Introduction: When Diverticulosis Isn’t the Full Story
If you’ve been diagnosed with diverticulosis, you’ve probably been told it’s harmless — a common finding during colonoscopy that requires little more than a high-fiber diet. But what happens when you start experiencing chronic rectal bleeding, loose stools, or mild left-sided abdominal pain, even when there’s no infection?
These symptoms might not be a simple case of diverticulitis or hemorrhoids. Instead, they may signal a lesser-known condition called Segmental Colitis Associated with Diverticulosis (SCAD) — an inflammatory disorder that targets the same part of your colon affected by diverticulosis, especially the sigmoid region.
Though often overlooked or misdiagnosed, segmental colitis in diverticulosis is a real and distinct condition. This article breaks down how it develops, how it differs from other GI issues, and how it can be effectively managed once correctly identified.
What Is Segmental Colitis in Diverticulosis?
Segmental colitis is an inflammation of the mucosal lining in parts of the colon already affected by diverticulosis, especially the sigmoid colon. Unlike diverticulitis, which involves infection of the diverticula themselves, segmental colitis affects the tissue between the diverticula — leading to a unique and localized inflammation pattern.
This condition tends to:
- Occur in older adults, often over age 50
- Present without systemic illness like fever
- Be confused with inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS)
Because many doctors assume rectal bleeding in diverticulosis is due to either hemorrhoids or diverticular bleeding, this under-the-radar inflammation is frequently missed.
Why Segmental Colitis Happens in Diverticulosis Patients
The causes of segmental colitis in diverticulosis are not entirely understood, but researchers believe several factors contribute:
1. Impaired Blood Flow (Ischemia)
The sigmoid colon has a vulnerable blood supply, especially in older adults. When blood flow is reduced or inconsistent, it can lead to inflammation of the mucosal lining.
2. Local Microbiota Disruption
The pouches of diverticulosis may harbor altered gut flora. This bacterial imbalance can cause chronic immune activation in the surrounding mucosa.
3. Mechanical Stress or Trauma
Straining, constipation, or pressure from the diverticula may damage the local tissue and cause a low-grade chronic injury, leading to inflammation.
4. Immune Dysregulation
Aging immune systems may not regulate inflammatory responses well, allowing chronic segmental inflammation to persist without clear infection.
Symptoms: Signs You Might Be Dealing with Segmental Colitis, Not Just Diverticulosis
Patients with segmental colitis often report symptoms that do not fully align with diverticulitis or IBD. Key red flags include:
- Intermittent or chronic rectal bleeding
- Mucus in the stool
- Loose or semi-formed stools
- Mild, left-lower quadrant abdominal discomfort
- No fever, chills, or severe pain
These symptoms can persist for weeks or even months, often without acute episodes that would otherwise prompt emergency care.
Why It’s Frequently Misdiagnosed
Segmental colitis in diverticulosis is commonly mistaken for:
- Hemorrhoids, due to rectal bleeding
- Mild ulcerative colitis, due to localized inflammation
- IBS, due to chronic loose stools
- Diverticular bleeding, which is usually brisk and painless — unlike the slower, intermittent bleeding seen in SCAD
Adding to the confusion, many patients have normal lab tests (e.g., white blood cell count, CRP, ESR), so inflammation goes undetected unless a colonoscopy is done.
Diagnosis: How Segmental Colitis is Confirmed
A diagnosis of segmental colitis in diverticulosis requires a careful combination of clinical observation, colonoscopy, and histology.
1. Colonoscopy Findings
- Inflammation is localized to areas with diverticulosis, especially the sigmoid colon
- Appearance may include mucosal erythema, friability, or shallow ulcerations
- Rectum and proximal colon typically appear normal
2. Biopsy (Histopathology)
Tissue samples show:
- Chronic mucosal inflammation
- No evidence of Crohn’s disease (no granulomas)
- No diffuse inflammation (as in ulcerative colitis)
3. CT Imaging (Optional)
CT scans are usually not diagnostic for SCAD but may help rule out diverticulitis, which shows diverticular wall thickening and fat stranding.
Treatment: Managing Segmental Colitis Without Overtreating
Fortunately, most cases of segmental colitis in diverticulosis respond well to conservative treatment, and aggressive immunosuppressants are rarely needed.
1. 5-Aminosalicylic Acid (5-ASA) Therapy
- Oral or rectal mesalamine is the mainstay treatment
- Helps reduce local inflammation with minimal side effects
2. Short Course Antibiotics
- Metronidazole or ciprofloxacin may be used if bacterial overgrowth is suspected
- Especially helpful when SCAD overlaps with low-grade infection
3. Fiber and Bowel Management
- High-fiber diet can reduce pressure and improve stool consistency
- Prevents further stress on inflamed mucosa
4. Avoid Unnecessary Steroids
- SCAD rarely requires systemic corticosteroids
- Overuse can worsen symptoms or delay accurate diagnosis
Prognosis: What to Expect Long-Term
Most patients with segmental colitis in diverticulosis:
- Recover completely with medical therapy and bowel care
- Experience intermittent relapses, often mild
- Do not progress to inflammatory bowel disease
- Have no increased colon cancer risk from SCAD itself
Long-term follow-up is usually not required unless symptoms recur or escalate.
When to Suspect SCAD Instead of IBS or Hemorrhoids
If you’re over 50 and have:
- Known diverticulosis
- Recurrent or chronic rectal bleeding
- Loose stools without pain or fever
- Mucus in stool
- Negative IBD tests or normal colon beyond the sigmoid
… then segmental colitis should be considered, and colonoscopy with biopsy should be arranged.
Conclusion: Don’t Let Segmental Colitis Hide Behind Diverticulosis
Chronic rectal bleeding and loose stools in patients with diverticulosis aren’t always benign or “just IBS.” Segmental colitis is an under-recognized yet treatable condition that requires a specific approach — not guesswork.
By staying alert to the signs, insisting on proper diagnostic workup, and avoiding unnecessary over-treatment, both patients and clinicians can uncover and manage this silent source of colon inflammation before it leads to unnecessary worry or incorrect labeling as IBD.
