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Urolithiasis

Basics

Stone formation within the urinary tract: Urinary crystals bind to form a nidus, which grows into a calculus (stone). Symptoms range from asymptomatic to obstructive, with febrile morbidity if infection is involved.

Epidemiology

  • Bladder stones (vesical calculosis) common in malnourished populations (Middle East, Asia)

  • Increasing incidence in industrialized nations

  • Increased risk in patients with IBD, gastric bypass

  • Incidence: 100–200/100,000/year (industrialized countries)

  • Peak age: 40–60 years; M:F ratio ~3:1

  • Prevalence: 10–15% in US; lifetime risk >14% (men), >6% (women)

Etiology & Pathophysiology

  • Supersaturation + dehydration → stone formation

  • Urinary stasis (e.g., horseshoe kidney, neurogenic bladder)

  • Promoters/Inhibitors:

    • Organic: Tamm-Horsfall protein, uropontin, etc.

    • Inorganic: citrate, pyrophosphate

  • Stone types:

    • Calcium oxalate/phosphate (80%)

    • Uric acid (10–15%)

    • Struvite (5–10%)

    • Cystine (<1%)

Contributing Conditions

  • Hypercalciuria (absorptive, renal leak, resorptive)

  • Hyperparathyroidism, sarcoidosis, malignancy, immobilization

  • Hyperoxaluria (enteric, primary, dietary)

  • Hyperuricosuria (purine-rich diet, gout, chemo, etc.)

  • Hypocitraturia (acidosis, RTA, thiazides)

Genetics

  • Up to 20% have family history

  • Inherited forms: cystinuria, hyperoxaluria, Lesch-Nyhan, RTA

Risk Factors

  • Race: White > Asian > Black

  • Male sex, family history

  • High protein/salt/oxalate diets

  • Hot, dry environments, sedentary work, summer months

  • Obesity, GI surgery, anatomical anomalies

  • Some medications and possible microbiome involvement

Prevention

  • Hydration (≥2–3 L/day)

  • Limit salt, meat, and oxalate-rich foods

  • Children: ultrasound before CT; MET for ≤10 mm stones

  • Pregnancy: conservative management unless symptomatic

Diagnosis

History

  • Renal colic, flank/groin pain, hematuria (95%)

  • N/V, fever, dysuria, urgency

Physical Exam

  • CV angle tenderness, iliac fossa pain

Differential

  • Appendicitis, AAA rupture, pyelonephritis, ectopic pregnancy, MI, etc.

Diagnostics

  • Urinalysis (pH, RBCs, nitrates)

  • Bloodwork: creatinine, calcium, urate, CBC

  • Stone analysis if passed

  • Non-contrast CT: gold standard

  • Ultrasound: especially in pregnancy/children

  • X-ray KUB for radiopaque stones

Treatment

Conservative Management

  • Stones <5 mm: spontaneous passage

  • Stones 5–10 mm: may require medical expulsive therapy (MET)

  • Stones >10 mm: usually surgical intervention

  • Recurrence: 30–50% within 5–10 years

Medications

  • α-blockers (e.g., tamsulosin) for MET

  • NSAIDs for pain (e.g., ketorolac)

  • Antiemetics as needed

Referrals

  • UTI, sepsis, renal failure, large stones, pregnancy, children

Additional Therapies

  • Uric acid stones: alkalinize urine (K-citrate), allopurinol

  • Cystine stones: alkalinize urine, chelating agents

  • Modify risk meds: e.g., indinavir, triamterene, acetazolamide

Surgical Options

  • Emergency: stent or nephrostomy

  • Elective: ESWL, ureteroscopy, PCNL

  • Open surgery is rare

Inpatient Considerations

  • Analgesia: NSAIDs + opioids

  • Antiemetics

Ongoing Care

  • Follow-up imaging until stone passage confirmed

  • Stone analysis + 24-hour urine panel if recurrent

  • PTH if hypercalcemia

Dietary Advice

  • Increase fluids (clear urine)

  • Reduce carbonated drinks, oxalate, salt, and protein

  • Avoid low calcium diets

  • Increase phytate-rich foods

  • Limit vitamin C

Prognosis

  • Passage rate:

    • <5 mm: 90% pass

    • 8 mm: 10% pass

  • Recurrence: 50% in 10 years

Patient Education

  • Explain risk factors, dietary links, and need for hydration

Clinical Pearls

  • Tamsulosin helps passage of moderate stones

  • Avoid calcium restriction in calcium stone formers

  • High-oxalate foods should be minimized