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Medical Rounds

Getting Pumped

For patients with cirrhosis of the liver awaiting transplant, it’s not uncommon to experience a buildup of fluid in the abdomen. When water leaks out of blood vessels and into the peritoneal cavity, it has nowhere to go and no way to move.

“Until the patient gets a liver transplant, the only way to alleviate that fluid buildup and the pressure that it causes has been to drain the fluid manually every one or two weeks,” says gastroenterologist Ashish Nimgaonkar. “That’s an expensive procedure, and the fluid buildup significantly impairs the quality of life for the patient.”

Tapping several liters of fluid also requires an infusion of albumin to help maintain cardiovascular and kidney function. “Albumin is made from human plasma, and it can be quite expensive. For every liter of fluid we pull from a patient, we infuse up to 8 grams of albumin,” says Nimgaonkar. He estimates that each patient visit to have fluid drained costs between $2,000 and $3,000.

Now he and his Johns Hopkins lab team have designed a mechanical pump that can move the fluid out of the cavity and into the bladder or stomach, where patients can eliminate it naturally themselves.

Nimgaonkar knew that a simple drain wouldn’t work; there was nothing to propel the fluid from the cavity through the drain. And an electrical pump was also a nonstarter, since metal interferes with MRI—commonly needed by patients awaiting living transplants.

The solution? A purely mechanical pump made of silicone and other MRI-compatible materials that uses the patient’s natural body movement to pump fluid out of the peritoneal cavity. “It’s a biopowered shunt,” Nimgaonkar explains. “Body movement creates a pressure differential between the cavity with the fluid in it and the bladder or stomach. The pump senses the difference in pressure and drives the fluid from one chamber to the other.”

Nimgaonkar is now testing the pump in animal models and expects to see it move to clinical trials within a few years. “We estimate that this will save the U.S. health system more than $1 billion a year,” he says. “Best of all, these patients don’t have to get so sick.”