In cases like this, my husband reminds me that "we are the customers" -- you're paying for a service -- doctors and basically it's time to say this isn't working, lets do a scan, xray... Sometimes they run contrast down an ng tube... DS had several xrays, including a gastrografin (sp) enema, which also sometimes helps to break things loose. In DS' case, he wasn't passing gas, nothing was coming thru and they determined thru those scans that his obstruction was further up on his abdomen and wasn't moving. He needed surgery because he had scarring adhesions from his orginal surgery an an infant.
Later after his surgery (a week), there was apparently still some very hard, tar like stool that wouldn't break loose. They tried the enema, golytely and finally the put mucomyst down his ng tube. He started to rumble -- in the middle of the night DH while rubbing DS' stomach said he actually felt a piece of hard stool move. The next morning things finally broke loose.