Colonic transit time in mentally retarded persons.

INTRODUCTION: Constipation is frequently seen in patients with mental retardation (MR). Its pathophysiology is poorly understood. Measurement of colon transit time (CTT) differentiates between retentive and non-retentive constipation. AIM: To determine total and segmental CTT in MR patients compared to healthy controls. METHOD: Of 250 residents, 60 patients older then 16, without swallowing disorder or scoliosis, are randomly chosen, 58 participated (intelligence quotient < 50, median age 35.5 year, 29 male). Constipation was defined as less than three defecations a week. Controls are 32 non-constipated age-matched healthy volunteers (median age 29 year, 19 male). CTT is measured by daily administration of ten radio-opaque markers during 6 days and abdominal X-ray on day 7. CTT is calculated using Bouchoucha's [7] method. RESULTS: Compared to controls, total CTT is significantly (P < 0.001) longer in MR (median 22.8 h vs. 57.6 h, respectively). Of the MR patients, 21/58 (36%) are constipated. The mental retardated and constipated (MRC) have a significant prolonged CTT in all segments (P < 0.01; median right CTT 19.2 h vs. 4.8 h; left CTT 14.4 h vs. 4.8 h; rectosigmoidal CTT 42 h vs. 9.6 h), whereas in mental retarded non-constipated (MRNC) persons, the rectosigmoidal CTT is prolonged (median 21.6 h vs. 9.6 h). CONCLUSION: Patients with moderate to deep MR have a significantly prolonged total CTT. In MRNC persons, rectosigmoidal CTT prolongation suggests a defecation problem. In MRC, CTT is prolonged in all segments, suggesting diffuse colonic inertia problem.