What is the role of CT scanning in the diagnosis of abdominal abscess?

Updated: Mar 27, 2020
  • Author: Alan A Saber, MD, MS, FACS, FASMBS; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Computed tomography (CT) has greater than 95% accuracy and is the best diagnostic imaging method for abdominal abscess. The presence of ileus, dressings, drains, or stomas does not interfere with reliability.

For good anatomic resolution, use oral and intravenous (IV) contrast (see the images below). Oral contrast may help to differentiate a fluid-filled extraluminal structure from a normal intestine. Extravasation of oral contrast indicates a fistula or an anastomotic leak. IV contrast may enhance the abscess by concentrating the contrast material within the abscess wall. The use of oral and IV contrast may be limited by ileus, allergy to contrast material, and renal insufficiency.

Contrast-enhanced computed tomography (CT) scan of Contrast-enhanced computed tomography (CT) scan of infected pancreatic pseudocyst (which can develop from acute necrotizing pancreatitis and give rise to an abscess).
A 35-year-old man with a history of Crohn disease A 35-year-old man with a history of Crohn disease presented with pain and swelling in the right abdomen. Figure A shows a thickened loop of terminal ileum adherent to the right anterior abdominal wall. In figure B, the right anterior abdominal wall, adjacent to the inflamed terminal ileum, is markedly thickened and edematous. Figure C shows a right lower quadrant abdominal wall abscess and enteric fistula (confirmed by the presence of enteral contrast in the abdominal wall).

Identify any occult abscesses using serial images obtained from the diaphragm to the pelvis. The appearance of an air bubble within a fluid collection or a low-attenuation extraluminal mass is diagnostic of an intra-abdominal collection. CT can document inflammatory edema in the adjacent fat (obliteration of fat plane) and hyperemia in the abscess wall (enhancement).

Drawbacks of CT include nonportability, relative difficulty in diagnosing intraloop abscesses, and, possibly, poor patient cooperation.

Recent intra-abdominal surgery also may pose a diagnostic problem in patients in whom intra-abdominal abscesses are suspected. CT is not recommended for use in diagnosing such abscesses until approximately postoperative day 7, by which time postoperative tissue edema is reduced and nonsuppurative fluids (eg, hematoma, seroma, intraoperative irrigation fluid) should be reabsorbed. In most postoperative patients, signs of intra-abdominal abscesses do not develop within the first 4-5 days.

A literature review from the Netherlands indicated that CT is superior to graded-compression ultrasonography in the diagnosis of acute appendicitis, a potential cause of abdominal abscess. [9]

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