What causes brown urine and how is it treated?

Brown Urine: Causes and Treatment

Brown urine most commonly results from concentrated urine, medications, or foods, but can indicate serious conditions including acute porphyria, hemoglobinuria, myoglobinuria, or liver disease—diagnosis requires urinalysis with dipstick and microscopy to differentiate these causes. 1, 2

Immediate Diagnostic Approach

Initial Evaluation

• Obtain urinalysis with dipstick testing to assess for blood, protein, bilirubin, and urobilinogen 1, 2
• Perform microscopic examination to differentiate hematuria (≥3 RBCs/HPF), hemoglobinuria, or myoglobinuria 3, 4
• Check urine specific gravity and pH as concentration and acidity affect color 2

Key Differentiating Features on Dipstick

• Positive blood on dipstick WITHOUT red blood cells on microscopy suggests hemoglobinuria or myoglobinuria rather than true hematuria 4, 5
• Positive bilirubin and/or urobilinogen indicates hepatobiliary disease 1, 2
• Dipstick measures peroxidase activity and can be confounded by myoglobin, povidone iodine, or dehydration 3

Major Causes of Brown Urine

Acute Porphyria (Red-Brown Color)

• During acute porphyria attacks, urine may appear normal initially but turns red-brown upon standing or exposure to light due to porphobilinogen (PBG) oxidation 6
• PBG/creatinine ratio increases >10 times the upper limit of normal during attacks (or >10 μmol/mmol creatinine by mass spectrometry) 6
• Measure urinary PBG and ALA (aminolevulinic acid) levels if acute neurovisceral symptoms present (abdominal pain, neurological symptoms) 6
• Obtain sample during symptomatic period as PBG excretion may normalize between attacks or after hemin treatment 6

Hemoglobinuria

• Results from intravascular hemolysis with free hemoglobin in urine causing red-brown discoloration 4, 5
• Dipstick positive for blood but microscopy shows few or no intact RBCs 4
• Consider paroxysmal nocturnal hemoglobinuria if recurrent episodes of dark urine, especially in morning 4
• Check serum for hemolysis markers (elevated LDH, low haptoglobin, elevated indirect bilirubin) 4

Myoglobinuria

• Occurs with rhabdomyolysis from trauma, prolonged immobilization, or muscle injury 5
• Serum creatine kinase elevated up to 150 times normal in severe cases 5
• Monitor serum creatinine and BUN as myoglobinuria can precipitate acute renal failure 5
• Dipstick positive for blood without RBCs on microscopy, similar to hemoglobinuria 5

Concentrated Urine

• Most benign cause of brown urine, particularly in dehydrated patients 1, 2
• High specific gravity (>1.020) confirms concentration 2
• Resolves with adequate hydration 1

Medications and Foods

• Common medications causing brown urine include metronidazole, nitrofurantoin, methyldopa, and antimalarials 1, 2
• Foods such as fava beans, rhubarb, and aloe can cause brown discoloration 1, 2
• Obtain detailed medication and dietary history 1, 2

Hepatobiliary Disease

• Elevated conjugated bilirubin produces dark brown or tea-colored urine 1, 2
• Positive bilirubin on dipstick with or without urobilinogen elevation 2
• Check liver function tests if bilirubin detected in urine 1

Treatment Approach

For Acute Porphyria

• Administer hemin (hematin) as standard treatment for acute attacks 6
• Avoid triggering factors including certain medications, fasting, and alcohol 6
• PBG excretion may normalize during or shortly after hemin treatment 6

For Hemoglobinuria/Myoglobinuria

• Aggressive intravenous hydration to prevent acute tubular necrosis and renal failure 5
• Monitor renal function closely (serum creatinine, BUN) 5
• Treat underlying cause of hemolysis or rhabdomyolysis 4, 5

For Medication-Related Discoloration

• Reassure patient if benign medication effect confirmed 1, 2
• Consider alternative medication if discoloration causes significant distress 1

For Concentrated Urine

• Increase fluid intake to achieve adequate hydration 2
• No specific treatment required beyond hydration 1

Critical Pitfalls to Avoid

• Do not assume brown urine is simply concentrated urine without performing urinalysis 1, 2
• Do not rely solely on dipstick results—microscopic confirmation is essential to differentiate hematuria from hemoglobinuria/myoglobinuria 3, 4
• Do not miss acute porphyria—obtain PBG levels if patient has acute neurovisceral symptoms, as delayed diagnosis can be life-threatening 6
• Do not overlook myoglobinuria in trauma patients—supplement routine creatinine/BUN with creatine kinase and rapid myoglobin testing to prevent acute renal failure 5
• Sample timing matters for porphyria diagnosis—collect urine during symptomatic periods as PBG may normalize between attacks 6