PD Nurse. If there is a flow problem, always call your peritoneal dialysis nurse. She will advise you on what to do next. If there is a flow problem, its usuallly means that your pd catheter is clotted. Therefore you will need an anti-coagulation solution to be drained though your pd catheter to destory the clot. This solution can be provided by your pd nurse.
Flow problems . There are many different reasons for it. Simple Constipation can cause flow problem so make sure you have regular bowel movements. Sometimes fibrin formation in the catheter slows down the flow, talk to your PD nurse and they can flush the catheter with medicines to open it up if Fibrin clot is the problem. Worst case is Catheter malfunction and infection which mandates catheter exchange/removal!
Tell your Doctor. Tell your nephrologist asap. You want to make sure it is not a sign that the catheter is going to stop working. You can usually correct most problems without removing/replacing it.