New Zealand has the world's highest rates of colorectal cancer, and it is our second leading cause of cancer death. The formation of a "temporary ileostomy" is a cornerstone of colorectal cancer care, particularly for rectal cancer. This involves dividing the small bowel, and bringing the ends up to the skin, so the gut contents flow into a bag. Although these ileostomies are only needed for 2 weeks (protecting a surgical join while healing), patients are stuck with them for much longer: 4.5 months on average. During this time patients are subject to major risks due to their ileostomy of: dehydration, kidney problems, readmission to hospital, missed doses of chemotherapy, infections, and worse long-term bowel function. We have invented a novel device which can overcome these problems. It is a pump that reinfuses the stoma output contents safely back into the large bowel. This trial will evaluate the new pump device.