Thin Stool

Although it may be uncomfortable, it is important to look at your stool after going to the bathroom. The stool can tell you a lot about what is going on inside your body. Stool can have various characteristics, from hard and lumpy to mushy or watery.

What does it mean when the stool is thin? This article discusses the symptom of thin stool and its potential causes. It also discusses when to seek medical advice for this symptom.

Symptoms of Thin Stools

The stool produced in the intestines may appear in various ways and can change from day to day. Generally, stool should be brown (though it may have a different color depending on what has been eaten) and soft enough to pass easily, without straining.

Stool that is thin or narrow when it comes out can occur from time to time. The occasional thin stool isn't usually a cause for concern, as long as bowel movements are otherwise normal. If the stool continues to be thin and regular bowel movements no longer occur, it's time for evaluation. 

Thin stools may be described as long and pencil thin. The normal, more rounded shape is lost. It may be harder to pass and require more straining or bearing down when trying to go. 

Depending upon the cause, thin stool may be accompanied by other symptoms, such as:

• Abdominal pain
• Weight loss
• Bloating
• Blood mixed in or on the stool

Causes of Thin Stools

There can be many reasons for thin or narrow stools. As previously mentioned, it’s something that may just happen occasionally without any known cause. When it's frequently happening, the causes may include:

• Constipation
• Colorectal cancer, including anal cancer
• Fecal impaction
• Internal hemorrhoids

Constipation

Thin stools can signal constipation. With constipation, stool passes slowly through the intestines, which allows the intestines to absorb more water from the stool, making it even more difficult to pass. If there is significant constipation, only thin amounts of stool may be able to pass through.

Colorectal Cancer

A cancerous mass in the intestine, or closer to the end, near the anus, can cause thin stools. If the mass is large enough to block the stool’s movement through the intestine, pencil-thin stool may be the only thing that is able to move through. Other symptoms associated with colon cancer include:

• Abdominal pain
• Blood in the stool
• Unintentional weight loss

Fecal Impaction

Fecal impaction is similar to constipation, but in the case of fecal impaction, a lump of dry stool is stuck in the rectum (the bottom portion of the colon just before the anus). This blocks the ability of other stool to move through normally, and the blockage may allow only a thin amount of stool to pass.

Internal Hemorrhoids

Internal hemorrhoids are swollen and inflamed veins in the rectum or anus that don't extend outside the anus. If they are large, they can block stool passage and result in thin stool. Internal hemorrhoids may cause rectal bleeding.

What Medications Can Cause Thin Stools?

Medications that slow the movement of the intestines can cause thin stools. They can lead to constipation and possible fecal impaction, causing thin stool. Some of the medications that can do this include:

• Opioid pain medications, such as morphine or hydrocodone
• Anticholinergics, such as scopolamine or oxybutynin
• Antidiarrheal medications, if taken too often

How to Treat Thin Stools

There’s no one specific treatment used for thin stools. Treating the underlying condition can help the stool return to a normal appearance. 

To treat constipation, increasing fiber in the diet is important. Additionally, staying well hydrated can help as well.

Medications may be necessary for those whose stools don’t improve enough through dietary changes or drinking extra water. These medications can include laxatives which help stimulate the intestine to pass stool, or stool softeners, which can make the stool easier to pass by allowing the stool to retain water and fat cells.

Treatment for colorectal cancer can vary, depending on how advanced the cancer has become. Surgery to remove the mass is a common procedure and may be followed by chemotherapy or radiation, or both.

Fecal impaction is treated by removing the stuck stool in the rectum. This can be done manually by a healthcare provider who will use a well-lubricated, gloved hand to insert a finger or two into the rectum to help break up the stool so it can be removed. Interventions such as suppositories or enemas may also be used.

Hemorrhoid symptoms are often relieved with nonsurgical methods such as more water and fiber or fiber supplements in the diet to soften the stool and avoid straining while defecating. If the hemorrhoid prolapses (extends beyond the anus) or becomes thrombosed (a clot forms in it), surgery may be done.

Complications Associated With Thin Stools

Though there are no specific complications associated with thin stool, the underlying condition causing the thin stool needs to be addressed before complications develop such as complete bowel obstruction or further growth and spread of cancer. 

Are There Tests to Diagnose the Cause of Thin Stools?

A healthcare provider may recommend tests to help determine the cause of thin stools. Tests that may be done to look for the cause of thin stools can include:

• Digital rectal examination: A healthcare provider performs this exam to see if they can feel any mass inside the rectum.
• Stool tests: A sample of stool is sent to a lab and can be analyzed for potential causes, such as bacteria or other infections, parasites, or blood
• Colonoscopy: During this procedure, a camera is inserted into the colon to look for any areas that may be abnormal or causing the symptom of thin stool. If something looks abnormal, a biopsy (sample) can be taken for testing.

When to See a Healthcare Provider 

The occasional episode of thin stool is likely not a cause for concern. However, if thin stools occur more frequently, notify a healthcare provider. Blood in the stool is always a reason to talk to a healthcare provider.

If thin stools aren’t responding to what you’re doing to improve them (such as increasing fiber) or are accompanied by other symptoms, such as abdominal pain or weight loss, notify a healthcare provider.

Summary 

Thin stool can be a symptom that occurs at times but is not usually concerning. Causes include constipation, colorectal cancer, and fecal impaction. Thin stools require evaluation if they persist or are accompanied by other symptoms, such as blood in the stool or abdominal pain. Tests can be done to help find the cause.

A Word From Verywell

It may be awkward to talk about the appearance of your stools, but producing stools is an important function of the body, and it helps to be aware of its appearance. If you see changes in your stool, discuss them with a healthcare provider.