The 24-year-old Acevedo heard scratching, pulled away the plywood covering the doorway and found the year-old pup, Lola.
She said Lola jumped into her arms and set off a flood of tears. She says the dog was a little skinnier than she remembered.
Veterinarians at Boston's Angell Animal Medical Center said the dog somehow found food and water in the home. They say it is expected to fully recover.
Lola was diagnosed with "refeeding syndrome," a condition that requires a careful reintroduction of food to prevent life-threatening complications in malnourished patients. Veterinarians gave Lola her first meal Wednesday and the dog is now being feed 16 grams -- slightly more than the weight of three nickels -- of wet food every six hours, officials said.