Validity of diffusion-weighted magnetic resonance imaging in the evaluation of acute pyelonephritis in comparison with contrast-enhanced computed tomography

Abstract

Purpose: Applications of diffusion-weighted magnetic resonance imaging outside the brain have gained increasing importance in recent years, and recent studies have shown the usage of diffusion-weighted (DW) imaging in diagnosing pyelonephritis based on renal cortical and medullary apparent diffusion coefficient (ADC) values. The aim of this study was to assess the validity of DW magnetic resonance (MR) imaging in comparison with contrast-enhanced computed tomography (CECT) in diagnosing pyelonephritis. Material and methods: A cross-sectional observational study was conducted for a period of six months in a tertiary hospital in Coimbatore. All patients with clinical and laboratory diagnosis of acute pyelonephritis, who were referred for radiological imaging (CECT), were taken into the study. Out of 112 patients with a clinical and laboratorial diagnosis of acute pyelonephritis (APN), who underwent both DW MR and CECT, diagnosis of APN was made in 100 patients based on CECT, while in 12 cases the investigation (CECT) was negative. Finally, these 100 patients were included in the study. The validity of DW MR imaging in diagnosing APN was assessed by deriving sensitivity, specificity, and positive and negative predictive value in comparison with CECT findings. Results: The validity report of DW MR imaging in the detection of APN showed a very high sensitivity (96-100%) and specificity (86-90%) and very low false positives (6-10%) and negatives (< 5%), and it also showed that in the areas of affected renal parenchyma ADC values were consistently lower compared to unaffected renal parenchyma. Conclusion: Based on the generated hypothesis, DW MR imaging of the kidneys seems to be highly sensitive and specific for the detection of focal or diffuse infections within the kidney in comparison with CECT.

CT and MRI in Urinary Tract Infections: A Spectrum of Different Imaging Findings

“…High attenuation areas on non-contrast CT represent hemorrhage, while low attenuation areas represent edema. In early contrast-enhanced CT scan, there is a loss of corticomedullary differentiation associated with wedge-shaped hypo-enhancing areas or striated nephrogram pattern of linear alternating streaks of increased and decreased attenuation extending from the renal sinus to the renal cortex ( Figure 1 ) [ 11 ]. The pathophysiology of these radiological features may be due to poorly functioning renal parenchyma caused by vasospasm, tubular obstruction, or interstitial edema [ 10 , 24 ].…”

“…Both MRI and CT provide high image quality, allowing easy diagnosis of urinary tract infections. CT is usually readily available than MRI [ 11 ], however both modalities allow comprehensive evaluation of the renal parenchyma, surrounding structures and spaces, and better evaluation of the urothelial wall [ 12 , 13 ].…”

“…Other CT advantages include the use of multiplanar reconstruction (MPR), curved planar reformatted images, maximum intensity projection (MIP) and three-dimensional (3D) reconstruction. The detectability of air and calcifications is usually better using CT scan than MRI, although these conditions can also be detected on MRI [ 2 , 11 , 13 , 14 , 15 ].…”

“…Additionally, MRI can be used for diagnosing chronic UTI with or without using contrast material. MRI has also the advantage of high soft-tissue resolution and no radiation exposure [ 11 , 16 ].…”

“…Better tissue characterization can be obtained using dynamic contrast enhanced MRI and diffusion weighted MRI [ 16 , 17 ]. Diffusion-weighted imaging (DWI) can easily diagnose pyelonephritis based on renal parenchymal apparent diffusion coefficient (ADC) values, which are usually found to be lower than those of the unaffected renal parenchyma [ 11 , 18 , 19 ].…”