You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is In case elective surgery of Ca sigmoid colon, which of the following should be done - and explain in detail?
The principal treatment of colon cancer is resection of the lesion along with its lymphovascular supply.
About preoperative bowel preparation Sabiston 18/e p266 writes-

"Mechanical bowel preparation with the addition of oral antibiotics was the standard of care for several decades for any intestinal surgery. More recent studies have evaluated the need for both oral antibiotics and mechanical cleansing. Oral antibiotics confer no benefit to the patient and may increase the risk for postoperative infection with Clostridium difficile. In addition, although it seems intuitive that removal of bulk fecal material would decrease the risk for anastomotic and infectious complications, the opposite is true. A recent meta-analysis showed that both of these events are not decreased and may be increased with mechanical cleansing."

Prophylactic antibiotic
a broad-spectrum parenteral antibiotics is administered just prior to the skin incision.
there is no proven benefit of using antibiotics postoperatively after an uncomplicated colectomy so must not be continued beyond the day of surgery.