Thomas George's parents feared their son might lose his right arm and the sight in one eye after finding him covered in blood in the street after the attack in Mangotsfield.
The Barley Close Primary School pupil was bitten on his right arm, neck, shoulder, back and face by a dog believed to be an Alsatian - Rottweiler crossbreed.
The muscles in part of his bicep and underarm had been ripped from the bone and he underwent a five-hour operation to reattach them and clean up his wounds after the incident on Monday.
The dog which attacked him has been put down by its owner.
Thomas was playing with a friend near his home in Springfield Road at around noon on Monday.
The friend, a boy who was staying with relatives living nearby, asked Thomas if he wanted to play at his grandmother's house. As Thomas entered the house the dog, which was being held by the other boy, jumped towards him and began biting and shaking him.
His mother Carrie Lambert, 29, and father Steven George, 33, were in their back garden when they heard screams coming from down the road. Ms Lambert said:
"We saw a car stopped in the middle of the road and first we thought someone had been run over. But then I saw Thomas running down the road towards me covered in blood.
"His arm was spurting blood and it was running down his face. I was really worried he was going to lose his arm, as I could see the muscle hanging off and there was just an unbelievable amount of blood.
"We also thought he might lose his eye – in the end the cut near his eye was superficial but it was bleeding a lot as well."
Mr George called an ambulance, which took Thomas to Frenchay Hospital. After the lengthy operation doctors told Thomas's parents that he will need physiotherapy but should be able to use his arm normally again eventually.
He returned home yesterday with his arm heavily bandaged and in a sling.
His mother told the Post he will need counselling after being left traumatised by the incident.
"It was so awful to see him in that state," said Ms Lambert. "He is a normal, happy-go-lucky seven-year- old boy and likes to be active and run around with his friends.
"He has told me he doesn't want to talk about what happened and says he won't play outside anymore – it's heartbreaking.
"Thomas will not be able to go back to school on time next week and won't be able to use his arm for a little while. He's left-handed and this was his right arm, so that's a slight positive."
Ms Lambert and Mr George say they did not know the dog's owner, a relative of a boy their son had met during the school holidays, and had not been to see them since the attack, although the owner had apologised.
"We did not know the owner of the house had a dog, and wouldn't have let Thomas play there before checking it out ourselves had we known," she said.
Ms Lambert said the couple, who have another son Kieran, nine, wanted to thank refuse collectors who helped get the dog off Thomas by throwing sticks at it.
An Avon and Somerset Police spokeswoman said that no offence under the Dangerous Dogs Act had been committed.
Police have told Thomas' parents that any legal action in relation to the incident would have to be brought in a civil court.
(This is Bristol - Sept 1, 2011)
