This patient most likely has analgesic-induced nephropathy. Analgesic-induced nephropathy can present with florid nephrotic range proteinuria. This often results from nonsteroidal antiinflammatory medications which cause a reversible decline in renal blood flow and glomerular filtration rate due to the inhibition of vasodilatory prostaglandin production. NSAIDs can also produce acute interstitial nephritis, wherein a kidney biopsy would show minimal changes and a typical interstitial inflammatory pattern.
Chronic necrosis of the renal papilla with calcification is typically seen. However, sloughing of the papilla may cause hematuria and present acutely as renal colic, as in this patient. Urine studies usually show hematuria, proteinuria, and pyuria with white blood cell casts, whereas the urine culture is usually sterile. The associated microcytic anemia in this patient is out of proportion to the renal dysfunction and is possibly due to gastrointestinal blood loss from NSAID-induced chronic gastric irritation. Discontinuation of the analgesic will cause stabilization or even improvement in renal function.
A 70-year-old white male presents to the office because of worsening fatigue, nausea, malaise, and bilateral pedal edema. He also complains of a decreased appetite for the past six weeks. Four weeks ago, he had an upper respiratory tract infection that resolved with over-the-counter medications. He describes his degenerative joint disease as moderately severe, and for which, he has been taking ibuprofen for the past year. His other daily medications for the past six years are metoprolol, hydrochlorothiazide, hydralazine, and simvastatin. He has no known drug allergies. He has a 50-pack-year history of smoking, and occasionally drinks alcohol. His family history is significant for strokes. His labs on this office visit show the following:
Serum creatinine 5.2 mg/dL
His urine analysis shows: 4+ protein, 0-1 RBC/HPF, 20-25 WBC/HPF, and a few granular casts. His 24-hour urine protein is 7 g. Ultrasound of the kidneys is unremarkable. His antinuclear antibody titers are 1:40. During his previous visit one year ago, the creatinine was 1.2. Which of the following is the most likely cause of his presentation?
PSGN: Even though this patient had a recent upper respiratory tract infection, this does not explain glomerulonephritis. The patient has nephrotic range proteinuria, no RBCs or RBC casts in the urine analysis.
Hydralazine lupus: Hydralazine can cause drug-induced lupus; however, the drug-induced lupus usually does not cause renal failure.