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A Japanese Twist on Bedwetting Treatment: Olive Oil Enemas Plus Liquid Glycerin

By Steve Hodges, M.D.

I’m always on the lookout for better, faster ways to help children resolve encopresis (chronic poop accidents) and enuresis (bedwetting or daytime pee accidents).

After discussion with a pediatric surgeon in Kobe, Japan, I believe I’ve hit upon a promising new regimen for the most stubborn cases. I’m talking about cases where even diligent adherence to the Modified O’Regan Protocol (M.O.P.), a daily enema regimen, does not fully empty the child’s rectum, so accidents persist.

I also suspect this protocol will provide faster results for children who begin enuresis and/oor encopresis treatment with fecal impaction, as well as constipated kids who are supremely motivated to get dry — that is, determined enough to comply with what is admittedly a cumbersome treatment.

In deference to the research out of Japan that inspired it, I’m calling the new protocol “J-M.O.P.”

The regimen involves an overnight olive-oil enema before bed, followed by a “Japanese-style” glycerin enema in the morning and a second glycerin enema in the afternoon or early evening. The regimen continues daily until the child has been accident-free, day and night, for two to four weeks. At that point, as with all M.O.P. variations, the child gradually tapers off enemas.

Japanese-style glycerin enemas, as I detail below, contain two to four times the glycerin volume found in standard American liquid glycerin suppositories (LGS) and contain equal parts glycerin and water. For convenience, I’ll call these glycerin-and-water enemas GWE.

To implement J-M.O.P., all you need are olive oil, liquid glycerin, water, and syringes — no store-bought enemas required. This regimen can be implemented inexpensively worldwide.

In this article, I’ll discuss the research that inspired J-M.O.P. and my rationale for the protocol. The dosing specifics and tapering recommendations can be found in the J-M.O.P. Cheat Sheet, a downloadable addendum to the M.O.P. Anthology 5th Edition.

Heads up: This post assumes you’re familiar with enema-based treatment in general and M.O.P. in particular. If you’re new to this treatment approach for enuresis and encopresis, start with these blog posts:

First off: Why do I see a need for yet another version of M.O.P.?

After all, I’ve already published five variations of the protocol, all of them explained in the M.O.P. Anthology: Standard M.O.P. (daily enema + osmotic laxative), M.O.P.x (daily enema + stimulant laxative), M.O.P.+ (daily large-volume enema), Double M.O.P. (overnight oil enema + morning large-volume enema), and Multi-M.O.P. (three docusate sodium mini-enemas per day or two liquid glycerin suppositories per day).

Geez, isn’t that enough to choose from?

For most kids, yes. Nearly all my patients are able to overcome enuresis and/or encopresis with these M.O.P. variations. Though it often takes a few months of trial and error to settle on the best regimen for a given child, eventually almost all kids can achieve and maintain an empty rectum.

That, of course, is the goal of treatment. Only when the rectum is completely and persistently emptied of stool can it shrink back to normal size, regain lost tone and sensation, and stop aggravating the bladder nerves. That’s when accidents stop.

However, there is a subset of children, many of them teens or tweens, who continue to have accidents (usually bedwetting) despite months of M.O.P. treatment. This is monumentally frustrating to families — and to me. Parents ask: How can my kid still be wetting the bed after all those enemas?

Inevitably, an x-ray provides the answer: There’s still poop in the rectum. In these unlucky kids, stool seems to be Super-Glued, if not welded, inside the rectum.

What on earth can be done to dislodge and flush out this crusty, clingy, stool pile-up? From experience, I know that success requires 1.) more frequent pooping, and 2.) an enema solution that stimulates complete evacuation.

By “more frequent pooping,” I mean at least two full-on bowel movements per day. A single daily bowel movement won’t make a dent in a poop pile-up.

For some kids, a single daily enema plus an osmotic laxative (Standard M.O.P.) is sufficient to prompt two bowel movements per day. But many children — those with a deeply ingrained tendency to withhold poop and with severely compromised rectal tone and sensation — need more help. For these kids, in the early stages of treatment, I recommend either a second daily enema (Multi-M.O.P.) or a senna-based stimulant laxative such as Ex-Lax (M.O.P.x).

And yet, in some children, even two stimulated bowel movements per day simply will not clear the rectum. The stool is just stuck.

Which brings me to the second part of the bowel-clearing equation: the enema solution.

I’ve come to believe that for the most challenging cases, the best solution may be to soften stool with olive oil overnight and then stimulate evacuation with elevated doses of liquid glycerin twice a day — not just for a few days but for as long as it takes accidents to stop.

(For those steeped in M.O.P. parlance, J-M.O.P. essentially combines Double M.O.P. with Multi-M.O.P. but with an increased volume of glycerin, in combination with water.)

I’ll get to the olive oil shortly, but let’s start with glycerin. Why do I favor glycerin?

Because it’s gentle, effective, inexpensive, and widely available and because I believe it can safely be used twice a day. (In the Anthology, I explain how to make DIY glycerin enemas.)

By contrast, phosphate (Fleet) enemas cannot be used twice a day (because phosphate is an electrolyte). Docusate sodium mini-enemas (Enemeez) are effective, gentle for most kids, and suitable for use two or even three times per day, but they also are expensive and hard to find outside the United States. Plus, you can’t make these enemas at home, adjust the volume, or use them in conjunction with oil enemas, as I explain in the Anthology.

Until recently, I wasn’t entirely comfortable recommending twice-a-day use of liquid glycerin. Pedia-Lax, manufacturer of pre-made liquid glycerin suppositories, advises against it. A company representative emailed me: “Glycerin can be irritating to the mucosa and [even] one liquid glycerin suppository can cause burning.” However, this has not been my experience. My patients find liquid glycerin quite gentle. Thousands have used glycerin daily without a problem. A rare few have reported discomfort.

I didn’t feel the Pedia-Lax caution was medically justified, so I probed further and found a study by Akiko Yokoi, M.D., Ph.D., a pediatric surgeon and researcher at Kobe Children’s Hospital in Kobe, Japan.

Coincidentally, I had already blogged about Dr. Yokoi’s 2020 study in the Journal of Pediatric Surgery, titled “The usefulness of olive oil enema in children with severe chronic constipation.”

In that blog post, I had focused on her findings supporting olive oil enemas, an excellent remedy that dates back to the 19th century but had never been formally studied.

On second look at Dr. Yokoi’s study, I zoomed in on her references to liquid glycerin enemas. In Japan these are commonly used to treat children with chronic constipation and are sold commercially in much larger volumes than in the United States.

I contacted Dr. Yokoi to learn more about her hospital’s use of glycerin enemas. In an email, she told me she has no safety concerns about using glycerin in higher volumes for extended periods on a daily basis and more than once a day if needed.

In her training, she learned that “glycerin primarily stimulates evacuation and is expelled with the stool after all, which suggests it doesn't have systemic effects, even in higher doses. So, it is generally safe.”

In Japan, glycerin enemas are commercially available in a formulation containing 50% glycerin and 50% water, in volumes of 30 ml (that is, 15 ml glycerin, 15 ml water), 60 ml and 120 ml. By comparison, store-bought glycerin enemas in the United States contain 4 ml for children under 6 and 7.5 ml for children 6 and older.

In other words, the Japanese commonly use two to four times as much glycerin as we do.

“We frequently use glycerin enemas and generally find them very effective,” Dr. Yokoi told me.

Kobe Children’s Hospital often prescribes daily glycerin enemas for treating chronic constipation and fecal impaction and sometimes recommends multiple glycerin enemas per day. “In some postoperative cases, such as with Hirschsprung's disease, we recommend administering it two or three times a day” to prevent stool leakage and diaper rash," Dr. Yokoi told me.

After my discussion with Dr, Yokoi, I felt entirely comfortable recommending U.S.-size glycerin enemas twice a day.

But I also began to wonder: Could Japanese-size glycerin-and-water enemas (GWE!) help my patients who can’t get empty on two small LGS per day?

I also thought: What about combining two daily GWE with overnight oil-retention enemas? Could that do the trick for kids who are relentlessly clogged?

In recent years, I have steered away from using large-volume enemas (the kind made with a bag enema kit) to treat enuresis. While saline-plus-glycerin enemas work well for encopresis-only patients, providing extra oomph to flush out stool, I believe large-volume enemas — with 300 ml to 600 ml total volume — stimulate too much rectal stretching for children with highly sensitive bladder nerves. I definitely would not recommend using large-volume enemas twice a day.

I suspect the Japanese-size GWE could be the Goldilocks solution: just right. In other words, powerful enough to facilitate greater evacuation than LGS but not so large as to aggravate sensitive bladder nerves.

What’s more, I believe the addition of overnight oil enemas could be the final piece in the puzzle for the tough cases.

I’ve been recommending oil-retention enemas for many years to my patients with fecal impaction. As doctors in the 19th century recognized, oil does a terrific job of softening crusty old stool, priming the hard mass to be flushed out by a stimulant enema in the morning. An 1892 medical journal described oil enemas as a “safe method of relieving even the most obstinate cases of spasmodic constipation,” and I concur!

But until recently, I had considered oil enemas a very short-term treatment — a jump-start to other M.O.P. variations, something to try for a few days or on weekends or school vacations.

I didn’t consider this approach might be helpful as a longer-term treatment for the toughest cases or perhaps just a faster ticket to dryness for more conventional cases.

However, my discussion with Dr. Yokoi prompted me to reconsider. For children with severe impaction, she commonly prescribes olive oil enemas in addition to glycerin. And the Japanese-style GWE — requiring only glycerin, water, and a syringe — has sufficient volume to clear out the detritus after an overnight oil enema. This is a much simpler wash-out procedure than the large-volume enemas I had been recommending.

Consistent with my experience, Dr. Yokoi told me that softening stool with olive oil makes glycerin enemas alone more comfortable and effective for her most impacted patients, for whom pooping is quite painful.

But it wasn’t just Dr. Yokoi who got me thinking about combining olive oil enemas with two-a-day glycerin enemas on an extended basis.

A few of our private support-group members posted that they kept their children on overnight oil enemas for more than a month, with great results. Their children experienced significant improvement with olive oil initially, and these parents didn’t want to tempt fate by changing the regimen until accidents had ceased.

Meanwhile, a handful of other parents have posted x-rays taken that show their children retained stool in the rectum despite more than two months of Multi-M.O.P. (with either LGS or Enemeez).

Based on all of the above, I am proposing the most aggressive M.O.P. variation yet: overnight oil enemas plus two-a-day Japanese-size GWE, continued daily until the child is reliably accident-free.

I used to define “reliably accident-free” as at least 7 accident-free days and nights. However, recently I have erred on the more conservative side, advising families to wait two to four weeks before starting a gradual taper. (I discuss the Slow Taper approach in the Anthology.)

Children who take a long time to empty are prone to filling back up quickly, and experience tells me that extending the daily-enema phase reduces the odds that accidents will recur, by giving the rectum more time to heal. As I often tell families: Our goal is to shrink the rectum, not to get off enemas asap (though certainly no one wants to keep doing enemas longer than is necessary!).

I recognize that J-M.O.P. is a hassle and may be logistically difficult for kids with after-school activities. It’s not the first regimen I'd recommend for, say, a 7-year-old whose only prior treatment has been Miralax. But I might recommend the protocol to a teenager who is desperate to get dry, and I would definitely recommend it for a child of any age whose x-ray shows rectal stool despite adherence to M.O.P.x or Multi-M.O.P. for at least six weeks.

If you’re unable to get an x-ray, you can reasonably assume your child is retaining stool if accidents have persisted after two months on M.O.P.x or Multi-M.O.P.

I should note that Dr. Yokoi’s study focused on fecal impaction and chronic constipation, not enuresis and encopresis. But since chronic constipation is the root cause of enuresis and encopresis, and since stubbornly impacted stool is the reason accidents persist, it stands to reason that combining olive oil with two GWE per day will do the job in the seemingly intractable cases of bedwetting, daytime accidents, and/or poop accidents.

Also of note: At Kobe Children’s Hospital, Dr. Yokoi told me, glycerin enemas are the go-to treatment for chronic constipation and fecal impaction. Doctors recommend PEG 3350 (Miralax) only in patients who are allergic to glycerin or are averse to enemas.

That’s the opposite of the approach taken in the United States, Canada, Europe, Australia, and New Zealand, where most physicians consider enemas “overly aggressive” and “traumatic” and default to PEG 3350, no matter how useless the treatment proves to be.

I’ve only just started recommending J-M.O.P. to my patients and parents in our private Facebook support group.

I will report back on the effectiveness of this regimen when more families have tried it.


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