Radiographic Procedures · ARRT Radiography
Abdomen Radiography
Covers the KUB centered at the iliac crest, erect and decubitus views 5 cm above it, the 5-minute upright rule, and the three-image acute abdomen series with a PA chest.
Overview
The abdomen chapter is built around one routine projection and the reasons it is not enough. The AP supine abdomen, better known as the KUB, is centered at the iliac crest with the bottom margin at the symphysis pubis and exposed at the end of expiration. Procedures is the largest content category on the ARRT Radiography exam, at 66 of 200 scored questions to 28 February 2027, 72 from 1 March 2027. For each abdomen projection, learn three things: where the central ray goes, what the image must include, and what the patient does with their breath.
Much of what follows the KUB exists because air-fluid levels need a horizontal beam and free air shows best with one. Gas rises and fluid settles, and neither draws a visible line unless the central ray runs along that boundary. That is why the erect and decubitus projections use a horizontal beam centered about 5 cm (2 inches) above the crest to include the diaphragm, and why the patient must be upright or on their side for a minimum of 5 minutes, 10 to 20 minutes preferred, before the exposure.
The chapter also covers the left lateral decubitus, taken left side down so free air rises over the liver on the raised right side away from the gastric bubble, and the dorsal decubitus, the answer when an ICU patient cannot be rolled at all. The acute abdomen series is three images: AP supine, AP erect, and a PA chest, included because chest technique shows the smallest amounts of free air under the diaphragm.
Rounding it out: quadrants and the nine regions, intraperitoneal versus retroperitoneal organs, seven palpable landmarks with the iliac crest at L4-L5, and pathology from pneumoperitoneum to volvulus, plus the 2027 additions of ingested foreign bodies and gastric tube placement.
What you’ll learn in this chapter
The 32 lessons in this chapter break down as follows. The full lesson content is unlocked when you start a free account.
Abdomen
- Abdominal Radiography
Anatomy
- Quadrants and the Nine Regions
- The Peritoneum
- Quiz
- The Organs Inside the Abdomen
- The Kidneys and Their Level
- Quiz
Landmarks
- Seven Palpable Landmarks
Technique
- Technique, Shielding and Breathing
Projections
- AP Supine Abdomen
- Quiz
- AP Erect Abdomen
- Quiz
- PA Prone and Lateral
Decubitus
- Left Lateral Decubitus
- Quiz
- Dorsal Decubitus
- Quiz
Acute abdomen
- The Acute Abdomen Series
- Quiz
- Free Air and Air-Fluid Levels
Foreign bodies
- Foreign Bodies and Tube Placement
- Quiz
Clinical indications
- Pathology on a Plain Abdomen
Image critique
- Critiquing an Abdomen Film
- 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.
- KUB
- The AP supine abdomen, named for kidneys, ureters, and bladder. Centered at the iliac crest with the bottom margin at the symphysis pubis, exposed at the end of expiration.
- Acute Abdomen Series
- Three images: AP supine abdomen, AP erect abdomen, and a PA chest. The chest is included because chest exposure technique best shows small amounts of free air under the diaphragm.
- Pneumoperitoneum
- Free air in the peritoneal cavity, most often from a perforated stomach or bowel, such as a gastric or duodenal ulcer. On an erect image it appears as a thin crescent-shaped lucency under the right hemidiaphragm.
- Air-Fluid Level
- A flat horizontal interface where gas sits on top of liquid inside a bowel loop. It signals obstruction or ileus and only appears with a horizontal beam.
- Left Lateral Decubitus
- The patient lies on the left side so free air rises over the liver on the raised right side, away from the gastric bubble. Requires 5 minutes minimum on the side, 10 to 20 preferred.
- Dorsal Decubitus
- The patient stays supine while a horizontal beam crosses from one side to the other. The remaining horizontal beam option when a patient cannot be rolled at all.
- Retroperitoneal
- Behind the peritoneum, pinned to the posterior abdominal wall. Includes the kidneys, pancreas, C-loop of the duodenum, ascending and descending colon, and the aorta.
- Iliac Crest
- The most commonly used abdominal landmark, at the level of the L4-L5 vertebral interspace. The default centering point for the supine abdomen.
Sample practice question: Thorax and Abdomen
One free sample from the 285-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.
Hands-on
Practice the positioning
Open the Positioning Lab to drill body position, central ray, anatomy, and common errors for each projection in this chapter.
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Frequently asked questions
What does the ARRT Radiography Radiographic Procedures category cover?
The abdomen chapter is built around one routine projection and the reasons it is not enough. The AP supine abdomen, better known as the KUB, is centered at the iliac crest with the bottom margin at the symphysis pubis and exposed at the end of expiration. Procedures is the largest content category on the ARRT Radiography exam, at 66 of 200 scored questions to 28 February 2027, 72 from 1 March 2027. For each abdomen projection, learn three things: where the central ray goes, what the image must include, and what the patient does with their breath.
How many lessons are in the Abdomen Radiography chapter?
This chapter contains 32 lessons across 11 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 current ARRT Content Specifications?
Yes. Every chapter on this site maps directly to the ARRT Radiography Content Specifications in effect for your exam window. This chapter falls under the Radiographic Procedures domain of the official ARRT exam blueprint.