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Nephrology

Nephrologyis the branch of medicine that specializes in the functions and diseases of the kidney.

Systemic conditions that affect the kidneys along with acute and chronic renal diseases including the systemic problems all come under nephrology. Systemic conditions include diabetes and autoimmune disease, while systemic problems that occur as a result of kidney problems include -

  • Renal osteodystrophy
  • Hypertension
  • Stone disease
  • Renal infections

Dialysis

Dialysis is the process which is used as an artificial replacement for the functions performed by the kidneys in people with renal (kidney) failure. It is used in two types of cases -

  • For those with an acute disturbance in kidney function(acute renal injury and failure)
  • For those with chronic kidney disease (chronic renal failure or end-stage renal disease)

Dialysis is effective in replacing the most important task of the kidneys, which is removing waste and excess water from the blood. This is done through diffusion (waste removal) and ultrafiltration (fluid removal).

Substances in water tend to move from an area of high concentration to an area of low concentration. Similarly, blood flows by one side of a semi-permeable membrane while a dialysate (special dialysis fluid) flows by the opposite side. A semi-permeable membrane is a thin layer of material that contains pores of various sizes. Smaller solutes and fluid pass through this membrane but it blocks the passage of larger substances like red blood cells and large proteins. This replicates the filtering process that takes place in the kidneys when the blood enters the kidneys and the larger substances are separated from the smaller ones.

Ultrafiltration systems eliminate the need for clarifiers. Efficient ultrafiltration systems utilize membranes which can be submerged and air scoured. This offers superior performance for the clarification of wastewater.

There are mainly two types of dialysis, haemodialysis and peritoneal dialysis.

Hemodialysis

Alsospelt asHaemodialysis, is a method that is used to remove the extracorporeal waste such as urea from the kidneys and free water from the blood when the kidneys are in a state of renal failure. It can be an outpatient or inpatient therapy.

Routine hemodialysis is usually conducted in a dialysis outpatient facility of a hospital or a dedicated, stand alone clinic. In special circumstances it can also be done at home but has to be managed or done jointly with the assistance of a trained helper who is usually a family member. The dialysis treatments in a clinic are initiated and managed by specialized staff of nurses and technicians.

Peritoneal dialysis (PD)

This is a treatment for patients with severe chronic kidney disease. The process uses the patient's peritoneum in the abdomen as a membrane across which fluids and dissolved substances like electrolytes and urea are exchanged from the blood.

In automatic peritoneal dialysis, the fluid is introduced through a permanent tube in the abdomen and flushed out every night when the patient is asleep, while in the case of continuous ambulatory peritoneal dialysis this is done via regular exchanges throughout the day.

PD can be used as an alternative to hemodialysis but in rare conditions. Although less expensive it has comparable risks. The primary complication of PD is usually an infection due to the presence of a permanent tube in the abdomen.

Kidney Transplantation

Kidney transplant surgery is carried out to replace the patient's ailing kidney with the donor's healthy kidney. It requires the surgeon to place the new kidney inside the patient's lower abdomen and connect it to the patient's arteries and veins, subsequently, allowing blood to flow through this new kidney to help it make urine.

The body takes nutrients from food and converts them to energy. After the body has taken the food that it needs, waste products are left behind in the bowel and in the blood.

The kidneys and urinary system keep chemicals, such as potassium and sodium, and water in balance, and remove a type of waste, called urea, from the blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys. Kidneys also regulate fluid and acid-base balance in the body.

Procedures may vary depending on the patient's condition. Generally, a kidney transplant follows this process:

The surgery is performed while the patient is asleep under general anesthesia.An intravenous (IV) line is started in the patient's arm. Additional catheters may be inserted in the neck and wrist to monitor the status of the heart and blood pressure, as well as for obtaining blood samples. Alternate sites for the additional catheters include the subclavian (under the collarbone) area and the groin.If there is excessive hair at the surgical site, it may be clipped off. A catheter is inserted into the bladder.

The patient is then positioned on the operating table, lying on the back. A tube is inserted through the mouth into the lungs and attached to a ventilator that will breathe for thepatient during the procedure.The anesthesiologist continuously monitorsthe heart rate, blood pressure, breathing, and blood oxygen level during the surgery.The skin over the surgical site is cleansed with an antiseptic solution and an incision made into the lower abdomen on one side.

The donor's kidney is inspected prior to implanting it and thenplaced into the abdomen. A left donor kidney is implanted on the right side while a right donor kidney is implanted on the left side as this allows the ureter to be accessed easily for connection to the bladder.The renal artery and vein of the donor kidney are sutured (sewn) to the external iliac artery and vein.After the artery and vein are attached, the blood flow through these vessels is checked for bleeding at the suture lines.The donor ureter (the tube that drains urine from the kidney) is connected to the bladder.The incision is closed with stitches or surgical staples and thoroughly dressed with sterile bandage.

Deceased-donor transplantation

Living donation typically occurs among persons who know each other;whereas deceased donation is generally anonymous. Allocation of organs from deceased donors is based on a waiting list system, with special priorities given to the following:

  • Pediatric recipients (to minimize the impact of chronic renal failure on growth)
  • HLA zero-mismatch pairings (because of their documented improved graft survival rate)

Donors positive for hepatitis B core antibodies are routinely paired with recipients who have documented hepatitis B immunity as a result of immunization or prior infection. Kidneys from donors with chronic hepatitis C virus infection are frequently transplanted into recipients with hepatitis C and minimal hepatic damage and likewise.

The donor operation is now typically part of a complex multiorgan recovery process that includes the kidneys, liver, pancreas, heart, and lungs. Organ recovery essentially involves perfusion of the involved organs with cold preservation solution.

Increased use of DCD donor kidneys and the efficient use of expanded-criteria donors (ECDs) can, to a lesser degree, increase organ availability. ECD kidneys come either from donors who are older than 60 years or from donors who are older than 50 years and have 2 of the following 3 characteristics:

  • History of hypertension
  • Cerebrovascular injury as the cause of death
  • Creatinine level higher than 1.5 mg/dL at any time

In routine use, ECD kidneys are associated with a significantly higher risk of nonfunction and delayed graft function. These kidneys are currently allocated in an expedited manner to patients who have agreed to accept these risks. They are often placed on pulsatile perfusion pumps to assess their flow and resistance to flow characteristics.

As the number of patients listed for kidney transplantation continues to increase, transplant professionals continue to search for methods of increasing the donor pool.

Renal Allograft

Kidney allograft biopsies are performed for specific clinical indications, or as part of a surveillance program (or protocol). Renal allograft dysfunction after transplantation may be caused by acute rejection (AR), chronic rejection (CR) and other causes such as recurrence of renal disease. Allograft biopsy is the "gold standard" to establish the correct diagnosis.

With improved immunosuppression, acute rejection after transplantation has become less of a problem. Rejection is usually asymptomatic, though it is sometimes associated with fever and pain at the graft site. It usually presents as an unexplained rise in serum creatinine levels and can be confirmed with biopsy. Typical biopsy findings include lymphoplasmacytic infiltration of the renal interstitial areas with occasional penetration of the tubular epithelium by these cells.

Most rejection episodes can be treated successfully with a short course of increased steroid doses. Failure to respond to steroid therapy for a particularly aggressive appearance determined by biopsy may prompt a change of treatment.

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