Final answer:
The nurse's most appropriate action when peritoneal fluid is draining slowly and the patient's abdomen is increasing in girth is to reposition the patient to facilitate drainage.
Step-by-step explanation:
If a nurse observes that peritoneal fluid is draining slowly and that the patient's abdomen is increasing in girth during peritoneal dialysis, the most appropriate action would be B) Reposition the patient to facilitate drainage. This is because repositioning can help overcome gravity-related issues that might be hindering fluid drainage. Advancing the catheter further or infusing additional dialysate could increase the risk of complications and should only be done after careful evaluation. Aspirating with a syringe is typically not recommended as it may damage the catheter or the peritoneal lining.