Older dog losing weight.

I have Sheppard/Lab mixed breed about 13 years old. She is a large dog and has been an indoor dog for the last 7 years. Before she started loosing weight, she was 75 to 80 pounds at her heaviest. She still gets fed the same cup and a half of Dog Chow twice a day she always has and has no problems eating. She is down to about 60 to 65 pounds now and is looking very thin, with her ribs showing prominently. The dog has had several impacted anal glands that made it difficult to have a BM in the past, but seems to have little problems with that now.

My wife, with 6 years vet assistant experience back in the 80s, thinks she is starving due to tumors in her digestive track. The dog will eat very quickly and will sometimes have foamy saliva at the corners of her mouth after eating. My wife says she eats like she is starving, but I am not sure what that would look like. The dog also won't touch the puppy's food, who free feeds. It seems if she were starving, she would eat anything she could.

Other than the loss of weight, she still gets around pretty good for her age, but is noticeably weaker with less stamina (shorter walks). She has issues from time to time with her rear legs and will limp for a bit if one of the younger dogs knock her down playing. Her confidence on stairs is getting worse as well, but she can still make it upstairs every night for bed. There are times when the limping will be prolonged (days or weeks) but canine aspirin seems to help.

I know an examine would help in letting us know if she has tumors or cancer, but money is an issue and I wanted to I want to make sure this isn't a normal pattern for older dogs. If she is suffering, we would want to know so we can make an informed decision.

Sorry for the long question. I appreciate any insight. Thanks,
David Griswold
Omaha, NE

Thank you for your time. She doesn't seem to have issues with frequent urination and spends up to 4 to 5 hours in the house without accidents. She does not receive aspirin everyday. We only give it to her when she shows signs of being in pain walking, such as a limp.

However, she has had a cough in the past. I don't remember the last time it has happened, but it has came and went several times. This has also been discussed as a possible diagnosis with my wife. The last time we took her for a walk, she was coughing towards the end of the walk.

She is a fighter, but I don't want her to suffer, so we will continue to monitor her and try to make sure she isn't in pain.

Thanks again,
David