In urgent care, how should I evaluate and manage a patient who suspects a kidney stone and presents with only trace hematuria and no other findings?

Immediate Management of Suspected Kidney Stone with Trace Hematuria in Urgent Care

In an urgent care setting, a patient with suspected kidney stone and only trace hematuria requires pain control, confirmation of true hematuria with microscopic urinalysis, and risk-stratified imaging—but the absence of hematuria does NOT exclude urolithiasis.

Initial Assessment and Pain Management

• Provide immediate analgesia with NSAIDs (if not contraindicated) or opioids for severe pain, as renal colic is typically severe and radiates to the groin 1.
• Administer IV fluids if the patient is dehydrated or unable to tolerate oral intake, though high fluid intake is a mainstay of stone management 1.
• Assess for signs of infection including fever (>37.8°C), rigors, or systemic symptoms, as infected hydronephrosis is a urologic emergency requiring immediate drainage 2, 3, 4.

Confirm True Hematuria

• Order microscopic urinalysis immediately to confirm ≥3 red blood cells per high-power field (RBC/HPF), as dipstick testing alone has only 65-99% specificity and "trace" blood may represent a false positive 5, 6.
• Recognize that absence of hematuria does NOT exclude stones: microhematuria has only 77% sensitivity for urolithiasis overall, and 23% of patients with confirmed stones have no hematuria 7.
• The sensitivity is even lower (55%) for renal stones compared to ureteral stones (85%), so negative microscopy does not rule out nephrolithiasis 7.

Risk Stratification for Imaging

High-Risk Features Requiring Immediate CT (Non-Contrast)

• Fever, rigors, or signs of sepsis with suspected obstruction = infected hydronephrosis requiring emergent urologic consultation and drainage (percutaneous nephrostomy or retrograde stent) 2, 3, 4.
• High-grade obstruction suggested by severe unrelenting pain despite adequate analgesia 1.
• Solitary kidney, transplant kidney, or baseline renal insufficiency 5.
• Inability to control pain with oral analgesics may require hospitalization and imaging 1.

Standard Imaging Approach

• Non-contrast CT (NCCT) is the gold standard for diagnosing urolithiasis in the emergency/urgent care setting, with superior sensitivity and specificity compared to ultrasound or IVP 5, 7.
• Ultrasound has limited sensitivity (24-57% for stone detection overall, up to 61% for ureteral stones), though it is 100% sensitive for hydronephrosis if present for >2 hours 5.
• Low-dose CT protocols can minimize radiation while maintaining diagnostic accuracy 5.

Laboratory Evaluation

• Obtain urinalysis with microscopy to confirm hematuria and assess for pyuria, crystals, or casts 5.
• Urine culture if infection suspected (pyuria, fever, or systemic symptoms), preferably before antibiotics 5, 2.
• Serum creatinine and BUN to assess renal function, especially if obstruction or bilateral stones suspected 5.
• Strain urine to recover stone for analysis, as stone composition guides prevention strategies 1.

Disposition and Follow-Up

Discharge Criteria (if no high-risk features)

• Pain controlled with oral analgesics 1.
• No signs of infection or high-grade obstruction 1, 4.
• Able to tolerate oral fluids 1.
• Provide oral analgesia, antiemetics, and instructions to strain urine 1.
• Arrange urology follow-up within 1-2 weeks for stones that may not pass spontaneously (>5mm, proximal location) 5.

Hospitalization/Urgent Urology Referral Required

• Infected hydronephrosis (fever + obstruction) = immediate drainage with percutaneous nephrostomy or retrograde stent 2, 3, 4.
• Uncontrolled pain despite parenteral analgesia 1.
• High-grade obstruction or solitary kidney 1.
• Acute kidney injury or baseline renal insufficiency 5.

Critical Pitfalls to Avoid

• Never dismiss suspected stone disease based on absent hematuria alone—23% of confirmed stones have no microscopic hematuria 7.
• Do not delay imaging in patients with fever and suspected obstruction, as infected hydronephrosis requires emergent decompression within hours 2, 3, 4.
• Do not rely on ultrasound alone for stone diagnosis in the acute setting, as it misses the majority of ureteral stones and small renal stones 5.
• Approximately 90% of stones <5mm pass spontaneously, but larger stones or those causing high-grade obstruction require intervention 1.