Saturday 26th Apr, 2025
Structure and function of the Kidney
The kidneys are two bean shaped organs lying on either side of the backbone in the loins. Each adult kidney weights about 150 gm and is of the size of a closed fist. Some people may have only one kidney which is sufficient to maintain the normal kidney function for whole life. Single kidney may be detected incidentally. The other kidney may not to be present at its normal position.
The main function of the kidney is to remove waste products from the blood and return the clean blood to the body. Blood is carried to the kidney by renal artery and every minute about one liter of blood enters the kidney and after cleaning is carried back from kidney by renal vein. Inside each kidney there are about one million filtering units called nephrons. Urine is formed by the kidneys after filtration of blood and this urine which contains all the waste products is carried by the ureter to the urinary bladder where it is stored and excreted time to time.
These waste products are produced in the body as end products of metabolism-for example urea, creatinine, uric acid. When kidneys fail these waste products accumulate in the blood. Kidneys also excrete drugs and their end products and any toxic substances from the body.
The other main functions of the kidney are:
Level of electrolytes like sodium, potassium, calcium, magnesium is maintained according to the body needs. The electrolytes are essential for normal functioning of various tissues and organs.
The main hormone produced by the kidney is Erythropoietin which helps in formation of the red blood cells of blood. Level of this hormone goes down in patients of chronic kidney disease and the patient develops anemia (low hemoglobin level) The other main hormonal function of the kidney is activation of vitamin D which is essential for maintaining the strength of bones.
Kidneys also produce rennin a substance which is needed for regulation of blood pressure. High blood pressure is usually present in patients of renal failure.
When kidneys fail, water and waste products of the body which are normally removed by the kidney accumulate and cause harmful effects on most of the organs- heart, blood vessels, nervous system, bones, stomach and intestines, skin and blood forming sites (bone-marrow).
Kidney Failure
There are two types of kidney failure:
Acute Kidney Failure
This type of kidney failure happens suddenly in a few days and is potentially reversible if the cause is treated in time. One of the common causes of acute kidney failure in developing countries (including India) is acute gastroenteritis (infection of stomach and intestinal tract) characterized by vomiting and loose motions of sudden onset. The condition causes low blood pressure (due to loss of water from the body) and kidney failure. Similarity low blood pressure due to other causes like heart diseases, blood loss or extensive burns can cause acute kidney failure. So, if we restore the blood pressure in the conditions renal failure can be reversed.
Drugs like analgesics (Pain relieving drugs), certain antibiotics and herbal medicines can cause acute kidney failure. This type of renal failure is potentially reversible if the offending agent is discontinued early.
Chronic kidney failure (Disease)
The earlier term of chronic kidney or renal failure has understandable by common man as well. Any kidney problem which involves structure of the kidney (for example cysts), protein in urine or raised blood urea and creatinine levels and lasts for 3 months or more is called chronic kidney disease.
The common causes of CKD are
Treatment options for chronic kidney disease
In general any kidney disease lasting 3 months or more is called chronic kidney disease. It passes through five stages of progressive decline in kidney function-stage 1 has a normal kidney function and stage 5 is called End stage Kidney Disease or failure and needs replacement therapy, that is replacement of kidney function by dialysis of transplantation.
When kidney failure is diagnosed, the patient suddenly develops a fear and feels depressed. He/she also does not believe it and moves from one doctor to another. Kidneys remove wastes from the body via urine. When kidneys fail body cannot maintain the fluid balance, hemoglobin is low due to the lack of hormone erythropoietin produced by kidneys which maintains normal production of red blood cells.
Blood pressure rises because of the disturbed production of the hormone from the kidney which maintains blood pressure and also due to the accumulation of fluids which are normally removed by the kidney. The failure of the kidney function affects all the organs of the body skin, nervous system, stomach and intestines, heart, bones, chest, endocrine system etc.
With treatment the kidney function can be maintained to a great extent. By controlling high blood pressure, treating infection in the body, by giving medicines to treat anemia and bone disease many of the symptoms can be relieved. A stage will however reach when need for replacement of kidney function arises.
Choice of treatment
Kidney function is replaced by dialysis or kidney transplantation.
The choice of treatment is always decided after a thorough discussion between the doctor on one side and the patient and his family on the other. Since the treatment is life long, patient and the family have to understand the burden and decide whether the benefit is worthwhile. Patient on dialysis or after kidney transplantation may attend his work normally. When a patient is diagnosed as chronic kidney disease it may take months to years before reaching the stage when replacement of kidney function is needed. The time of initiation of dialysis is decided by a number of factors including symptoms, signs and biochemical tests.
Dialysis
Here are two types of dialysis-
1) Hemodialysis
2) Peritoneal dialysis.
Hemodialysis (artificial kidney):
In hemodialysis blood of the patient is cleaned outside the body and the cleaned blood is returned to the body. This is a continuous process. Blood from the patient is taken to a processing unit called dialyser. The dialyser is a filtering apparatus made of a thin membrane which generally is in the form of hairy thin tubes from one end and comes out from the other end and returned to the body. In the dialyser dialysis fluid surrounds the membranes. All waste products from the blood pass through small holes in the membrance to the dialysis fluid which goes into the waste pipe.each dialysis of hemodialysis lasts for 4 hours and the process is repeated 3 times per week.
In hemodialysis blood from the patient needs to be passed to the dialyser and returned to the body after cleaning in the following ways
Advantages of Hemodialysis:
Disadvantages of Hemodialysis:
Complications of hemodialysis
The complications during hemodialysis are:
These complications are generally short lasting and easily treatable
Long term complications
The following problems are noted in patients on long term dialysis:
Anemia and bone disease are related to the presence of kidney disase and need to be treated as before dialysis.
Haemodialysis can be performed in:
However, a water treatment plant to supply purified water is needed. For each hemodialysis approximately 140 litres of treated water are needed. Home hemodialysis machines are fitted with a small water treatment plant.
Peritoneal dialysis:
In peritoneal dialysis the natural membrane-Peritoneum serves as the filter in the same way as the filtering membrane in hemodialysis. Peritoneum is a thin membrane which surrounds the intestine and other organs. It has a rich blood supply. A fluid called peritoneal dialysis fluid containing electrolytes and glucose is put inside the peritoneal cavity through a tube called catheter. The waste products which circulate in blood in kidney failure patients pass through the peritoneal membrane into the dialysis fluid which is periodically removed through the peritoneal dialysis catheter and replaced by fresh fluid. The process is repeated.
The different types of peritoneal dialysis are:
Acute or emergency peritoneal dialysis:
In this type of dialysis a catheter meant for single use is inserted into the abdomen (peritoneal cavity). In adults 2000 ml of fluid is put into the peritoneal cavity. The fluid is removed after 30-45 minutes and repeated cycles of 20-30 are given in 24-36 hours.
This type of dialysis has been given up in most of the dialysis centers and replaced by hemodialysis. However, it can yet be used in emergency situations when hemodialysis is not available. This procedure is painful and has some life threatening complications and should be avoided as much as possible.
Continuous ambulatory peritoneal dialysis (CAPD):
CAPD is used as a replacement treatment in patients with stage 5 or end stage kidney disease. A specially designed permanent catheter is fixed in the peritoneal cavity mostly by a minor surgical procedure. After a gap of about 2 weeks from insertion dialysis is into the peritoneal cavity which takes approximately 15-20 minutes. After 6 hours the fluid is removed and replaced by another exchange of 2 liters of fresh fluid. The process is repeated 4 times a day and a week. When the fluids remains in the abdomen, all the waste products in blood which are normally removed by kidneys are filtered in the peritoneal dialysis fluid which is drained out.
This type of chronic peritoneal dialysis is called continuous ambulatory peritoneal dialysis (CAPD) since it continuously removes the waste products in the blood and the patient remains moving normally and performs normal activities. The fluid is always in the abdomen.
Automated peritoneal dialysis (APD)
In this type of dialysis, machine is used to perform the dialysis fluid exchanges. Generally 10 liters of peritoneal dialysis fluid is exchanged in 5 cycles of 2L each. The machine is programmed to perform 5 cycles of 2 liters each overnight in 8 hours. The patient sleeps after the machine is connected. After disconnecting it in the morning; the patient attends to his/her usual activities during the day and repeats the process every night. The patient may have 2L of fluid in abdomen during day time or keep it dry.
Both the types manual (CAPD) and one with the machine (APD) are comparable in efficacy.
CAPD and APD are performed by the patient himself/herself after getting training from the dialysis personnel. It may be carried out by a helper if the patient is not able to perform it.
Advantages of CAPD/APD
Disadvantages of peritoneal dialysis
Exit site (where the catheter comes out) infection
Kidney Transplantation
Kidney transplantation is the best option of replacement therapy and the patient is free from dialysis. Suitability for transplant is made by the Nephrologist. All patients may not be fit for transplant and in that case will continue on dialysis.
If a patient has an advanced heart or lung disease or is suffering from cancer he/she is not suitable for transplant.
For kidney transplantation a donor is needed.
Donor may be:
Cadaver donor:
Cadaver donor is a dying person serving as kidney donor. If a healthy person meets a motor vehicular accident and gets a severe head injury and becomes brain dead with no chances of recovery he/she qualifies to be a cadaver donor. Such people are alive on supportive treatment with artificial ventilation. They can be donors if they have written a will for kidney donation or the family gives consent for donation.
Living donor:
Living donor are generally close relatives. In some countries unrelated donors like close friends or emotionally related people are allowed as donors.
After kidney transplantation medicines are needed for the whole life till the transplanted kidney is functioning. These medicines called immunosuppressive drugs are also very expensive.
The notion “changes the kidney like the spare part of a machine “is wrong.
Financial implications:
All the three modes of replacement therapy are expensive. Moreover in the Jammu & Kashmir state there is not much support from the health insurance agencies. Reimbursement for those in government services is cumbersome and full of hurdles.
At present on an average the bare minimum expenses for hemodialysis are Rs 11000-12000 per month, peritoneal dialysis 14000-18000 per month. Currently the kidney transplant patients will have to spend approximately 15000 per month soon after transplantation and after a few months the expenses may be 6000-10000 per month. In a few patients expenses may be less.
How to choose the mode of replacement therapy:
Kidney transplantation is the best option in suitable patients. Most of the patients are suitable and the fitness is decided by the Nephrologists. Availability of donor decides the option in suitable patients.
Hemodialysis and peritoneal dialysis are equally effective modes of treatment. The decision is taken by the doctor after discussing with the patient and family after considering other associated illnesses.
For example a renal failure patient with advanced heart failure may be fit for Peritoneal rather than hemodialysis. A patient with repeated abdominal surgeries may not be fit for peritoneal dialysis. Patient may need to be changed to hemodialysis if he develops repeated attacks of Peritonitis on Peritoneal dialysis. A patient on hemodialysis with failed vascular access will have to be shifted to peritoneal dialysis.