There are a number of different operations that can be done depending on where the cancer is within the large bowel and on the size of the cancer.

Usually the piece of bowel containing the cancer is removed together with some apparently normal bowel either side of it. The two ends of the remaining healthy bowel are then joined together (this is called an anastomosis). During the operation the area around the growth will be examined for signs of disease. As part of this examination some of the nearby lymph glands (lymph nodes) will be removed so they can be examined under the microscope and checked for signs of cancer spread.

If the cancer is very large at the time of operation it may not be possible to remove it. If this is the case the surgeons will often do a bypass operation, cutting and rejoining normal bowel either side of the tumour. This prevents any blockage of the bowel developing due to the cancer and reduces symptoms.

If for some reason the normal bowel cannot be rejoined it can be brought out onto the skin of the front of the abdomen. This is called a stoma and a bag is worn over it to collect the stools. Sometimes the stoma is only temporary, for a few months, and a further operation to rejoin the bowel can be done later. Sometimes, however, the stoma is permanent.

If the cancer is in the colon, then an operation called a colectomy is performed. This involves removing the part of the colon where the cancer is, as described above. Depending on which part of the colon is involved, different names are given to the type of colectomy which is needed. A hemi-colectomy is where half of the colon is removed (this can either be on the left or on the right).A sigmoid colectomy is where the final part of the colon, leading to the rectum, is removed. A transverse colectomy is where the transverse colon (the middle part of the colon) is removed. Occasionally it may be necessary to remove most or all of the colon and these operations are called a subtotal or total colectomy.
For a cancer in the rectum, one of two operations is usually performed: an anterior resection or an abdomino-perineal resection (APR). The choice of operation depends on where the growth lies in the rectum, the closer it is to the anus the more likely it is that an APR will be necessary.

An anterior resection involves removal of the first half or two thirds of the rectum together with the lower part of the colon. The colon and remaining rectum can then usually be joined up again without the need for a permanent colostomy. An APR involves removal of the lower part of the colon, the whole of the rectum and the anus. Because of this a stoma is always needed after an APR and it is permanent.

The tests your father will have before his operation will mean that the surgeon will have a good idea of the type of surgery which he is likely to need. So your father should be able to discuss the possible options with his medical team before he has his operation.