This condition is usually only a part of much more extensive tuberculosis. There is often a coincident tuberculosis of the kidney and ureter (see above). The vesiculae seminales, vas deferens, and testicle are frequently affected, and the bladder affection is often due to propagation from the testicle.

The tuberculosis is in the form of ulcers of the mucous membrane which at first are circular, but acquire various shapes by coalescence (Fig. 445). The ulcers are mostly superficial and their edges very slightly raised, the latter having a pale colour so that the ulcer is surrounded by a whitish zone. The disease begins by the formation of tubercles in the mucous membrane. These break down and form ulcers, which continuously extend by the further tuberculosis of their walls and the breaking down of the infiltration. The general appearances of these ulcers are very well shown in the annexed figure from Virchow's work on tumours. Their superficial character renders them liable to be overlooked.

Fig. 445. - Tuberculosis of the bladder. Many round or serpiginous ulcers are shown. These are superficial, but are denned by their white edges which represent recent tubercles. There are several white spots, indicating tubercles which have not yet ulcerated. (Virchow).