International vets "nearly lost" a 17-year-old elephant in Pakistan on Wednesday after knocking her out to perform diagnostic tests, but they now hope to treat multiple issues that have left her crippled for months.

Noor Jehan has been barely able to walk around her enclosure at Karachi Zoo because of a huge growth between her back legs, sparking concern from keepers and visitors.

A team of veterinarians and wildlife experts from Four Paws International intervened after images of the ailing African elephant were shared across social media.

"We nearly lost Noor Jehan when we gave the sedative," veterinarian Amir Khalil told reporters after the jumbo diagnosis.

"It was a risky procedure."

A huge crane was deployed on Wednesday to lift the 3.5-ton pachyderm after she had been tranquillized.

Ultrasound and other tests suggest Noor Jehan has a huge hematoma inside her abdomen, as well as issues with her intestines.

"It is clear Noor Jehan is in serious pain and suffering," Khalil said.

"There is a treatment for this... it needs some luck and it needs a lot of work in coming days."

Pakistan's zoos are frequently criticised for disregarding animal welfare, and in 2020 a court ordered the only zoo in the country's capital to shut because of its decrepit state.

The zoo drew international condemnation for its treatment of an Asian elephant named Kaavan, who was later airlifted to retirement in Cambodia in a project spearheaded by US popstar and actor Cher, and carried out by Four Paws.

Last year a zoo in the eastern city of Lahore called off plans to auction 12 lions to private individuals after overbreeding, saying it would instead create new enclosures for the big cats.

"It is high time to phase out zoos from Pakistan," said Mahera Omar, the chief of Pakistan Animal Welfare Society.