Exclusion of urolithiasis in the presence of contrast media using dual energy

Case history

45-year-old female with cholangiocellular carcinoma and known peritoneal carcinosis presents for follow-up scan post surgery and post chemotherapy.

Question

Can virtual non-enhanced imaging confirm the presence of a small renal stone in the lower pole of the right kidney found incidentally?

Diagnosis / Differential diagnosis

The two major differential diagnoses of hyperenhancing areas in the collecting system of the kidneys after the administration of contrast medium can be renal calculi and excreted contrast media. If a non-enhanced scan is not present, the differential diagnosis is difficult to assess.

Findings

Singular scan in portal venous phase. A small hyperenhancing nodule was found in the right lower pole collecting system. No nephrolithiasis was known prior to the scan. Virtual non-enhanced analysis demonstrated an iodine containing nodule that was no longer present in the virtual non-enhanced image. Thus a renal calculi could be excluded and the diagnosis of excreted contrast media could be made.

Comment

This case demonstrates that the use of dual energy scanning may make any non-enhanced scan phase obsolete. The scan technique gives one the flexibility to reconstruct a non-enhanced image when needed. Especially in incidental findings or to save dose, the virtual non-enhanced imaging technique allows for full imaging capacities without compromising image quality.

[1] Conventional 5 mm axial image of the lower pole of the kidneys. In the right kidney, the hyperenhancing area could be a calcified nodule.	[2] High resolution coronal reconstruction displays a nodular hyperenhancing nodule.
[3] High resolution sagittal reconstruction confirms the presence of a nodular hyperenhancing nodule, making the diagnosis of a renal calculus likely.	[4] Virtual non-enhanced analysis shows that the major component of the nodular formation is iodine, which is no longer present in the virtual non-enhanced image.

Authors: Axel Kuettner, Katharina Anders, Michael Lell