Nephronia

Nephronia

Since the first description of ALN as reported by Rosenfield et al9 in 1979, the condition has subsequently also been described in a number of other studies.3,11 ALN is a nonsuppurative focal form of acute bacterial infection, generally affecting 1 or more renal lobules,3,4,9,10 and is considered to be a midpoint in the spectrum of upper UTI, a spectrum ranging from uncomplicated pyelonephritis to intrarenal abscesses.7Considering this dynamic nature of UTI, ALN may progress to renal abscess if left untreated. Hence, it is extremely important to differentiate ALN from intrarenal abscess, not only because these 2 conditions are pathologically different but also because they may be best managed differently. Surgical drainage may be required for most cases of intrarenal abscesses, whereas ALN, like APN, necessitates only antibiotic management.

The clinical severity of acute renal bacterial infection spans continuously from an uncomplicated lower urinary tract infection (UTI) to frank abscess formation.1 Among this suite of renal inflammatory diseases, acute lobar nephronia (ALN), also known as acute focal bacterial nephritis, has been diagnosed with ever-increasing frequency in patients, as a result of the advancement of noninvasive imaging-technique modalities.2 ALN presents as a localized nonliquefactive inflammatory renal bacterial infection, which typically involves 1 or more lobes.3,4 It has previously been indicated as a complicated form of acute renal infection, representing the progression of the inflammatory process of acute pyelonephritis (APN).5 ALN may also represent a relatively early stage of the development of renal abscess.6 The typical clinical presentations of ALN include fever, flank pain, leukocytosis, pyuria, and bacteriuria, which are similar to those with renal abscess or APN.1,3

Diagnosis

Most of patients with ALN presented with nonspecific findings of fever and flank or abdominal pain. Pyuria, leukocytosis, and elevated C-reactive protein also usually were found. Some patients presented only with fever and had minimal symptoms such as vague flank discomfort, malaise, or even no urinary symptoms and, rarely, a few patients may have no pyuria and negative urine cultures.

Investigation

Sonographically, ALN generally presents as severe nephromegaly or a poorly defined, irregularly margined focal mass with hyper-, iso-, or hypoechogenicity, depending on the temporal sequence of the lesions and the resolution of the disease.7,8 Although renal ultrasonography has been considered the best and most effective screening method, various false-positive and false-negative findings have been reported previously.1,9 The characteristicappearance of a focal mass in the kidney with poorly defined margins is the hallmark of the ultrasonographic findings for ALN.2,7,8,10 Unfortunately, however, the sensitivity of this ultrasonographic characteristic for ALN diagnosis is probably not satisfactory

Computed tomography (CT), instead, is currently recognized as the most sensitive and specific imaging modality for diagnosing ALN.1,2,4,7,10 CT images of the ALN-infected areas typically appear as wedge-shaped, poorly defined regions of decreased nephrogenic density after contrast medium administration1,4,7 and as mass-like hypodense lesions in the more severe form.11 CT, however, is costly and requires the sedation of a young patient. We recently developed a systematic imaging work-up scheme using ultrasonography screening followed by CT. With this scheme, not only the efficacy of CT performance but also the sensitivity of overall diagnosing of ALN seems to be improving.12

Treatment

Treatment for patients with ALN generally requires intravenous and oral antibiotic medication as does treatment for uncomplicated APN.3,7,10 (Most common 70-80% E.coli) Surgical intervention is rarely needed for patients with ALN, except for those with concomitant urologic abnormalities, which may increase the risks for occurrence of acute bacterial infection.2 Although it has been suggested that the treatment duration for ALN needs to be at least the same as that for uncomplicated APN, recommendations for the duration of antibiotic treatment still remains somewhat inconclusive, and to the best of our knowledge, for neither condition has a rigorous therapeutic efficacy comparison of relevant medication been performed.7

Reference

http://pediatrics.aappublications.org/cgi/content/full/117/1/e84