What is the peritoneum?
The peritoneum is the thin inner lining of the abdomen that coats all intra-abdominal organs and the inner aspect of the abdominal wall. It consists of two layers, the parietal peritoneum that lines the abdominal and pelvic wall and the visceral peritoneum that lines the organs in the abdomen and pelvis.
How does the peritoneum help with dialysis?
The peritoneum acts as a natural filter and is used to help with the removal of waste products and extra fluid from the body. This function is usually reserved for the kidneys. In the presence of kidney failure, the removal of waste products is accomplished either via the blood (hemodialysis) or by inserting a soft tube (catheter) inside the abdomen and using the peritoneum to perform the filtering function.
How does peritoneal dialysis (PD) work?
After the catheter is inserted, it is ready for use in a few weeks. A special fluid, called the dialysate is placed inside the abdomen via the catheter and allowed to stay there for a few hours. The dialysate has a sugar called dextrose in it that makes it concentrated which then helps in pulling in the waste products and extra fluid from the body into the peritoneal cavity. The amount of time that the dialysate sits in the abdomen is called the dwell time. This is individualized by the nephrologist based on the medical condition of the patient. After a few hours, the fluid is then allowed to drain out and is discarded. A new bag of dialysate is then placed into the abdomen for a fresh dwell time.
The process of placing the dialysate and then draining it is called an exchange.
How many times does PD need to be done every day?
That depends upon the type of PD that is decided upon.
Continuous ambulatory peritoneal dialysis (CAPD) will require 3 to 5 exchanges every day. At the end of the day, an exchange is done before bedtime and the fluid is then drained upon waking up in the morning. CAPD does not require a machine and is done by hooking a plastic bag containing the dialysate to the catheter and then using gravity to drain the fluid at the end of the dwell time. Patients can be ambulatory and go about doing their daily activities while the dialysate is in the abdomen.
Automated peritoneal dialysis (APD) is usually done at night with the help of a cycler that delivers and drains the dialysate fluid during sleep.
What are the pros and cons of peritoneal dialysis?
Peritoneal dialysis is easier on the body because it is done continuously and can therefore mimic the kidney in its function. Removal of the extra fluid is gentler and therefore is less stressful on the heart. Daily activities, work and travel can be done more easily compared to hemodialysis.
PD may not be appropriate for certain individuals- these include morbidly obese patients and patients who have had previous surgeries on their abdomen.
The biggest complication with PD is peritonitis, which can be a life-threatening problem. This happens when the exit site of the catheter becomes infected or the catheter becomes contaminated during the exchanges. Most patients will have abdominal pain, fever, nausea or vomiting and some redness near the exit site. The dialysate might also look unusually cloudy. If this happens, patients may need to be admitted to the hospital for antibiotics to clear the infection. In rare circumstances, the catheter may need to be removed.
Fluid and dextrose absorption can also occur with longer dwell times. This usually leads to weight gain and bloating. A cycler might be necessary in patients who use CAPD during the night.