Dialysis is the process of diffusion across a semipermeable membrane to remove unwanted, toxic substances from blood while adding desirable components.
A continuous constant flow of blood on one side of the semipermeable membrane and a cleansing solution (dialysate) o the other hand allows removal of waste products from the blood.
Types of dialysis:-
- Peritoneal dialysis
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In this method, a dialyzing machine or artificial kidney is connected to the patient’s body. In this, blood from an artery of the patient is diverted through a dialyzing membrane after cooling it to 0oC and mixing with an anticoagulant (heparin).
Dialysing membrane has pores equal to those of glomerular capillaries and acts a super fine strainer. This tube is immersed in a solution called dialysate.
The dialysate is isotonic to blood plasma with respect to the normal solutes and is hypotonic with respect to metabolic wastes. Hence the waste like urea, uric acid, creatinine, excess H+ ammonium salts, etc. from blood diffuse across the membrane into the dialysate.
The dialysate is changed as and when required.
Blood from dialyzer is returned to the body through a vein after warming it to the body temperature and mixing with an anti-heparin. For hemodialysis, patients often have to be hospitalized, and they would have to spend about four to five hours at least twice or thrice a week.
Hemodialysis is expensive.
Since vascular access in necessary for hemodialysis, risks of blood-borne infections like staphylococcal infections are more.
Advantages of hemodialysis
- Short treatment time and minimize interruptions of life-style between treatments.
- More efficient than peritoneal dialysis.
- The patient can lead more or less normal life.
- It can also help in the recovery of reversible kidney damage.
- No part of the equipment is fitted inside the body.
- Bacteria and viruses cannot pass through it.
- Peritoneal dialysis
The present form of peritoneal dialysis is continuous ambulatory peritoneal dialysis or CAPD.
Unlike hemodialysis, CAPD can be carried out anywhere by the patient himself without any assistance. Here the peritoneum of the abdominal cavity is itself the semipermeable membrane.
A catheter is surgically implanted in the abdominal cavity of the patient. A bag containing the dialysate fluid is attached to the catheter, and the fluid is infused into the abdominal cavity through the catheter.The wastes and unwanted substances from the blood vessels pass into the fluid during this peritoneal wash.
The composition of the dialysate fluid can be modified according to the patient’s needs. The abdominal cavity has to be emptied every four to six hours, and new fluid has to be replaced.
Meanwhile, the patient can carry out his normal activities. Complications of this dialysis include peritonitis, obesity, abdominal hernias, etc.
Advantages of peritoneal dialysis
- Avoidance of frequent vascular access which is necessary for hemodialysis.
- Slower clearance rate which may be advantageous for patients with cardiovascular instability.
- It is more amenable to total self-treatment and doesn’t need hospitalization.
Organ transplantation involves the transfer of organs from one person to another.Skin transplantation was first to be done.
Renal transplantation is the transfer of kidney fro one person to another.
The graft is usually for a cadaver (dead person) donor or from a sibling or a parent. Kidney transplantation. Like other organ transplantation is also based on the Principle of Histocompatibility proposed by Alesis Carr.
This principle states that every individual has differences in the tissues at the genetic level and if there are many genetic differences and so chemical differences between the recipient and the donor, the rejection will be severe. But if they are histocompatible, The process of rejection will be slow.
The rejection of the transplanted kidney is due to immunosuppression which is immune in which the cell-mediated immune system of T-cell of recipient’s body rejects the transplanted organ as “non-self.”
In immunosuppression, major histocompatible complex antigens and many minor antigens present on the surface of the cells of transplanted kidney stimulate the production of antibodies which initiate the process of rejection of transplanted kidney.
To enhance the chances of successful renal transplantation, following measures are suggested:
- The kidney is usually taken from the member of sibling species(having more or less similar genetic constitution).
- ABO (blood group) compatibility is essential.
- Select the donor kidney on the basis of HLA (Human Leucocyte Antigen).
Long-term immunosuppressive therapy is required. Drugs used to avoid immunosuppression are called immunosuppressants. Most commonly used immunosuppressants are: antimetabolites, alkylating agents, radiations (X-rays, alpha rays, beta rays), cyclosporin, anti-lymphocyte globulins, adrenal corticoids, etc.
These immunosuppressants hinder the development of lymphocytes.But these immunosuppressants are not only highly susceptible to a number of infectious diseases. Cervix and skin cancer have been detected in the patients who had undergone renal transplantation.
Approximately 50% of patients will have some skin malignancies by 15 years post-transplant.
Significance of Kidney Transplantation
- Renal transplantation offers the possibility of restoring kidney function kidney function and thereby correcting many metabolic abnormalities.
- Transplanted kidney, unlike the artificial kidney, replaces the endocrine as well as excretory function. This allows the return of erythropoiesis by the secretion of erythropoietin and returns to normal calcium metabolism by the hydroxylation of cholecalciferol.