A 55-year-old man is being evaluated for fatigue. He has a history of hypertension and chronic low back pain due to a traumatic injury 20 years ago. His medications include lisinopril and over-the-counter pain medications. His father has diabetes and his mother has hypertension. He does not use tobacco, alcohol, or illicit drugs. His blood pressure is 130/80 mm Hg and pulse is 80/min. Physical examination is unremarkable. Laboratory studies are as follows: Laboratory studies show serum creatinine level of 2.2 mg/dL and blood urea nitrogen of 34 mg/dL. Which of the following is the most likely cause of this patient's urinary findings?

Question

A 55-year-old man is being evaluated for fatigue.  He has a history of hypertension and chronic low back pain due to a traumatic injury 20 years ago.  His medications include lisinopril and over-the-counter pain medications.  His father has diabetes and his mother has hypertension.  He does not use tobacco, alcohol, or illicit drugs.  His blood pressure is 130/80 mm Hg and pulse is 80/min.  Physical examination is unremarkable.  Laboratory studies are as follows:  Laboratory studies show serum creatinine level of 2.2 mg/dL and blood urea nitrogen of 34 mg/dL.  Which of the following is the most likely cause of this patient's urinary findings?

Quizplus · Accepted Answer

11ec25c8_d4ce_9d4e_bc81_155d3ebb82d5_MD0003_00 This patient's abnormal urinalysis (painless hematuria, sterile pyuria, white blood cell casts, trace proteinuria) suggests a non-glomerular disorder affecting the tubulointerstitium or lining of the urinary tract. Given his chronic low back pain treated with over-the-counter analgesics, he likely has analgesic nephropathy. Chronic analgesic use with 1 or more analgesics (eg, nonsteroidal anti-inflammatory drug such as aspirin) can cause chronic kidney disease due to chronic tubulointerstitial nephritis. Patients are typically asymptomatic with an elevated creatinine found incidentally. Patients can also develop painless and prominent hematuria due to papillary ischemia from analgesic-induced vasoconstriction of medullary blood vessels (vasa recta). Significant papillary necrosis and sloughing may cause renal colic. (Choice A) Glomerulonephritis is typically accompanied by more characteristic abnormalities seen on urine studies (dysmorphic red blood cells, subnephrotic/nephrotic range proteinuria, and red blood cell casts). However, this patient's predominant presence of urine white blood cells suggests an interstitial nephritis. (Choice B) Nephrolithiasis usually presents with renal colic accompanied by hematuria. However, nephrolithiasis is typically not associated with trace proteinuria, pyuria, or acute kidney injury unless there is infection or bilateral obstruction. (Choice D) Urinary tract infection presents with dysuria, fever/chills, abdominal pain, and pyuria (with positive leukocyte esterase or nitrite). (Choice E) Malignancy typically presents with painless hematuria but is less likely in this patient without tobacco use or family history of cancer. Urothelial malignancy rarely causes trace proteinuria, pyuria, or chronic kidney disease. Educational objective: Long-term analgesic use with 1 or more analgesics (eg, nonsteroidal anti-inflammatory drug such as aspirin) can cause chronic kidney disease due to tubulointerstitial nephritis and hematuria due to papillary necrosis. References: Analgesic nephropathy (http://www.ncbi.nlm.nih.gov/pubmed/9601134)

A 55-Year-Old Man Is Being Evaluated for Fatigue