Hello Andrea, I'm Dr. Deb. Thanks for requesting me; I'll do my best to help you today.
I'm sorry for this concern for Annie.
It's certainly possible that her anal glands are bothering her since this is a commonly seen problem in small dogs but such a problem is unlikely to be the underlying cause of her loose stools.
Some dogs with diarrhea will rub their butts secondary to discomfort/irritation in their colon so if I had to speculate, I'd say this was the cause.
As to possible explanations for her diarrhea, there could be several explanations ranging from internal parasites to dietary indiscretion to viral or bacterial diseases to Inflammatory Bowel Disease to systemic issues (problems with the kidneys or liver, for example).
In most cases, symptomatic treatment is enough to resolve the problem and I'll include my suggestions below:
1. I'll occasionally suggest one or two doses of Imodium (Loperamide) but not very often for several reasons:
a) I've seen a number of dogs develop side effects such as constipation, bloat, and sedation with other, potentially, more serious adverse effects also possible: paralytic ileus, toxic megacolon, pancreatitis, and central nervous system signs.
b) In addition, collies, shepherds, related breeds, or other dogs who have a defective MDR-1 gene mutation may be overly sensitive to loperamide and it's use should be avoided. I think it unlikely that Annie has this gene since she's not a breed at risk but you can never be too careful.
I also think your dose is higher than I would have suggested for a dog this size.
2. Instead, I'll usually recommend regular strength PeptoBismol as long as my patient isn't vomiting or taking steroids or non-steroidal anti-inflammatory medication. The dose would be 1 ml per 10 lbs of body weight 2-3 times a day which means Annie would be given about 1/2 teaspoon at one time.
Pepto bismol should not be given to vomiting dogs since it contains salicylates (the active ingredient in Aspirin) which can irritate the stomach.
3. I'd also start her on a good quality, canine probiotic such as Forti Flora or Resources Protegrity GI. These products can be extremely useful for gastrointestinal issues (and to help strengthen the immune system as well). They may be available at local pet/grain stores or can be purchased online.
4. I often do recommend a bland diet of 1 part boiled, skinless chicken breast (or hamburg) to 20-minute white rice if the patient wants to eat.
5. Offering Pedialyte in addition or instead of water can also help replace electrolytes lost in the looser stools. It doesn't have a great taste, though, so many dogs won't drink it. You can use a syringe or small turkey baster to dribble fluids into her mouth if she's not drinking much to help keep her hydrated.
If she continues to have no interest in food and/or the diarrhea persists for more than a day or so and/or if she starts to vomit or become lethargic, then a vet visit may be prudent.
I hope this helps and that she's feeling better soon. Deb