The problem as I see it with the term IBS, it seems so nebulous (albeit very distressing) with no real defining tests, therefore in some senses it can and does on occasion get brushed aside as psychological. Whereas Gastroparesis and Oesophageal Dysmotility are able to be tested and quantitatively measured.
I'm sure if more M.E. people, whom doctors otherwise suggest with a wave of the hand have IBS, had the gastric emptying study and oesophageal manometry tests done, GI dysmotility in a subset of this patient group would be more frequently diagnosed and therefore better treated.
I disagree that it is not useful to obtain and attach a correct diagnosis or name for specific collective symptoms and issues, as many parts make up the whole in M.E. For each separate 'mini diagnosis' (and often not so mini may I add), better management can be implemented and a better quality of life can ensue.
I often wonder when I hear of very ill M.E patients who are confined to bed, very thin and have a feeding tube, have they actually ever been tested for upper GI Dysmotility? In these cases a feeding tube into the stomach for instance will do little good if a patient has significant Gastroparesis with slowed liquid transit time. They need to have a jejunostomy (a feeding tube into the jejunum - upper bowel) because essentially the stomach is not doing its job of digesting the liquid food and moving it along for further digestion of nutrients. The patient feels sicker with nausea and possibly vomiting as the food just sits there. Also there are very effective medications which can be prescribed in conjunction with such a diagnosis.
The same goes for other diagnoses co-existing with and part of the M.E. package - like Orthostatic Intolerance or POTS. This is another frequent accompaniment of M.E. however correct diagnosis and treatment management can greatly improve QOL. Sleep disorders. Pain. Balance problems. Headaches. Food allergies. These (and many others) are part of documented symptoms frequently experienced in M.E. and for many, some measure of relief can be achieved with correct identification and a treatment strategy.
Some of these stand alone diagnoses in themselves are considered quite monumental as a sole problem in non-M.E. people, leave alone in us who seem to have so many co-existing conditions.