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598 SeCTIOn III Renal ` RENAL—PAthoLogy Renal ` RENAL—PAthoLogy

Kidney Can lead to severe complications such as hydronephrosis, pyelonephritis, and acute kidney injury. Obstructed
stones stone presents with unilateral flank tenderness, colicky pain radiating to groin, hematuria. Treat and prevent
by encouraging fluid intake.
CoNtENt PRECiPitAtEs With X-RAy FiNDiNgs Ct FiNDiNgs URiNE CRystAL NotEs
Calcium Calcium Radiopaque Radiopaque Shaped like Calcium stones most common (80%); calcium
oxalate: envelope A oxalate more common than calcium
hypocitraturia or dumbbell phosphate stones.
Can result from ethylene glycol (antifreeze)
ingestion, vitamin C abuse, hypocitraturia
(associated with  urine pH), malabsorption
(eg, Crohn disease).
Treatment: thiazides, citrate, low-sodium diet.
Calcium Radiopaque Radiopaque Wedge- Treatment: low-sodium diet, thiazides.
phosphate: shaped
 pH prism
Ammonium  pH Radiopaque Radiopaque Coffin lid B Account for 15% of stones. Caused by infection
magnesium with urease ⊕ bugs (eg, Proteus mirabilis,
phosphate Staphylococcus saprophyticus, Klebsiella)
(struvite) that hydrolyze urea to ammonia Ž urine
alkalinization. Commonly form staghorn
calculi C .
Treatment: eradication of underlying infection,
surgical removal of stone.
Uric acid  pH RadiolUcent Minimally Rhomboid D About 5% of all stones. Risk factors:  urine
visible or rosettes volume, arid climates, acidic pH.
Strong association with hyperuricemia
(eg, gout). Often seen in diseases with  cell
turnover (eg, leukemia).
Treatment: alkalinization of urine, allopurinol.
Cystine  pH Faintly radi- Moderately Hexagonal E Hereditary (autosomal recessive) condition in
opaque radiopaque which Cystine-reabsorbing PCT transporter
loses function, causing cystinuria. Transporter
defect also results in poor reabsorption
of Ornithine, Lysine, Arginine (COLA).
Cystine is poorly soluble, thus stones form
in urine. 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 (eg, penicillamine) if
refractory.
A B C D E

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