Disease of the month: Polycystic kidney disease

This genetic illness affects about one in 800 people in the UK. Mary Randell explains how advisers can offer cover for it

We shall begin with a quick anatomy lesson. The two kidneys lie to the sides of the upper abdomen, behind the intestines. Each one is bean shaped and about the size of an orange.

The kidneys clear waste materials and maintain the correct balance of fluids and chemicals in the body.

The renal artery, which carries blood to each kidney, divides into many tiny blood vessels or capillaries throughout the kidney. In the outer part of the kidney, these vessels form structures called glomeruli.

A glomerulus acts like a filter and allows waste products, water and salt to pass from the blood into a tiny channel called a tubule, while keeping blood cells and protein in the bloodstream.

Each glomerulus and tubule is called a nephron. There are about one million nephrons in each kidney.

As the water, salts and waste products pass along the tubule, there is a complex adjustment of the content, allowing some water and salts to be absorbed back into the bloodstream, depending on the current level of water and salt in your blood.

Tiny blood vessels next to each tubule enable this fine adjustment of the transfer of water and salts between the tubules and the blood.

The liquid that remains is called urine, which then passes down a tube called a ureter, which goes from each kidney to the bladder. Urine is stored in the bladder until it is passed out through the urethra.

The cleaned, filtered blood from each kidney is collected and carried in the renal vein back to the heart.

CAUSE OF PKD

Polycystic kidney disease (PKD) is a genetic disorder caused by one or more genes functioning abnormally.

Autosomal dominant disease (ADPKD), sometimes known as adult polycystic kidney disease, is the most common form and arises from one faulty gene (either ADPKD 1 or ADPKD 2) being inherited from one affected parent.

Autosomal recessive disease (ARPKD) is much rarer and occurs when a child inherits two abnormal genes – one from each parent.

ARPKD is a much more serious condition and unfortunately, many children will die at birth or shortly afterwards. For our purposes, we will focus on ADPKD.

ADPKD affects about one in 800 people in the UK, with men and women both equally affected. For each individual with PKD, there is a 50-50 chance that the faulty gene will be inherited by any children they may have.

As the name suggests, the disease is characterised by multiple (poly) fluid filled cysts developing in both kidneys.

Over time, the cysts will grow in size and number (sometimes to several hundred), taking over the healthy tissue and preventing normal filtering of blood. This then results in a decline and finally failure of renal function.

PKD develops very slowly and problems usually don’t occur until adulthood. In a few cases, an individual can have ADPKD without ever developing symptoms or problems. In most cases, symptoms appear sometime between the ages of 30 and 50.