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Lobar nephronia or acute focal bacterial nephritis is an acute, non-suppurative, focal, renal infection.1 It usually presents with fevers and flank pain. In the general population it is well described in children. We report an adult co-infected with HIV and hepatitis C, who presented with meningism and bilateral lobar nephronia.
A 37 year old man was admitted with a 4 day history of headaches, fevers, and vomiting with a 2 week background of dysuria. On presentation with a seroconversion illness 3 years previously he received combination antiretroviral therapy (ARV) for 9 months. Four months before the current admission ARV was re-introduced for symptomatic HIV infection. The most recent CD4 count was 250 cells×106/l, and HIV viral load was 107 000 copies/ml. Hepatitis C infection had recently been diagnosed and the patient was receiving weekly interferon alfa. His symptoms began the day after the fifth injection. On examination he was pyrexial, temperature 39°C, had meningism and abdominal tenderness in both right upper quadrant and left iliac fossa. Investigations showed C reactive protein (CRP) 265 (normal = 0–4) IU/l, neutrophils 11×109/l, and normal urea and creatinine. Cranial computed tomography (CT) and cerebrospinal fluid analysis were normal. Urinanalysis showed protein++ and blood+; urine culture was negative. Blood cultures grew Escherichia coli, which was treated with cefuroxime. Abdominal CT scan showed multiple low attenuation solid lesions with peripheral enhancement in both kidneys (fig 1A). The patient’s symptoms rapidly settled. He completed a 4 week course of oral cephadroxyl. As E coli was cultured from blood and a repeat scan after completion of treatment was normal (fig 1B) the renal CT appearances were ascribed to lobar nephronia.
The CT appearance of lobar nephronia is of either a single, or more uncommonly, multiple lesions in either one or both kidneys. The appearances are of either inflammatory (hypodense wedge-shaped) areas, or mass-like lesions.2,3 A radiological differential diagnosis for single lesions includes intrarenal abscess, renal carcinoma, and simple cyst. For multiple lesions, it includes microabscesses, lymphoma, hamartomata, and metastases.
The clinical severity lies between that of pyelonephritis and renal abscess and it is important to differentiate lobar nephronia from these pathologies as management differs both in duration of antibiotics and the need for drainage of renal abscess. Histologically, the conditions differ. By contrast with the tissue necrosis and liquefaction seen in an abscess, in lobar nephronia there is localised hyperaemia, interstitial oedema, and leucocyte infiltration. These features are less severe and are diffuse in acute pyelonephritis.2E coli is the most common causative organism. Other pathogens include Proteus mirabilis, Staphylococcus aureus, Klebsiella spp, Pseudomonas aeruginosa, and enterococci. Antibiotics are given for up to 6 weeks and relapse may occur.
The majority of reports of lobar nephronia in the general population are in children, probably reflecting the higher incidence of urinary tract infections in children. Although lobar nephronia has been described previously in adult HIV infected patients,4 our patient had an unusual presentation with meningism. Response to antibiotics was good and it is unclear to what extent immunosuppression due to HIV or hepatitis C infection, or interferon alfa may have contributed to the development of lobar nephronia. This case describes an uncommon presentation of renal infection in HIV infected adults and highlights the need to exclude differential diagnoses, especially lymphoma and metastases.