pheripheral edema in lab puppies

Question
I am in the process of purchasing a pure bred black lab puppy, it is the grand daughter of my female dog.

Recently several of the pups have developed massive swelling in their lower limbs.  The pups behavior is fine and they do not have pain.

they have been to the vet twice and this particular vet is unable to diagnose.  He is on his way to the university today with two of the pups.  

The litter size is nine pups but only 4 or 5 are effected.

The vet did a liver function test and that checked out ok.

there is no fever, no diareha, no vomitting, no wieght loss.........they are active, defecate, urinate, and eat normally.

The rear legs are more effected than the front legs, some pups  only have one or two legs effected.

You can actually see the fluid sacks, it is almost like elephantititis

The puppy's dad has an allergy to food protien. he is the offspring to my female dog.

any guesses as we are anxious for some sort of answer and the university will most likely take at least a weeek or more.

Unfortunately if the pup requires ongoing medical care we will be unable to afford it so we will not be able to purchase the pup, however if this is a short term thing then we will go a head.

thank you for your time

Answer
I would be concerned about underlying heart disease or abnormal protein metabolism.  If the legs are accumulating fluid, it may be only a short time before fluid accumulates into the belly and chest.  I would not recommend purchasing one of these puppies or any puppies from this bitch or stud.  This is not likely to be a short-term medical problem.