Diagnostic Evaluation of Numerous RBCs in Urinalysis
For numerous RBCs in urinalysis, the complete urologic evaluation requires upper tract imaging (preferably CT urography) followed by cystoscopy, with the specific pathway determined by whether glomerular or non-glomerular bleeding is present. 1
Initial Characterization of Hematuria
Before proceeding with imaging, you must first determine the source and nature of the bleeding:
- Examine the urinary sediment microscopically to quantify RBCs per high-power field and assess RBC morphology (dysmorphic vs. normal) 2, 1
- Check for RBC casts, which are virtually pathognomonic for glomerular bleeding 1, 3
- Measure proteinuria using dipstick initially, with 24-hour collection if significant (>1g/day indicates glomerular disease) 1
- Obtain serum creatinine and eGFR to assess renal function 1
- Look for dysmorphic RBCs (>75% dysmorphic suggests glomerular origin; <17% suggests non-glomerular) 4
Pathway for Glomerular Hematuria
If you identify dysmorphic RBCs, RBC casts, significant proteinuria, or elevated creatinine:
- Refer to nephrology immediately for concurrent evaluation 1
- Renal biopsy is indicated when systemic causes are not identified 2
- Monitor renal function, proteinuria, and blood pressure regularly 1
- A bladder scanner or KUB alone is insufficient for this population
Pathway for Non-Glomerular (Urologic) Hematuria
This is where your imaging decisions matter most:
Upper Tract Imaging
- Multi-phasic CT urography is the imaging procedure of choice for evaluating the upper urinary tract 1
- CT urography is superior to traditional IVU, ultrasound, or plain KUB for detecting renal cell carcinoma, transitional cell carcinoma, and urolithiasis 2
- A simple KUB radiograph is inadequate as it cannot evaluate renal masses, characterize lesions, or adequately assess the collecting system 2
- Bladder scanner has no role in hematuria evaluation—it only measures post-void residual volume and cannot detect pathology 1
Cystoscopy
- Cystoscopy must be performed on all patients aged 35 years and older with hematuria 1
- Perform cystoscopy regardless of age if risk factors for urinary tract malignancy are present (smoking, occupational chemical exposure, history of gross hematuria, pelvic irradiation, irritative voiding symptoms) 1
- Cystoscopy may be deferred in low-risk patients under age 35 at physician discretion 1
Urine Cytology
- Obtain voided urine cytology in all patients with risk factors for transitional cell carcinoma 2
- Cytology is particularly useful for detecting carcinoma in situ 2
- If malignant or atypical cells are identified, cystoscopy is mandatory 2
Special Considerations
Exclude Benign Causes First
- Repeat urinalysis 48 hours after cessation if history suggests menstruation, vigorous exercise, sexual activity, or trauma 2, 1
- Treat urinary tract infection and repeat UA in 6 weeks—no further evaluation needed if hematuria resolves 2, 1
- In women, perform urethral and vaginal examination to exclude local causes; obtain catheterized specimen if vaginal contamination suspected 2, 1
Anticoagulation
- Do not attribute hematuria solely to anticoagulation—full urologic and nephrologic evaluation is required regardless of anticoagulation status 1
- This is a common pitfall that leads to missed malignancies
Age-Based Approach
- Patients >40 years have significantly higher risk of malignancy and require complete evaluation 5
- In patients ≤40 years with microscopic hematuria and no risk factors, CT or ultrasound may suffice, but add cystoscopy if gross hematuria is present 5
What NOT to Use
- Bladder scanner: Only measures post-void residual; has no diagnostic value for hematuria 1
- KUB alone: Inadequate for detecting renal masses, characterizing lesions, or evaluating collecting system 2
- Ultrasound alone: Limited sensitivity for small renal masses and transitional cell carcinoma 2
- IVU alone: Cannot distinguish solid from cystic masses and requires additional imaging when abnormalities are detected 2