Just above a litre of blood passes both kidneys every minute and one tenth gets filtered out as fluid. Blood cells, most proteins and fat particles stay in. Water and anything smaller get squeezed out!
Next, the kidneys do some fine tuning. They take back in what is useful to the body: the right amount of minerals, glucose, amino-acids and water.
3 Water balance.
Kidneys pee more when we drink more but conserves water by peeing little if we are not drinking enough.
Hundreds of waste products like urea, toxins and drugs are filtered out and not taken back. This way, the kidneys keep the inside of the body clean.
5 Acid-base balance
Our bodily functions like food metabolism produce a lot of acid. The kidneys are the only organs that gets rid of excess acid.
The kidneys keep the environment in the body stable. It includes keeping the concentration of many chemicals in the body within a tight range.
7 Blood pressure control.
The kidneys control blood pressure by getting rid of excess salt and releasing various hormones. If the kidneys are diseased, blood pressure goes up.
8 Erythropoeitin production
The kidneys produce erythropoeitin (EPO) that makes the bone marrow produce red cells. Without any EPO, we become severely anaemic.
9 Vitamin D activation
Kidneys convert the vitamin D we get from food and the sun into an active form that keep our bones strong and healthy.
10 Glucose control
The kidneys help to stabilise blood sugars by controlling the loss of glucose in the urine and by making new glucose when levels go low. This is why the newest class of drugs for diabetes act on the kidneys.
Kidney (renal) diseases are many and varied. What is commonly encountered in daily practice and what is feared by many patients is End Stage Renal Disease requiring dialysis. There are a lot of myths and half truths that I have encountered in my practice over the years. One of them is that “pou change ou du sang kan fer dialyse”, another one is that “dimoune mort kan fer dialyse” , yet another funny one is ” dimoune dire ki kan fer dialyse ki…” and so on…I shall dispel all these myths and half truths over the next posts.
The main complication of most kidney diseases is End Stage Renal Disease (ESRD), which is as the name suggests, the last stage of kidney failure, and the patient will now require dialysis. The main causes of ESRD are Diabetes Mellitus and Hypertension which are quite prevalent in Mauritius. Almost half of the Mauritian population is diabetic, or pre diabetic and a quarter of the population is hypertensive. This leaves us all at high risk of chronic kidney failure or disease (CKD), a condition in which the kidneys are irreversibly and permanently damaged and eventually renal replacement therapy will be needed.
There are five stages of CKD and that is graded mainly as per kidney function. The last stage of which is ESRD, a situation where renal replacement therapies should be considered. The treatment of choice for ESRD is a kidney transplant. A healthy compatible donor must be found and if all tests are ok, a surgery is done whereby a healthy kidney from the donor is removed and transplanted in the recipient (the patient with ESRD). It is worth pointing out that most people are born with two kidneys and only one is needed as such to maintain life. Hence this enables us to donate one kidney.
However very often, a potential donor is not found in time and thus the patient is left with no choice but starting on dialysis. This will be elaborated in a further post.
The kidneys are located deep in the lower back to the left and right of the spine near the lower ribs.
Each kidney is shaped like a bean with the size of a fist. It is on average about 11cm long and 6cm wide and 150g in weight. These dimensions are obviously proportional to the person’s height.
The right kidney lies lower than the left kidney as a result of being pushed down by the liver. The right kidney is also slightly smaller than the left.
Most people are born with 2 kidneys but some healthy people can have 1 or 3 or 4 (click here and here to find out more) kidneys too!
The kidneys move up and down by a few centimetres as we breathe in and out.
The kidneys receive 20% of all the blood the heart pumps out. That is just above one thousand millilitres every minute!
Taking in all that blood flow, the kidneys filter out about 120 millilitres of fluid every minute. Don’t worry, they later reabsorb most of the fluid back in the body. After all, we normally pass just over a litre of urine a day!
Each kidney contains just over one million nephrons. A nephron is a miniature filter that receives blood, filters and reabsorbs fluid to produce urine.
Each kidney has a cap above upper pole. This is the adrenal gland which functions separately from the kidney and produces important hormones.
The kidneys shrink slowly as we get older but this process occurs faster and earlier in kidney disease. A badly shrunken kidney will barely function.