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HEMATURIA

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Microscopic hematuria: Greater than five RBCs per high-powered-field in a urine sample

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EPIDEMIOLOGY

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  • Microscopic hematuria: 3–4% incidence on single urine sample; falls to 1% or less for two or more positive samples

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DIFFERENTIAL DIAGNOSIS

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Red Urine with a Negative Dipstick for Blood
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  • Medications: Chloroquine, deferoxamine, metronidazole, nitrofurantoin, pyridium, rifampin, salicylates, doxorubicin

  • Dyes: Fruits/vegetables (beets, blackberries, food coloring)

  • Metabolites: Melanin, methemoglobin, porphyrin, urates, tyrosinosis

  • Bacteria: Serratia urinary tract infection (some strains produce a red/burgundy pigment)

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Positive Urine Dipstick for Blood, but Absence of Red Blood Cells
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  • Hemoglobin: Suggests a hemolytic process

  • Myoglobin: Associated with rhabdomyolysis from trauma, infection, prolonged seizures, or severe electrolyte abnormalities

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Repeatedly Positive Urine Dipstick for Blood and Presence of Red Blood Cells (Hematuria)
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  • Urinary tract: Cystitis/urethritis, hypercalciuria, urolithiasis, trauma, coagulopathy, sports hematuria (may be traumatic or nontraumatic, the latter due either to increased filtration pressure or to increased glomerular permeability as a result of hypoxic damage to the nephron as blood is redistributed to contracting skeletal muscles)

  • Kidney, non-glomerular: Acute tubular necrosis (ATN), interstitial nephritis, pyelonephritis, sickle cell disease or trait, cysts, tumors (e.g., Wilms), trauma, vascular anomalies (e.g., renal vein thrombosis)

  • Kidney, glomerular: Glomerulonephritis (GN, see section below)

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PATHOPHYSIOLOGY

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  • Lesions in the glomerulus, renal interstitium, vasculature, or urinary tract result in bleeding or leakage of red blood cells into urinary tract

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CLINICAL MANIFESTATIONS

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  • Glomerular hematuria typically presents with brown or cola-colored urine with RBC casts, dysmorphic RBCs, and proteinuria

  • Urinary tract or vascular causes present with gross hematuria occasionally with blood clots, eumorphic RBCs (normal appearing), and absent or minimal proteinuria

  • Hypertension, edema, and/or acute kidney injury (AKI) suggest acute GN

  • Abdominal mass suggests tumor, hydronephrosis, polycystic kidney disease, or obstruction

  • Certain rashes are associated with Henoch–Schönlein purpura (HSP) or systemic lupus erythematosus (SLE)

  • Fever and dysuria suggest a urinary tract infection (UTI)

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DIAGNOSTICS

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The diagnostic pathway depends on whether there is gross or microscopic hematuria as well as other abnormal findings. Begin with a urinalysis with microscopy as well as a thorough history and physical exam.

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  • Microscopic hematuria: In the absence of RBC casts, proteinuria, hypertension, AKI, or other concerning clinical signs, repeat urinalysis weekly ×2 (without exercise)

  • Gross hematuria with proteinuria, dysmorphic RBCs, RBC casts, hypertension, or AKI indicates glomerular origin: Send serum electrolytes, BUN, creatinine, CBC with differential, and C3/C4. If suspect postinfectious GN, send ASO and/or anti-DNase B titers. Consider further evaluation such as antineutrophil antibody and antineutrophil cytoplasmic antibody based on clinical presentation

  • Gross hematuria without proteinuria or RBC casts: Suggests an extraglomerular origin. Urine culture if symptoms of infection; renal/bladder ultrasound always indicated to evaluate for stones, tumors, and other structural lesions; consider abdominal CT if ...

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