Dr Palaniappan Sundaram, Associate Consultant, Urology Service, Sengkang General Hospital, a member of the SingHealth group, answers frequently asked questions on urinary stones. 

1. How are urinary stones formed?

Urinary stones form when urine contains a high concentration of chemicals such as calcium, oxalate, phosphate and uric acid, and too little of the substances such as citrate and magnesium that stop stone formation.

2. What causes urinary stones?

Urinary stones are a common condition, affecting 10 to 12 per cent of the adult population. The most common cause of urinary stones is not drinking enough water. The golden rule is that two to three litres should be drunk every day – or enough to result in two litres of urine. So drink whatever amount is necessary to make that volume. If not enough water is taken in, urine becomes concentrated, allowing chemicals to crystallise and urinary stones to form.

3. Does diet contribute to urinary stones?

Apart from not drinking enough water, people with certain conditions that increase calcium levels in the body, such as hypothyroidism, also tend to get urinary stones. That is not to say that people prone to kidney stones should avoid calcium consumption, as large studies have shown that restricting calcium intake leads to stone formation. Moderate calcium intake, and lower salt and animal protein intake, is fine. Oxalate, which is present in most foods, however, is harder to restrict.

4. How are urinary stones treated?

Most small stones are passed out in the urine, but larger ones can be treated in several ways:

  • Extracorporeal shock wave lithotripsy, done as an outpatient procedure, uses shock waves to break urinary stones into fragments, which are then passed out in the urine over the next few days. This non-invasive and safe procedure, however, may require more than one session.
  • Percutaneous nephrolithotripsy is a minimally invasive keyhole operation. A small hole is made in the body to allow a scope to pass into the kidney. The urinary stone is broken up and removed through this passage.
  • Uretero-renoscopy involves passing a small scope through the urethra and bladder into the ureters and kidneys. The urinary stone is then broken up and removed.

Read on to learn about a study conducted to determine if drinking a type of sparkling mineral water could prevent urinary stones.

Ref: N18