Renal stones

Question 1

Which renal stones appear opaque on XR

Answer 1

• Calcium oxalate
• Mixed calcium oxalate/ phosphate
• Triple phosphate stones
• Calcium phosphate

Question 2

Which stones appear radio-lucent on XR

Answer 2

urate
xanthine

Question 3

how do cysteine stones appear on XR

Answer 3

semi-opaque (“ground glass” appearance)

Question 4

Most common type of renal stone

Answer 4

calcium oxalate

Question 5

Where are stag horn calculi found?

Answer 5

involve the renal pelvis and extend into at least 2 calyces.

Question 6

When do stag horn calculi develop and what are they composed of?

Answer 6

• develop in alkaline urine
• composed of “struvite”(ammonium magnesium phosphate, triple phosphate).

Question 7

What infections predispose patients to stag horn calculi?

Answer 7

• Ureaplasma urealyticum
• Proteus

Question 8

Risk factors for renal stones

Answer 8

• dehydration
• hypercalciuria
• hyperparathyroidism
• hypercalcaemia
• cystinuria
• high dietary oxalate
• renal tubular acidosis
• medullary sponge kidney
• polycystic kidney disease
• beryllium or cadmium exposure

Question 9

Increased risk of urate stones

Answer 9

• gout
• ileostomy: loss of bicarbonate and fluid = acidic urine
  => precipitation of uric acid

Question 10

Drugs that promote the formation of calcium renal stones

Answer 10

loop diuretics
steroids
acetazolamide
theophylline

Question 11

Which drug which can prevent calcium stones? How?

Answer 11

Thiazide diuretics
- Increase distal tubular calcium resorption

Question 12

Management of renal colic due to stones

Answer 12

• NSAIDs (can give IM if acute)
• IV paracetamol if cant have NSAID
• alpha blockers => promote smooth muscle relaxation and dilation of the ureter

Question 13

What bloods should you order when suspecting a renal stone

Answer 13

• urine dip + culture
• U&E
• FBC/CRP to look for infection
• calcium
• urate
• coag if planning intervention

Question 14

Imaging for renal stones

Answer 14

non-contrast CT KUB

other Ix include US (for pregnant or children)

Question 15

Management of renal stones

Answer 15

< 5mm = watchful waiting

5-10mm = shockwave lithotripsy

10-20 mm =
shockwave lithotripsy OR ureteroscopy

> 20 mm =
percutaneous nephrolithotomy

Question 16

Management of ureteric stones

Answer 16

< 10mm
shockwave lithotripsy +/- alpha blockers

10-20 mm
ureteroscopy

Question 17

Stones < 5 mm will usually pass spontaneously. TRUE/FALSE

Answer 17

TRUE

Question 18

Describe what happens during shockwave lithotripsy

Answer 18

• shock wave is generated external to the patient
• internally cavitation bubbles and mechanical stress lead to stone fragmentation

Question 19

Complications of lithotripsy

Answer 19

• passage of shock waves can result in solid organ injury
• Fragmentation of larger stones may cause ureteric obstruction
• procedure is uncomfortable requiring analgesia before and after

Question 20

What happens during ureteroscopy?

Answer 20

• ureteroscope is passed retrograde through the ureter and into the renal pelvis
• stent is left in situ for 4 weeks after the procedure.

Question 21

For whom is ureteroscopy indicated?

Answer 21

• in individuals (e.g. pregnant females) where lithotripsy is contraindicated
• also in complex stone disease

Question 22

What happens during Percutaneous nephrolithotomy?

Answer 22

• access is gained to the renal collecting system
• intra corporeal lithotripsy or stone fragmentation is performed and stone fragments removed

Question 23

Prevention of calcium stones

Answer 23

• high fluid intake
• add lemon juice to drinking water
• avoid carbonated drinks
• limit salt intake
• potassium citrate
• thiazides diuretics (increase distal tubular calcium resorption)

Question 24

Prevention of oxalate stones

Answer 24

cholestyramine / pyridoxine
- reduces urinary oxalate secretion

Question 25

Prevention of uric acid stones

Answer 25

allopurinol
urinary alkalinization e.g. oral bicarbonate