Case presentation:

A 29-year-old woman with a history of insulin-dependent diabetes mellitus was treated for a urinary tract infection. Twelve days later, she presented with persistent flank pain.

Physical exam showed:
She was a moderately ill-appearing woman who was afebrile with a heart rate of 100, respiratory rate of 16, and BP of 170/100. She did not appear to be dehydrated. There was costo-vertebral angle tenderness on the left and left lower quadrant (abdominal) tenderness with guarding, but without rebound tenderness.

Laboratory results: 

Serum electrolytes           White blood cells    10,700/ul
Sodium         127 meq/l           Neutrophils        70%
Potassium        5                 Bands              12%
Chloride        92
Bicarbonate     17           Urinalysis
                                   Appearance      Pink/cloudy
Glucose        640 mg/dl           Glucose         2+
BUN             32                 Ketones         1+
Creatinine     1.6                 Protein         3+
                                   Sediment        Many RBC, rare bacteria
                                                   25 WBC/HPF
Blood and urine cultures negative

Questions:

  1. What is the probable cause of the patient's renal problem?
  2. How does the urinalysis support this diagnosis?
  3. What do you think the decreased bicarbonate value (normal = 24) means?
  4. What do you think of the patient's BUN and creatinine values?