Peritoneum is a thin, semipermeable membrane that forms the inner lining of abdominal cavity and keeps the stomach, intestines, liver and other organs in place. It has two layers which are continuous with each other. The space between these layers is the peritoneal cavity and is normally filled with small quantities of slippery fluid that helps these layers and organs to slide over each other. This membrane has rich blood supply.
What is Peritoneum ?
Peritoneum is a thin, semipermeable membrane that forms the inner lining of abdominal cavity and keeps the stomach, intestines, liver and other organs in place. It has two layers which are continuous with each other. The space between these layers is the peritoneal cavity and is normally filled with small quantities of slippery fluid that helps these layers and organs to slide over each other. This membrane has rich blood supply.
What is Peritoneal Dialysis ?
Peritoneal dialysis (PD) is the gradual transport of solutes and water across peritoneum that separates fluid that is artificially instilled into peritoneal cavity through a surgically inserted tube (peritoneal catheter; see below) and blood within the capillaries in the peritoneal membrane. It is one of the three options of renal replacement therapy for patients having irreversible advanced chronic kidney disease, the other two being hemodialysis and renal transplantation.
How are wastes and excess water eliminated during PD ?
The peritoneal cavity is filled with dialysis solution manually or using automated machines. The fluid is allowed to stay inside the cavity for 2 to 6 hours (dwell period). During this period, waste materials and excess water and electrolytes present in the blood capillaries get into fluid instilled into the peritoneal cavity. When the fluid is drained out at the end of the dwell period, the wastes are removed from the body.
What are the types of PD ?
The types of PD are: Continuous Ambulatory Peritoneal Dialysis (CAPD) in which a limited number of exchanges (see below) are done manually and Automated Peritoneal Dialysis (APD) in which multiple exchanges are done using a machine called cycler
What do you need to perform PD ?
Peritoneal catheter, connection apparatus (transfer set), dialysis solution (available in 2 and 5 liter bags and drain bag for collection of waste fluid) and cycler (if you are on APD).
What is peritoneal catheter ?
Peritoneal catheter is the most important requirement for PD. It is used to drain PD solution in and out of peritoneum. It is a long silicone rubber tube that has numerous side holes at one of its ends and one or two cuffs in the middle. It is introduced into the peritoneal cavity by a surgical technique (open or laparoscopic) in the Operating Room under anesthesia.
What is transfer set ?
It is a connection apparatus in the form of plastic tubing that helps to connect peritoneal catheter to PD solution bag. The transfer set along with a metallic adaptor will be attached to peritoneal catheter (3 days after the catheter insertion) in the ward by a sterile technique. Transfer set needs to be changed once in 6 months and whenever there is an episode of peritoneal infection.
What is PD solution bag ?
PD solution bag is a clear flexible plastic bag that contains the dialysis solution (usually of 2 liters volume). Each package contains one full bag and one empty bag; these two are connected by Y tubing. The stem of Y tubing should be connected to the transfer set during each exchange.
What is PD exchange ?
PD exchange includes connection of the stem of Y tubing of solution bag to the transfer set, drainage of the previously instilled dialysis fluid from the peritoneal cavity (takes approximately 20 minutes), flushing the tubing to remove residual air from the tubing, instillation of the fresh solution into the peritoneal cavity (takes approximately 10 minutes) and disconnection of the stem of Y tubing of solution bag from the transfer set. The bags are kept at different levels during the exchange so that drainage and instillation occur by gravity.
What is dwell time ?
Dwell time is the period during which the dialysis solution remains inside the peritoneal cavity. Dialysis takes place during this period. Usual dwell time will be 4 to 6 hours. With APD, the dwell time is shorter and set by the machine.
When will dialysis be started through peritoneal catheter ?
The peritoneal catheter insertion wound needs two weeks’ time for healing. Intraabdominal pressure will increase when fluid is instilled into the peritoneal cavity; the increase will be much higher when the patient is ambulant and this will interfere with the healing of the wound. Therefore PD will be started 2 weeks after catheter insertion. Hemodialysis will be continued as before during this period.
If the patient requires initiation on PD before this time period for medical reasons, a cycler will be used and PD will be done when the patient is lying.
Who are the candidates for PD ?
Anyone with end stage renal disease can undergo PD. Some patients choose it for convenience. PD is specifically recommended for patients having vascular access problems and poor cardiac function.
Are there any contraindications for PD ?
Patients with congenital or acquired defects in the peritoneum (hernias) cannot undergo PD unless these defects are repaired. Patients with active intraabdominal infection or those who have undergone major intraabdominal surgery in the recent past will have to wait for peritoneal catheter insertion until infection subsides or the wounds heal.
Is PD as effective as hemodialysis?
PD is as effective as hemodialysis in clearance of wastes; however it requires longer time for clearance of the same amount of waste.
May I know more about APD ?
APD is done in lying position. The initial connection and the final disconnection are done manually. Filling and drainage are done by the cycler; peritoneal catheter will be connected to the cycler until it is disconnected manually. The patient cannot move around during dwell (in CAPD, the patient can move around and perform routine activities during dwell). It is preferably done during sleep. It is easier to perform and the risk of infection is less as manual processes are less. It also improves clearance of wastes but it is more expensive.
Who will do PD ?
The patient or his close relative will do PD. The person chosen by the patient for doing PD will be trained by NU Hospitals Nephrology team to perform the exchanges using sterile technique when they get admitted for initiation on PD (two weeks from the time of catheter insertion). The patient will be discharged once the team is convinced that the person is capable of performing PD as advised.
Where can I perform PD exchange ?
You can perform the exchange in your home or at your work place; but make sure that the area is clean and not crowded before starting the exchange.
What are the complications of PD ?
Complications of PD include fluid leak through the abdominal wall, abdominal wall hernia, weight gain and obesity, tendency for increased blood sugar levels, reduced drain and infection of the peritoneal cavity (peritonitis). Among these, peritonitis is the most important complication; it is preventable and mostly the result of break in aseptic technique while performing an exchange. Over a period of time, there may be reduced function of peritoneum resulting in poor clearance of solutes. Such a complication will require switch over to hemodialysis if the function cannot be improved. It is worthy to note that residual kidney function is maintained for a longer period in patients on PD than in patients on hemodialysis.
If you have opted for PD, please go through Public Information Brochure on “How to Perform PD Exchange”
Reference
Handbook of Dialysis, Fourth edition, John T Daugirdas
