Functional constipation is a common condition in children and often requires prolonged maintenance treatment with macrogol. This randomized, double-blind, placebo-controlled trial will evaluate whether co-supplementation with Bifidobacterium longum W11 and Colopectin can support maintenance therapy in children with functional constipation who are receiving macrogol and are candidates for weaning. Participants aged 2 to 6 years will be randomized to receive either the active supplementation or placebo once daily for 4 weeks, followed by 4 weeks of follow-up after treatment discontinuation. The study will assess persistence of constipation after macrogol discontinuation, as well as stool consistency, distress during evacuation, soiling episodes, and treatment compliance.

Functional constipation is one of the most common gastrointestinal disorders in childhood and is frequently associated with painful or infrequent defecation, stool retention, and reduced quality of life. In many children, maintenance treatment with macrogol is required for prolonged periods, and gradual weaning may be clinically challenging. Therefore, supportive dietary or microbiota-targeted strategies that may facilitate maintenance management and discontinuation of macrogol are of clinical interest.

Bifidobacterium longum W11 is a probiotic strain with potential effects on intestinal function and motility, while Colopectin contains prebiotic and fiber-related components that may help support bowel regularity. The combination is being investigated as a co-supplementation strategy in children with functional constipation during the maintenance phase of treatment.

This study is a randomized, double-blind, placebo-controlled, parallel-group trial in children aged 2 to 6 years with functional constipation who have been receiving maintenance-dose macrogol for at least 3 months and are candidates for treatment weaning. A total of 100 participants will be randomized in a 1:1 ratio to receive either Bifidobacterium longum W11 (Bowell®) plus Colopectin (Colopectin®) or placebo, administered once daily between meals in the afternoon for 4 weeks. After the treatment period, supplementation will be discontinued and participants will be monitored for an additional 4 weeks.

Clinical assessments will be performed at baseline (T0), at Week 4 (T1), and at Week 8 (T2). The primary endpoint is persistence of constipation, defined as 2 or fewer bowel movements per week, after discontinuation of macrogol therapy. Secondary endpoints include changes in stool consistency assessed using the Bristol Stool Scale, presence or absence of distress during evacuation, number of soiling episodes, and treatment compliance.

Inclusion Criteria:

• Children aged 2 to 6 years
• Diagnosis of functional constipation
• Receiving maintenance therapy with macrogol for at least 3 months
• Candidates for weaning from macrogol therapy

Exclusion Criteria:

• Children with intestinal meteorism or flatulence
• Children diagnosed with organic constipation
• History of previous abdominal surgery
• Children with frailty or disabilities
• Presence of other organ diseases or syndromes

Participants, parents or guardians, care providers, investigators, and outcome assessors will remain blinded to treatment allocation. Active treatment and placebo will be provided in sachet form and administered according to the same schedule.