“Schwannomas are benign nerve sheath tumors with significant Schwann cell differentiation. They similarly affect both genders and are atypically discovered in patients in their 3th and 5th decades of life. Schwannomas most commonly involve peripheral, motor, sympathetic, or cranial nerves of the head and neck region and upper and lower extremities. Schwannomas have been found at almost every location of the body including in extremities, head, neck, retroperitoneum, mediastinum, pelvis, and rectum. Visceral locations, however, are very rare and preoperative diagnosis is challenging, as schwannomas are often confused with other neoplasms.”
Abdominal schwannomas: review of imaging findings and pathology. 
Lee, N.J., Hruban, R.H. & Fishman, E.K.
Abdom Radiol 42, 1864–1870 (2017)

Angiodysplasia accounts for 6% of cases of lower GI bleeding.

• Abnormal proliferation of venules and capillaries within submucosal layer of bowel
• Degeneration of blood vessels related to aging
• 75% of lesions in the right colon
• Colonoscopy is not sensitive for this diagnosis, identifying only 68% of cases seen on angiography
• Densely opacified and dilated draining veins, early filling veins, dilated feeding artery, vascular submucosal ‘tufts’ in the wall of the colon.
• Arterial phase images key, with venous phase less important

”While diverticulosis is the most common cause of lower GI bleeding, angioectasia is the most common vascular lesion causing lower GI bleeding and has an increased incidence with age. In the colon, angioectasia is more common in the cecum and ascending colon. On CT images, colonic angioectasia can appear as punctate or discoid foci of enhancement in the colon wall. As in the small bowel, angioectasias may be incidental findings unrelated to the cause of bleeding.”
Gastrointestinal Bleeding at CT Angiography and CT Enterography: Imaging Atlas and Glossary of Terms 
Flavius F. Guglielmo et al.
RadioGraphics 2021; 41:1632–1656

“The most frequent complication of DD is diverticulitis, and the second one is hemorrhage. Excluding ano-rectal diseases, hemorrhage secondary to DD is the second cause of bleeding of the lower gastrointestinal tract, but it is the main cause of massive bleeding up to 30 to 50% of cases. It is estimated that up to 15% of patients with DD in the colon will bleed at some point in their life, bleeding is usually painless and large, and is up to one-third of the cases massive and requires hospitalization and transfusion support.” 
Colonic diverticular bleeding. Have we identified the risk factors for massive bleeding yet?
Blancas Valencia JM
Rev Esp Enferm Dig. 2017 Jan;109(1):1-2.

“It is estimated that up to 15% of patients with DD in the colon will bleed at some point in their life, bleeding is usually painless and large, and is up to one-third of the cases massive and requires hospitalization and transfusion support.” 
Colonic diverticular bleeding. Have we identified the risk factors for massive bleeding yet?
Blancas Valencia JM
Rev Esp Enferm Dig. 2017 Jan;109(1):1-2.

“The natural history of colonic diverticula hemorrhage indicates that it is stopped spontaneously in 70 to 80% of cases, so treatment should be directed to support management, in 20 to 30% of cases specific medical treatment through endoscopic management with any of the available modalities such as: epinephrine injection, thermal or mechanical methods such as endoscopic clip or ligature, and in very few cases a radiological or surgical treatment will be necessary.” 
Colonic diverticular bleeding. Have we identified the risk factors for massive bleeding yet?
Blancas Valencia JM
Rev Esp Enferm Dig. 2017 Jan;109(1):1-2.

“Once the initial episode of bleeding stops, most patients will not recur, and only 30% will present a second bleeding episode and in this rebleeding group the risk of a new bleeding episode is very high, so surgical treatment is recommended.” 
Colonic diverticular bleeding. Have we identified the risk factors for massive bleeding yet?
Blancas Valencia JM
Rev Esp Enferm Dig. 2017 Jan;109(1):1-2.