Colon Diverticulitis

Definition

• Sleisenger and Fordtran's Gastrointestinal and Liver Disease

Epidemiology

• Diverticulitis develops in approximately 4% of patients with known diverticulosis over an 11-year period (older estimates of 10-25% risk are now considered overestimates).
• Prevalence of diverticulitis hospitalizations in the USA peaked around 2008 and has since stabilized.
• The proportion of patients requiring surgery decreased from ~25% to ~15% between 2000 and 2010.
• In Western populations, ~95% of diverticula occur in the sigmoid/left colon. In Asian populations, right-sided diverticula predominate.
• Sleisenger and Fordtran's

Pathophysiology

1. Increased local bacterial flora
2. Diminished venous outflow and localized ischemia
3. Altered mucosal defense (defective CD2-induced apoptosis in lamina propria lymphocytes, upregulating local immunity - similar to IBD)
4. Possible CMV reactivation (found in >2/3 of affected bowel segments in diverticulitis)
5. Transmural bacterial extension -> microperforation

• Microperforation - contained by pericolic fat -> small pericolic abscess
• Larger perforation - extensive abscess, possible fistula or obstruction
• Free perforation -> bacterial or fecal peritonitis (incidence ~4/100,000/year)
• Sleisenger and Fordtran's

Hinchey Classification of Diverticular Perforation

• Sleisenger and Fordtran's

Clinical Features

• LLQ abdominal pain (constant or intermittent) - the hallmark
• Change in bowel habits (diarrhea or constipation)
• Low-grade fever
• Anorexia, nausea, vomiting
• "Sympathetic cystitis" - dysuria/urinary frequency from bladder irritation by inflamed sigmoid
• LLQ tenderness on exam; possible palpable mass; guarding/rebound
• Note: BRBPR is NOT seen in acute diverticulitis

• Diffuse tenderness with rebound/guarding -> perforation or abscess rupture
• Dysuria + fecaluria -> colovesical fistula
• Feculent vaginal discharge -> colovaginal fistula
• Palpable mass -> localized abscess
• Vomiting + distension -> obstruction
• High fever / sepsis

• Sleisenger and Fordtran's; Rosen's Emergency Medicine

Diagnosis

Imaging

• Colonic wall thickening
• Pericolic fat stranding
• Localized microperforation
• Abscess formation
• Free air or fluid (perforation)

Lab Work

• WBC elevated in most but normal WBC in up to 46% - does not exclude diagnosis
• Urinalysis when colovesical fistula suspected
• Sleisenger and Fordtran's; Rosen's Emergency Medicine; Bailey and Love's Surgery

Differential Diagnosis

Management

Uncomplicated Diverticulitis

• Liquid/low-residue diet, advance as tolerated
• Oral analgesics
• Selective antibiotics (if used): cover Gram-negative aerobes AND anaerobes (e.g., metronidazole + ciprofloxacin; or amoxicillin-clavulanate)
• No benefit of IV over oral antibiotics for uncomplicated disease

• Elderly or immunocompromised patients
• Multiple comorbidities
• Unable to tolerate oral intake
• Failure of outpatient therapy
• First episode with diagnostic uncertainty

Complicated Diverticulitis

• Stage I (<3-4 cm): may resolve with antibiotics alone + bowel rest
• Stage II (>3-4 cm or pelvic): CT-guided percutaneous drainage - success rate 74-80% for patient stabilization, allowing later single-stage resection in 3-4 weeks
• 20-25% require urgent surgery (multiloculated, inaccessible, or non-resolving abscess)

• Emergency surgery required
• Options: Hartmann's procedure (sigmoid resection + end colostomy) vs. primary anastomosis (with or without protective stoma)
• A recent 2025 meta-analysis on primary anastomosis in emergency left colon surgery supports safety of primary anastomosis without protective stoma in selected patients

• Develops in <5% of all diverticulitis cases but ~20% of surgical cases
• Colovesical fistula is the most common (men > women due to uterus acting as barrier)
• Treatment: elective surgical resection after bowel prep and preoperative cystoscopy/urologic evaluation

• Colonic obstruction from stricture or inflammatory mass
• Acute: IV fluids, bowel decompression, consider stenting vs. surgery
• Chronic stricture: elective resection

Elective Surgery - Indications

• Recovery from complicated diverticulitis (abscess/fistula/obstruction)
• Recurrent symptomatic disease significantly impairing quality of life
• Inability to exclude carcinoma

• Sleisenger and Fordtran's; Rosen's Emergency Medicine; Bailey and Love's Surgery

Post-Acute Surveillance

• Colonoscopy is not routinely required after each episode
• Follow standard colorectal cancer screening intervals
• High-fiber diet post-recovery (reduces recurrence and symptom burden)
• Physical activity reduces risk of developing diverticulitis (mechanism unclear)
• Previously advised avoidance of nuts/seeds/popcorn has been discredited - no evidence base

Recent Evidence (PubMed 2024-2026)

• A 2025 systematic review and meta-analysis (Kahana et al., Surgery) found no significant QoL advantage of elective surgery over non-operative management for colonic diverticulitis - supports conservative management as first-line for most recurrent cases.
• A 2026 systematic review (Sassun et al., Colorectal Dis) found low rates of recurrent diverticulitis after sigmoid resection, supporting surgery in high-recurrence-risk patients.
• Genetic determinants of diverticulosis are increasingly recognized, with connective tissue genes implicated - relevant to younger patients with early-onset disease.