An update on pyelonephritis: role of contrast enhancement ultrasound (CEUS)

Diffusion-weighted MRI in the identification of renal parenchymal involvement in children with a first episode of febrile urinary tract infection

Aims

This study aims to assess the diagnostic accuracy of diffusion-weighted Magnetic Resonance Imaging (DW-MRI) and determine the inter-reader agreement between two expert radiologists in detecting pyelonephritic foci during the initial episode of febrile urinary tract infection (fUTI) in children aged 0-5 years. Also, we aim to establish the correlation between clinical data and DW-MRI findings.

Methods

Children aged 0-5 years presenting with their first episode of fUTI were included in the study and underwent DW-MRI and Ultrasound (US) examinations within 72 h of admission. Inter-observer agreement between the two expert radiologists in assessing DW-MRI scans was evaluated using Cohen's kappa statistic. Clinical and laboratory data were subjected to statistical analysis.

Results

84 children (40 male, 44 female) with a mean age of 7.3 (SD 6.2) months were enrolled. DW-MRI detected pyelonephritis in 78 out of 84 cases (92.9%), with multiple foci observed in 73 out of 78 cases (93.6%). There was a "substantial" level of agreement between the two expert radiologists (κ = 0.725; observed agreement 95.2%). Renal US revealed pyelonephritis in 36 out of 78 cases (46.2%). White blood cell (WBC) count (p = 0.04) and lymphocyte count (p = 0.01) were significantly higher in patients with positive DW-MRI. Although not statistically significant, patients with positive DW-MRI had higher mean values of C-Reactive Protein, Procalcitonin, and neutrophil WBC count (7.72 mg/dl, 4.25 ng/dl, and 9,271 /μl, respectively).

Conclusions

DW-MRI exhibited excellent diagnostic performance in detecting pyelonephritic foci, with substantial inter-reader agreement among expert radiologists, indicating the reliability of the technique. However, a weak correlation was observed between laboratory parameters and DW-MRI results, potentially because of the low rate of negative DW-MRI findings.

Ultrasound, contrast-enhanced ultrasound and pyelonephritis: A narrative review

Acute pyelonephritis (APN) is a bacterial infection resulting in kidney inflammation, typically arising as a complication of an ascending urinary tract infection that ascends from the bladder to the kidneys. Clinical diagnosis is generally based on clinical and laboratory findings. Recent guidelines recommend not performing diagnostic imaging unless a complicated APN is suspected or the infection affects high-risk patients such as the elderly, immunocompromised individuals, or diabetics. Contrast-enhanced ultrasound (CEUS) is a valuable tool in both the diagnosis and follow-up of APN. It aids in distinguishing small simple nephritic involvement from abscess complications and monitoring their evolution over time during antibiotic therapy. Given its lack of ionizing radiation and nephrotoxicity, CEUS is a valid diagnostic modality for approaching and monitoring pyelonephritis, improving early identification and characterization of inflammatory lesions. This review aims to summarize the main evidence on the use of ultrasound and CEUS in the diagnosis of APN and its follow-up.

Scientific Status Quo of Small Renal Lesions: Diagnostic Assessment and Radiomics

Background: Small renal masses (SRMs) are defined as contrast-enhanced renal lesions less than or equal to 4 cm in maximal diameter, which can be compatible with stage T1a renal cell carcinomas (RCCs). Currently, 50-61% of all renal tumors are found incidentally. Methods: The characteristics of the lesion influence the choice of the type of management, which include several methods SRM of management, including nephrectomy, partial nephrectomy, ablation, observation, and also stereotactic body radiotherapy. Typical imaging methods available for differentiating benign from malignant renal lesions include ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI). Results: Although ultrasound is the first imaging technique used to detect small renal lesions, it has several limitations. CT is the main and most widely used imaging technique for SRM characterization. The main advantages of MRI compared to CT are the better contrast resolution and tissue characterization, the use of functional imaging sequences, the possibility of performing the examination in patients allergic to iodine-containing contrast medium, and the absence of exposure to ionizing radiation. For a correct evaluation during imaging follow-up, it is necessary to use a reliable method for the assessment of renal lesions, represented by the Bosniak classification system. This classification was initially developed based on contrast-enhanced CT imaging findings, and the 2019 revision proposed the inclusion of MRI features; however, the latest classification has not yet received widespread validation. Conclusions: The use of radiomics in the evaluation of renal masses is an emerging and increasingly central field with several applications such as characterizing renal masses, distinguishing RCC subtypes, monitoring response to targeted therapeutic agents, and prognosis in a metastatic context.

Contrast-Enhanced Ultrasound Follow-Up for Acute Pyelonephritis Patients

Contrast-enhanced ultrasound (CEUS) is increasingly used in clinical practice as the first diagnostic method in patients with suspected pyelonephritis rather than abdominal CT with contrast medium, especially in young subjects. We performed a retrospective analysis on patients in for whom a CEUS examination was utilized as a follow-up method after acute pyelonephritis as normal clinical practice. Through evaluating all patients, in terms duration between CEUS examination and normalization (healing) of the renal disease, we found that the mean duration is 25.9 days. Our ultrasound findings did not induce any therapeutic modifications, not even in the cases in which the examination was repeated several times. Therefore, setting up a CEUS follow-up examination after 25 days from the first diagnosis can reduce the number of repeated tests, benefitting patients and the healthcare system in terms of reducing costs.