A 24-year-old man comes to the urgent care clinic due to blood in his urine. He has a 1-day history of mild midline back discomfort, associated with a single episode of red urine. The hematuria subsequently resolved and his urine is now a normal yellow color. The patient also has had a sore throat for the past 4 days, for which he took 3 tablets of over-the-counter acetaminophen. He has had no fever, abdominal pain, or burning during urination. He has smoked 1 pack of cigarettes daily for 5 years. Physical examination is unremarkable. Urinalysis shows: Which of the following is the most likely source of this patient's urinary complaints?

Question

A 24-year-old man comes to the urgent care clinic due to blood in his urine.  He has a 1-day history of mild midline back discomfort, associated with a single episode of red urine.  The hematuria subsequently resolved and his urine is now a normal yellow color.  The patient also has had a sore throat for the past 4 days, for which he took 3 tablets of over-the-counter acetaminophen.  He has had no fever, abdominal pain, or burning during urination.  He has smoked 1 pack of cigarettes daily for 5 years.  Physical examination is unremarkable.  Urinalysis shows:  Which of the following is the most likely source of this patient's urinary complaints?

Quizplus · Accepted Answer

11ec25c8_d10f_99e5_bc81_cb54f00a1c78_MD0003_00 Hematuria can be due to glomerular or non-glomerular causes. Non-glomerular hematuria is more common; it is characterized by gross hematuria with normal-appearing red blood cells (RBCs) but without significant proteinuria. Etiologies include cancer (eg, renal cell, prostate), infections (eg, cystitis), polycystic kidney disease, and nephrolithiasis. Patients frequently have specific urinary symptoms (eg, dysuria, flank pain, renal colic) that help to clarify the diagnosis. In contrast, glomerular hematuria usually causes microscopic hematuria, though gross hematuria may be present in some cases. It is usually due to glomerulonephritis (GN) or basement membrane disease. Symptoms are usually absent or nonspecific (eg, low back pain), and patients may present after developing features of nephritic syndrome (eg, hematuria, hypertension, oliguria, elevated creatinine). Urinalysis usually shows proteinuria with dysmorphic RBCs or RBC casts. This patient, with proteinuria and transient gross hematuria following acute pharyngitis, most likely has IgA nephropathy, which is the most common GN in adults. IgA nephropathy is typified by hematuria starting within 5 days of an upper respiratory or pharyngeal illness (synpharyngitic GN). (Choice B) Prostate carcinoma, benign prostatic hypertrophy (BPH), or prostatitis can cause non-glomerular hematuria. Prostate carcinoma and BPH usually present in men age >55, often with symptoms of urinary tract obstruction. However, prostatitis is unlikely as this patient had no evidence of urinary tract infection (negative leukocyte esterase, nitrite, and white blood cells). (Choice C) Renal tumors or malignancies (eg, renal cell cancer) involving the interstitium can present as non-glomerular hematuria. However, proteinuria would not be typically seen with this condition. (Choice D) Papillary necrosis with sloughing of the renal papilla is a rare cause of non-glomerular hematuria. It may be seen with long-term acetaminophen abuse but not with light-intermittent use (mnemonic NSAID: Nonsteroidal antiinflammatory drugs, Sickle cell disease, Analgesic abuse, Infection (pyelonephritis), and Diabetes mellitus). (Choice E) Acute tubular necrosis is characterized by acute azotemia following a hypotensive or nephrotoxic injury. Patients may have dark or cola-colored urine, but significant hematuria is uncommon. Tubulointerstitial nephritis causes microscopic hematuria associated with elevated creatinine and variable proteinuria. It is most commonly due to certain medications including antibiotics, NSAIDs, and diuretics. (Choice F) Urinary bladder tumor, carcinoma, or cystitis can present as non-glomerular hematuria. While smoking is a risk factor for bladder carcinoma, this malignancy is rarely seen in younger adults (age <55). And cystitis is unlikely as this patient had no evidence of urinary tract infection. Educational objective: Hematuria (gross or microscopic) can be due to glomerular or non-glomerular causes. The source of hematuria is more likely to be glomerular if the urine studies reveal proteinuria, dysmorphic red blood cells (RBCs) or RBC casts. References: Assessment of microscopic hematuria in adults. (http://www.ncbi.nlm.nih.gov/pubmed/16734050)

A 24-Year-Old Man Comes to the Urgent Care Clinic Due