Inflow and outflow pain in Peritoneal Dialysis

What is Inflow and outflow pain in Peritoneal Dialysis?

• Occasionally, patients complain of pain upon infusion or drainage of PD fluid.
• Infusion pain is a frequent problem in peritoneal dialysis (PD), and can markedly vary in intensity and risk. 
• Among the many etiologies are peritonitis and other inflammatory processes of the peritoneum, accidental infusion of air, and acidic pH of the dialysate, and expired dialysate with high concentrations of glucose degradation products or GDPs, extreme temperatures of dialysis solution, hypertonicity of the solution, rapid infusion rates and high pCO₂ levels in the peritoneal dialysis fluid. 

• Timing and duration of the pain usually provide the diagnostic clues as to which of the aforementioned issues are causative and therefore crucial to discerning appropriate treatment.
• Transient pain related to inappropriate temperature can be adequately managed with proper patient instruction. Pain related to the lower pH of the PD solution is also transient in nature, given the rapid increase in the PD fluid pH to physiologic levels.
• The effect of constipation on expansion of intestinal diameter and resultant crowding of the viscera around the catheter should not be minimized as a cause of either fill or drain pain.

• Drain pain and overfill are two complications of peritoneal dialysis (PD) that get very little attention in the published literature.
• A “PubMed” search reveals no articles about PD with ‘drain pain’ in the title and only one addressing ‘overfill’ in the sense of an excessive intraperitoneal dialysate volume.

• Infusion pain also results from stretching of the intraperitoneal structures as in the case of compartmentalization due to adhesions.
• Infusion pain can result from infusion of an inappropriately cool or warm PD solution, peritoneal sensitivity to the lower than physiologic pH of PD solution (i.e., 5.2 to 6.4), visceral sensitivity to a directed jet stream of PD fluid from the PD catheter, or a malpositioning of the PD catheter against the viscera.
• Discomfort during drainage (“drain pain”) of PD effluent usually relates to a siphoning effect on the viscera or peritoneum and may therefore also relate to catheter positioning.
• The use of neutral pH PD solutions can address this issue if available. Although addition of bicarbonate to the PD solution prior to peritoneal infusion can also help reduce pain, introduction of any exogenous substance to the PD fluid theoretically may increase infection risks.
• Alternatively, patients can leave a small residual volume of PD fluid in the abdomen at the end of the drain phase of the exchange.

In peritoneal dialysis (PD), inflow and outflow pain refers to the discomfort or pain experienced by some patients during specific stages of the dialysis procedure. Peritoneal dialysis is a method of removing waste products and excess fluids from the body by using the peritoneal membrane, which lines the abdominal cavity, as a natural filter.

During a PD session, there are two main phases: the inflow phase and the outflow phase.

1. Inflow Phase: This is the initial phase of the PD procedure, where the dialysis solution (dialysate) is introduced into the peritoneal cavity through a soft, flexible tube called a catheter. The catheter is typically inserted into the abdomen through a small surgical procedure. The dialysate is allowed to dwell inside the peritoneal cavity for a prescribed period, during which waste products and excess fluids are exchanged across the peritoneal membrane.

Inflow pain may occur during the introduction of the dialysate into the peritoneal cavity. Some patients may experience discomfort, mild cramping, or a feeling of fullness during this phase. The intensity of inflow pain can vary from person to person and may improve with time as the patient gets accustomed to the procedure.

1. Outflow Phase: After the prescribed dwell time, the spent dialysate, now containing waste products and excess fluids, needs to be drained from the peritoneal cavity. This is the outflow phase. The patient lowers their drainage bag or container below the level of the abdomen, and gravity allows the spent dialysate to flow out through the catheter.

Outflow pain may occur during the drainage process. Some patients may experience discomfort, abdominal cramps, or a pulling sensation as the dialysate is being drained. Like inflow pain, the severity of outflow pain can vary among individuals and may improve with time and experience.

The inflow and outflow pain in peritoneal dialysis can be managed by making adjustments in the dialysis prescription, such as the dialysate volume or dwell time. Additionally, using warm dialysate can sometimes alleviate discomfort. It’s essential for patients to communicate their symptoms to their healthcare team so that appropriate modifications can be made to improve their overall dialysis experience.

If inflow or outflow pain is severe or persistent, or if there are other concerning symptoms, patients should contact their healthcare provider promptly to rule out any complications and ensure that the peritoneal dialysis treatment is optimized for their specific needs.

A survey of 293 automated Peritoneal Dialysis (APD) patients in 6 sizeable Peritoneal Dialysis programs in the Canadian province of Ontario, shows that 72 or 25% of these patients are using a tidal modality of Peritoneal Dialysis, specifically because of drain pain

• This residual volume serves as a buffer to the inflowing dialysate and reduces the tugging sensation associated with the last phase of the drain. Use of “tidal” therapy with APD accomplishes the same effect. Tidal PD can also reduce nightly alarms during cycler treatment related to sluggish PD catheter outflow.
• However, caution should be taken to avoid too large of a residual volume so as to avoid a total IP volume that may cause clinical problems. Effective treatment of constipation should always be undertaken as a simpler means to relieve either fill or drain pain prior to considering leaving a residual volume after each exchange.

If you are experiencing inflow or outflow pain during peritoneal dialysis, it’s important to communicate with your healthcare team. They can evaluate the underlying cause of the pain and make necessary adjustments to the dialysis procedure or treatment plan to help alleviate your discomfort.

Timing and duration of the pain usually provide the diagnostic clues as to which of the aforementioned issues are causative and therefore crucial to discerning appropriate treatment. Transient pain related to inappropriate temperature can be adequately managed with proper patient instruction.

Pain related to the lower pH of the PD solution is also transient in nature, given the rapid increase in the PD fluid pH to physiologic levels. The use of neutral pH PD solutions can address this issue if available.

Although addition of bicarbonate to the PD solution prior to peritoneal infusion can also help reduce pain, introduction of any exogenous substance to the PD fluid theoretically may increase infection risks.

Alternatively, patients can leave a small residual volume of PD fluid in the abdomen at the end of the drain phase of the exchange.

This residual volume serves as a buffer to the inflowing dialysate and reduces the tugging sensation associated with the last phase of the drain. Use of “tidal” therapy with APD accomplishes the same effect.

Tidal PD can also reduce nightly alarms during cycler treatment related to sluggish PD catheter outflow. However, caution should be taken to avoid too large of a residual volume so as to avoid a total IP volume that may cause clinical problems.

Effective treatment of constipation should always be undertaken as a simpler means to relieve either fill or drain pain prior to considering leaving a residual volume after each exchange.

• Occasionally, patients complain of pain upon infusion or drainage of PD fluid. Infusion pain can result from infusion of an inappropriately cool or warm PD solution, peritoneal sensitivity to the lower than physiologic pH of PD solution (i.e., 5.2 to 6.4), visceral sensitivity to a directed jet stream of PD fluid from the PD catheter, or a malpositioning of the PD catheter against the viscera.
• Discomfort during drainage (“drain pain”) of PD effluent usually relates to a siphoning effect on the viscera or peritoneum and may therefore also relate to catheter positioning.
• The effect of constipation on expansion of intestinal diameter and resultant crowding of the viscera around the catheter should not be minimized as a cause of either fill or drain pain.