Tamilnadu Urological Research Centre

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The following are the frequently asked questions answered by

Dr. C. Chinnaswami, M.S., M.Ch, FRCS.,
TNURC, Kidney Stone Clinic, Chennai.

1. Has the incidence of urinary stones increased?

It is true, incidence of stones in the kidney and ureter has increased in recent times, whereas the bladder stones that were common in children are not to be seen now a day.

Possible causes for the increase could be due to changes in life style, contributed by

  • Increase in salt intake
  • Increased intake of animal proteins.
  • Low intake of fibers and alkalis
  • Inadequate water intake.
  • Use of food preservatives.

2. What chemical abnormalities are known to cause kidney stones?

The chemical abnormalities relate to the type of stones that form in the kidneys. These four types of stones and the chemical abnormalities that cause them are:

Calcium Stones: people who form this type of stone either have too much of one type of three chemicals in their urine, or not enough of another. In particular, they have either too much calcium, oxalate, or urate in their urine, or too little citrate. Eating too much salt may cause too much calcium to stay in the urine A few patients will have kidney stones from overproduction of the calcium controlling hormone, parathormone. Drinking milk does not cause kidney stones.

Struvite Stones: Chronic infection of the urine generally causes these stones. The bacteria responsible for the infection cause a chemical alteration of urine, which leads to this type of stone.

Cystine Stones: These stones form because of an inborn error of metabolism of Alanine. Abnormal amount of cystine accumulates in the body which leads to stone formation. Usually, other family members have the same condition.

Knowing the type of kidney stone is important to prescribing treatment to prevent further stone formation.

3. Where do urinary stones formed and where are they found?

It is commonly seen in the kidney and ureters. Bladder stones are common in children and in elderly persons. Most of the stones are formed in the minute tubules of the kidney and pass down. It may stay in the kidney and grow bigger or it may stay in the ureter. Majority of the stones can easily slip down to the bladder and pass out in natural way. It may get lodged at various levels and grow larger.

4. How do the stones form in urinary tract?

Kidney excretes out large quantity of minerals and end products of metabolism and maintains the internal equilibrium of the body. The minerals are in a super saturated but soluble forms. When the balance is upset either by increase in concentration of the salts (as seen in dehydration due to sweating or diarrhea or poor intake of fluids) or turbulence of urinary stream or presence of materials like bacteria, dead papillae (tissue in kidney) tumor or foreign bodies on which the salts gets deposited and stone starts to grow.

Urinary stone has been compared to ferroconcrete in structure. It is not formed of pure crystals as in blue metal. There is a scaffolding formed by colloids, dead bacteria, tumor tissue or foreign body (like steel rods in concrete) and salts in the urine oxalate, uric acid, triple phosphate or cystine crystalline materials fill in the space between the scaffolds.

Some crystals grow well in alkaline urine whereas some stones grow only in acidic urine. Many stones grow rapidly in stagnant urine, which gets collected above obstructed urinary tract.

5. What are the symptoms of urinary stones?

A) Pain is the commonest presenting symptoms. It may be severe, shooting from the back towards the thigh or genitalia. This happens when the stone moves from the kidney to the ureter. It is called renal colic or ureteric colic.

Stones, which are inside the kidney, may not cause severe pain but dull aching pain may be felt in the kidney area. It is a perplexing but surprising fact that big stones may remain and grow silently whereas small stones can cause severe pain when they move about.

B) Haematuria – passing blood in the urine is another common feature of urinary stones. This blood in the urine could be quite obvious to the naked eye or only a microscope could detect it. Severity or quantum blood is not dependent on the size of the stone.

C) Fever may be associated with pain in stone disease. It points to the presence of infection.

D) Tenderness – this term is used to denote presence of pain on touching (palpating) various areas of the abdomen. This is to be distinguished from pain mentioned earlier. Presence of tenderness denotes infection.

When the last two symptoms fever and tenderness are noted the stone problem should be considered serious and treated promptly.

E) Swelling – it is unusual to see any significant swelling in simple stone disease. It may be seen in stones of long duration.

F) Nausea or Vomiting – may be associated with severe pain. It may also be a sign of kidney failure associated with some kidney stones.

6. How are stones in the ureter treated?

Stones, which are seen above the level of the pelvic bone, can be successfully treated by ESWL. At times the stone can be pushed into the kidney endoscopically and treated by ESWL. This is called Push & Bang! it may be advantageous to leave a ‘Double J’ stent (bent tube) inside the urinary tract while treating impacted and larger ureteric stones.

Stones, which are lying over the pelvic bone, are not suitable for ESWL treatment. Similarly, results of ESWL treatment for stones in the lower part of the ureter are not satisfactory. In such situations, the stones are visualized by ureteroscope and treated by basketing or by Intra Corporeal Lithotripsy using Laser, Lithoclast or Ultrasound. All these procedures are considered invasive and will require anesthesia and hospitalization for a few days.

Very big stones in the ureter are still better treated by open surgery. Retroperitonoscopy is a recent ‘key hole surgery’ which is suitable for large stones in the ureter. Laproscopy is another alternate method.

7. How are stones in urinary bladder treated?

Most of the stones in the bladder can be treated endoscopically (without open operation) ‘Vesico Lithotripsy’. The stone will be visualized by Endoscopes and stone can be broken to bits mechanically by Lithotrite or by special equipments like Lithoclast, Ultrasound, Electro hydraulic lithotripsy or Laser. However, it is very important to treat any predisposing cause like prostatic hypertrophy, stricture of the urethra, etc.

8. Do urinary stones reoccur?

Yes. About 10-15% of persons get recurrence of urinary stones.

9. What is the role of diet in the management of urinary stones?

A diet low in animal protein, sodium and normal calcium has been found to be highly efficient in preventing reoccurrence.

Calcium restriction has deleterious effect on stone reoccurrence rate.

There is Inverse relationship shown between intestinal absorption of oxalate and daily calcium intake. Urinary calcium excretion depends more on the dietary acid load than on the calcium intake itself.

The new trend is NORMALISATION OF DIETARY HABITS and not restriction of any single nutritional constituent. Dietary restriction of calcium for stone prevention is NOT RECOMMENDED.

In the small group of patients having ABSORPTIVE HYPERCALCIURIA Type I alone require moderate calcium restriction.

10. What do you recommend to avoid stone formation?


  • Fluid intake
  • Balanced – drinking advice to have urine out put of 2.0 – 3.0 (4) per day
  • Depending on the occupation, leisure activity, general atmospheric temperature, etc.
  • Neutral beverages – to be encouraged.
  • Maintain urine specific gravity, less than 1010
  • Distribute intake evenly, adequate intake at nights.


  • Balanced Diet
  • Rich in vegetable fiber
  • Rich in alkaline potassium
  • Normal calcium content (1 to 1.2g)
  • Restricted sodium chloride (4-5g/day)
  • Restricted animal protein 0.8 to 1g/kg body ut./day
  • Limited sugar and fat content
  • Limited oxalate content


  • BMI between 18 and 25 kg/m2
  • Stress limitation
  • Adequate physical activity
  • Balancing of excessive fluid loss.

Approximately 15% of stone formers need additional drugs for preventing stone reoccurrence. An elaborate metabolize evaluation is necessary to guide the urologist for specific medication.

11. When does one need open (cutting) surgery?

Open surgery for urinary stones is obsolete. It is rarely necessary in complex staghorn stones or when operation is necessary to correct obstruction in urinary tract (eg. Hydronephrosis – where pyeloplasty is necessary) as when Kidney is to removed (due to total loss of function or for life threatening source of infection).

12. Who are the persons likely to form recurrent stones?

  • Children and teen agers
  • When there is obstruction in urinary pathway
  • Presence of infection or foreign body in the urinary tract
  • Gout and increase in uric acid level in blood.
  • Genetically induced stone formers
    • Renal Tubular Acidosis
    • Primary Hyper Oxaluria
    • Cystinuria
  • Disorders of calcium metabolism, e.g. Hyper Parathyoidism.

13. What precaution should one take to prevent stone recurrence?

Normalization of body weight and cardio-vascular risk factors, sufficient physical activity, balanced nutrition and sufficient circadian fluid intake are the appropriate measures to prevent recurrence of calculi formation.

Low intake of animal protein and sodium chloride and high intake of alkaline potassium are the dietary measures to be adopted. Calcium restriction is not advisable (except in absorptive Hyper calciuria)

14. How much fluid should be consumed per day by a stone patient?

This will depend on the climate, physical activity of the person, food habits and other factors. If the urine specific gravity is maintained around 1010 crystallization of stone forming elements will be minimized. The aim should be to maintain urinary output of about 2 to 2.5 liters per day. This may not be possible for patients in cardiac failure or when kidney function is not adequate.

15. What are the food articles to be avoided?

This depends on the type of stone formed

  • High oxalate foods (to be avoided in Hyper oxaluria)
  • Green beans, Beats, Celery, Green Onions
  • Leek, Leafy greens, Cocra, Chocolate, Black tea, Berries – gooseberry, black berries,
  • Strawberry, currants, Orange peel, Lemon peel,
  • Dried figs, Nuts – peanut, butter, Toffee.
  • High Purine foods - to be avoided by patients, with uric acid stones.
  • Organ meats, Shellfish, Meat-beef, Pork,
  • Lamb, Poultry, Fish, Meat extracts,
  • Vegetables: Asparagus, cauliflower, peas, mushrooms, kidney beans, Lentils.

16. Is there is a relationship between diabetes and stone formation?

Probably there is no direct relationship. At times Diabetics develop a condition known as ‘papillary necrosis’. In this condition small bit of collecting tubules sloughs off and present as a Nidus for stone formation.

17. Can urinary stones cause Hypertension?

Hypertension is associated with many diseases of the kidneys. Stones may not cause Hypertension directly. But pathological changes in the kidney caused by the stone can cause Hypertension.

It is common to see elevation of Blood pressure during episodes of acute pain caused by the stone.

18. Can stones be associated with cancer?

Stones lodged in the kidney or urinary bladder can cause changes in the lining membranes of these organs. These changes called metaplasia can ultimately lead to cancer.

Sometimes calcium deposition resembling stone may be seen on the surface of some cancerous tumors.

19. Can stones cause kidney failure?

Kidney failure occurs when both the kidneys function below the optimum level. If one kidney functions normally and the other kidney is badly affected (or even if removed) there will not be any significant symptom of kidney failure.

In stone disease kidney failure can occur if both the kidneys are affected badly, or when there is obstruction to both the ureters by stones. Symptoms of kidney failure (obstructiveanuria) will be seen when a single functioning kidney is obstructed or seriously diseased.

20. What is Stag-Horn calculus? How is it treated?

Fairly large stone in a kidney occupying large part of the kidney pelvis and branching into one or more of the calyces is usually referred as ‘Stag-Horn’ calculus. Very often it is associated with urinary infection. Most of the Stag-Horn calculi are treated by the PCNL, at times a combinatination of ESWL & PCNL or so called Sandwich treatment where ESWL followed by PCNL and again ESWL for residual fragments may be necessary.

Complex Stag-Horn calculi with mush room like projection into minor calyces may require open surgery.

21. What is meant by ‘clinically insignificant calculus?

Calculi which are less than 5mm (smaller than the diameter of ureter) are not likely to cause any harm. They are passed in urine in course of time without any specific treatment. There stones are usually referred as ‘clinically insignificant’ calculus. Trying to remove them may prove to be futrile and may even cause more trouble than the stone can cause.

22. Are stone formation familial?

Most of the stones are not familial. Rare forms of stones such as cystine stones occur in families. Renal Tubular acidosis and Primary Hyperoxaluria are the other familiar conditions associated with stone disease.

23. Is there a ‘role’ for Banana stem (Vazhithandu) in stone management?

Banana stem is an age old home remedy for urinary stone. Effectiveness is not proved. But there is no harm. Diet rich in vegetable fibres reduces calcium absorption and will be useful in calcium stone formers. But taking ‘Banana stem’ as juice can cause gastric irritation to many patients. The stem can be cooked and taken as ‘Salad’ or ‘Poriyal’.

24. What is the role of Tomatoes in stone disease?

Traditionally tomatoes are blamed as the cause of stone disease. This is not proven scientifically. It contains more oxalate than many vegetables. Hence taking large quantity of Tomatoes as juice, salad or ketchup can cause increased oxalate absorption. Similarly many vegetables with small seeds like Brinjal and Bhendi (ladies finger) were also blamed for stone formation. Moderate quantity of these vegetables could cause no harm.

25. Should stone formers avoid milk totally?

Not necessary. As a matter of fact, calcium stone formers should consume at least minimum quantity of calcium in their food. If there is total restriction of calcium in the diet there will be mobilization of calcium from the bones into the blood stream and this may be harmful. About 250-300ml of milk (any form) is permitted for stone formers.