Paradoxical diarrhea happens when loose, watery stool finds a way around hardened, impacted stool in your colon and leaks from your anus.

Also called overflow diarrhea, it’s often a symptom of a type of irritable bowel syndrome (IBS) called mixed IBS (IBS-M).

Normally, when you’re constipated, hardened stool blocks other stool from passing through the colon. This is called fecal impaction. But when the pressure of other stool builds up behind hardened stool, liquid can start to leak through and pass out of the anus. This leads to symptoms of diarrhea and constipation at the same time.

Read on to learn more about the symptoms of paradoxical diarrhea, what can cause it, and when you should get medical help.

Paradoxical diarrhea symptoms are similar to those of both constipation and diarrhea.

Here are some of the symptoms you might experience when you first start getting constipated:

  • not having a bowel movement for a few days or having fewer than three movements a week
  • having stools that are dark, hard, and dry
  • not being able to have a bowel movement without pushing or straining
  • not feeling like you’re done on the toilet after having a bowel movement

After a few days, you might start noticing watery stool when you sit down on the toilet. Even if you pass a lot of watery stool, you still might not feel like you’re done. This is paradoxical diarrhea.

Other symptoms include:

Paradoxical diarrhea is a common symptom of IBS-M. There’s no specific known cause of IBS-M.

Diet or lifestyle triggers can cause constipation and diarrhea, especially if you have:

Bacterial infections can also cause paradoxical diarrhea.

An overgrowth of unhealthy bacteria can disrupt your body’s ability to digest food and result in both constipation and diarrhea. This disruption can last for months until healthy gut bacteria can regrow.

Complications of paradoxical diarrhea are rare if you treat it or if it resolves on its own.

Over time, however, untreated paradoxical diarrhea can cause:

Short periods of diarrhea and constipation aren’t a big cause for concern.

However, you should get medical help if you have symptoms of diarrhea, constipation, or both for longer than a week or if you notice any of the following symptoms:

To diagnose paradoxical diarrhea, a doctor might:

  • run a medical history to understand your overall health
  • do a physical exam to look for any signs of illness
  • perform a digital rectal examination to find impacted stool
  • suggest an X-ray or CT scan of your abdomen to look for impacted stool
  • recommend an enema with contrast dye to more easily see impacted stool or other issues in your colon

Some treatment options for paradoxical diarrhea include:

  • digital disimpaction, where a doctor uses a lubricated glove to insert a finger into your anus and loosen impacted stool
  • an enema that flushes out hardened stool with fluids
  • laxatives to trigger your intestinal muscles to contract and release impacted stool

Speak with a doctor before trying any of these medications or treatments to relieve symptoms.

Preventing constipation is the best way to prevent paradoxical diarrhea.

Here are some tips on how to prevent constipation:

  • Drink enough water every day to stay hydrated.
  • Eat plenty of fiber, like raw fruits and vegetables or legumes like beans and lentils, to help stool move through your gastrointestinal tract more easily.
  • Add probiotics to your diet to help improve the health of your gut bacteria.
  • Reduce or eliminate caffeine and alcohol, as these can dehydrate you.
  • Get at least 150 minutes of moderate intensity aerobic exercise each week to help keep your bowel muscles moving.

Here are some of the most frequently asked questions about paradoxical (overflow) diarrhea.

What does overflow diarrhea look like?

Overflow diarrhea looks like loose and watery stool that can suddenly come out when you sit down on the toilet but have constipation. It might also have blood or mucus in it.

Is paradoxical diarrhea dangerous?

Short episodes of paradoxical diarrhea aren’t dangerous. But over time, impacted stool and inflammation in your intestines from paradoxical diarrhea can increase your risk of complications.

How long does paradoxical diarrhea last?

Paradoxical diarrhea might only last for a few days, especially if you make diet or lifestyle changes to help yourself have a bowel movement. But if you have a condition like IBS-M or a severe bacterial infection, paradoxical diarrhea can last for weeks or more. Speak with a doctor or get medical help if you have long episodes of paradoxical diarrhea.

What can cause constipation followed by explosive diarrhea?

IBS-M is a common cause of constipation followed by explosive diarrhea.

Other causes include:

  • bacterial infections
  • stress
  • a lack of fiber in your diet
  • dehydration

Why do I feel like I have diarrhea but can’t poop?

Hardened stool stuck in your colon can cause liquid behind it to build up to high pressures. When the pressure is high enough, liquid can seep around the hardened stool and leak out through the anus.

This may continue until you finally pass any hardened stool that might be causing blockages in your colon.

Paradoxical diarrhea is when you’re constipated and have diarrhea at the same time. It’s often a result of IBS-M or a trigger like a bacterial infection or stress.

Paradoxical diarrhea that lasts for a few days isn’t a cause for concern, but it’s best to seek medical help if it lasts for a week or more.