Why does a trip to the bar mean so many trips to the bathroom?

It usually hits when you’re quaffing your fourth bottle of Beck’s. Your bladder starts dictating how much of your friends’ protracted story you have the patience to listen to. Distraction takes over as your smile becomes strained and, before you know it, you demand that your friend hold that thought, and your drink, while you lunge for the bathroom. Nature taps you on the shoulder and screams in your ear, “You must break the seal!”

This inability to control Nature’s call afflicts even the most experienced drinkers now and again. Many imbibers pin this sudden response to excessive pints of ale simply catching up with the body. But it doesn’t quite add up that way. Explaining this bladder phenomenon goes beyond plumbing mechanics and involves understanding how the bladder interacts with a more northerly organ – the brain.

Usually your bladder can be filled to half capacity before it sends a message to your brain about the need to excrete fluid from the body. The ensuing urge isn’t sudden and is usually suppressible, as the layered, smooth muscle that surrounds the bladder stays relaxed until a timely encounter with a Jiffy-John occurs. Once the coast is clear, the nervous system signals the bladder muscles to contract into a funnel shape. That applies pressure to the bladder walls leading to the expulsion of urine and a sigh of relief.

Things change, though, three margaritas into happy hour. Alcohol, in urinary terms, is a diuretic. It suppresses a part of the brain – the pituitary gland – from producing a hormone that regulates the water content of your body. Interrupting this balance causes the kidneys to sequester excessive amounts of water in the bladder instead of reabsorbing it. As the night wears on, the plot thickens as a discrepancy between actual urine volume and the urge to “go” arises – the need to visit the powder room becomes more about what’s going on in your brain than what’s going on in your bladder.

This curious imbalance was discussed at a recent meeting of the International Continence Society. Recent MRI imaging studies have differentiated brain centers that pertain to bladder fullness from regions involved in the false sense of urgency. One study, authored by B. S. Athwal and reported in the journal Brain, found that “mismatching” – when one experiences a low degree of bladder fullness with a high urge to urinate – is caused by deactivation in parts of the cortex that receive sensory information from the entire body.

Another study, headed by Derek Grifiths of the University of Pittsburgh, found that poor bladder control is associated with weak activation in another part of the cortex, important for decision making and impulse inhibition.

Unfortunately, nobody has yet sent someone into an MRI with a dry martini in hand to directly study the effects of alcohol on the bladder-brain relationship; most likely because there would be too many other factors that would impinge upon the results. But it appears that going number one for the first time while boozing exacerbates miscommunication between your bladder and your nervous system, leading to the infamous “breaking of the seal.”

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