Urinary Bladder - Inflammation

Inflammation is one of the most frequently diagnosed lesions of the urinary bladder. Inflammation may be acute, suppurative, chronic, chronic-active, or granulomatous, depending on the predominant cell type or cell response involved. In acute inflammation, the predominant infiltrating cell is the neutrophil, though fewer macrophages and lymphocytes may also be present. There may also be evidence of edema and hyperemia. The neutrophil is also the predominant cell type in suppurative inflammation; however, the neutrophils are aggregated, and many of them are degenerative (suppurative exudate). Lymphocytes predominate in chronic inflammation; lymphocytes also predominate in chronic-active inflammation, but there are also a significant number of neutrophils—both lesions contain macrophages. Diagnosis of granulomatous inflammation, another form of chronic inflammation, requires the presence of a significant number of aggregated, large, activated macrophages, epithelioid macrophages, or multinucleated giant cells.

Inflammatory cells can be seen anywhere in the bladder, including the lumen, mucosa, submucosa, and muscularis (Figure 1). Hemorrhage, necrosis, urothelial hyperplasia, and fibrosis may be evident, depending on the lesion (Figure 2). In most instances, inflammation arises from bacterial infections or the presence of calculi. Inflammation may also be a direct consequence of chemical administration.