Abdomen (lateral decubitus view)

Thelateral decubitus abdominal radiograph is often included in an acute abdominal series. The more useful position for detecting free intraperitoneal air is the left lateral decubitus position.

Patient position

• the patient is in recumbent position, with heranterior (PA position) or his side againstposterior (AP position) part of the detectorpatient to be in contact with the image receptor
  • usually left side down (left lateral decubitus)
• patient's hands should be raised to avoid superimposing on the region of interest, legs may be flexed for balance
• rotation of shoulders or pelvis should be minimized, but not as critical as on other abdominal radiographic views
• legs may be flexed for balance
• field of view should contain the diaphragm and the right skin border (to visualize all of the lateral liver border)to entire abdomen
• patient should ideally be recumbent for 5-10 minutes before obtaining the radiograph
• Image taken when patient is at full inspiration

X-ray beam features

• the view can be obtained in either the AP or PA direction direction, with the beam justcentral ray should be centered approximately 5cm above the level of iliac crest
• source-to-image distance: 40" (100 cm)
• 70-75 kVp at 40-100 mAs (or AEC)
• grid may be used

Advantages

• may be more useful than the PA erect view for detecting intraperitoneal free gas ²
• best view to see gas from a gastroduodenal perforation or a distended duodenal loop in acute pancreatitis or cholecystitis
• patient does not have to be able to stand upright

Disadvantages

• portable views are markedly inferior to radiographs under controlled setting, although they may be useful for evaluating the positions of tube and lines