When the kidneys are gradually destroyed over a period of months or years, chronic renal failure ensues.

THE kidneys? main function is to filter blood to get rid of waste products, toxins, and excess water and electrolytes from the body, whilst reabsorbing useful chemicals. These products are produced by the normal metabolic processes of the body.

Many medicines are excreted by the kidneys. The kidneys help in the regulation of the blood pressure and also produce hormones which help regulate the production of red blood cells and the growth and maintenance of bones.

The kidneys enable a person to consume various foods, medicines, fluids, and substances without toxic by-products reaching harmful levels in the body.

Kidney (renal) failure occurs when the kidneys are unable to perform their functions, leading to accumulation of toxic substances in the body and consequent harm to health.

Renal failure can be acute or chronic. The former occurs rapidly, while the latter occurs gradually over many years during which the kidneys are destroyed over a period of time, usually months or years.

Chronic renal disease results in the accumulation of toxic substances, waste materials, and fluid in the body. It also leads to high blood pressure, altered acid and electrolyte balance, anaemia, and bone disease.

Chronic renal disease is categorised into stages. when the loss of kidney function is total or near total, it is called chronic renal failure or end stage renal disease (ESRD). at this stage, a person requires dialysis or kidney transplantation to stay alive.

Causes

The main causes of chronic renal disease are diabetes mellitus and high blood pressure. this is of concern because there are many people with one or both conditions. The overall prevalence of diabetes was 11.6% in the National Health and Morbidity Survey (NHMS III) 2006, with the prevalence of newly diagnosed cases having increased from 2.5% in 1996 to 5.5% in 2006.

The prevalence of high blood pressure was 32.2% in those aged 18 years and above.

Both Type 1 and 2 diabetes mellitus cause diabetic nephropathy, which is the leading cause of death in many countries. Uncontrolled high blood pressure damages the kidneys with the passage of time. The NHMS III reported that only 26.3% of those who were aware of their condition and currently receiving treatment were found to have their blood pressure controlled. The overall control of high blood pressure was an abysmal 8.2%.

Renal diseases also result in ESRD. The causes include chronic kidney infection, glomerulonephritis, which damages filtration in the kidneys, polycystic kidney disease, and stones. Narrowing of the arteries supplying the kidneys causes ischaemic nephropathy. Obstruction of the urinary tract by stones, prostate enlargement, and narrowing (strictures) may also cause kidney disease.

Prolonged use and abuse of analgesics like acetaminophen and ibuprofen can lead to analgesic nephropathy.

Clinical features

As the kidneys are able to compensate for disordered function, chronic renal disease may progress without symptoms for a long time.

Because of the multiple functions of the kidney, the symptoms vary considerably, even to the extent that there may be no decrease in urine output even in advanced ESRD.

The features of chronic renal disease include frequent urination, especially at night (nocturia); high blood pressure; swelling of the legs and puffiness around the eyes due to fluid retention; fatigue, pallor and breathlessness due to anaemia or accumulation of waste products; loss of appetite; nausea and vomiting; bone pain and fractures; bleeding tendencies due to poor clotting; and decreased sexual interest and erectile dysfunction. It is advisable for individuals with such features to consult a doctor.

It is advisable for those who have diabetes and/or high blood pressure to ensure there is good control of their conditions. It is also advisable for those who have diabetes, high blood pressure, or kidney conditions to consult a doctor if pregnancy is known or suspected.

As there is often no symptom in the early stages of chronic renal disease, reliance has to be placed on laboratory investigations to make the diagnosis. It is advisable for any person who has the condition(s) that cause chronic renal disease to have such tests regularly. The majority of the tests do not require hospitalisation.

Urinalyses provide information about kidney function. The presence of protein, red and white blood cells, and casts in the urine would raise suspicion. more sensitive tests for protein are the measurement of albumin and creatinine. The ratio of urinary albumin to creatinine provides a good estimate of the daily albumin excretion.

The collection of urine for 24 hours enables analysis of proteins and waste products like creatinine and urea.

The glomerular function rate (GFR) provides information about overall renal function. It decreases with worsening of renal function. The GFR can be calculated from the amount of creatinine and urea excreted in the urine collected in the 24-hour period. It can also be calculated from special compounds given intravenously.

The blood creatinine and urea increases with deterioration of renal function. there would also be altered electrolyte balance, particularly potassium, calcium, and phosphorus, as well as altered acid-base balance.

The disruption of blood cell production and decreased life span of red cells leads to low haemoglobin (anaemia). Blood loss in the gut can also contribute to anaemia.

Ultrasound would reveal a shrunken kidney in chronic kidney disease, although they may be normal or enlarged in size in conditions like adult polycystic kidneys and diabetic nephropathy. It may also reveal the presence of urinary obstruction and kidney stones.

A kidney biopsy may be done to obtain tissue samples of the kidneys for microscopic examination, especially when the cause of the kidney disease is unclear. It involves introducing a needle through the skin into the kidney under local anaesthesia and is usually done on an outpatient basis.

Management

There is no cure for chronic kidney disease. The management goals are to slow the progression of disease, treat the causes and contributory factors, treat complications, and replace lost function.

The general measures involve:

> Ensuring good control of diabetes. Those whose blood glucose control is poor are at increased risk of all the complications of diabetes, including chronic kidney disease.

> Good control of high blood pressure slows down the progression of chronic renal disease. The blood pressure has to be kept below 130/80 mm Hg if there is kidney disease. The angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB) are medicines which have a protective effect on the kidneys.

> Good diet control slows down the progression of chronic renal disease. this involves restricting protein intake and limiting the intake of salt, potassium, and phosphorus. The amount of water consumed must not be excessive. Adherence to the advice from the doctor and dietician is crucial.

> Cessation of smoking.

> Weight reduction.

> Avoid, or use under medical supervision, certain medicines, which include analgesics like aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen; antacids and laxatives that contain magnesium and aluminum; H2 antagonists like cimetidine and ranitidine; pseudoephedrine decongestants; and traditional medicines.

Specific problems require specific treatment, and they include:

> Diuretics for fluid retention.

> Erythropoiesis stimulating agents for anaemia. These agents replace the deficiency of erythropoietin, which is produced by healthy kidneys.

> Medicines that bind phosphorus in the gut and vitamin D for bone disease due to chronic renal disease.

> Correction of acidosis.

When the kidney function reaches a stage in which it is severely compromised, dialysis or transplantation is required for the patients to stay alive.

There are two types of dialysis, i.e. through the blood vessels (haemodialysis) or through the abdominal cavity (peritoneal dialysis). The body?s waste products are removed by circulating the blood through an artificial kidney machine in the former, and through a catheter inserted into the abdominal cavity in the latter.

Dr Milton Lum is a member of the board of Medical Defence Malaysia.

This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.