Hi David, in regards to colonoscopy in IBD, you can look at surveillance with colonic disease to pick up cancer earlier OR to assess severity of mucosal inflammation / look for complications (ie. strictures) / assess response to treatment.
It seems that you're drilling down on the latter.
Still loads of variables. Things to keep in mind:
Bowel prep can precipitate "mini" flares in some people. The prep can also cause mild mucosal inflammation, which could be over called and then lead to over treatment.
Colonoscopy has a perforation risk of 1 in 1000, nasty complication. Very hard to justify scoping a really well patient who then perforates, leading to a bowel resection, and potentially multiple enterocutaneous fistula (getting close to worst case scenario - most colonoscopies are very safe and uneventful).
If someone has no symptoms at all - ie. feels great, a normal calprotectin and their bloods are fine (not just CRP, but albumin, ferritin, Hb, B12, etc) and they're not losing weight, then it would be very unlikely they would have significant inflammation. In regards to complications (ie. stricture), if it was asymptomatic, you wouldn't treat it (ie. dilate or surgery). So you have to ask yourself, why would you scope this patient? What are you likely to find, perhaps minimal inflammation, that may have been prep induced.
What if someone had been in that situation for 5 or 10 years, would you rescope them just to be sure? Difficult. If the patient (or parents in the younger ones) were a little anxious and wanted reassurance, then you would have a lower threshold. Remember that with each flare, you might be reinvestigating, unlikely someone is going to go that long without any symptoms or signs of a flare. You also need to keep in mind how severe their Crohn's has been previously, if severe, requiring strong meds, then you would have a much lower threshold to rescope an asymptomatic patient.
It is important when you say no symptoms to really explore that though, not just Question "how do you feel? Answer "okay".
In regards to repeat imaging (MRE) in asymptomatic people, again, not really a high yield. Definitely if there was any hint of active disease or complication, but a really well person with a normal calprotectin. If you had to do something just to make absolutely sure they didn't have grumbling inflammation, then a colonoscopy would be better in an asymptomatic person, much better idea of mucosal inflammation/healing.
In regards to faecal calprotectin. Really depends on the trend and the levels with previous flares and response to treatment. So, patient has severe flare with calprotectin around 700 or so, treated, feeling well, calprotectin bouncing around 50 to 150 to 50, do nothing. However, if you we're checking frequently and the trend was a slow rise (ie. 50, 95, 160, etc) then reinvestigate to ensure adequate treatment. Frequency of checking really depends upon how sick you have been, if really mild, easily treated Crohn's, then every year or 2 might be reasonable if they remain well. If really sick with slow response to treatment, then much more frequently (perhaps 3 to 6 monthly) would be more reasonable.
Clear as mud...