Acute Lobar Nephronia

Acute lobar nephronia, also known as acute focal bacterial pyelonephritis, is a focal inflammation and bacterial infection of the kidneys without liquefaction or abscess formation. It is an interim between acute pyelonephritis and kidney abscess. ALN is a radiological diagnosis as clinical symptoms overlap with acute pyelonephritis.

 ALN is more commonly reported in pediatric population and reports in adults are much more scarce likely due to under diagnosis. Imaging in adults is not routine for acute complicated UTI. ALN typically requires longer duration of antibiotics.

Acute lobar nephronia also known as acute focal bacterial nephritis is “an acute localized non –liquefactive infection of the kidney caused by bacterial infection” . It is considered a midpoint in the spectrum of upper urinary tract infection  between acute pyelonephritis and intrarenal abscess.

ALN is a condition commonly described in the pediatric age group with limited case studies reported in the literature for adult population.

Longer duration of antibiotics are generally required in patients with acute lobar nephronia in comparison to acute pyelonephritis. We describe 2 cases of ALN with a review of literature.

Laboratory findings were remarkable for white cell count of 11,100 cells/microliter  .Urine culture from ED visit one day prior showed Escherichia coli>100,000 colony forming units /ml , which was sensitive to all tested antibiotics except ampicillin, trimethoprim/sulfamethoxazole and gentamicin. Intravenous (IV) Contrast enhanced Computed Tomography scan of the abdomen and pelvis showed findings consistent with acute pyelonephritis on the left side with an area of of low-attenuation in the upper pole, measuring up to 3.5 cm, which may represent a developing abscess.

The term was used in analogy to acute lobar pneumonia. The first case of ALN was described by Rosen field et al. It is also called as acute focal pyelonephritis. There is disagreement in the literature regarding the nomenclature used to describe ALN.

Some clinicians and radiologists use the term “complicated pyelonephritis” which likely accounts for ALN being under diagnosed. Rathore et al in their case series and review of acute lobar nephronia suggest that ALN is a better term to distinguish it from general bacterial infections of the kidney.

ALN is regarded as an interim between acute pyelonephritis and renal abscess. It is defined as an acute focal bacterial nephritis and characterized by non-liquefactive bacterial infection of one or more lobules of the renal parenchyma. In the past, ALN has been experimentally induced by surgically creating vesicoureteral reflux in pigs.

 Although most of the cases are focal, cases of migratory nephronia have also been described. Histologically, ALN is characterized by localized hyperemia, interstitial edema and heavy leukocytic infiltration with focal areas of necrosis.

ALN is clinically difficult to distinguish from APN and imaging plays a pivotal role in diagnosis. Unlike children where imaging is part of routine work up, in an adult with UTI, imaging is recommended only in certain situations therefore a high index of suspicion is required for the diagnosis of acute lobar nephronia.

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With Regards,

David Paul

Editorial Assistant

Journal of Clinical Nephrology and Research