According to Levy, Brown, & Lawrence, (2016), kidney dialysis is a procedure that is used to substitute the various normal functions of the kidneys in an individual. Therefore, dialysis is essential in helping people with renal failure to have a chance of living a productive life despite their conditions. Usually, kidneys play a crucial role in the filtration of waste products from the blood. Whenever the kidneys start to fail, dialysis is required to help the body perform the functions of failed kidneys. One of the primary roles of the kidney in the body is the regulation of fluid balance through the adjustment of urine output. It is also crucial in the removal of waste products such as urea from the body.
Dialysis is required when kidneys fail in its two main roles discussed above. Therefore, an individual will start dialysis when kidneys fail to adequately filter the blood leading to the building up of waste products to a critical level within the body (Davis, 2016). The two primary reasons contributing to the need for dialysis are high blood pressure and diabetes (Ramin, 2014). The accumulation of waste products in the body causes sickness in a person. Nephrologists are the doctors that specialized in the conditions and diseases of the kidneys. These doctors determine the need for dialysis among patients through measuring of several chemical levels in the body of the patients. Creatinine and blood urea nitrogen are the two primary chemicals regulated since their rise indicates the decrease of kidney's ability to cleanse waste products from the body.
There are two major types of dialysis. They include peritoneal dialysis and hemodialysis. Peritoneal dialysis involves the use of a fluid that is placed in the abdominal cavity of the patient via peritoneal dialysis catheter to help in the removal of excess of fluid and waste products from a patient's body. In peritoneal dialysis, the body tissues present in the body of the patient is used as a filter. Hemodialysis involves the use of a particular type of filter and machine to help get rid of excess fluids and waste products from the patient's blood (Ramin, 2016). In this type of dialysis, the dialysis machine receives the blood from the body of the patient via a sterile tubing, which is passed into a dialysis membrane that acts as a filter.
The use of dialysis started in the 1940s. In 1943, a Dutch physician called Willem Kolff built the first type of dialyzer referred to as an artificial kidney. He obtained the idea of having a machine that can help in the cleaning of blood, after observing one of the patients suffer from renal failure. After the completion of his invention, Kolff began treating patients with acute kidney failure for the next two years despite only one successful treatment after over a dozen patients. An improved design was manufactured in the early 1950s after more experimentation (Ing, Rahman, & Kjellstrand, 2012). One of the main disadvantages of the model developed by Kolff was that it did not treat end-stage renal disease but only acute kidney failure.
It was Dr. Belding Scribner, who developed a way that could assist in the treatment of end-stage renal disease via the use of an access point on the arms of the patients. The first dialysis center was opened by Scribner in 1962 (Ing, Rahman, & Kjellstrand, 2012). Eventually, Dr. Scribner was able to develop a portable dialysis device that could be used in the dialysis treatment by the patients at home. By 1973, the percentage of individuals receiving dialysis at home was almost 70%.
This essay discusses the concept of dialysis by studying the physiology of kidneys. The various types of dialysis are considered including the way they are done, and the machines involve in the process. It further helps clarify the advantages and disadvantages of hemodialysis and peritoneal dialysis. Finally, the essay covers future works in the field of dialysis.
Physiology of Kidneys
According to Sherwood, (2011), the primary function of the kidneys is the filtration of blood. This process usually takes place in three main processes. During the process, urine is formed as a waste product, which consists of metabolic waste molecules and excess water in the process of renal system filtration. Primarily, the renal system helps the body in the regulation of plasma osmolarity and blood volume as well as the removal of waste as urine. The urine formation takes place in three distinct stages including glomerular filtration, tubular reabsorption, and tubular secretion (Sherwood, 2011). The diagram below shows the parts of the nephron and the role of each component in the filtration of blood as well as the maintenance of homeostatic balance in the body.
Each section of the nephron has a different function to help the kidneys perform its functions. The glomerulus is responsible for forcing small solutes from the blood through the use of high pressure. The proximal convoluted tubule helps in the active transportation of drugs and toxins into filtrate from the interstitial fluid as well as the reabsorption of water, ions, and nutrients into the interstitial fluid from the filtrate. Also, this section is responsible for the adjustment of the pH of the blood through the selective excretion of ammonia into the filtrate, via ammonia's reaction with H+ to formNH4+. The higher the acidity of the filtrate, the higher the volume of ammonia is secreted. There is the presence of aquaporins in the descending loop of Henle, that is responsible for the passing of water into interstitial fluid into the filtrate.
The diffusion of Cl- and Na+ into the interstitial fluid takes place in the thin part of the descending loop of Henle. In the thick section of the descending loop of Henle, these two ions are carried into the interstitial fluid. Therefore, there is more dilution of the filtrate as the filtrate travels up the limb since the only salt is lost and not water. The reabsorption of Cl-, Na+, and HCO3- ions takes place in the distal convoluted tubule as well as the selective secretion of H+ and K+ into the filtrate, to help in the maintenance of electrolyte and pH balance in the blood. Finally, dilute urine is formed in the collecting duct after the reabsorption of solutes and wastes from the filtrate.
It is the process in the kidney where the filtration of fluid in the blood occurs across the capillaries that are present in the glomerulus. Glomerular filtration is the first stage in the formation of urine, and it is the primary physiologic function of the kidneys. It is described as the process of filtering blood in the kidneys, where glucose, fluid, waste products, and ions are excreted from the capillaries in the glomerular (Sherwood, 2011). Most of the materials are then reabsorbed into the body within the nephron, while others leave the body in the form of urine.
Glomerular filtration is responsible for the filtration of the various solutes. The specialized membranes that are present in the afferent arteriole and high blood pressure play a critical role in the process of glomerular filtration. One of the main advantages of the glomerulus is that high blood pressure is maintained regardless of the elements that impact systemic blood pressure. The presence of a "leaky" connection in the glomerular capillary network between the endothelial cells is crucial to help solutes pass through easily. Passive diffusion is responsible for the transfer of all solutes except the macromolecules in the glomerular capillaries. In this stage of filtration, no energy is required (Sherwood, 2011). The glomerular filtration rate is the term that refers to the volume of filtrate that the kidneys form every minute. It is an essential indicator of the kidney function and is regulated by multiple mechanisms.
The glomerulus is a cluster of capillaries that are intertwined, which receives the blood plasma from the afferent arteriole. The glomerular capsule, which is some times referred to as the Bowman's capsule, forms the outer section of the glomerulus and usually consists of a parietal layer on the outside and visceral layer on the inside. The visceral layer is located at the bottom of the thickened glomerular basement membrane. It is made up of podocytes, which later forms small slits through which the fluid passes before entering the nephron. The large molecules such as the red blood cells, albumin, and platelets are restricted by the size of the filtration slits. These large molecules are usually the non-filterable parts of blood.
Tubular Reabsorption and Secretion
Tubular reabsorption is a process in kidney physiology that involves the removal of water and solutes from the tubular fluid and into the blood. The process takes place in the proximal convoluted tubule section of the nephron. In tubular reabsorption, almost all nutrients are reabsorbed, through either active or passive transportation. Hormones play a critical role in the regulation of reabsorption of some essential electrolytes and water (Sherwood, 2011). The most abundant ion is sodium, which is mostly reabsorbed through active transport before being transferred to the peritubular capillaries. Water follows sodium ions out of the tubule to help even out the osmotic pressure, as a result of the active transportation of these ions out of the tubule.
In the peritubular capillaries, there is the independent reabsorption of water due to the presence of aquaporins within the proximal convoluted tubule. It is usually due to high osmotic pressure and low blood pressure that is present in the peritubular capillaries. However, there is the maximum transportation limit of every solute; hence, there is no reabsorption of the excess solutes.
The ascending limb is usually permeable to solutes and not water, while the descending limb is vice versa. Also, it is crucial to note that the loop of Henle extends into the renal medulla, which is characterized by the high presence of salt concentration. Therefore, the loop of Henle concentrates the filtrate through the absorption of water from the renal tubule. As the loop of Henle moves deeper into the medulla, there is an increase in its osmotic gradient. In the figure above, it is found that the two sides of the loop of Henle, perform different functions, leading to a countercurrent multiplier (Sherwood, 2011). Around the loop of Henle, there are the vasa recta, whose role is to act as countercurrent exchanger.
As shown in the figure, the loop of Henle is a countercurrent multiplier, that leads to the creation of a concentration gradients by the use of energy. The descending limb of the loop of Henle has been described as water permeable. The osmolality in this limb increases as the limb descends further into the renal medulla leading to the flow of water to the interstitial fluid from the filtrate. According to Sherwood, (2011), there is a higher osmolality at the bottom of the loop than in the interstitial fluid. Therefore, as sodium and chloride ions exit via the existing channels in the membrane, as the filtrate enters the ascending limb. As the filtrate climbs ups the loop, the active transportation of chloride ions out of the filtrate happens after the sodium ions. Usually, osmolarity is expressed as milliosmoles per liter.
As the filtrate reaches the distal convoluted tubule, usually, the absorption of most solutes an...
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