Greetings. Sorry you have to be here but you are in good company, even if I do say so myself.
I remember those days of panic! You have my sympathies. The doctors instructions were vague, your kid is hurting/vomiting/bleeding, you don't want to do the "wrong" thing...
I can share with you what we have learned from experience and from medical advice we've gotten but please understand you always need to check things out with his doctor or NP if possible. When in doubt, call - even if it's the middle of the night. It's OK - you're new to all this and even seasoned parents are uncertain about this stuff most of the time. Better a call to GI and trip to ER that's unneeded than you end up with a true medical emergency that requires 911. If you have no or poor insurance then you are in a really tough place when faced with these decisions. I would make sure your GI knows this and remind them when they start telling you to go to ER so they can take that into account.
I can tell you the short answer based on what you've shared.
1. If the pain is so bad he can't stand up straight or walk or talk you go to ER
2. If he has some belly pain, diarrhea and is vomiting you call ped GI if he is unable to keep any fluids down and you have no reason to suspect a viral illness
3. If he has bad belly pain, he is not passing any gas, has definitely not passed any stool for 2 days and is vomiting you definitely call ped GI.
You are going to spend a lot of time biting your nails and playing the "watchful waiting" game. I personally hate that game but it really is true that only time will answer some questions.
Now for the really long version.
Evaluating belly pain is tricky. It can be referred pain from another part of the gut, it can come and go, it can mean appendicitis not IBD, it can just be really bad gas. For my son, pain from constipation is usually along his lower ribcage, presumably because his transverse colon is getting stretched by all the stool in it.
What I learned to do is to look at both his behavior/signs and what he is saying/symptoms.
The difference between signs and symptoms is that the first can be objectively measured or observed. A 102 fever that has been taken with a thermometer is a sign. Complaints about feeling feverish are symptoms - subjective things that the patient reports but that cannot necessarily be measured by someone else. When it comes to pain, signs include increased BP, heart rate and breathing. Symptoms are the patient's description of severity, location and character. So you want to look at signs as a way of helping you to evaluate the symptoms. When you talk to the doctor on the phone they are more focused on signs than symptoms - something that may be helpful to you when talking with them.
Keep in mind that you will almost certainly NEVER see these signs/symptoms OK? So take deep breaths. And do NOT tell your kid this stuff.
You probably need to go to ER if he is having pain severe enough that he cannot stand upright or walk and it does not pass very quickly or is getting worse. If he is in so much pain that he cannot talk, move or respond to anything but the pain then you call 911.
Now my 16 year old can get gas so bad he has that kind of pain so we don't necessarily jump in the car and run to ER when that happens. But that's because he has several years experience to draw on and is older now and is a pretty good judge of when he needs to go to ER and when it's just gas. When he was 11 we called ped gi and headed for ER when he had pain that bad. Sometimes it was gone by the time we got to ER at which point we usually turned around and went home. If it wasn't then we went in and they did their thing depending on his presentation in ER.
Vomiting bile (green stuff that isn't food) or coffee grounds (blood) should signal a trip to ER in my opinion. Vomiting bile is almost certainly going to be accompanied by severe pain because this is probably an obstruction. Coffee grounds merits a call to ped GI who will probably send you to ER.
Vomiting bright red blood = call 911
Passing large clots or lots of clots in his stool is call to ped GI and almost certainly going to ER. By large I mean the size of small marbles. Lots of clots (not liquid blood but clots) even if they're small isn't good.
Guarding - this refers to automatic or unconscious protection of his belly when he moves or when someone gets too close or he might bump into something.
Severe, unremitting diarrhea, especially if it smells bad merits an immediate call to ped GI and may end up in ER. If he has more than 10 stools in 3 hours you go to ER.
If he has a fever (100.5 or higher), complaining of belly pain with signs that he is in pain, and just seems sick to you - doesn't laugh, play, etc. - then I would definitely call ped gi unless it's clear that there's a bug going through the family and you believe that's what's going on. In that case, wait and see is probably what I would do but it would depend on how bad it was.
A fever of 103 or higher always merits a call to pediatrician or ped GI when it's an IBDer.
If they're on prednisone or immune suppresants/biologics then you call for temps over 100.5 that occur more than twice in 12 hours or for fevers over 101.5 once in 12 hours.
Any significant change in signs/symptoms usually warrants a call to ped GI but not necessarily outside of business hours. If he's always had D and now hasn't pooped for 3 days - call. If he's always had C and has persistent frequent D - call. If he's never had bloody stools and he has one - call. of those 3 examples, whether you call outside business hours depends on additional information - if he's in pain, how bad it is, if he's also vomiting, how much blood. The more signs he has that he's in distress/sick or if the problem is severe I will likely call in the middle of the night.
Ok I am going to switch topics now.
I hate to break it to you but in six years of being on pediatric IBD boards/forums I have only known a couple kids who have managed to stay in some kind of remission using dietary interventions alone. More often dietary interventions are combined with medication and the dietary intervention may allow use of 6-MP or Methotrexate instead of biologics.
I personally believe that our kids need meds - for CDers immune modulating/suppressing meds - to achieve and stay in remission. It is hard to come to grips with this when you understand the possible long term consequences of using these meds. But failing to keep CD or UC in remission carries it's own cost and not only destroys QOL but can result in permanent damage to the body that will require surgery and may result in severe disability, even death, in the future.
If you child has moderate to severe disease, when it comes to meds you will probably find yourself choosing between the known - damage to your child's body from uncontrolled IBD, loss of QOL, emotional costs - and the unknown risks of cancer or other problems in the future. Some parents don't really have a choice - their child is so sick that it is biologics or death. I remember being so scared, so sure I would never put my child on biologics. While I may have been right to be scared, getting my son into remission trumped all the possible future problems since not treating his CD could have killed him much more quickly.
If you look back 20 or so years - before 6-MP started being used to treat CD - your perspective may shift. Before that there were no options but prednisone, surgery and diet. The rates of surgery were much higher. The rates of disability were sky high. The likelihood of death from complications/surgery was much greater. Life span was shorter for IBDers by as much as 20 years.
I don't think we want to go back to that. I am not saying you are not right to be scared. I am just saying that you may not have the luxury of a choice.
Hang in there. Somehow it will all work out.