How should I manage a patient with a kidney stone, including acute pain control, hydration, medical expulsive therapy, criteria for urologic referral, and preventive measures?

Kidney Stone Management

Acute Pain Control

NSAIDs are the first-line treatment for acute kidney stone pain and should be administered immediately—specifically intramuscular diclofenac 75 mg, which provides pain relief within 30 minutes. 1, 2

• NSAIDs (diclofenac, ibuprofen, metamizole) are superior to opioids because they reduce ureteral smooth muscle tone and spasm, have fewer side effects, and carry no risk of dependence 1, 2
• Use the lowest effective dose to minimize cardiovascular and gastrointestinal risks 1
• Be cautious in patients with low glomerular filtration rate as NSAIDs may impact renal function 1

Reserve opioids (hydromorphine, pentazocine, or tramadol) strictly as second-choice analgesics when NSAIDs are contraindicated or ineffective. 1, 2

• Avoid pethidine specifically due to high rates of vomiting and need for additional analgesia 1, 2
• Failure to respond to analgesia within one hour requires immediate hospital admission 2

Emergency Situations Requiring Urgent Intervention

If sepsis and/or anuria are present with an obstructed kidney, perform urgent decompression via percutaneous nephrostomy or ureteral stenting immediately—this is a urologic emergency. 1, 2

• Collect urine for antibiogram testing before and after decompression 1
• Administer antibiotics immediately and re-evaluate the regimen following antibiogram findings 1
• Delay definitive stone treatment until sepsis resolves 1
• Intensive care may become necessary 1
• Shock, fever with obstruction, or abrupt recurrence of severe pain after initial relief all require immediate hospital admission 2

Initial Diagnostic Workup

Obtain renal ultrasonography as the first-line imaging modality to quantify stone burden and guide treatment decisions. 3, 2, 4

• Follow with KUB or low-dose non-contrast CT if ultrasound does not provide sufficient information 1
• Ultrasound is preferred in pregnant patients 4

Perform urinalysis with both dipstick and microscopic evaluation to assess for infection, hematuria, urine pH, and identify crystals pathognomonic of stone type. 3, 2

• Obtain urine culture if urinalysis suggests infection or patient has history of recurrent UTIs 3, 2

Order serum chemistries including electrolytes, calcium, creatinine, and uric acid to identify underlying metabolic conditions. 3, 2

Obtain detailed medical and dietary history to identify conditions, habits, or medications that predispose to stone disease. 3

Conservative Management vs. Intervention Algorithm

Conservative management is appropriate for uncomplicated ureteral stones up to 10 mm (AUA guideline) or up to 6 mm (EAU guideline). 3, 2

• Maximum duration of conservative treatment is 4-6 weeks from initial presentation 3, 2
• If stone fails to pass spontaneously within this timeframe, intervention is required 3

Medical Expulsive Therapy (MET)

Prescribe alpha-blockers (tamsulosin) for medical expulsive therapy, particularly for stones >5 mm in the distal ureter—this provides the greatest benefit. 1, 3, 2

• MET is considered first-line therapy for uncomplicated distal ureteral stones ≤10 mm 4
• This is an off-label class effect of alpha-blockers 1

Hydration and Supportive Care

Instruct patients to increase fluid intake to achieve urine output of at least 2.5 liters daily to promote stone passage. 2, 5, 6

• For cystine stones specifically, target at least 4 liters per day to decrease urinary cystine concentration below 250 mg/L 5
• Coffee, tea, wine, and orange juice are associated with lower stone risk, while sugar-sweetened beverages should be avoided 2

Instruct patients to void urine into a container or through a tea strainer to catch any passed stone for analysis. 2

• Stone analysis should be performed for all first-time stone-formers to guide prevention strategies 2

Stone Type-Specific Medical Management

Calcium Stones

For calcium stones with hypercalciuria, offer thiazide diuretics (hydrochlorothiazide 25 mg twice daily or 50 mg once daily). 3, 2, 5

• Advise dietary sodium restriction to maximize the hypocalciuric effect 5

For calcium stones with hypocitraturia, offer potassium citrate therapy to increase urinary pH and inhibit stone formation. 3, 2, 5

• Potassium citrate is a potent inhibitor of calcium phosphate crystallization 3
• Prefer potassium citrate over sodium citrate as the sodium load may increase urine calcium excretion 3, 5

Uric Acid Stones

For uric acid stones, prescribe potassium citrate as first-line therapy to raise urinary pH to approximately 6.0, enhancing uric acid solubility. 3, 5

• Oral chemolysis with alkalinization using citrate or sodium bicarbonate (target pH 7.0-7.2) can dissolve stones with 80.5% success rate 1, 2
• Patients should monitor their urine pH and adjust medication accordingly 1
• Do not prescribe allopurinol as first-line therapy without addressing urinary pH 3, 5

Cystine Stones

For cystine stones, first-line therapy includes increased fluid intake (≥4 L/day), restriction of sodium and protein intake, and urinary alkalinization with potassium citrate to raise pH to approximately 7.0. 3, 5

Offer cystine-binding thiol drugs such as tiopronin to patients unresponsive to dietary modifications and urinary alkalinization. 5

• Tiopronin is preferred over d-penicillamine due to better efficacy and fewer adverse events 5

Brushite Stones

For brushite stone formers with hypocitraturia or elevated urine pH, prescribe potassium citrate as first-line pharmacological therapy. 3

Offer thiazide diuretics to brushite stone formers with hypercalciuria, as they lower urinary calcium excretion and may increase the safety and efficacy of citrate therapy. 3

• The combination of potassium citrate and thiazide diuretics can be used for patients with persistent stone formation 3

Criteria for Urologic Referral

Refer to urology for intervention if:

• Stone fails to pass after 4-6 weeks of conservative management 3, 2
• Sepsis and/or anuria with obstruction (urgent referral) 1, 2
• Shock or fever with obstruction (urgent referral) 2
• Abrupt recurrence of severe pain after initial relief 2
• Bleeding disorder or antithrombotic therapy requiring coordination with internist before stone management 1

Before stone treatment, obtain urine microscopy and culture results to exclude or treat UTI before stone removal. 1

Offer perioperative antibiotic prophylaxis to all patients undergoing endourological treatment—a single dose before ureteroscopy is sufficient. 1

• For percutaneous nephrolithotomy in high-risk patients, an extended course of preoperative antibiotic prophylaxis significantly reduces postoperative sepsis and fever 1
• Tailor antibiotic choice to institutional or regional antimicrobial susceptibility patterns 1

Metabolic Evaluation and Follow-Up

Obtain a single 24-hour urine specimen for stone risk factors within six months of initiating treatment to assess response to dietary and/or medical therapy. 3, 2, 5

After initial follow-up, obtain a single 24-hour urine specimen annually or with greater frequency depending on stone activity. 3, 5

Perform periodic blood testing to assess for adverse effects in patients on pharmacological therapy:

• Monitor for hypokalemia with thiazides 3, 5
• Monitor for hyperkalemia with potassium citrate 3, 5

Obtain repeat stone analysis when available, especially in patients not responding to treatment. 3, 5

Telephone follow-up one hour after initial assessment to verify pain control. 2

Obtain imaging studies within 7 days if stone has not passed to reassess stone burden. 2

Preventive Measures

Dietary Modifications

Ensure sufficient dietary calcium at 1000-1200 mg/day—do not restrict dietary calcium as this may paradoxically increase stone risk by increasing intestinal oxalate absorption. 2, 6

• Do not use supplemental calcium as it may be associated with increased risk of stone formation 3

Limit sodium intake to 2-3 g/day (or 3-5 g/day of sodium chloride). 6

Limit oxalate-rich foods in patients with calcium stones. 6

Avoid vitamin C and vitamin D supplements. 6

Limit animal proteins to 0.8-1.0 g/kg body weight/day but increase plant proteins in patients with calcium and uric acid stones and those with hyperuricosuria. 6

Increase proportion of citrus fruits in the diet. 6

Lifestyle Modifications

Maintain normal body mass index as obesity increases stone risk. 6, 4

Provide fluid compensation for working in high-temperature environments. 6

Avoid cigarette smoking. 6

Common Pitfalls to Avoid

• Do not use opioids as first-line therapy—NSAIDs are superior and avoid dependence risks 2
• Do not delay admission for patients with fever and obstruction—this represents a urologic emergency requiring immediate drainage 2
• Do not prescribe oral or rectal analgesics as primary therapy in acute settings—absorption is unreliable; intramuscular route is preferred 2
• Do not restrict dietary calcium—this may paradoxically increase stone risk 2, 6
• Do not ignore dysuria component—it may indicate concurrent UTI requiring antibiotic therapy before any stone intervention 2
• Do not neglect underlying metabolic abnormalities that contribute to stone formation 3
• Do not prescribe allopurinol as first-line therapy for uric acid stones without addressing urinary pH 3, 5
• Do not fail to monitor for medication side effects such as hypokalemia with thiazides or hyperkalemia with potassium citrate 3, 5