Kidney stones Flashcards
How does supersaturation lead to kidney stone formation?
Once concentration of an ion exceeds solubility threshold, it begins to precipitate into a stone
What is the most common type of kidney stone?
Calcium-containing stones (calcium-oxalate, calcium phosphate)
What are two risk factors for calcium-containing kidney stones?
Hypercalcuria and/or hyperoxaluria (high oxalate foods, excessive vitamin C, malabsorptive GI conditions)
What is the composition of struvite stones?
Magnesium, ammonium, phosphate, and calcium carbonate
How do struvite stones form?
They require presence of urease-positive bacteria in the urine, which increase the pH to make phosphate insoluble such that it precipates with surrounding magnesium/ammonium/calcium
What type of kidney stone forms the majority of staghorn calculi?
Struvite (forms a large stone that penetrates more than one renal calyx)
What is the most common bacteria responsible for struvite stone formation?
Proteus
What is the driving force of uric acid stone formation?
Hyperuricosuria caused by high purine/protein diet or statesof cell turnover/breakdown
What pH do uric acid stones form at?
Acidic urine (soluble above pH of 5.5)
What is a unique characteristic of uric acid stones?
Radiolucent on x-ray imaging
How are cysteine stones formed?
Due to inherited disorders of metabolism (very rare)
What are 4 general risk factors for kidney stone formation?
- low urine volume (increases concentration of solutes)
- high sodium diet (leads to decreased calcium reabsorption and thus increased urinary calcium/calcium precipitation)
- high protein diet (increased acid load, buffered by release of Ca from bone reservoirs)
- hypocitraturia (citrate inhibits stone formation)
What is the clinical presentation of kidney stones?
Acute flank pain, hematuria
What type of kidney stones are not visible on x-ray?
Uric acid stones (radiolucent)
What is the treatment for kidney stones?
pain control and fluids usually (they pass on their own), surgery may be required if they cannot pass (rare)