Abstract

Objective: We evaluated the value of magnetic resonance imaging (MRI) in the diagnosis of urinary system calculi.

Materials and methods: Fifty-five patients with urinary system calculi disease were included in the study. A total of 80 calculi were evaluated. Findings of 3D MR urography (MRU) and diuretic combined contrast-enhanced dynamic 3D T1 MR renography (MRR) were compared with those of ultrasonography (US) and intravenous urography (IVU). MRI evaluation was performed by two radiologists, of whom one was aware of the patients’ clinical and previous radiological findings and the other was blind to these findings.

Results: Both radiologists detected the same 35 calculi and missed 19 calculi. The first radiologist detected 26 calculi different from those detected by the second radiologist (p<0.001). Findings of the first radiologist were used for comparison with previous findings. For all calculi including renal, ureteropelvic junction, and ureter locations, with reference to IVU, both MRU and MRR had a sensitivity of 94%, positive predictive value (PPV) of 94%, but had a specificity of less than 50%. When US was taken as the reference modality, the sensitivity was 100% and PPV was 97% for both MRU and MRR, with specificity rates being 83% and 86%, respectively. Compared to US and IVU, the size of the calculi were significantly underestimated by MRI (p<0.001). 

Conclusion: The size of the calculi is significantly underestimated by MRI; however, MRI evaluation in the light of clinical and previous radiological findings provides significant diagnostic support.