- Recruitment based on simplified core ROME III diagnostic criteria for functional constipation (based on specific screening questions):a). average Bristol stool type of 1 - 4 AND frequency of 1 - 3 spontaneous bowel movements (SBMs) per week b). plus at least ONE of: straining on at least 25% of defaecations; sensation of incomplete evacuation on at least 25% of defaecations; sensation of anorectal obstruction / blockage on at least 25% of defaecations; use of manual manoeuvres on at least 25% of defaecations