulsion time. Phenotypes were characterized based on high anal pressure at rest and during evacuation (high anal), low rectal pressure alone (low rectal) or low rectal pressure with impaired anal relaxation during evacuation (hybrid), and a short anal high-pressure zone. Symptoms were not useful for predicting which patients had prolonged balloon expulsion times.

Conclusions: Principal components analysis of rectoanal pressures identified 3 phenotypes (high anal, low rectal, and hybrid) that can discriminate among patients with normal and abnormal balloon expulsion time. These phenotypes might be useful to classify patients and increase our understanding of the pathogenesis of defecatory disorders.

Figure 1

Representative high-resolution manometry tracings in constipated patients with (A) high PC1, (B) low PC3, (C) low PC4, or (D) low PC5 scores. (A) Higher PC1 scores were associated with 3 higher anal resting and squeeze pressures and higher anal pressure during simulated evacuation (dyssynergia). Rectal balloon pressure during simulated evacuation increased with (A) but not with (B) low PC3 score or (D) low PC5 score. Relative to rest, anal pressure increased during simulated evacuation in the patient with a (B) low PC3 score but not in the patient with a (D) low PC5 score. (C) A short high-pressure zone is the distinguishing feature in patients with low PC4 scores. The profile on the far right shows the location of the sensors in the anorectum for the example in panel D. BD, bear down (simulated evacuation); R, rest; and S, squeeze. Color scale shows pressure in mmHg

Figure 2

ROC curves showing the utility of anal manometric features for discriminating between: (1) control subjects and patients with normal balloon expulsion time (left panel) and (2) control subjects with normal balloon expulsion and controls or patients with prolonged balloon expulsion time.