Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry for this concern for your cat. It actually doesn't take much to trigger vomiting in this species so I don't worry too much about it if the vomiting is fairly intermittent. However, if it's persistent and chronic, then there may be a few possible explanations, depending on the age of the cat.
1. The first thing I'd probably consider would be Inflammatory Bowel Disease (IBD) for a cat this age.
There is usuallya history of intermittent vomiting in these cats which worsens into a flare-up although this isn't true for all cats. There cats are rarely losing weight (unless they're older when the disease develops) or showing other signs...they just vomit usually secondary to inflammation in the gastrointestinal tract.
Blood work would be normal, in most cases. Even an ultrasound wouldn't necessarily pick it up; it would take biopsies to diagnose. Obviously, most owners don't want to pu ttheir cats through this procedure, which is understandable.
Response to steroids can often be very useful in diagnosing IBD but there is usually a dietary component to this problem as well. Feeding grain free may help in some cases but often you have to feed more hypoallergenic diets such as Z/D (from your vet), or Natural Ba***** *****mited Ingredient Diets, Nature's Variety Instincts line, Evo duck or venison, Nature's Variety Frozen Raw Medallions (I recommend that they be zapped in the microwave for 10-15 seconds on each side).
Sometimes this is a trial and error process---finding the food that your cat will eat as well as one that helps with the problem.
Additionally, probiotics such as Forti Flora (found at many local pet or grain stores or online) given every day may be helpful.
For severe IBD cases, I recommend the following as well:
a. l-glutamine500mg/day crush in food which is available at health food stores oronline.
b NuCat Senior which is a supplement which containsanti-oxidants.
c. Vitamin D3 1,000 IU day.. but not calcitriol.This amount of Vit D3 is not dangerous to cats
2. Systemic disease such as problems with the kidneys or liver or pancreas; blood work is usually pretty diagnostic in these patients.
If Sammy were my cat or my patient, I'd approach the situation by changing her food as I mentioned above since this is a relatively simple thing to do. I'd also give her a daily probiotic. If you don't see improvement by several weeks, then a vet visit might be prudent.
I hope this helps. Deb