Diverticulitis
Definitions
🔹 Diverticulosis
- Presence of sac-like mucosal outpouchings (diverticula) through the muscular layer of the colon.
- Often asymptomatic and found incidentally on colonoscopy or imaging.
- Prevalence:
- ~10% of individuals >45 years
- ~65% of individuals >70 years
🔹Diverticular Disease
- Encompasses the entire clinical spectrum:
- Asymptomatic diverticulosis
- Symptomatic uncomplicated diverticular disease (SUDD)
- Acute diverticulitis (complicated or uncomplicated)
- Chronic complications (fistula, strictures, bleeding)
🔹 Acute Diverticulitis
- Inflammation and micro- or macro-perforation of a diverticulum.
- Associated with bacterial overgrowth, mucosal injury, and transmural inflammation.
Epidemiology
🔹 Prevalence
- ~60% of individuals >60 years have diverticulosis.
- Diverticulitis occurs in ~10–25% of those with diverticulosis.
🔹 Demographics
- More common in:
- Males <50 years
- Females 50–70 years
- Mean age of hospital admission ≈ 63 years
- Sigmoid colon: common site in Western populations
- Right colon: more commonly involved in Asian populations
Risk Factors
🔹 Lifestyle and Diet
- Low dietary fibre intake (Western diet)
- High red meat and fat consumption
- Physical inactivity
- Obesity
- Smoking
🔹 Medications
- ↑ Risk: NSAIDs, corticosteroids, opioids
- ↓ Risk: Statins (possible protective effect)
🔹 Misconceptions
- No evidence that avoiding seeds, nuts, or popcorn reduces risk.
- Primary focus should be maintaining soft stool consistency via high-fibre intake.
🧬 Pathophysiology
🔹 Mechanism of Disease
- Elevated intraluminal pressure → mucosal herniation
- Erosion of diverticular neck from increased pressure or microtrauma
- Inflammation leads to:
- Microperforation → phlegmon or localised abscess
- Macroperforation → peritonitis
- Chronic inflammation → fibrosis, fistulae, or obstruction
🔹Complications
- Localised phlegmon or abscess
- Fistula formation (colovesical, colovaginal, enterocutaneous)
- Bowel obstruction (stricture or compression)
- Generalised peritonitis
- Rectal bleeding (from vasa recta disruption)
🩺 Clinical Presentation
🔹 Symptom Classification
Category | Definition |
---|---|
Uncomplicated | Localised inflammation without abscess, perforation, or systemic features |
Complicated | Associated with abscess, perforation, obstruction, fistula, or severe bleeding |
Non-severe | Mild-moderate local symptoms, haemodynamically stable, oral intake preserved |
Severe | Systemic illness, marked inflammation, or failed outpatient therapy |
🔹 History
🔸 Pain
- LLQ (Western populations)
- RLQ (Asian populations)
- Constant or intermittent, usually progressive
- Cramping pain ± bloating or flatulence
🔸 Gastrointestinal Symptoms
- Constipation (≈ 50%)
- Diarrhoea (≈ 35%)
- Nausea and vomiting (suggestive of ileus/obstruction)
- Anorexia
🔸 Urinary Symptoms
- Dysuria, frequency, urgency (suggests colovesical irritation)
🔸 Systemic Symptoms
- Fever, chills (suggest abscess or systemic inflammation)
- Malaise or myalgia in severe cases
🔹 Physical Examination
- LLQ tenderness on palpation (focal)
- Guarding, rebound, rigidity → peritonitis
- Palpable mass in 20% (suggests abscess)
- Hypoactive or normal bowel sounds
- Fever common; hypotension rare unless septic
🧪 Investigations
🔹 Laboratory Tests
- WBC: Elevated (>15 × 10⁹/L in severe cases)
- CRP/ESR: Elevated (CRP >150 mg/L suggests complicated disease)
- Urinalysis: May show sterile pyuria if bladder involved
- Blood cultures: If febrile or septic
🔹 Imaging
🔸 H5: CT Abdomen & Pelvis (with contrast)
- Gold standard
- Sensitivity: ~95% | Specificity: ~96%
- Assesses severity (Hinchey, WSES), identifies complications
- Typical findings:
- Colonic wall thickening
- Pericolic fat stranding
- Pericolic air/fluid
- Abscess, extraluminal gas or contrast (perforation)
🔸 Ultrasound
- Operator-dependent
- Sensitivity 84–94%, specificity 80–93%
- Less reliable than CT, useful when CT contraindicated
🔸 MRI
- Comparable to CT but more expensive and less available
- Preferred in pregnant or CT-contraindicated patients
🔸 Abdominal X-ray
- May show ileus, air-fluid levels
- Free air under diaphragm if perforated
🔹 Endoscopy
- Contraindicated in acute phase (risk of perforation)
- Colonoscopy at 6–8 weeks post-recovery to exclude:
- Colorectal cancer
- IBD
- Other causes of colitis
⚕️Management
Trigger to re-image | Typical red-flag findings |
---|---|
Systemic toxicity | T ≥ 38.5 °C, tachycardia, SIRS/sepsis picture |
Localised or generalised peritonism | Guarding, rebound, rigid abdomen |
Laboratory escalation | WBC > 15 × 10⁹/L or CRP > 150 mg/L after 48 h |
Obstructive or urinary signs | Vomiting, ileus, dysuria (suggests fistula) |
Failure of outpatient care | Persistent / worsening pain or inability to tolerate diet after 48–72 h |
Immunocompromise | Transplant, high-dose steroids, chemotherapy |
🔹 Initial Principles – Diagnostic Confirmation and Imaging Strategy
- All first presentations of suspected diverticulitis should undergo contrast-enhanced CT of the abdomen and pelvis:
- Confirms the diagnosis
- Classifies severity (e.g. Hinchey or WSES classification)
- Excludes mimics (e.g. colorectal cancer, IBD, ischaemic colitis, gynaecological causes)
- CT findings guide management regardless of whether the patient has known diverticular disease.
🔹 Role of Empirical Treatment Without Imaging
- Empirical outpatient treatment without imaging is acceptable only when:
- Patient has a previous CT-confirmed episode in the same colonic segment
- Current symptoms match the patient’s typical flare pattern
- The presentation is mild, afebrile, and the patient is haemodynamically stable
- Even in these cases, imaging is advised if:
- There are red flag features
- Symptoms do not improve or worsen within 48–72 hours
🔹 Decision Point – 48–72 Hour Clinical Reassessment
- Improving patients rarely need repeat imaging
- Deteriorating patients almost always require re-imaging and escalation of care
- Key indicators for imaging or admission:
- T ≥ 38.5 °C, tachycardia
- Worsening abdominal pain or peritonism
- WBC >15 × 10⁹/L, CRP >150 mg/L
- Vomiting or oral intolerance
- Immunosuppression
🔹 Criteria for Conservative Outpatient Management (WSES 2020, RACGP, AGA/ACP)
Outpatient treatment without immediate CT may be considered if all of the following apply:
- Previous CT-proven diverticulitis in same colonic location
- Current flare is consistent with previous episodes
- Afebrile or T < 38.5 °C
- Heart rate < 90 bpm, normal BP
- No signs of peritonism
- CRP <150 mg/L, WBC <15 × 10⁹/L
- Nausea is controlled; patient tolerates oral fluids
- Patient has prompt access to review and imaging if needed
Practice Pearl – MJA/RACGP – https://www.mja.com.au/system/files/issues/211_09/mja250276.pdf
🩹 Treatment by Severity
🔹 Uncomplicated (Non-Severe) Diverticulitis
Outpatient management is appropriate for immunocompetent, haemodynamically stable patients with:
- Mild localised symptoms
- No systemic toxicity
- Tolerance of oral intake
Management:
- ✅ Simple analgesia: Paracetamol ± NSAIDs (if no contraindications)
- ✅ Oral fluids, progressing to a soft or low-residue diet as symptoms improve
- 🚫 Antibiotics not routinely required (WSES 2020, RACGP) unless specific criteria are met
Antibiotic therapy is indicated if:
- Right-sided diverticulitis
- Immunocompromised state (e.g. diabetes, transplant, chemotherapy)
- No clinical improvement within 72 hours of conservative treatment
Oral antibiotic regimens:
- First-line:
→ Amoxicillin–clavulanate 875+125 mg PO every 12 hours for 5 days - Penicillin allergy:
→ Trimethoprim–sulfamethoxazole 160+800 mg PO every 12 hours
→ PLUS Metronidazole 400 mg PO every 12 hours
→ Duration: 5 days total
🔹 Severe or Complicated Diverticulitis
Criteria for inpatient care:
- Signs of systemic infection (fever ≥38.5 °C, tachycardia, hypotension)
- Inability to tolerate oral intake
- Local or generalised peritonism
- Failure of outpatient management (worsening after 48–72 h)
- Imaging-confirmed complications (abscess, fistula, obstruction, perforation)
Management:
- Hospital admission
- Nil by mouth (NPO) with IV fluid resuscitation
- IV analgesia
- Empirical IV antibiotics:
- Gentamicin IV once daily
- PLUS Metronidazole 500 mg IV every 12 hours
- PLUS Amoxicillin 2 g IV every 6 hours
OR Ampicillin 2 g IV every 6 hours
Escalation of care:
- CT-guided percutaneous drainage if abscess ≥3–5 cm
- Surgical consultation for:
- Free perforation and peritonitis
- Fistula formation
- Bowel obstruction
- Ongoing sepsis or failure of medical therapy
Complications
🔹 Acute Complications
- Abscess (confined or pelvic)
- Free perforation → purulent/faecal peritonitis
- Fistulae (colovesical, colovaginal)
- Large bowel obstruction
- Rectal bleeding (diverticular bleed)
- Sepsis or septic shock
🔹 Diverticular Bleeding
- Common cause of painless, large-volume lower GI bleeding
- Spontaneous cessation in 75%
- Diagnostic options:
- Colonoscopy
- RBC scintigraphy
- CT angiography
- Therapeutic options:
- Endoscopic haemostasis
- Angiographic embolisation
Long-Term Outcomes & Recurrence
🔹 Recurrent Disease
- Occurs in 25–50% of patients
- Recurrence doesn’t predict complications
- Repeat imaging if atypical or worsening course
🔹 Chronic Pain
- Seen in ~20%
- IBS overlap or low-grade persistent inflammation
- Consider GI referral if symptoms persist despite resolution of inflammation
🔹 Elective Colectomy
- Consider in:
- Recurrent complicated diverticulitis
- Fistula
- Persistent symptoms despite medical therapy
🔹 Mortality
Category | Mortality |
---|---|
Uncomplicated (outpatient treated) | ≈ 0% |
Complicated, requires surgery | ≈ 5% |
Perforation with peritonitis | Up to 20% |
🔍 Follow-up and Prevention
🔹Colonoscopy and Surveillance
- A colonoscopy is recommended 6–8 weeks after an episode of acute diverticulitis (if not done within prior year)
- Purpose:
- Confirm diverticular disease
- Exclude malignancy (especially in complicated cases)
- Exclude differential diagnoses (e.g. IBD, colitis)
- In patients with complicated diverticulitis, the risk of colorectal cancer is estimated to be ≈10%
🔹 Recurrence
- Recurrent diverticulitis occurs in ~25–50% of cases
- Most recurrences are mild and do not increase the risk of complications
- Consider surgical referral for:
- Persistent symptoms
- Recurrent complicated episodes
- Stricture, fistula, or obstruction
🔹 Lifestyle & Dietary Modifications
- Cease smoking
- Increase dietary fibre (≥25–30 g/day)
- Promotes soft stool and reduces colonic intraluminal pressure
- Maintain hydration
- Avoid unnecessary food restrictions:
- Despite historical advice, studies show no evidence that corn, seeds, or nuts increase diverticulitis risk
- The primary culprit is likely impacted faecal matter, not food particles
- AFP and RACGP suggest patients should not be advised to avoid seeds/nuts
References
- RACGP Clinical Guidelines: racgp.org.au
- WSES Guidelines 2020: wjes.biomedcentral.com
- MJA Review: mja.com.au
- AGA/ACP Clinical Practice Updates (US context)
- UpToDate, Therapeutic Guidelines (eTG)