What is the purpose and procedure of a barium enema?

Barium Enema: Purpose and Procedure

A barium enema is a radiologic examination of the colon that has largely been replaced by more sensitive and less invasive procedures like colonoscopy and CT colonography (CTC) for colorectal cancer screening and diagnosis. 1

Purpose of Barium Enema

Barium enema serves several clinical purposes:

1. Colorectal cancer screening: Historically used as one option for colorectal cancer screening, though now considered less optimal than newer methods 1

2. Visualization of colonic abnormalities: Allows visualization of polyps, tumors, diverticula, and structural abnormalities of the colon 1

3. Alternative when colonoscopy is incomplete: May be used when colonoscopy cannot be completed to the cecum, though CT colonography is now preferred in this scenario 1

4. Total colon examination: Provides examination of the entire colorectum when performed as a double-contrast study 1

Types of Barium Enema

There are two main types:

1. Double-Contrast Barium Enema (DCBE):

   • Uses both barium and air to define the contours of the colorectal mucosa
   • More sensitive than single-contrast for detecting polyps and mucosal abnormalities
   • Sensitivity for detecting large polyps (≥10mm) is approximately 48% 1
   • Specificity for large polyps is about 90% 1

2. Single-Contrast Barium Enema (SCBE):

   • Uses only liquid barium without air insufflation
   • Markedly inferior performance compared to DCBE
   • Sensitivity for polyps <1cm is approximately 72% 1
   • Generally performed only when patients cannot tolerate DCBE

Procedure

The barium enema procedure involves:

1. Bowel preparation: Complete cleansing of the colon is required, typically involving dietary restrictions, laxatives, and enemas

2. Patient positioning: The patient lies on a fluoroscopy table and is repositioned throughout the examination to distribute the contrast material

3. Contrast administration:

   • A rectal tube is inserted, and barium sulfate suspension is instilled into the rectum
   • For DCBE, air is also insufflated to create the double-contrast effect 2

4. Imaging:

   • Fluoroscopy is used to guide the examination in real-time
   • Multiple spot images are obtained with the patient in different positions
   • The fluoroscopist analyzes the luminal contour, barium-coated mucosal surface, and barium pool to detect abnormalities 2

5. Post-procedure care: Patients are advised to increase fluid intake and may take mild laxatives to help eliminate the barium

Current Status in Clinical Practice

Barium enema has significantly declined in use due to:

1. Inferior sensitivity: Multiple studies show DCBE is less sensitive than colonoscopy and CTC for detecting polyps and cancer 1, 3

2. Inability to obtain biopsies: Unlike colonoscopy, barium enema is purely diagnostic and cannot remove polyps or obtain tissue samples 4

3. Patient discomfort: Often poorly tolerated by patients compared to modern alternatives 3

4. Better alternatives: Current guidelines favor colonoscopy or CTC over barium enema 1

5. Limited utility after incomplete colonoscopy: Studies show that repeat colonoscopy under deeper sedation is preferable to DCBE after an incomplete colonoscopy 5

Safety Considerations

Important safety issues with barium enema include:

1. Perforation risk: Though rare, colonic perforation can occur

2. Barium peritonitis: If perforation occurs during a barium study, barium can leak into the peritoneal cavity causing severe peritonitis 6

3. Aspiration risk: Barium can cause severe chemical pneumonitis if aspirated into the lungs 6

4. Contraindications: Should not be used when perforation is suspected; water-soluble contrast is safer in these situations 6

5. Imaging interference: Barium creates significant streak artifact, interfering with subsequent CT imaging 6

Current Recommendations

According to the most recent guidelines:

• Barium enema has fallen out of use with the emergence of CTC 1
• Clinical consensus and literature confirm that fluoroscopic modality is not as sensitive as CT-based examination 1
• The American College of Radiology no longer recommends DCBE as a backup examination for incomplete colonoscopy 1
• For colorectal cancer screening, colonoscopy and CTC are preferred over barium enema 1

In summary, while barium enema was historically an important tool for colorectal evaluation, its clinical utility has been largely superseded by more accurate and patient-friendly alternatives.