A wide range of underlying diseases may be the source of lower GI bleeding. Diagnosis and management differ depending on the type of bleeding (Tables 34.1 and 34.2).

In the presence of acute lower GI bleeding, clinical evaluation and resuscitation should be initiated before diagnostic evaluation [17]. This take into account the patient’s history, intake of antiplatelet or anticoagulant therapy, vascular disease, and the duration and frequency of previous bleedings. Physical examination should focus on the patient’s vital signs. In the case of clinical evidence of acute bleeding or associated high comorbidity, patients should be monitored in an intensive care unit [18]. Management includes treatment of coagulopathy, volume replacement, and transfusions before the source of bleeding is investigated. In contrast to acute upper GI bleeding, only a few risk scores have been developed to accurately forecast the outcome of a patient with acute lower GI bleeding in terms of risk of recurrent bleeding, intensive management, and mortality. Useful tests include the Bleed classification system (based on ongoing bleeding, low systolic blood pressure, elevated prothrombin time, erratic mental status, and unstable comorbid disease), clinical risk factors, and an artificial neural network [19–21].

The goals of investigations for lower GI bleeding are (1) to identify the source of the bleed and (2) to allow its permanent treatment. Endoscopic and imaging techniques (nuclear scintigraphy, computed tomography angiography, and catheter angiography) are both of interest. Today they not only play a role in localizing and identifying the cause of bleeding but also are an important part of bleeding management; each of these approaches addresses the various types of bleeding. Because only specialist centers can offer the full range of these advanced procedures, patients who specifically require them must be identified. An algorithm addresses this selection process [22] (Fig. 34.6).

Endoscopy is considered as the investigation of choice. In acute lower GI bleeding, pan–upper GI endoscopy is mandatory to rule out a potential source of bleeding in the upper GI tract [23]. The use of a nasogastric tube and gastric lavage to exclude an upper GI source of bleeding is no longer recommended. Colonoscopy has been proposed as the first-line modality for diagnosis and therapy of lower GI bleeding. Because 80 % of hemorrhages will cease spontaneously, an elective colonoscopy is often indicated after standard bowel preparation. The accuracy of colonoscopy in identifying definitively the source of bleeding varies between 45 % and 90 % [24]. In the case of acute bleeding, the timing of colonoscopy is urgent. It may be hampered by incomplete preparation or poor observation of the colonic wall as a result of a massive hemorrhage. Urgent endoscopy has been defined as occurring within 12–48 h of admission. Earlier completion of colonoscopy has been associated with greater yield and shorter length of hospital stay [15]. Rapidly purging the colon through a nasogastric tube or by mouth has been recommended to facilitate mucosal observation and improve diagnostic yield. Although urgent colonoscopy can be performed without preparation, Jensen et al. [5] reported a significant reduction in sensitivity in cases of insufficient preparation and successful treatment in as few as 21 % of cases.

Diagnostic colonoscopy can be associated with endoscopic hemostasis. Depending on the site and cause, several modalities are available, including thermal coagulation, injection of hemostatic agents, and mechanical devices. Thermal coagulation with bipolar electrocoagulation, argon plasma, and laser-mediated coagulation are the preferred methods for vascular lesions, especially angiodysplasia. Epinephrine injection and metal clips are recommended for diverticular disease or bleeding after polypectomy, with a limited risk of complication. The accuracy of hemostasis by endoscopic therapy in diverticular hemorrhage is 95 %, without morbidity, but recurrent bleeding is observed in more than 25 % of cases [25].

Rectal varices and hemorrhoids are best treated with rubber bands and a sclerosing injection.

In the case of negative upper and lower GI endoscopies, the small bowel should be investigated. Wireless capsule endoscopy is a painless tool that allows a noninvasive evaluation of the entire small bowel. A high diagnostic yield – more than 90 % – has been reported. Angiodysplasia is the most frequently observed lesion, found in up to 49 % of patients [26]. The best results were obtained in cases of ongoing obscure-overt bleeding (>90 %) and dropped to 12.9 % in cases of previous overt bleeding, in parallel with the duration of the interval since the bleeding episode began. Wireless capsule endoscopy seems to be superior to push-enteroscopy. The main contraindication is a bowel stricture. A 5 % rate of non-natural excretion has been reported.