What could be causing brown urine in a patient, potentially with a history of liver disease or kidney problems, and how should it be evaluated and treated?

Brown Urine: Evaluation and Management

Brown urine requires immediate evaluation to distinguish between benign causes and serious conditions such as liver disease, rhabdomyolysis, or hemolysis—the specific shade and associated findings guide the diagnostic approach. 1, 2

Initial Assessment and Color Characterization

The specific shade of brown provides critical diagnostic clues:

• Tea-colored or cola-colored urine strongly suggests a glomerular source of bleeding with hemoglobinuria or myoglobinuria, requiring immediate evaluation for glomerulonephritis or rhabdomyolysis 3, 2
• Dark brown or amber urine in the context of liver disease suggests bilirubinuria from conjugated hyperbilirubinemia, particularly when accompanied by pale stools and jaundice 4, 1
• Reddish-brown urine may indicate myoglobinuria from rhabdomyolysis, especially following trauma, prolonged immobilization, or excessive muscle activity 4, 2

Critical Immediate Diagnostic Steps

Dipstick and Microscopic Urinalysis

• Perform dipstick testing immediately to detect blood, protein, bilirubin, and urobilinogen—a positive blood reaction without RBCs on microscopy suggests hemoglobinuria or myoglobinuria 3, 2
• Confirm with microscopic examination showing ≥3 RBCs per high-power field to distinguish true hematuria from hemoglobinuria or myoglobinuria 4, 3
• Examine for dysmorphic RBCs (>80%) or red cell casts, which are pathognomonic for glomerular disease and require immediate nephrology referral 4, 3

Essential Laboratory Evaluation

• Serum creatinine, BUN, and complete metabolic panel to assess renal function and detect hepatorenal syndrome in cirrhotic patients 4
• Creatine kinase (CK) if rhabdomyolysis is suspected—levels >1,000 U/L with myoglobinuria indicate significant muscle injury requiring aggressive hydration 4
• Liver function tests including total and direct bilirubin, AST, ALT, alkaline phosphatase, and albumin if liver disease is suspected 4
• Complete blood count to evaluate for hemolytic anemia if hemoglobinuria is suspected 5

Liver Disease Context: Hepatorenal Syndrome Considerations

In patients with known cirrhosis presenting with brown urine:

• Brown urine with oliguria suggests acute kidney injury (AKI), which develops in approximately 20% of hospitalized cirrhotic patients and carries 15% one-year mortality 4
• Withdraw all diuretics immediately and discontinue beta-blockers, NSAIDs, and nephrotoxic medications 4
• Administer albumin 1 g/kg (maximum 100 g) for two consecutive days if AKI stage >1A is present, while carefully monitoring for pulmonary edema 4
• Screen for infection with blood cultures, urinalysis, and diagnostic paracentesis if ascites is present, as spontaneous bacterial peritonitis precipitates 30% of AKI cases in cirrhosis 4

If brown urine persists despite volume expansion and serum creatinine remains >0.3 mg/dL above baseline, suspect hepatorenal syndrome-AKI and initiate vasoconstrictor therapy with terlipressin plus albumin 4

Rhabdomyolysis Management Protocol

When myoglobinuria is confirmed (positive dipstick for blood without RBCs, elevated CK):

• Initiate aggressive IV hydration immediately with normal saline at 200-300 mL/hour to maintain urine output >200-300 mL/hour and prevent acute tubular necrosis 4
• Monitor serum potassium closely as hyperkalemia from muscle breakdown can cause life-threatening dysrhythmias 4
• Consider urine alkalinization with sodium bicarbonate to maintain urine pH >6.5, which reduces myoglobin precipitation in renal tubules 4
• Continue forced diuresis until CK normalizes and urine clears—failure to clear brown urine despite adequate hydration suggests ongoing muscle injury 4

Glomerular Disease Evaluation

If tea-colored urine with proteinuria and dysmorphic RBCs:

• Quantify proteinuria using spot urine protein-to-creatinine ratio—values >0.2 g/g indicate significant glomerular disease requiring nephrology referral 4, 6
• Measure complement levels (C3, C4) to evaluate for post-infectious glomerulonephritis or lupus nephritis 4
• Obtain ANA and ANCA testing if vasculitis is suspected based on systemic symptoms 4
• Immediate nephrology referral is mandatory for red cell casts, >80% dysmorphic RBCs, or rapidly declining renal function 4, 3

Hemoglobinuria from Hemolysis

When hemoglobinuria is suspected (positive dipstick without RBCs, no elevated CK):

• Evaluate for paroxysmal nocturnal hemoglobinuria (PNH) with flow cytometry for CD55 and CD59 deficiency, particularly if recurrent episodes of dark urine occur 5
• Assess for intravascular hemolysis with lactate dehydrogenase (LDH), haptoglobin, indirect bilirubin, and peripheral smear 5
• Consider mechanical hemolysis from prosthetic heart valves or march hemoglobinuria from vigorous exercise 5

Common Pitfalls to Avoid

• Never attribute brown urine solely to dehydration or medications without confirming the diagnosis—serious conditions like rhabdomyolysis or glomerulonephritis require immediate intervention 1, 2
• Do not delay evaluation in cirrhotic patients as AKI progression significantly worsens prognosis and 44% of patients with ascites die within 5 years 4
• Avoid over-transfusion in bleeding cirrhotic patients—maintain hemoglobin at 7-9 g/dL to prevent volume overload and worsening portal hypertension 4
• Do not assume anticoagulation explains brown urine—these medications may unmask underlying pathology but do not cause discoloration themselves 3

Urgent Referral Criteria

• Immediate nephrology referral for red cell casts, >80% dysmorphic RBCs, protein-to-creatinine ratio >0.2 g/g, or rapidly declining eGFR 4, 3, 6
• Urgent hepatology consultation for cirrhotic patients with AKI not responding to albumin and volume expansion within 48 hours 4
• ICU admission for rhabdomyolysis with CK >5,000 U/L, hyperkalemia, or oliguria despite aggressive hydration 4