What is Poor or slow inflow or outflow in Peritoneal Dialysis?
Poor or slow inflow or outflow of PD fluid is a problem that more frequently occurs during the initial break-in period of a PD catheter, but can occur at any time in the course of treatment. The most common cause is constipation, and the first step is to effectively clear the bowel of excessive stool. If this is not effective at resolving the problem, then other causes need to be investigated.
Discernment as to whether the flow problem is bidirectional or unidirectional (only poor outflow) helps determine the cause of the problem. Bidirectional flow problems usually indicate obstruction of the catheter lumen by clot, fibrin, or a kink or bend in the catheter. Conversely, unidirectional poor outflow suggests either of the following:
• Malposition of the PD catheter in a place where the PD fluid cannot be drained (i.e., migration of the catheter out of the true pelvis).
• Encumbrance of catheter drainage pores by tissue or viscera. Although the force of PD fluid inflow can more easily push bowels engorged with stool, epiploic appendices, omental wraps, or adhesions aside, the negative pressure of outflow results in collapse of these organs and tissues on the draining catheter.
Plain-film roentgenographic imaging of the abdomen provides diagnostic assistance in determining the presence of constipation or malposition or kinking of the PD catheter. Catheters can be repositioned by trocar or laparoscopy. By exclusion, outflow occlusion not related to constipation is most likely related to adhesions, omental wrapping, or epiploic appendices, and would require surgical or laparoscopic intervention and correction. Injection of catheters with sterile contrast by radiology can facilitate diagnosis. Inability to resolve these issues with the existing or new PD catheter would be an indication for transfer to HD.
The presence of fibrin or blood occluding a PD catheter at times can be signaled by the appearance of these substances in the PD catheter or effluent. Heparin should be added in a concentration of 500 to 2000 U/L to each dialysate exchange and continued for at least 24 to 48 hours after the effluent is clear.
A catheter obstructed with blood or fibrin can be treated with push–pull infusion of dialysate or sterile saline under moderate pressure with a 50-mL syringe. The procedure should be discontinued if the patient has any pain or cramping. Alternatively there are several anecdotal reports of success utilizing different regimens of tissue plasminogen activator (tPA) infused with sterile saline or sterile water into the PD catheter. No controlled studies demonstrate the safety or efficacy of this methodology, however.