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Abdominal radiography can be useful in many settings. Before the advent of computed tomography (CT) imaging, it was a primary means of investigating gastrointestinal pathology and often allowed indirect evaluation of other abdominal viscera.
Although abdominal radiography has lower sensitivity and specificity than a CT of the abdomen, it still serves a role as an adjunct or optional test. Current uses for abdominal radiography include:
- a preliminary evaluation of bowel gas in an emergent setting
- a negative study in a low pretest probability patient may obviate the need for a CT study and therefore lower radiation dose
- evaluation of radiopaque tubes and lines
- evaluation for radiopaque foreign bodies
- evaluation for postprocedural intraperitoneal/retroperitoneal free gas
- monitoring the amount of bowel gas in postoperative ileus
- monitoring the passage of contrast through the bowel
- colonic transit studies
- monitoring renal calculi
- pregnancy is a relative contraindication to the use of ionizing radiation
AP supine view
- can be performed as a standalone projection or as part of an acute abdominal series
PA erect view
- often taken with the supine view, when used together it is a valuable projection in assessing gas-fluid levels, and free gas in the abdominal cavity.
- used to visualize calculi within the urinary system (kidneys, ureters, bladder)
Generally, plain radiograph examination of the abdomen comprises an AP supine and PA erect view, supplemented by a number of additional views as clinically indicated.
lateral decubitus view
- performed as an alternative to the PA erect view to assess for free gas in the abdominal cavity
- often used as a problem-solving view during the identification and localization of foreign bodies
PA prone view
- performed if the patient is unable to lie supine
dorsal decubitus view
- used when it is unsafe to perform both a PA erect or a lateral decubitus view, this projection requires no patient movement.
- used in barium studies and the location of foreign bodies and/or lines such as a Tenckhoff catheter
The patient should be gowned with minimum clothing. Radiopaque materials (zippers, belts, etc.) should be removed.
If relevant, enteric tube suction should be avoided before the study. Ideally, the patient's bladder should be emptied as well.
Abdominal radiographs may be obtained in the radiology department or may be performed portably. Views should generally include either the diaphragm or inferior pubic ramus. Gonadal shielding may be provided for men.
Portable abdominal radiographs may be necessary due to patient immobility but are of much poorer quality.
The kVp of the x-ray beam may be altered in order to bring out different aspects of the abdominal radiograph:
- lower kVp offers greater tissue contrast and better visualization of gas, but there is decreased penetration of the x-ray beam
- higher kVp may be useful for evaluation of radiopaque objects (contrast, tubes, lines, etc.)