Urolithiasis/Nephrolithiasis

General Overview

• Symptoms
  • Renal colic, hematuria, abdominal/flank pain waves or paroxysms, nausea, urinary symmptoms
    • Struvite with UTI, flank pain, urine pH<7
• Stones
  • Calcium (oxalate>phosphate) stones (80%), uric acid, struvite (magnesium ammonium phosphate), cystine
• Risk
  • History of prior nephrolithiasis (50% recurrence at 10y)
  • Family history (2xRR)
  • Hypertension (2xRR)
  • Enhanced enteric oxalate absorption (gastric bypass, bariatric surgery, short bowel syndrome)
  • Proteus/Klebsiella UTI for Struvite
• Complications
  • Renal obstruction/damage (eg. Staghorn calculi)
  • Do not miss pyelonephritis, diverticular abscess

Red Flags

• Concurrent UTI (risk of pyonephrosis, bacteremia)
• Single kidney
• Bilateral obstruction
• Premorbid renal failure or anuria

Diagnosis

• Non-contrast CT scan (88% sensitivity)
  • Ureteral dilatation or stranding without a stone likely recent passage of stone
• Ultrasound (54% sensitivity)
  • First-line in pregnancy
• Other: KUB (abdominal plain film)

Investigations

• UA + Urine culture
• Serum electrolytes (Na, K, Cl, HCO3, Ca, Creat)
• Stone analysis

Additional investigations for risk (<18yo, multiple or recurrent stones, non-calcium stones - uric acid or cystine, complication - AKI, sepsis, hospitalization)

• Albumin, uric acid, bicarbonate
• PTH if serum calcium is high normal or high
• Vitamin D if serum calcium low normal or elevated PTH
• 24h urine collection x2
  • Volume, creatinine, Ca, Na, K, Oxalate, Citrate, uric acid, magnesium
  • Cystine if suspect cystine stone (or if stone analysis cystine)
• Spot urine: pH, UA, Specific gravity

Treatment

• Pain control: NSAID + Opioid
  • Ketorolac 15mg IV or indomethacin 100mg PR + morphine 5mg IV
• Hydration (Target 2.5L daily urine output)
• Consider Tamsulosin 0.4mg PO daily (or nifedipine)
  • Recent studies do not show a significant benefit
• Urology consultation
  • Inpatient if urosepsis, acute kidney injury, anuria, N/V (unable to tolerate oral)
  • Outpatient if >10mm (unlikely to pass)
• Strain urine to analyse stone
• Diet
  • High in fiber, fruits, vegetables
  • Calcium 1000-1200mg/day
    • Calcium stone - aim for sodium intake of 1500mg (<2300mg daily)
  • Avoid Vitamin C