When substances found in the urine become highly concentrated, a stone-like solid material is formed in the kidney. This is known as ‘kidney stone’ or ‘renal calculi’ or the medical term for kidney stone is ‘NEPHROLITHIASIS’. This stone may travel down the urinary tract or it may stay in the kidney. These stones vary in size and composition. Small kidney stones may pass out of the urinary tract without causing much pain and discomfort, but some large stones require surgery.
Signs and Symptoms of Kidney Stones
- Severe pain and discomfort in the abdomen or lower back
- Pain or burning sensation while urinating
- Presence of blood in the urine
- Persistent need to urinate but passing out small amount of urine
- Nausea and vomiting (rare)
- Fever and chills in presence of infection (rare, but due to infection if any)
Causes of Kidney Stones
- Hypercalciuria: It is a medical condition in which large amount of calcium is excreted out of the body via urine. Research has shown that people with Hypercalciuria are at a higher risk of developing kidney stones and this is because of two main reasons- increased saturation state of the urinary calcium salts such as calcium phosphate and calcium oxalate and decrease in the activity of inhibitors that may protect against kidney stone formation such as citrates.
- Family history of renal stones: Individuals with a family history of developing kidney stones are at a higher risk as compared to those without a family history.
- Gout: Excess uric acid (a waste product) gets accumulated in the blood and forms crystals in the joints and kidney. These crystals get deposited in the kidneys and can become large stones, which may further lead to pain and discomfort and may permanently cause damage to the kidneys.
- Distal renal tubular acidosis: In this, kidneys fail to excrete acids into the urine. This in turn causes an individual’s blood to remain too acidic. One of the complications of distal renal tubular acidosis is kidney stones.
- Dehydration: A very common cause of kidney stones is dehydration or drinking less fluid. Chronic dehydration may lead to production of urine with higher concentration of waste materials and minerals. This may further lead to the formation of crystals, which may build up in the kidneys to become stones.
- Secondary hyperparathyroidism: In this condition, parathyroid glands become overactive resulting in excess production of parathyroid hormone. This in turn causes Hypercalciuria, which further causes formation of kidney stones.
- Hyperoxaluria: It is a disorder characterized by high levels of oxalate in the urine. Individuals with such a disorder are at an increased risk of developing calcium oxalate kidney stones.
- Chronic inflammatory bowel disease: Malabsorption associated with chronic inflammatory bowel disease causes increased oxalate absorption by increasing oxalate solubility and by reducing citrate excretion. Furthermore, the volume of urine decreases, urine becomes more concentrated and the pH of urine falls thus leading to kidney stone formation.
Types of kidney stones
|Types of Stones||Composition of Stone|
|Calcium stones||Calcium Oxalate and Calcium Phosphate|
|Uric acid stones||Uric Acid Crystals|
|Struvite stones||Triple combination of magnesium, phosphate and ammonium|
|Cystine stones||Cystine precipitation|
- Calcium stones: It occurs in two major forms- calcium oxalate and calcium phosphate. Calcium stones are the most common type of kidney stones. Out of the two, calcium oxalate stones are more common as compared to calcium phosphate stones. Calcium oxalate crystals are formed through combining calcium with oxalic acid. These stones may be formed due to systemic disease (such as a bowel disease), a diet rich in calcium, certain medications, genetics or other kidney problems.
- Uric acid stones: These stones are made out of crystals of uric acid, which is a breakdown product of DNA and RNA. These stones can be orange or red in color because they absorb hemoglobin breakdown products. Uric acid crystals when passed in the urine, may give it an orange-red color. They can be caused by eating too much animal protein particularly red meat.
- Struvite stones: These are made out of a triple combination of magnesium, phosphate and ammonium. Certain bacteria get entry into the body and lead to the formation of such crystals, which further leads to the formation of Struvite stones. These stones can become huge and their bacteria may cause injury to the kidneys. Furthermore, bacteria may enter into the blood stream and may cause sepsis. Individuals with kidney infection are at a greater risk of developing Struvite stones.
- Cystine stones: These stones are rare and may occur only in those individuals with inherited kidney disorder/disease called ‘cystinuria’. In such a disorder, abnormal amounts of four amino acids, out of which one is Cystine that enters in the urine. This leads to the formation of crystals and kidney stones. Cystine stones may become very large in size and they can block the kidney tubules and cause further damage.
Diagnosis of Kidney Stones
- Urine testing: This test helps an individual to know the amount of stone-forming minerals that he/she is excreting in the urine. Presence or absence of infection can also be detected.
- Blood test: Blood test may help reveal biochemical problems that can lead to kidney stone formation such as elevated calcium level in the blood.
- Ultrasonography: It helps detecting and measuring the kidney stones.
- CT scans: They can help detect the presence of stones, their locations and their size.
Drinking at least 2.5 to 3 liters of fluids per day is the thumb rule in the treatment of kidney stones. The leading cause of kidney stone is concentrated urine. Therefore, more amounts of fluids are required to dilute the urine. However, fluids with high sugar content such as sugar-sweetened beverages, packaged fruit juices and sugar syrups should be restricted. Besides drinking water some other fluids may also help in the treatment of kidney stone, these include.
- Lemon juice: Citrate or citric acid from lemons prevents the formation of crystals. One can easily add some fresh lemon juice to their regular water to add some citrate to their diet.
- Barley water: It is a very well known diuretic, which increases the urine output.
- Coconut water: it is rich in potassium, helps in alkalizing urine, and prevents formation of kidney stones.
Fruits: Blueberries or cherries
Vegetables: Bell peppers and squash
High Fiber Foods: Oats, Beans, root vegetables and psyllium husk
Here are some important information for dietary restriction for preventing kidney stones and re-formation of kidney stones (renal calculi).
Restricted Food Lists
|Food Category||Restricted Foods|
|Vegetables||Beets, Spinach, Rhubarb, Collard, Turnip Greens|
|Salt Amount||More than 2500 mg per day is restricted|
|Nuts & Seeds||Peanuts|
|Pulses||Whole Bengal, Gram (CHANA), Horse Gram (Kulthi Dal) +, Rajma, Soya Beans|
|Cereals & Grains||Wheat bran, ragi|
|Spices & Herbs||Asparagus|
|Dairy Products||All dairy products.|
|Animal Foods||All animal food including Organ Meats – Brains, Kidneys, Liver, meat extracts – gravy, broth, bouillon, consomme, Other – herring, mussels, scallops, caviar or anchovies|
|Drinks & Beverage||Colas, Soft drinks or carbonated drinks, pre-packed fruit juice|
|Others||Chocolate, Custard apple, Sweet breads, Corn syrup|
+ Kulthi (horse gram) is contraindicated in Kidney Stones formed of Uric Acid Crystals or if uric acid level is elevated in the blood.
Limit sodium intake
Individuals with calcium oxalate stones need to cut down on their sodium intake. High sodium intake further increases the calcium excretion in the urine and increases the risk of stone formation. Therefore, it is advisable to restrict sodium intake up to 2500 milligrams per day. Such individuals strictly need to cut down their sodium intake during the course of treatment. Foods with high sodium content, which strictly need to be avoided, include-
- Packaged ketchups and chutneys
- Sauces and dressings
- Processed meat such as bacon, sausages and ham
- Bakery products such as breads, loaf, croissants, puffs, pizza bread and burger buns
- Salted nuts
- Savory snacks
- Frozen meals
- Ready-to-eat food items
- Canned vegetables
- Baked beans
- Dried fish
- Salted butter
- Restaurant foods
Tip: Develop a habit of reading the food label before purchasing any food product. A food label is a powerful tool, which helps individuals to know the presence of certain ingredients and their amounts. Reading a food label can be of great use for individuals with calcium oxalate stones as they can know the amount of sodium present in the food product and purchase accordingly. A food label may not always have the word ‘salt’ on it. Look out for words with prefix ‘sodium’ such as
- Sodium chloride
- Sodium benzoate
- Sodium hydroxide
- Sodium bicarbonate and so on
Do not overdo on calcium restriction
Individuals with calcium oxalate stones may require a moderate calcium restriction of 800 milligrams per day. However, diet with very high calcium content (2000 milligrams per day) need to be reduced. Severe calcium restriction or complete elimination of calcium form the diet without restricting oxalate intake will leave too much intestinal oxalate unbound and this will make them easily available for absorption. When this occurs, urinary oxalate levels rise and oxalates are 15-20 times stronger in promoting kidney stone formation. Therefore, limiting dietary oxalates becomes necessary when calcium intake is reduced.
Restrict animal proteins
Individuals with uric acid stones need to restrict animal proteins (except dairy products) such as red meat, processed meat and shellfish. These animal proteins increase the formation of uric acid in the urine and increase the risk of developing uric acid stones. However one serving (100 grams or 2 medium pieces) of lean meat such as chicken or fish can be consumed 2 to 3 times per week.
Restrict intake of strong tea and coffee
Strong or black tea and coffee are high in oxalates, which may further increase the risk of kidney stone formation. Therefore, individuals with calcium oxalate stone can consume a light tea or coffee but they strictly need to restrict intake of strong tea or strong coffee. The recommendation for tea and coffee drinkers is to drink moderate amount of tea or coffee (2 cups per day) with milk.
Current research has shown a positive link between obesity and increased risk of kidney stone formation. People who are overweight and obese with high waist circumference should lose weight in order to reduce the risk. Obesity is linked with increased intake of refined sugars, low fluid intake, and high intake of calcium, oxalate and purine rich foods. All these factors increase the risk of kidney stones formation. Therefore, following a healthy diet with high intake of whole grains, fruits, vegetables and lean meat will help in weight loss and further decrease the risk associated with obesity.
Avoid vitamin C supplements
Research has showed that individuals who take vitamin C supplements are at increased risk of developing calcium oxalate kidney stones. Vitamin C is excreted out of the body in the form of oxalate. Therefore, vitamin C supplements should be restricted without restricting dietary sources of vitamin C.
Avoid soft drinks and colas
Soft drinks and colas with phosphoric acid should be avoided due to their urine acidifying effect.
Oxalate content of different foods
|Food items||Oxalate content (milligrams)||Serving size|
|Spinach, cooked||750||½ cup|
|Spinach, frozen||600||½ cup|
|Beet greens||916||½ cup|
|Beets, cooked||675||½ cup|
|Chard, Swiss chard, leaves, cooked||660||½ cup|
|Turnip greens, cooked||110||½ cup|
|Collard greens, cooked||70||½ cup|
|Kale, cooked||125||½ cup|
|Potato, cooked||64||1 medium|
|Sweet potato, cooked||140||½ cup|
|Carrots, cooked||45||½ cup|
|Cocoa, dry||250||1/3 cup|
|Unsweetened chocolate||91||30 grams|
|Lady finger||145||7-8 pods|
|Wheat germ||67||¼ cup|
Purine content of different foods
When foods with high purine content are consumed, the production of uric acid in the body increases. Therefore, people with uric acid stones should restrict the following foods (high and moderate purine content)-
|Food items||Total purine in mg uric acid/100 grams|
|Organ meat (liver heart, brain, spleen)||450-550|
|Beef, muscles only||133|
|Bean, seed, white, dry||128|
|Bean, soya, seed, dry||190|
Calcium content of different foods
|Food items||Calcium content (milligrams)/100 grams|
|Roots and tubers||10-15|
|Tapioca, dry chips||91|
|Green gram, split||150|
|Bengal gram, whole||202|
Adopt plant-based diet and avoid animal foods including dairy products.
Sample Menu Plan
|Option 1: 1 bowl fiber rich cereal grain with vegetables OR||–|
|Option 2: 1 vegetable sandwich with 2 slices multigrain or whole wheat bread OR||Tomatoes and capsicum can be added to the sandwich after removing the seeds carefully (for individuals with calcium oxalate stones)|
|Option 3: 2 slices of wholegrain or multigrain bread with vegetable hummus||–|
|Option 1: 1 glass coconut water (if non-diabetic)||This will increase the urine volume|
|Option 2: 1 cup vegetable juice + 1 serving of fiber rich cereal grain||–|
|1 bowl salad (no tomato, capsicum and spinach) + 2 serving whole grain cereals + 1 serving tofu||–|
|1 bowl soup (no tomato soup)||Include more of vegetable soups, but do not consume tomato soup|
|1 portion split DAL + 2 Chapatti||–|
|1 glass lemon water||This will increase the urine volume|
|1 bowl salad (no tomato, capsicum and spinach) + 2 serving whole grain cereals||Do not add salad dressings to salad as they have high sodium content.|
|1 bowl soup (no tomato soup) + 1 serving tofu||–|
|1 portion split DAL + 1 Chapatti||–|