What is the approach to managing urolithiasis?

Approach to Urolithiasis Management

Acute Presentation and Initial Diagnostic Workup

For acute renal colic, immediately administer NSAIDs (diclofenac, ibuprofen, or metamizole) as first-line analgesia, reserving opioids only when NSAIDs are contraindicated or insufficient. 1, 2, 3

Diagnostic Imaging Strategy

• Ultrasound is the primary diagnostic tool and should not delay emergency care, though sensitivity is only 45% for ureteral stones 1
• Non-contrast CT is the gold standard after ultrasound for acute flank pain, providing 93.1% sensitivity and 96.6% specificity while assessing stone location, burden, density, and anatomy 1, 2
• Low-dose CT protocols should be utilized to minimize radiation exposure while maintaining diagnostic accuracy 1
• KUB radiography helps differentiate radioopaque from radiolucent stones and aids in follow-up monitoring 1

Essential Laboratory Evaluation

• Obtain urinalysis/urine culture, serum creatinine, uric acid, ionized calcium, sodium, potassium, blood cell count, and CRP for all emergency presentations 1
• Stone analysis must be performed for all first-time stone formers to guide targeted prevention strategies 1, 2

Emergency Interventions

If sepsis and/or anuria with obstruction is present, perform urgent decompression via percutaneous nephrostomy or ureteral stenting before any definitive stone treatment. 1, 2, 3 Collect urine for culture before and after decompression, initiate immediate antibiotics, and re-evaluate based on antibiogram results 1

---

Conservative Management and Medical Expulsive Therapy

Pain Control Protocol

• NSAIDs reduce additional analgesia requirements compared to opioids and should be dosed at the lowest effective amount to minimize cardiovascular/gastrointestinal risks 1, 2, 3
• Exercise caution with NSAIDs in patients with low glomerular filtration rate as they may impact renal function 1, 3
• If opioids are required, use hydromorphone, pentazocine, or tramadol rather than pethidine, which has higher vomiting rates 1, 3

Medical Expulsive Therapy (MET)

For ureteral stones >5mm in the distal ureter, alpha-blockers provide the greatest benefit with a 29% increase in stone passage rates. 1, 2, 3

• Patients must have well-controlled pain, no sepsis, and adequate renal function to attempt conservative management 2, 3
• Counsel patients that alpha-blockers are used "off-label" for this indication 2, 3
• Most stones that pass spontaneously do so within approximately 17 days (range 6-29 days) 4
• If observation with MET fails after 4-6 weeks, offer definitive stone treatment 4

---

Surgical Intervention

Indications for Immediate Intervention

Proceed directly to stone removal if:

• Uncontrolled pain despite adequate analgesia 4
• Signs of infection or sepsis 4
• Development of obstruction or significant hydronephrosis 4

Treatment Selection by Stone Characteristics

For ureteral stones requiring removal:

• Both SWL and URS are acceptable first-line treatments, though URS yields significantly greater stone-free rates (approximately 95% for stones <10mm) 1, 2, 4
• The electrohydraulic lithotripter should not be used for ureteral stones 1
• For patients with bleeding disorders or on anticoagulation, URS should be considered first-line 4

For renal stones:

• Stones <10mm: URS or SWL as first-line options 1
• Stones 10-20mm: URS or SWL 1
• Stones >20mm: PCNL as first-line therapy 1, 2
• Non-contrast CT is mandatory prior to PCNL to determine optimal surgical approach 1, 2

Procedural Considerations

• Administer antimicrobial prophylaxis based on prior culture results and local antibiogram patterns 4
• Use a safety guidewire for most endoscopic procedures to facilitate rapid re-access 4
• If purulent urine is encountered, abort the procedure immediately, establish drainage, and continue antibiotics 4

---

Stone-Specific Medical Prevention

Calcium Stones (Most Common - >80% of Cases)

Maintain dietary calcium intake of 1,000-1,200 mg daily - restriction paradoxically increases stone risk 1, 2

For hypercalciuria:

• Thiazide diuretics are strongly recommended 1, 2
• Acidify urine with L-Methionine if urinary pH is high 1

For hypocitraturia:

• Potassium citrate is FDA-approved and indicated for hypocitraturic calcium oxalate nephrolithiasis 5
• Initiate at 30 mEq/day for mild-moderate hypocitraturia (>150 mg/day) or 60 mEq/day for severe hypocitraturia (<150 mg/day) 5
• Target urinary citrate >320 mg/day (ideally 640 mg/day) and urinary pH 6.0-7.0 5

For hyperuricosuria:

• Allopurinol is recommended by multiple guidelines 1, 2
• Febuxostat is a second-line option, though the FDA issued a safety alert regarding increased cardiac death risk compared to allopurinol 1, 2

Uric Acid Stones

Oral chemolysis with urinary alkalinization is strongly recommended as first-line therapy. 1

• Potassium citrate or sodium bicarbonate to achieve urine pH 7.0-7.2 (or 6.2-6.8 per some guidelines) can dissolve stones 1, 2, 5
• Patients should monitor urine pH regularly 1
• There is controversy regarding allopurinol: AUA recommends against routine use as first-line, while EAU supports it for hyperuricosuric uric acid stone formers 1

Cystine Stones

Increase fluid intake to achieve urine output of at least 3L daily. 1, 2

• Urinary alkalinization to achieve pH 7.0-7.5 is universally recommended 1, 2
• If refractory to alkalinization, initiate thiol-binding agents (tiopronin or D-penicillamine) 1, 6

---

Universal Prevention Measures

All stone formers should increase fluid intake to achieve urine volume of at least 2.5L daily - this is the single most important dietary intervention 2, 6, 7, 8

• Limit salt intake by avoiding high-salt foods and added table salt 5
• Restrict animal protein and sodium ingestion 6

---

Monitoring and Follow-Up

Obtain 24-hour urine collections within 8-12 weeks (per EAU/UAA) or 6 months (per AUA/CUA) after initiating therapy to assess response. 1, 2

• Monitor serum electrolytes (sodium, potassium, chloride, CO2), creatinine, and complete blood counts every 4 months, more frequently in patients with cardiac disease, renal disease, or acidosis 5
• Perform periodic ECGs when using potassium citrate 5
• Discontinue potassium citrate if hyperkalemia, significant creatinine rise, or significant fall in hematocrit/hemoglobin occurs 5
• Periodic imaging to assess for stone growth or new formation, though specific timing is not standardized 1, 2

Critical Pitfall

Approximately 50% of recurrent stone formers experience only one recurrence, while 10% have highly recurrent disease requiring aggressive prevention 2 - tailor intensity of metabolic workup and prevention based on recurrence pattern rather than treating all patients uniformly.