STONE · TOPIC
MECHANISM · CAUSE
FEATURES
TREATMENT · CLUE
Calcium oxalate
most common
Idiopathic hypercalciuria, ↓ urinary citrate, low fluid intake; ↑ oxalate (Crohn, ileal resection, bariatric surgery, ethylene glycol, high-dose vitamin C)
Radiopaque; envelope or dumbbell crystals; any urine pH
Thiazide (↓ urine Ca²⁺), potassium citrate, fluids, low sodium, normal calcium diet
Alkaline urine: type 1 RTA, primary hyperparathyroidism, topiramate, acetazolamide
Radiopaque; wedge-shaped prisms
Thiazides; treat cause
Urease-producing bacteria (Proteus, Klebsiella, S saprophyticus) split urea → NH₃ → alkaline urine
Radiopaque; staghorn calculi filling the pelvis; coffin-lid crystals
Eradicate infection + remove stone surgically
Acidic urine (pH < 5.5), hyperuricemia: gout, tumor lysis, myeloproliferative disease, chronic diarrhea/ileostomy, diabetes (low NH₄⁺)
Radiolucent (seen on CT/US); yellow-red rhomboid or rosette crystals
Alkalinize urine (potassium citrate), allopurinol, fluids
Cystinuria (AR): defective PCT reabsorption of cystine, ornithine, lysine, arginine
Faintly radiopaque; hexagonal crystals; staghorn in children; ⁺ cyanide-nitroprusside test
Alkalinize, fluids, tiopronin / penicillamine
Stone obstructs and stretches the ureter
Severe colicky flank pain → groin/testis/labia; hematuria; nausea; restless patient
Noncontrast CT · US in pregnancy/children · NSAIDs, tamsulosin
Narrowest points of the ureter
UPJ, crossing the iliac vessels (pelvic brim), UVJ (narrowest)
Stones < 5 mm usually pass
Obstruction ± infection
Hydronephrosis, pyelonephritis; obstructed infected kidney → sepsis
Urgent decompression (stent or nephrostomy)
↑ PTH → hypercalcemia → hypercalciuria
Recurrent calcium stones + bone pain + hypercalcemia
"Stones, bones, groans, moans"
Drug crystallizes in tubules or urine
Indinavir (radiolucent), acyclovir, sulfadiazine, triamterene; topiramate → Ca phosphate
Hydration