Emphysematous Pyelonephritis

Photoclinic
Foresee Your Next Patient

For 4 days, a 62-year-old woman with type 2 diabetes mellitus had constant, severe, crampy abdominal pain associated with nausea, non-bloody emesis, and anorexia, but not fever. She reported that the pain had an insidious onset and was exacerbated by urination. Dysuria began 2 weeks before the onset of pain.

The patient’s temperature was 35.4°C (95.7°F); blood pressure, 105/61 mm Hg; pulse, 122 beats per minute; respiration rate, 24 breaths per minute; and glucose level, 450 mg/dL. The patient was awake, alert, and appropriately oriented. The physical examination was notable for a soft, obese abdomen with mild bilateral upper quadrant tenderness on deep palpation.

White blood cell count was 17,300/µL with 86% neutrophils and 9% bands; platelet count, 157,000/µL; blood urea nitrogen level, 64 mg/dL; and creatinine level, 5 mg/dL. Urinalysis showed 3+ proteinuria, glycosuria, positive leukocyte esterase, as well as pyuria and bacteria. A CT scan of the abdomen revealed an enlarged, nonhydronephrotic right kidney with perinephric stranding, gas within the cortex (thick arrow) and perinephric spaces (thin arrow), as well as inflammation and stranding around the right proximal ureter.

The patient was admitted to the ICU for management of emphysematous pyelonephritis (EPN). Her ICU course was notable for the development of diabetic ketoacidosis and septic shock. Pressors, broad-spectrum antibiotics, and insulin were initiated. Blood and urine cultures eventually grew Escherichia coli. Her hospital stay was complicated by the development of oliguric renal failure, which required hemodialysis.

Clinical findings with significant negative prognostic value in EPN are thrombocytopenia, altered mental status, acute renal failure, and shock. Factors such as age, blood glucose level, and site of infection do not have a significant influence on outcome. Characteristics that best predict a favorable outcome are nonobstructive unilateral disease, combined medical and surgical treatment, and short interval between symptom onset and initiation of therapy.¹

EPN is usually diagnosed by CT and classified based on imaging findings²:
•Class 1, gas in the collecting system only.
•Class 2, gas in the renal parenchyma without extension to the extrarenal space.
•Class 3A, extension of gas or abscess to the perinephric space.
•Class 3B, extension of gas or abscess to the pararenal space.
•Class 4, bilateral EPN or a solitary kidney with disease.

For classes 1 and 2, combined antibiotic therapy and percutaneous nephrostomy tube drainage (PCD) have a success rate of 66%, while the mortality rate for treatment with antibiotics alone ranges from 40% to 90%.^1,3 For classes 3 and 4, with 2 or fewer negative prognostic indicators, antibiotic therapy and PCD may be attempted but ultimately nephrectomy may be necessary.^1,4 With more than 2 negative prognostic indicators, nephrectomy is recommended. The success rate of nephrectomy was 90% when attempted in one study.¹

Given that this patient’s EPN was class 3B, with 2 negative prognostic indicators, nephrectomy was considered because of her critical condition; however, she instead underwent PCD and antibiotic therapy for kidney preservation. Serial CT scans showed substantial improvement. She was discharged home on ciprofloxacin and scheduled for continued hemodialysis. 

EPN should be suspected in patients with diabetes and/or urinary tract obstruction with acute renal failure and E coli or Klebsiella pneumoniae infection. Although EPN is rare, the projected growth of the diabetic population warrants increased attention to this potentially fatal disease. ■