Urolithiasis (Kidney Stones)

Epidemiology and Etiology:

· M > F

· 20-30y peak

· Familial and hereditary predisposition

· Inborn errors of metabolism

· Most important causal factor is increased urinary concentration of the stones’ constituents

· Exceeding their solubility (supersaturation)

· Changes in urinary pH

· Decreased urine volume

· Deficiency of inhibitors of crystal formation

· Pyrophosphate

· Diphosphanate

· Citrate

· Glycosaminoglycans

· Osteopontin

· nephrocalcin

· Calcium oxalate and phosphate (70%)

· Idiopathic hypercalciuria (50% of those)

· Hypercalcemia and hypercalciuria (10%)

· Hyperoxaluria (5%)

· Enteric hyperoxaluria

· Acquired - intestinal overabsorption in patients with enteric diseases

· Vegetarians – diet rich in oxalates

· Hereditary (primary hyperoxaluria)

· Enteric (4.5%)

· Hyperabsorption of calcium from the intestine

· Primary (0.5%)

· Hyperuricosuria (20%)

· Increased uric acid secretion (hyperuricosuric calcium nephrolithiasis

· “nucleation” of calcium oxalate by uric acid crystals in the collecting ducts

· Hypocitraturia

· Renal hypercalciuria

· Impairment in renal tubular reabsorption of calcium

· No known metabolic abnormality (15-20%)

· Magnesium ammonium phosphate (Struvite) (15-20%)

· Some of the largest stones

· Infections by urea-splitting bacteria (Proteus, some Staph)

· Convert urea to ammonia

· Uric acid (5-10%)

· Associated with hyperuricemia

· Gout

· Leukemias, rapid cell turnover

· Associated with hyperuricosuria

· Idiopathic (50% of uric stones)

· Cystine (1-2%)

· Genetic defects in renal aborption of amino acids (ex. cystine)

· Others or unknown (~5%)

Common sites:

· Renal pelvices and pelves

· bladder

Gross features:

· X-ray

· Calcium stones are opaque

· Ureic acid stones are lucent

· Unilateral in 80%

·

Histologic features:

·

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

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Other features:

· Complications

· Urinary obstruction

· Ulceration and bleeding

· Colic (small stones in ureters)

· Infection

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References:

· Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. 7th ed. Saunders; 2004:1552.