A kidney stone is a solid mass made up of tiny crystals. Stones can form when urine contains too much of certain substances. These substances can create small crystals that become stones. The stones take weeks or months to form.
Causes/ Risk Factor of kidney stones
There are many causes of kidney stones and it is unusual to have just one causative factor.
The main reasons for forming stones are:
- Kidney stones are found in 2-3% of people and 0.5% of people present each year with an acute episode of pain due to stones; the rate has been rising steadily since the start of the 20th century
- Men are more commonly affected than women until after the age of 50 when the sex distribution becomes equal
- At age 70, a person has a lifetime risk of 1 in 8 for forming a stone
- Whether stones form is governed by both intrinsic (heredity, age & sex) and extrinsic factors (geography, climate, water intake & diet)
- Poor fluid intake combined with a low fiber, high protein western diet containing a lot of refined sugar increases the risk of forming stones
- Recurrence rates for stones are high (20% at 5 years, 35% at 10 years & 70% at 20 years)
- There is an association with "metabolic syndrome" (Syndrome X)
In most patients, more than one of the groups above is involved in stone formation. In patients with idiopathic stones, these are usually made of calcium oxalate and recurrence of these stones is common.
Warning symptoms and signs of kidney stones
- Anatomical (structural) abnormalities (inherited or acquired)
- Excess stone-forming substances in the urine
- Lack of stone inhibitors in the urine
- Chronic Infection in the urine (mostly in post-menopausal women)
- Idiopathic (i.e. no reason identified in 5-10%)
The patient may not have symptoms until the stones move down the tubes (ureters) through which urine empties into the bladder. When this happens, the stones can block the flow of urine out of the kidneys.
The main symptom is severe pain that starts suddenly and may go away suddenly:
Whilst kidney stones may cause pain in the loin with radiation down into the groin, there are many other causes for such pain. These include problems with the back and spine as well as a number of other non-urological conditions. The only way to find the cause of the patient’s symptoms is to have further investigations
- Abdominal pain
- Back pain
- Groin pain
- Testicle pain
- Abnormal urine color
- Blood in the urine
This will normally include some or all of the following:
- A full clinical history including asking the patient about their diet, time spent in a hot dry climate, fluid intake and whether there is a family history of stones
- A physical examination including assessment of the abdomen, measurement of blood pressure
- General blood tests to measure kidney function, liver function, blood sugar, uric acid, calcium, phosphorus and to check the blood cells for anemia or other problems
- Urine tests for blood (90% of patients with a stone have a trace of blood in the urine)
- Urine tests for pH (acidity)
- Urine test for infection.
- Urine test to measure a chemical called cystine.
- 24-hour urine collections will also be arranged for more detailed chemical analysis for patients who are young (less than 30), have a family history of stones or have had stones within the previous 5 years
- Examination of the stone to determine the type
- CT scan imaging is the best way to diagnose stones as almost all stones show up on a CT scan.
- Other imaging tests Abdominal/kidney MRI, Abdominal x-rays, Intravenous pyelogram (IVP), Kidney ultrasound and Retrograde pyelogram can also identify kidney stones
Treatments Options For Kidney Stones
Small stones in the kidney or ureter, which are causing no problems, can be managed expectantly and may pass spontaneously. Active treatment is usually recommended for larger stones or stones which are causing problems
- Patients will normally be given specific advice about changes to their diet and fluid intake which will reduce the risk of further stone formation.
- There is some evidence that stone inhibitor levels (especially citrate) can be increased by drinking fresh lemon juice in water and that this reduces the levels of stone-forming chemicals in the urine.
- There is no need to restrict calcium (dairy) intake and installing a water softener is not helpful in preventing further stones.
- Avoid grapefruit juice and vitamin C supplements, which can increase the risk of forming stones.
It may be possible to dissolve certain less common types of stone Further advice about specific medical treatment may be suggested once the patient’s stone has been analyzed chemically.
- Thiazide diuretics (water pills) and other drugs may be used to reduce the calcium levels in your urine.
- Allopurinol (for uric acid stones)
- Antibiotics (for stones caused by infection. Antibiotics will be prescribed before stone treatment and may need to be continued after surgery)
- Phosphate solutions
- Urinary alkalinization (for uric acid stones)
- Sodium bicarbonate or sodium citrate
- Penicillamine therapy (for cystine stones)
Small, symptomless stones in the kidney can be monitored by regular checks with an abdominal X-ray. Stones of a similar size in the ureter (less than 5mm diameter) may also pass by themselves but active treatment will normally be recommended if the stone shows no sign of passage after 2-3 weeks.
- Alpha blockers. For stones in the ureter, a muscle-relaxant drug (usually an alpha-blocker, normally used to relieve prostate symptoms) can help to speed the passage of a stone by specifically relaxing the muscle of the ureter.
- Anti-spasm drugs (e.g.Buscopan, Probanthine) are still used by some doctors but have little effect on symptoms and do not speed stone passage.
Extracorporeal shockwave lithotripsy - ESWL
ESWL cannot be performed safely in: -
- This is the most common treatment recommended for stones in the kidneys and for stones less than 1cm diameter in the upper ureter (the drainage tube between kidney & bladder).
- 90% of stones will clear with one treatment but some patients may need re-treatment or even surgical intervention.
- If a stone has not responded to two successive treatments with ESWL, it is unlikely to fragment with further treatments and other removal methods will then be considered.
- pregnant women
- patients on Warfarin or other blood-thinning agents (e.g. dipyridamole, clopidogrel)
- patients whose weight exceeds 300lb.
The main reasons for recommending surgical treatment are:
The best treatment for any stone is a combination of all the techniques described below, tailored to the specific needs of individual patients and their stone(s).
- a stone which is too large to pass spontaneously (greater than 5mm diameter)
- a stone which is causing obstruction to urine drainage
- a stone which is causing (or has been caused by) infection
- a stone which has formed as a result of an anatomical (structural) problem which also needs correction at the same time as stone treatment
- failure of simple painkillers to control symptoms
- Percutaneous (keyhole) surgery
Percutaneous nephrolithotomy (PCNL) is used for large stones in the kidney (e.g. "staghorn" stones) or large stones in the upper ureter, either as a primary measure or if ESWL has failed.
- Flexible uretero-renoscopy
Smaller stones in the kidney can be extracted or fragmented with a laser, using a flexible telescope passed through the bladder. A temporary stent may need to be inserted after this procedure.
- Rigid ureteroscopy
Stones in the ureter can be extracted or fragmented with a laser using a rigid telescope passed through the bladder. A temporary stent may need to be inserted after this procedure.
- Insertion of a ureteric stent
In the emergency situation, when a stone is blocking the ureter completely, it may be necessary to insert a stent under general anesthetic to relieve the blockage so that definitive treatment can be performed at a later stage.
- Percutaneous nephrostomy
If there is a blockage with severe infection due to a stone in the ureter, a drainage tube may be inserted into the kidney under local anesthetic to relieve the problem; this will be followed, at a later date, by definitive treatment of the stone.
Complications of Kidney Stones
- Decrease or loss of function in the affected kidney
- Kidney damage, scarring
- Obstruction of the ureter (acute unilateral obstructive uropathy)
- Recurrence of stones
- Urinary tract infection
Prevention of kidney stones
- Drink plenty of fluids (6 - 8 glasses of water per day) to produce enough urine.
- Depending on the type of stone, certain medications or diet changes may be required to prevent the stones from coming back.