Nephrolithiasis in Adults

Background

• Kidney stones (renal calculi) are crystalline mineral deposits that form in the kidney, and may occur in 1%-20% of people during their lifetime. The risk of recurrence depends on the disease or disorder causing stone formation, but may be up to 40%-50% in adults with idiopathic calcium stones.
• Hypercalciuria is the most common underlying metabolic precipitant. Other causes include hyperoxaluria, hyperuricosuria, hypocitraturia, cystinuria, low urinary volume, urinary tract infection, and medications.
• Calcium (oxalate or phosphate) is the most common constituent of stones, with other common constituents being struvite (associated with infection) and uric acid.
• Spontaneous passage rates are estimated to be 68% for stones < 5 mm and 47% for stones 5-10 mm, but spontaneous passage may take more than 1 week. Rates can vary based on factors such as age, gender, and prior history of stones.

Evaluation

• Patients are often asymptomatic until a stone causes partial, intermittent, or complete obstruction, resulting in acute and potentially debilitating renal colic.
• Perform immediate imaging in patients with fever or solitary kidney, or when the diagnosis of stone is in doubt (Strong recommendation).
  • Use noncontrast-enhanced computed tomography (CT) as a first-line imaging choice in non-pregnant adults (Strong recommendation). It has the best sensitivity and specificity, but carries a significant radiation exposure.
  • Low-dose CT is preferred for patients with body mass index (BMI) ≤ 30 kg/m² to limit risks of ionizing radiation while maintaining sensitivity and specificity at ≥ 90%, but is not recommended for patients with BMI > 30 kg/m² due to lower sensitivity and specificity.
  • Use ultrasound as an alternative in children, pregnant women, or persons with a history of radio-opaque stones.(Strong recommendation).
• For patients with acute symptomatic stone(s), perform:
  • blood tests including complete blood count, serum creatinine, uric acid, and calcium (ionized or total calcium plus albumin) (Strong recommendation).
  • urinalysis and urine culture or microscopy to rule out infection and assess stone composition (Strong recommendation).
  • imaging to assess stone location and quantify stone burden (Strong recommendation).
• For patients with asymptomatic stone(s) or prior stone history, consider:
  • blood tests including complete blood count, serum creatinine, uric acid, and calcium (ionized or total calcium plus albumin).
  • urinalysis and urine culture or microscopy to rule out infection and assess stone composition.
  • imaging to assess for stone location and quantify stone burden
• Obtain a stone composition analysis for the first stone that is able to be recovered (Strong recommendation).
• Consider obtaining 1 or 2 24-hour urine collections as part of a full metabolic evaluation for patients with or at risk for multiple stone episodes, including those with nephrocalcinosis.

Management

• Pain management with analgesics:
  • Offer a nonsteroidal anti-inflammatory drug (NSAID) (such as metamizole, diclofenac, indomethacin, or ibuprofen) or acetaminophen as drug of first choice for initial pain control (Strong recommendation) (metamizole not available in the United States) .
  • Consider hydromorphone, pentazocine, or tramadol as a second choice (Weak recommendation) (pentazocine only available as combination formulation with naloxone in the United States) .
  • Consider nonpharmacologic methods of pain control including local warming of abdomen and lower back and transcutaneous electrical nerve stimulation (TENS).
• Management of urinary tract infection:
  • Treat urinary tract infection, if present, prior to endourologic stone removal (Strong recommendation).
  • Perform urgent decompression (percutaneous drainage or ureteral stenting) in patients with evidence of infection and obstructing stone or any signs of sepsis with obstructing stones (Strong recommendation).
• Treat all uncomplicated cases of urolithiasis in pregnancy conservatively, unless there are clinical indications for intervention (Strong recommendation).
• For ureteral stones:
  • Consider active stone removal if there is low likelihood of spontaneous passage, persistent pain despite adequate pain medication, persistent obstruction, or renal insufficiency.
  • If there are no indications for active stone removal, initial observation with periodic evaluation recommended for patients with newly diagnosed ureteral stones(Strong recommendation) (generally < 6 mm, but no exact cutoff known).
  • Offer alpha blockers as medical expulsion therapy to adults with distal ureteral stones ≥ 5 but ≤ 10 mm (Strong recommendation).
  • If active stone removal is needed, the choice of procedure depends on stone composition, location, size, available equipment, and patient preference.
    • Use ureteroscopy for patient with mid- or distal ureteral stones who are not candidates for or failed medical expulsion therapy (Strong recommendation); consider ureterorenoscopy in patients with suspected cystine or uric acid ureteral stones (Weak recommendation), and for ureteral stones ≥ 10 mm.
    • Use shock wave lithotripsy (SWL) for patients with mid- or distal ureteral stones if treatment is indicated and patient declines ureterorenoscopy (Strong recommendation) or can be an option for ureteral stones < 10 mm. Homogeneous stones with high density (> 1,000 HU) on unenhanced CT are less likely to be disintegrated by SWL.
    • Use percutaneous antegrade removal as an alternative when SWL not indicated or has failed, and when upper urinary tract is not amenable to retrograde ureteroscopy (Strong recommendation).
• For renal stones:
  • Consider observation if there are no indications for active stone removal, or for asymptomatic, stable renal stones.
  • Indications for active stone removal include stone growth, stones in patients at high risk for stone formation, obstruction due to stones, infection, symptoms, large stone size, and patient preference.
  • If active stone removal is needed, the choice of procedure depends on stone composition, location, size, available equipment, and patient preference.
    • For symptomatic calyceal diverticular stones, preferentially use endoscopic therapy (ureterorenoscopy, percutaneous nephrolithotomy, laparoscopic surgery, robotic surgery) (Strong recommendation).
    • For symptomatic non-lower pole renal stone burden ≤ 20 mm, offer SWL or ureterorenoscopy; if > 20 mm, offer percutaneous nephrolithotomy as first-line therapy (Strong recommendation).
    • For symptomatic lower pole stone burden ≤ 10 mm, offer SWL or ureterorenoscopy. If > 10 mm, consider ureterorenoscopy or percutaneous nephrolithotomy.
• Consider follow-up within 6 months of starting treatment with single 24-hour urine specimen for stone risk factors to assess response to dietary and/or medical therapy, and then at least annually (Weak recommendation).
• To reduce recurrence risk:
  • Increase fluid intake spread throughout the day to achieve urine volume ≥ 2-2.5 L/day (Strong recommendation).
  • Consider criteria for high risk of recurrence to determine if secondary prevention is indicated.
  • Consider specific prevention strategies as guided by results of metabolic evaluation and stone composition analysis. For example:
    • For calcium oxalate stones:
      • Limit dietary sodium intake.
      • Dietary calcium restriction is not recommended. Counsel patients to consume dietary calcium 1,000 – 1,200 mg per day.
      • Increase fruits and vegetables and limit non-dairy animal protein.
      • Consider pharmacologic monotherapy with thiazide diuretic, citrate, or allopurinol to prevent recurrent nephrolithiasis in patients with active disease in whom increased fluid intake fails to reduce the formation of stones.
    • For uric acid stones:
      • Offer potassium citrate to raise urinary pH.
      • Do not routinely offer allopurinol as first-line therapy.
    • For struvite and infection stones, surgically remove stone material as completely as possible and prescribe antibiotics in patients with persistent bacteriuria (Strong recommendation).