@article{article_1767841, title={Decoding acute pyelonephritis: imaging signatures and patterns of renal involvement across modalities}, journal={Anatolian Current Medical Journal}, volume={7}, pages={751–759}, year={2025}, DOI={10.38053/acmj.1767841}, author={Karaalioğlu, Banu and Sağlık, Pelin and Akçay, Ahmet}, keywords={Acute pyelonephritis, acute focal bacterial nephritis, magnetic resonance imaging, diffusion-weighted imaging, contrast-enhanced CT}, abstract={Aims: Acute pyelonephritis (APN) and acute focal bacterial nephritis (AFBN) are severe forms of urinary tract infection with overlapping clinical features. Differentiating these entities and assessing disease extent by imaging are critical for guiding management and preventing complications. Each modality has unique strengths and limitations. This study aimed to evaluate imaging-based differences between APN and AFBN and to assess the diagnostic performance of commonly used modalities. Methods: This retrospective study included 87 adult patients with renal parenchymal infection evaluated between 2018 and 2024. Imaging modalities comprised computed tomography (CT, n=87; 20 non-contrast, 67 contrast-enhanced), magnetic resonance imaging (MRI, n=20), and ultrasound (USG, n=53). Imaging features were compared between APN and AFBN. The diagnostic performance of non-contrast CT (NCCT), USG, and MRI was assessed using contrast-enhanced CT (CECT) as the reference standard. Agreement between CECT and contrast-enhanced MRI (CE-MRI) was analyzed using Cramer’s V. Results: APN was diagnosed in 40 patients (46%) and AFBN in 47 (54%). Complication rates, causative microorganisms, and associated findings did not differ significantly between groups. CECT was the most reliable modality, whereas USG (sensitivity 26.4%) often failed to detect the infection, and NCCT frequently failed to delineate the extent of disease. CE-MRI showed excellent agreement with CECT (Cramer’s V=0.93, p <0.001) but offered no additional diagnostic value. DWI was more sensitive in defining infection extent, revealing additional foci in AFBN or more localized disease in APN. All lesions visible on CE-T1WI were also detected on T2WI, and the combined use of DWI and T2WI improved diagnostic confidence, with T2WI contributing additional specificity. Conclusion: While APN and AFBN share similar clinical and microbiological characteristics, radiological patterns suggest differences in inflammatory pathogenesis. CECT remains the reference standard, but USG and NCCT have limited diagnostic value. MRI—particularly diffusion-weighted imaging (DWI) combined with T2-weighted image (T2WI) —demonstrated superior sensitivity and may serve as a promising contrast-free alternative, especially in children, pregnant patients, and those with impaired renal function.}, number={6}, publisher={MediHealth Academy Yayıncılık}, organization={This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.}