This kidney disease can affect the young as well as the elderly. With no treatment for the condition, Vanessa Leyland explains how its development can be slowed through maintaining a healthy blood pressure
The kidneys comprise a pair of organs, commonly about five inches long and three inches wide, located at the back of the abdominal cavity on either side of the spine. The left kidney is slightly higher and larger than its counterpart.
Their primary function is to filter blood. Blood travels into the kidneys via the renal artery, waste is excreted from it and then returns to the bloodstream; the waste and any excess water travel to the bladder as urine. Additionally, the kidneys balance bodily fluid content, adjust the level of minerals and chemicals, produce an enzyme called rennin - which helps control blood pressure - and activate vitamin D for strong bones.
A kidney has three layers: the glomeruli, which is packed full of capillaries; the renal medulla, which contains urine-forming tubules; and the central area where urine collects, which is known as the renal pelvis. These layers form the functional part of the kidney and are known as the nephron; each kidney has over one million nephrons.
There are two main types of polycystic kidney disease (PKD):
- Autosomnal dominant disease, which means one parent will have the condition already, is the most common form. The prevalence is one in 1,000 and symptoms do not usually develop until the age of 40. Kidney failure may develop eventually, leading to death.
- Autosomnal recessive disease, which appears in childhood, is quite rare and affects one in 10,000 babies; this form of the illness requires both parents to pass on the abnormal gene. Death occurs usually within a few years due to portal hypertension with liver and kidney failure.
PKD can also be non-inherited and can be derived from a chronic kidney problem, dialysis or old age.
The disease is characterised by multiple cysts that increase in size and number with age and the fluid-filled cysts give the kidney a honeycomb appearance. As the cysts increase in number and size they replace normal kidney tissue, making the kidneys larger and reducing their ability to function, which can then result in kidney failure. The kidneys can enlarge by three to four times their normal size.
Detection
Symptoms may take many years to develop: one of the first signs of PKD is pain in the back, sides or abdomen caused by the kidneys increasing in size due to the enlarged cysts, bleeding cysts or kidney stones; 50.5% of pain is musculoskeletal in origin. There may be blood in the urine, headaches and urinary tract infections. Raised blood pressure, or hypertension, is a common early symptom and, even though the kidneys may still be functioning normally, this may damage them further, though hypertensive medication will slow the deterioration down.
Babies with PKD can be identified at birth due to a swollen abdomen caused by the enlarged kidneys; the liver may also be involved. Where there is a family history of PKD, an ultrasound during pregnancy may detect the disease. In adults, where there is a family history of the disease, routine screening will identify it before any symptoms develop and a definitive diagnosis is provided by an intravenous pyelogram, computed tomography scan or ultrasound.
Keeping at bay
At present, there is no treatment for the disease but it is possible to slow its progression; blood pressure control is very important in reducing kidney damage, although failure will occur eventually. In seven out of 10 people with PKD, failure will happen by the age of 65. Dialysis, which replaces the renal function, or a transplant may then be performed.
It is important to reduce the amount of salt consumed, eat healthy foods, watch weight and exercise regularly to improve cardiovascular function. It is also important not to smoke.
Cysts on the liver will occur in 30% of people with PKD, which can also develop in the spleen, pancreas, ovary and other organs. In 10% of cases, berry aneurysms in the cerebral vessels may result in brain haemorrhage.
Facts and figures
- At present there is a clinical trial into a drug called Tolvaptan, which has shown to be effective in preventing the growth of cysts in rodents.
- If a parent has autosomnal dominant PKD there is a 50% chance their child will also have it.
- In the US, 12% of patients with end-stage renal disease will have PKD.
- The first documented case of PKD was Stefan Bathory, a king of Poland who lived from 1533 to 1588.
- The first dialysis took place in 100 AD in Roman baths, when people with a build-up of urea in their systems soaked in the baths to sweat out toxins.
- Wolfgang Amadeus Mozart is thought to have died from kidney failure
- Kidneys represent 0.5% of the body's total weight.
- A body's entire volume of blood is filtered through the kidneys 12 times a day.
- Vanessa Leyland is life and disability underwriter at Aegon Scottish Equitable.
Sources:
Swiss Re Lifeguide
www.PKDcharity.co.uk
www.bbc.co.uk
UNDERWRITING IMPLICATIONS
For underwriting purposes, the categories used are 'disease present' and 'positive family history only'.
When considering an application for life protection where the disease is present, the underwriter will request a general practitioner's report and will ask for results of all renal investigations, past and present. An underwriter will need to establish how well the kidneys are functioning and the stage of the disease. To determine this, the glomerular filtration rate (GFR) will need to be known. A GFR is a kidney function test that determines how much of the blood has been filtered through the kidney effectively; this is done by calculating the filter of a marker such as inulin, a fructose-derived substance that is not absorbed by the body but is filtered readily by the kidney.
The underwriter would look for a GFR that is greater than 50 and the blood pressure well controlled, with no further cardiovascular risk factors; uncontrolled hypertension accelerates the loss of kidney function and control is very important.
Where there is a family history of PKD with no disease present, it would be expected that the client has been investigated fully using a computed tomography (CT) scan or ultrasound.
Where a genetic test has been performed, the underwriter would take into account all appropriate industry legislation relating to the use of genetic testing results.
