40 year old male patient came to emergency with history of right lumbar pain and fever, USG Doppler of right kidney shows focal hypoechoic area in upper pole with small anechoic area within. CT scan of the same patient showwed focal hypoenhancing lesion in upper pole of right kidney with small non enhancing area within. These features are suggestive of focal pyelonephritis with evolution of abscess.
Acute focal pyelonephritis (AFP) is a variant of pyelonephritis in which single or multiple discrete areas show changes of inflammation. The sonographic appearances of AFP are varied and can be echogenic, echopoor or of mixed echogenicity, but are typically described as being echopoor. CT typically shows focal hypoenhancing areas. Imaging is done mainly to identify the complications like intra renal and peri renal abscess.