Everyone has unusual bowel movements from time to time. Sometimes it's difficult to know whether these changes might be a sign of something serious.
Narrow stools, in particular, are frequently mentioned in articles about colorectal cancer, which raises the question: Can pencil-thin stools really be a warning sign of colon cancer?
According to Dr. Kirtan Nautiyal, a gastrointestinal medical oncologist at Houston Methodist, while thin or narrow stools alone aren't a reliable indicator of colon cancer, unexplained changes in stool shape or consistency shouldn't be disregarded, especially if you're experiencing one or more other signs of colorectal cancer.
Understanding colon cancer
Colorectal cancer develops when abnormal cells in the colon or rectum grow uncontrollably. These growths sometimes start as polyps on the lining of the colon or rectum.
If a cancerous polyp goes undetected, it can form into a tumor that grows into the wall of the colorectal tract. "From there, the tumor can spread to nearby lymph nodes and ultimately to other organs," Dr. Nautiyal warns.
Risk factors for developing colorectal cancer
As with many other types of cancer, certain health conditions and lifestyle factors impact a person's risk of developing colorectal cancer. Type 2 diabetes, obesity, a sedentary lifestyle, smoking and moderate to heavy alcohol use have all been linked to colorectal cancer. That's why partnering with your doctor to monitor and manage your overall health is so important.
Some of the risk factors for colon or rectal cancer can't be changed, including:
- Age: Most people diagnosed are over age 50
- Gender: It's more prevalent in men than in women
- Race: African Americans are 20% more likely to develop colorectal cancer
- Family history: About one-third of patients with colorectal cancer have family members who have had it
- Inflammatory bowel disorder (IBD): This includes people living with Crohn's disease or ulcerative colitis
Symptoms of colorectal cancer
The earliest stages of colorectal cancer, including polyps, don't cause obvious symptoms. When symptoms do appear, the warning signs can include:
- Rectal bleeding (blood in the stool)
- Changes in bowel habits (frequency of bowel movements or consistency of stool)
- Abdominal or pelvic pain
- Unexplained weight loss
- Loss of appetite or disinterest in eating
Fatigue is also common among patients with colorectal cancer. Dr. Nautiyal explains this can happen as tumor growth leads to blood loss.
"The loss of blood means the patient isn't getting enough iron in their system, so they develop iron-deficiency anemia and fatigue sets in," Dr. Nautiyal says. "Anyone with an iron deficiency, especially men and post-menopausal women, should get screened to rule out a polyp or cancer as the cause."
(Related: 7 Signs It's Time to See a Gastroenterologist)
When should you worry about thin stools?
It's normal for the size, shape and consistency of your stool to fluctuate, as is how often you go. You might occasionally have bowel movements that appear skinny, ribbon-like, flat or even stringy. Or you might experience diarrhea or constipation now and then.
Any of these may be caused by lifestyle factors or other health conditions such as:
- Changes in your diet (too much or too little fiber)
- Disruptions in your routine, such as travel
- Flareup of irritable bowel syndrome (IBS)
- Gastrointestinal infection
- Medication side effects
- Stress
"Colon cancer isn't the only — nor the most likely — explanation for thin, narrow stools, especially in the absence of other symptoms such as weight loss, abdominal pain and rectal bleeding," says Dr. Nautiyal. "If you're worried about a new or persistent change in stool consistency, it's important to consult your doctor."
(Related: Stool Colors: Brown, Green, Red, Black — What's Normal & What's Not?)
When to seek medical care
Unusual stools or bowel habits typically resolve on their own within a few days. If the symptoms last more than a week, talk with a doctor.
"What concerns us most is when patients develop more than one symptom at the same time," says Dr. Nautiyal. "If you have rectal bleeding, especially if it's dark, or abdominal pain along with your stool changes, talk with a doctor right away."
Depending on your age and symptoms, the doctor may recommend a colonoscopy. In this short outpatient procedure, a gastroenterologist will examine the interior of your rectum and colon using a thin, flexible, lighted tube.
"If you have pre-cancerous polyps, we can often find and remove them during a colonoscopy before they turn into something more serious," Dr. Nautiyal says. "When we can catch cancer early, it means better outcomes with less intensive treatment."
No matter what your stool looks like, it's important to follow your doctor's recommendations for regular colorectal cancer screening tests. For people with average risk, the guideline for colonoscopies is now age 45, with follow-up screenings every 10 years.
(Related: Why Even Young Adults Should Care About Colorectal Cancer Screening)
