An Introduction to Your Kidneys

Kidneys are main organs of plumbing system (urinary system). They remove all waste substances and extra water in the form of urine. This is done by filtering the blood. There are 2 kidneys each located on either side of the spine. They are bean-shaped organs about the same size as a fist. At least 1 healthy kidney is needed for a normal life. Each kidney is encased in fatty cushion (perinephric fat) and a fibrous tissue outside the fat (Gerota’s fascia). As said earlier their main job is to filter the blood through tiny tube like structures or units called nephrons. Each kidney has around 1 million nephrons although this is variable. Each nephron has blood vessels coming into Bowman’s capsule (glomerulus). Blood is filtered here and the filtered fluid goes through convoluted [coiled] tubules (smaller tubes) where most of the fluid is absorbed along with electrolytes (Figure 2). Nephrons could be lost due to diseases of the kidney, trauma, by operation and conditions like diabetes and high blood pressure. Blood passes through nephrons and waste products and excess water are removed from the blood and turned into urine. In addition to filtering blood, kidneys also produce hormones called erythropoetin (which stimulates bone marrow to produce blood cells), renin (hormone that has a role in controlling blood pressure), vitamin D (regulates Calcium). There is gradual decrease in kidney function with increase in age.

Figure 2: Nephron [PCT: Proximal Convoluted Tubule; DCT: Distal Convoluted Tubule] There are blood vessels around the PCT and DCT which are not shown.

What are the diseases affecting the kidneys?

There are several types of kidney diseases. Kidneys could be defective at birth or acquire diseases after birth during infancy, childhood or in adulthood. Sometimes diseases in other parts of the body such as diabetes could affect kidneys.

• Inherited: Polycystic kidneys
• Infections: Pyelonephritis
• Inflammation: Glomerulonephritis
• Kidney tumours: Benign and malignant
• Obstructive: Due to obstruction to the flow of urine.
• Reflux: Scarring of the kidney due to backflow of the urine
• Kidney stones
• Systemic diseases: Diabetes, high blood pressure (Hypertension)

What are the manifestations of kidney disorders?

There may not be any kidney disease symptoms. Some of the manifestations are:

1. Increased frequency day and/or night
2. Discomfort or pain while passing urine
3. Blood in the urine : Visible or non-visible
4. Swelling/puffiness of the face particularly around eyes. Swelling around ankles due to fluid retention
5. Loin pain (back pain)
6. Foamy urine
7. Feeling tired, unwell with loss of appetite
8. Shortness of breath
9. Feeling sick

How do I keep my kidneys healthy?

Common risk factors for kidney disease are diabetes, high blood pressure, family history of kidney problems, obesity and smoking. To keep kidneys going well it is important to drink plenty of water, exercise and eat healthy diet. If you suffer from diabetes or hypertension, get appropriate advice from your GP and make sure that your kidneys are working well. If you notice any urinary problems particularly after the age of 50, it is important to get checked for kidney diseases. Some drugs/medications could also damage kidneys. Early detection is very important.

What are the tests done for kidney diseases?

• Blood Substances: Taking a small blood sample for checking the levels of creatinine, urea and electrolytes (sodium, potassium and chloride) tells the doctor the general state of kidneys. These substances are cleared by the kidneys every minute. Normal level would indicate satisfactory function of kidneys.
• Urine examination: A test to check the colour of urine and its contents, such as sugar, protein, red blood cells, white blood cells and bacteria.
• Ultrasound (US) examination: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.
• Computerised Tomography (CT) Urography: A series of pictures of the kidneys, ureters, and bladder to find out if cancer is present in these organs. A contrast dye is injected into a vein. As the contrast dye moves through the kidneys, ureters, and bladder the radiology doctor carefully examines for any abnormality.
• Magnetic resonance imaging (MRI): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body.
• MAG-3 (Mercaptuacetyltriglycine) Renography: A renal MAG3 scan is a nuclear medicine test that allows doctors to see your kidneys and learn more about how they are individually functioning (split function). This is particularly useful in hereditary cancers.
• Biopsy: The removal of cells or tissues that can be viewed under a microscope by a pathologist to check for signs of kidney cancer. To do a biopsy for renal cell cancer, a thin needle is inserted into the tumor and a sample of tissue is withdrawn. In most cases however biopsy is not performed as the appearances (images) in CT or MRI scan are sufficient to make a diagnosis of kidney cancer.