Lateral decubitus abdomen X-ray positioning (left side down)
An extra abdomen view, used when a routine one is not enough. The patient lies on their left side, the beam passes front to back (AP), straight on to the receptor with the tube horizontal, and the centring point is the midline, upper abdomen.
By the ScanFlo Editorial Team · Updated
In this section · X-ray positioning
- X-ray positioning guides
- Skull positioning
- Face & sinuses positioning
- Soft tissue neck positioning
- C-spine positioning
- Chest positioning
- Shoulder positioning
- Humerus positioning
- Elbow positioning
- Forearm positioning
- Wrist positioning
- Hand positioning
- T-spine positioning
- Abdomen positioning
- L-spine positioning
- Sacrum & SI joints positioning
- Pelvis positioning
- Hip positioning
- Femur positioning
- Knee positioning
- Tibia & fibula positioning
- Ankle positioning
- Foot positioning
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Left lateral decubitus. Lay the patient on the left side, back against the vertical detector, for several minutes before exposure; take the opposite side too.
Centring & collimation
Central ray
APCentre: the midline, upper abdomen.
Beam: AP, perpendicular to the receptor, horizontal beam.
Collimate: include the uppermost flank and the upper diaphragm
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 110 cm | Horizontal beam |
| Receptor | 35 × 43 cm | landscape |
| Placement | Erect (wall) bucky | Grid in |
| Angulation | None | Perpendicular to the receptor |
Marker & breathing
- Marker: marker on the up side, labelled decubitus
- Breathing: Breathe out and hold.
Exposure by patient size
Treat these as a starting point. Your detector, your generator and the patient in front of you will all move the numbers.
| Patient size | kV | mAs (chart) | mAs (DR default) |
|---|---|---|---|
| XS | 80 | 6.3 | 2.5 |
| S | 80 | 10 | 4 |
| M | 80 | 12.5 | 5 |
| L | 80 | 20 | 8 |
These start from a classic film-screen chart (80 kV, 20 mAs at 140 cm) and are adjusted for a digital detector at 110 cm. The DR column is what ScanFlo's console suggests; each step up or down changes the mAs by about a quarter.
Image quality checklist
- The uppermost flank is fully included (free gas collects there).
- The upper part of the diaphragm is shown.
- The anatomical side marker is visible, correct and clear of the anatomy.
- Collimation borders are visible on all sides, no wider than the area requested.
Faults & how to fix them
| Fault | Cause | Fix |
|---|---|---|
| Up-side flank cut off | Centred on the midline only | Shift centring toward the uppermost flank. |
Common questions
- Where do you centre for an abdomen lateral decubitus X-ray?
- The centring point is the midline, upper abdomen.
- What distance and beam angle does an abdomen lateral decubitus need?
- 110 cm from the tube to the receptor. The beam passes front to back (AP), straight on to the receptor with the tube horizontal.
- What size receptor, and do you need a grid?
- Use a 35 × 43 cm receptor, landscape, in the wall bucky. A grid is needed.
- What should the patient do with their breathing?
- Ask them to breathe out and hold it while you expose.
- What goes wrong most often on an abdomen lateral decubitus?
- Up-side flank cut off. Usual cause: centred on the midline only. The fix: shift centring toward the uppermost flank.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a abdomen lateral decubitus in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.