What is the recommended workup for a patient with a history (hx) of kidney stones who is currently experiencing symptoms?

Workup for Patient with History of Kidney Stones Presenting with Symptoms

Start with ultrasound as your primary imaging modality, followed by non-contrast CT if ultrasound is inconclusive, and obtain urinalysis with dipstick and microscopy plus basic serum chemistry (electrolytes, calcium, creatinine, uric acid, CBC, and CRP if infection suspected). 1, 2

Immediate Assessment

Determine if this is an emergency requiring urgent intervention:

• Check for fever, signs of sepsis, or intractable pain requiring immediate referral 2
• Assess for solitary kidney, bilateral obstruction, or acute kidney injury 2
• If infection with obstruction is present, urgent decompression via percutaneous nephrostomy or ureteral stenting is mandatory 3

Imaging Strategy

Primary imaging approach:

• Ultrasound first (45% sensitivity, 94% specificity for ureteral stones; 88% specificity for renal stones) 1, 2
• Ultrasound is particularly useful for detecting hydronephrosis and complications, though it may miss findings within the first 2 hours before secondary signs of obstruction develop 1

If ultrasound is inconclusive or additional detail needed:

• Non-contrast CT abdomen/pelvis is the reference standard with 97% sensitivity 1
• Use low-dose CT protocol (93.1% sensitivity, 96.6% specificity) to minimize radiation exposure 1, 2
• For patients with known recent stone disease on imaging, non-contrast CT helps assess interval stone migration, passage, or complications like infection, perinephric abscess, or urinoma 1

Plain KUB radiography:

• Helps differentiate radiopaque from radiolucent stones (44-77% sensitivity) 1
• Useful for follow-up imaging 1, 2

Laboratory Evaluation

Immediate laboratory workup for all symptomatic patients:

• Urinalysis: Dipstick and microscopy to assess pH, hematuria, signs of infection, and crystal identification 1, 2
• Serum chemistry: Electrolytes, calcium, creatinine, uric acid 1, 2
• CBC and CRP if infection suspected 1
• Urine culture if urinalysis suggests infection or patient has history of recurrent UTIs 2

Stone analysis:

• Instruct patient to strain urine and collect any passed stones for analysis 2, 3
• Stone analysis should be performed for all first-time stone formers when material is available 1, 2

Pain Management

First-line treatment:

• NSAIDs (diclofenac, ibuprofen, or metamizole) are first-line for renal colic 1, 2
• NSAIDs reduce need for additional analgesia compared to opioids 1
• Use lowest effective dose due to cardiovascular and gastrointestinal risks 1

Second-line:

• Opioids when NSAIDs are contraindicated or insufficient 2, 3

Metabolic Evaluation Timing

Defer comprehensive metabolic testing during acute presentation, but plan for:

• High-risk first-time stone formers (multiple/bilateral stones, nephrocalcinosis) 3
• All recurrent stone formers (≥2 episodes) 1, 3
• Patients with bilateral disease or strong family history 1
• Stones composed of uric acid, cystine, or struvite 3

Comprehensive metabolic testing includes:

• One or two 24-hour urine collections analyzing volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 2, 3

Special Populations

Pregnant patients:

• Ultrasound as first-line imaging (strongly recommended) 1, 2
• MRI as second-line if needed 2, 3
• Low-dose CT only as last resort 1, 2

Pediatric patients:

• Ultrasound first-line, followed by KUB or low-dose CT if additional information required 1, 3

Common Pitfalls to Avoid

• Do not delay imaging in patients with suspected obstruction, fever, or solitary kidney 3
• Do not miss infection with obstruction, which constitutes a urologic emergency requiring immediate drainage 2
• Do not rely solely on ultrasound if clinical suspicion remains high despite negative findings, as sensitivity is only 45% for ureteral stones 1
• Do not order contrast-enhanced CT routinely for known stone disease with recurrent symptoms, as it rarely changes management (only 2-3% of cases) 1
• Do not forget to instruct patients to strain urine to capture stones for analysis 2