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GI Tract in Disease_Large Intestine_Lower GI Bleeding_Colorectal Cancer_Diverticulosis

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This document reviews major diseases of the large intestine, focusing on colorectal cancer, lower gastrointestinal bleeding, diverticulosis, diverticulitis, diverticular bleeding, and hemorrhoids.

<strong>Colorectal cancer</strong> is a common cancer of the colon or rectum, with a lifetime risk of about 5%. It typically develops over 10–15 years through a sequence from hyperproliferation to adenomatous polyp, high-grade dysplasia, and invasive adenocarcinoma. Patients may be asymptomatic, present with warning symptoms, or rarely have obstruction or peritonitis. Screening is recommended starting at age 45, and earlier for those with family history, inherited cancer syndromes, or inflammatory bowel disease. Common screening methods include stool-based tests, flexible sigmoidoscopy, colonoscopy, and CT colonography. Diagnosis is made by colonoscopy. Localized disease is treated with surgical resection, while metastatic disease requires chemotherapy and/or palliative care.

<strong>Lower GI bleeding</strong> usually originates beyond the ligament of Treitz, most often from the colon. It may cause hematochezia, melena, or symptoms of anemia such as lightheadedness, syncope, shortness of breath, or chest pain. Common causes include diverticulosis, angiodysplasia, ischemic colitis, inflammatory bowel disease, infection, colon cancer, post-polypectomy bleeding, and hemorrhoids. Initial management includes large-bore IV access, volume resuscitation, and exclusion of upper GI bleeding. Colonoscopy with hemostasis is often used for treatment.

<strong>Diverticulosis</strong> consists of mucosal and submucosal outpouchings, increases with age, and is usually asymptomatic. It is often found incidentally. Complications include diverticulitis and diverticular bleeding. Diverticulitis presents with left-sided abdominal pain, fever, and elevated WBC count; CT is used for diagnosis, and treatment depends on whether the disease is uncomplicated or complicated. Diverticular bleeding is usually painless and self-limited.

<strong>Hemorrhoids</strong> are swollen veins in the anal canal and are treated conservatively first, with procedural or surgical options if needed.

Keywords

colorectal cancer

lower gastrointestinal bleeding

diverticulosis

diverticulitis

diverticular bleeding

hemorrhoids

colonoscopy

adenomatous polyp

hematochezia

diverticular disease