Urology: Nephrolithiasis (Kidney Stones)

Nephrolithiasis (Kidney Stones)

Definitions

  • Urolithiasis: Stone in Any Part of the Urinary Tract
  • Nephrolithiasis: Kidney Stones or Renal Calculi
    • *Often Used to Broadly Refer to Any Stone in the Urinary Tract
  • Ureterolithiasis: Stone in the Ureter

Stone Types

  • Radiopaque Stones:
    • Calcium Oxalate (70-80% – Most Common Stone)
    • Calcium Phosphate (15%)
    • Struvite (Mg Ammonium Phosphate) (1%)
      • Staghorn Calculi Within Pelvis
      • From Proteus mirabilis Infection (Produce Urease)
  • Radiolucent Stones:
    • Uric Acid (8%)
    • Cysteine (1-2%)
      • From Congenital Disorders of Cysteine Reabsorption

Risk Factors

  • Older Age
  • Male Sex
  • White Ethnicity
  • Functional Disability
  • Prior Stones
    • Recurrence Risk: 10-30% at 3-5 Years, 50% at 10 Years
  • Specific Risk Factors for Calcium Oxalate Stones:
    • Low Urine Output
    • High Urine Calcium or Oxalate
    • High Urine pH
    • Low Urine Citrate
    • Primary Hyperparathyroidism
    • Diabetes
    • Increased GI Absorption of Oxalate in Colon – Due to IBD, Short Gut Syndrome or Bowel Resection)
    • Betel Quid Chewing (Practice in Southeast Asia)
  • Specific Risk Factors for Uric Acid Stones:
    • Gout
    • Obesity
    • Low Urine pH
    • Myeloproliferative Disorders

Presentation

  • Colicky Pain – Severe Episodes Lasting 20-60 Minutes
  • Hematuria
  • Nausea & Vomiting
  • Dysuria
  • Urinary Urgency

Complications

  • Urinary Obstruction & Hydronephrosis
  • Renal Injury/Failure
  • Urinary Tract Infection/Pyelonephritis

Diagnosis

  • Primary Diagnosis: CT (Without Contrast)
  • Other Options: MRI or IV Pyelography

Nephrolithiasis 1

Large Right Ureterolithiasis on CT 2

Staghorn Nephrolithiasis on Abdominal XR 3

Treatment

Medical Treatment

  • Primary Tx: Pain Control (NSAIDs Preferred)
  • Tamsulosin (Alpha Blocker) for Stones 5-10 mm in Diameter

Emergent Surgery

  • Indications:
    • Obstructing Stone & UTI/Sepsis
    • Bilateral Obstruction & AKI
    • Obstruction & AKI with a Solitary Functional Kidney
  • Urgent Decompression is Preferred Approach
    • Generally Wait to Remove Stone Until Infection is Cleared
    • Stone Manipulation in Setting of UTI Can Cause Severe Sepsis
  • Surgical Approach:
    • Ureteroscopy with Stent Placement
    • Percutaneous Nephrolithotomy with Percutaneous Nephrostomy Tube

Elective Surgery

  • Indications:
    • Severe Symptoms
    • Diameter > 10 mm
    • Medical Failure After 4-6 Weeks
    • Persistent Obstruction Due to Stones
    • Recurrent UTI Due to Stones
  • Surgical Options:
    • Ureteroscopy – Often the Preferred Approach
      • May Leave a Ureteral Stent After Stone Excision
    • Extra-Corporeal Shock Wave Lithotripsy (ESWL) – May Be Considered for Small-Medium Sized Stones in the Proximal-Mid Ureter
    • Percutaneous Nephrolithotomy – Generally Reserved as Second-Line for Large/Complex Stones
      • May Leave a Percutaneous Nephrostomy Tube After Stone Excision
    • Surgical Excision (Laparoscopic, Robotic or Open) – Rarely Used

References

  1. Wal RR. Wikimedia Commons. (License: Public Domain)
  2. Patel C, Modgil V, Luscombe C, Liu S. A unique presentation, and management, of acute urinary retention in a young boy with underlying vesicoureteral reflux. J Surg Case Rep. 2013 Sep 7;2013(9):rjt047. (License: CC BY-NC-3.0)
  3. Dilmen N. Wikimedia Commons. (License: CC BY-SA-3.0)