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)