Science & Technology in Action

11th Edition

Kidney stones and how to remove them

Boston Scientific

Kidney stones can often be shattered using a non-invasive procedure called shock wave lithotripsy. The shattered pieces are then eliminated naturally from the body. High energy sound waves are focussed on the stone for about an hour at the rate of about 1 pulse per second.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Kidneys
Pain is part of human consciousness and is an invaluable aid to survival. It tells us when something is wrong with our body. All pains are different; back pain, toothache, bruising or headache. There are even phantom pains where people who have had limbs amputated feel pain in the limb even although it is no longer there. One of the worst pains is that associated with kidney stones. It is described as being like getting stabbed with a knife, agonising or excruciating. However I think the best description is ‘exquisitely painful’ as it gives an indication of the uniqueness of the pain.

The Greek physician Hippocrates first described the symptoms of kidney stones in 400 BC as follows: 

 ‘an acute pain is felt in the kidney, the loins, the flank and the testis of the affected side. With the urine sand is passed; as the sand passes along the ureter, it causes severe pain which is relieved when it is expelled; then the same sufferings begin again.’

What are kidney stones? 
Kidney stones, sometimes called renal calculi, are lumps of hard, crystalline mineral material that form within the kidney or urinary tract. The medical term for having them is nephrolithiasis. About one in every 20 people will be affected at some time in their life usually between the ages of thirty to fifty. They are more common in Asians and Caucasians than in Africans, or African Americans. 

Causes of kidney stones
Kidney stones form for three main reasons:

The urine may contain more crystal-forming substances than the fluid in it can dissolve. 

The urine may lack the substances that prevent crystals from sticking together. 

In response to a urinary tract infection.

Dehydration is probably the most important risk factor for kidney stone formation. The two most likely causes of dehydration are taking lots of strenuous exercise or living in a hot climate and not drinking enough water. Dietary factors also play a part. For example people who take large doses of vitamin C, often in the belief that it will prevent disease, have a 20% higher risk of developing stones. Eating foods rich in oxalates such as rhubarb can also be a contributory factor.

A family history of kidney stones is also a significant risk factor, especially in this part of the world. People with certain medical conditions (e.g. gout), or those who take some medications, such as those used in chemotherapy, are also at an increased risk of developing stones.

Diagnosis 
Initial diagnosis is based on symptoms but this may be followed by 

X-ray, ultrasound scans, intravenous pyelogram (IVP) or even a CT scan to give a more detailed picture of the size, number and location of the stones. This is always carried out prior to surgical intervention.

True or False?

  1. Lithotripsy uses ultra-sound. false
  2. Most kidneys stones pass without treatment. true
  3. Analgesics relax muscles. false
  4. Dehydration is the most common cause of kidney stones. true
  5. Most kidney stones are calcium compounds. true
  6. Urinary tract infections always cause kidney stones. false
  7. Open surgery is the best treatment for most kidney stones. false
  8. Diueretics increase urine production which is more likely to cause stones. false
  9. X-rays are used to diagnose and locate kidney stones. true
  10. RIRS is slightly invasive. true
  11. ESWL can cause bruising in the area of the stone. true
  12. Lithotripsy can be used to help mend broken bones. true