PATH - Kidney Stones

Question 1

Calcium oxalate

Answer 1

Calcium stones most common (80%); calcium
oxalate more common than calcium phosphate stones

Shaped like envelope or dumbbell

*Hypocitraturia often associated with DEC urine pH

Radiopaque

Can result from ethylene glycol (antifreeze) ingestion, vitamin C abuse, hypocitraturia, malabsorption (eg, Crohn disease).

Treatment
-thiazides, citrate, low-sodium diet.

Question 2

Calcium phosphate

Answer 2

Wedgeshaped prism

INC pH

Radiopaque

Treatment: thiazides

Question 3

Ammonium magnesium phosphate

Answer 3

Also known as *struvite

*Coffin lid

Commonly form *staghorn calculi

INC pH

Caused by infection with urease⊕ bugs (Proteus mirabilis, Staphylococcus
saprophyticus, Klebsiella)

Radiopaque

Treatment: eradication of underlying infection,
surgical removal of stone

Question 4

Uric acid

Answer 4

Rhomboid or rosettes

Strong association
with hyperuricemia (eg, gout). 

DEC pH

RadiolUcent
Visible on ultrasound

Often seen in diseases with  cell turnover, such as
*leukemia

Treatment: alkalinization of urine, allopurinol

Question 5

Cystine

Answer 5

Hexagonal

DEC pH

Hereditary (autosomal recessive) condition in
which Cystine-reabsorbing PCT transporter loses function, causing cystinuria

Usually begins in childhood.

Can form staghorn calculi.

Sodium cyanide nitroprusside test⊕

“SIXtine” stones have SIX sides

Treatment: low sodium diet, alkalinization of urine, chelating agents if refractory.