AN EXAMINATION OF THE RELIABILITY OF REPORTED STOOL FREQUENCY IN THE DIAGNOSIS OF IDIOPATHIC CONSTIPATION

Objectives: To investigate the reliability of reported stool frequency in the diagnosis of constipation. Methods: Our criterion for the diag nosis of idiopathic constipation was less than or equal to 3 stools pe r week for greater than or equal to 6 months, Subjects who believed th at they met this criterion were invited to participate. Daily stool fr equency was recorded over a 4-wk study period, and all stools were wei ghed during the final week. A colon transit study and anorectal manome try were performed at the beginning and at the end of the study. Resul ts: On review of stool diaries from 45 subjects who described chronic constipation and who completed the 4-wk study, only 22 (49%) actually satisfied our criterion for idiopathic constipation. The remaining 23 (51%) subjects, although describing constipation, had, on average, 6 s tools/wk. A history of psychiatric illness was 5 times more frequent a mong those whose bowel symptoms correlated poorly with objective measu res. Measures of difficult defecation were similar in the two groups. Mean colon transit time was significantly longer and correlated closel y with stool weight only in subjects who truly were constipated (p < 0 .05). Anorectal manometry was not helpful in discriminating between th ose who satisfied our criterion for constipation and those who did not . Conclusions: Defining constipation on the basis of a patient)s repor ted stool frequency may prove misleading; the diagnosis of idiopathic constipation should be supported by the use of stool diaries and a col on transit study.