Not all patients will have black stools, if the patient’s bowel cancer has broken and bleeding on the surface of tumor, the patient may have black stools. Because the color of blood will turn black after being digested and absorbed inside the intestine, so the patient’s stool will show black phenomenon, that is, black stool. If the bowel cancer is relatively early or there is no ulceration or bleeding on the surface of the bowel cancer, the patient’s stool will be yellow and will not be black stool. Bowel cancer is more common in the large intestine, for example, there are tumors in colon or rectum, and most of the patients have frequent stools, loose stools, or even black stools or bloody stools, etc. Generally, it is necessary to go to the hospital in time to have an examination, including colonoscopy, abdominal and pelvic CT examination, etc. Usually, it is recommended to have surgery after a clear diagnosis.