KIDNEY STONES – RENAL CALCULI*
A kidney stone, also known as a renal calculus (from the Latin renes ‘kidneys’ and calculus ‘pebble’) is a solid concretion or crystal aggregation formed in the kidneys from dietary minerals in the urine. The kidneys filter the blood and remove the extra waste and water as urine. Many waste chemicals are in the urine. They can sometimes form crystals that clump together to make stones. Kidney stones are hard rock-like crystals of varying sizes and shapes. They can vary in size from as small as a grain of sand up to as big as a golf ball.
Classification of Kidney Stones
Urinary stones are typically classified by their Location:
· In the kidney - nephrolithiasis
· In the ureter - ureterolithiasis
· In the bladder – cystolithiasis.
They can also be classified by their Chemical Composition:
· Calcium containing
· Uric acid
The most common type of kidney stones (up to 80%) are those formed from calcium, generally combined with oxalate or phosphate. Struvite (ammonium magnesium phosphate) stones (10-15%) are caused by a urine infection and are often quite large and are also known as 'infection stones'. Uric acid stones (5-10%) tend to be softer than other forms of kidney stones. Cysteine stones are very rare and hereditary. They look more like crystals than stones.
Frequency of Kidney Stones
Kidney stones are one of the most common disorders of the urinary tract. About 4-8% of Australians suffer from kidney stones at some time. The lifetime risk of developing kidney stones is 1 in 10 for Australian men and 1 in 35 for women.
After having one kidney stone, the chance of getting a second one is 4-10% each year. About 30-50% of people with a first kidney stone will get a second one within five years and then the risk declines. (www.kidney.org.au)
What Happens Once a Stone has Formed in the Kidney?
Kidney stones typically leave the body by passage in the urine stream, and many stones are formed and passed without causing symptoms. If stones grow to sufficient size, usually at least 3 millimetres in diameter, they can cause obstruction of the ureter. Urethral obstruction creates back pressure on the kidney, resulting in distension and dilation of the renal pelvis and calyces, as well as spasm of the ureter. The resultant pain, which can be extreme and excruciating, is called renal colic: it is felt in the flank (the area between the ribs and the hip), lower abdomen and groin. This pain is the result of spasm of the muscles in the ureter, as they try to expel the stone into the bladder.
Renal colic typically comes in waves lasting up to 60 minutes. It is often associated with nausea, vomiting, fever, haematuria (blood in the urine) and painful urination.
Diagnosis of Kidney Stones
The diagnosis of kidney stones is made on the basis of information obtained from the history, physical examination, urinalysis, radiographic studies and laboratory tests. Ultrasound and blood tests may also aid in the diagnosis.
A traditional radiograph of the abdomen that includes the kidneys, ureters and bladder will show calcium-containing stones, since they are relatively radiodense. Calcium phosphate stones have the greatest density, followed by calcium oxalate and ammonium magnesium phosphate stones. Cysteine stones are only faintly radiodense, while uric acid stones are entirely translucent.
All stones are detectable by CT scans.
Where a CT scan in unavailable, an intravenous pyelogram may be performed. This involves an intravenous injection of a contrast agent excreted via the kidney and thus the X-rays are able to demonstrate the stone(s).
Ultrasound imaging of the kidneys can sometimes be useful as it gives details about the presence of hydronephrosis, suggesting that the stone is blocking the outflow of the urine.
Laboratory investigations typically carried out include:
· Microscopic examination of the urine
· Urine culture
· Full blood count
· Renal function tests
· 24 hour urine collection
· Collection of stones and their analysis.
Analysis of the stone is very useful, so if you pass a stone, try to collect it since analysis of it could help to decide the correct treatment for prevention of recurrence.
What Causes Kidney Stones?
A stone can form when substances such as calcium, oxalate, cystine or uric acid are at high levels in the urine. This can be the result of an underlying medical condition causing high levels of these chemicals in the body. However, stones can also form if these chemicals are at normal levels.
When the urine becomes supersaturated (when the urine solvent contains more solutes than it can hold in solution) with one or more crystal-forming substances, a seed crystal may form through the process of nucleation. A seed crystal can grow and aggregate into an organised mass, the kidney stone.
Supersaturation of the urine is pH-dependent. For example: at a pH of 7.0 (neutral), the solubility of uric acid in urine is 158 mg/100 ml. Reducing the pH to 5.0 (acidic) decreases the solubility of uric acid to less than 8 mg/100 ml. Thus, the formation of uric acid stones requires a combination of hyperuricosuria (high urine uric acid levels) and a low urine pH.
Supersaturation of the urine is a necessary condition for the development of any kidney stone. Calcium-based stones have a more complex aetiology. Normal urine contains chelating agents, such as citrate, that inhibit the nucleation, growth and aggregation of calcium contains crystals. Sufficient dietary intake of magnesium and citrate inhibits the formation of calcium oxalate and calcium phosphate stones. Magnesium's efficiency in subduing stone formation and growth is dose-dependent.
Risk Factors for the Formation of Kidney Stones
· Dehydration from low fluid intake is a major factor in stone formation.
· High dietary intake of animal protein, sodium, refined sugars and oxalate increase the risk of kidney stone formation.
· Kidney stones can result from an underlying metabolic condition such as distal renal tubular acidosis, hyperparathyroidism or primary hyperoxaluria.
· It has been suggested that genetics can lead to a predisposition to kidney stones. But the main reason that kidney stones seem to run in families is more due to learned behaviour (diet) within the family than genetics.
· As stated earlier, cystine stones, which are rare, have a genetic basis.
Treatment of Kidney Stones
Most kidney stones can be treated without surgery. 90% of stones will pass within 3-6 weeks. In this situation, the only treatment required is pain relief. Pain can be so severe that hospitalisation may be required and very strong painkillers may be needed.
However, if a stone does not pass and blocks the urine flow or causes bleeding or an infection, then it may need to be removed.
New surgical techniques include:
- Extracorporeal Shock-Wave Lithotripsy. Ultrasound waves are used to break the kidney stones into smaller pieces, which can pass out with the urine. It is used for stones less than 2cm in size.
- Percutaneous Nephrolithotomy. A small cut is made in your back and a special instrument is used to remove the kidney stone.
- Endoscope Removal. An instrument is inserted into the urethra, passed into the bladder then up the ureter to where the stone is located. The stone is then removed or broken up so it can pass more easily.
How to Prevent Kidney Stones
- A healthy diet is crucial. See my September 2005 newsletter Acid / Alkali Balance - The Ideal Diet and my March 2008 newsletter Foods for Health.
- It is essential to avoid dehydration, especially if you have had one stone already. It is suggested that the volume of urine should be at, or above, two litres a day.
- Avoid drinking coffee, switch to tea. Green tea reduces the chances of developing kidney stones.
- Get quick and proper treatment of urinary infections.
- Citrus juices may reduce the risk of some stones, particularly orange, grapefruit and cranberry.
- Reducing salt lowers the risk of calcium containing stones.
- Avoid drinks containing phosphoric acid (carbonated drinks such as cola).
- Stevia as an artificial sweetener is safe to replace refined sugars (see my March 2010 newsletter Stevia).
- Avoid supplement protein powders.
- Maintain a calcium intake of about 1000mg a day.
- Magnesium citrate, a B vitamin complex with extra vitamin B6, with a healthy diet will protect against the development of large stones. Harvard researchers found that 180mg of magnesium and 10mg of B6 taken daily can actually prevent 92.3% of kidney stones. Other studies show huge reductions with magnesium alone at 500mg a day (see my December 2008 newsletter Magnesium).
- It is suggested that a drink containing equal parts of apple cider vinegar and honey (two teaspoons each in 200ml water) taken daily will reduce kidney stone formation.
- The following herbs have been shown to help in the prevention of kidney stones: Nettle leaf, Hydrangea root, Gravel root, Marshmallow root, Horsetail herb, Uva ursi, Corn silk and Goldenrod flowers.
(These points on prevention come from www.naturalnews.com)
When a kidney stone causes no symptoms, watchful waiting is a valid option. For symptomatic stones, pain control is usually the first measure, using medications such as non-steroidal anti-inflammatory drugs or opioids. If the stone is not passed, some form of surgical intervention would be indicated.
As in all conditions, prevention is the best way forward. Many of the suggestions outlined above, as preventatives for kidney stones, are positive for general health.
*Copyright 2015: The Huntly Centre.
Disclaimer: All material in the huntlycentre.com.au website is for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.
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