Do You Have Stringy or Fibrous Poop? Here’s What Can Cause It

Many people make a habit of checking what their poop looks like. So if you peek in the toilet after a bowel movement, you aren’t alone. In fact, there’s a good reason to do this. Changes in your poop can give you information about your digestion. It can even be a sign of certain medical conditions. Here we discuss causes of fibrous or stringy poop and when it might mean there’s something else going on.

What do fiber strings in your poop look like?

Fiber strings look like undigested food in your poop. They look similar to threads. For example, if you eat a lot of bananas, you may notice stringy black lines in your poop. These are from the center of the banana. And sometimes fiber strings look like straws of undigested food. Like a long, thin piece of carrot, for example.

But here’s where things can get a little tricky. Depending on who you ask, stringy poop can mean different things. They might be referring to long, narrow poops. This is also sometimes called shoestring poop, because of how long and thin it is. And this is different than just seeing stringy fiber in your poop. So in the next section, we go through a list of what can cause this.

What causes stringy poop?

Fiber strings in your poop come from partially digested fiber from the food you eat. This is because fiber is hard to digest — just one of the reasons fiber is so good for your gut health. 

Long, narrow, stringy poop has a few more causes. And since some of these can be a little more serious, we go through them in more detail below.

Changes in your routine

Certain disruptions in your usual schedule may also have an effect on what your poop looks like. For example, if you’re traveling, you may not be going to the bathroom as often. Or if you’re less physically active, you may be pooping less, and your poop may look narrower than usual. 

How much water you drink

Drinking water can help push your poop out of your body, making it less likely for you to become constipated. If you have a few days when you’re drinking less water than you normally do, you may notice that your poop looks thinner than usual.

Medical conditions

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder that leads to changes in a person’s poop. Sometimes, IBS can cause mucus in the stool. This can give poop a stringy appearance. Other GI disorders like Crohn’s disease and ulcerative colitis may also cause bloody mucus in a person's poop, giving it a stringy appearance. 

Infections

Certain infections caused by bacteria or parasites can lead to diarrhea, causing poop to look stringy. And some viruses can also cause loose stools — think of your typical 24-hour stomach bug that has you repeatedly visiting the toilet. Any of these types of infections is likely to cause more than stringy-looking poop. In these cases, you’ll probably have symptoms like fever, nausea, vomiting, and stomach cramps.

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Colorectal cancer

In rare cases, colorectal cancer can also cause poop that appears narrower. But this is a less common cause of shoestring poop. And thin poop alone is usually not a reason to worry about colorectal cancer. Rather, a person with colorectal cancer may experience narrow stools as well as bleeding from the rectum, weight loss, and noticeable changes in their poop that don’t go away after a few days.

Other medical conditions

Other reasons that a person may have narrower poop than usual are rare but include:

• Polyps in your colon: Sometimes a person can have small growths or polyps in their colon. Most often, they aren’t dangerous. They may lead to changes in poop, including thin-looking stool.

• Bowel obstruction: A bowel obstruction is a blockage in the intestine. This can be caused by things like scar tissue from past surgery, infections, and even severe constipation. Along with a noticeable decrease in bowel movements, this also causes pretty severe stomach pain.

• Fecal impaction: When a person’s poop builds up in their rectum, it can cause what’s known as a fecal impaction. In this case, a person may not be able to push out any poop. Or if they’re able to, it may come out in very small or thin pieces.

• Anal stenosis: In rare cases, a person may have a narrowing of their anal canal, which is where poop passes through to exit the body. This is sometimes referred to as an anal stricture. It can cause poop to look thinner. 

When are fiber strings in your poop a sign of a problem?

It’s not uncommon to see a few fiber strings in your poop, or notice that your poop looks different than it normally does. But if you’re experiencing fiber strings or stringy stool in addition to the following symptoms, you’ll want to speak with your healthcare professional right away:

• New or severe abdominal pain

• Blood in your poop, which can look bright red or even black like tar

• Loss of appetite

• Nausea and vomiting

• Weight loss 

Even without these symptoms, it never hurts to check in with a medical professional if these poop changes won’t go away. 

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Written by:

Cherilyn Davis, MD

Cherilyn Davis, MD, is a board-certified pediatrician in New York City. She has held local and national roles at the American Medical Women’s Association including board member of the physician division and physician chair of social media.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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