Radiographic Procedures · ARRT 2025
Lower GI Barium Enema
The 60 cm enema bag limit, Sims position and the 7.5 to 10 cm tip rule, which obliques open each colic flexure, and the 30 to 40 degree axial angle for the rectosigmoid.
Overview
The barium enema runs the upper GI playbook in reverse: contrast enters at the rectum and moves retrograde to the cecum, filling rectum, sigmoid, descending, transverse, ascending, and cecum in that order. On the ARRT Radiography exam this chapter lives in Procedures, the largest domain at 72 of 200 scored questions, and many of its questions are about the procedure itself rather than the positioning.
The numbers to bank first: the enema bag hangs no higher than 60 cm (24 inches) above the table, the tip goes in with the patient in Sims position (left side down, leaning forward) and never past 7.5 to 10 cm (3 to 4 inches) total, and single contrast runs 110 to 125 kV while double contrast drops to 90 to 100. Never force the tip. The rectum carries two anteroposterior curves, and forcing the tip at the wrong angle can cause serious injury.
Positioning turns on two systems. The obliques rotate 35 to 45 degrees, and anteriors match their letter while posteriors swap: RAO and LPO open the right colic (hepatic) flexure, LAO and RPO open the left. The axial projections carry the chapter's only tube angle, 30 to 40 degrees, cephalad on a supine patient and caudad prone, to elongate the rectosigmoid, where most carcinomas of the large intestine occur. Double contrast questions come down to gravity: air rises into the anterior sections, so a supine patient shows an air-filled transverse colon and a prone patient the reverse.
The chapter closes with the postevacuation image at 90 to 100 kV, defecography, the colostomy barium enema, and the pediatric study, where latex tips and inflatable balloon retention tips are both banned outright.
What you’ll learn in this chapter
The 35 lessons in this chapter break down as follows. The full lesson content is unlocked when you start a free account.
Lower GI
- Lower Gastrointestinal: the Barium Enema
Anatomy
- The Large Intestine, in Order
- Cecum, Appendix, Rectum and Anal Canal
- Where the Air Goes and Where the Barium Goes
- Quiz
Small bowel
- The Small Bowel Series
Clinical indications
- What the Barium Enema Is Looking For
Preparation
- Bowel Preparation
Equipment
- The Room, the Tips and the Mixture
Procedure
- Sims Position, the Tip, and Fluoroscopy
- Quiz
Contrast
- Single Contrast and Double Contrast
- Quiz
Projections
- PA and AP Barium Enema
- The Anterior Obliques
- The Posterior Obliques, and Which Flexure Opens
- Quiz
- Lateral Rectum and the Ventral Decubitus Lateral
- Right and Left Lateral Decubitus
- Quiz
- The Projections That Need a Tube Angle
- Quiz
- Postevacuation, and What Happens After
Special procedures
- Defecography and the Colostomy Barium Enema
Pediatrics
- The Pediatric Barium Enema and Intussusception
- Quiz
Summary
- Every Barium Enema Projection in One Place
Image critique
- Critiquing a Barium Enema
- Quiz
Recap
- What to Carry Out of This Chapter
- Quiz
- Quiz
- Quiz
- Quiz
- Quiz
Key terms in this chapter
These are the 8 terms most likely to appear on the ARRT registry from this chapter. Use them as a flashcard pre-quiz.
- Sims Position
- The insertion position: patient on the left side, leaning forward, right knee flexed in front of the left leg. It relaxes the abdominal muscles before the enema tip goes in on expiration.
- Enema Bag Rule
- The bag hangs no higher than 60 cm (24 inches) above the table before the procedure begins. Only the radiologist raises it during the study, based on the rate of flow.
- Double Contrast
- Thick barium at 75 to 95 percent weight to volume coats the mucosa while air distends the lumen. The recommended study for polyps, diverticula, and mucosal change.
- Colic Flexures
- The two bends of the colon. The right colic (hepatic) flexure sits lower because of the liver; RAO and LPO open it, while LAO and RPO open the higher left colic (splenic) flexure.
- Rectosigmoid
- The region where most carcinomas of the large intestine occur. The axial projections angle the central ray 30 to 40 degrees to elongate it and separate the overlapping sigmoid loops.
- Lateral Decubitus Pair
- Right and left lateral decubitus projections taken with a horizontal beam during double contrast studies. Each lifts one half of the colon so its mucosa fills with air.
- Postevacuation Image
- The final radiograph, taken at 90 to 100 kV after the patient empties the bowel. The residual mucosal coating is what shows small polyps and defects.
- Intussusception
- One length of bowel telescoping into another, most common in infants under 2. An air enema under fluoroscopy can both diagnose it and treat it by pneumatic reduction.
Sample practice question: Thorax and Abdomen
One free sample from the 75-question Thorax and Abdomen bank. See the format, the rationale style, and the difficulty before you sign up.
On a properly positioned and exposed PA chest radiograph in an adult, how many posterior ribs should be visible above the diaphragm to indicate adequate inspiration?
Show answer and rationale
A, Incorrect: 8 posterior ribs typically indicates underinspiration. Repeat with full inspiration.
B, Correct: Correct. The standard is at least 10 posterior ribs visible above the diaphragm on a properly inspired adult PA chest. Underinspiration (only 8 visible) compresses lung markings and may mimic pulmonary disease.
C, Incorrect: Counting anterior ribs is less reliable because they're more variable and angle differently. Use posterior ribs as the standard.
D, Incorrect: Costophrenic angle visibility is part of quality assessment but does not specifically indicate inspiration adequacy.
Read 3 chapters free.
The free tier unlocks 3 complete chapters, 50 practice questions, and 1 sample timed exam. No credit card required.
Frequently asked questions
What does the ARRT Radiography Radiographic Procedures category cover?
The barium enema runs the upper GI playbook in reverse: contrast enters at the rectum and moves retrograde to the cecum, filling rectum, sigmoid, descending, transverse, ascending, and cecum in that order. On the ARRT Radiography exam this chapter lives in Procedures, the largest domain at 72 of 200 scored questions, and many of its questions are about the procedure itself rather than the positioning.
How many lessons are in the Lower GI Barium Enema chapter?
This chapter contains 35 lessons across 14 sections, plus a knowledge-check quiz at the end. The full lesson content is unlocked with a Premium subscription. The free tier includes 3 complete chapters.
Is this chapter aligned with the ARRT 2025 Content Specifications?
Yes. Every chapter on this site maps directly to the ARRT Radiography Content Specifications effective 2025. This chapter falls under the Radiographic Procedures domain of the official ARRT exam blueprint.