A four-year-old Hong Kong girl who will undergo life-saving surgery in Australia today believed she was on a sightseeing trip, her mother said. Tang Tsz-ching, who was born with a rare heart disease, checked into a hospital in Sydney yesterday afternoon in preparation for the operation to prolong her life. Her parents said yesterday they had withheld details of the surgery from Tsz-ching, telling her she was to have a checkup so as not to scare her. 'She cried before coming here today. She dreads going to hospital as it reminds her of the pain she has experienced from injections and blood tests,' said mother Tang Cheng Yin-kwan. 'We dare not to tell her about the operation. All along she's thought she is here for sightseeing.' Tsz-ching's condition deteriorated a year ago, forcing her to stop attending school in October. A director at her school then offered to foot the bill of up to $500,000 for the operation, which the family could not afford. Yesterday, in the Children's Hospital in the suburb of Westmead, a cheerful Tsz-ching was immersed in a cartoon on television, saying she wanted a vanilla ice-cream. When asked what impressed her most about Australia, Tsz-ching said 'giraffe', referring to the animal she saw during a visit to Sydney zoo shortly after arriving late last month. 'We took her to see the Opera House and the zoo. She had a good time,' Mrs Tang said. While Tsz-ching remains cheerful, her parents are finding the stress increasingly hard to bear. 'We are getting less and less sleep as the day of the operation nears, said father Tang Kwai-wa. 'I woke up this morning and thought: 'Oh dear, it's tomorrow.' Sometimes I just have to seize the moment and look at her face a little more. Who knows what will happen tomorrow?' The couple said they expected to spend the next two weeks at the hospital before Tsz-ching was discharged. 'Sleeping on a couch [by Tsz-ching's bedside] is not a problem. My biggest concern is her well being,' said Mrs Tang, who is six months pregnant. Dr Lau Kai-chu, a paediatric cardiologist at the hospital who is assisting in the diagnosis, said the five-hour operation was low-risk, but life-saving. 'Without it, the girl is not going to die within weeks, but her life span would be severely restricted,' he said. The open-heart surgery involves closing a hole in Tsz-ching's heart and removing an obstruction to the flow of blood.