Kidney stones, or renal calculi, are formed from mineral salts or uric acid in the urine. An estimated 10 percent of Americans develop kidney stones at some point in their lives. Mild cases may mimic gastroenteritis, or stomach flu. Symptoms of kidney stones include specific patterns of pain, profuse sweating, urine that is cloudy, odorous or contains pus and blood, reduced urine output and sometimes chills and fever. Treatment consists of flushing with fluids and taking pain medication at home. Hospitalization and surgical treatments are sometimes necessary.
Pain Patterns
The type of pain experienced is relative to the location of stones. Renal colic is caused by the smooth muscle inside the ureter trying to work the stone down and out. When the stone is in the kidney and upper ureter, pain is felt in the upper back and side, or flank. In males, referred pain may be felt in the testicle on the affected side.
The stone then travels approximately 20 cm to the bladder and the pain moves forward, radiating down to the groin; it no longer will be felt in the testicles. When the stone enters the bladder tunnel, pain radiates down to the scrotum in males and the vulva in females. Bladder urgency is a reaction to irritation, becoming more uncomfortable as the uretal orifice slowly dilates. When the stone suddenly pops into the bladder, relief is instant. Passage of the stone through the urethra to the outside of the body may burn, but it rarely causes severe pain.
Causes
Healthy kidney function depends on the secretion of various protective compounds and natural mechanisms that control the pH of urine and keep mineral salts suspended in solution. When the protective mechanisms fail to keep these substances dissolved, uric acid, phosphates and calcium oxalate can crystallize and form jagged or smooth stones.
Eighty percent of kidney stones are formed from calcium oxalate. Calcium stones often run in families. Dietary intake of refined carbohydrates, especially sugar and high fructose corn syrup, causes more calcium to build up in the urine by triggering the release of insulin.
Chronic dehydration concentrates urine and stresses the kidneys. A diet high in animal protein and low in fruits and vegetables is associated with kidney stones. Those with gout, inflammatory bowel disease, diabetes, a sedentary lifestyle and overactive parathyroid glands are at higher risk. White men ages 30 to 50 have more kidney stones than women, blacks or children. In 50 percent of kidney stone cases, another stone forms within a few years.
Types
There are four main types of kidney stones. Calcium oxalate is the most common. Uric acid stones are associated with gout and excessive consumption of red meat. Struvite stones are unrelated to metabolism; they are caused by infection. Women may get struvite stones as a result of recurrent urinary tract infections. Cystine stones are caused by a rare congenital condition, cystinuria.
References
- National Kidney Foundation: Kidney Stones
- "No More Kidney Stones"; John Rodman, M.D., R. Ernest Sosa, M.D., Cynthia Seidman, M.S., R.D., 2007
