Clinic Location & Map

#09-40 Mt Elizabeth Novena Specialist Centre
(located within Mt Elizabeth Novena Hospital)
38 Irrawaddy Road
Singapore 329563

Phone: +65 6235 1180
Fax: +65 668 41310
Emergency: +65 6535 8833

Clinic Hours

Monday - Friday 9:00am - 5:30pm
Saturday 9:00am -12:30pm
Sunday / Public Holiday Closed

Urinary Stone

Picture of Urinary Stone

Urinary stones are formed in the kidney from a combination of factors, like insufficient water intake, high carbohydrate-low fibre diet, excess oxalates intake (tea, chocolates) and high purine foods (peanuts, red meat, soya beans, beer).


Most stones present with colicky loin to groin pain which is so painful that strong narcotic injections are invariably needed. This pain is due to the high pressures created in the blocked kidney as the stone passes down. There is usually blood in the urine too due to ‘abrasion’ of the urinary tract lining. Prolonged blockage will lead to infection, especially in diabetics. If infection occurs, fever, persistent loin pain and painful, frequent urination develops. If the obstruction is prolonged, the kidney is at risk of permanent damage (atrophy).


Picture of contrast injection (IVU)

Fig 1. IVU requires injection of contrast to confirm the stone location

Picture of CT Scan

Fig 2. CT scan is fast to do and can even show small radiolucent stones.

Xrays are needed to confirm the site, size and shape of the stone. A quick screening test is a plain xray (KUB) combined with ultrasound of the kidney / bladder. However, the limitation is that some 10% of stones do not show up on KUB because they are either too small or do not contain enough calcium. Also, gas and stool shadows can obscure tiny stones. Hence, xrays using contrast injection (IVU) is the standard way of locating these stones [Fig 1]. The disadvantage with IVU is that bowel preparation is needed, risk of contrast allergy and it takes 1 hour to do. Hence, non-contrast CT scan is increasingly used to diagnose urinary stones with the advantage that it is fast to perform, needs no bowel preparation nor injection of contrast. Even small, non-calcium containing stones < 5 mm can be imaged [Fig 2].


Treatment depends on the size and site of the stone. Stones < 5 mm can be managed conservatively because they are small enough to they pass out of the ureter. Stones > 5 mm tend to obstruct, and are managed by one of the following means:

1. ESWL (Shock wave lithotripsy)[Fig 3]

A lithotripter is a machine that stones into tiny pieces using the technology of focused shock waves. The stone is located by means of xray or ultrasound attached to the machine. This is a safe outpatient treatment lasting about 1 hour. It can be used to treat stones lodged in the kidney or ureter, the highest success rate being for kidney stones (> 90%). The patient is awake but will still need intravenous analgesics as the technique involves delivery of at least 2000 to 4000 shocks before the stone can be broken. It does not damage the kidney although the kidney can get swollen or develop a blood clot (haematoma). Bloody urine is expected in the following few days. The limitation with ESWL is that it is not suitable for grossly obese patients. The other disadvantage is it is restricted to stones < 2 cm and repeat sessions may be required if the stone is very hard in consistency; such hard stones cannot be predicted from the xrays. Technical limitations are difficulty in localizing the stone in obese patients, if the stone overlies the sacrum bone and if there is too much bowel gas overlying the stone during the procedure.

Picture of ESWL treatmeny

Fig 3. ESWL treatment to break stones < 2 cm size lodged in the kidney or ureter

2. PCNL (Endoscopic puncture through the kidney)[Fig 4].

This is a minimally-invasive technique for stones > 2 cm located in the kidney or upper ureter. It involves creating a puncture tract into the kidney to access the stone by means of a nephroscope. The stone is broken either with a laser, ultrasonic or pneumatic device and extracted out via this scope. The whole procedure is done under xray guidance and takes between 2 to 3 hours to do. Hospital stay is at least 3 days. About 3% of patients may develop a re-bleed due to an abnormal artery-vein malformation. If so, readmission to hospital for radiographic intervention is needed. Despite the surgical risks, the advantage of PCNL over ESWL is that big stones can be cleared with a high success rate (>95%) at a single session.

Picture of PCNL

Fig 4. PCNL involves a puncture into the kidney to break big stones > 2 cm size

Picture of URS

Fig 5. Ureteroscopy to break stones lodged in the ureter

3. URS (Endoscopic treatment via the ureter)[Fig 5].

This endoscopic procedure involves a mini-scope that is passed up the urethra into the bladder and up the ureter. It is suitable for stones < 1 cm lodged in the ureter. A laser or pneumatic probe is placed onto the stone to break it. A wired basket can also be used to extract the stone pieces. The procedure takes 30 mins to 1 hour and can be done as a day case because the pain and bleeding is usually minor. Some cases may require a double-J stent to be inserted into the kidney especially if injury has occurred to the ureter wall. URS is ideal for stones lodged in the lower ureter ( success rate > 95%). The other advantage with this method is that the ureter opening can be dilated to facilitate passage of the stone fragments.