By June Cheong

Recent court cases involving organ trading have focused attention on human kidneys.

Bean-shaped, these two vital organs located below the ribcage at the back of the waist are each as big as a human fist.

Think of them as 'border patrol' - keeping the homeland (your body) safe and maintaining the status quo.

Dr Titus Lau, senior consultant nephrologist at the department of medicine, National University Hospital, said: 'The kidneys' major function is to maintain a stable internal environment to allow us to live in a relatively hostile and unstable external environment.'

He explained that the kidneys, besides monitoring and stabilising the body's internal landscape, are vital in excreting or removing waste products and toxins from the body.

Equally vital are their endocrine functions, such as producing hormones for red blood cell production and blood pressure control.

They also regulate water and salt balance, control the blood's acidity levels and produce vitamin D in its active form to maintain bone health.

Dr Pary Sivaraman, consultant kidney and transplant physician at the Singapore Clinic for Kidney Diseases, said: 'It's not difficult to imagine why kidneys are very important. If there was total cessation of both kidneys' function, a person would not live beyond at most a few days.'

Most people have two kidneys, each having its own set of nerves, lymph drainage and blood supply.

Kidneys usually receive 20 to 25 per cent of the blood flow that comes from the heart and 90 per cent of this is pushed through the kidneys' filtration system.

Each kidney has one million of such filtering units, or glomeruli, and these prevent proteins and red blood cells from passing through.

The contents in the filtered fluid may be reabsorbed or excreted, depending on the body's needs.

What is left becomes urine, which contains salts, toxins and water, and is drained into the bladder. When this is full, the urine is passed out.

Kidney failure can lead to complications from the build-up of waste products in the body and the irregularity of salt and water balance and blood pressure levels.

Symptoms which result include reduced appetite, tiredness, nausea, loss of libido, swelling of the limbs and face and high blood pressure.

Dr Sivaraman said that any significant damage to the glomeruli, blood vessels or drainage system of the kidneys can cause them to fail.

The top three causes of chronic renal failure here are diabetes mellitus, chronic inflammation of the glomeruli and hypertension, said Dr Tan Seng Hoe, senior consultant and head of the renal medicine unit at Tan Tock Seng Hospital.

These three causes make up 70 to 80 per cent of cases in Singapore. In 2005, 3,569 people suffered from end-stage renal failure.

Dr Lau added that very obese people, those with known history of kidney stones, those with strong family history of kidney disease or kidney failure, and older folk are more susceptible to kidney failure.

Dr Gordon Ku, consultant nephrologist at Ku Kidney Medical Centre, said that certain Chinese herbs and painkillers can also cause damage to the kidneys.

He said: 'It's possible to reverse kidney failure at an early stage.

'For instance, if your urine is leaking protein, restricting the amount of protein in your diet may help. Medicine can also control protein leaks and blood pressure.'

Early detection and prevention is the key in the fight against kidney disease. (See other story.) Asked what people can do to look after their kidneys, DrTan said: 'Avoid excessive salt intake and smoking. Patients with diabetes should control their condition.'

Dr Lau said staying generally healthy is the best means of preventing kidney disease for those with no known medical problems.

Dr Sivaraman summed it up: 'As the major causes of kidney failure are related to diabetes mellitus and hypertension, steps to prevent these diseases would help in the prevention of kidney failure.'

This article was first published in Mind Your Body, The Straits Times on July 23, 2008.