Review Question - QID 104487

Analgesic nephropathy is commonly caused by long-standing use of analgesics and is the most common cause of drug-induced renal failure. It results in papillary necrosis and chronic tubulointerstitial nephritis.

Analgesic nephropathy may occur as a result of excessive use of analgesics including drugs that contain phenacetin, acetaminophen, NSAIDs, or aspirin. It may manifest as an interstitial nephritis, renal papillary necrosis, or both and can lead to either acute or chronic renal failure. Progression is insidious. Recall that there are multiple causes of hematuria including kidney stones, infection, bladder and kidney cancer, glomerular diseases, trauma, systemic vascular diseases, sickle cell disease, and polycystic kidney disease among many others. The first step in evaluation is a urinalysis.

Thaller and Wang discuss the evaluation of asymptomatic microscopic hematuria in adults. Routine screening for hematuria is not indicated; however, once discovered, its cause should be investigated beginning with a medical history and review of medications. Laboratory and imaging studies, such as intravenous pyelography, renal ultrasonography or retrograde pyelography, may be required to determine the degree and location of the associated disease process.

McDonald et al. discuss the assessment of microscopic hematuria in adults. Hematuria is clinically significant when three to five red blood cells are seen in a high-power field. In several studies less than 10% of patients with asymptomatic microscopic hematuria had an underlying malignancy.

Illustration A represents the histological findings in renal papillary necrosis. Microscopic analysis of these specimens would reveal papillary necrosis with or without a tubulointerstitial nephritis.

Incorrect Answers:
Answer 2: A kidney stone would be more likely to cause painful hematuria. Furthermore, biopsy would not show renal papillary necrosis and chronic tubulointerstitial nephritis.
Answers 3 & 4: Bladder cancer and kidney cancer are both causes of painless hematuria but would be less likely in a young female and given the history of migraines and histological findings, analgesic nephropathy would be the more likely diagnosis. Furthermore, neither would result in papillary necrosis or chronic tubulointerstitial nephritis.
Answer 5: Sickle cell may cause renal papillary necrosis, but would be less likely than analgesic nephropathy given the patient's history of migraines and race.