Chapter 110. Advanced Abdominal Imaging

1. What are the advantages and limitations of abdominal ultrasound?

2. What are the indications for gastrointestinal (GI) fluoroscopy?

3. What are the advantages of computed tomography (CT) when compared with magnetic resonance imaging (MRI) for imaging abdominal structures?

4. What are the indications for nuclear medicine imaging studies?

Radiologists expect to provide guidance in the use of advanced medical imaging tests in the care of acutely ill patients requiring hospitalization. This chapter is intended to present the thought processes that radiologists commonly use rather than dictate a particular test for a particular patient or situation.

Before ordering advanced imaging, it is always important to consider whether the information may be provided by prior studies. The KUB (Kidneys Ureter and Bladder) is often ordered as a screening examination but also serves as the initial default imaging examination when selection of a more specific test cannot be made, as when a patient has diffuse abdominal pain without any localizing signs. No preparation is required. The radiation exposure is slightly higher than a chest radiograph. Although originally IV and PO contrast material was administered in conjunction with plain film radiography, this is no longer common practice. However, in the acutely ill patient who has received one or more contrast agents for a prior study, the KUB can provide additional information without readministration of contrast material, especially for patients with abdominal pain occurring during or shortly after imaging of a different region of the body. A rudimentary intravenous pyelogram (IVP) can be obtained following contrast-enhanced head or chest CT or even cardiac catheterization. The period of time over which the visualization persists will be inversely proportional to the patient's estimated glomerular filtration rate (eGFR) over several hours. The oral contrast material administered for an abdominal CT scan will be concentrated within the colon and often remain visible for several days.

Ultrasound can be the best possible examination for the acutely ill hospitalized patient. It is relatively inexpensive, uses no ionizing radiation, and tailored examinations can be performed at the patient's bedside if necessary. Ultrasound is enhanced by passage through water and stopped by air and bone. It is therefore able to detect a pleural effusion and guide thoracentesis of small to moderate pleural effusions. The information provided depends very much on the operator even with complete video recording. Ultrasound is a very useful tool for the interventional radiologist and may be chosen by the radiologist for a variety of biopsies including liver and prostate.

Abdominal US

In the abdomen, renal and gallbladder ultrasounds are standard examinations. A screening abdominal ultrasound will also include images of the liver, spleen, and pancreas. The confirmation of a simple cyst can exclude more significant pathology in many organs, including ovaries, kidneys, and liver. In order to visualize the pancreas, the ultrasonographer will either compress the air out of the stomach or have the patient drink water to allow the stomach to ...