Problem
A 54-year-old schoolteacher is seeing your today for complaints of passing bright red blood when she had a bowel movement this morning. She stated the first episode occurred last week. The episode today was accompanied by nausea, sweating, and weakness. She states she has had some LLQ pain for several weeks but described it as "coming and going". She says she has had a fever and abdominal cramps that have worsened this morning.
Diagnosis is lower GI bleed secondary to diverticulitis.
Task
What can cause diverticulitis in the lower GI tract?