Rectal cancer vomiting is not contagious. The vomiting in rectal cancer is primarily due to the growth of a tumor in the intestine that becomes too large, which then induces intestinal obstruction, causing the patient to vomit and be unable to eat. Furthermore, the vomit is not contagious, and rectal cancer itself is not a contagious disease. For patients with rectal cancer, it is essential to relieve the obstruction as soon as possible and to arrange surgery promptly. If sphincter preservation is possible, it should be attempted. Also, patients with rectal cancer should undergo a pathological biopsy to determine the type of cancer and whether it has spread. Patients with rectal cancer also need to be on a full-liquid diet. Foods with residues should be avoided as much as possible to not easily induce intestinal obstruction, leading to electrolyte disturbances or even causing the body to go into shock. Thus, it is crucial to pay sufficient attention to these issues.