Diverticulitis and Diverticulosis
Acquired colonic outpouchings; inflammation produces left lower quadrant pain and fever.
Also known as: diverticulitis, diverticulosis, diverticular disease, acute diverticulitis
Overview
Diverticulosis: presence of acquired sac-like protrusions (false diverticula — lacking the muscular layer) of the colonic wall. Diverticulitis: inflammation or infection of one or more diverticula, classified as uncomplicated or complicated (abscess, fistula, obstruction, perforation).
Epidemiology
Diverticulosis prevalence rises with age: ~5% at age 40, ~30% at 60, >65% by age 85. Sigmoid colon is the most common site in Western countries (95% of cases). Right-sided diverticulosis more common in Asia. ~4% of patients with diverticulosis develop diverticulitis.
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Risk factors
- Age — most important
- Low-fiber, high-red-meat Western diet
- Obesity
- Smoking
- NSAID use (increases risk of diverticular bleed and perforation)
- Sedentary lifestyle
- Genetic susceptibility
- Connective tissue disease (Ehlers-Danlos, Marfan — early onset)
Pathophysiology
Increased intraluminal pressure (low-fiber diet → smaller stool → segmental contraction with high pressures) drives mucosal/submucosal herniation through weak points in the muscularis where vasa recta penetrate (vasa recta erosion → diverticular bleed). Diverticulitis: micro-perforation of an obstructed diverticulum → pericolonic inflammation, potentially with abscess or free perforation.
Clinical presentation
Symptoms
- Diverticulosis: usually asymptomatic; incidental on colonoscopy or imaging
- Diverticular bleed: painless, brisk hematochezia (most common cause of LGIB)
- Diverticulitis: left lower quadrant pain (sigmoid), constant, often worsening over 1-3 days
- Fever, chills, anorexia
- Change in bowel habit (constipation or diarrhea)
- Nausea, vomiting (if obstruction)
- Urinary symptoms (pneumaturia, fecaluria, recurrent UTI — colovesical fistula)
Signs / physical exam
- LLQ tenderness ± palpable mass (phlegmon or abscess)
- Low-grade fever, tachycardia
- Localized peritoneal signs
- Diffuse peritonitis if free perforation (Hinchey III/IV)
- Rectal exam may reveal tender mass anteriorly (Douglas pouch abscess)
Classic findings
Older adult with LLQ pain, fever, and leukocytosis — 'left-sided appendicitis.'
Differential diagnosis
- Acute appendicitis (especially with redundant sigmoid in LLQ or cecal diverticulitis) — Periumbilical pain migrating to RLQ; right-sided diverticulitis in Asian patients mimics this
- Colorectal cancer — Older patient, weight loss, anemia, change in bowel habit; colonoscopy 6-8 wk after diverticulitis recovery
- Inflammatory bowel disease — Younger patient, chronic course, bloody diarrhea, extraintestinal features
- Ischemic colitis — Sudden bloody diarrhea, watershed areas, atherosclerotic risk factors
- Infectious colitis (C. diff, Yersinia, Shigella) — Stool studies; recent antibiotics or travel
- Urolithiasis — Colicky flank pain radiating to groin, hematuria; CT urolithiasis protocol
- Gynecologic: ovarian torsion, PID, ectopic pregnancy — Pelvic exam, pregnancy test, pelvic ultrasound in women
- Epiploic appendagitis — Localized LLQ pain, characteristic small fat-density CT lesion adjacent to colon; self-limited
Diagnostic workup
Diagnostic criteria
CT-confirmed pericolonic inflammation with diverticula. Modified Hinchey classification: Ia (pericolic phlegmon), Ib (pericolic abscess <4 cm), II (pelvic/intra-abdominal abscess), III (purulent peritonitis), IV (feculent peritonitis).
Labs
- CBC (leukocytosis with left shift)
- BMP, lactate (if severe)
- CRP — predicts severity
- Urinalysis (exclude UTI, identify fistula)
- Urine pregnancy test in women of childbearing age
- Blood cultures if septic
Imaging
- CT abdomen/pelvis with IV contrast — MODALITY OF CHOICE; identifies pericolic inflammation, bowel wall thickening, abscess, fistula, free air; classifies by Hinchey stage
- AVOID colonoscopy during acute diverticulitis (perforation risk); perform 6-8 weeks AFTER resolution to exclude malignancy when first episode or alarm features
- Ultrasound or MRI in pregnancy or young patients to limit radiation
Diagnostic algorithm
| Hinchey Stage | CT Finding | Management |
|---|---|---|
| Ia | Pericolic phlegmon, no abscess | Antibiotics ± observation; usually outpatient |
| Ib | Pericolic abscess <4 cm | IV antibiotics ± percutaneous drainage if ≥3-4 cm |
| II | Pelvic or intra-abdominal abscess | Percutaneous drainage + IV antibiotics |
| III | Purulent peritonitis | Emergent surgery (Hartmann or resection + anastomosis with diversion) |
| IV | Feculent peritonitis | Emergent surgery |
Treatment
First-line
- Uncomplicated diverticulitis (Hinchey Ia, mild Ib without significant abscess): often managed as outpatient; bowel rest as tolerated; antibiotics selective rather than universal per AGA 2015 (consider in elderly, immunocompromised, comorbidities, severe symptoms)
- Outpatient antibiotic regimens: amoxicillin-clavulanate, or ciprofloxacin/levofloxacin + metronidazole × 7-10 days
- Clear liquid diet advanced as tolerated
- Follow-up in 2-3 days
Inpatient — moderate diverticulitis
- Admit if unable to tolerate PO, significant comorbidities, immunocompromise, failed outpatient management, abscess, or peritoneal signs
- IV antibiotics: piperacillin-tazobactam, ceftriaxone + metronidazole, or ertapenem
- Bowel rest, IV fluids, analgesia (avoid NSAIDs)
- Transition to oral antibiotics with clinical improvement
Abscess (Hinchey Ib-II)
- Abscess <3-4 cm: IV antibiotics alone
- Abscess ≥3-4 cm: percutaneous (image-guided) drainage + IV antibiotics
- Surgery if failure of drainage or clinical deterioration
Perforation with peritonitis (Hinchey III/IV)
- Emergent surgery — Hartmann procedure (sigmoid resection with end colostomy) or primary anastomosis with diverting ileostomy
- Laparoscopic lavage controversial; not preferred over resection
- Broad-spectrum IV antibiotics
Recurrent or complicated disease
- Elective sigmoid resection — individualized; consider after recurrent episodes (no longer routine after 2nd episode), persistent symptoms, complicated disease (fistula, stricture), immunocompromise
- AGA 2020 recommends shared decision-making rather than number-of-episodes rule
Diverticular bleed
- Resuscitate; most stop spontaneously (75%)
- Colonoscopy with hemostasis (clip, epinephrine, thermal) for active bleeding source
- CT angiography or tagged RBC scan if hemodynamically stable but ongoing bleeding
- IR angiographic embolization for refractory or massive bleed
- Surgery for failed embolization and persistent hemodynamic instability
Complications
- Abscess (intra-abdominal, pelvic)
- Fistula — colovesical (most common, M:F due to uterus barrier), colovaginal, coloenteric, colocutaneous
- Stricture and partial obstruction
- Free perforation with peritonitis
- Diverticular hemorrhage — most common cause of brisk lower GI bleeding
- Recurrence (15-30% within 5 yr after first episode)
PANCE pearls
- AVOID colonoscopy during acute diverticulitis — perforation risk. Schedule 6-8 weeks after resolution to exclude underlying malignancy (especially first episode or complicated disease).
- Antibiotics are no longer routine for uncomplicated diverticulitis in healthy patients (AGA 2015) — observation with close follow-up is acceptable.
- Pneumaturia, fecaluria, or recurrent polymicrobial UTI in older adult = colovesical fistula until proven otherwise.
- Right-sided diverticulitis is more common in Asian populations and frequently misdiagnosed as appendicitis.
- Old teaching to avoid nuts, seeds, and popcorn has NO evidence supporting it (Strate, JAMA 2008).
- Elective surgery decision is individualized — not by episode count. Consider in young immunocompromised patients, persistent symptoms, complicated disease.
- Modified Hinchey classification (CT-based) guides therapy — abscess ≥4 cm needs percutaneous drainage; peritonitis needs OR.
- Smoldering/chronic diverticulitis (low-grade inflammation without abscess) may benefit from elective resection.
References
- AGA 2015 — Stollman N et al. AGA Institute Guideline on the Management of Acute Diverticulitis. Gastroenterology 2015;149:1944-1949
- ASCRS 2020 — Hall J et al. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Treatment of Left-Sided Colonic Diverticulitis. Dis Colon Rectum 2020;63:728-747
- Strate Nuts/Seeds — Strate LL et al. Nut, Corn, and Popcorn Consumption and the Incidence of Diverticular Disease. JAMA 2008;300:907-914
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