Severe right loin pain in a diabetic patient.

A 48-year-old diabetic woman presented to the United Christian Hospital with fever of acute onset and right loin pain. Physical examination revealed tenderness with a ballotable right kidney. Clinically, the patient was septic with blood pressure on the low side. Laboratory data revealed leukocytosis with a left shift and an elevated creatinine level. A plain kidney, ureter, and bladder (KUB) radiography was obtained upon request (Fig 1). What acute condition was she suffering from?