Undiagnosed & Worsening Episodes of Discomfort and Distress

Since she reached adulthood, our two year old chihuahua mix has had intermittent spans during which she seems physically and mentally distressed. They occur very roughly every couple of weeks and will sometimes last less than a day, though recently they seem to be lasting multiple days at a time. Normally a cheerful, engaged dog, during these periods Pepperoni will be solitary and nervous. She seems to be confused about why she feels unwell, and will shake (which she doesn't usually do, despite being a chihuahua mix) and put her tail between her legs. Usually she'll have decreased appetite as well. Occasionally during these periods she will even growl at us when we try to touch her, which, without exception, she does not do when she's feeling normal. She's had multiple blood panels done with no important findings, and we've taken her to the vet several times with no solutions. Solutions they've offered included strengthening her core (in case the culprit is back pain. Quite difficult to get a dog to do sit-ups, and she goes for healthy number of walks. The vet also didn't seem to think her back was hurting; it seemed like a guess) and medication for an irritated butt (which seemed to be bothering her once, but doesn't seem to be a chronic problem). Currently Pep is in the middle of the longest one of these periods yet. We took her to the vet for the normal symptoms, plus a very slight fever, rapid breathing, and accentuated lack of appetite (not even interested in treats). The vet attributed this to about 3 grams (she weighs 14lbs) of not-so-dark chocolate she had consumed 2 days prior, and prescribed a bland diet and pain meds for gastroenteritis. She's eating again, but 4.5 days after consuming the tiny amount of chocolate she's still plainly unwell, and the chocolate doesn't explain the cyclical nature of these episodes (she does not have a habit of eating things she's not supposed to). It seems worth mentioning that she's quite heavy for her size, packing nearly 15lbs on to a frame more fit for 10-12lbs. This is despite eating slightly less than 0.5 cups of food daily (Hill's Science Diet, plus about half a Greenie per day and a few very small treats), and getting a decent amount of exercise. Her biological sister is somewhere around 6 or 7 lbs lighter (albeit slightly smaller in general). My fiancé took her and her sister in as orphaned bottle babies when they were approximately 2 weeks old. Pep was roughly half the weight of her sister at that time (the same one whom she now outweighs). We have always wondered if she might have something affecting both her weight and these periods of discomfort. We know the vet is doing the best they can, but we are tired of taking her there and being given cursory and unfruitful examinations. In this forum we're hoping for some specific possible diagnoses for which we could ask that she be checked. Peppy is the sweetest little girl, and we worry about her. Any insights you could provide would be greatly appreciated. (To avoid confusion: dog being smothered by Pep in top left is not her biological sister :)  

Hello!  After a dog, particularly a small dog, eats chocolate, some things need to be established as a matter of urgency.  This includes the quantity of chocolate, the quality of the chocolate (was it mostly milk and sugar, or mostly chocolate) and the weight of the dog.  Theobromine toxicity is real, affects the kidneys and is frequently fatal; your vet's emergency team will, at any time - even if it's the middle of the night where you are - carry out the sums to establish the urgency of this situation if it has not been worked out already.

In your question, it sounds as though your vet has already made this assessment - I have not - and decided that the kidneys were not at risk.  However, if this assessment has not been carried out, then it needs to be.   Diana Falcao wrote an article for our blog called 'My dog has eaten chocolate, what should I do?' This will give you a little more information.

However, chocolate aside, prior to this your girl was having some symptoms which have recurred again now - and it is possible that these signs may reflect abdominal pain, such as can be seen in pancreatitis.  This is common in dogs that present as overweight and not uncommon in dogs of normal weight.  It is often triggered by eating fatty or sugary foods, such as chocolate, even at safe doses.  Vets used to test for pancreatitis using an enzyme called lipase, but many cases were missed this way and more advanced tests are now available.  However, depending on the lab machine used by your vet, these sometimes have to be requested specifically by the lab.

Arthritic / spinal / other skeletal pain may be surprisingly difficult to spot and sometimes vets will trial pain medications with a view to monitoring the response, if it is not obvious from the examination.  Finally, if abdominal pain is unexplained, then sometimes  ultrasound examination can also be useful.

I hope that this has given you some possibilities to consider and would strongly recommend a return to your vets, asking what causes of the signs remain to be ruled out (as you said, you could ask about pancreatitis specifically) and what tests would be needed in order to rule them out.   Wishing you all the best and please do let us know how Pepperoni gets on!