New urine-based kidney stone test delivers results in 30 minutes

The technology, modeled after a carnivorous plant, doesn't require 24-hour collection of samples or processing in a lab.

May 22 (UPI) -- A new urine-based testing system can diagnose people with kidney stones in 30 minutes or less, a study published Friday in the journal Science Advances has found.

Faster test results mean those with the painful condition can start treatment -- and hopefully recover -- sooner. Current testing approaches take up to 10 days to produce results.


"Since the result will be available immediately, such as during an office visit, it will tell the doctor the cause of the stone and guide dietary and pharmacologic interventions," Pak Kin Wong, principal investigator on the study, told UPI.

"The doctor can also use the device to monitor the response of the patient to treatment and indicate the need for other treatment options," said Wong, who is professor of biomedical and mechanical engineering at Penn State University.

Kidney stones are caused by a buildup of certain salts and minerals that form crystals, according to the American Kidney Fund. These crystals, in turn, clump together and enlarge to form a hard mass, or stones, in the kidneys. They might move into the urinary tract and cause bloody urine, pain and blockages.


Typically, doctors use metabolic testing of urine to assess for the presence of the minerals that cause stones to form. These tests require the patient to collect their urine over a 24-hour period in a large container.

Expensive equipment is required to detect urinary minerals for a test result -- meaning the sample has to be shipped to a commercial diagnostic lab for testing, Wong said. The results normally come back in seven to 10 days.

Wong and his team developed a biomimetic detection system called slippery liquid-infused porous surface, or SLIPS-LAB, which works by enabling a reagent and urine droplets to easily move through the testing device's fluid addition channel. This enables the reactants to combine with the urine at the necessary timed rate for reaction.

The test results can then be read using a scanner or a cell phone, and the scanned image can then be analyzed using a computer algorithm. All these steps, according to Wong, take about 30 minutes in a physician's office.

An added benefit, Wong said, is that SLIPS-LAB is more cost-effective than regular, 24-hour testing.

The technology was inspired by nepenthes pitchers, which are carnivorous plants that have unique leaves shaped like pitchers and are filled with digestive liquid, according to Wong. As they've evolved, the plants have developed extremely slippery liquid-infused micro-textured rims that cause insects to fall into the "pitcher," he said.


In their study, Wong and his colleagues demonstrated that SLIPS-LAB enables the reagent and sample to move by themselves and quickly perform the reactions needed to produce results.

The system doesn't require a technician to run any machinery, so it is possible to do the test in non-traditional settings, like a physician's office or even the patient's home, Wong said.

Another promising result of the research was demonstrating that the test also works as a spot test, meaning people with kidney stones can monitor certain levels in their urine without 24-hour collection, said the lead author of the study, Hui Li, a biomedical engineering graduate student.

The team is working with kidney specialists to evaluate the test in larger studies of people with suspected kidney stones.

"In the future, we also hope this device can be used for preventive care of high-risk stone formers, such as patients with personal and family histories of urinary stones, obesity and high blood pressure, like blood glucose testing that a patient can use it at home, to help patients to monitor their stone risk," Wong said.

"The preventive aspect is very important for stone disease, which has a very high recurrent rate."

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