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Urology Resources
Urinary Stone
Urinary stones are formed in the kidney from a combination of factors, like insufficient water intake, foods containing excess oxalates (tea, chocolates), and high purine (peanuts, red meat, soya beans, beer).
Symptoms
Most stones present with colicky loin to groin pain which is so painful that narcotic analgesia is often needed. This pain is due to the passage of the stone down the ureter resulting in increased pressure created within the kidney. There may be accompanying blood in the urine due to abrasion of the urinary tract lining. Prolonged blockage can lead to infection, especially in diabetics. If so, fever and painful urination become additional symptoms.
Diagnosis
X-rays are needed to confirm the site, size and shape of the stone. A quick screening test can be done with just a plain x-ray (KUB) together with ultrasound of the kidney / bladder. However, the limitation of this method is that some 10% of stones do not show up on the KUB because they are either small in size or do not contain enough calcium. Hence, x-rays using contrast injection (IVU) is the standard way of locating these stones. The disadvantage with IVU is that bowel preparation is needed, there is risk of contrast allergy and it takes an hour to do. Hence, nowadays, non-contrast CT scan is increasingly used to diagnose urinary stones with the advantage that it is fast to do, need no bowel preparation or injection of contrast material.
Management
Treatment depends on the size and site of the stone. Stones less than 5 mm can be managed conservatively because they are less likely to block the kidney when they pass down the ureter. Stones bigger than 5 mm tend to obstruct, and are managed by one of the following means:
- ESWL (Shock wave treatment)
A lithotripter machine is used to break the stones into tiny pieces using the technology of shock waves focused onto the stone. The stone is located by means of x-ray or ultrasound attached to the machine. This is an outpatient treatment that lasts 40 minutes or so, is safe and convenient. It can be used to treat stones in the kidney or ureter, although the best success rate is for kidney stones (>90%). Narcotic analgesia with/without sedation is given prior to treatment as the technique involves delivery of up to 4000 shocks before the stone can be adequately broken. It does not damage the kidney although some bleeding and swelling does occur. The disadvantages are that it is restricted to stones < 2 cm in size, and repeat sessions may be needed if the stone is very hard. The stone may also be hard to locate if there is overlying gas shadows at the time of treatment. - PCNL (Endoscopic treatment through kidney)
This is a minimally-invasive technique for large stones > 2 cm lodged in the kidney or upper ureter. It involves creating a tract into the kidney followed by insertion of a scope through which the stone is broken. The stone pieces are then extracted out via this track. This surgery has to be done under general anaesthesia under x-ray guidance and takes 2 to 3 hours. The hospital stay is at least 3 days because of the high bleeding rate caused by the kidney puncture. Also, some 3% of patients may develop a re-bleed due to an abnormal artery-vein connection that may occur 2 weeks post-treatment. In such an occurrence, readmission to hospital for radiographic intervention is needed. Despite the surgical risks, the advantage of PCNL over ESWL is the high success rate (>95%) achieved at a single session. - URS (Endoscopic treatment via the ureter)
This is endoscopic treatment using a mini-scope that is passed up the urethra into the bladder and up the ureter for stones lodged within the ureter. Using a laser or lithoclast (pneumatic device), direct contact is made on the stone. A wired basket can also be used to extract the stone pieces. It is done under general anesthesia as a day surgery case because the pain and bleeding is usually minor. Occasionally, a double-J stent may need to be inserted after the procedure if injury has occurred to the ureter wall. The success rate is highest for stones lodged in the lower ureter (>95%); the other advantage being the ureter opening is dilated by the scope to facilitate subsequent stone passage. This procedure usually takes 30 minutes.
