Calcium Oxalate
The most common kidney stone forms when urine becomes supersaturated with these two ions.
Calcium + oxalate.
Calcium phosphate stones require urine to be in this pH range.
Alkaline urine (pH > 7)
Uric acid stones occur when urine pH is below this value.
pH < 5.5
Struvite stones require infection with what type of bacteria?
Urease-positive bacteria (Proteus, Klebsiella, Staph saprophyticus)
Cystine stones are caused by a defect in this renal tubular process.
Proximal tubule reabsorption of cystine (cystinuria)
This urinary inhibitor, when low, strongly increases calcium oxalate stone risk.
Citrate
This medication can raise urine pH and increases the risk of calcium phosphate stones.
Acetazolamide
These metabolic conditions increase uric acid stone risk. Name one
Gout
High-purine diet
Metabolic syndrome/insulin resistance
What characteristic shape or pattern can struvite stones form in the kidney?
Staghorn calculi
Cystine stones characteristically have this crystal shape.
Hexagonal crystals
Name two systemic or dietary conditions that increase oxalate levels.
Fat malabsorption (Crohn’s, bariatric surgery)
Excess vitamin C
High oxalate diet (spinach, nuts)
Describe where calcium phosphate stones typically form inside the kidney.
In the collecting ducts in alkaline environments.
Why are uric acid stones radiolucent?
They lack calcium, so they don’t show on X-ray.
Explain why struvite stones grow so rapidly.
Urease-producing bacteria cause ammonia production, rapidly alkalinizing urine which leads to massive precipitation of magnesium-ammonium-phosphate.
Why do cystine stones form more readily in acidic urine?
Cystine is poorly soluble in acidic conditions, so crystals precipitate.
Raising pH improves solubility.