Renal Stones and Renal Cancer Flashcards
Calcium Stones
Imaging findings on xray
RF for calcium stones
- Approximately 80% of kidney stones contain calcium oxalate, calcium phosphate or both
- Calcium stones are RADIOPAQUE on plain radiograph
- Hypercalciuria, hyperoxaluria and hypocitraturia are risk factors for calcium stones
Calcium oxalate stones Associated RF + aetiology Urine pH Crystal appearance Radiopacity Prophylaxis
Incidence 75%
Aetiology
- Hypercalciuria
- Hyperoxaluria
- Hypocitraturia
- Can result from increased intake of ethylene glycol (antifreeze), vitamin C
- Associated with IBD, eg: UC and CD due to malabsorption
Decreased urine pH (acidic)
Biconcave dumbbells or bipyramidal envelopes
Radiopaque
Urine alkalinsation
Calcium phosphate stones Associated RF + aetiology Urine pH Crystal appearance Radiopacity Prophylaxis
- Aetiology: hyperparathyroidism, type 1 RTA
- Increased urine pH
- Wedge shaped prisms
- Radiopaque
- Urine acdification
Uric acid stones Associated RF + aetiology Urine pH Crystal appearance Radiopacity Prophylaxis
Incidence 10%
- Aetiology: gout, hyperuricemia, hyperuricosuria
- High cell turnover, eg: leukemia, chemotherapy
- Urine pH (acidic)
- Radiolucent
- Urine alkalinzation
Struvite stones Associated RF + aetiology Urine pH Crystal appearance Radiopacity Prophylaxis
5-10%
- Aetiology: UTI with urease producing bacteria, eg: proteus mirabilis, Staph saprophyticus, klebsiella
High urine pH
Rectangular prisms, coffin lid appearance
Weakly radiopaque
Urine acidification
Lead to staghorn calculi:
Staghorn stones are large branching stones that fill part of all of the renal pelvis and renal calyces and they can be complete or partial depending on the level of occupancy of the collecting system.
Cystine stones Associated RF + aetiology Urine pH Crystal appearance Radiopacity Prophylaxis
Cystinuria (hereditary) Decreased urine pH (acidic) Hexagon shape - the cystine chapel has 6 sides. Weakly radiopaque Urine alkalinsation
Xanthine stones Associated RF + aetiology Urine pH Crystal appearance Radiopacity Prophylaxis
Xanthinuria - hereditary deficiency of xanthine oxidase (failure to convert xanthine to uric acid) or allopurinol
Generally independent of urine pH
Amorphous
Radiolucent
Which stones are radioopaque (bright) and which are radiolucent (dark)?
Radioopaque (bright): calcium phosphate, calcium oxalate, struvite
Radiolucent (dark): uric acid, cysteine
“uric acid stones are radiolUcent (xray negative)
How does IBD cause kidney stones?
Crohn disease leads to increased oxalate absorption via malabsorption of fatty acids, which leads to kidney stones
Increased intestinal absorption of oxalate, eg: due to fatty acid malabsorption (eg: crohn disease, UC, short bowel syndrome)
- Calcium normally binds oxalate to form calcium oxalate which is excreted via faeces
- In conditions associated with fatty acid malabsorption due to bile acid reabsorption, calcium preferentially binds free fatty acids, leading to excess free oxalate and therefore increase oxalate absorption
What are drugs that can cause kidney stones.
Crystallisation of drug compounds in the urine which is commonly associated with:
- aciclovir
- idinavir
- sulfonamides
- fluoroquinolones
- ceftriaxone
Stone formation due to alterations in urine composition, which are commonly associated with:
- Acetazolamide
- Frusemide
- Topiramate
- Vit D, vit A
- Aluminium magnesium hydroxide
- Calcium
Imaging for kidney stones
Non contrast abdominopelvic CT
US
What size stones pass or are unlikely to pass
- <5mm: >90% pass spontaneously with supportive care
- >7mm: unlikely to pass
How to treat :
- complex renal calculi and staghorn calculi
- stone burden of less than 2 cm in pregnant females
- stone burden of less than 2cm in aggregate
- complex renal calculi and staghorn calculi: percutaneous nephrolithotomy
- stone burden of less than 2 cm in pregnant females: ureteroscopy
- stone burden of less than 2cm in aggregate: lithotripsy
