Why did my dog die?

Hi, My dog died recently. She was 11 yr.s 9 mo.s old, about 55-60 lbs., labrador/german shepherd mix.

She had diarrhea over the course of 2 nights (maybe about 8 episodes defecating in total). It stopped for about 12 hours during the day after the first night. Light brown color, no sign of blood. No vomitting. No other apparent symptoms. Still had appetite and willing to go out for walk.

After the second night I gave her a 2mg dose of imodium, and another dose about 1mg 8 hours later. I started feeding her rice with chicken and some water mixed in. She was drinking some wate. The diarrhea stopped and she made it through the night okay. She seemed a little lethagic, possibly from the imodium. Likely a bit constipate due to the imodium.

I had to leave her for a few hours (this was 24 hours after the first dose of imodium and more than 24 hours since her last diarrhea). She seemed okay at the time. When I came back she was dead.

She died laying on the sofa where she normally sleeps. Some white foam had come out of her mouth. Her tongue appeared a bit darker in color, but I am not sure how long she was dead. Not blue, maybe purplish.

She was thin and had been relatively healthy her whole life. No known serious problems from previous visits to the vet. She did sometimes make a choking sound when she would like on her back for stomach pets. It did not really occur otherwise.

I realize now I should have taken her to the vet and maybe the imodium was a mistake (although I have read that it should be okay). Any thoughts on what might have killed her? Dehydration (she was drinking some and had access to fresh water)? Complications from imodium? Heart gave out? Other organ failure? Seizure?

I know you won't be able to tell for sure, but any thoughts based on your experience might help give some closure.

Thanks. That is helpful.

My concern with imodium was that maybe she was not able to get something out of her system that she needed to? However, after 2 days it seems like her system should have been clear of anything she ate. I don't think she ate anything toxic and she did not vomit.

In thinking about, diarrhea and lose stools were becoming a bit more common as she got older. Is that potentially an indication of a serious/terminal problem?

Did the white foam from her mouth indicate anything, or is that common?

Thanks again. You have been helpful.

Thanks again. One last question based on your reply.

She often made choking/gagging/coughing type sound when she would roll over on her back. I never really noticed this when she was upright, or it was very infrequent.

Have you ever seen anything like that and would that possibly indicate fluid in the lungs or a heart condition? Or just the affect of gravity tongue, throat or whatever?