Thank you for your query. I understand your concern. A rectal bleeding could be caused by: 1)hemorrhoids 2)fissures 3)tumor/polyps 4)inflammatory bowel diseases 5)infection Based on his symptoms, medical history, I would primarily rule out a Hemangioma. These are benign tumors that commonly occur on skin, liver, intestines (but can occur anywhere in the body) and may lead to bleeding. This could be what his doctor meant by saying cluster of veins . A benign polyp could also be a possibility in his case. I would do a colonoscopy, endoscopy CT scan of the abdomen, blood work( to check for clotting disorders, liver function problems). Chest x-ray, I would also elicit a complete personal & family history with a thorough physical exam. I do not think that an acquired respiratory condition lead to this. Instead, I feel that it could have been an isolated incident. Most Hemangiomas of the intestine can be treated surgically with a good prognosis. The same goes for polyps. If a malignant growth has been detected, the extent & severity should be assessed & a treatment regimen made. This may involve surgery, radiation & chemotherapy. Prognosis depends on staging of the tumor Infections, fissures, hemmorhoids can be treated promptly & have an excellent prognosis. Hope this helps. Wish you both good health Please get back to us for further clarification.