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Kidney Stones: Causes and treatments

Pain, General | February 23, 2015 | Author: The Super Pharmacist

general, Pain

Kidney Stones: Causes and treatments

Kidneys are an important part of the body. In addition to urine production, they play a role in balancing acid levels. They also contribute to the maintenance of normal blood pressure by regulating the concentrations of electrolytes and salts in the body. Injuries or diseases affecting these organs may result in a significant effect on normal function and life quality, and a considerable burden on healthcare resources.

A common renal disorder is urolithiasis, more often referred to as kidney stones. These are most often crystalline structures of oxalate, a calcium-rich mineral. They are thought to originate in plaques of calcium phosphate that may build up on renal papillae (the 'tops' of renal pyramids). This plaque results in the formation of small, pebble-like stones, which may remain in the kidney or pass into the ureter. Plaque formation is thought to be related to hypercalciuria, or a high concentration of calcium in the urine. Other types of kidney stone may be formed from other molecules, including cysteine, a component of many proteins.

The Kidney

The kidney is an organ that filters the fluids in the body for useful compounds and molecules, and separates it from any waste, which is expelled from it into the bladder for excretion.

The KidneyIn other words, it forms urine as a result of processing the blood that is pumped through it. There are two kidneys (normally) present in the body, located in the rear of the lower abdomen to either side of the spine. The central part of the kidneys is made up of a number of short tubes, which meet to form the ureter, or the tube connecting a kidney to the bladder. A number of pyramid-shaped structures surround these tubes in a fan-like pattern. The pyramids are separated by the renal cortex.

These structures are surrounded by a complex network of blood vessels, and all of this is enclosed in a tough capsule-like structure. The complete organ somewhat resembles a bean that curves around the renal pelvis as it joins the ureter. The renal artery and vein also enter the kidney at this point, where they subdivide into the network of small vessels mentioned above. These traverse the nephrons, in which urine is formed. 

The formation of kidney stones

The formation of kidney stones may be linked to a number of factors, including:

A diet high in sugar or sodium chloride (salt): Sodium in particular may cause an imbalance in the biological mechanisms that regulate the normal calcium levels in the body, thus forcing more calcium into the kidneys. The presence of kidney stones has been found to be associated with the increased risk of bone fractures, (which may indicate calcium deficiency or the inability to integrate calcium into bone) particularly in older and middle-aged women.

Genetic factors: A genetic disorder that results in abnormally high levels of vitamin D may be associated with stone formation. This disorder may result in hypercalcaemia (excessive circulating calcium) which may in turn lead to the build-up of calcium in the kidneys. This also suggests a possible role of excessive dietary calcium in kidney stone formation. In addition, a family history of kidney stones may affect the probability of their development.

Dehydration: Inadequate water intake may be associated with the increased risk of kidney stone formation.

Increased bodyweight

Cystinuria, or high concentrations of cysteine in the urine. This may be due to a high dietary intake of protein, or certain medical conditions.

Symptoms of Kidney Stones

Kidney stones may cause symptoms that affect the normal activity and quality of life for those affected. These may include:

  • Pain when urinating
  • Urinary abnormalities, such as needing to urinate more frequently
  • Cloudy, red or brown urine
  • Pain in the region of the kidneys, which may radiate into the abdomen
  • Fever and/or chills (this is due to infection, which may accompany kidney stones)

Kidney stones are typically measured in length. They may reach 20 millimetres or more in size. A patient may have one or more kidney stones at a time. A recent study of 97 adult patients found that, for patients with large stones (or multiple stones equivalent to one measuring 20mm), each 1mm increase in size over 20mm was associated with a 20% increase in the risk of developing chronic kidney disease.

Treatments for Kidney Stones

Shock-wave Lithotripsy

Treatments for Kidney StonesThis is a procedure in which stones are broken up, usually by sonication (i.e. sound waves that disrupt the structure of a kidney stone).

Shock-wave lithotripsy is a popular method to treat this condition, and is regarded as effective and safe by many medical authorities and researchers. The main advantage of this procedure is that it may be done from outside the body, (i.e. it is extracorporeal) thus avoiding the need for surgery.

Surgery

There are several types of surgery available to remove kidney stones. These procedures are recommended for stones of a length exceeding 20mm by the European Association of Urology. (Stones of 20mm or less may be treated with one of the alternative treatments also listed her). The most prominent forms of surgery include:

Percutaneous nephrolithotomy (PNL): This is stone removal or destruction done through a small puncture wound above the ureter and kidney in the lower abdomen rather than through the bladder. A needle is passed into the renal pelvis through this incision to locate the stone. A review of ten studies compared these techniques, including newer types of 'micro' and 'mini' forms of percutaneous nephrolithotomy (which are designed to further reduce surgical invasion). Standard PNL was found to be superior in terms of stone removal. However, RIRS was associated with lower rates of complications than PNL, and appeared to have improved stone-free rates compared to both mini- and micro-PNL. In addition, mini- and micro-PNL appear to be linked to reduced efficacy and increased mortality. A recent study of 40 patients who received PNL reported immediate relief from pain following the procedure and improvements in quality of life that persisted for a year afterward.

Retrograde intrarenal surgery (RIRS):

IRetrograde intrarenal surgery (RIRS)n this procedure, an endoscope (camera probe) is inserted through the urethra (the tube leading out of the bladder) and extended through the bladder to reach a stone in the ureter or kidney. The stone may be then broken up using an ultrasound probe or laser. Alternatively, the stone may be removed with a thin for-cep.

Flexible Ureterorenoscopy: Shock-wave lithotripsy and surgery to remove stones are often less suitable for patients with a high body mass index (e.g. those who are obese or morbidly obese). In these cases, a procedure involving the insertion of a small, thin camera probe into the ureter and/or kidney (i.e. ureterorenoscopy) to aid excision or disruption of a stone may be more successful. A clinical trial compared the efficacy of this technique in 188 people of normal weight and 87 obese patients. The success and morbidity of ureterorenoscopy was statistically similar for both groups. However, the outcomes of ureterorenoscopy may be affected by the size of the stone to be removed.

If a patient wishes to avoid these levels of intervention, they may choose to pass the stone through the bladder and urethra themselves. Smaller, asymptomatic stones may be passed spontaneously, with or without medical supervision. The U.S. National Health and Nutrition Examination Survey found that, of its participants with a history of kidney stones, 22.4% of these had passed three or more.

A patient choosing to pass a stone themselves may be advised to drink plenty of fluids while waiting for the stone to move out of the ureter. Alternatively, drugs (adrenergeric alpha-blockers) may be used to enhance passage, if the stone is located in the ureter near the bladder. This process may also involve regular consultation with a doctor or urologist, which may include yearly imaging of the stone to assess movement, growth and the probability of passing it. Stone size may affect this; for example, an 8mm stone has an approximate 20% chance of being passed. Waiting for unassisted passage may have disadvantages; for example, there may be a need for the increased use of pain-killing drugs while trying to pass a symptomatic stone. A study of the treatment preferences of 101 kidney stone patients found that those who had passed a significantly large stone previously were more likely to choose surgery rather than repeat this experience.

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