KUB X-ray positioning (urinary tract survey)
One of the routine abdomen views. The patient lies on their back, the beam passes front to back (AP), straight on to the receptor, and the centring point is the midline at the iliac crests.
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
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- Ankle positioning
- Foot positioning
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Supine. Lay the patient supine, bladder emptied first, head on a small pillow.
Centring & collimation
Central ray
APCentre: the midline at the iliac crests.
Beam: AP, perpendicular to the receptor.
Collimate: upper poles of the kidneys to the symphysis
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 35 × 43 cm | portrait |
| Placement | Table bucky | Grid in |
| Angulation | None | Perpendicular to the receptor |
Marker & breathing
- Marker: R marker
- 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 | 70 | 20 | 5 |
| S | 70 | 32 | 8 |
| M | 70 | 40 | 10 |
| L | 70 | 63 | 16 |
These start from a classic film-screen chart (70 kV, 63 mAs at 140 cm) and are adjusted for a digital detector at 100 cm. The DR column is what ScanFlo's console suggests; each step up or down changes the mAs by about a quarter. 80 kV with contrast: 32 mAs.
Image quality checklist
- The lower ribs (upper renal poles) are included.
- The symphysis is included (add a bladder view if not).
- 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 |
|---|---|---|
| Upper renal poles cut off | Centring low | Recentre; take a second film if the abdomen is long. |
Common questions
- Where do you centre for a urinary tract survey (KUB) X-ray?
- The centring point is the midline at the iliac crests.
- What distance and beam angle does a urinary tract survey (KUB) need?
- 100 cm from the tube to the receptor. The beam passes front to back (AP), straight on to the receptor.
- What size receptor, and do you need a grid?
- Use a 35 × 43 cm receptor, portrait, in the table 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 a urinary tract survey (KUB)?
- Upper renal poles cut off. Usual cause: centring low. The fix: recentre; take a second film if the abdomen is long.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a urinary tract survey (kub) in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.