Dog Vomits immediately after trying to eat anything

I have a 7 year old spayed Pom/Corgi that started vomiting immediately or within minutes of eating a small quantity of anything. Her symptoms began around May 2nd and at that time, she also vomited after drinking water. Her vomit was mostly foamy clear liquid. Otherwise, she didn't exhibit any other condition indicating she was suffering any medical issues, other than as the days progressed, she began to seem weaker since she wasn't retaining any food. I brought her to the vet on May 9th and after a physical exam, they only gave her an anti-nausea injection. This appeared to resolve the issue for several days, but then she relapse. Her vomit now had color, usually yellowish and foamy, but she didn't seem to vomit when drinking water. I again brought her to the vet on May 20th and they conducted a CT scan, bloodwork, and urine sample. The called me yesterday and said the CT, reviewed by an actual radiologist, showed no obvious objects, obstructions or abnormal anatomy. The bloodwork looked normal, other than I RBC level, which they attributed to dehydration. Unable to determine the cause of her vomiting, other than suggestion she might have pancreatitis, they recommended an ultrasound as the next step.  However, I'm hesitant to approve this diagnostic scan since I work in Radiation Oncology and working with CT's are part of my profession, so if a CT can't detect the condition that we feel would cause the vomiting, I don't believe an ultrasound would detect something that the CT couldn't image. A Radiation Oncologist and my brother, an ENT surgeon, both concur.  So I need advice as to what my next step should be: an endoscopy? Could it truly be pancreatitis? What about a parasite? Her weight as of last Monday was 15.4 pounds, which is about her normal weight. She has never experienced any other medical condition before and she is not on medication. Her daily diet is dry kibble, with occasional table scraps. Just before she experienced her vomiting, my father gave her a small steak bone from his plate (without my permission, and which I would not have given her due to the small size of the bone). But since the CT did not image this high-density organic material, I don't believe this is the cause of her condition.

I forgot to add that last night while she was laying next to me after trying to eat some canned dog food (after which, I let her outside for half an hour to vomit), her abdomen would occasional convulse as if she was about to vomit, even though her she was resting her head down on the couch and otherwise no exhibit any other distressing behavior. This continued for probably 10-15 minutes.

Hello - and thank you for this thought provoking question.   I didn't know the answer, having always diagnosed pancreatitis using a combination of ultrasound and various blood tests.  I simply wouldn't have thought to send a suspected pancreatitis case for advanced imaging, owing to the fact that there is a cheaper, reliable method readily available. The online Merick veterinary manual (described as 'the Bible' for medical cases) has this to say:   More advanced imaging techniques, such as.... CT or MRI, are not yet used for (dignosing) .... pancreatitis..... although this may show promise for the future.  Thus it appears that at the current time, CT may not have been assessed for its reliability in diagnosing pancreatitis, while most vets have someone quite handy at checking with the more familiar probe, and know exactly what they are looking for.  I hope that this helps.  I can only imagine the radiation oncologist and CT surgeon's eyebrows raising at this, but while most doctors are either GPs or chase a specialism, most GP vets treat up to 5 species at a level which might involve basic orthopaedic surgery, ketoacidosis, kidney stones, dental extractions vaccinations and euthanasia in one day.  I would argue that its worth them checking with whomever did the MRI (they would have access to the latest understanding), but it could simply be thst this detail isn't known yet.  Is it possible that the MRI scans aren't resolving well enough to know for sure ???  I do not know the answer to that.  I must admit that reading through the case, I was also thinking 'have they scanned the pancreas?'   I would be fascinated to hear whether  pancreatitis is found in the end (your vet may think it best to scan around the time of a 'bout').  Wishing your pom / corgi (both high-risk breeds for pancreatitis) all the best from here.

As regards to what else it could be, I would strongly reccommend asking your vet to make and refine a differentials list - its good practise to discuss it with you, especially as an owner who is interested in working things through.   I wonder whether Giardia could be on the list, or Addisons (were electrolytes taken),  or the eating of animal faeces or toxicities.  Please do let me know when you find out!

I apologize for not responding with updates sooner as multiple, successive family health emergencies transpired during the interim. The current status is that she was referred to a Internal Medicine vet at an affiliated clinic after exhausting the capabilities of my local vet clinic. A battery of tests were performed for Addison's and Pancreatitis, both of which were negative. However, the lab results indicated an extremely high level of cortisol (steroids) at 38.5 (normal is 20) which suggests Cushing's Disease. But her symptoms do not reflect any of that disease, and the vet mentioned that the test suffers up to 25% false-positive rate. Thus, he doesn't believe she has Cushing's. Other considerations are esophagitis, gastroesophageal reflux disease, esophageal strictures, and/or abnormal function of the distal esophageal sphincter. Also, it was noted her small intestines had slight thickening of portions along its length; an invasive biopsy would be necessary to determine the potential cause of that. To rule some of the less complicated diagnosis, both Rx and OTC medication will be administered for GERD and esophagitis. As she's now down to 6 pounds from 16.4 pounds four weeks ago, a special high-granularity, low-fat, wet food will be prescribed that would hopefully be able to transit through any esophageal strictures. If she refuses to eat that (being picky), then I'm to continue feeding her the soup "gruel" that I started her on last week that she's to be able to ingest that occasionally without vomiting. The next diagnostic imaging recommend is fluoroscopy to visualize the intake of food throughout the upper gastrointestinal tract. This is where it stands today.