IBD (Crohn's and Ulcerative Colitis): Stool Changes to Watch For
Bristol Types 6-7 in IBD context - Updated September 2026
What Is IBD? Crohn's Disease vs Ulcerative Colitis
Inflammatory Bowel Disease (IBD) is a term encompassing two major conditions: Crohn's disease and ulcerative colitis (UC). IBD is fundamentally different from IBS (Irritable Bowel Syndrome): IBS is a functional condition with no visible inflammation; IBD involves structural inflammation, ulceration, and tissue damage that can be seen on endoscopy, imaging, and biopsy.
Crohn's Disease
- Can affect any part of the GI tract (mouth to anus)
- Transmural inflammation (through all layers of gut wall)
- Skip lesions (patches of inflammation separated by normal tissue)
- Associated with fistulas, abscesses, strictures
- Diarrhoea, abdominal pain, weight loss, fatigue
Ulcerative Colitis
- Affects only the colon (large bowel), always includes rectum
- Mucosal inflammation (inner layer only)
- Continuous inflammation from rectum upward
- Rectal bleeding and urgency are hallmark symptoms
- Bloody diarrhoea, tenesmus, urgency, cramping
IBD is diagnosed through colonoscopy with biopsy, blood tests (raised CRP, low albumin, anaemia), faecal calprotectin (a stool inflammation marker), and imaging (MRI for Crohn's, CT). Unlike IBS, IBD has biomarkers. If you have rectal bleeding with diarrhoea, your GP should not label it as IBS without investigation.
Bristol Stool Types in IBD Flares
During an IBD flare, stool type typically shifts towards types 6 and 7 - mushy, ragged pieces or entirely liquid. In UC, blood and mucus are often visible mixed through the stool, which is not typical of IBS-D and is a key distinguishing feature. In Crohn's affecting the ileum or upper colon, stools may be type 5-6 without blood (particularly in ileostomy patients where rectal blood is not possible). In Crohn's involving the colon or rectum, blood may be present similarly to UC.
Flare Warning Signs on the Bristol Scale
A sustained shift over 3-5 days, without dietary or medication explanation, may signal early flare activity.
Blood mixed through stool (not just on paper) is a hallmark of colonic IBD activity. Contact your IBD nurse specialist.
On the Truelove and Witts index reproduced in NICE NG130, severe UC is 6 or more bowel movements a day with blood, plus at least one feature of systemic upset (pulse above 90, temperature above 37.8C, anaemia, or ESR above 30). Six counts, not just more than six. Hospital admission may be required.
Nocturnal bowel symptoms are organic, not functional - IBS does not typically cause night-waking. This always requires investigation.
Toxic megacolon is a rare but life-threatening complication of UC. Signs include distended abdomen, fever, rapid pulse, and reduced bowel sounds. Emergency presentation.
How Tracking Helps IBD Management
Logging Bristol type, frequency, blood presence, urgency, and pain daily gives you and your IBD team a concrete dataset to review. Pattern shifts in stool type - even subtle ones over 5-7 days - can sometimes precede a full clinical flare by days to weeks, allowing earlier treatment initiation.
Our private bowel tracker includes a symptoms field where you can log blood, mucus, pain, and urgency alongside stool type. Export the CSV and share it at your IBD clinic appointment. Many gastroenterology departments now welcome patient-generated outcome data for consultations.
The Harvey-Bradshaw Index (for Crohn's) and Simple Clinical Colitis Activity Index (SCCAI, for UC) are clinical scoring tools that use stool frequency and blood as inputs - exactly what this tracker records. See Crohn's and Colitis UK for condition-specific resources and NHS helpline access.
Distinguishing IBS from IBD on Bristol Pattern Alone
| Feature | IBS-D | Active IBD (UC/CD) |
|---|---|---|
| Blood in stool | Absent (if present, investigate) | Common, especially in UC |
| Mucus | Can occur, usually small amounts | Common, often visible |
| Nocturnal diarrhoea | Unusual / not typical | Common in active disease |
| Weight loss | Uncommon | Common in active disease |
| Fever | Absent | Present in severe flare |
| CRP / calprotectin | Normal | Elevated |
| Colonoscopy | Normal | Visible inflammation/ulceration |
| Symptom onset | Chronic, stress-related | Can be acute, progressive |
Updated September 2026. This page does not provide medical advice. If you have diagnosed IBD, follow your IBD team's specific guidance. In doubt, call your IBD nurse helpline.