Stone Disease

Question 1

What is urolithiasis?

Answer 1

• Stone disease
• Common disorder where stones form in kidney or bladder but may present anywhere in urinary tract
• While stones often cause pain at some point, many can remain asymptomatic
• Affect 1-5% of population, with Caucasian men being particularly affected

Question 2

Where do stones commonly get stuck?

Answer 2

• Pelvic-ureteric junction
• Pelvic brim
• Vesico-ureteric junction

Question 3

Stones are usually idiopathic with low fluid intake promoting stone formation, but what else can they be associated with?

Answer 3

• Metabolic → hyperparathyroidism / prolonged immobilisation / gout
• Dietary → high oxalate from tea, nuts, choc, strawbs

Question 4

What type of stones are renal stones?

Answer 4

• Calcium oxalate (65%) → spiky, radio-opaque
• Calcium phosphate (15%) → smooth, large, radio-opaque
• Struvite (10-15%) → large, horny, staghorn, radio-opaque
• Urate (3-5%) → smooth, brown, radiolucent
• Cystine (2%) → yellow, crystalline, semi-opaque

Question 5

What are clinical features of stones?

Answer 5

• Ureteric colic → loin-grain pain, may radiate to testes/labia, is the acute presentation, where ureteric smooth muscle contracts against the blocked stone causing colic; intense and agonising
• Microscopic haematuria → occurs >90% pts
• Gravelly urine → small stones pass painlessly in urine
• UTI → recurrent cystitis or pyelonephritis

Question 6

Which bedside investigations for renal stones?

Answer 6

Urine dipstick → identifies UTI and haematuria

Question 7

Which blood tests for renal stones?

Answer 7

• FBC
• U+Es
• Calcium
• Phosphate
• Uric acid
• Clotting

Question 8

What is the 1^st line choice of imaging for stones?

Answer 8

• Non-contrast CT KUB
• 99% visible
• Helps to exclude other causes

Can also do IV urogram to outline urinary tract and show function and any obstruction or hydronephrosis

Question 9

What is the acute management for stones?

Answer 9

• Pain relief by NSAIDs (eg. diclofenac)
• An obstruction, particularly if infection present, is a urological emergency
• Must be relieved to prevent permanent renal damage
• Percutaneous nephrostomy
  
  • A small tube passed into upper renal pelvis (under US guidance w/ the patient sedated), and the urine collected in an external bag

Question 10

What is the non-emergency management of stones?

Answer 10

• < 5mm → will pass within 4-6 wks
• If complicated (ureteric obstruction, renal developmental abnormality, prev renal transplant) then intervention
• Extracorpeal shockwave lithotripsy (ESWL) → non-invasive procedure used in > 80%; shockwaves focused using USS guidance onto the stone, which is fragmented and passed during micturition
• Ureteroscopy → passed via urethra to retrieve stones using collecting baskets, or to fragment them with intracorporal lithotripsy or lasers
• Percutaneous nephrolithotomy → tract formed via small loin incision directly from loin into renal pelvis + nephroscope inserted, stone retrieved with basket or fragmented - technique useful for large stones or staghorn stones in pelvis

Question 11

Who can’t undergo lithotripsy?

Answer 11

• Pregnant women
• Those taking warfarin

Question 12

Are stones likely to recur?

Answer 12

• Recur in 50% of pts
• Advise high fluid intake to produce >2L urine per day
• Avoid foods with high oxalate content
• Manage hypercalcaemia w/ thiazides
• Gout is managed with allopurinol