From the Guidelines
Yes, a CT scan of the abdomen with or without contrast can be used to rule out a collection, particularly when ultrasound (US) is inconclusive or unable to evaluate deep collections [ 1 ].
Key Points
- CT scans provide the advantage of detecting deep collections and can help distinguish collections from adjacent vasculature or bowel using intravenous (IV) and oral contrast [ 1 ].
- US is more limited in evaluating collections deep within the soft tissues or adjacent to the loops of bowel, but is useful for screening superficial or large fluid collections and collections within or adjacent to solid organs [ 1 ].
- Noncontrast CT may be helpful in patients with suspected hemorrhage or in the evaluation for nephrolithiasis in the transplant kidney [ 1 ].
- The use of CT abdomen and pelvis with IV contrast should be considered in conjunction with the risks of nephrotoxicity from iodinated contrast [ 1 ].
Clinical Considerations
- In patients with fever of unknown origin, CT is usually the first-line modality [ 1 ].
- CT can be useful in patients with renal colic and moderate to severe hydronephrosis by US, as these patients can be at higher risk of stone passage failure [ 1 ].
- The presence of hydronephrosis on US can reduce the risk of alternate diagnosis being identified on CT [ 1 ].
From the Research
CT Scan for Abdominal Collection
- A CT scan of the abdomen with or without contrast can be used to rule out a collection, depending on the specific situation and patient factors 2, 3, 4, 5, 6.
Non-Contrast CT
- Non-contrast CT can provide benefit for critical decision-making in patients with acute surgical abdomen, with findings indicating the need for surgical treatment visualized on non-contrast images in 90.7% of patients overall 2.
- Non-contrast CT can be used to evaluate patients with acute nontraumatic abdominal pain, with no significant difference in diagnostic performance compared to CT with oral contrast in most cases 5.
Contrast-Enhanced CT
- Contrast-enhanced CT can be useful in certain situations, such as characterizing disease entities and facilitating the recognition of vascular structures 4.
- Intravenous contrast is the most frequently cited contrast agent, with at least 90% of respondents reporting its use in 12 of 18 indications 6.
Virtual Contrast Enhancement
- Virtual contrast enhancement using a generative adversarial network (GAN) based framework can synthesize contrast-enhanced CTs directly from non-contrast CTs, potentially reducing the need for contrast agents 3.