Figure 17a. Emphysematous pyelitis. (a) Abdominal radiograph obtained during the excretory phase of an intravenous urogram with the patient supine demonstrates multiple air bubbles within the renal collecting systems (arrows) and moderate hydronephrosis bilaterally. (b) Delayed tomographic image localized over the distal left ureter demonstrates multiple tiny intramural gas bubbles and a dilated left ureter (arrows).