What is Dialysis
Dialysis is a treatment that artificially reproduces certain functions of the kidney, cleaning the blood from excess waste products and water.
Dialysis respects the principles of passive diffusion of solutes and ultrafiltration of fluids, allowing to reproduce the filtration that occurs in the kidney. The patient's blood flows through a dialysis membrane with pores of varying sizes, large enough to allow small ions and solutes to pass between two fluid compartments, but not enough to allow larger components, such as red blood cells and plasma proteins, to escape. . On the other side of the membrane flows a particular dialysis fluid, the composition of which ensures that the most important solutes remain in circulation.
Although dialysis is not a cure, it can extend the life span of the patient while waiting for a donor to be available for a kidney transplant.
Renal filtration and dialysis
Every day the kidneys filter the blood, eliminating waste products and excess water and ions that together make up the urine. When they are healthy, the kidneys regulate the concentration of ions (Na +, K +, H +, HCO3-), other solutes (such as glucose, amino acids, etc.) and water in the blood, and remove waste products from metabolism. However, if the nephrons, the functional units of the kidney, are damaged, the normal processes that take place within them (filtration, secretion, reabsorption and excretion) can be compromised. As a result, the amount of waste products in the blood accumulates to dangerous levels and - in the absence of treatment - can prove fatal.
Dialysis is a treatment that compensates for the poor efficiency of some kidney functions altered by the disease:
- Removal of toxic substances (urea, uric acid, creatinine and other molecules);
- Electrolyte and acid-base rebalancing, keeping some substances, such as potassium, sodium and bicarbonate, at a safe level in the blood;
- Removal of liquids (taken through food and not eliminated with diuresis).
When it is needed
Loss of kidney function can be the common consequence of a wide variety of diseases, affecting the kidneys directly (for example: glomerulonephritis, polycystic kidney, chronic kidney disease, repeated kidney infections, etc.) or indirectly (such as diabetes or hypertension) .
If the kidneys stop functioning properly, waste products accumulate in the blood and cause manifestations such as:
- He retched;
- Itchy skin
- Fatigue (extreme tiredness);
- Blood in the urine (hematuria),
- Swelling in the feet, hands and ankles.
Symptoms tend to appear when the disease is advanced, as the kidney has a large functional reserve. Dialysis is advised on the appearance of clinical signs representative of severe loss of kidney function, with dangerously high levels of waste products in the blood (uremia).
In some cases, dialysis may be recommended regardless of whether the patient has started experiencing symptoms of uremia. A glomerular filtration rate of less than 15 ml / min (GFR, measures how many milliliters of blood the kidneys are able to filter in a given time) is a "valid indication for starting dialysis treatment."
Acute renal failure. A common reason why dialysis may be needed is a severe infection of the kidneys leading to a sudden loss of their function (known as acute kidney failure). In this case, dialysis treatment is only necessary temporarily, until the physiological activity of the kidneys is restored.
Types of dialysis
The two main types of dialysis, hemodialysis and peritoneal dialysis, remove waste and excess fluids from the blood in different ways.
- Hemodialysis
Hemodialysis involves the passage of the patient's blood through a system called an artificial kidney. The dialysis device contains a semi-permeable membrane that divides the internal space into multiple compartments: one contains the dialysis fluid, the other the blood sent to the machine from an arterial catheter. As the blood proceeds inside the device, solute exchanges between the blood and the dialysis fluid occur through the membrane. This membrane, being semipermeable, allows the passage of molecules according to their electrochemical gradient (passive diffusion), preventing that of the corpuscular elements of blood and proteins. The levels of the components of the dialysis fluid can vary and are typically prescribed by a nephrologist according to the needs of the individual patient, in order to facilitate the movement of particular molecules in a particular direction. Once the exchange has taken place, the blood leaves the device and returns to the patient through a venous catheter. Most patients require three sessions per week, each lasting four hours.
- Peritoneal dialysis
Peritoneal dialysis uses a membrane inside the body, the peritoneum, in the same way that the semipermeable membrane is used in hemodialysis. The peritoneum is a thin membrane that lines the inside of the abdomen and surrounds and supports the abdominal organs, such as the stomach and liver. Like the kidneys, the peritoneum contains thousands of small blood vessels, making it useful as a filtering device. During this type of dialysis, the dialysis fluid is introduced through a catheter into the peritoneal cavity. In this way, there is an exchange of solutes between the blood flowing through the capillaries of the peritoneum and the dialysis fluid contained in the peritoneal cavity. After a certain period of time (approximately 4-6 hours), the dialyzed fluid is removed from the abdominal cavity.
Advantages and disadvantages
In many cases, the choice of which type of dialysis to use depends on the patient, as both hemodialysis and peritoneal dialysis produce similar results. However, some health problems can make one method more advisable than another (for example , if the patient has undergone a previous operation on the abdomen).
Typically, peritoneal dialysis is usually recommended as the first form of treatment for:
- Children from two years of age;
- Adults with kidney disease but who do not have other serious health conditions, such as heart disease or cancer.
Hemodialysis is usually recommended for people who cannot undergo peritoneal dialysis, such as older patients, who are not in overall good health. The decision on which treatment method to take is not final and is It is possible to switch from one type of dialysis to another.
Dialysis can cause some side effects:
- Tiredness. A common undesirable manifestation in both hemodialysis and peritoneal dialysis is a persistent feeling of tiredness, caused by a combination of effects that the therapy may have on the body.
- Anemia. It is a common complication of chronic renal failure, due to the reduced secretion of erythropoietin, a hormone that stimulates the formation of red blood cells. Dietary restrictions or the loss of iron and vitamins through hemodialysis can contribute to anemia.
- Weakening of the bones. If the damaged kidneys are no longer able to process vitamin D, calcium metabolism disorders can occur.
- Itching.Many people who undergo hemodialysis experience itchy skin, which is often worse during or shortly after the procedure. This effect is believed to be due to a buildup of potassium in the body. Avoiding potassium-rich foods can help reduce the frequency and severity of this symptom.
- Low blood pressure (hypotension). A drop in blood pressure is one of the most common side effects of hemodialysis, particularly if the patient is diabetic. Hypotension can be caused by the drop in fluid levels that occurs during dialysis. The best way to minimize low blood pressure symptoms (shortness of breath, abdominal and muscle cramps, nausea or vomiting) is to keep your daily fluid intake at the levels recommended by your doctor. If hypotensive symptoms persist, the amount of fluid used during dialysis probably needs adjustment.
- Muscle cramps. During a hemodialysis session, some people experience muscle cramps, usually in the lower legs. This effect is likely due to the muscle's reaction to fluid loss that occurs during hemodialysis. Sometimes, cramps can be relieved by adjusting fluid and sodium intake between hemodialysis treatments.
- Fluid overload. Since fluid is removed from the body during hemodialysis, drinking more fluids than recommended between hemodialysis treatments can cause life-threatening complications, such as heart failure or accumulation of fluid in the lungs (pulmonary edema).
- High blood pressure (hypertension). If you consume too much salt or drink too much fluids, high blood pressure is bound to get worse and lead to heart complications.
- Elevated potassium levels (hyperkalaemia). Potassium is a mineral that is normally removed from the body through the kidneys. If you take more potassium than recommended, the level can become too high and, in severe cases, it can cause heart problems.
- Amyloidosis. Dialysis-related amyloidosis develops when protein material from the blood deposits on tendons and joints, causing pain, stiffness and joint effusion. The condition is more common in patients undergoing long-term hemodialysis (typically more than five years). .
- Staphylococcal infections. Patients on hemodialysis have an increased risk of developing a Staphylococcus aureus infection. The hemodialysis process can allow bacteria to enter the body where they can cause a severe invasive infection. This can spread through the blood, leading to organ dysfunction. multiple (sepsis). Sepsis associated with an invasive staph infection is the second most common cause of death, after heart disease, in patients undergoing hemodialysis.
- Peritonitis. A common side effect of peritoneal dialysis is bacterial infection of the peritoneum. Peritonitis can occur if dialysis equipment is not kept properly sterilized. Patients on hemodialysis have a lower risk of getting the infection, but if this occurs, it tends to be more severe.
- Weight gain. The dialysis fluid that is used during peritoneal dialysis contains sugar molecules, some of which can be absorbed by the body. This effect can lead to weight gain, if the daily caloric intake is not reduced with an adequate diet that may be supported. - under medical advice - from regular exercise.
Results
Dialysis is a challenging treatment, requiring considerable patient cooperation, but also a potential life-saving measure. The success of dialysis in the treatment of kidney failure depends on a number of factors, including the age of the patient and any concomitant chronic diseases (such as heart disease or diabetes). The etiology of the disease also affects survival rates; for example, people with kidney failure caused by polycystic kidney disease and glomerulonephritis tend to have a better long-term prognosis than patients who experience the condition as a complication of high blood pressure. or diabetes. Unfortunately, dialysis can only compensate for the loss of kidney function to some extent and is not a permanent cure. Many people remain on dialysis for a long period of time (in some cases, for the rest of their lives) , but for a significant minority of patients, the ultimate goal is kidney transplantation, which is the best treatment for renal failure. A suitable candidate for such surgery must undergo dialysis until a compatible donor is available ( dead or living) This time period can range from a couple of months to about three years and are ineligible for a kidney transplant, due to an "other serious concomitant health condition, such as a tumor or severe heart disease, they will need to undergo dialysis for the rest of their life. Often, this is a safer option than a transplant.
