Confused over what “diarrhea alternating with constipation” actually means?

The commonly used phrase, diarrhea alternating with constipation, is sometimes seen in symptom lists for colon cancer and IBS, even ovarian cancer.

And it’s ambiguous. I asked for an elaboration from Matilda N. Hagan, MD, an inflammatory bowel disease specialist at The Center for Inflammatory Bowel and Colorectal Diseases, part of The Melissa L. Posner Institute for Digestive Health and Liver Disease at Mercy Medical Center in Baltimore.

Alternating Diarrhea and Constipation with IBS

Dr. Hagan explains, “Generally speaking, ‘diarrhea alternating with constipation’ is specific to ‘mixed type irritable bowel syndrome.’

“This means a person has changes in their bowel habits such that at times they have diarrhea (well-known to be change in consistency of stool from formed to loose or liquid) or constipation where there is a decrease in frequency of bowel movement and/or passage of hard pellet-like stool.

“For some they may have normal formed stool in between or go from one extreme to the other.

“As far as timing, skipping three or more days without a bowel movement counts as constipation, especially if it is associated with abdominal discomfort or bloat.”

Alternating Diarrhea and Constipation

with Colon Cancer

You may have read that colon (or ovarian) cancer may cause “diarrhea alternating with constipation.”

The aafp.org site states for colon cancer: “Constipation may be constant or may alternate with diarrhea.”

It’s that word “alternate” or “alternating” that throws things off. The aafp.org site states that in colon cancer, the “alternating constipation and diarrhea signify leakage of liquid stool” that’s “around the lower level of a tumor.” The cancer is “partially obstructing the bowel.”

What else can alternating diarrhea and constipation mean?

As Dr. Hagan explains, relative to IBS, it’s a time period of diarrhea, followed by a time period of constipation, and constipation is defined as three-plus days without a bowel movement and/or voiding hard, pellet stools.

Constipation can also mean straining hard to void hard stools, not necessarily pellet shaped; they can be larger chunks—but hard, necessitating a lot of straining and discomfort while you’re on the toilet seat.

You may even be having normal frequency of BMs, but nearly every time, they are hard and require heavy straining.

What if in between these episodes, you have diarrhea? This would fall under the category of “alternating.” The in-between episodes themselves can vary.

For instance, Monday, Tuesday and Wednesday you have BMs—all hard and requiring straining.

But Thursday you have diarrhea. Friday you strain and void hard poops. Saturday, diarrhea. Sunday, diarrhea. Monday, a few hard, straining bowel movements. Wednesday, diarrhea.

You get the picture. Any given day is either all diarrhea or all constipation.

Another scenario is that on a given day, you have both diarrhea and constipation. The day after may be all diarrhea—or all constipation.

Or maybe in between normal voiding days (formed non-hard stools), you have days of both constipation and diarrhea.

There are benign causes like IBS and food intake, but potential (less likely) serious causes like colon and ovarian cancer, and Crohn’s disease.

In short, the concept of diarrhea alternating with constipation comes with multiple permutations.

No particular permutation points to colon or ovarian cancer! Dr. Hagan says, “If the symptoms are present for three months or longer,” you should “consider discussing with a health care professional.” However, if the symptoms come with other issues such as unexplained weight loss, pelvic or stomach pain, back or leg pain, poor appetite or new-onset fatigue, don’t wait longer than two weeks to make a medical appointment. If you see blood in your stools, make the soonest appointment.

Source: aafp.org/afp/2000/0315/p1759.html#sec-7