Summary

Background: Acute focal nephritis is an inflammatory process of the renal parenchyma affecting principally the cortex of the kidney. It is considered a midpoint in the spectrum of upper urinary tract infections, ranging from uncomplicated pyelonephritis to intrarenal abscesses, and until recently the hyperechoic sonographic appearance of this lesion was considered uncommon.  

Objectives: To determine the relative prevalence of hyperechoic and hypoechoic sonographic appearance of focal renal lesions in patients with the clinical diagnosis of acute pyelonephritis and to correlate the findings with those of the color Doppler examinations.

Methods: We reviewed the sonograms of 367 patients hospitalized with the clinical diagnosis of acute pyelonephritis. The sonograms were reviewed for acute renal inflammatory changes. When a focal lesion was detected, we noted the echogenicity, side, form, location and color Doppler characteristics.

Results: Abnormal sonographic findings related to the infection were found in 78 cases. In 52 patients a focal lesion was diagnosed. Forty-seven focal lesions appeared hyperechoic related to the adjacent parenchyma. These lesions were more frequently located at the upper pole and were wedge-shaped in most of the cases. The areas appeared hypo/avascular on the color Doppler examination.

Conclusions: Our data suggest that the most common appearance of acute focal nephritis is an area of increased echogenicity in the parenchyma of the affected kidney.