Patients with chronic kidney failure could be freed from fixed dialysis machines, thanks to a wearable artificial kidney that has shown promising results in a pilot study.

British researchers said yesterday the battery-powered device, developed by US firm Xcorporeal Inc, had proved successful when worn for periods of four to eight hours.

The long-term goal is round-the-clock use, doing away altogether with the need for patients to be hooked up to a fixed haemodialysis machine in a hospital or clinic for 12 hours a week.

"The device has the potential to become a practical means of delivering extended and more frequent dialysis to patients with end-stage kidney failure," Andrew Davenport of University College London and colleagues wrote in the Lancet medical journal.

Further tests are now needed, since their small study involved only eight patients, with an average age of 52 years, who were established on regular haemodialysis before being fitted with the wearable - though rather bulky - device.

The rate of blood flow and the speed at which toxic chemicals were removed from the body was considerably slower than in conventional dialysis but this was not seen as a problem, since the device can be worn for long, continuous periods.

Two of the patients experienced blood clotting, due to receiving insufficient anticoagulant medication, and one was temporarily disconnected when a needle became dislodged. Nonetheless, all the subjects said they would recommend the treatment to other patients with kidney failure, the researchers reported.

Nearly 1.3 million people worldwide suffer from chronic kidney failure that requires treatment with dialysis. A lucky few receive a kidney transplant but donor organs are scarce.

In the long term, experts hope miniaturisation and nanotechnology will provide more convenient and, ultimately, implantable devices that replicate the function of a healthy kidney.

"The wearable artificial kidney reported today is a small first step in the long road to wearable blood-cleansing devices," said Garabed Eknoyan of Baylor College of Medicine in Houston, Texas.