Fig. 17. A diabetic patient with gas-containing perirenal abscess presenting with right flank pain, fever and chills.

A. The lesion was not diagnosed by ultrasonography initially. B. Axial contrast-enhanced computed tomography performed one day after ultrasound shows right perirenal abscess with thick enhanced fascia (white arrows), gas contents (black arrows) and fluid collections that were not well detected by initial ultrasonography (A). P, abscess in the perirenal space; RK, right kidney.