Kidney Stones (Nephrolithiasis)

kidney stones

Kidney stones (Nephrolithiasis) are a hard deposits made from chemicals in the urine. These chemicals are essentially minerals and salts that are formed inside kidneys. Urine has several waste substances dissolved in it. When there is excessive waste in inadequate liquid, crystals begin to form. The concentrated urine allows minerals to crystallize. The crystals join with other elements and form a solid that will get larger to form a specific kidney stone. Mostly these chemicals are excreted in the urine by people who drink adequate amount of fluids. These fluids wash these chemicals preventing formation of stones. The stone-forming chemicals are calcium, oxalate, urate, cystine, xanthine, and phosphate.

Kidney stones can be formed in children as young as 5 years. The main causes of stones in children are inadequate water intake and high consumption of salty foods like potato chips and French fries.

Generally, kidney stones do not cause any permanent damage if recognized in the  early stages. The size of stone may vary from as small as grain of sand to as big as pebble. The tiny stones may move out of the body in urine without any pain. The stones that do not move cause back pressure of urine in urinary tract and cause pain. The patients with kidney stone may experience severe pain while passing the stone. Mostly such patients may require plenty of water to drink and take medication to relieve pain. In few patients these stones may lodge in the urinary tract and may lead to urinary infection or other complications. These cases may require surgical intervention to remove the stones.   

Symptoms:

A kidney stone may remain silent without any symptoms until it moves around within the kidney or ureter (tube joining kidney with urinary bladder). The patient may experience following symptoms: 

  • Severe pain in the side of the abdomen and back, below the ribs
  • Pain radiating to the lower abdomen and groin. Pain may shift to different location based on the movement of the stone.
  • Waxing and waning pain that fluctuates in intensity
  • Pain during urination
  • Red or brown urine suggestive of blood in the urine,
  • Cloudy or foul-smelling urine
  • Nausea and vomiting
  • Increased frequency of urination.
  • Passing small amount of urine
  • Fever and chills if associated with urinary infection

Causes:

There is no definite single cause of kidney stone but several factors may increase the risk of crystallization and stone formation. The urine in such patients contain crystal forming substances like calcium, oxalate and uric acid. Moreover, the fluid content in the urine in much less in proportion to the crystals. Certain types of stones are more prone to run in families due to genetic influence.

Types of Kidney Stones:

These are several types of kidney stones and knowing these would help  determine the cause and may give clues on how to reduce the risk of getting more kidney stones. The types of kidney stones include:

  1. Calcium Stones: Most kidney stones are calcium stones, usually in the form of calcium oxalate. Oxalate is found in food and is also made daily by the 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. It may also be associated with certain migraine headaches or with taking certain seizure medications, such as topiramate.
  2. Struvite stones. Struvite stones are formed in response to urinary infections.  These stones can grow quickly and become quite large, sometimes with few symptoms or little warning.
  3. Uric acid stones. Uric acid stones can form in people who don’t drink enough fluids and take high-protein diet. These stones are also seen in people with high uric acid in blood and suffering from gout. The genetic factors also increase the risk of uric acid stones. The formation of these types of stones tend to run in families. 
  4. Cystine stones. These stones form in people with a hereditary disorder that causes the kidneys to excrete too much of certain amino acids (cystinuria). These are relatively uncommon types.

Risk Factors: 

  1. Family or personal history: The person with the family history of kidney stones is more likely to develop stones. If someone  already had one or more kidney stones, there is an increased risk of developing another. Those who have developed stone has 50% higher chance of developing another stone within 5-7 years.
  2.  Dehydration: Not drinking enough water each day can increase the risk of kidney stones. People who live in warm climates and those who sweat a lot may be at higher risk than others.
  3. Diets: Eating a protein rich diet, high sodium (salt) and sugar (mainly fructose in table sugar) may increase the risk of some types of kidney stones. This is especially true with a high-sodium diet.
  4. Obesity: High body mass index (BMI), large waist size and weight gain have been linked to an increased risk of kidney stones.
  5. Digestive diseases and surgery: Gastric bypass surgery, inflammatory bowel disease or chronic diarrhoea can cause changes in the digestive process, increasing the levels of stone-forming substances in the urine.
  6. Medical conditions: Diseases and conditions that may increase the risk of kidney stones include kidney disease, cystinuria, hyperparathyroidism, certain medications and urinary tract infections

Diagnosis:

The diagnosis of kidney stones are done with medical history, clinical examination and imaging tests. The commonest diagnostic tool is KUB X ray i.e. X ray of kidney-ureter-bladder. KUB will show the size and the position of stone. KUB is also done before and after the treatment to monitor the response of treatment.

High resolution CT is done to know the exact size and shape of the stone. Currently CT is a preferred option for diagnosis of kidney stone. In few cases a special type of X-ray (Intravenous Pyelography) is also done after injecting a dye.

Besides imaging tests, patient may undergo certain blood and urine tests to assess the overall health of the kidney.

Prevention of Kidney Stones:

Drinking adequate amount of fluid keep urine less concentrated with wastes products. The colour of the urine should be light yellow to clear if person is well hydrated. Water is the best fluid to take for dilution of urine. People should drink about 12 or more glasses of water a day. In summers and those who exercise water intake should be increased. Sugar should be taken in limited quantities.  Animal proteins makes urine more acidic which increases the risk of kidney stones. Various packaged food and beverages should be avoided due high content of salt.   

In obese persons, reduction of weight with balanced diet help reduce the risk of stone formation.

Treatment:

Treatment of kidney stones are aimed at high intake of water and fluids. In case of pain, the medication for pain relief is prescribed. Doctor may also prescribed medication to reduce the acidic nature of urine.

In case of larger stone or if there is an evidence of urinary infection, doctor may recommend to go for surgical removal. There is a non-invasive procedure to remove kidney stone known as shock wave lithotripsy (SWL). This technique uses high energy sound waves to break the stones into small fragments that are passed through urine. There is another procedure known as ureteroscopy where an endoscope is inserted into ureter to dislodge the stone. 

In highly complicated cases of kidney stones nephrolithotomy or nephro lithotripsy can be advised to remove these stones.   

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