In histology, how does ulcerative colitis typically present?

Ulcerative colitis is characterized by inflammation that is primarily confined to the mucosa and submucosa of the gastrointestinal tract. This limited involvement distinguishes it from Crohn's disease, which can affect all layers of the bowel wall (transmural inflammation) and can impact any segment of the gastrointestinal tract.

In ulcerative colitis, the inflammation leads to the formation of mucosal ulcers, but the extent remains superficial compared to other forms of inflammatory bowel disease. The primary pathological changes include extensive loss of mucosal epithelial cells and inflammatory infiltration predominantly of lymphocytes and neutrophils within the mucosal layer. While neutrophil infiltrates do occur in ulcerative colitis, they are a feature seen within the context of the mucosal inflammation rather than defining the condition.

Understanding this characteristic localization of inflammation is crucial for differentiating ulcerative colitis from other conditions, particularly when diagnosing and determining treatment strategies. The presence of mucosal ulcers and fissuring can occur but is secondary to the lact of deepest tissue involvement.