Effective ultrasonographic predictor for the diagnosis of acute lobar nephronia

Correct identification of acute lobar nephronia (ALN) is necessary to prevent progression to renal abscess. The goal of this retrospective study was to determine whether the sonographic finding of severe nephromegaly (i.e. renal length greater than mean + 3 sd) is a preselection criterion for computed tomographic (CT) scanning in diagnosing pediatric ALN among children with an acute upper urinary tract infection.

We evaluated a new imaging work-up scheme to detect pediatric ALN. All patients with urinary tract infection were evaluated with ultrasonography. If a markedly enlarged kidney or focal mass was present sonographically, CT scanning was done immediately. CT scanning was also performed when the patient had borderline nephromegaly and remained febrile for 72 h after start of antibiotic treatment. ALN diagnosis was made on the basis of positive CT findings.

Thirty patients with ALN (13 left, 7 right, 10 bilateral) and one with acute pyelonephritis were identified. ALN in all patients resolved after 3 weeks of antibiotic treatment. Thirty-nine of the 62 kidneys evaluated showed severe nephromegaly, and 10 had focal renal masses. With CT diagnosis of ALN as the reference standard, the sensitivity of severe nephromegaly was 90.0% and the specificity was 86.4%. When the focal renal mass was added as a combining predictor, the sensitivity further increased to 95%.

Pediatric ALN was effectively predicted using sonographic findings of severe nephromegaly and/or focal mass before CT scanning.