One confusing (and surprisingly common) situation is when it looks like diarrhoea… but it’s actually severe constipation. This phenomenon is called constipation overflow, and if you’ve ever been caught off guard by unexpected loose stools despite feeling “blocked up,” this article is for you.
Let’s break down what constipation overflow is, how it’s diagnosed, and how to manage it — especially if you’re navigating life with IBS.
What Is Constipation Overflow?
Constipation overflow — also known as overflow diarrhoea — happens when hardened stool builds up in the colon or rectum, blocking the passage. As more stool is produced, the only way for it to escape is around the blockage, so what leaks out is watery, mushy stool or mucus. This can look and feel just like diarrhoea, but the root cause is actually severe constipation.
It’s basically your gut saying: “I’m full, and this is the only way out.”
Common signs of constipation overflow:
- Frequent small leaks of loose or watery stool
- Feeling of incomplete emptying after a bowel movement
- Bloating, abdominal discomfort, or cramping
- Urgent diarrhoea after a period of constipation that results in accidental soiling or “accidents” (especially in children or older adults)
- A long-standing pattern of constipation
- Alternating between constipation and what seems like diarrhoea
If you’re dealing with IBS, especially IBS-M (mixed) or IBS-C (constipation-predominant), this can be especially tricky to identify. It’s not uncommon to assume you’re having an IBS-D flare — when in reality, it’s the backlog of stool causing all the trouble. It’s important you talk to your doctor to get the constipation overflow diagnosed.
How Is Constipation Overflow Diagnosed?
A healthcare provider may suspect constipation overflow based on your symptoms and bowel habits. The diagnosis process often includes:
1. History & Symptom Review
They’ll ask about how often you go, stool consistency (get familiar with the Bristol Stool Chart), bloating, abdominal pain, and accidents.
2. Physical Exam
A gentle abdominal exam may reveal firm stool buildup. A digital rectal exam can detect stool right in the rectum.
3. Imaging (if needed)
In more persistent cases, an abdominal X-ray or ultrasound might be used to confirm large amounts of retained stool.
How to Manage Constipation Overflow
Before you can manage or prevent constipation overflow, you need to remove the backed-up stool in the colon or rectum. Think of it like clearing a traffic jam — until the blockage is gone, nothing is moving the way it should. Once the poo traffic jam is gone, you can switch your focus to long-term constipation management.
Options for clearing the blockage:
Senna Based Laxatives
These products are a combination laxative that includes docusate sodium (a stool softener) and sennosides (a stimulant laxative). They are often marketed under the brand names Coloxyl & Senna, Senokot-S, PeriColace, or Senna Plus.
These products need to be taken every day for 1-2 weeks until the stool backup has been cleared.
Note, Senna based laxatives are not suitable for longterm use. So once the backlog is cleared, you will need to switch to a different option or use dietary strategies.
Osmotic Laxatives
These work by drawing water into the stool and makes it easier to pass. Osmotic laxatives are suitable for long term use if needed.
Common options:
- Polyethylene glycol (PEG) – brand names like Miralax, Movicol or Osmolax
- Lactulose – a synthetic sugar that softens stools
- Magnesium citrate or magnesium hydroxide – can be helpful short-term
Start with a low dose and increase slowly. These laxatives may take 24–72 hours to fully work. To help the process, continue to drink plenty of water alongside laxatives.
Enemas & Suppositories
If stool is backed up in the lower colon or rectum, you may need something that works locally and faster.
Options include:
- Glycerin suppositories – stimulate the rectum gently
- Saline enemas (e.g., Fleet enema) – work quickly to soften and flush stool
- Mineral oil enemas – lubricate and ease passage
These options work within 15 minutes to 1 hour. Make sure you use them in a private and comfortable space near a bathroom. Please note that enemas should only be used occasionally as frequent use can irritate the bowel and reduce your body’s natural signal to go.
Manual Disimpaction (In Severe Cases)
If the stool is extremely hard and impacted, especially in the elderly or children, your healthcare provider may need to manually remove it. This is usually done gently using a gloved, lubricated finger and may involve local anesthesia or stool-softening agents beforehand.
This is not something to attempt at home. It’s a medical procedure done in a clinical setting and only when necessary.
What to Expect During the Clearing Process
While your body clears out the excess stool, you might experience some unpleasant symptoms:
- Cramping or bloating as your colon starts moving again
- Multiple trips to the bathroom over several hours or days
- Loose stool initially as the blockage clears — this is normal!
Stay close to a bathroom and be kind to your body. Rest, hydrate, and avoid heavy meals during this process.
When to Seek Medical Help
Please reach out to a healthcare provider if you experience any of these:
- You have not passed stool for several days and laxatives aren’t working
- You feel severe abdominal pain, vomiting, or fever
- There’s blood in your stool
- You suspect a child or elderly person has a blockage
Next Steps
Clearing the blockage safely is the first step toward long-term relief. Once things are moving again, the next goal is to prevent it from happening again by following constipation and IBS-M management strategies.
Final Thoughts
Overflow diarrhoea as a result of constipation can be incredibly confusing — especially when it presents like diarrhoea. But recognising it is a major step toward feeling better and staying regular. If you’re seeing a pattern of inconsistent stools, bloating, or accidents, it’s worth bringing up with your healthcare provider.
You’re not alone in this, and with the right support, your gut can feel a whole lot more predictable.
Image credit: MMD Creative/Shutterstock.com
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