Sensitivity of sonography in pyonephrosis: a reevaluation

Area of Science:

• Radiology and Imaging
• Nephrology
• Urology

Background:

• Distinguishing simple hydronephrosis from pyonephrosis is crucial for appropriate patient management.
• Ultrasound is a primary imaging modality for evaluating hydronephrosis.
• Pyonephrosis, a severe infection within a dilated renal collecting system, requires prompt treatment.

Purpose of the Study:

• To evaluate the sonographic features that differentiate simple hydronephrosis from pyonephrosis.
• To assess the sensitivity and specificity of ultrasound in diagnosing pyonephrosis.

Main Methods:

• Retrospective review of 50 patients with hydronephrosis.
• Analysis of sonographic findings, including fluid-fluid levels and internal echoes.
• Correlation of imaging findings with clinical diagnosis.

Main Results:

• Fluid-fluid levels and coarse echoes within the collecting system were reliable indicators of pyonephrosis (100% specificity).
• However, six patients with proven pyonephrosis had anechoic or low-level echoes, mimicking simple hydronephrosis.
• Ultrasound sensitivity for pyonephrosis was 62%, despite 100% specificity.

Conclusions:

• While specific ultrasound findings are highly specific for pyonephrosis, atypical presentations can occur.
• The limited sensitivity necessitates consideration of further diagnostic steps.
• Sonographically guided needle aspiration remains valuable for diagnosing pyonephrosis in patients with urosepsis and significant hydronephrosis.