Okay I can only share my experiance with seizures.....Diggy had them...and he did infact poop AND pee himslef every time he had one. Never passed out....never even closed his eyes. He stiffened up, shook, and drooled. I did Bile acid test for liver and it was good, they did find low blood sugar. Cure was mini meals ever 3-4 hours. Now Digg was only 8-12 weeks old when this was happening which hpoglycemia is common at that young age. Your sisters dog is older and its not so common to come on at that age. DOesntmean it cannot happen tho. I would do like many said and run Bile acid test, its not too expensive and cannot hurt. If the result are good on that then I would explore the hypoglycemia & epilespy route. Just my opinion and I am far from and expert. Just have a little experiance with seizures, and I do know they absolutely stink. I pray for your sisters dog and if you ever need anyone to talk to let me know...Im here.