Diffusion-weighted magnetic resonance imaging: new perspectives in the diagnostic pathway of non-complicated acute pyelonephritis

The diagnosis of acute pyelonephritis (APN) requires demonstration of parenchymal involvement. When no predisposing conditions are found, non-complicated APN is suspected and CT or MRI should be performed. Diffusion-weighted (DW) MRI might be useful, quicker and cheaper than the standard gadolinium-enhanced (GE) MRI. The aim of this study is to compare DW-MRI with GE-MRI to test its diagnostic accuracy in APN. Of 318 consecutive patients hospitalised for APN, 279 underwent MRI. Four hundred and fourteen MR studies (first test and follow-up examinations) were gathered and data were processed using Diffusion Analysis software. DW-MRI has been compared with GE-MRI for evaluating diagnostic agreement. Two hundred and forty-four patients were diagnosed as having APN; 35 were negative. One hundred and sixty-three APN cases were considered non-complicated and selected for the study. Among the 414 MR examinations, comparing DW-MRI with GE-MRI, positive correlation was found in 258 cases, negative in 133. There were 14 false-negatives and 9 false-positives. DW-MRI achieved sensitivity 95.2 %, specificity 94.9 %, positive predictive value 96.9 %, negative predictive value 92.3 % and accuracy 94.6 %. DW-MRI is reliable for diagnosing non-complicated APN. The high diagnostic agreement between DW-MRI and GE-MRI offers new perspectives in diagnostic management, enabling diagnosis of non-complicated APN without using ionising radiation or contrast media. aEuro cent The diagnosis of acute pyelonephritis (APN) requires demonstration of renal involvement. aEuro cent Hitherto magnetic resonance imaging required gadolinium enhancement (GE-MRI) to establish this diagnosis. aEuro cent But diagnostic agreement between diffusion-weighted and GE-MRI offers new diagnostic opportunities. aEuro cent Quantification of ADC values can help diagnose and monitor APN. aEuro cent DW-MRI avoids ionising radiation and paramagnetic contrast medium administration.