urinary stones Flashcards
what is Urolithiasis
stones in the urinary system
urinary stones epidemiology (age, sex)
age: 20-50yro
sex: M 3:1 F
why are men more prone to urinary stones (2)
- Testosterone increases oxalate production -> Calcium oxalate stone production
- Women have higher urinary citrate (inhibitor for calcium containing stones)
risk factors for urinary stones
- occupation - sedentary
- hot environment
- diet (animal protein, sat)
- fluid intake
- time of the year (most common in summer)
what can urinary stones be comprised of
- calcium oxalate
- uric acid (monosodium urate)
- calcium phosphate
- struvite
- cystine
what are the majority of urinary stones made up of
calcium oxalate
how do urinary stones form
- supersaturation of urine with a solute (either due to increase in solute or decrease in solvent)
- precipitation out of the solution and formation of crystals
- crystals then act as a nidus, or place where more solutes can deposit and over time it builds up a crystalline structure
what substances can inhibit crystal growth (urinary stones)
- magnesium
- citrate
-> inhibit crystal growth and aggregation, preventing urinary stones from forming in the first place
risk factors for calcium containing urinary stones (5)
- Hypercalcaemia
- Hypercalciuria
- HypOcitraturia
- Hyperuricosuria (daily urinary uric acid excretion of more than 800 mg in men and more than 750 mg in women)
- Hyperoxaluria
when do calcium oxalate crystals form compared to calcium phosphate
Calcium oxalate crystals are more likely to form in ACIDIC urine, whereas calcium phosphate crystals are more likely to form in ALKALINE urine
what can cause hyperoxaluria (3)
- genetic defect that increases oxalate excretion
- defect in liver metabolism
- diet heavy in oxalate-rich foods like rhubarb, spinach, chocolate, nuts, and beer
which urinary stones are radiolucent
radiolucent - don’t show up well on xray:
1. uric acid stones
2. cystine stones
risk factors for uric acid urinary stones (3)
- purine rich diet
- gout
- myeloproliferative disorders
what are struvite stones
“infection stones” - a composite mix of magnesium, ammonium, and phosphate
how do struvite stones form (3)
- infection with bacteria like Proteus mirabilis, Proteus vulgaris, and Morganella morganii;
- the bacteria use the enzyme, urease, to split urea into ammonia and carbon dioxide
- ammonia makes the urine more alkaline and favors precipitation of magnesium, ammonium, and phosphate into jagged crystals called “staghorns”
risk factors for struvite stones
- urinary tract infections
- vesicoureteral reflux
- obstructive uropathies
what are cystine stones
urinary stones composed of the amino acid cysteine which sometimes leaks into the urine (reduced resorption in the PCT) to crystalise and form a yellow or light pink colored stone
urinary stones presentation
- pain - loin, flank, renal colic
- haematuria
- recurrent UTI
- pyonephrosis (pus in the renal collecting system - emergency)t
the presence of a stone where causes the most pain (urinary)
ureteropelvic junction and down the ureter - usually subsides once in the bladder
what is lithotripsy
high energy shock waves passed through the body and used to break stones into small pieces that can easily be excreted
3 sources of shock waves in lithotripsy
- Electrohydraulic
- Piezo electric
- Electromagnetic
urinary stones mgx (5)
- hydration (disoolves precipitate)
- lithotripsy
- surgery
- stent placement
- dissolution therapy
what surgery can be done for urinary stones (2)
- Percutaneous nephrolithotomy (PCNL)
- open stone surgery
what is the dissolution therapy for uric acid stones
- urinary alkalinisation -> NaHCO3 / potassium citrate
- if high serum/urine uric acid levels -> allopurinol
