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Kidney Stones/Nephrolithiasis

Kidney stones present with:

  • Renal colic - Excruciating, colicky loin to groin pain

  • Restlessness (differentiates it from peritonitis, where they’re still)

  • Haematuria

  • N+V

  • Oliguria

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“A man with Kidney Stones suffering from the typical symptom - pain in the sides that radiates down to the groin” © https://www.myupchar.com/en (Licensed under CC BY-SA 4.0) https://creativecommons.org/licenses/by-sa/4.0/


Differentials:

  • Pyelonephritis

  • Other ureteric obstructions (e.g. stricture, clot, tumour)

  • MSK pain


Complications:

  • Obstruction

  • Infection with obstructive pyelonephritis


Types

The most common type is a Calcium-based stone (80%). This is usually made of Calcium Oxalate (more common) or Calcium Phosphate. Risk factors for it are Hypercalcaemia and Oliguria.


N.B. Thiazide diuretics can be given to prevent calcium phosphate stones.


Other types of stones include:

  • Uric acid - Radiolucent so aren’t seen on XR, but are seen on CT

  • Struvite (ammonium magnesium phosphate) - Associated with proteus infection, and often leads to Staghorn calculi

  • Cystine - Due to cystinuria, which is an autosomal recessive disease

  • Indinavir - Due to ART


N.B. Only the Uric acid and Indinavir stones are radiolucent, therefore won't be seen on XR.


Investigations

The main investigation to do is a Non-contrast CT KUB.

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“Non-contrast CT of multiple bilateral renal calculi” © Kristie Guite, Louis Hinshaw and Fred Lee (Licensed under CC-BY 3.0) https://creativecommons.org/licenses/by/3.0/


N.B. US KUB good alternative in pregnant women and children.


Other investigations to do are:

  • Urine dip - Shows haematuria and rules out infection

  • Bloods - FBC, U&E, Ca, Uric acid


Management

Lifestyle changes:

  • Stay hydrated

  • Add fresh lemon juice to water (citric acid binds to urinary calcium for excretion)

  • Avoid fizzy drinks

  • Allopurinol or potassium citrate (decrease uric acid)


NSAIDs (e.g. Diclofenac) better analgesic option for colicky, spasmic pains - One-off IM dose shown to be the best option in an acute setting.


If stone < 5mm:

  • Watchful waiting if no signs of obstruction

  • Tamsulosin (expuslive therapy) if stone is in distal ureter


If stone > 1cm:

  • Shock wave lithotripsy - high energy shock waves break up the stone, allowing them to pass naturally

    • Can also be done if the stone < 1cm and usual management options aren't working

  • Ureteroscopy - option for distal/middle ureteric stones and pregnant women - stents can be left to prevent obstruction


If stone > 2cm:

  • Percutaneous nephrolithotomy - used for very large stones and staghorn calculi

  • Open surgery - last option


If the patient becomes septic, a nephrostomy should be done to allow for decompression and immediate drainage of the kidney.



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