The primary function of the kidney is to make urine and purify the blood. Each kidney removes waste materials, and other chemicals which are not required by the body.
Important functions of kidney are described below.
Purification of blood by removal of waste products is the most important function of the kidney.
The food that we consume contains protein. Protein is necessary for the growth and repair of the body. But as protein is utilized by the body it produces waste products. Accumulation and retention of these waste products is similar to retaining poison inside the body. Each kidney filters blood, and toxic waste products which are eventually excreted in the urine.
Creatinine and urea are two important waste products, that can easily be measured in the blood. Their “values” in blood tests reflects the function of the kidney. When both the kidneys fail, value of creatinine and urea will be high in blood test.
The second most important function of the kidney is the regulation of fluid balance by excreting excess amount of water as urine while retaining the necessary amount of water in the body, that is essential for living .
When the kidneys, fail they lose the ability of removing this excess amount of water. Excess water in the body leads to swelling.
The kidneys play another important role of regulating minerals and chemicals like sodium, potassium, hydrogen, calcium, phosphorus, magnesium and bicarbonate and maintains normal composition of body fluid.
Changes in the sodium level can affect person’s mental state, while changes in the potassium level can have serious adverse effects on the rhythm of the heart as well as functioning of the muscles. Maintenance of normal level of the calcium and phosphorus is essential for healthy bones and teeth.
The kidneys produce different hormones (renin, angiotensin, aldosterone, prostaglandin etc.) which help regulate water and salt in the body, which plays vital roles in the maintenance of good blood pressure control. Disturbances in hormone production and regulation of salt and water in a patient with kidney failure can lead to high blood pressure.
Erythropoietin is another hormone produced in the kidneys, it plays an important role in the production of red blood cells (RBC). During kidney failure, production of erythropoietin is decreased, which in turn leads to decreased production of RBC resulting in low haemoglobin (anaemia). This is the reason why in patients with kidney failure, the haemoglobin count does not improve despite supplementation with iron and vitamin preparations.
The kidneys convert vitamin D into its active form which is essential for the absorption of calcium from food, growth of the bones and teeth, and keep the bones strong and healthy. During kidney failure, decreased active vitamin D leads to decreased, growth of bones and they also become weak. Growth retardation may be sign of kidney failure in children.
In the process of blood purification, the kidneys retain all necessary substances and selectively removes excess fluid, electrolytes and waste products.
Let us understand this complex and amazing process of urine formation.
Do you know that every minute, 1200 ml of blood enters the kidneys for purification, which is 20% of the total blood pumped by the
Symptoms of kidney diseases vary from person to person. A lot depends on the type of underlying disease and its severity. Symptoms are often, vague and non-specific, and therefore the disease is difficult to diagnose in the early stages.
Swelling of face, abdomen and feet, is a frequent presentation of kidney disease. One characteristic of swelling due to kidney disease is that it is usually noticed first below the eyelids (this is called peri-orbital oedema) and is most noticeable in the morning.
Kidney failure is a common and important cause of swelling. But one needs to bear in mind that swelling does not necessarily indicate kidney failure. In certain kidney diseases, despite normal kidney function, swelling still occurs (e.g. nephrotic syndrome). Equally important, is the fact that swelling may not be seen in some patients despite significant kidney failure.
Loss of appetite, abnormal taste in the mouth and poor food intake are common problems faced by a person with kidney failure. With worsening of kidney function, there is increased level of toxic substances, which leads to nausea, vomiting and occasionally, intractable hiccups.
In patients with kidney failure, hypertension is common. If hypertension occurs at a young age (less than 30 years) or blood pressure is very high at the time of diagnosis, the reason may be that of a kidney disease.
Anaemia and weakness Generalized weakness, early fatigue, poor concentration and pallor are common complaints of a person with anaemia (low haemoglobin level). At times these may be the only complaints of a person in the early stages of chronic kidney failure. If anaemia does not respond to standard treatment, it is essential to rule out kidney failure.
Non-specific complaints Low back pain, generalized body aches, itching and leg cramps are frequent complaints in kidney disease. Retardation of growth, short stature and bending of leg bones are common in children with kidney failure.
1. Reduction in urine volume, is very common in various kidney diseases.
2. Burning sensation in urine (dysuria), frequent urination (frequency) and passing of blood or pus in urine are symptoms of urinary tract infection.
3.Obstruction to the normal flow of urine can lead to difficulty in ‘voiding’ (passing urine), and poor stream of urine. In severe conditions, complete inability to pass urine can occur.
Although a person may have some of the above mentioned symptoms and signs, it does not necessarily mean that the person is suffering from kidney disease. However, in the presence of such symptoms, it is highly recommended to consult the doctor and to rule out any possibility of kidney disease and other systemic illnesses by blood and urine tests. It is important to remember that serious kidney problems may exist silently for a long period without significant symptoms and signs.