Comparison of diffusion-weighted whole-body magnetic resonance imaging and abdominal ultrasonography versus contrast-enhanced computed tomography in diagnosing acute focal bacterial nephritis: a retrospective cohort study.

Background: Abdominal contrast-enhanced computed tomography (CT) is the gold standard for diagnosing acute focal bacterial nephritis (AFBN). However, contrast-enhanced CT is contraindicated for patients with contrast medium allergies, impaired renal function, pregnancy, metformin use, and thyroid disease. Diffusion-weighted whole body imaging with background body signal suppression (DWIBS) is a safe imaging modality for such patients. Although DWIBS can quickly evaluate inflammation, its role in diagnosing AFBN remains unclear. Therefore, we aimed to compare imaging modalities for diagnosing AFBN and evaluate the efficacy of DWIBS in patients receiving inpatient treatment. Methods: In this retrospective cohort study, we included individuals aged ≥18 years hospitalized for AFBN under the Diagnosis Procedure Combination system from January 1, 2013, to December 31, 2022. Exclusion criteria included imaging findings not suggestive of AFBN. The primary outcome was the proportion of patients who underwent abdominal ultrasonography, contrast-enhanced CT, and DWIBS and their respective diagnostic rates for AFBN. The secondary outcome was the accuracy of AFBN detection using abdominal ultrasonography and DWIBS compared to that of the standard contrast-enhanced CT. Results: The study cohort included 123 patients, with an average age of 51±20.4 years; 107 (87.0%) were women. Abdominal ultrasonography was used in 74.0% (91/123) of the patients, yielding a diagnostic rate of 31.9% (29/91). Contrast-enhanced CT was used in 90.2% (111/123) of the patients, with a diagnostic rate of 100% (111/111). DWIBS was used in 11.4% (14/123) of the patients, with a diagnostic rate of 85.7% (12/14). The accuracy of AFBN detection (correct response rate) was 26.6% (21/79) for abdominal ultrasonography and 75.0% (6/8) for DWIBS, indicating that DWIBS had a significantly higher accuracy rate than that of abdominal ultrasonography [Chi-square test, χ Conclusions: DWIBS demonstrated promising diagnostic accuracy for AFBN compared with abdominal ultrasonography, suggesting it could be a valuable diagnostic tool for this condition. Given its diagnostic accuracy, DWIBS may be considered over abdominal ultrasonography in patients who are unable to undergo contrast-enhanced CT due to allergies or pregnancy. However, further prospective studies with larger sample sizes are necessary to validate these findings.