Well, if you can't contact a dr's office for advice on this; one fairly reliable source you can turn to is your local pharmacist. Explain the situation, ask if they know of a mild, natural based laxative... or a mild, natural, water soluble form of fibre... After my resection, I asked my GI IF I could take anything if I became backed up/constipated (had this horrible notion it might occur whilst my stitches were still fresh... pictured my sewn-up colon coming apart at the seams, as it were - thankfully it didnt' happen)
Anyway, he advised a natural, MILD, overnite laxative would be safe for me. Bear in mind, post surgery, I was completely inflamation free... colon was in the 'best' shape ever. Other things you can do is decrease eating solids... switch to liquid or soft diet only.. and increase the fluids you drink.