Kidney Stones

KIDNEY STONES

Kidney stones are common, affecting 0.2% of adults annually. Approximately 7% of men and 3% of women will develop a kidney stone in their lifetime. Men develop kidney stones 3 to 4 times more commonly than women, and this is thought to be due to females having higher levels of urinary citrate, which is a potent stone inhibitor.

Stones can occur at any age, but are most common between the ages of 20 – 40 years.

After having developed one kidney stone, there is a significant risk of recurrence.

Recurrence rates for kidney stones:

10% within 1 year
35% within 5 years
50% within 10 years

How did my stone form?

Most patients like to know why their kidney stone formed. There is still much debate on this topic, however there are two main causes, structural and metabolic. Structural causes include those conditions where there is impaired drainage of urine from the kidney such as PUJ obstruction, calyceal diverticula or medullary sponge kidney. Metabolic causes include diseases of the bowel and kidney, which result in high levels of calcium, oxalate or uric acid (a protein breakdown product) in the urine, which can lead to supersaturation of the urine (that is, insufficient water is available to dissolve these compounds). Different stone types may occur depending on which of these is elevated.

It is widely accepted that most stones begin life as a small plaque on the lining of the kidney, which forms a nidus for further stone to form around it (epitaxy), however stones can also form within the collecting ducts of the glomerulus (the tiny filters within the kidney) or within the broader collecting system of the kidney.

Large Stone within the Renal Pelvis

This photo, taken through a flexible pyeloscope, demonstrates a large stone within the renal pelvis

Renal colic

Kidney stones can present in a variety of ways such as blood in the urine (haematuria), urinary tract infections or pain. The most dramatic of these is renal colic, which occurs when a stone passes from the kidney into the ureter. This causes obstruction to the outflow of urine from the kidney, resulting in an increase in pressure and swelling within the kidney, which causes sudden and severe pain in the loin. This usually requires hospital admission and depending on the size and location of the stone, may require surgery.

Kidney stones are diagnosed using a detailed X-Ray or CT scan which will provide all the information required to determine the best treatment for your stone.

Stones may become impacted at three main locations within the ureter, corresponding to its narrowest points:

  1. Pyeloureteric junction (PUJ) – between the kidney and its outflow duct, the ureter
  2. At the level of the iliac blood vessels
  3. At the vesicoureteric junction (VUJ) – just as the ureter drains into the bladder

Kidneys In Situ

Kidneys In Situ - Anterior View

Which is the best treatment for my kidney stone?

The treatment of your kidney stones is determined by its size and position, and other factors including the degree of pain, your overall kidney function and the presence of infection.

The size of the stone helps predict the likelihood of the stone passing spontaneously. As a general rule, stones less than 4 mm in size have an excellent chance of passing by themselves and so intervention is only recommended in the presence of severe pain or infection.

Likelihood of spontaneous passage of a stone by stone size (within 1 month):

4 mm - 90%
5 mm - 50%
6 mm - 10%

If a stone does not pass spontaneously, or is not likely to, then treatment is recommended. Occasionally medicines may be offered to improve the chances of your stone passing spontaneously.

Ureteroscopy

Ureteric stones are usually treated by inserting a long narrow telescope (ureteroscope) through the lower urinary tract (urethra and bladder), up to the stone and fragmenting it with an energy source such as laser, as demonstrated in the diagram below.

Ureteroscopy

The stone fragments are then removed with a tiny basket and sent for analysis. If the stone cannot be retrieved, then a plastic drainage tube (stent) is left to bypass the stone and relieve the obstruction, with ureteroscopy delayed for 1-2 weeks.

Ureteroscopy is carried out as a day procedure in hospital without any incision and so recovery is usually rapid. If a stent is inserted you may notice some urinary frequency and bleeding (haematuria) but this is expected. The stent can be removed within 1-2 weeks in most cases. Ureteric stents should not be left inside longer than 3 months as they carry a risk of forming stone material around them (encrustation).

This technique can also be employed for stones which are still inside the kidney using longer flexible instruments (flexible pyeloscope).

Ureteroscopy by Dr Simon Bariol

Shock-wave lithotripsy

There are many other ways to treat stones within the kidney and ureter. Shock wave lithotripsy is a technique where the stone is fragmented through the skin using shock waves. There is less acute morbidity and pain associated with this procedure, however most studies show that the stones take a longer time to pass with this technique. There is also a potential long-term risk of hypertension (high blood pressure) and diabetes.

Shock-wave lithotripsyShock-wave lithotripsy

Shock-wave lithotripsy

Percutaneous nephrolithotomy

Percutaneous nephrolithotomy is a technique reserved for larger kidney stones which requires a small (2 cm) cut in the flank through which a broad telescope is passed into the kidney and the stone fragmented and removed.

Percutaneous nephrolithotomy

Percutaneous nephrolithotomy

This is a longer procedure and involves a 2-3 day stay in hospital. An external “nephrostomy” tube drains your the kidney through the skin for the first 24-48 hours, which is removed prior to your discharge home. There is a risk of infection with this procedure and so you will need to take antibiotics both before and after your operation for a short period of time. Owing to the considerable blood flow through the kidney, there is also a mild risk of bleeding, but rarely requiring blood transfusion.

Percutaneous Nephrolithotomy by Dr Simon Bariol

Other less common approaches to the kidney include laparoscopic (keyhole) and open surgery, but these are only performed in exceptional circumstances.

Dr Bariol will be happy to discuss your operation in detail at the time of your consultation.

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