Abdomino-anal Dyscoordination in Defecatory Disorders

The contribution of the abdominal muscles to normal defecation and disturbances thereof in defecatory disorders (DDs) are unknown.

In 30 healthy and 60 constipated women with normal rectal balloon expulsion time (BET) (n = 26) or prolonged BET (ie, DD; n = 34), seated anorectal pressures (manometry) and thickness (ultrasound) of the external and internal oblique and transversus abdominis muscles were measured simultaneously at rest, during hollowing, squeeze, evacuation, and a Valsalva maneuver.

Compared with healthy women with a normal BET, DD women had a lower rectal and greater anal pressure increase during evacuation (P ≤ .05), and more activation of the internal oblique and the transversus abdominis muscles during squeeze (P < .05). The change in transversus abdominis thickness during a Valsalva maneuver vs hollowing (rho = 0.5; P = .002) and separately vs evacuation (rho = 0.7; P < .0001) were correlated in DD but not in healthy women with a normal BET. A principal component (PC) analysis of anorectal pressures and muscle thicknesses during evacuation uncovered a PC (PC3) that was associated with a prolonged BET. Higher PC3 scores were associated with low rectal and high anal pressures at rest and during evacuation, thinner external oblique muscle, and thicker internal oblique muscle during evacuation. A greater PC3 score was associated with increased odds for DD vs health (odds ratio, 1.84; 95% CI, 1.05-3.23), and separately vs constipation with a normal BET (odds ratio, 3.64; 95% CI, 1.73-7.69).

Taken together, these findings show 3, possibly inter-related, disturbances suggestive of dyscoordination in DD: aberrant activation of abdominal muscles during squeeze in DD, dyscoordination of the abdominal muscles during various tasks in constipated women, and abdomino-anal dyscoordination.