Is anal blockage a manifestation of rectal cancer? The answer could be yes, but it could also be due to hemorrhoids, or other diseases. The main common symptoms of rectal cancer include changes in bowel habits and the characteristics of the stool. There may be frequent bowel movements, diarrhea, or constipation, or alternating constipation and diarrhea, a sensation of anal heaviness, or associated with vague abdominal pain. Symptoms of abdominal pain, intestinal obstruction, and abdominal masses might also appear. When the tumor grows to a certain extent, an abdominal mass can be palpated, which might cause some compressive symptoms, possibly leading to anal blockage as one of the symptoms.