Renal Stones

Types

  • Renal stones vary in size
  • Calcium oxalate forms 80% of stones
  • Calcium phosphate
  • Uric acid (not visible on xray)
  • Struvite (magnesium ammonium phosphate)

 

Staghorn Calculus

  • Renal calculus that forms the shape of a staghorn
  • The body sits in the renal pelvis with horns extending into renal calyxes
  • Usually composed of struvite
  • In recurrent upper urinary tract infections, the bacteria can hydrolyse the urea in urine to ammonia, creating the solid struvite
  • Can be seen on plan xray films

 

Presentation

  • May be asymptomatic and never cause an issue
  • Renal colic
  • Excruciating loin to groin pain
  • Colicky (fluctuating in severity) as the stone moves and settles
  • May have haematuria, nausea, vomiting and oliguria
  • May have symptoms of sepsis if infection present (i.e. fever)

 

Diagnosis

  • Urine dipstick (haematuria in stones but also exclude infection)
  • Bloods for infection and kidney function
  • Renal stones may not be visible on abdominal xray
  • CT KUB (non-contrast scan of kidney, ureters and bladder) is gold standard for identifying stones

 

Management

  • NSAIDs are usually the most effective type of analgesia (e.g. PR diclofenac)
  • Antiemetic if nausea and vomiting
  • Fluids
  • Antibiotics if infection is present
  • Stones less than 6mm have greater than 50% chance of passing without intervention
  • Spontaneous passage can take several weeks
  • Tamsulosin (an alpha-blocker) can be used to help aid spontaneous passage of stones
  • Surgical Interventions in large stones or stones that do not pass

 

Surgical Interventions

  • Extracorporeal Shock Wave Lithotripsy
    • An external machine generates shock waves and directs them at the stone under xray guidance.
    • Breaks the stone to smaller parts to make them easier to pass.
  • Ureteroscopy and Laser Lithotripsy
    • Camera inserted via urethra, bladder and ureter
    • Stone identified
    • The stone is broken up by targeted lasers
    • The smaller parts are easier to pass
  • Percutaneous Nephrolithotomy
    • Performed in theatres under anaesthetic
    • A nephroscope (small camera on a stick) is inserted via a small incision at the patient’s back
    • The scope is inserted through the kidney to assess the ureter
    • Stones can either be removed or broken up to small stones
  • Open Surgery

 

Recurrent Stones

  • One episode of renal stones predisposes patients to further episodes
  • Advice to
    • Increase oral fluids
    • Reduce dietary salt intake
    • Reduce intake of oxalate-rich foods for calcium stones (e.g. spinach, nuts, rhubarb, tea)
    • Reduce intake of urate- rich foods for uric acid stones (e.g. kidney, liver, sardines)
    • Limit dietary protein
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