Lethargic, Older Mini Dachshund

Question
I am the 4th owner of a mini dachshund and lately she has been vomitting a clear, foamy substance.  She is also intermittently lethargic one day and her usually bouncy self the next day.  She is anywhere form 7-12 yrs old, according to the last vet I took her to see.  She vomits approximately 4 days a week.  I feed her regular dog food, no table scraps, but this dog will find and eat anything on our walks, from chicken bones to dried worms.  I watch her constantly so she doesn't get to them, but sometimes I'm not always successful.  Basically, I'm asking why she vomits so often.

Answer
The vomiting may be due to a sensitive stomach, food allergy or an internal organ problem such as kidney or liver disease.  I would recommend having some blood tests run to rule out liver and kidney disease.  

In the meantime, FAST her for 24 hours...provide fresh water only.  Then re-introduce a bland diet of boiled chicken OR burger with rice--NO regular dog food, treats or scraps.  If she does not vomit while on this BLAND diet, then I would recommend trying a Hill's Sensitive Stomach food or Prescription Hills I/D.

In addition, I would give her yogurt on a daily basis as well as adding digestive enzymes into her food such as PROZYME.