Nephrolithiasis (kidney stones) can be made up of numerous types of material, including calcium, uric acid, cystine and struvite. Generally, stones develop on the renal papillae or in the collecting system of the kidney. Stones are a common cause of hematuria (blood in the urine) and flank pain. Obstruction occurs when a stone cannot pass through the ureter smoothly. When stones grow too large to enter the ureter, they often grow in size and develop a "staghorn" appearance. Stone types that can cause a staghorn include struvite, cystine and uric acid stones.
Calcium Stones
Calcium oxalate and calcium phosphate stones are approximately 75 to 85 percent of all stones. These stones are particularly more common in men. The etiology of calcium stones depends on the cause. Hereditary causes include distal renal tubular acidosis, hereditary hyperoxaluria and hypocitratria (low citrate) and idiopathic hypercalciuria. Diet can cause hyperuricosuria, leading to stones. Cancer that leads to primary hyperparathyroidism can cause calcium stones as well. Treatments for calcium stones are dependent upon the etiology and usually aim at prevention. The most common type of calcium stone etiology is idiopathic hypercalciuria, and treatment is to lower the level of urinary calcium by giving a thiazine diuretic.
Uric Acid Stones
Uric acid stones are half the time seen in patients with gout but can be present in patients who do not have gout. The stones are red-orange in color in the urine. Causes of uric acid stones are gout, dehydration, Lesch-Nyhan syndrome, malignant tumors and idiopathic. Most of these conditions are hereditary. Treatment is aimed at lowering serum levels of uric acid with allopurinol.
Cystine Stones
Cystine stones are fairly uncommon, making up approximately 1 percent of all stones. These stones occur evenly in males and females. They have a hereditary etiology. They appear lemon yellow in urine due to sulfur content. Treatment consists of increasing fluids, alkali and D-penicillinamine.
Struvite Stones
Struvite stones account for 10 to 15 percent of all stones. They are more common in females. The bacterial species Proteus produces urease when chronically infecting the genitourinary tract. The stones can grow to a very large size in the renal pelvis and calyces. They often produce a "staghorn" appearance. The best treatment for struvite stones is with antibiotics to eradicate the Proteus species and treat the infection.
References
- "Current Medical Diagnosis and Treatment"; McPhee S.J., Papadakis M.A., Tierney L.M.; McGraw Hill; 2007
- National Kidney and Urologic Diseases Information Clearinghouse: Kidney Stones in Adults
