About two weeks ago, Misty developed diarrhea for no apparent reason -- We hadn't changed her dog food or given her any weird treats or people food, and as far as we know she hadn't eaten anything that she shouldn't have eaten.  She was also acting fine -- Not acting sick at all.  Appetite still good, drinking plenty of water, still very active and playful, etc., etc.

SO, we added a small spoonful of pure canned pumpkin to her breakfast and dinner (she gets fed twice a day) and started her on probiotics.  BINGO, problem solved -- EXCEPT ...  Now she's having trouble with the OTHER end.  She's been gagging and acting like she's going to throw up.  It hasn't been severe or anything -- and she's actually thrown up only once -- but the gagging has been regular enough that my brother has started calling her Horky The Dog.  Took her to the vet and NADA -- Nothing weird in her stool, urine, blood work, stomach cultures; no infections; nothing stuck in her throat ... NOTHING.  AND, other than the gagging, she's STILL acting just fine.  No inflammations, no apparent signs of illness or allergies; no skin, hair, eye, etc., issues; still as alert, playful and pushy as ever.  Took her off the probiotics and pumpkin, and no change.  

Misty HAS been on a lowfat dog food for a few months due to an earlier, suspected case of pancreatitis, and now the vet is recommending switching her to a low-ingredient dog food. The current thinking is that Misty may have a food sensitivity and it just took a while to manifest.  One of the brands recommended for her is Natural Balance.

Has anyone else dealt with this?  Does anyone else use Natural Balance?

Natural Balance is an alright dog food. Only issue I really have with it is it's all sweet potato and is really starchy. It is very similar in recipe to the American Journey brand on Chewy. You may check prices. I feed Prey by TOTW which is legume based, so less starchy. With going to a limited ingredient route it really helps to know what you're trying to limit to be able to pick one that works. Zignature has a limited line that is excellent but pricey. Merrick also has a limited line without potato.

As for the gagging, your vet did a pretty thorough check it sounds like. Sometimes sinus issues can cause a dog to gag or make a sound like gagging if they are trying to expel something like drainage or something bothering them deeper in their sinuses. Is it a gag or a reverse sneeze? Reverse sneezing sounds a little like they are trying to hock a loogie sometimes. This could be caused by allergies but might not manifest in any real irritation that you would see during a vet exam. That's a real tough one since so much came back fine.

Mishka went thru something similar last year, minus the gagging, BUT she would throw up every once in awhile. Mishka was also going thru a UTI issue around the time it started, which I tied into her situation but in all likelihood, it was coincidental. Mishka seems to indeed have some food sensitivities, I'm thinking chicken and/or too many starches. Since I had already switched both dogs food to Acana, I felt better finding a limited ingredient line (after feeding them the ocean formula for awhile) to one called Acana Singles. It's single protein, limited ingredient, and they both like it much better than Acanas Heritage line. Acana also has a little program going on where if you save your receipts (they provide a small envelope) and buy I think it's 9 bags (I'd have to check to be certain, though) then they give you a "coupon" for a free bag. It's something atleast! LOLOL.

Her gagging though must be something. Does it happen at just any given time, or does it occur more after eating, or playing, or running, etc.?

The gagging was happening MOSTLY right after she woke up from sleeping, but it also happened seemingly randomly and for no apparent reason.  We considered that possibly it was reverse sneezing, or maybe even kennel cough or something more serious with her breathing or esophagus, but it didn't seem likely given how she was acting, etc.

Right now, though, she seems to be cured!  The vet recommended giving Misty a half tablet of Prilosec with her dinner that night, putting her back onto regular probiotics and pumpkin, and also transitioning her to a limited ingredient dog food.  We took the vet's "limited ingredient dog food list" to the pet supply store and checked our options. I was originally considering Natural Balance because it's easy to find and somewhat affordable. (Thank you for pointing out the potato issue, Jenn!) One of the other brands on the list was Venture by Earthborn Holistics. The pet supply store DID have Venture and it wasn't too outrageous in price.  Some VERY interesting ingredients in this brand.  One food even had squid!  Also no grains or potatoes.  

So, we picked up a small bag of Venture Rabbit & Pumpkin to start Misty on a slow transition and we sprinkled a bit on her regular kibble for dinner.  Wow, she LOVED it!  She also didn't have trouble taking the half-tablet of Prilosec. She was a very happy doggy after that, especially considering all of the poking and prodding she had to endure at the vet.  She barely gagged at all the first night, and last night and this morning she hasn't gagged at all.  

Funny thing is, about an hour after eating dinner and having the Prilosec, we were all sitting around watching TV and Misty let out an absolutely colossal FART. Really, it was epic.  Didn't smell too great, either.  But then she let out a big sigh and seemed very happy and content afterwards.  Maybe that was her system announcing its recovery...?  Not sure.  I'm just happy she seems to be cured for now.