Abdomen (dorsal decubitus view)

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The dorsal decubitus view is a supplementary projection often replacing the lateral decubitus view in the context of an unstable patient who is unable to roll nor stand. Used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to be transferred to, or other imaging modalities (e.g. CT) are not available.

This projection is not a lateral projection.

Indications

Used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to safety lay in the lateral decubitus position or to be transferred to, or other imaging modalities (e.g. CT) are not available.

Patient position

  • the patient is supine
  • the detector is placed landscape of at the patient's left-hand side running parallel to the long axis of the abdomen 
  • patient's hands should be raised to avoid superimposing on the region of interest; legs may be flexed for balance
  • patients should be changed into a hospital gown, with radiopaque items (e.g. belts, zippers) removed
  • x-ray is taken in full inspiration

Technical factors

  • horizontal beam dorsal decubitus view
  • centering point
    • 5 cm above the iliac crests at the midcoronal plane of the patient 
  • collimation
    • anteriorly to include soft tissue boundaries 
    • posterior to include soft tissue 
    • inferior to the level of the pubic rami 
    • superior to the diaphragmatic domes 
  • orientation
    • landscape
  • detector size
    • 35 cm x 43 cm
  • exposure
    • 70 - 80 kVp
    • 30 - 120 mAs
  • SID
    • 100 cm
  • grid
    • yes

Image technical evaluation

  • it is essential that the anterior abdominal wall and the diaphgrams are included on the image to detect any free intraperitoneal gas.
  • there should be no blurring of the bowel gas due to respiratory motion.

Practical points

Due to the high exposure of this examination and the need to demonstrate soft tissue, the use of an aluminum filter over the anterior portion of the patient is advantageous to even out density and filter out higher energy x-rays.