What is the appropriate workup and treatment for a patient with suspected kidney stones?

Diagnostic Workup and Treatment for Kidney Stones

The appropriate workup for suspected kidney stones should include ultrasound as the primary diagnostic tool, followed by non-contrast CT if needed, along with basic blood and urine tests to identify underlying metabolic abnormalities and guide treatment decisions. 1

Initial Diagnostic Evaluation

Imaging Studies

• Ultrasound is the recommended first-line imaging modality with 45% sensitivity and 94% specificity for ureteral stones (88% for renal stones) 1
• Non-contrast CT scan is the standard second-line modality for acute flank pain after ultrasound, providing detailed information about stone location, burden, density, and anatomy 1
• Low-dose CT maintains high diagnostic accuracy (93.1% sensitivity, 96.6% specificity) while reducing radiation exposure 1
• KUB (kidney-ureter-bladder) radiography helps differentiate between radiopaque and radiolucent stones and is useful for follow-up 1

Laboratory Assessment

• Basic screening evaluation should include serum electrolytes, calcium, creatinine, and uric acid to identify underlying medical conditions associated with stone disease 1
• Urinalysis should include both dipstick and microscopic evaluation to assess urine pH, indicators of infection, and identify crystals that may indicate stone type 1
• Urine culture should be obtained if urinalysis suggests urinary tract infection or in patients with recurrent UTIs 1
• If primary hyperparathyroidism is suspected (high or high-normal serum calcium), obtain serum intact parathyroid hormone level 1

Advanced Metabolic Evaluation

Indications for Comprehensive Metabolic Testing

• High-risk first-time stone formers (multiple or bilateral stones, nephrocalcinosis) 1
• Recurrent stone formers 1
• Patients with stones composed of uric acid, cystine, or struvite (indicating specific metabolic or genetic abnormalities) 1

Components of Metabolic Testing

• One or two 24-hour urine collections analyzed for:
  • Total volume
  • pH
  • Calcium
  • Oxalate
  • Uric acid
  • Citrate
  • Sodium
  • Potassium
  • Creatinine 1
• Stone analysis should be performed at least once when a stone is available 1
• Review available imaging to quantify stone burden and identify anatomical abnormalities 1

Treatment Approach

Acute Management

• NSAIDs (diclofenac, ibuprofen, metamizole) are first-line treatment for renal colic 1
• Opioids are second-choice analgesics if NSAIDs are contraindicated or insufficient 1
• In cases of sepsis and/or anuria with obstructed kidney, urgent decompression via percutaneous nephrostomy or ureteral stenting is strongly recommended 1
• Medical expulsive therapy (alpha-blockers) is effective for ureteral stones, particularly those >5mm in the distal ureter 1

Stone Removal Options

• Endoscopic procedures (ureteroscopy, percutaneous nephrolithotomy) are preferred for most patients requiring stone removal 1
• Open/laparoscopic/robotic surgery should not be offered as first-line therapy except in rare cases with anatomic abnormalities, large/complex stones, or those requiring reconstruction 1
• Stone material should be sent for analysis to guide prevention strategies 1
• Antimicrobial prophylaxis should be administered prior to stone intervention based on prior urine culture results and local antibiogram 1

Prevention Strategies

• Dietary modifications based on stone type and metabolic abnormalities 1
• Increased fluid intake to achieve urine output >2.5 L/day 1
• Pharmacologic therapy targeted to specific metabolic abnormalities identified in 24-hour urine collections 1
• Regular follow-up with repeat metabolic testing to assess response to interventions 1

Special Considerations

• Pregnant women: Ultrasound is first-line imaging, followed by MRI if needed, with low-dose CT as last resort 1
• Children: Ultrasound is first-line imaging, followed by KUB or low-dose CT if additional information is required 1
• Patients with infection stones or suspected infection: Complete stone removal is essential to prevent recurrent UTIs and renal damage 1
• Patients with reduced renal function: Careful monitoring is required as some stone types (cystinuria, primary hyperoxaluria, struvite stones) present greater risk for renal failure 2

Common Pitfalls to Avoid

• Delaying imaging in patients with suspected obstruction, fever, or solitary kidney 1
• Failing to obtain stone analysis when available 1
• Inadequate metabolic evaluation in high-risk or recurrent stone formers 1
• Neglecting to assess for systemic conditions associated with stone disease (obesity, hypertension, diabetes) 1
• Incomplete stone removal when infection stones are present 1