Is it true that once you go toilet on a night out, you won't be able to stop going?

Is this you on a night out after a few drinks? Photo / 123RF

For Kate, the Friday night fear is real.

At about 5pm she'll leave her job in the Sydney CBD and head out with some colleagues to the pub. There'll be a few beers and then they will carry on for a few celebratory bubbles, if they're lucky, at a bar with a harbour view.

But there will be a niggling worry in the back of Kate's head.

"You hold it in as long as you can but once you go once ... you keep on going."

"When I'm drinking at home it's actually not too bad and I don't have to go as often," said Kate from Bonnyrigg in western Sydney.

"But it happened last night at a work event. The first couple of hours drinking you're OK but then obviously after a few you'll eventually need to go to the loo and after that it's pretty much like clockwork."

By Kate's reckoning, spirits and white wine unlock the floodgates, but red wine less so.

It is almost universally called breaking the seal - the theory that on a night out once you go to the loo you'll then will have to go at regular intervals for the rest of the evening.

But is breaking the seal actually real? Or is it all in our heads?

Well, it turns out there may be some truth to the theory. But it's less about Friday nights and more about the alcohol itself. So much so, if you were only drinking soft drinks you'd be unlikely to feel the burn quite so firm.

Urologist and spokesman for the Urological Society of Australia and New Zealand, Associate Professor Peter Chin, told news.com.au that not only was breaking the seal real, alcohol had distinct qualities that compounded the problem.

Around 20 per cent of alcohol is immediately absorbed into the blood stream, he said. The remaining 80 per cent can take about 30 minutes or more to get absorbed and for you to feel the effects.

As the alcohol travels around the blood stream it eventually ends up at the kidneys where waste becomes wee.

"It is the effects of alcohol on the kidney and bladder that can result in the phenomenon of breaking the seal," Mr Chin said.

"Firstly, alcohol - and caffeine - are both diuretics and make the kidneys start to produce more urine. Secondly, the effects of alcohol and caffeine on the bladder are as 'irritants', they make your bladder more irritable, and so less able to hold onto urine.

"If you continue to drink, the effects compound as you produce more and more urine and your bladder gets more and more irritated resulting in breaking the seal and a feeling that you just opened the floodgates," he said.

However, breaking the seal probably wouldn't be so bad if it wasn't for another effect associated with alcohol.

Booze interferes with the pituitary gland situated in the base of the brain. When it's working normally, the gland produces the antidiuretic hormone which tells the kidney to absorb more water and not send as much to the bladder.

But alcohol flicks a switch on the gland and reduces the amount of this hormone being produced. In turn, this leads to more liquid cascading down to the bladder eager to find the nearest exit.

Of course, the amount of liquid you drink will cause more pressure on the pipework down below. But, Mr Chin said, the irritation alcohol causes the bladder was "the forgotten part of the equation."

"Once alcohol causes the diuresis and irritation, the dam breaks and ongoing consumption of alcohol leads to the phenomenon of breaking the seal."

For people suffering from cystitis or urinary tract infections the effect can be magnified with just a single drink sending you scurrying. As you get older, your tolerance to alcohol can also change.

But what can you do to, if not to prevent the seal from breaking, then at least patch it up so you don't go so often?

"Clench it in and hold out as long as possible," laughs Kate. "Crossing your legs also helps".

Mr Chin said there are ways to beat the seal.

"The good news is you can train your bladder to hold more," he said advocating a "calendar plan" over several weeks.

"On the first week you make sure you wait at least one hour between each visit to the toilet. The following week you wait one hour and fifteen minutes, and each week add an additional 15 minutes until at six to eight weeks your bladder should be able to hold on for around three hours.

"But if drinking only a small amount of alcohol means you are in the toilet every 15 minutes then you should consider getting it investigated because that isn't normal." Mr Chin advises.

Otherwise, breaking the seal is just one of those side effects of a good night out.

"If it's only a minor thing and you accept that you may need to go to the toilet more frequently when you drink alcohol then you should drink as much as you feel like," Mr Chin said.

"Within reason," he added.

So, do yourself a favour. If you don't want the river to keep on running once the dam wall bursts - stick to mocktails.