Nephrolithiasis (Urolithiasis)

Risk factors

• dehydration
• hypercalciuria, hyperparathyroidism, hypercalcaemia
• cystinuria
  • cystine stones, which can occur in patients with cystinuria, a recessive genetic disorder involving defective renal tubular transport of certain amino acids including cystine. Cystinuria might be more common in patients with HIV, especially those on the medication Indinavir, used as a protease inhibitor in the treatment of HIV.
• high dietary oxalate or increased oxalate absorption (as in Chron's disease)
• Primary hyperoxaluria
  • Primary hyperoxaluria is an autosomal recessive disorder, characterized by recurrent kidney stone formation due to increased urinary oxalate. The mutation occurs in genes coding for either of two liver enzymes (AGXT or GRHPR), which leads to deficiency of the enzymes and accumulation of glyoxylate, a precursor of oxalate. This results in calcium oxalate stones with a characteristic 'envelope' crystal shape in urine.
• Fat malabsorption
• renal tubular acidosis
• medullary sponge kidney, polycystic kidney disease
• beryllium or cadmium exposure

Risk factors for urate stones

• gout
• ileostomy: loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid

Drug causes

• drugs that promote calcium stones: loop diuretics, steroids, acetazolamide, theophylline
• thiazides can prevent calcium stones (increase distal tubular calcium resorption)

Initial management of renal colic

Pain management and medical therapy

• both BAUS and NICE recommend an NSAID as the analgesia of choice for renal colic NICE
  • whilst diclofenac has been traditionally used the increased risk of cardiovascular events with certain NSAIDs (e.g. diclofenac, ibuprofen) should be considered when prescribing