What is the next step in managing a 32-year-old man with hematuria (presence of red blood cells in urine), cellular casts, and significant proteinuria, who is taking Xarelto (rivaroxaban) for atrial fibrillation and has a normal renal ultrasound?

Management of Hematuria with Proteinuria and Cellular Casts

The next step in managing this 32-year-old man with hematuria, cellular casts, and 3+ proteinuria should be a nephrology referral for evaluation of primary renal disease, including consideration of renal biopsy. 1

Clinical Findings Indicating Glomerular Disease

• The presence of RBCs (4 per high power field), cellular casts, and significant proteinuria (3+) strongly suggests glomerular disease requiring nephrology evaluation 1
• Cellular casts are highly specific for glomerular or tubulointerstitial kidney disease and warrant thorough evaluation 1
• The combination of proteinuria and hematuria significantly increases the likelihood of primary renal disease compared to either finding alone 1
• 3+ proteinuria likely represents significant protein excretion (>1g/day) which meets criteria for nephrology referral 1

Recommended Diagnostic Approach

• Quantify proteinuria with a 24-hour urine collection to determine exact protein excretion (a total protein >1g/day definitively warrants nephrology referral) 1
• Assess renal function with serum creatinine and estimated GFR 1
• Evaluate for systemic diseases associated with glomerulonephritis including:
  • Lupus erythematosus
  • Vasculitis
  • Infections such as hepatitis and endocarditis 1
• Consider primary glomerular diseases such as:
  • IgA nephropathy
  • Membranoproliferative glomerulonephritis
  • Crescentic glomerulonephritis 1

Importance of Renal Biopsy

• Renal biopsy is usually recommended when systemic causes are not identified in patients with findings suggestive of glomerular disease 1
• Biopsy findings help determine specific diagnosis, prognosis, and guide treatment decisions 1
• The presence of cellular casts with significant proteinuria strongly suggests the need for histological evaluation 1

Special Considerations with Rivaroxaban (Xarelto)

• The patient's use of rivaroxaban for atrial fibrillation requires careful consideration when planning invasive procedures like renal biopsy 2
• Temporary discontinuation of rivaroxaban will be necessary before renal biopsy, with appropriate bridging anticoagulation if needed 2
• Rivaroxaban may need dose adjustment based on renal function if kidney disease is confirmed 2

Pitfalls to Avoid

• Do not attribute hematuria solely to anticoagulation therapy (Xarelto) when cellular casts and significant proteinuria are present, as these findings suggest intrinsic renal disease 1
• Avoid relying solely on dipstick proteinuria without quantification, as false positives can occur with high specific gravity and hematuria 3
• Do not delay nephrology referral when cellular casts and significant proteinuria are present, as early intervention may prevent disease progression 1
• Remember that normal renal ultrasound does not exclude glomerular disease, which requires histological diagnosis 1

Long-term Monitoring

• After diagnosis and initial treatment, patients require monitoring of:
  • Proteinuria levels (target <1g/day indicates better prognosis) 1
  • Blood pressure (target <125/75 mmHg with proteinuria >1g/day) 1
  • Renal function 1