Know the frequency of different types of stones and the status of blood and urine calcium in patients with calcium containing stones.

• Calcium containing stones (75%) are composed mostly of Ca oxalate and Ca phosphate

  • 10% show both hypercalcemia and hypercalciuria

    • Due to hypercalcemic states

      • HyperPTH

      • Diffuse bone disease

      • Sarcoidosis

      • Renal tubular acidosis

  • 50% have hypercalciuria w/o hypercalcemia

    • Increased absorption from GI

    • Inhibited tubular absorption

    • Increased Ca-Mg ATPase activity

  • 25% have neither hypercalciuria nor hypercalcemia

  • 20% have increased uric acid secretion

• Triple (phosphate) / struvite stones (15%) are composed of Mg ammonium phosphate

• Uric acid stones (6%)

• Cysteine stones (1-2%)

Know the chemical nature and cause of staghorn calculi.

• Alkalinization of urine by ammonia causes precipitation of Mg ammonium phosphate salts

• Typically follows infections w. urea-splitting bacteria (Proteus, some Staph)

Know the possible causes of uric acid stones and that uric acid stones are radiolucent.

• Occurs in patients w/ hyperuricemia (e.g., gout, leukemia)

• More than 50% do NOT have hyperuricemia

Know the pathogenesis of urolithiasis

• Supersaturation of urine w/ stone’s component(s)

• Changes in urinary content of mucoproteins that form organic matrix (1-5%)

• Change in urine pH

• Presence of bacteria may influence formation

• Inhibitors of crystal formation are deficient

• Pyrophosphate

• Diphosphanate

• Citrate

• Nephrocalcin

Know the most common sites of stones and clinical manifestations of stones.

• Stones generally are formed in calyces / pelvis / urinary bladder

• Smaller stones are usually symptomatic because they enter ureters and cause colic

• Hematuria

• May be complicated by infection or obstructed uropathy

Category: Pathology Notes