There are different types of enema:  single or double contrast barium enema and water-soluble contrast enema.

Guidelines for Choosing the Type of Enema to Perform

• Rectal bleeding - gross or occult
• Polyps or carcinoma - suspected or known
• Inflammatory bowel disease - suspected or known
• Patient over 40 years of age who can cooperate and turn over without assistance

Indications for single contrast barium enema:

• Patient under 40 years of age with abdominal signs or symptoms not suggestive for polyps, colitis, or bleeding (i.e., pain only, bloating only) 
• Suspected diverticulitis   
• Bowel not prepared but limited exam requested to verify or exclude obstruction, volvulus, appendicitis, fistula, etc.   
• Uncooperative, disabled, very old, or very ill patient unable to tolerate or perform the maneuvers required for a double contrast study

Contraindications to barium enema of any type:

• Suspected acute perforation 
• Acute, fulminating colitis
• Immediately after biopsy

Indications for water-soluble contrast enema:

• Suspected perforation or high risk for intestinal perforation  
• Therapeutic enema for disimpaction (after failure of routine cleansing enemas)