What is the role of MRI in the diagnosis of nephrolithiasis?

Updated: Jun 21, 2018
  • Author: Chirag N Dave, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Answer

Magnetic resonance imaging (MRI) has virtually no role in the current evaluation of acute renal colic in the typical patient. Direct detection of most stones is not possible with MRI, and MRI should not be used for that purpose in most instances. MRIs are generally more expensive than other studies, such as CT scans, which reveal stones much better.

On the other hand, MRI produces no dangerous radiation, the gadolinium contrast it uses has minimal nephrotoxicity, and it can readily reveal urinary obstruction even if the stones themselves are not easily visualized. These attributes make using MRI reasonable in selected cases in which other technologies are too toxic or potentially dangerous, such as in some children and in pregnant women (see below). Gadolinium contrast, however, is contraindicated if the estimated glomerular filtration rate is less than 30, owing to the risk of nephrogenic systemic fibrosis.

Use of MRI in pregnant patients is somewhat controversial. Long-term effects on the fetus are unknown, and MRI is not specifically indicated in pregnancy, although it is not specifically contraindicated either. Anecdotal reports suggest that MRI has no immediately detectable deleterious effects. When other imaging modalities cannot be used or are insufficient, magnetic resonance urographic imaging can be considered on a case-by-case basis when the benefits to the mother and fetus outweigh the potential risks.

Although MRI does not play a major role in the diagnosis of ureteral stones, it can be used for this purpose. One study of 40 consecutive patients with acute flank pain found sensitivity of 54-58% and specificity of 100% using breath-hold heavily T2-weighted sequences. [40] Sensitivity and specificity increased to 96.2-100% and 100%, respectively, using gadolinium-enhanced 3-D FLASH MR urography. Its lack of radiation makes MRI a good choice in this setting for pregnant women who have nondiagnostic findings from a sonogram.


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