Abdomen AP Supine (KUB) is a radiography positioning projection of the Abdomen. Supine, legs extended, arms at sides. SID 40". Standard KUB position. The centering point is located at the level of the iliac crest (l4), at midline.. The central ray is perpendicular to ir at the level of the iliac crest (l4), midline.. Image-quality criteria include entire abdomen visible from diaphragm to pubic symphysis., spine midline shown without rotation.. Standard exposure ranges from 70 to 80 kVp, 25 to 40 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Diaphragm and liver outline.
- Stomach and gastric bubble.
- Small bowel loops.
- Colon throughout abdomen.
- Psoas muscles.
- Kidney outlines.
Patient preparation
- Verify patient identity using two identifiers.
- Ask patient to remove radiopaque objects from abdomen.
- Position patient supine on table, legs extended.
- Place arms at sides or across chest.
- Align midline of patient with table.
Position & centering point
At the level of the iliac crest (L4), at midline.
Central ray
Perpendicular to IR at the level of the iliac crest (L4), midline.
Exposure / technique
- kVp
- 70–80
- mAs
- 25–40
- SID
- 40" (102 cm)
- Notes
- Grid required. Supine position more comfortable for acute abdominal pain patients.
Image-quality criteria
- Entire abdomen visible from diaphragm to pubic symphysis.
- Spine midline shown without rotation.
- Pelvis and femoral heads visible at bottom.
- Air-fluid levels subtle but present if obstruction.
- Bone trabeculae and soft tissue sharp.
- Collimation: 14 x 17 inches or larger crosswise.
Common errors / ARRT traps
- 1 Patient rotation obscures midline and distorts anatomy.
- 2 Arms crossed or overhead overlap abdomen.
- 3 CR too high excludes pelvis and inguinal regions.
- 4 CR too low excludes diaphragm and stomach.
Clinical indications
- Routine abdominal pain evaluation.
- Bowel obstruction assessment.
- Acute abdomen rule-out.
- Urinary calculus detection.
Aligned to the 2025 ARRT Content Specifications.