Acute Focal Bacterial Nephritis in a Patient with Solitary Kidney: Case Report

INTRODUCTION

Acute focal bacterial nephritis is an underdiagnosed condition. It clinically resembles acute pyelonephritis. If unrecognized and undertreated, it may progress into complications (kidney abscess and scars). Contrast-enhanced computed tomography (CT) reveals specific images of the disease and is considered the gold standard to make the diagnosis.

CASE REPORT

A 63-year-old male patient with solitary kidney presented with symptoms compatible with acute pyelonephritis. Kidney ultrasound was not conclusive. Because of persisting high-grade fever not resolving after 48 hours of antibiotics, a contrast-enhanced CT was then performed, and the diagnosis of acute focal bacterial nephritis was made. A repeat CT after three weeks of intravenous (IV) antibiotics showed marked improvement of the intrarenal lesions, and a fourth week of IV antibiotics was dispensed.

CONCLUSION

Diagnosing acute focal bacterial nephritis is important (particularly in a patient with solitary kidney). This will dictate the therapy duration. Unlike acute pyelonephritis, acute focal bacterial nephritis requires at least three weeks duration of antibiotics to avoid progress into further complications.

Acute Focal Bacterial Nephritis Caused by Staphylococcus simulans

A toddler girl presented to our hospital with a fever that lasted for five days. She had no prior history of urinary tract infections or contact with farm animals. Investigations revealed a diagnosis of acute focal bacterial nephritis (AFBN), and we initiated antimicrobial therapy with ampicillin and cefmetazole. On day five, methicillin-resistant coagulase-negative staphylococci were detected in her urine culture, and we changed the antibiotics to vancomycin. Antibiotic therapy was continued for 21 days, with no recurrence of fever. Finally, the bacteria were identified as Staphylococcus (S.) simulans, which is a common farm animal pathogen. Clinicians should be aware of the possibility of AFBN caused by S. simulans, even if the patient has no prior history of close contact with farm animals. If a rare organism is detected in urine culture during AFBN treatment, the patient should be treated with appropriate antibiotics for the pathogen.

Acute focal bacterial nephritis and prolonged fever

Acute focal bacterial nephritis (AFBN) is characterised by a complicated upper urinary tract infection ranging from acute pyelonephritis to renal abscess. Timely diagnosis of AFBN is important because antibiotic therapy of longer duration is required. A 10-year-old boy presented with fever for 5 days and bilateral flank pain. He was oriented and cooperative but appeared ill. Physical examination did not reveal any oedema or costovertebral angle tenderness. Acute phase reactants such as erythrocyte sedimentation rate and C-reactive protein were raised, serum creatinine was 1.25 mg/dL (0.31-0.88) and leucocyte esterase was positive in the urine. Ultrasonographic examination demonstrated bilaterally enlarged kidneys with increased echogenicity. Because of the high creatinine level, abdominal magnetic resonance imaging (MRI) was performed instead of computed tomography (CT) for further evaluation. The MRI showed an increase in the size of both kidneys, renal cortical heterogeneity and multiple cortical nodular lesions with diffusion restriction (constrained Brownian movement of water molecules) on diffusion-weighted MRI. A negative urine culture result in children presenting with fever and abdominal pain may mislead the clinicians, causing them to miss a nephro-urological diagnosis. It is therefore recommended that patients in whom the cause of fever cannot be determined be scanned by ultrasound and examined by CT or MRI so that undiagnosed and/or suspected cases of AFBN might be detected.

Acute Lobar Nephronia in an infant presented as a renal tumor

A case report of a 02-month-old infant referred to us with incidental bilateral renal masses on ultrasound, which was reported as nephroblastoma/Wilms tumor on CT scan, no signs, and symptoms of infection. Urine and blood cultures were negative, which led to a percutaneous renal biopsy which showed Acute Lobar Nephronia. The infant was started intravenous antibiotics which resulted in the resolution of bilateral renal masses on serial ultrasounds.

Acute Focal Bacterial Nephritis: Two Cases and Review of the Literature

Rationale:

Acute focal bacterial nephritis (AFBN) has mainly been reported in pediatrics. It may be an underdiagnosed condition in adults because it resembles acute pyelonephritis (APN) in its clinical presentation.

Presenting concerns of the patients:

Two young women (25 and 27 years old, respectively) presented with complaints compatible with a diagnosis of APN. However in both, fever was of high grade, persistent for several days in spite of antibiotic administration, and there was demonstrated worsening of the inflammatory biomarkers. A contrast-enhanced computed tomography (CECT) led to the diagnosis in both cases.

Diagnoses:

Contrast-enhanced computed tomography reveals the most sensitive and specific images of AFBN. This includes wedge-shaped lesions with decreased enhancement, which may be focal or multifocal.

Interventions (including prevention and lifestyle):

Antibiotic therapy for at least 3 weeks.

Outcomes:

Resolution of AFBN was obtained after 3 weeks of antibiotics.

Lessons learned:

Our 2 cases illustrate the importance of CECT imaging to confirm the diagnosis of AFBN. Interstitial bacterial inflammation may have a worse prognosis if not diagnosed early and efficiently treated. Unlike APN, the management of AFBN requires at least 3 weeks of antibiotics to prevent the development of renal scarring and renal abscess.

Comparison of acute lobar nephronia and acute pyelonephritis in children: a single-center clinical analysis in southern taiwan

BACKGROUND

Patients with acute lobar nephronia (ALN) require a longer duration of antimicrobial treatment than those with acute pyelonephritis (APN), and ALN is associated with renal scarring. The aim of this study was to provide an understanding of ALN by comparing the clinical features of pediatric patients with ALN and APN.

METHODS

We enrolled all of the patients with ALN (confirmed by computed tomography) admitted to our hospital from 1999 to 2012 in the ALN group. In addition, each patient diagnosed with APN who was matched for sex, age, and admission date to each ALN patient was enrolled in the APN group. The medical charts of patients in these two groups were retrospectively reviewed and analyzed for comparison.

RESULTS

The fever duration after hospitalization in the ALN group and the APN group were 4.85 ± 2.33 days and 2.30 ± 1.47 days respectively. The microbiological distributions and the majority of susceptibilities were similar in the ALN and APN groups. The majority of clinical manifestations are nonspecific and unreliable for the differentiation of ALN and APN. The patients with ALN were febrile for longer after antimicrobial treatment, had more nausea/vomiting symptoms, higher neutrophil count, bandemia, and C-reactive protein (CRP) levels, and lower platelet count (all p < 0.05). In multivariate analysis, initial CRP levels, nausea/vomiting symptoms, and fever duration after admission were independent variables with statistical significance to predict ALN. Severe nephromegaly occurred significantly more in the ALN group than in the APN group (p = 0.022).

CONCLUSION

The majority of clinical manifestations, laboratory findings, and microbiological features are similar between patients with ALN and APN. Clinicians should keep a high index of suspicion regarding ALN, particularly for those with ultrasonographic nephromegaly, initial higher CRP, nausea/vomiting, and fever for > 5 days after antimicrobial treatment.