Renal stones Flashcards
Which renal stones appear opaque on XR
- Calcium oxalate
- Mixed calcium oxalate/ phosphate
- Triple phosphate stones
- Calcium phosphate
Which stones appear radio-lucent on XR
urate
xanthine
how do cysteine stones appear on XR
semi-opaque (“ground glass” appearance)
Most common type of renal stone
calcium oxalate
Where are stag horn calculi found?
involve the renal pelvis and extend into at least 2 calyces.
When do stag horn calculi develop and what are they composed of?
- develop in alkaline urine
- composed of “struvite”(ammonium magnesium phosphate, triple phosphate).
What infections predispose patients to stag horn calculi?
- Ureaplasma urealyticum
- Proteus
Risk factors for renal stones
- dehydration
- hypercalciuria
- hyperparathyroidism
- hypercalcaemia
- cystinuria
- high dietary oxalate
- renal tubular acidosis
- medullary sponge kidney
- polycystic kidney disease
- beryllium or cadmium exposure
Increased risk of urate stones
- gout
- ileostomy: loss of bicarbonate and fluid = acidic urine
=> precipitation of uric acid
Drugs that promote the formation of calcium renal stones
loop diuretics
steroids
acetazolamide
theophylline
Which drug which can prevent calcium stones? How?
Thiazide diuretics
- Increase distal tubular calcium resorption
Management of renal colic due to stones
- NSAIDs (can give IM if acute)
- IV paracetamol if cant have NSAID
- alpha blockers => promote smooth muscle relaxation and dilation of the ureter
What bloods should you order when suspecting a renal stone
- urine dip + culture
- U&E
- FBC/CRP to look for infection
- calcium
- urate
- coag if planning intervention
Imaging for renal stones
non-contrast CT KUB
other Ix include US (for pregnant or children)
Management of renal stones
< 5mm = watchful waiting
5-10mm = shockwave lithotripsy
10-20 mm =
shockwave lithotripsy OR ureteroscopy
> 20 mm =
percutaneous nephrolithotomy
Management of ureteric stones
< 10mm
shockwave lithotripsy +/- alpha blockers
10-20 mm
ureteroscopy
Stones < 5 mm will usually pass spontaneously. TRUE/FALSE
TRUE
Describe what happens during shockwave lithotripsy
- shock wave is generated external to the patient
- internally cavitation bubbles and mechanical stress lead to stone fragmentation
Complications of lithotripsy
- 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
What happens during ureteroscopy?
- ureteroscope is passed retrograde through the ureter and into the renal pelvis
- stent is left in situ for 4 weeks after the procedure.
For whom is ureteroscopy indicated?
- in individuals (e.g. pregnant females) where lithotripsy is contraindicated
- also in complex stone disease
What happens during Percutaneous nephrolithotomy?
- access is gained to the renal collecting system
- intra corporeal lithotripsy or stone fragmentation is performed and stone fragments removed
Prevention of calcium stones
- high fluid intake
- add lemon juice to drinking water
- avoid carbonated drinks
- limit salt intake
- potassium citrate
- thiazides diuretics (increase distal tubular calcium resorption)
Prevention of oxalate stones
cholestyramine / pyridoxine
- reduces urinary oxalate secretion
Prevention of uric acid stones
allopurinol
urinary alkalinization e.g. oral bicarbonate
