Fecal impaction (FI) is a common cause of lower gastrointestinal tract obstruction, and it is the result of chronic or severe constipation and most commonly found in the elderly population. Gastrografin is a water soluble contrast mediate that could act as an osmotic laxative. It has been shown to confer a therapeutic benefit in adhesive small bowel obstruction (SBO). The investigators speculate that gastrografin administrated orally may be more effective than enema in the treatment of fecal impaction induced intestinal obstruction.

Inclusion Criteria:

1. A confirmed presence of fecal impaction diagnosed based on the following conditions: large amount of hard stool (impacted faecaloma) in colon or rectum; abdominal radiography was performed for assessment.
2. Rome III criteria for chronic constipation present for ≥8 weeks.

Exclusion Criteria:

1. Patients with a history of colorectal surgery or an organic cause of constipation; pregnancy.
2. Patients with long-term medical conditions potentially associated with constipation (ie, cystic fibrosis, cerebral palsy, hypothyroidism, spinal and gastric anomalies).
3. Patients with medical or psychiatric illness.
4. Patients with abnormal laboratory data or thyroid function.