Identification of functional defecation disorder in patients with constipation based on colonic transit test: a retrospective study.

Background: This study aims to evaluate the diagnostic efficacy of colonic transit test (CTT) in cases of constipation associated with functional defecation disorders (FDD) within the Chinese population.

Methods: A retrospective analysis was conducted involving 202 patients diagnosed with functional constipation, who underwent CTT, high-resolution anorectal manometry, and balloon expulsion test. Participants were categorized based on the Rome IV criteria, comprising 103 patients with FDD and 99 without. The study examined the symptomatic characteristics of both groups and assessed the diagnostic utility of CTT in identifying constipation with FDD.

Results: The predominant symptom reported among individuals with chronic functional constipation was excessive straining, observed in 69.3% of cases. The incidence of hard stool passage and feelings of incomplete evacuation were significantly greater in the FDD group compared to the non-FDD group (47.6% vs. 31.3%,  = 0.018 and 50.5% vs. 25.3%,  = 0.001, respectively). The presence of three or more rectosigmoid (RS) residual markers and a transit index of 40% or greater demonstrated moderate diagnostic value for FDD, characterized by low sensitivity(44.7% and 47.6%) but high specificity(76.8% and 75.8%). The RS residual markers were effective in differentiating between FDD and normal transit constipation, but not effectively distinguish between FDD and slow transit constipation.

Conclusions: The presence of RS residue serves primarily as an exclusionary criterion for diagnosing FDD. In cases of slow transit constipation, but not normal transit constipation, it is imperative to conduct multiple kinetic assessments to accurately differentiate between FDD and other types of constipation.