US Supreme Court Justice Ruth Bader Ginsburg will return to work after a gallbladder treatment, allaying fears of a vacancy that would have allowed President Donald Trump to appoint another conservative to the bench.

Justice Ginsburg, who has had a series of health scares, underwent non-surgical treatment for a gallbladder condition on Tuesday (local time) and was resting comfortably, court spokeswoman Kathy Arberg said.

The health of the liberal justice is closely watched because a Supreme Court vacancy would give Mr Trump the opportunity to appoint a third justice to the nine-member court and push it further to the right.

The court currently has a 5-4 conservative majority.

Justice Ginsburg, also known to her fans as RBG, faced workplace discrimination as a pregnant woman in 1950s America. She helped draft the landmark Pregnancy Discrimination Act of 1978.

The 87-year-old had a gallstone that had caused an infection and was treated at Johns Hopkins Hospital in Baltimore, spokeswoman Kathy Arberg said in a statement.

Justice Ginsburg is expected to participate in the court's oral arguments on Wednesday (local time) remotely from the hospital.

Tests following the court's oral arguments on Monday morning (local time) showed Justice Ginsburg was suffering from a gallstone that had migrated to her cystic duct, a tube that empties the gall bladder, blocking it and causing an infection, Ms Arberg said.

Justice Ginsburg is expected to stay in the hospital for a day or two, the spokeswoman said.

News of her ill health and recovery often trends on Twitter, with supporters sending prayers and expressing relief at her return to work.

The court's oldest justice has had a host of health issues in recent years.

In November 2018, she broke three ribs in a fall. Subsequent medical tests led to treatment for lung cancer that caused her to miss oral arguments in January 2019.

She returned to the bench, but said in August she had received radiation therapy to treat pancreatic cancer.

The Supreme Court this week has been hearing oral arguments by teleconference for the first time in its history in response to health concerns raised by the coronavirus pandemic.

ABC/Reuters