Nephrolithiasis or kidney stone disease is a common disorder that affects both men and women. Kidney stone disease occurs more commonly in men than in women. The disease state gives rise to symptoms such as lumbar pain, nausea, vomiting, bloody and foul smelling urine and pain and burning on urination. The prevalence of Nephrolithiasis is found to be increasing.
Sometimes stones recur later in life, in people who have already developed a stone. There are different types of kidney stones and the cause and prevention of these also differ. Majority of these stones consist of calcium phosphate and calcium oxalate. Uric acid, struvite and cystine stones are less common.
Kidney stones develop when dissolved minerals in the urine supersaturate. To understand the causes of kidney stones and ways to prevent their formation, it is important to look at the factors that aid stone formation. These factors that favor stones to form include low urine volumes, saturation of the urine with substances that form stones, and urinary tract infections.
The climate plays a big role in formation of stones in the kidneys. Hot climates such as in the Middle West and in the tropics promote increased water loss through sweating. Water loss and chronic dehydration produces low urine volume which helps dissolved substances in the urine to precipitate out as stones.
When excessive amounts of calcium, oxalate, uric acid and cystine is excreted these develop into stones. Excretion of excessive quantities of these substances is due to various reasons including, high intake of food that leads to accumulation of these substances, metabolic diseases and obesity, underlying disease conditions such as gout.
High dietary intake of sodium, purines and proteins is found to cause calcium and oxalate stones. Oxalate stones also develop when dietary intake of calcium is low and oxalate is high. Low calcium diets reduce crystallization of oxalate in the gut and thereby promoting the absorption of calcium ions. Genetic variations in the transporters of oxalate in the blood also contribute to hyperoxaluria (hyper excretion of oxalate in the urine).
Primary gout and uricosuric agents leads to uricosuria (hyper excretion of uric acid in urine). Uricosuria lead to both uric acid and calcium oxalate stones. Low urine citrate results in the decrease of citrate that is available for binding with calcium. This binding of citrate with calcium inhibits crystallization.
Bacterial infection with organisms that hydrolyses urea into ammonium and hydroxyl ions provides persistently alkaline urine that promotes the formation of struvite stones. The incidence of urinary tract infections is higher in women than in men thus struvite stones seem to be more common in women.
The prevention of kidney stones depends on the type of stone and eliminating the causes and treating underlying conditions that lead to stone development. Diet is also an important factor when it comes to preventing certain stones.
Diets rich in sodium and animal protein should be avoided in preventing calcium and oxalate stones. Purine and oxalate rich food should be cut down to prevent oxalate and uric acid stones. Purine rich foods include beans, mushrooms, spinach, yeast, poultry and alcoholic beverages such as beer etc.
Oxalate rich foods such as soy, brewed tea, cocoa, lamb, nuts, berries, rhubarb, beets and dried figs etc must be taken less to prevent oxalate stones. High intake of vitamin C must also be avoided in hyperoxaluria to prevent further oxalate stones from developing.
It is not recommended to cut down on dietary calcium as with less calcium to bind with oxalate in the gut, these free oxalate ions can supersaturate in the urine. A higher calcium diet may actually reduce the chances of forming calcium stones. However, calcium and oxalate intake must be in balance.
Fresh fruits and vegetables and juices are recommended in preventing kidney stones. These are rich in potassium which helps in preventing calcium stones. Cranberry juice is found to have anti-stone forming properties and can be useful in preventing calcium oxalate stones. Citrus fruit juices are helpful in preventing kidney stones as they contain citrate and potassium. Citrate inhibits stone formation by binding with calcium while potassium seems to reduce urinary calcium excretion. Black current juice reduces acidity and makes urine more alkaline which helps prevent uric acid stones.
Adequate water intake is needed to dilute urine and produce a high daily urine volume that will prevent the formation of stones. Drinking lots of water may help in passing the stone in the urine. Normally about 2 liters of water needs to be drunk per day. Those who already have a kidney stone must drink 3 to 3.5 liters of water per day to prevent further stones from developing. Hydration also helps prevent recurrence of stones.
Conditions that lead to hypercalciuria, such as primary hyperparathyroidism and other metabolic diseases (e.g. metabolic acidosis) must be corrected in order to prevent calcium stones. Removal of the parathyroid glands reduces the formation of further calcium stones. Metabolic acidosis is corrected by treating with sodium bicarbonate or potassium citrate.
Recurrent bacterial infections should be treated and prevented to reduce the formation of struvite stones. Preventive measures such as the use of cranberry juice and antibiotics to treat bacterial infections can reduce the chances of developing infection stones.