Kidney Stones

KIDNEY STONES (Also known as NEPHROLITHIASIS)

Definition

A kidney stone is a solid, pebble-like piece of material that can form in one or both of your kidneys when high levels of certain minerals are in your urine. Kidney stones rarely cause permanent damage if treated by a health care professional.​

What is a kidney stone?

A kidney stone is a hard, crystalline mineral material formed within the kidney or urinary tract. Kidney stones are a common cause of blood in the urine (hematuria) and often severe pain in the abdomen, flank, or groin. Kidney stones are sometimes called renal calculi.

The condition of having kidney stones is termed nephrolithiasis. Having stones at any location in the urinary tract is referred to as urolithiasis, and the term ureterolithiasis is used to refer to stones located in the ureters.

Who is at risk for kidney stones?

• Anyone may develop a kidney stone, but people with certain diseases and conditions (see below) or those who are taking certain medications are more susceptible to their development. Urinary tract stones are more common in men than in women. 
• Most urinary stones develop in people 20 to 49 years of age, and those who are prone to multiple attacks of kidney stones usually develop their first stones during the second or third decade of life. 
• People who have already had more than one kidney stone are prone to developing further stones.
• In residents of industrialized countries, kidney stones are more common than stones in the bladder. 
• The opposite is true for residents of developing areas of the world, where bladder stones are the most common. This difference is believed to be related to dietary factors. 
• Over the last few decades, the percentage of people with kidney stones has been increasing, most likely related to the obesity epidemic.
• A family history of kidney stones is also a risk factor for developing kidney stones. Kidney stones are more common in Asians and Caucasians than in Native Americans, Africans, or African Americans.
• Uric acid kidney stones are more common in people with chronically elevated uric acid levels in their blood (hyperuricemia).
• A small number of pregnant women develop kidney stones, and there is some evidence that pregnancy-related changes may increase the risk of stone formation. Factors that may contribute to stone formation during pregnancy include a slowing of the passage of urine due to increased progesterone levels and diminished fluid intake due to a decreasing bladder capacity from the enlarging uterus. 
• Healthy pregnant women also have a mild increase in their urinary calcium excretion. However, it remains unclear whether the changes of pregnancy are directly responsible for kidney stone formation or if these women have another underlying factor that predisposes them to kidney stone formation.

PREVALANCE OF KIDNEY STONES IN INDIA

Kidney stones are common in industrialized nations with an annual incidence of 0.5% to 1.9%.

In India upper and lower urinary tract stones occur frequently but the incidence shows wide regional variation.

The incidence of renal calculi is comparatively low in the southern part of country compared to other parts.

What causes kidney stones?

Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine. The most common type of kidney stone contains calcium in combination with either oxalate or phosphate. A majority of kidney stones are calcium stones. Other chemical compounds that can form stones in the urinary tract include uric acid, magnesium ammonium phosphate (which forms struvite stones; see below), and the amino acid cysteine.

• Dehydration from reduced fluid intake or strenuous exercise without adequate fluid replacement increases the risk of kidney stones. Obstruction to the flow of urine can also lead to stone formation. In this regard, climate may be a risk factor for kidney stone development, since residents of hot and dry areas are more likely to become dehydrated and susceptible to stone formation.

• Kidney stones can also result from infection in the urinary tract. These are known as struvite or infection stones. Metabolic abnormalities, including inherited disorders of metabolism, can alter the composition of the urine and increase an individual's risk of stone formation.

Other medical conditions which cause kidney stones

A number of different medical conditions can lead to an increased risk for developing kidney stones:

• Gout results in chronically increased amount of uric acid in the blood and urine and can lead to the formation of uric acid kidney stones.
• Hypercalciuria (high calcium in the urine), another inherited condition, causes stones in more than half of cases. In this condition, too much calcium is absorbed from food and excreted into the urine, where it may form calcium phosphate or calcium oxalate kidney stones.
• Other conditions associated with an increased risk of kidney stones include hyperparathyroidism, kidney diseases such as renal tubular acidosis, and other inherited metabolic conditions, including cystinuria and hyperoxaluria.
• Chronic diseases such as diabetes and high blood pressure (hypertension) are also associated with an increased risk of developing kidney stones.
• People with inflammatory bowel disease are also more likely to develop kidney stones.
• Those who have undergone intestinal bypass or ostomy surgery are also at increased risk for kidney stones.
• Some medications also raise the risk of kidney stones. These medications include some diuretics, calcium-containing antacids, and the protease inhibitor indinavir (Crixivan), a drug used to treat HIV infection.
• Dietary factors and practices may increase the risk of stone formation in susceptible individuals. In particular, inadequate fluid intake predisposes to dehydration, which is a major risk factor for stone formation. Other dietary practices that may increase an individual's risk of forming kidney stones include a high intake of animal protein, a high-salt diet, excessive sugar consumption, excessive vitamin D supplementation, and excessive intake of oxalate-containing foods such as spinach. Interestingly, low levels of dietary calcium intake may alter the calcium-oxalate balance and result in the increased excretion of oxalate and a propensity to form oxalate stones.
• Hyperoxaluria as an inherited condition is uncommon and is known as primary hyperoxaluria. The elevated levels of oxalate in the urine increase the risk of stone formation. Primary hyperoxaluria is much less common than hyperoxaluria due to dietary factors as mentioned above.

What are the signs and symptoms of kidney stones?

Symptoms

A kidney stone may not cause symptoms until it moves around within your kidney or passes into your ureter — the tube connecting the kidney and bladder. At that point, you may experience these signs and symptoms:

·         Severe pain in the side and back, below the ribs

·         Pain that radiates to the lower abdomen and groin

·         Pain that comes in waves and fluctuates in intensity

·         Pain on urination

·         Pink, red or brown urine

·         Cloudy or foul-smelling urine

·         Nausea and vomiting

·         Persistent need to urinate

·         Urinating more often than usual

·         Fever and chills if an infection is present

·         Urinating small amounts

Pain caused by a kidney stone may change — for instance, shifting to a different location or increasing in intensity — as the stone moves through your urinary tract.

When to see a doctor

Make an appointment with your doctor if you have any signs and symptoms that worry you.

Seek immediate medical attention if you experience:

·         Pain so severe that you can't sit still or find a comfortable position

·         Pain accompanied by nausea and vomiting

·         Pain accompanied by fever and chills

·         Blood in your urine

·         Difficulty passing urine

Types of kidney stones

Knowing the type of kidney stone helps determine the cause and may give clues on how to reduce your risk of getting more kidney stones. If possible, try to save your kidney stone if you pass one so that you can bring it to your doctor for analysis.

Types of kidney stones include:

·         Calcium stones. Most kidney stones are calcium stones, usually in the form of calcium oxalate. Oxalate is a naturally occurring substance found in food and is also made daily by your liver. Some fruits and vegetables, as well as nuts and chocolate, have high oxalate content.

Dietary factors, high doses of vitamin D, intestinal bypass surgery and several metabolic disorders can increase the concentration of calcium or oxalate in urine.

Calcium stones may also occur in the form of calcium phosphate. This type of stone is more common in metabolic conditions, such as renal tubular acidosis. It may also be associated with certain migraine headaches or with taking certain seizure medications, such as topiramate (Topamax).

·         Struvite stones. Struvite stones form in response to an infection, such as a urinary tract infection. These stones can grow quickly and become quite large, sometimes with few symptoms or little warning.

·         Uric acid stones. Uric acid stones can form in people who don't drink enough fluids or who lose too much fluid, those who eat a high-protein diet, and those who have gout. Certain genetic factors also may increase your risk of uric acid stones.

·         Cystine stones. These stones form in people with a hereditary disorder that causes the kidneys to excrete too much of certain amino acids (cystinuria).

Risk factors:

Factors that increase your risk of developing kidney stones include:

·         Family or personal history. If someone in your family has kidney stones, you're more likely to develop stones, too. And if you've already had one or more kidney stones, you're at increased risk of developing another.

·         Dehydration. Not drinking enough water each day can increase your risk of kidney stones. People who live in warm climates and those who sweat a lot may be at higher risk than others.

·         Certain diets. Eating a diet that's high in protein, sodium (salt) and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much salt in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.

·         Being obese. High body mass index (BMI), large waist size and weight gain have been linked to an increased risk of kidney stones.

·         Digestive diseases and surgery. Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the levels of stone-forming substances in your urine.

·         Other medical conditions. Diseases and conditions that may increase your risk of kidney stones include renal tubular acidosis, cystinuria, hyperparathyroidism, certain medications and some urinary tract infections.

Kidney stone facts

• A kidney stone is a hard, crystalline mineral material formed within the kidney or urinary tract.
• Nephrolithiasis is the medical term for kidney stones.
• One in every 20 people develop kidney stones at some point in their life.
• Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine.
• Dehydration is a major risk factor for kidney stone formation.
• Symptoms of a kidney stone include flank pain (the pain can be quite severe) and blood in the urine (hematuria).
• People with certain medical conditions, such as gout, and those who take certain medications or supplements are at risk for kidney stones.
• Diet and hereditary factors are also related to stone formation.
• Diagnosis of kidney stones is best accomplished using an ultrasound, intravenous pyleography (IVP), or a CT scan.
• Most kidney stones will pass through the ureter to the bladder on their own with time.
• Treatment includes pain-control medications and, in some cases, medications to facilitate the passage of urine.
• If needed, lithotripsy or surgical techniques may be used for stones which do not pass through the ureter to the bladder on their own.

Kidney Stone Treatment

Most kidney stones eventually pass from the kidney through the ureter and bladder and finally through the urethra on their own. However, treatment is often required for pain control from kidney stones as they pass. The consumption of ample fluids helps facilitate the passage of kidney stones, but even with plentiful fluid intake, most people require some type of medications for pain control.

Can  kidney stones be prevented?

Rather than having to undergo treatment, it is best to avoid kidney stones in the first place when possible. It can be especially helpful to drink more water, since low fluid intake and dehydration are major risk factors for kidney stone formation.

Depending on the cause of the kidney stones and an individual's medical history, changes in the diet or medications are sometimes recommended to decrease the likelihood of developing further kidney stones. If one has passed a stone, it can be particularly helpful to have it analyzed in a laboratory to determine the precise type of stone so specific prevention measures can be considered.

People who have a tendency to form calcium oxalate kidney stones may be advised to limit their consumption of foods high in oxalate, such as spinach, rhubarb, Swiss chard, beets, wheat germ, and peanuts. Also drinking lemon juice or lemonade may be helpful in preventing kidney stones.

Are home remedies effective for kidney stones?

For some people who have had many kidney stones, home care may be appropriate. When passing a kidney stone, drinking lots of fluid is important. In fact, this is the most important home care measure. Medications may help control the pain (as described previously). However, if it is the first time one has had symptoms suggestive of a kidney stone, it is important to see a doctor right away.