What is the evaluation and management approach for a patient with dysmorphic Red Blood Cells (RBCs) on urinalysis?

From the Guidelines

The evaluation and management of a patient with dysmorphic red blood cells (RBCs) on urinalysis should focus on identifying and treating the underlying glomerular pathology, with an initial workup including a comprehensive metabolic panel, complete blood count, urine protein-to-creatinine ratio, and a 24-hour urine collection to quantify protein excretion, as recommended by the most recent guidelines 1.

Key Components of Evaluation

• A detailed history and physical examination should be performed to assess risk factors for genitourinary malignancy, medical renal disease, and other causes of microhematuria, as outlined in the 2025 AUA/SUFU guideline 1.
• Serologic testing should assess for autoimmune conditions, including anti-nuclear antibody (ANA), anti-neutrophil cytoplasmic antibodies (ANCA), anti-glomerular basement membrane antibodies, complement levels (C3, C4), and screening for hepatitis B, hepatitis C, and HIV.
• Imaging studies, such as renal ultrasound, should be used to evaluate kidney size and structure.
• A renal biopsy may be necessary for definitive diagnosis, especially if there are signs of rapidly progressive glomerulonephritis or significant proteinuria, as suggested by the KDIGO clinical practice guideline commentary 1.

Management Approach

• Management depends on the underlying cause but may include immunosuppressive medications such as corticosteroids (prednisone 1 mg/kg/day), cyclophosphamide, rituximab, or mycophenolate mofetil.
• Blood pressure control is essential, typically with ACE inhibitors or ARBs, which also help reduce proteinuria.
• Regular monitoring of renal function, urinalysis, and proteinuria is necessary to assess treatment response.

Importance of Dysmorphic RBCs

• The presence of dysmorphic RBCs indicates glomerular inflammation or damage, which distinguishes it from lower urinary tract bleeding that produces normal-shaped RBCs, as noted in the AUA guideline 1.
• The evaluation of hematuria, including the examination of urine sediment for dysmorphic RBCs, is an essential tool for nephrologists, as emphasized in the KDIGO commentary 1.

From the Research

Evaluation Approach

The evaluation approach for a patient with dysmorphic Red Blood Cells (RBCs) on urinalysis involves several steps:

• Assessing the presence and percentage of dysmorphic RBCs in the urine, as studies have shown that a higher percentage of dysmorphic RBCs is associated with glomerulonephritis (GN) 2, 3
• Evaluating the patient's renal function and performing a kidney biopsy if necessary, as dysmorphic RBCs can indicate glomerular disease 2, 4
• Conducting a thorough urological evaluation, including cystoscopy and computed tomography (CT) imaging, to rule out urological diseases, as some studies suggest that urological diseases can also present with dysmorphic RBCs 3
• Assessing the patient's proteinuria levels, as the presence of proteinuria can be a stronger indicator of glomerular disease than dysmorphic RBCs alone 2, 3

Diagnostic Value

The diagnostic value of dysmorphic RBCs in evaluating microscopic hematuria is modest, with a sensitivity of 20.4% and specificity of 96.3% for glomerular disease 2

• The presence of dysmorphic RBCs can indicate glomerular bleeding, but it is not a definitive diagnostic tool, as other studies have shown that dysmorphic RBCs can also be present in urological diseases 3, 5
• The percentage of dysmorphic RBCs can vary depending on the methodology used, with some studies suggesting that a concentration technique can increase the sensitivity of RBC cast identification 4

Clinical Implications

The clinical implications of dysmorphic RBCs on urinalysis are significant, as they can indicate underlying glomerular disease or urological conditions:

• Patients with dysmorphic RBCs should undergo further evaluation, including renal function tests and kidney biopsy if necessary, to determine the underlying cause of the hematuria 2, 4
• Urological evaluation should not be omitted in patients with dysmorphic RBCs, as treatment-requiring urological diseases can be present 3
• The presence of proteinuria and hematuria can be a stronger indicator of glomerular disease than dysmorphic RBCs alone, and should be taken into account when evaluating patients with microscopic hematuria 2, 5