Editing Nephrolithiasis (section)

== Aetiology ==

* Idiopathic calcium urolithiasis
** Unexplained hypercalciuria with normal serum calcium
** Makes up 70% of patients with stones
* Hypercalcaemic disorders
** Primary hyperparathyroidism
** Prolonged immobilisation - bone resorption
** Milk alkali syndrome
*** Ingestion of large quantities of calcium, vitamin D3 and alkali
*** Leads to hypercalcaemia, alkalosis and possible renal impairment
*** Alkalosis compromises renal excretion of calcium
** Sarcoidosis
** Metastatic cancer
** Cushing's disease
** Hyperthyroidism
* Renal tubular syndromes
** Renal tubular acidosis - calcium phosphate stones
** Cystinuria - genetic disorder - cystine stones which are radio-opaque
* Uric acid lithiasis
** Either excrete excessive amounts of uric acid or have excessively acid urine
** Uric acid remains undissociated and insoluble at pH < 5.5
** Production of uric acid can be increased in myeloproliferative diseases or in those receiving chemotherapy - can cause stones
** Low volume urine can precipitate stones - patients with high-volume ileostomies are at risk
** Mostly faintly radio-opaque
* Enzyme disorders
** Primary hyperoxaliuria
** Xanthinuria
** 2, 8 dihydroadeninuria
* Secondary urolithiasis
** Secondary hyperoxaliuria - after small bowel resection, or in patients with IBD or chronic pancreatitis with a jejunoileal bypass
** Excess fat in the gut binds with calcium, and low calcium reduces the amount of calcium available to bind oxalate
** Dietary excess - these can increase urinary oxalate
*** Rhubarb
*** Spinach
*** Tea
*** Cocoa
*** Chocolate
*** Pepper
** Infection - some organisms break urea to produce ammonia and CO2. The urine becomes alkaline, promoting formation of struvite calculi (magnesium ammonium phosphate) which can develop into a staghorn calculus.
*** Proteus
*** Pseudomonas
*** Staphylococcus
** Obstruction and stasis - delayed crystal washout
** Medullary sponge kidney - calcium stones
** Urinary diversion - combination of infection, acidosis and stasis
** Drugs - acetazolamide, allopurinol (xanthine stones), thiazide diuretics (uric acid stones)
* Others
** Geography
** Climate
** Water intake
** Diet
** Occupation - sedentary jobs in hot environments
** Age - 50% of patients present between 30 and 50
** Slight male preponderance