Cancer that originates in the rectum, the lower part of the large intestine just below the colon. Colon and rectal cancers are often jointly called colorectal cancer. Most cancers of the large intestine grow slowly; therefore, colorectal cancer can often be cured with early detection and treatment.
A cancerous growth in the rectum, the final segment of the large intestine, may have a genetic component in some instances. Specifically, the inherited condition known as familial adenomatous polyposis, characterized by the formation of numerous polyps in the large intestine, elevates the risk. However, the exact cause is often unknown. Diet-related factors, such as high consumption of meat and fatty foods and low intake of fiber, could also contribute to the risk. Rectal cancer is most frequently diagnosed between the ages of 50 and 70.
Initial signs of rectal cancer often include rectal bleeding while having a bowel movement, as well as diarrhea or constipation. As the condition progresses, pain may develop. If not addressed, the cancer can lead to serious bleeding and pain, and could obstruct the intestine, blocking the passage of feces. The cancer also has the potential to metastasize to other organs.
Rectal cancer might be suspected if a fecal occult blood test, which checks for concealed blood in the stool, yields a positive result. It can also be discovered during a rectal exam and confirmed through proctoscopy or sigmoidoscopy, which are internal inspections using either a rigid or flexible viewing device, along with a biopsy, where a small tissue sample is removed for microscopic evaluation.
Treatment typically involves surgery. For a tumor located in the upper part of the rectum, both the affected segment and the terminal portion of the colon are excised, after which the two remaining ends of the intestine are stitched together. To aid in the healing process, a temporary colostomy might be performed, rerouting feces through a surgically-created opening in the abdomen. If the tumor is in the lower rectum, the complete rectum and anus are removed. In this scenario, due to the absence of a natural exit for feces, a permanent colostomy is established.
Radiation therapy and chemotherapy may supplement or replace surgical intervention. The prognosis largely hinges on the extent of the cancer when treatment begins.