This question is a little out of ’left-field’, I think, but I will give it a short answer.
Ascites is the name used for the collection of fluid inside the abdominal cavity. Though it is most commonly associated with liver disease or with advanced cardiac failure, it certainly does occur in various types of kidney disease – in particular, the nephrotic syndrome. But, of course, by the time the patient requires dialysis, kidney function has already been effectively lost – else why is the patient on dialysis —and any remaining ‘residual renal function’ in patients with nephrotic syndrome is usually very rapidly lost once dialysis starts. As a result, ascites (which, in nephrotic syndrome, results from excessive urinary protein losses and a resulting low blood protein (albumin) level) is rarely an issue. It would be uncommon indeed for nephrotic ascites to persist to any degree or for any length of time once haemodialysis had started.
Though there is a (rare) condition where abdominal fluid accumulation can persist in patients who have first undergone peritoneal dialysis but who have subsequently transferred to haemodialysis, this is (again, I stress) a rare problem.
Most abdominal swelling in haemodialysis patients is probably due to things other than renal disease or a dialysis-related ascites.
Some patients may have enlarged kidneys (for example, patients with polycystic kidney disease) while others may have various forms of associated or coincidental liver disease which may be complicated by either liver (or spleen) enlargement and/or ascitic fluid accumulation. Severe cardiac failure can cause ascites, that is true, but it would be rare for this to be uncontrollable by fluid removal and volume management (with or without albumin administration) once the patient is dialysis-dependent. Various malignancies, if associated with an abdominal spread of the disease, may also cause ascites – but this is independent of the kidney disease or the dialysis therapy.
Finally, and most commonly, I suspect the abdominal swelling you may have noticed relates to the frequent problem that many (if not most) dialysis patients face … chronic constipation. This is most often due to a mixture of causes but which might include (1) medication effects eg: binders; (2) rapid fluid shifts which ‘dehydrate’ the bowel content during dialysis and solidify the faecal content of the bowel; (3) the intrinsic renal disease, most specifically and commonly diabetes, which damages small blood vessels and nerves in the wall of the bowel leading to what is called an autonomic neuropathy - a condition frquently seen in diabetics where there is paralysis of the normal mobility (motility) of the bowel which leads to stasis (loss of forward movement of bowel content) and dilatation (lax overstretching) of the bowel wall.
Ascites as a feature of dialysis per se, is not something that we would usually encounter or expect. The presence of significant abdominal swelling raises the question of ‘why’. The answer would rarely be expected to lie in direct relationship with the dialysis therapy and would uncommonly be due to ascitic fluid accumulation but, ‘nine times out of ten’ (an Aussie expression for commonly), would be due to the bowel issues – with or without diabetes – as I have described above.