Abdomen Lateral Decubitus is a radiography positioning projection of the Abdomen. Lateral recumbent, CR perpendicular at 2 inches above iliac crest. SID 40". The centering point is located 2 inches above iliac crest at midline.. The central ray is perpendicular to ir at 2 inches above iliac crest at midline.. Image-quality criteria include entire abdomen shown from diaphragm to pelvis., dependent (lower) side clear of table edge.. Standard exposure ranges from 75 to 85 kVp, 30 to 60 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Entire abdomen in true lateral projection.
- Air-fluid interfaces visible laterally.
- Free air lucency if pneumoperitoneum present.
- Bowel loops layered against dependent side.
- Liver silhouette against dependent side.
- Peritoneal fat stripe.
Patient preparation
- Verify patient identity using two identifiers.
- Remove all radiopaque objects from abdomen.
- Position patient lateral recumbent on left or right side.
- Keep back straight, not leaning forward or backward.
- Place arms out of field or across chest.
Position & centering point
2 inches above iliac crest at midline.
Central ray
Perpendicular to IR at 2 inches above iliac crest at midline.
Exposure / technique
- kVp
- 75–85
- mAs
- 30–60
- SID
- 40" (102 cm)
- Notes
- Grid required. Patient lateral recumbent on horizontal IR.
Image-quality criteria
- Entire abdomen shown from diaphragm to pelvis.
- Dependent (lower) side clear of table edge.
- Free air visible as lucency against dependent side if present.
- Air-fluid levels shown in true lateral view.
- Spine shown in profile along posterior margin.
- Bone trabeculae and soft tissue sharp throughout.
Common errors / ARRT traps
- 1 Patient leaning forward/backward alters lateral anatomy.
- 2 Dependent side touching table edge reduces image quality.
- 3 CR too high excludes lower abdomen and pelvis.
- 4 Patient motion during longer exposure blurs anatomy.
Clinical indications
- Free air detection (pneumoperitoneum evaluation).
- Bowel obstruction assessment with lateral air-fluid levels.
- Abdominal pain with patient unable to stand.
- Supine patient positioning alternatives.
Aligned to the 2025 ARRT Content Specifications.