The most common cause of children chronic constipation is functional disorders. Functional constipation is diagnosed after excluding organic causes of constipation (anatomical, neurological, endocrinological) and identification of two symptoms defined by the Rome III criteria. There could be low number of bowel movements (below three times a week), defecation pain, fecal incontinence (once a week), stool consistency or occurrence of large diameter stools. The treatment is change of diet, defecation training and application of laxatives.

The probiotics are defined as living microorganisms, which provided in a proper doses should result in beneficial effect on a host health. The assessment of its characteristic is related to strain of bacteria affiliation.

Taking into the consideration that patients with constipation may experience microflora intestine disorders, using the probiotics can have the positive impact on process of treating this disease. The additional reason for using the probiotics during the constipation treatment is an influence of probiotics on movement of the alimentary canal.

In spite of proved effectiveness of some probiotics' strains further research are required, because clinical significance is ambiguous and the effect is confirmed among patients with short medical history. That's way the further analysis of probiotic Lactobacillus reuteri DSM 17938, which was successful treatment method of chronic constipation amongst children (infants) should be performed.

The primary aim of the study is the assessment of Lactobacillus reuteri DSM 17938 efficacy, provided with macrogol (Forlax), as treatment of constipation in 3-7 years old children. The baseline of estimation is the frequency comparison of bowel movement in children belonging into two groups: Lactobacillus reuteri treatment and placebo.

The secondary aim of the study is the assessment of frequency the additional symptoms connected with defecation disorders: such as: number of pain episodes during defecation, the intensity of pain, number of hard stools, number of fecal incontinence per week, number of macrogol (Forlax) pockets used.

The investigators believe that constipation treatment (laxatives- macrogol) with Lactobacillus reuteri has better efficacy that the same treatment without Lactobacillus reuteri in 3-7 years old children with medical history of chronic constipation.

Inclusion Criteria:

• Children 3-7 years old
• Occurrence less than three bowel movement per week
• Medical history from at least two months]
• Ineffective laxative treatment at least two months
• The parents approval for child participation in the study and for the treatment

Exclusion Criteria:

• Well-known, organic cause of constipation (i.e. hypothyroidism, Hirschprung disease, cystis fibrosis)
• Anatomic defects of the alimentary canal
• The surgery of the alimentary canal in the past
• Treatment of antibiotics/probiotics during last two weeks before start of the study