A 60-year-old female diabetic patient presented with fever, dysuria and abdominal pain.

Non-contrast CT abdomen demonstrated air in the left renal calyces, renal pelvis and ureter. No parenchymal air pockets / perinephric inflammation noted. These imaging features are consistent with emphysematous pyelitis.

Emphysematous pyelitis refers to air in the pelvicalyceal system usually secondary to anaerobic infection. Preexisting diabetes is a risk factor. It can also be secondary to trauma, recent urinary tract intervention procedures or fistula between urinary and gastrointestinal system. 

Differentiation between emphysematous pyelitis and emphysematous pyelonephritis is of utmost importance as the latter has higher mortality rates.