Constipation is the most common complaint in childhood gastrointestinal disease, affecting an estimated 20% of the global children.The treatment strategies consist of diet control, behavioral intervention and oral and sometimes rectal laxatives. Given higher success rate and fewer side effects, the laxative PEG3350 has been considered the first choice in childhood constipation.However, effectiveness of PEG 3350 laxative is not lasting, and the use of PEG increases the risk of fecal incontinence. Additional treatment interventions are still necessary.Enema can act directly on the rectum and distal colon to quickly relieve symptoms of fecal impaction which is considered one of main source of intractable constipation. Children with fecal impaction who received enema had fewer fecal incontinence and diarrhea than children who received PEG. There have been lots of evidence that enema is effective in fecal impaction in children with functional constipation.But there are still cases of recurrences noted after enema. Fecal bacteria transplantation (FMT) is a new treatment method emerging in recent years, which is widely used in the treatment of functional gastrointestinal diseases. FMT has been proved to play a very prominent role in correcting intestinal flora disorders. By transplanting exogenous flora into the intestinal tract of patients, FMT can inhibit bacterial reproduction, regulate intestinal environment and cascade the body immunity, so as to achieve the therapeutic effect of disease.

Retrograde colonic enema with FMT, an new method, provides the possibility for the treatment of childhood constipation. However, there is still a lack of evidence-based support for the treatment of childhood constipation by retrograde colonic enema with FMT. Therefore, we designed a randomized, controlled, double-blind clinical trial to confirm the efficacy and safety of retrograde colonic enema with FMT in the treatment of childhood constipation.

Inclusion criteria:

• 4-14 years old;
• Roman IV criteria for childhood constipation;
• After a course of PEG and a course of Chinese medicine treatment was ineffective;
• Barium enema showing fecal impaction.

Exclusion criteria:

• Congenital and/or acquired intestinal diseases, such as congenital megacolon, intestinal stenosis, polyps, Crohn's disease, tuberculosis, inflammation, and tumors;
• Anorectal diseases, such as anal atresia, fistula, abscess, and tumor;
• Neurological diseases, such as brain and spinal cord diseases;
• genetic metabolic diseases;
• psychosocial and behavioral diseases;
• other systemic diseases;
• Refused to participate in.