Bladder biopsy showing cystitis cystica and cystitis glandularis. Brunn nests, cystitis cystica and cystitis glandularis frequently coexist in the same specimen. The inciting agent is usually chronic inflammation or irritation of the mucosa. In many cases, however, no cause is evident. Given their frequent occurrence in normal bladders, these changes are almost considered normal variants of bladder histology.