Diverticular Disease
A structural consequence of high intraluminal pressure forcing mucosa out through weak points in the colonic wall, so a low-fibre Western diet, the sigmoid colon's narrow calibre, and the complications of diverticulitis all follow from one mechanical principle.
In a nutshell
Low-fibre stool raises segmental colonic pressure, forcing mucosa out through weak points where vasa recta perforate the wall, mostly in the sigmoid colon. Obstruction of a diverticulum causes diverticulitis, and every complication (abscess, perforation, fistula, bleeding) is that same inflammatory process extending further.
Classic presentation
An older adult with constant left iliac fossa pain, fever and localised tenderness, sometimes with a palpable mass, effectively left-sided appendicitis.
Key points
- Diverticula form at the point of highest pressure (sigmoid colon) and structural weakness (where vasa recta perforate the muscularis).
- Diverticulosis is asymptomatic; diverticulitis is obstruction and inflammation of a diverticulum, giving left iliac fossa pain and fever.
- Complications share one mechanism extending further: contained inflammation gives an abscess, uncontained gives peritonitis, erosion into bladder gives a colovesical fistula with pneumaturia, and erosion of a vessel gives painless brisk PR bleeding.
- CT abdomen/pelvis with contrast is first-line in suspected acute diverticulitis and stages complications.
- Colonoscopy is deferred until inflammation has settled, both to avoid perforation risk and to exclude an underlying cancer.
First-line investigation
CT abdomen and pelvis with contrast in suspected acute diverticulitis.
First-line management
High-fibre diet for uncomplicated diverticulosis; conservative management (analgesia, fluids, selective antibiotics) for uncomplicated diverticulitis, escalating to drainage or surgery for complications.
Exam traps
- Colonoscopy is contraindicated during acute diverticulitis because of perforation risk: it is performed later to exclude malignancy, not acutely.
- Diverticular bleeding is classically painless and brisk, unlike the pain-predominant picture of diverticulitis; do not assume bleeding means active inflammation.
- Left iliac fossa pain with fever in an older adult is diverticulitis until proven otherwise, but red-flag features (peritonism, shock) mean urgent imaging, not empirical community treatment.
- Pneumaturia is a fistula symptom, not a urinary tract infection: think colovesical fistula from diverticular disease in a patient with recurrent UTIs and gas in the urine.
Educational content pending clinical review. Not medical advice.