Passive hyperemia occurs in consequence of obstruction of the veins by tumours in the abdomen or otherwise. Sometimes in such cases the veins of the mucous membrane undergo great dilatation and become varicose, especially in the floor of the bladder, giving rise to Vesical haemorrhoids. The dilated veins may even obstruct the orifice of the urethra, and there is sometimes haemorrhage from them.

Haemorrhage from the bladder occurs also in consequence of the irritation of calculi, from tubercular ulcers, from papillary and cancerous tumours. There may be haemorrhages from the mucous membrane in scurvy, hsemorrhagic small-pox, etc. There is sometimes a haemorrhage following catheterization, and probably due to the sudden relief of pressure from the emptying of the bladder, without a sufficient contraction of the muscular coat. If the bleeding into the bladder be considerable the blood may coagulate, and may be discharged with some difficulty. Or it may mix itself with the urine, and no consistent coagulum be formed.