Rectal tumour. Coloured barium X-ray of the large intestine of a patient with a rectal tumour (growth, dark, indicated by arrow). The rectum is the terminal portion of the large intestine, where faeces is stored before it exits the body via the anus. This is a villous, or folded, tumour. Treatment is with surgical removal as the tumour may be malignant (cancerous), or obstructing faeces from leaving the body. This image was produced using a double contrast barium enema. Water containing radio-opaque barium was introduced into the rectum, which was then distended by air.