What is the appropriate management for an adult patient with persistent lower abdominal pain, microscopic hematuria (RBC 3-10 on urinalysis), and a Blood Urea Nitrogen (BUN)/creatinine ratio of 5?

Management of Microscopic Hematuria with Lower Abdominal Pain and Low BUN/Creatinine Ratio

This patient requires urgent urologic evaluation with cystoscopy and CT urography to rule out bladder injury or other serious urologic pathology, given the combination of persistent lower abdominal pain, confirmed microscopic hematuria (RBC 3-10), and an abnormally low BUN/creatinine ratio of 5 that suggests possible urinary tract disruption with urine reabsorption.

Critical Initial Assessment

The BUN/creatinine ratio of 5 is abnormally low (normal ratio is 10-20:1) and raises immediate concern for:

• Bladder rupture with urinary ascites causing "reversed autodialysis" where creatinine diffuses back into the bloodstream faster than urea, lowering the ratio 1
• This occurs when urine leaks into the peritoneal cavity, creating pseudorenal failure with elevated creatinine but disproportionately low BUN 1
• Suprapubic pain and low urine output are clinical indicators of potential bladder rupture that warrant immediate imaging 2

Immediate Diagnostic Steps

Obtain CT cystography with retrograde filling to evaluate for bladder injury:

• Retrograde gravity filling with minimum 300 mL contrast is required—simply clamping a Foley to accumulate IV contrast is inadequate and misses injuries 2
• Films at maximal fill and after drainage are mandatory 2
• Intraperitoneal bladder rupture presents with low-density free fluid (urinary ascites) on imaging 2

If bladder rupture is confirmed:

• Intraperitoneal rupture requires immediate surgical repair—catheter drainage alone is insufficient and risks peritonitis and sepsis 2
• Extraperitoneal rupture can be managed with catheter drainage for 2-3 weeks 2

Standard Hematuria Evaluation (If Bladder Intact)

Confirm True Microscopic Hematuria

• RBC 3-10/HPF meets the diagnostic threshold (≥3 RBCs/HPF) for microscopic hematuria requiring evaluation 2, 3
• This level is not normal—contrary to older literature suggesting up to 8 RBCs/HPF might be acceptable, current AUA guidelines define ≥3 as abnormal 2, 4

Rule Out Benign Causes First

Obtain urine culture before proceeding with invasive testing:

• If UTI is present, treat with appropriate antibiotics and repeat urinalysis 6 weeks after treatment completion 5
• Persistent hematuria after documented UTI resolution requires full urologic workup 2, 5
• Never attribute persistent hematuria to UTI without confirming resolution 5

Assess for Glomerular vs. Non-Glomerular Source

Examine urinary sediment for:

• Dysmorphic RBCs (>80% suggests glomerular disease) 3, 6
• Red blood cell casts (pathognomonic for glomerular disease) 3, 6
• Significant proteinuria (>500 mg/24 hours suggests renal parenchymal disease) 3, 6

If glomerular features present:

• Obtain serum creatinine, BUN, complete metabolic panel 3
• Check complement levels (C3, C4), ANA, ANCA if vasculitis suspected 3
• Refer to nephrology for persistent proteinuria, red cell casts, elevated creatinine, or hypertension with hematuria 3, 5

Complete Urologic Evaluation for Non-Glomerular Hematuria

Risk Stratification

This patient requires full urologic evaluation based on:

• Persistent symptoms (lower abdominal pain) with hematuria 2, 3
• Pain with hematuria suggests urolithiasis, tumor, or structural abnormality 2, 3

Imaging of Upper Urinary Tract

Multiphasic CT urography is the preferred modality:

• Includes unenhanced, nephrographic, and excretory phases to evaluate kidneys, collecting systems, ureters, and bladder 3, 4
• Superior sensitivity for detecting renal cell carcinoma, transitional cell carcinoma, and urolithiasis 2, 4
• If CT contraindicated (renal insufficiency, contrast allergy), use MR urography or renal ultrasound with retrograde pyelography 3

Lower Urinary Tract Evaluation

Cystoscopy is mandatory for complete evaluation:

• Flexible cystoscopy preferred over rigid (less pain, equivalent diagnostic accuracy) 3, 5
• Visualizes bladder mucosa, urethra, and ureteral orifices to exclude transitional cell carcinoma 3, 4
• Bladder cancer accounts for 30-40% of gross hematuria and 2.6-4% of microscopic hematuria cases 3

Follow-Up Protocol

If initial workup is negative but hematuria persists:

• Repeat urinalysis at 6,12,24, and 36 months with blood pressure monitoring 2, 5
• Consider repeat evaluation within 3-5 years for persistent or recurrent hematuria 2, 5

Immediate re-evaluation warranted if:

• Gross hematuria develops 2, 5
• Significant increase in degree of microscopic hematuria 2
• New urologic symptoms appear 2, 5
• Development of hypertension, proteinuria, or evidence of glomerular bleeding 2, 3

Critical Pitfalls to Avoid

• Never ignore the low BUN/creatinine ratio—this is not a benign finding and suggests urinary tract disruption until proven otherwise 1
• Never attribute hematuria to anticoagulation or antiplatelet therapy without complete evaluation—these medications unmask underlying pathology but don't cause hematuria 3, 5
• Never delay evaluation for persistent pain with hematuria—this combination has high yield for detecting significant pathology 2, 3
• Never accept UTI as the sole explanation without documenting resolution of hematuria 6 weeks post-treatment 5