Are bedwetting and daytime wetting different conditions? (Nope)

Parents are often led down different treatment paths depending on whether a child's accidents happen during the day or at night. They shouldn't be.

By Steve Hodges, M.D.

Are bedwetting and daytime wetting different conditions requiring different treatments?

It's a question that keeps surfacing among parents and researchers alike.

A mom in our private support group recently posted:

Is it realistic to think nighttime wetting is a separate problem from daytime, since my son has been dry and soil-free during the day for a long time but is still soaked at night?

Meanwhile, an Algerian study recently concluded that nighttime and daytime wetting "represent two distinct clinical phenotypes...with different underlying mechanisms."

What's more, the mental health literature tends to treat daytime and nighttime wetting as separate conditions, insisting the distinction has a "major impact on the sequence and types of treatment."

In a word: no.

Daytime and nighttime enuresis are simply two symptoms of the same condition: an overactive bladder caused by chronic constipation.

Once in a blue moon, wetting has other causes, such as tethered cord syndrome or diabetes. (I discuss the rare causes in the M.O.P. Anthology.) But virtually all wetting accidents—whether they occur at 2 a.m. or 2 p.m.—happen because an enlarged, stool-clogged rectum aggravates the nearby bladder nerves.

It's important for parents to know this, so you don't waste time pursuing different treatments for what is actually the same underlying problem.

The remedy for daytime enuresis—emptying the rectum so it shrinks back to size and stops aggravating the bladder—also resolves nighttime wetting. Bedwetting just tends to take longer.

In this post, I'll explain how we know daytime and nighttime enuresis have the same cause—and why studies suggesting otherwise reach the wrong conclusion.

READ: Children with Encopresis and Enuresis Deserve the Best Treatment, But Most Aren't Getting It

Daytime and nighttime accidents involve the same organ (the bladder) doing the same thing (contracting involuntarily). So why are they so often treated as different conditions?

The answer comes down to one arbitrary difference: whether the child is awake when the accidents happen.

That single distinction has sent researchers, clinicians, and parents down very different paths.

An accident that happens overnight is often blamed on "deep sleep," urine overproduction, or a bladder too small to hold urine all night. The recommended remedies include waking the child, prescribing drugs to reduce nighttime urine production, or simply waiting for the child’s bladder to “mature.”

An accident that happens at school, meanwhile, is often blamed on behavior, psychological distress, an unwillingness to stop playing and use the toilet, or an inability to "listen to their body." These children are often referred for behavioral or psychological therapy or, if they have ADHD, sensory processing disorder, or autism, the accidents are simply attributed to those diagnoses.

In both cases, the assumption is the same: the timing of the accidents reveals their cause. But there's no logical reason it should—and no compelling evidence that it does.

The bladder doesn't know—or care—whether the child is asleep or awake.

Let’s start with the pioneering research of Dr. Sean O'Regan, the pediatric kidney specialist who demonstrated in the 1980s that enuresis was caused by constipation.

To Dr. O'Regan, daytime and nighttime wetting were simply different manifestations of the same problem: an enlarged, stool-filled rectum irritating the bladder. His studies included children with daytime wetting, nighttime wetting, or both. He saw no reason to distinguish among them, referring simply to "enuretic children."

Dr. O'Regan also recognized that encopresis and recurrent urinary tract infections were additional manifestations of the same underlying problem. At the time, bowel and bladder dysfunction were widely considered unrelated.

Using anorectal manometry, Dr. O’Regan confirmed that children with enuresis, recurrent UTIs, and encopresis had profoundly impaired rectal sensation and rectums stretched to more than twice their normal diameter. Urodynamic testing also showed uninhibited bladder contractions in the children with enuresis.

Dr. O’Regan’s published results strongly supported his theory. In one study of 47 girls with recurrent UTIs, 44 stopped having infections after completing his three-month enema protocol. Twenty of the 21 girls with encopresis stopped soiling, and 22 of the 32 girls with enuresis became dry.

The following year, Dr. O'Regan reported similar results in 17 children with nighttime wetting, daytime wetting, or both. Anorectal manometry showed all were severely constipated. After treatment, every child either showed improvement or stopped wetting.

But if Dr. O'Regan's theory was correct, why didn't every child completely stop wetting?

His studies don't fully answer that question because his treatment protocol lasted only three months. My own clinical experience offers the missing piece.

Daytime wetting usually resolves much sooner than nighttime wetting. Dr. O'Regan's three-month enema regimen simply wasn't long enough (or robust enough) for many children to become completely dry at night.

Different rates of recovery do not imply different causes.

Many children experience what I call the Long Lag, a scenario where bedwetting persists long after poop accidents and daytime wetting have resolved. I explain this phenomenon in The Long Lag: Why Bedwetting Takes Longer to Fix Than Daytime Accidents.

When a child is mired in the Long Lag, it’s understandable parents might suspect bedwetting has a different cause.

It doesn’t.

Recovery depends not only on how enlarged the child's rectum is but also on how sensitive the bladder nerves are. Some children stop wetting after a modest reduction in rectal size. Others don't become dry until the rectum has completely shrunk back to normal and the irritated bladder nerves have had many months to recover.

When bedwetting persists after daytime wetting has resolved, it's tempting to hunt for a different cause. But that's a wild goose chase.

With my patients, I adjust the treatment regimen and, depending on what an abdominal x-ray shows, add bladder medication while the empty-but-enlarged rectum continues to shrink. The Anthology includes several strategies for shortening the Long Lag.

If daytime and nighttime wetting really have the same cause, why do some studies conclude otherwise?

The Algerian study is a good example because it contains three fatal flaws common to studies claiming daytime and nighttime wetting have different causes.

Fatal flaw #1: Researchers rely on unreliable methods to determine which children are constipated.

The Algerian researchers listed constipation as a possible contributor to enuresis but concluded it was not a major factor because they detected constipation in only 27% of children with daytime wetting and 20% of children who wet only at night.

Yet Dr. O'Regan's research, and my own, found that virtually all children with enuresis have a severely enlarged, stool-filled rectum.

Why the discrepancy?

Because the Algerian team, like many researchers, used the Rome criteria to diagnose constipation. This symptom checklist misses many cases because it relies on parent reports of the child's bowel habits and symptoms rather than actual measurements. I detail the problems with these criteria in Even Severe Constipation Goes Undiagnosed in Bedwetting Children. Here's Why.

Unless you're evaluating the rectum with anorectal manometry or abdominal x-ray (including rectal diameter), you simply don't know which children have stool retained in the rectum. Without that information, you can't reliably assess the relationship between constipation and enuresis.

Fatal flaw #2: Researchers rely on indirect evidence to determine whether children are producing too much urine.

The Algerian team concluded that bedwetting is "mainly related to nocturnal urine overproduction." But they never actually demonstrated that the kidneys were producing too much urine.

Instead, they estimated overnight urine production by adding together the child's first-morning void and the urine absorbed by overnight diapers and sheets. They then compared that to a predicted bladder capacity based solely on the child's age—not the child's actual, measured bladder capacity.

This approach can easily overestimate urine production. A child who wets the bed early in the night may empty the bladder, continue producing urine, and then urinate again in the morning. The resulting urine volume reflects two bladder voids, not necessarily excessive urine production.

Furthermore, the researchers never measured vasopressin levels, even though inadequate nighttime secretion of this hormone is the proposed explanation for urine overproduction. That's understandable because measuring vasopressin isn't straightforward. A single blood sample tells you very little. To determine whether a child lacks the normal nighttime rise in vasopressin, you'd ideally need multiple blood samples collected throughout the night while the child sleeps—a cumbersome, invasive, and impractical procedure.

True pathological urine overproduction does exist. Children with diabetes insipidus, a rare hormonal disorder, produce enormous volumes of urine around the clock and are constantly thirsty. I've seen two such cases in my career. Diabetes mellitus can also cause excessive urine production, and I've encountered a few of those patients as well.

Those are genuine examples of polyuria. Wetting the bed does not, by itself, demonstrate that a child is producing too much urine.

The methods used by the Algerian team don’t come close to showing that children with nighttime enuresis overproduce urine.

Fatal flaw #3: Researchers mistake differences in severity for differences in cause.

Researchers often assume that because some children wet only at night while others wet during both the day and night, the two groups must have different underlying causes. (Still others wet only during the day, a less common presentation I explain in the M.O.P. Anthology.)

But a simpler explanation fits the evidence.

The severity of a child's urinary dysfunction depends on two factors: how enlarged the rectum is and how sensitive the bladder nerves are to that stretching. As rectal enlargement worsens, the bladder becomes increasingly irritated and prone to involuntary contractions.

About one-third of children with nighttime enuresis also experience daytime wetting. In my practice, abdominal x-rays typically show that these children have more stool retained in the rectum than children who wet only at night. Their rectums are more enlarged, their bladders are more irritated, and the bladder contractions are more forceful.

It takes a mighty aggravated bladder to trigger accidents while a child is awake. Bedwetting is more common because it takes less severe bladder overactivity to cause accidents during sleep.

Researchers often argue that children who wet only at night produce too much urine. To explain why these children don't wake up to urinate, they invoke another theory: that they sleep too deeply. But neither explanation is supported by convincing evidence.

In fact, studies show that children with enuresis tend to sleep less deeply than their peers, as I explain in Nope, Deep Sleep" Doesn't Cause Bedwetting (It's Impossible)

But this line of thinking ignores another important question: If these children really are producing excessive amounts of urine, why don't they simply wake up and use the toilet?

Because they don't have time. The bladder contractions come on so suddenly and forcefully that the child can't stop them—much like trying to stop a sneeze or a hiccup once it's started.

The Algerian study concludes that everything about daytime and nighttime enuresis is different except one thing: both types of accidents cause considerable psychological distress—low self-esteem, social withdrawal, anxiety, and increased parental stress.

On that point, we completely agree.

But treating daytime and nighttime wetting as different conditions only compounds that distress. It sends families down the wrong treatment path and delays recovery.

Recognizing that daytime and nighttime wetting are different manifestations of the same underlying problem puts families back on the treatment path that stops the accidents—and helps children regain their confidence, independence, and childhood.