Constipation and rectal cancer are not directly related, and it cannot be said that constipation is rectal cancer. Patients with constipation are recommended to perfect colonoscopy to exclude organic lesions, while patients with rectal cancer can be clearly diagnosed by perfecting colonoscopy and pathology, mainly because pathology can detect cancer cells, and patients with rectal cancer are more likely to be misdiagnosed and mistreated as hemorrhoids in clinical practice, and have been treated according to hemorrhoids, resulting in repeated attacks. Finally, colonoscopy can be improved to clearly diagnose rectal cancer or anal cancer. If a patient has constipation combined with blood in stool and recurrent episodes of the disease, it is necessary to improve colonoscopy and pathological examination in a timely manner to clarify the diagnosis and timely treatment, so as not to delay the disease.