Nephroliths

Question 1

Calcium oxalate

Answer 1

Envelope (octahedron)
Precipitates in hypocitraturia (low urine pH)
Risks: Ca in urine, low citrate, high oxalate, hyperPTH, medullary sponge kidney, T1RTA, ethylene glycol
Tx: thiazides (watch K), citrate, low sodium diet
Associated with excessive GI Ca absorption (CROHN’S), decreased renal Ca reabsorption and a decrease in bone density

Hyperoxaluria from low Ca diet, bowel disease

Hyperuricosuria from high protein diet treat with diet changes, water and allopurinol or febuxostat

Question 2

Calcium phosphate

Answer 2

Wedge-shaped prism
Similar risk factors to calcium oxalate
Tx: low Na diet and thiazides

Question 3

Ammonium magnesium phosphate (Struvite)

Answer 3

Coffin lid
Urease + bacteria (Proteus, Staph., Klebs.), urine alkalinization so high pH
Staghorn caliculi

Question 4

Uric acid

Answer 4

Rhomboid/rosette
Radiolucent, need CT
low urine pH, low urine volume, arid climates
Gout, high cell turnover (leukemia)
Tx: alkalinize urine, allopurinol

Question 5

Cysteine

Answer 5

Hexagonal
low pH
radiolucent, less visible on CT
Hereditary (AR) proximal defect of reabsorption (Fanconi)
Poor cysteine, ornithine, lysine, argenine reabsorption
Staghorn caliculi
Tx: alkalinization of urine and low Na diet
No recurrence with transplant