Medical researchers from the University of New South Wales have identified a link between the acidity levels in urine and overactive bladders.

The team has found that acid inside urine is an important stimulant of the cells lining the bladder wall.

These cells then release a chemical which activate nerve receptors, sending a signal to the brain that the bladder is full.

The researchers say it is the first time that a connection has been drawn between acid and bladder function.

“No-one really knows what causes overactive bladder – that’s what makes it such a difficult thing to treat,” said the paper’s lead author Professor Elizabeth Burcher, from UNSW’s School of Medical Sciences.

“Acid is a new stimulus that we haven’t been aware of before.”

At the moment drugs aimed at reducing the activity of neurotransmitter receptors in the bladder wall are the main treatment for overactive bladder.

However Professor Burcher said these drugs have a number of side effects including dry mouth, constipation and drowsiness.

They can also be expensive. Overactive bladder currently costs more than pneumonia and influenza, osteoprosis and breast cancer.

“A new more cost-effective approach would be terrific. There’s no doubt it’s an area of unmet need,” said Professor Burcher.

The next step is to conduct further investigations to see if the results apply to humans.

“It’s always difficult to relate animal findings to human tissue, and there are species differences,” she said.

“But we’ve shown that acid is a stimulus in two animals – the pig and the rat. There’s no reason to believe it wouldn’t be the case in humans too.”

The study was published in the British Journal of Pharmacology. It was conducted with support from the federal government’s National Health and Medical Research Council and a grant from Pfizer.