Alistair Cameron-Strange is a Consultant Urologist at The Prince of Wales Hospitals and The Sutherland Hospital in Sydney and is an expert in the minimally invasive treatments of simple and complex urinary stones.
As Director of The NSW Lithotripsy Centre, he has a cumulative experience of more than 10000 kidney stone treatments. He specializes in Urinary Stone Disease using the most modern State-of- the-Art Laser Technology, Extracorporeal Shockwave Lithotripsy and Keyhole surgery to treat both simple and complex urinary stones. He is supported by an excellent team of Uroradiologists and Laser trained theatre nursing staff.
With the latest advances in minimally invasive surgery for urinary stones, conventional open surgery is seldom required these days. Minimally invasive procedures are advantageous because they involve a shorter hospital stay, less pain and faster recovery.
After treating kidney stones it is important to consider the preventative aspects of stone disease to try to determine the cause of the stone and which metabolic disorder may have led to the formation of the stone. This is fairly complex but there are guidelines which all stone formers should follow.
Stone formers may pass stones at different times in their lives without any symptoms. The best outcome for an episode of renal colic is that the stone passes spontaneously without the need for surgical intervention. Intervention however is indicated for unremitting pain; failure of the stone to pass because it is too large or jammed in the ureter causing back pressure on the kidney; and infection.
The best way to remove a stone is whole as fragments are not left behind. Residual fragments can cause stone recurrence. Where this is not possible, an energy source will need to be applied to fragment the stone to removeable and passable fragments.
The energy sources we use are Laser, SWL (shockwave lithotripsy), and electrohydraulic lithotripsy. The use of these modalities varies with respect to the size, site and density of the stone and will be discussed below.
It should be appreciated that residual stone fragments do not always pass and may remain in the kidney to form the nucleus for future stone recurrence.
The cause of kidney stones is complex but the supersaturation theory is easily understood. Calcium is normally dissolved in the urine aided by the presence of stone inhibitors. If there is an excessive accumulation of calcium in the urine, calcium salts aggregate to form stone particles which, in time, will grow to form a stone. The absence of stone inhibitors in the urine makes this more likely. Uric acid can similarly form urinary stones, particularly in those with gout.
Dehydration will result in the concentration of calcium or uric acid in the urine and for this reason we see more kidney stones in hot climates and more stones in summer than in winter.
Patients with recurrent urinary tract infections may form infection stones which can fill the hollow part of the kidney forming a staghorn stone.
Kidney stone disease is becoming recognized as a systemic disease indicative of an adverse metabolic environment. There is a definite association between kidney stones, obesity, diabetes, hypertension, stroke and heart attack. Obesity and diabetes promote stone formation - uric acid stones are more common in diabetic patients while obesity increases the urinary excretion of promoters of crystallization and urine acidity, and contributes to an increase in calcium oxalate stones.
Kidney stones may present with pain, backache, infection, blood in the urine or as an incidental finding. Large kidney stones may block urine drainage from the kidney and reduce the function of that kidney. The typical pain of acute renal colic in the male is from loin to groin to testicle.
The definitive diagnosis that you have a kidney stone is its presence on an Xray. The most accurate way of finding a stone is by performing a CT scan although a plain Xray or urinary tract ultrasound may be helpful with the diagnosis.
There are three things to be done.
Renal colic at its worst is the most severe pain that one can experience. In this setting an intravenous narcotic and anti-emetic will settle the pain. Some patients may only need a strong oral analgesic
Renal colic dictates an urgent visit to the ER for pain relief.
Ureteric Stones <5mm in diameter have a >85% chance of passing without intervention. Tamsulosin will often help with the passage of small calculi which may pass without the patient's knowledge.
As the diameter of the stone increases, so does the rate of spontaneous passage decrease. More recent work has shown that the length of the stone is a more accurate predictor that a stone will pass than the diameter. Most ureteric stones >7mm will require intervention. Ureteral stones that will not pass are best treated by passing a telescope into the ureter through the bladder, and disintegrating the stone with a laser or electrohydraulic energy source. As an alternative the initial placement of an internal ureteral JJ stent through the bladder will relieve the pain but the stone will need to be treated at a later date.
Surgical therapies for stones within the kidney <2cm in size.
For larger stones percutaneous nephrolithotomy (PCN) is performed. Under general anaesthetic an access track is created through the loin into the kidney. This permits access by a telescope to the kidney. The stones are fragmented with ultrasound or electrohydraulic lithotripsy and the fragments removed with forceps.In this way the kidney can be totally cleared of all stone material. If there are residual fragments after this treatment they can later be treated with laser or SWL.
Advantages - total stone clearance possible, 3 day hospital stay, quick return to work.
Disadvantages - an invasive procedure. Low risk of kidney damage and damage to adjacent organs. Blood transfusion in <3% of patients.
It is seldom that one has to resort to open surgery nowadays. The one indication for this is a very large staghorn stone with a large peripheral stone burden.
There are four main types of stones. Calcium oxalate/phosphate (by far the commonest), uric acid stones, infection stones and cystine stones. The treatment for each of these differs but in general terms a stone former should
When kidney stones are of great concern:
In these situations one has to drain the kidney with a nephrostomy tube placed through the skin into the hollow part of the kidney, as well as treat the infection. Such a condition may be life threatening and necessitate intensive care treatment. Once the fever has settled then the stone can be treated as described.
Stone analysis will determine the stone composition which will determine the strategy to prevent recurrence.
In addition other tests will be performed to assess the levels of calcium, phosphate and uric acid in the blood and urine. The parathyroid hormone PTH which maintains calcium balance in the body will also be measured. If the PTH is elevated it could indicate overactivity within the parathyroid glands in the neck. If this is the case surgery will be needed to remove the affected parathyroid/s of which there are four.
Some, but few patients have diet as a cause of their stones, others leak too much calcium into the urine and there are those on a normal diet who simply absorb too much calcium from a normal diet.
Uric acid stones are the only stones that can be dissolved, provided they do not have a calcium coating which makes them insoluble. These stones can be dissolved with ural (sodium bicarbonate) taken orally. In addition it may be necessary to take a drug - Allopurinol - to reduce the serum uric acid levels. Uric acid stone dissolution is successful in approximately 40% of patients.
Infection stones occur in those with recurrent urinary infections and can fill and silently destroy a kidney. The bacteria responsible for the infection cause a chemical alteration of the urine which promotes the growth of a stone. It is important to control or prevent recurrence of urinary infections.
Cystine stones are due to an inherited metabolic disorder. These stones are an ongoing problem as the recurrence rate is high and the medication used for prevention not very successful.
A JJ stent is an internal drainage tube which drains urine from the kidney to the bladder. They are called JJ stents as there is a J curl at each end to hold it in position.
JJ stents are placed under a general anaesthetic under various circumstances
JJ stents can cause irritative symptoms of urinary frequency, bladder pain during or after voiding, back pain during voiding, abdominal pain on the side of the stent and blood in the urine. Some or all of these symptoms occur in > 50% of patients. Others have no symptoms at all.
JJ stents should not be left in situ for more than 3 months and can be removed under a local anaesthetic. If pain is an issue treatment with tamsulosin and an analgesic may provide relief. After removal of the stent relief is instant.