Utility of MRI in diagnosis and treatment of acute focal bacterial nephritis with abscess formation in a paediatric patient

Contrast-enhanced CT is the gold standard for the diagnosis of acute focal bacterial nephritis (AFBN). However, owing to radiation exposure and the possibility of contrast agent-induced side effects, contrast-enhanced CT is not always recommended for children. A paediatric patient presenting with a 1-week history of fever was admitted to our hospital. After a urine culture detected Escherichia coli, antimicrobials were administered; however, the fever had not resolved by the third day of hospitalisation. Renal diffusion-weighted MRI was performed and showed multiple wedge-shaped areas of high signal intensity in the right kidney. Additionally, the same site showed an area of low signal intensity in the apparent diffusion coefficient, and a diagnosis of AFBN with abscess was made. A chronic-phase technetium-99m-labelled dimercaptosuccinic acid renal scintigraphy was performed, but there was no renal scarring. MRI may be a more suitable tool for diagnosing AFBN given no radiation exposure.

Are we losing awareness of other infections due to the fear of coronavirus disease-2019 and MIS-C?

INTRODUCTION

Multisystem inflammatory syndrome in children (MIS-C) is a rarely seen severe complication of coronavirus disease-2019 (COVID-19). Although fever is one of the indispensable symptoms, other infections should be considered in the differential diagnosis during the pandemic.

CASE REPORT

An 8-year-old and a 16-year-old female patient were admitted with fever, vomiting, headache. Both had fulfilled the criteria and were diagnosed with MIS-C. However, they both had remarkable persistent costovertebral angle tenderness, which was unexpected in MIS-C. In Case-1, urine analysis showed microscopic hematuria without pyuria, and urine culture showed no bacterial growth. Case-2 had microscopic hematuria and pyuria with Escherichia coli growth in urine culture. Contrast-enhanced computed tomography showed wedge-shaped hypodense multiple lesions in bilateral kidneys for Case-1, in the right kidney for Case-2. They diagnosed acute focal bacterial nephritis (AFBN).

CONCLUSIONS

The diagnostic criteria of MIS-C can overlap with the symptoms of other severe septic infections such as AFBN, which is a rare urinary tract infection, diagnosed by imaging of localized renal inflammatory mass-like or wedge-shaped lesion. A detailed anamnesis and careful physical examination may help differential diagnosis.

Non-invasive discrimination of acute focal bacterial nephritis with pyelonephritis

BACKGROUND

The appropriate antimicrobial treatment period for febrile urinary tract infection (UTI) can be changed, depending on whether the patient has acute focal bacterial nephritis (AFBN). The aim of this study was to clarify the characteristics of AFBN compared with those of acute pyelonephritis (APN) and establish a strategy to detect AFBN.

METHODS

A total of 77 patients diagnosed with febrile UTI were enrolled. They were divided into APN (n = 64) and AFBN groups (n = 13). The clinical data and other laboratory biomarkers were retrospectively analyzed.

RESULTS

The time required for fever resolution after antimicrobial treatment was significantly longer in the AFBN group than in the APN group (2.77 days vs 1.11 days, respectively, P < 0.001). Also, the time to disappearance of pyuria after antimicrobial treatment was longer in the AFBN group than in the APN group (6.22 days vs 2.32 days, respectively, P = 0.001). Fever lasting >1.75 days after antimicrobial treatment had a sensitivity of 92% and specificity of 79% for the detection of AFBN, while pyuria disappearance after 4 days had a sensitivity of 88% and specificity of 85%. When patients fulfilled both cut-offs, the sensitivity and specificity were 89% and 97%.

CONCLUSION

Acute focal bacterial nephritis was associated with fever of significantly longer duration after antimicrobial treatment, and it took a longer time for pyuria to disappear. Children with febrile UTI should be evaluated for AFBN if the fever persists ≥48 h after the initiation of antimicrobial treatment and if pyuria lasts for 4 days.

Acute Focal Bacterial Nephritis Associated With Central Nervous System Manifestations: A Report of 2 Cases and Review of the Literature

Acute focal bacterial nephritis (AFBN) is a localized bacterial infection of the kidney presenting as an inflammatory mass without frank abscess formation. In children, most patients with AFBN present with nonspecific conditions, such as fever, vomiting, and abdominal pain. A small number of reported cases are accompanied by neurological symptoms, including meningeal irritation, unconsciousness, and seizures. We experienced 2 rare cases of AFBN associated with central nervous system lesions. The first case was a 3-year-old girl who had neurological symptoms, including unconsciousness and seizures, with AFBN associated with acute reversible encephalopathy. The second case was a 5-year-old girl who had neurological symptoms, including unconsciousness, with AFBN accompanied by clinically mild encephalitis/encephalopathy with a reversible splenial lesion.