Kidney replacement therapy
General information:
In cases of severe or complete renal failure, the loss of kidney function can be treated with so called kidney replacement therapy. In general, a form of dialysis is used to filter the blood. In cases of severe chronic kidney diseases, the renal transplantation is a better form of treatment.
Dialysis:
As a replacement for the own kidney function, it is possible to undergo dialysis as a therapeutic method. It is a blood purification procedure which washes the blood artificially, but comparably to the natural kidney function: So-called urinary substances like excess water and toxins are removed from the body. However, even if the filter function can be imitated with the machines, the endocrinological functions (production of hormones, enzymes etc.) cannot be replaced by this form of treatment.
Dialysis patients can live and work quite normally. If not restricted due to other diseases, physical exercise is recommended. However, the shunt must be protected and, thus, contact sports should be avoided. The everyday life of dialysis patients is restricted by the regular dialysis sessions and the lifestyle rules considering diet and fluid intake, which go along with the treatment.
1. Hemodialysis / Haemodialysis:
In short, a device filters the blood outside the body comparable to an artificial kidney.
1.1 Preparation – Creating a shunt:
It is not possible to channel blood from a normal arm vein through a dialysis machine in sufficient quantity and at sufficient speed. Thus, before connecting the patient's blood circulation to the artificial kidney, the patient undergoes surgery to connect an artery with a vein to create a so-called “shunt” or “arteriovenous fistula”. Now, the blood flow and pressure through this vein is increased. Then, the vessel widens and develops a thicker vessel wall to manage the new conditions. The fistula can easily be felt and punctured with a needle and has sufficient blood flow for the dialysis. Usually, the shunt is placed above the wrist on the non-dominant side. The surgery for the shunt is planned normally one to two months prior because it takes about 4-6 weeks for a shunt to “mature” – to be usable for the treatment. However, in case of an acute impairment of the kidney function, a central venous catheter (CVC) can be used as a temporary solution till the shunt is matured. A CVC is a plastic tube which is inserted into a large body vein under local anaesthetic, where it can only remain for a few weeks due to an increased risk of infection and thrombosis.
1.2. The hemodialysis procedure:
Generally, hemodialysis is carried out three times a week in a specialized dialysis center for about four to five hours each. However, the time and frequency may vary from patient to patient and depends on height, weight, residual renal function and the individual life circumstances. Other services like nutrition counseling and an individual adapted exercise program are part of the dialysis sessions too.
1.3 How hemodialysis works:
The blood from the shunt flows through the dialysis machine. In the machine, between the patient’s blood and the dialysis fluid is a special membrane. Based on the principal of diffusion, mass transfer of substances in the blood follows a concentration gradient regulated by the semipermeable membrane. Consequently, small molecules like the previous mentioned urinary substances, e. g. toxins and creatinine, as well as electrolytes are able to pass the membrane. In contrast to them, bigger molecules and substances, e. g. the crucial red blood cells (erythrocytes), fats and proteins, stay in the blood. Moreover, during dialysis, excess water can be removed from the patient’s blood. To prevent the loss of crucial substances, e. g. minerals like potassium, sodium and magnesium, the concentration of those minerals has to be similar in the dialysis fluid. Additionally, to lower the risk of the formation of life-threatening blood clots in the machine, blood thinners are used.
Analogia of the semipermeable membrane and diffusion in the dialysis treatment:
The special dialysis membrane can be compared to a net in a river full of rocks and wooden branches of all sizes: Only small stones and wooden sticks can go through while bigger rocks and tree trunks are hold back. At the same time, there is an attentive bouncer (diffusion) who controls that net. He watches out that about the same number of rocks and sticks are hold back as let through. Thus, the concentration of the small object in front of and behind the net stays the same at all times. In other words, the bouncer helps the stones and sticks to go through the net or he even transports them back to the other side if needed, to ensure a constant equlity of objects on both sides of the net.
2. Peritoneal dialysis:
In short, the own peritoneum is utilized as a natural dialysis membrane. The own body is used as an dialysis machine.
2.1. Preparation – Inserting the dialysis catheter:
As preparation for the treatment a catheter is inserted near the patient’s belly button through the abdominal wall into the abdominal cavity. It is a short surgical procedure and is performed under anesthesia. The catheter is a small plastic tube with a length of about 35 centimeters (13 inches) and a diameter of 0,5 centimeters (0,2 inches). About 15 centimeters (6 inches) are left outside. From now on, through this tube the dialysis fluid is channeled into the abdominal cavity where the peritoneum is used as a natural semipermeable membrane – as a dialysis machine inside the patient.
2.2. The peritoneal dialysis procedure:
This treatment can be performed at home and by the patient himself. Thus, the regular visit of the dialysis center as it is needed for the hemodialysis is not necessary. Normally, the treatment is performed at night while the patient sleeps for a duration of about eight hours. The dialysis fluid is channeled into the abdominal cavity via the catheter, accumulates with the urinary substances (e. g. toxins, waste, creatinine and water) and then removed. Due to the consistent removement of waste, this treatment can be seen as rather gentle for the body.
2.3. How peritoneal dialysis works:
The peritoneum is a thin skin covering the whole abdominal cavity and most of the internal organs. The abdominal cavity is not filled with blood or any other fluid. Spread out, the peritoneum has an area of about two square meters (21,5 square feet). As it is very well supplied with blood, it is suitable as a natural dialysis machine with the peritoneum itself as the membrane.
Urinary substances (toxins, waste etc.) are transported via the tiny blood vessels to the peritoneum. On the other side, there is the abdominal cavity filled with dialysis fluid. Now, the peritoneum functions as a semipermeable membrane. Again, the effect of diffusion comes in hand. Due to a concentration gradient (This means: There are more particle of urinary substances in the blood than in the dialysis fluid.), the toxins and waste products pass through the peritoneum into the dialysis fluid. Since the dialysis fluid contains glucose, excess water can pass through the peritoneum into the dialysis fluid too. The reason for the passage of water is again the diffusion due to a concentration gradient: The concentration of glucose is higher in the dialysis fluid than in the blood. Nature always aims maintaining a balance. Thus, water passes on the other side to the dialysis fluid to “lower” the concentration of glucose or respectively “increase” the concentration in the blood.
Differences between the two dialysis forms:
In contrast to the hemodialysis, the peritoneal dialysis can be performed at home and by the patient himself. Thus, it offers a lot more freedom. Furthermore, the stress on the circulatory system is lower, lifestyles rules are less strict and no blood thinners have to be used. Nevertheless, it is crucial to perform this procedure at home under sterile conditions and to store the needed materials correctly. Thus, a common complication is a peritonitis, an infection of the peritoneum caused by germs from the skin or the intestine entering the abdominal cavity.
However, patients with little to no residual kidney function are not suitable for the peritoneal dialysis and have to be treated with hemodialysis. Moreover, peritoneal dialysis can only be performed for about five to ten years due to changes in the abdominal cavity and the peritoneum. Also, patients with diabetes have to be cautious with the dialysis fluid which contains high concentrations of glucose. Additionally, for some patients are bothered by the aesthetic look of the catheters on the belly. Thus, hemodialysis is generally suitable for (almost) every patient while peritoneal dialysis offers more freedom in life.
Symptoms of peritonitis are abdominal pain, fever, discoloration of the normally clear dialysis fluid. If these symptoms appear, please, visit your treating dialysis center or physician immediately! Generally, peritonitis can be treated with antibiotics and, afterwards, the peritoneal dialysis can be continued in most cases.
Please, discuss possible complications of your specific treatment procedure with your treating physician!
In cases of chronic kidney failure, a renal transplantation may be needed. Treatment with dialysis bridges the often years-long wait for a suitable organ. A renal transplant can be donated either alive by a relative or post-mortem by an organ donor. Now, the “new” kidney works as a replacement of the own kidney. It takes over and continues the natural kidney functions. Normally, the “old”/own kidneys remain in the body. However, as it is a foreign object, the body tries to fight against and rejects the organ. To prevent this, patients have to takes immunosuppressive pharmaceuticals regulating the immune system.
For more information about kidney transplantation, click here.
Did you know?
The dimensions of a typical dialysis machine are similar to an adult human being. In contrast, the human kidneys are about the size of a fist. Aren’t nature’s abilities awesome?
Please, discuss with your responsible physician the treatment options suitable for you!