Diverticular bleeding typically presents in elderly patients (>60 years old) and is associated with a “painless gush” of bright red blood per rectum. Patients with diverticular hemorrhage commonly provide a history of rectal bleeding that is large in volume and sudden in onset. Diverticulosis is the most common cause of acute LGIB, accounting for 42–56 % of cases (Fig. 6.1). Diverticula occur in areas of weakness within the wall of the colon. Bleeding occurs when the thin diverticular wall herniates into an arterial blood vessel (usually in the dome of the diverticulum or at its antimesenteric margin). In Western countries, 75 % of diverticula occur in the left colon, and, when right-sided diverticula do occur, they are usually associated with concurrent left-sided diverticula. Right-sided diverticular bleeding may be more severe than left-sided diverticular bleeding. Diverticular bleeding ceases spontaneously in about 80 % of cases. Although endoscopic therapies to treat a bleeding diverticulum, such as epinephrine injection and/or clip application (Video 6.1), are effective, recurrent bleeding has been reported in up to 40 % of patients despite endoscopic therapy [5]. For this reason, we advocate application of an endoscopic tattoo to mark the site of bleeding anytime an actively bleeding diverticulum is identified, so as to facilitate endoscopic or surgical localization should rebleeding occur. Recent studies have identified factors, such as nonsteroidal anti-inflammatory drugs (NSAIDs), antiplatelet drugs, and hypertension, that may be associated with a higher rate of recurrence of colonic diverticular bleeding [6].

Ischemic colitis usually manifests with abdominal pain and hematochezia, typically in an elderly patient. Historical features that raise the suspicion for colonic ischemia include small to medium volume passage of blood per rectum and antecedent hypotension. The colitis tends to be segmental (Fig. 6.2) and more commonly affects areas of the colon where the blood supply from two vascular territories do not overlap (“watershed areas”), such as the splenic flexure (Video 6.2). The likelihood of colonic ischemia as the cause of hematochezia also increases in patients who are critically ill or have a history of severe peripheral vascular disease. A common clinical scenario for the occurrence of colonic ischemia is in the critically ill patient who is in an intensive care unit and who suddenly develops hematochezia. Obtaining an accurate history regarding current medications (e.g., vasopressor therapy) and trending the patient’s blood pressure measurements in the period leading up to the episode of hematochezia are key determinants.

Bleeding vascular ectasias , or angioectasias , can present with either melena (from a right colon source) or bright red blood per rectum (from a left colon source). They more commonly present with painless bleeding in elderly patients (Fig. 6.3), and the severity of bleeding is variable. Angioectasias can be acquired through aging and their formation has been associated with chronic renal failure as well as aortic stenosis. Angioectasias are flat lesions in the GI tract and, as a result, can be easily obscured by retained colonic material or remain hidden between the colonic folds. In these situations, the use of an endoscopic cap may help locate an actively bleeding colonic angioectasia and facilitate endoscopic therapies, such as epinephrine injection, clip application, and/or argon plasma coagulation (Video 6.3). Angioectasias should be suspected in patients with recurrent overt LGIB where the source of bleeding has not been identified on previous colonoscopic examinations or other diagnostic studies. Colonoscopy with a good quality bowel preparation and careful examination of the colonic mucosa is essential for the detection and treatment of these lesions.

Overt LGIB due to colonic neoplasia is a relatively rare occurrence. Bleeding due to colonic neoplasia (Fig. 6.4) occurs more commonly in elderly patients and is more often a source of occult blood loss. Bleeding is usually of small volume and painless and tends to occur as a result of tumor neovascularization (Video 6.4). LGIB from colonic neoplasia can present as intermittent melena (from a right-sided colonic neoplasia) or hematochezia (from a more distal neoplasia). Factors that raise the suspicion for colonic neoplasia as the source of LGIB include a history of iron-deficiency anemia, weight loss, and a change in stool caliber.

Hemorrhoidal bleeding is a relatively common source of LGIB and can be seen in patients of any age. Small-volume hematochezia , characterized by bright red blood after a bowel movement with dripping into the toilet or streaking on the toilet paper, is most commonly caused by hemorrhoids, especially in patients under the age of 50. Hemorrhoidal bleeding tends to be of low volume and intermittent in nature and may be associated with constipation.

Anal fissures are typically associated with pain upon defecation and small volume bleeding. These may be associated with constipation and the passage of hard stools. There may also be a history of anal trauma antecedent to the episode of bleeding.

Rectal ulcers can be caused by severe or prolonged pressure and irritation within the rectum. This can be due to constipation and hard stool (stercoral ulcer) or by pressure from fecal management systems. Due to the rich blood supply of the rectum, bleeding from rectal ulcers (Fig. 6.5) can be severe if the ulcer erodes into an arterial vessel. This type of bleeding lesion may require multiple endoscopic modalities, such as epinephrine injection and clip application, in order to provide durable hemostasis (Video 6.5). The diagnosis of an anorectal source of LGIB requires a thorough examination of the anal canal, both internally and externally. A careful inspection of the external anal opening and a digital rectal exam should be performed. It is also imperative to perform a high-quality retroflexed endoscopic examination of the rectum when evaluating for potential anorectal sources of LGIB.

Inflammatory bowel disease (IBD) can present with abdominal pain and/or pain with defecation. Patients with IBD can present with either small or large volume of rectal bleeding and tends to occur in younger patients. In patients with IBD, bleeding is usually due to diffuse inflammation of the colonic mucosa, and the severity of bleeding is correlated to the degree of mucosal inflammation. LGIB in a patient with IBD may be the initial presenting symptom of the disease and may be associated with weight loss, anemia, inflammatory biomarkers, and extraintestinal manifestations or a family history of IBD.

Bleeding due to radiation proctopathy typically presents with the passage of bright red blood per rectum, which may be associated with tenesmus. A history of previous radiation exposure (i.e., radiation for prostate cancer in men or for uterine cancer in women) is essential in making the presumptive diagnosis of bleeding due to radiation proctopathy.

Patients with bleeding due to NSAID-induced colonic ulceration (Fig. 6.6) can present with either melena or hematochezia. In contrast to ischemic ulcers, NSAID-induced colonic ulcers may be isolated and can occur in any part of the colon. NSAID-induced ulcers generally are clean-based and resolve following cessation of the offending drug (Video 6.6).