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Diverticulitis

Clinical Subject Page

Diverticulitis

Diverticulitis is inflammation and/or infection of one or more colonic diverticula, most commonly affecting the sigmoid colon. It typically presents with left lower-quadrant abdominal pain, fever, and leukocytosis, and may be uncomplicated or complicated by abscess, perforation, fistula, or obstruction

Also called

Sigmoid Diverticulitis (most common location)

ICD-10

K57.9

Specialty

Gastroenterology

Onset

Acute

Reviewed

July 2026

On This Page

Overview

Diverticulitis develops when a colonic diverticulum becomes inflamed, usually due to microperforation. Most cases occur in the sigmoid colon. Patients commonly present with left lower-quadrant abdominal pain, fever, nausea, and altered bowel habits. Diagnosis is primarily made with CT abdomen and pelvis with intravenous contrast, which also identifies complications. Management depends on disease severity and ranges from outpatient treatment for uncomplicated cases to hospitalization, antibiotics, drainage, or surgery for complicated disease.

Etiology & Risk Factors

Etiology

Diverticulitis occurs when a diverticulum becomes obstructed and undergoes inflammation with microperforation, leading to localized infection.

Risk Factors

  • Diverticulosis
  • Increasing age
  • Low-fiber diet
  • Obesity
  • Smoking
  • Physical inactivity
  • Chronic constipation
  • NSAID use
  • Corticosteroid use
  • Opioid use
  • Immunosuppression
  • Family history

Pathophysiology

Diverticulosis → obstruction of the diverticular neck by fecal material → increased intraluminal pressure → bacterial overgrowth and inflammation → microperforation → localized pericolic inflammation → uncomplicated diverticulitis or progression to abscess, fistula, perforation, obstruction, or generalized peritonitis.

Clinical Presentation

Symptoms

  • Left lower-quadrant abdominal pain

  • Fever

  • Nausea

  • Vomiting

  • Constipation

  • Diarrhea

  • Abdominal bloating

  • Dysuria or urinary frequency (adjacent bladder irritation)

Signs

    • Left lower-quadrant tenderness

    • Localized guarding

    • Fever

    • Tachycardia

    • Palpable abdominal mass (abscess)

    • Generalized peritonitis (perforation)

History Taking

Ask about:

  • Location and onset of abdominal pain
  • Previous episodes of diverticulitis
  • Fever or chills
  • Nausea or vomiting
  • Constipation or diarrhea
  • Rectal bleeding
  • Urinary symptoms
  • Recent colonoscopy
  • NSAID or steroid use
  • Immunosuppression

Physical Examination

General Examination

Look for:

  • Fever

  • Tachycardia

  • Signs of dehydration

  • Features of sepsis

Abdominal Examination

Assess for:

  • Left lower-quadrant tenderness

  • Guarding

  • Rebound tenderness

  • Palpable mass

  • Abdominal distension

  • Bowel sounds

Rectal Examination

Assess for:

  • Rectal tenderness

  • Blood in stool

  • Alternative anorectal pathology

Investigations

Laboratory Tests

  • Complete blood count

  • C-reactive protein

  • ESR

  • Renal function and electrolytes

  • Liver function tests

  • Urinalysis

  • Pregnancy test in women of childbearing age

  • Blood cultures (if septic)

Imaging

CT Abdomen and Pelvis with IV Contrast (Preferred)

Identifies:

  • Inflamed diverticula

  • Colonic wall thickening

  • Pericolic fat stranding

  • Abscess

  • Perforation

  • Fistula

  • Obstruction

Ultrasound

May be used when CT is unavailable or during pregnancy but is less sensitive.

MRI

May be considered during pregnancy or when radiation should be avoided.

Colonoscopy

Not performed during the acute episode due to the risk of perforation.

It is recommended 6–8 weeks after recovery to exclude colorectal cancer and assess the colon, particularly after a first episode of complicated diverticulitis.

Diagnosis

Diagnosis is based on:

  • Clinical presentation
  • Elevated inflammatory markers
  • CT findings
  • Classification into uncomplicated or complicated diverticulitis
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Management

  • Uncomplicated Diverticulitis

    • Outpatient management for stable patients

    • Oral fluids and gradual diet advancement

    • Analgesia

    • Selective use of oral antibiotics (not required for all immunocompetent patients with mild uncomplicated disease)

    • Clinical follow-up

    Complicated Diverticulitis

    Hospital admission with:

    • Intravenous fluids

    • Intravenous antibiotics

    • Bowel rest when appropriate

    • Pain control

    • Percutaneous drainage for large abscesses (usually >3–5 cm)

    Surgery

    Indications include:

    • Generalized peritonitis

    • Free perforation

    • Failure of conservative treatment

    • Large or persistent abscess

    • Fistula formation

    • Bowel obstruction

    • Recurrent complicated disease in selected patients

    Common procedures:

    • Sigmoid colectomy

    • Hartmann procedure

    • Primary resection with anastomosis (selected stable patients)

Complications

  • Pericolic abscess
  • Colonic perforation
  • Generalized peritonitis
  • Colovesical fistula
  • Colovaginal fistula
  • Bowel obstruction
  • Sepsis
  • Recurrent diverticulitis

Prognosis

  • Most patients with uncomplicated diverticulitis recover completely with conservative treatment. Complicated disease has a higher risk of recurrence, surgery, and morbidity. Early diagnosis and appropriate management significantly improve outcomes.

Key Points / Clinical Pearls

  • Diverticulitis is inflammation of a colonic diverticulum, usually in the sigmoid colon.
  • Left lower-quadrant pain is the most common presenting symptom.
  • CT abdomen and pelvis with IV contrast is the preferred diagnostic test.
  • Classify disease as uncomplicated or complicated.
  • Mild uncomplicated diverticulitis can often be managed as an outpatient.
  • Antibiotics are selective for uncomplicated disease but mandatory for complicated disease.
  • Abscesses may require percutaneous drainage.
  • Surgery is indicated for perforation, generalized peritonitis, fistula, obstruction, or failed conservative treatment.
  • Colonoscopy should be performed after recovery, not during the acute episode.