Hi, Thanks for writing in. Your father in law is having from renal disease that requires maintenance dialysis. Fluid accumulation or ascites in the abdomen is present in many people with kidney disease those who are on dialysis. This happens because of the fluid overload that is not cleared by the kidneys in a normal way. There is also abnormal balance of proteins and fluid in the body that further causes ascites. Any fluid collection within the abdomen gives rise to irritation of the peritoneum causing pain and discomfort. Few people also develop conditions involving dysfunction of liver and heart which increases tendencies of fluid accumulation. The fluid accumulation due to ascites and pain can be controlled by medications. Larger amounts of fluids require removal through drain.