Diverticular Disease

Diverticula are protrusions of the bowel wall occurring most commonly in the colon. The condition of having diverticula (called diverticulosis) is mostly asymptomatic. These diverticula can become symptomatic, however, when associated with diseases. Diverticulitis is the inflammation of diverticula, often presenting with lower abdominal pain and changes in bowel habits. The condition may be further complicated by abscess, perforation, fistula, and bowel obstruction. Management consists of antibiotics, fluid resuscitation, and bowel rest. Surgery is required for complications, failure of medical management, and recurrent disease. In most cases of diverticular bleeding, spontaneous cessation occurs. Invasive intervention will be needed for persistent or recurrent bleeding.

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Diverticulosis is the presence of multiple diverticula, which are sac-like protrusions of the bowel wall.
Diverticular disease is diverticulosis with associated symptoms.

Presentation of diverticular diseases

  • Diverticulitis (inflammation of the diverticulum/diverticula)
  • Complications: obstruction, fistula, perforation, abscess
  • Diverticular bleeding
  • Segmental colitis associated with diverticula (SCAD)
  • Symptomatic uncomplicated diverticular disease (SUDD)
Diverticula, sigmoid colon

Diverticulosis: image showing the large bowel (sigmoid colon) with multiple diverticula

Image: “Large bowel (sigmoid colon)” by Haymanj. License: Public Domain


  • Colonic type is the most common diverticulosis.
  • Prevalence:
    • Age-dependent:
      • < 20% at the age of 40
      • 60% by the age of 60
    • Higher in countries with a Western diet
  • Distribution varies by race/ethnic origin:
    • Overall, left-sided diverticulosis is most common in the United States.
    • African Americans: higher percentage of right-sided disease than in whites
    • Asians: Right colon is predominantly affected.
  • About 4% of those with diverticulosis develop diverticulitis, with a 20% 5-year recurrence rate.

Risk factors

  • Diet:
    • Low fiber
    • High fat
    • Red meat
    • Seeds and nuts are not risk factors.
  • Obesity
  • Physical inactivity
  • Increased risk of complicated diverticular disease:
    • Genetic disorders
      • Marfan syndrome
      • Ehlers-Danlos syndrome
      • Scleroderma
    • Smoking



  • Intraluminal pressure causes herniation of the mucosa and submucosa through weak areas in the colon wall.
  • Diverticula occur in these weak spots (where vasa recta or nutrient vessels penetrate the muscular layer).
  • Colonic diverticula are considered “false” diverticula or pseudodiverticula (does not contain all layers of the bowel wall) as they do not contain a muscular layer.
  • Diverticulosis in most patients involves the sigmoid (most common site) and the descending colon.
Colonic diverticula

Pathophysiology of the development of diverticulosis from a healthy colon.
Colonic diverticula form when mucosa and submucosa herniate through the envelope that surrounds the intramural vasa recta (nutrient vessels).

Image by Lecturio.


  • Increased intraluminal pressure and/or thickened food particles contribute to the erosion of the diverticular wall.
  • In a minority of diverticulosis cases, inflammation, focal ischemia and/or necrosis (diverticulitis) follow, with bacterial translocation and possible micro-/macroperforation.

Types of diverticulitis

Diverticulitis is often mild, with mesentery and pericolic fat walling off a small perforation. More extensive disease can lead to complications.

  • Simple or uncomplicated diverticulitis: 
    • No associated complication(s) 
    • 85% of diverticulitis cases
  • Complicated diverticulitis (can be acute or chronic): 
    • Diverticular abscess (most common)
    • Obstruction
    • Free perforation
    • Fistula (frequently with the bladder)
    • Diverticular stricture
Acute diverticulitis

Pathophysiology of diverticulitis.
Acute diverticulitis is inflammation localized to a diverticulum and the surrounding mucosa. The process may include microperforation or bacterial translocation, or focal ischemia.

Image by Lecturio.

Clinical Presentation


  • Asymptomatic
  • In majority of cases, detected incidentally on colonoscopy or barium enema


  • Symptoms:
    • Abdominal pain
      • Constant
      • Left lower quadrant (LLQ) or suprapubic most common
      • Right lower quadrant if right-sided
    • Urinary urgency (from bladder irritation)
    • Constipation or diarrhea
    • Fever, nausea/vomiting
  • Signs:
    • Tender LLQ and suprapubic areas (right LQ if with right-sided diverticulitis)
    • Local peritoneal irritation (rebound tenderness)
    • Diffuse guarding and peritonitis suggest perforation.
    • Fever and tachycardia usually suggest complicated disease.



  • Patient is asymptomatic: no work-up 
  • Discovered incidentally after tests are done
  • Diverticular disease: Tests depend on presenting symptoms and suspected disease.
Diverticulum of the colon

Diverticulosis: colonoscopy showing diverticula in the colon

Image: “Diverticulum” by MAC 06. License: CC BY 4.0


  • History:
    • LLQ or suprapubic pain
    • Recurrent similar episodes of pain
  • Laboratory studies:
    • Elevated WBC count (with left shift)
    • Elevated C-reactive protein
  • Computed tomography (CT) scan:
    • Test of choice 
    • Will show:
      • Diverticula
      • Colonic wall thickening (> 4 mm)
      • Pericolonic fat stranding 
      • Microperforations (small gas bubbles next to the colon wall)
    • If complications are present, findings include: 
      • Abscess: fluid collection(s) with necrotic debris or air-fluid levels
      • Fistula: air collection noted within other organs
      • Obstruction: dilated bowel loops
      • Perforation: free air noted
  • Ultrasound:
    • Can show inflammation, bowel wall thickening, diverticula, abscess
    • Operator-dependent and requires experience
    • Rarely used in practice
  • Magnetic resonance imaging (MRI):
    • Similar findings to CT scan
    • Can be used when CT is contraindicated
  • Colonoscopy:
    • Contraindicated during an acute episode of diverticulitis due to increased risk of perforation
    • Recommended 6–8 weeks after resolution of the acute episode:
      • To establish the extent of the disease 
      • To rule out other diagnoses (malignancy: found in 1.3% of simple diverticulitis and in 8% of complicated disease)


Hinchey classification of severity of acute diverticulitis

  • Based on radiographic features
  • Helps direct surgical management of diverticulitis complications
Hinchey 1aPhlegmon (localized)
Hinchey 1bPericolonic/mesenteric abscess
Hinchey 2Pelvic abscess
Hinchey 3Generalized purulent peritonitis
Hinchey 4Generalized feculent peritonitis

Medical management

  • Outpatient (generally for Hinchey 1a)
    • 7–10 day course of oral antibiotics
      • Fluoroquinolones + metronidazole
      • Amoxicillin-clavulanate
      • Trimethoprim-sulfamethoxazole + metronidazole
    • Diet modification (optional): 2–3 days of clear-liquid diet
    • Reassess in 2–3 days.
  • Inpatient
    • Criteria for admission:
      • Complicated diverticulitis
      • Microperforation on CT scan (Hinchey 1b)
      • Sepsis
      • Fever > 39°C (102.5°F)
      • Significant leukocytosis
      • Age > 70
      • Immunosuppression
      • Significant comorbidities
      • Intolerance of oral intake
      • Failure of outpatient treatment 
    • Intravenous antibiotics: broad-spectrum with enteric coverage
    • Bowel rest/clear-liquid diet
    • Pain management
    • Repeat CT scan in 2–3 days if no improvement to evaluate for complications.
  • Recovery (about 6–8 weeks): Perform colonoscopy to rule out colon cancer.



  • Immediate:
    • Free perforation/peritonitis (Hinchey 3 and 4)
    • Worsening clinical course despite medical management
  • Delayed/elective (6–8 weeks after an acute attack):
    • Recurrent attacks of diverticulitis (2 or more)
    • After an initial attack for high-risk patients:
      • Diabetes
      • Immunosuppression
      • Renal failure
      • Collagen vascular disorders (e.g., lupus)
    • Complicated diverticulitis initially managed with medical therapy


  • Elective/delayed:
    • Segmental colon resection with primary anastomosis
    • Usually after a colonoscopy to rule out other diseases (e.g., cancer)
  • Emergent/same admission:
    • Primary anastomosis is at risk of leaking in the setting of inflammation/infection.
    • Diversion of fecal stream from the anastomosis is needed until healed:
      • Hartmann’s procedure (resection of involved colon segment with end colostomy): gold standard
      • Resection of involved segment with primary anastomosis and diverting loop ileostomy: alternative
      • Reversal of colostomy/ileostomy can be performed in 3–6 months.

Complications of Diverticulitis

Diverticular abscess (Hinchey 2)

  • Walled-off pus collection that forms adjacent to a ruptured diverticulum
  • 17% of hospitalized patients with acute diverticulitis
  • Management:
    • Intravenous antibiotics (1st-line treatment)
    • Radiologically guided percutaneous drainage: for abscess > 4 cm (if accessible)
    • Surgery if patient does not improve with antibiotics/drainage
Diverticulitis-related abscess

Imaging illustrating a sigmoid diverticulitis-related abscess: CT scan showing peri-colonic fluid collection with air-fluid level (green arrow) consistent with an abscess

Image: “Sigmoid diverticulitis” by Department of Surgery, Macerata Hospital, Macerata, Italy. License: CC BY 4.0


  • Can develop acutely with severe colon inflammation
  • Usually resolves when inflammation subsides
  • A stricture may develop after an acute phase (scarring from inflammation).
  • Diverticular stricture:
    • Difficult to differentiate from cancer 
    • Usually requires surgery


  • Free colonic perforation with uncontained leakage in the peritoneal cavity
  • Hinchey grade 3 and 4
  • Patients usually present with peritonitis, fever, and tachycardia.
  • Requires emergent surgery (Hartmann’s procedure)


  • Fistulas can develop as inflammation in the colon wall erodes into the adjacent organs: 
    • Colovesical (to bladder; presents with pneumaturia/ fecaluria)
    • Colovaginal/colouterine (foul-smelling/feculent vaginal discharge)
    • Coloenteric (to small bowel)
    • Colocutaneous (to the skin)
  • Can be initially managed with antibiotics in a stable patient
  • Rarely heal on their own
  • Eventually require surgical resection of the fistulizing colon segment

Other Presentations of Diverticular Disease

Diverticular bleeding

  • Most common source of lower gastrointestinal (GI) bleeding in adults
  • Vasa recta (in the diverticulum), covered by mucosal layer only, are exposed to continuous injury from luminal contents.
  • Vessel walls weaken from intimal and medial changes, predisposing to rupture and bleeding.
  • 50%–90% occur on the right colon.
  • Manifestations:
    • Usually painless hematochezia
    • Sometimes associated with cramping and bloating
    • Blood from the left colon is bright red; from the right colon, blood is maroon/brown.
    • Spontaneously stops in 75% of patients but with increased risk of rebleeding
  • Diagnosis and management of lower GI bleeding:
    • Workup commences once the patient is stable and resuscitation (for blood loss) is complete.
    • Colonoscopy: test of choice as it is both diagnostic and therapeutic
    • Imaging:
      • Nuclear scintigraphy (tagged red blood cell scan): detects bleeding with rate of 0.1–0.5 mL/min
      • CT angiography:
        • Detects bleeding with rate of 0.3–0.5 mL/min
        • Requires intravenous contrast and has radiation exposure
      • Angiography: 
        • Requires active bleeding loss of 0.5–1 mL/min
        • Therapeutic intervention with vasoconstrictors/embolization can be given (carries complication risks).
    • Surgery if bleeding cannot be controlled
Diverticular hemorrhage

Illustration of diverticular hemorrhage:
Arterial bleeding can complicate diverticulosis, with vascular disease or structural weakness as likely contributing factors. The condtion is the most common source of lower gastrointestinal bleeding.

Image by Lecturio.

Segmental colitis associated with diverticulosis

  • Inflammation of the interdiverticular mucosa (not diverticula themselves)
  • < 2% of cases with diverticulosis
  • Pathogenesis is not exactly understood, but may be related to:
    • Chronic mucosal inflammation from diverticular herniation
    • Fecal stasis with resultant change in bacterial flora
    • Ischemia from changes to mucosal microcirculation
  • Manifestations:
    • Lower or LLQ abdominal pain
    • Chronic diarrhea and occasional hematochezia
  • Diagnosis:
    • Discovered incidentally on work-up of diarrhea, abdominal pain, and hematochezia
    • CT scan: colonic wall thickening in segment with diverticulosis
    • Colonoscopy: interdiverticular inflammation often in the sigmoid colon, sparing the rectum
  • Management:
    • Antibiotics: ciprofloxacin, metronidazole
    • Other options: mesalamine, course of prednisone

Symptomatic uncomplicated diverticular disease

  • Also known as “smoldering” diverticulitis
  • Colonic wall thickening without obvious inflammation
  • Suspected causes:
    • Abnormal colonic motility
    • Visceral hypersensitivity
  • Manifestations:
    • Abdominal pain without other signs of acute diverticulitis
    • Constipation
  • Diagnosis:
    • Rule out other GI functional disorders (e.g., irritable bowel syndrome (IBS))
    •  Clinical findings: 
      • Pain in SUDD: more sustained (often > 24 hrs)
      • Pain not relieved by bowel movement, unlike in IBS
      • Tenderness located in the left iliac fossa
    • CT scan and colonoscopy:
      • Performed depending on symptoms, risk of cancer, and clinical status
      • Absence of diverticula excludes SUDD.
  • Management: high-fiber diet; rifaximin has been tried with success

Differential Diagnosis

  • Colorectal cancer (CRC): a colonic neoplasm that often presents with rectal bleeding and colonic obstruction. Colorectal cancer sometimes can be associated with inflammation; can perforate and mimic complicated diverticulitis. Diagnosis is by colonoscopy with biopsy in a stable patient. In an emergent situation, the diagnosis is sometimes made during surgery.
  • Inflammatory bowel disease (IBD): a family of autoimmune diseases that includes Crohn’s disease and ulcerative colitis. Acute presentation can be similar to diverticulitis (lower abdominal pain, diarrhea (sometimes bloody), and fever). Diagnosis is established by detailed history and colonoscopy with biopsies.
  • Appendicitis: inflammation of the appendix. Main symptom is right lower quadrant pain. May be impossible to clinically distinguish right-sided diverticulitis from acute appendicitis as the symptoms are very similar. Diagnosis is established by CT scan or sometimes during surgery.
  • Pelvic inflammatory disease: sexually transmitted infection of the internal reproductive organs in women. Presents with lower abdominal/pelvic pain, local peritonitis, and fever. Diagnosis is established by history, gynecologic exam, and pelvic ultrasound or CT scan.


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