Why does a urinary tract infection cause delirium?

Unclear: But likely it is related to the blood brain barrier being permeable when one has an infection.

Sepsis or high fever: Urinary infections reaching the affecting the kidney become pyelonephritis which can cause very high fevers 1o5 degrees or more which can occasionally cause delirium. Also bacteria can enter the blood stream, causing septacemia which is an infection in the blood stream and allows bacteria and infection to reach the brain. Fortunately this is rare but can happen with overwhelming sepsis.

Great question: We believe delirium occurs when the brain cannot maintain its normal activities when overwhelmed by metabolic demands or other variables which exceed the brain's capacity to compensate for. We do not know why uti's precipitate delirium in vulnerable older adults. We do know fever increases the oxidative requirements of the brain, and cytokines released during infection may play a role.