What is the recommended work-up and treatment for a patient with kidney stones?

Kidney Stone Work-Up and Management

Initial Screening Evaluation

All patients newly diagnosed with kidney or ureteral stones should undergo a screening evaluation consisting of detailed medical and dietary history, serum chemistries (electrolytes, calcium, creatinine, uric acid), and urinalysis with both dipstick and microscopic examination. 1

Medical History Components

• Query for medical conditions predisposing to stones: hyperparathyroidism, renal tubular acidosis, inflammatory bowel disease, obesity, hypertension, diabetes 1, 2
• Document all medications and supplements that may provoke stone formation 1
• Assess for personal or family history of kidney stones 2
• Obtain serum intact parathyroid hormone level if primary hyperparathyroidism is suspected 1

Dietary History Specifics

• Average daily fluid intake (amount and specific beverages consumed) 1
• Protein intake (types and amounts, particularly animal-derived purines) 1
• Daily calcium intake relative to recommended dietary allowance 1
• Sodium consumption 1
• High oxalate-containing foods 1
• Fruits and vegetables intake 1
• Over-the-counter supplements 1

Urinalysis Details

• Assess urine pH to help predict stone type 1, 3
• Identify crystals pathognomonic of specific stone types 1, 3
• Evaluate for indicators of infection 1, 3
• Obtain urine culture if urinalysis suggests UTI or patient has recurrent UTIs 1, 4

Diagnostic Imaging Strategy

Ultrasound is the recommended first-line imaging modality (45% sensitivity and 94% specificity for ureteral stones, 88% for renal stones), followed by non-contrast CT if needed. 3

• Non-contrast CT is the standard second-line modality for acute flank pain after ultrasound, providing detailed information about stone location, burden, density, and anatomy 3
• Low-dose CT maintains high diagnostic accuracy (93.1% sensitivity, 96.6% specificity) while reducing radiation exposure 3
• KUB radiography helps differentiate radiopaque from radiolucent stones and is useful for follow-up 3
• Pregnant women should undergo ultrasound first-line, followed by MRI if needed, with low-dose CT as last resort 3
• Children should undergo ultrasound first-line, followed by KUB or low-dose CT if additional information required 3

Comprehensive Metabolic Evaluation

High-risk first-time stone formers and all recurrent stone formers should undergo comprehensive metabolic testing with one or two 24-hour urine collections. 3, 4

Indications for Comprehensive Metabolic Testing

• Multiple or bilateral stones 3
• Nephrocalcinosis 3
• Recurrent stone formation 3, 4
• Stones composed of uric acid, cystine, or struvite 3

24-Hour Urine Analysis Parameters

• Total volume 3
• pH 3
• Calcium 3
• Oxalate 3
• Uric acid 3
• Citrate 3
• Sodium 3
• Potassium 3
• Creatinine 3

Acute Pain Management

NSAIDs (diclofenac, ibuprofen, metamizole) are first-line treatment for renal colic, with opioids reserved as second-choice analgesics only if NSAIDs are contraindicated or insufficient. 3, 4

• NSAIDs demonstrate superior efficacy, fewer side effects, and lower risk of dependence compared to opioids 4, 5

Treatment Decision Algorithm

Conservative Management

• Appropriate for uncomplicated ureteral stones up to 10 mm (AUA) or up to 6 mm (EAU) 4
• Medical expulsive therapy with alpha-blockers (tamsulosin) is recommended, particularly for stones >5mm in the distal ureter 3, 4
• Maximum duration of conservative treatment should be 4-6 weeks from initial presentation 4
• Approximately 90% of stones causing renal colic pass spontaneously 6

Urgent Intervention Required

• Sepsis and/or anuria with obstructed kidney requires urgent decompression via percutaneous nephrostomy or ureteral stenting 3
• High-grade obstruction with failure of oral analgesics to relieve pain 6
• Urinary tract infection in the setting of obstruction is a urologic emergency requiring immediate drainage 6

Elective Intervention Indications

• Stones that fail to pass after 4-6 weeks of conservative management 4
• Stone growth on serial imaging 5
• Persistent symptoms 5
• Urinary obstruction 5
• Recurrent infections 5
• Endoscopic procedures (ureteroscopy, percutaneous nephrolithotomy) are preferred for most patients requiring stone removal 3

Stone Analysis

Stone analysis should be obtained at least once when stone material is available to guide prevention strategies and treatment decisions. 4, 2

• Stone analysis should be performed during surgery, especially when only a few fragments are available 7
• Repeat stone analysis should be obtained in patients not responding to treatment 4

Medical Management Based on Stone Type

Calcium Stones

• Thiazide diuretics should be offered to patients with high or relatively high urine calcium and recurrent calcium stones 4
• Potassium citrate therapy should be offered to patients with recurrent calcium stones and low or relatively low urinary citrate 4
• Combination of potassium citrate and thiazide diuretics can be used for persistent stone formation 4

Uric Acid Stones

• Potassium citrate is first-line therapy to raise urinary pH to approximately 6.0 4
• Allopurinol should not be used as first-line therapy 4

Cystine Stones

• First-line therapy includes increased fluid intake, restriction of sodium and protein intake, and urinary alkalinization 4

Brushite Stones

• Potassium citrate is first-line for patients with hypocitraturia or elevated urine pH 4
• Thiazide diuretics should be offered to brushite stone formers with hypercalciuria 4

Prevention Strategies for All Patients

All patients should increase fluid intake to achieve urine output >2.5 L/day. 3, 4, 2

• Coffee, tea, wine, and orange juice are associated with lower stone risk 2
• Sugar-sweetened beverages should be avoided 2
• Maintain normal dietary calcium intake (1,000-1,200 mg/day) from food sources, not supplements 4, 2
• Limit sodium intake to 2,300 mg daily 4, 2
• For calcium oxalate stones, limit oxalate-rich foods while maintaining normal calcium consumption 2
• Avoid calcium supplements, which may increase stone risk unlike dietary calcium 4, 2
• Do not restrict dietary calcium, as this may increase intestinal oxalate absorption and stone risk 2, 6

Follow-Up Monitoring

A single 24-hour urine specimen should be obtained within six months of initiating treatment to assess response to dietary and/or medical therapy. 4

• After initial follow-up, obtain 24-hour urine specimen annually or more frequently depending on stone activity 4
• Periodic blood testing should be performed to assess for adverse effects in patients on pharmacological therapy 4
• Serial imaging should be used to monitor asymptomatic kidney stones 5

Critical Pitfalls to Avoid

• Delaying imaging in patients with suspected obstruction, fever, or solitary kidney 3
• Failing to obtain stone analysis when available 3
• Inadequate metabolic evaluation in high-risk or recurrent stone formers 3
• Neglecting to assess for systemic conditions associated with stone disease (obesity, hypertension, diabetes) 3
• Incomplete stone removal when infection stones are present 3
• Prescribing allopurinol as first-line therapy for uric acid stones instead of urinary alkalinization 4
• Using supplemental calcium rather than dietary calcium 4