Colonic transit times and the effect of lactulose or lactitol in hospitalized patients

To investigate whether a small dose (10 g per day) of a laxative (liquid lactulose, crystallized lactulose, or crystallized lactitol) can prevent the slow colonic transit associated with the physical inactivity of hospitalization.

Patients were randomly allocated to one of four groups: control, liquid lactulose, crystallized lactulose or crystallized lactitol, and the average of mean colonic transit times in these groups was compared.

Gastroenterologic Unit, Hospital dos Covoes, Coimbra, Portugal.

Patients with normal bowel movements, admitted to hospital for the investigation of conditions not associated with constipation or diarrhoea, were allocated to one of the four treatment groups and had their mean colonic transit times studied after hospitalization using radiopaque markers and abdominal radiographs. Each study group had 18 patients. During the study, each patient was given a normal diet and no drugs except the relevant laxative.

The average of the mean colonic transit times in each of the four groups were: 52.16 h [95% confidence interval (CI) 39.42-64.84] for controls; 22.45 h (95% CI 13.84-31.06) in the liquid lactulose group; 24.05 (95% CI 12.13-35.97) in the crystallized lactulose group; and 35.95 (95% CI 23.82-48.08) in the crystallized lactitol group. The differences were statistically significant for the two lactulose groups. The study of the mean colonic regional transit times showed that these differences related to transit in the right colon.

A small dose of lactulose (either liquid or crystallized) was effective in preventing slow colonic transit and constipation in hospitalized patients without causing unwanted symptoms. The slow transit affected mainly the right colon, and it was in this region that the laxative had effect.