What does poop look like with diverticulitis?
People often check the toilet during a flare, hoping it will say something about what is happening. Diverticulitis does not produce one recognisable kind of stool, but there are changes that are common and expected, and a few that need medical attention whatever else is going on.
There is no single diverticulitis stool. During a flare many people have constipation, some have diarrhea, and some notice mucus. On a clear liquid or low-fiber diet, stools become smaller and less frequent, which is expected. Black, tarry stools, maroon or bright red blood, or stool that stays pencil-thin are not normal diverticulitis signs and need a doctor promptly. Doctors diagnose diverticulitis from symptoms, examination and usually a CT scan, not from how stool looks.
Common stool changes during a flare
- Constipation. The most common change. Inflammation slows the bowel, pain makes people avoid straining, and eating little means less stool
- Diarrhea. Some people have looser stools instead, or alternate between the two
- Mucus. A small amount of clear or white mucus can appear with an inflamed bowel
- A feeling of not quite finishing, or needing to go more often in small amounts, when the inflamed section is low in the colon
These changes usually come with the symptoms that matter more for diagnosis: pain, most often low on the left side of the abdomen, and sometimes fever, nausea or bloating. What diverticulitis pain feels like covers how to describe it.
What changes during recovery
On clear liquids and low-fiber food
When you are eating very little fiber, there is simply less stool. Going every two or three days, with smaller and softer stools, is expected at this stage and not a sign that something is wrong, as long as you are passing wind and your pain is settling.
As fiber comes back
Stools become bulkier and more regular, and some extra wind and bloating is common for the first few weeks. A soft, formed stool that is easy to pass, type 3 or 4 on the Bristol stool scale, is the goal. Fiber after diverticulitis covers how fast to add it back.
| What you see | Usually means | What to do |
|---|---|---|
| Small, infrequent stools on a low-fiber diet | Expected with little fiber | Keep drinking; stools pick up as fiber returns |
| Hard, lumpy stools | Constipation | Fluids, and fiber once your doctor says the flare has settled |
| Loose stools for a day or two | Common during a flare or on antibiotics | Keep fluids up; call if it lasts or you feel dizzy |
| A little clear mucus | Can happen with an inflamed bowel | Mention it at your follow-up |
| Black, tarry stool | Possible bleeding higher in the gut | Contact a doctor the same day |
| Maroon or bright red blood | Bleeding in the colon | Urgent care, especially if there is a lot |
| Stool that stays pencil-thin | Possible narrowing | See your doctor; it needs checking |
Blood in the stool
Bleeding from diverticula is real, but it usually comes from diverticulosis, the pouches themselves, rather than from diverticulitis, the inflammation. It is typically sudden and painless, and can be a large amount of bright red or maroon blood. Any blood in the stool needs a doctor, and heavy bleeding, dizziness or fainting need emergency care. Diverticulosis vs diverticulitis explains the difference.
Narrow or pencil-thin stools
An occasional thin stool is common and means little. Stools that stay narrow over weeks can point to a narrowing of the bowel, which can follow repeated flares, or less commonly to another cause such as a growth. This is one reason a colonoscopy is often advised some weeks after a flare. If your stools have changed shape and stayed that way, tell your doctor rather than waiting.
When to get help
- Black, tarry stools, or any blood that is more than a streak
- Not passing stool or wind, with a swollen abdomen or vomiting
- Diarrhea for more than a couple of days, or signs of dehydration
- Fever, or pain that is getting worse rather than better
- A change in bowel habit or stool shape that lasts beyond your recovery
If pain or bowel changes are dragging on for weeks, diverticulitis pain lasting months covers the usual explanations and the tests that tell them apart.
Frequently asked questions
What does poop look like with diverticulitis? +
There is no single look. Constipation is most common during a flare, some people have diarrhea, and some notice mucus. Black stools, maroon or bright red blood, or stool that stays pencil-thin are not typical and need a doctor.
Does diverticulitis cause constipation or diarrhea? +
Either. Constipation is more common, but some people have looser stools, and some alternate. Antibiotics can also loosen stools.
Is it normal not to poop much during a diverticulitis flare? +
On clear liquids or a low-fiber diet there is less stool, so going every two or three days is expected, as long as you are passing wind and pain is settling. Not passing stool or wind with a swollen abdomen or vomiting needs a doctor.
Does diverticulitis cause blood in stool? +
Bleeding from diverticula usually comes from diverticulosis rather than diverticulitis, and is often sudden and painless. Any blood in the stool needs a doctor, and heavy bleeding needs emergency care.
Can diverticulitis cause thin stools? +
An occasional thin stool means little, but stools that stay narrow can point to a narrowing of the bowel and should be checked by a doctor.
This article is general information from Velora Health, not medical advice. It does not replace an assessment by a clinician who knows your history. If you have heavy bleeding, black stools, severe or worsening abdominal pain, a fever, or you cannot pass stool or wind, contact your doctor or your local emergency number now.