Peritoneal Dialysis
Anatomy of the peritoneum and positioning of the catheter
What is peritoneal dialysis, and how does it work?
Interestingly, the body has its own built in dialysis membrane: the peritoneal membrane.
This membrane lines your abdomen and organs. Its usual role is to pad and insulate them. We can use this membrane for dialysis. This is because there are pores in the membrane that act as a filter.
The dialysis fluid enters the peritoneal cavity (ie the abdomen) through a catheter. This is about as thick as a drinking straw. Usually between 1.5-2.5L litres is introduced (an “exchange”) which stays (“dwells”) for a few hours before being drained. Similar to haemodialysis, the toxins are filtered across this membrane from the body into the dialysis fluid. Excess body fluid is also carried with it.
There are a couple of forms of peritoneal dialysis:
1. Continuous ambulatory peritoneal dialysis – Patients manually exchange the fluid 3-5 times during the day
2. Automated peritoneal dialysis - Patients connect their dialysis catheter to a machine before they go to bed. All going well, the machine performs the multiple dialysis exchanges required overnight. This gives people the freedom to go about their business during the day.
How often will I need to perform peritoneal dialysis, and for how long each time?
In the beginning, a person’s kidneys are still working to some degree – evidenced by urination. Therefore only a small number of exchanges may be required each day. Gradually a person’s kidneys fail completely and they are completely dependent on dialysis. In this setting they will need full strength and consistent dialysis.
We can check how much dialysis is needed based on a few things:
· Symptoms – Symptoms of kidney failure include tiredness, itch, drop in the appetite and nausea. If these symptoms persist despite dialysis, the treatment may need alteration.
· Bloods – We monitor the waste levels such as creatinine, urea and potassium. High levels of waste imply inadequate dialysis. Occasionally we test how the peritoneum is performing. We do this by instilling the dialysate fluid and measuring how much toxin removal occurs over a four hours.
· Urine output – Patients on peritoneal dialysis tend to maintain a degree of urine output for longer than those on haemodialysis. This is an advantage because ongoing kidney function helps maintain fluid and toxin balance. Symptoms of excessive fluid include shortness of breath, weight gain and swelling in the ankles
Based on the above, peritoneal dialysis prescription can change. Each person’s membrane is different. Therefore the prescription of fluid volume, frequency, and strength of dialysis fluid that each patient uses is individualised.
What are the potential side effects or risks associated with peritoneal dialysis?
Infection – The catheter is a foreign object to the body. Therefore infections can occur anywhere from where it exits the skin (“exit site”), the catheter track (“tunnel”) or the abdomen (“peritonitis”). Prevention is the best form of cure. Therefore our patients are trained and assessed in hand hygiene and maintaining sterility during exchanges. The catheter also needs to dressed regularly, and antibacterial cream applied over the exit site. If an infection occurs usually this can be treated with antibiotics alongside the antifungal Nilstat. If cases where infection persists, the catheter can be removed.
Discomfort – As fluid fills the abdomen, this increases pressure within the abdomen. This can exacerbate any hernias, back pain and haemorrhoids. Fluid can also leak out of the abdomen through the skin if the pressure is too high. This is why it is preferable that the catheter is left to heal for a few weeks before use.
High sugar - The dialysis fluid is mostly made of sugar. This is the key ingredient in removing fluid. However this also means that each day around 100-200g of glucose is absorbed. This is like having a bag of lollies each day! It is no wonder that weight gain can become an issue, or dialysis can worsen diabetes. It is therefore important that people on dialysis maintain a healthy diet and lifestyle.
Slow drain output – Well functioning catheters will be able to run in 1.5-2L over 5-10 minutes, and drain out in 15-20 minutes. They may block for a variety of reasons including kinking or migration of the catheter. The most common cause of this is constipation, as a full bowel can bend the catheter. Therefore bowel motions need to be regular. Beware of changes that can cause constipation. These include changes to your diet (eg potassium restriction), decreased exercise, use of phosphate binders and iron tablets.
Burn-out – Caring for oneself long term can be quite burdensome. Speak to your team if you are struggling to cope with the demands of dialysis. During these times be vigilant to maintain proper technique, as lapses may cause complications. Commonly I see peritonitis in people who have become complacent with their hand hygiene.
Scarring – The constant washing in and out of dialysis fluid eventually scar ups the peritoneal membrane. Rarely, this may wrap over the bowel causing bowel obstruction.
How will my peritoneal dialysis catheter be placed, and how long will it take to heal?
Ideally the catheter is placed when dialysis is required in the next few months. This is because it usually takes 4 weeks for the catheter to heal, and potentially a few weeks longer if a hernia is also fixed at the time of surgery. In some cases the catheter can be placed in emergency situations. However this limits the volume of dialysis fluid that can be exchanged without leaking.
On the day of surgery, the exit site of the catheter will be marked. It is important that this site avoids your belt line because continuous pressure on the catheter causes irritation and potentially infection.
The catheter is then inserted by the surgeon usually under general anaesthetic. The tip of the catheter sits in the peritoneal cavity at the bottom of the pelvis. There are two cuffs in the tract. Eventually these fuse with the body’s tissue, anchoring the catheter to prevent dislodgement, and preventing bacteria from entering the tract into the abdomen causing an infection.
After placement, the catheter is flushed weekly to make sure that it is working properly until the person’s training can start.
How will peritoneal dialysis impact my daily routine and activities?
Peritoneal dialysis aims to maximise a person’s ability to function during the day, including work. This is because in many cases, the dialysis can be done at night. This compares with haemodialysis, where most people need to present to a dialysis unit three times a week for 4-5 hours each session (excluding travel time).
There is a significant investment by patients and staff at the beginning of peritoneal dialysis. This involves seeing the surgeon for assessment and insertion of catheter, and when the time comes the patient is trained in how to perform the exchanges, understanding the different types of dialysis fluids, looking after the catheter, using the automated dialysis machine, hand hygiene, monitoring weight, troubleshooting tips when travelling. The quickest I have seen a patient train is 2 days. Most take a week. Some take a couple of weeks while they build their confidence.
What do I do if I miss a peritoneal dialysis treatment?
During a person’s time on peritoneal dialysis, they will work closely with their healthcare team. Most dialysis units have a peritoneal dialysis nurse who can be contacted during the day. Some units have a dialysis nurse on call who can provide phone advice afterhours.
Please be in touch if there are any problems with the dialysis. Communication is key to the best outcome possible.
