If you have any combination of bloating, urgent bowel movements, stools that are mushy, sticky, or hard to wipe, and you “go” either zero or up to four times daily, this may surprise you:

You might actually be constipated.

By Audrey Inouye, Digestive Health Dietitian

More specifically, you may be dealing with overflow diarrhea—a commonly missed digestive issue where loose poop leaks around a moderate buildup of older poop stuck in the colon.

As a digestive health dietitian, this is one of the most misunderstood causes of ongoing gut symptoms I see. It’s also one of the most frustrating for people who have been trying for years to “fix their diarrhea” without success.

Common Signs of Overflow Diarrhea

Overflow diarrhea doesn’t look like what most people picture when they think of constipation. Many people with this condition have bowel movements every day—sometimes 3–4 times a day—which is why it’s often hard to diagnose.

Common signs often include two or more of the following:

• Bloating, often on most days
• Urgency, meaning you need to find a bathroom quickly
• Loose, mushy, or sticky stools that are messy and hard to clean
• Frequency, either several per day or too infrequently
• A feeling that you didn’t fully empty, even after going and going
• Straining, even when stools are soft
• Excess gas, pressure, or frequent passing of gas

You don’t need to have all of these symptoms. For many people, just two or more—especially when they happen together or keep coming back—can point toward overflow diarrhea.

Symptoms may:

• Start suddenly or build slowly over time
• Come and go, with periods where things seem better and then flare up again

This on-and-off pattern is a big reason overflow diarrhea is often mistaken for other digestive conditions.

How Overflow Diarrhea Is Diagnosed

Overflow diarrhea is usually diagnosed based on symptoms and history. When imaging is needed, the most useful test is an abdominal X-ray. I absolutely love abdominal X-rays because they show if there is a mild, moderate or high build up of stool and gas in the colon.  The amount and location of the build up will dictate the types of therapies that I decide to use.  

A few important things to know.  CT scans and ultrasounds do not commonly report on fecal loading unless it is extreme, like a full blockage. They do not report moderate fecal loading which is often the culprit of overflow diarrhea.  A normal colonoscopy does not rule this out, because the bowel is emptied before the test

This is another reason overflow diarrhea is commonly missed—by both patients and healthcare providers.  However, it can be easily detected with an abdominal X-ray! 

What’s Actually Happening in the Body

Your colon is a muscle.  When stool sits in the colon for a long time, the muscle stretches out. Over time, it becomes weaker, less responsive and less aware that stool is even there.  Eventually, the colon struggles to push old stool forward.  

Here’s the key part:

When new food moves into the colon from the small intestine, that stool is softer. Instead of pushing out the older, stuck stool, the softer stool pushes around it—the path of least resistance.  It is often soft, mushy, watery, and/or urgent. 

That’s overflow diarrhea.

The result is loose or mushy stools, urgency, multiple trips to the bathroom, and a messy uncomfortable clean-up.  Meanwhile, the older stool stays behind, and the confusing cycle continues.

What Causes Overflow Diarrhea?

Overflow diarrhea happens when stool builds up faster than the colon can move it out. Common contributors include:

• Prescription medications, pain medications, and/or supplements that slow digestion 
• Diets that are either too low or too high in fibre
• Conditions that contribute to constipation such as small intestinal bacterial overgrowth (SIBO), intestinal methanogen overgrowth (IMO), irritable bowel syndrome (IBS),  pelvic floor dysfunction, gastroparesis, low thyroid, etc
• Prostate conditions or previous treatment for prostate cancer
• Past GI illness or surgery
• Aging, perimenopause and menopause
• Autonomic conditions like mast cell activation syndrome (MCAS), postural orthostatic tachycardia syndrome (POTS), and Elher’s Danlos
• Simply not realizing you were constipated to begin with

For most people, it’s not one single cause, but a slow buildup over time.

Treatment: Why This Takes Time (and Why That’s Normal)

The hardest part of treating overflow diarrhea is recognizing it in the first place.

Once it’s identified—based on symptoms and sometimes an abdominal X-ray—treatment can begin. It’s important to know that clearing out extra stool is not instant. For most people, it takes 2–4 weeks, and sometimes longer.

Treatment usually includes:

• An individualized GI-gentle diet that non-restrictive and doesn’t add to stool buildup
• An excellent bowel regimen
• Gentle, evidence-based supplements, guided by GI guidelines
• Supporting the colon to empty more completely each day

During this time, the colon has to work harder, like 110% everyday. But that’s a good thing!

Just like any muscle, the colon gets stronger when it’s able to contract and move normally again. As stool clears out, the muscle can regain strength and sensitivity. Over time, symptoms like urgency, bloating, and messiness usually improve, usually around 2-4 weeks. 

There’s no one-size-fits-all plan. What works depends on your body, your history, and how your gut responds.  

Where a GI Dietitian Fits In

This is where my role comes in.  As a digestive health dietitian, it is my job to triage whether your symptoms are from a diarrhea related disorder or from constipation-induced overflow diarrhea.  I help recognize when overflow diarrhea is likely, reduce stool buildup without making symptoms worse, and adjust the plan based on what’s helping—and what isn’t.  I coach people through the ups and downs of this journey. 

If you’ve been told you have diarrhea but nothing seems to work, overflow diarrhea may be the missing piece.

The good news?

Once it’s recognized, it’s very treatable—with the right approach and enough time for your colon to recover.