In patients suffering from chronic renal failure , the platelets usually develop a dysfunction. They are responsible for preventing small bleeds. But if they cease to function then the patient develops a propensity for small hemorrhages which usually develop spontaneously. As soon as the dialysis session is completed the platelets will function optimally for some time. If the problem goes beyond control then a particular medication is given which is a synthetic anologue of vasopressin. You should consult your nephrologist who will guide you in this respect.

As you told in your history your having dialysis two times a week can explain the cause of your bruises.An increased incidence of spontaneous bleeding occurs in hemodialysis patients which is related to several factors like heparinisation during dialysis,ongoing anticoagulation therapy and platelet abnormality of uremia.First I will tell you about heparin.It is a substance given to prevent blood from clotting.It is given in hemodialysis to prevent your blood from clotting when it is taken out of your body into the dialysis machine.The effect of heparin stays for sometime after dialysis which can be one of the factors causing your bruising.Secondly the platelets or the cells which cause clotting will be abnormal in people having kidney problems .The platelets can adhere to the dialysis machine membrane releasing other chemicals which prevent blood from clotting.As such the bruises on your body need not worry you but it is there to remind you that you are always under risk of severe bleeding.As such I would recommend you to have your blood pressure at least twice daily and any drop in your blood pressure should be carefully investigated