Hematuria: Causes, Mechanism & Diagnosis

Hematuria: Causes, Mechanism & Diagnosis

Hematuria is the presence of blood in the urine, a warning sign of urinary tract problems, particularly kidney issues.

Pathogenesis:

Hematuria occurs due to one of three main causes:

• Glomerular filtration membrane damage: The glomerular filtration membrane is damaged, allowing red blood cells to leak into the urine.

• Tubular damage: Causes of tubular damage include:

• Cast obstruction: Deposits in the renal tubules cause obstruction, damaging the tubules.

• Oxidative stress: Oxidative stress damages mitochondria, leading to impaired renal tubule function.

• Increased capse activity: Increased capse activity causes apoptosis (cell death) in renal tubular cells.

• Increased cytokine production: Cytokines cause inflammation, damaging the renal tubules.

• Damage to the mucosal surface: Damage to the urinary tract mucosa due to kidney stones, tumors, infections, or trauma can cause hematuria.

Diagnosis of Hematuria:

• Principle: Red blood cells in urine contain hemoglobin (Hb). Hb catalyzes organic peroxide, causing oxidation and turning the reagent blue.

• False positives: False positive test results can occur due to:

• Oxidizing agents in urine.

• Hb, Mb (myoglobin) in urine.

• False negatives: False negative test results can occur due to:

• Ascorbic acid in urine.

• Urine left standing for too long.

• Dilute urine.

• Urine pH < 5.

Classification of Hematuria:

• Acanthocyte > 5%: Suggests a glomerular origin of hematuria.

• Initial hematuria: Suggests a lesion in the urethra.

• Terminal hematuria: Suggests a lesion in the bladder.

• Total hematuria: Suggests a lesion in the kidney or ureter.

Causes of Glomerular Hematuria:

• Post-streptococcal glomerulonephritis.

• IgA nephropathy.

• Thin basement membrane disease.

• Lupus nephritis.

• Henoch Schonlein purpura.

Red Urine Not Hematuria:

• Not from the urinary tract: Blood may originate from the reproductive tract or digestive tract.

• Not red blood cells:

• Red-colored food.

• Medications: Rifampicin, vitamin B12, methyldopa.

• Hemoglobinuria, myoglobinuria.

3-Hour Urine Sample:

• Purpose: Quantify urine sediment (Addis count).

Renal Biopsy:

• Indications:

• Proteinuria.

• Acute renal failure.

• Rapidly progressive renal failure.

Note:

Hematuria is a serious sign and requires prompt diagnosis and treatment to avoid dangerous complications.