4) Kidney disease:
The kidney produces 2 important hematological proteins called erythropoietin and thrombopoietin. They serve to stimulate the bone marrow to produce more red cells and platelets, respectively. In chronic kidney disease, the levels of both fall causing a fall in platelet count and easy bruising as well as spontaneous bleeding.
Another cause of easy bleeding and bruising in chronic kidney disease is the accumulation of urea, a by-product of protein metabolism in the body. Urea is mainly excreted by the kidney in healthy individuals and a fall in renal functions causes its levels to rise and toxicity to manifest. Urea increases bleeding time through many mechanisms and many of those are theoretical, but it is believed that the main one involves impairing the ability of platelets to stick to vessel walls.