Diverticulitis Abscess: Causes, symptoms, & Treatments (including surgical drainage).

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What is a diverticulitis abscess?

The diverticulum is a sac-like projection, often found in the sigmoid and left colon.

Diverticulitis abscess is different from diverticulitis. Abscess formation is a more severe complication of diverticulitis.

  • Acute diverticulitis refers to the acute inflammation of the sac-like diverticula of the colon. It leads to abdominal pain, fever, and bowel habit changes.
  • Diverticulitis abscess is a complication of acute diverticulitis. It o curs when a diverticulum becomes infected and filled with pus.

It is often difficult to differentiate between uncomplicated diverticulitis and diverticulitis abscess based on symptoms only.

The diverticulitis abscess is not limited to the colon, It can extend to the outside of your colon if perforation occurs (reference).

Common types of diverticulitis abscesses (reference).

  • Intramural abscess confined to the inflamed diverticulum (commonest).
  • An intra-abdominal abscess (around the colon, or anywhere inside the abdomen) due to perforation of the inflamed diverticulum.
  • Pelvic abscess.
  • Diffuse pus in the peritoneum (purulent peritonitis).
  • A distant abscess (due to the spread of infection through the blood): most commonly liver abscess is due to the spread of infection tough the portal vein carrying the blood from the intestines to the liver.

The below table is a simplified version of the stages of diverticulitis and diverticular abscess. It is



Stage 0Mild diverticulitis.
Stage1aExtension of inflammation to the tissues around the colon (but no abscess).
Stage 1bA small abscess (<5cm)
Stage IIAbscess inside the abdominal cavity, the pelvis, or distant to the site of diverticulitis.
Stage IIIPurulent (pus) inside the peritoneum.
Stage IVFeces inside the peritoneum.

The incidence of diverticulitis abscess.

Diverticulitis is a rare complication of diverticular disease affecting about 10-25% of patients with diverticulitis.

Diverticulitis abscess is even rarer. One study estimated that diverticulitis abscess occurs in about 17% of patients hospitalized with diverticulitis.

Causes of diverticulitis abscess:


The exact cause of diverticulitis is unknown. However, however, we think it is due to partial obstruction and micro-perforation of the diverticulum.

On the other hand, The diverticular abscess is often due to bacterial infection. The bacteria trapped inside the diverticula increase in number and form a pus-filled pocket.

The source of bacteria is often from the inside of the colon. The pus-filled pocket (diverticulitis abscess) is challenging to treat. A diverticular abscess often needs more vigorous antibiotic treatment and may require drainage.


Symptoms of the diverticular abscess.


The symptoms of diverticulitis abscess are not different from the symptoms and signs of uncomplicated diverticulitis. They may be more severe, or prolonged, But no single symptom can confirm the presence of an abscess.

The symptoms include:

  • Acute onset abdominal pain (often in the left lower abdomen, but it can be diffuse or elsewhere in the abdomen).
  • Changes in bowel habits (loose stool, constipation, or diarrhea).
  • Fever (High-grade fever is often more common with abscess formation than in diverticulitis).
  • Anorexia, nausea, and maybe vomiting.
  • Severe tenderness or rigidity.
  • A sense of mass (painful and tender) may indicate the presence of abscess due to diverticulitis.
  • Symptoms of intestinal obstruction may occur with large diverticulitis abscess (absolute constipation, distension, and persistent vomiting).
  • Sings of septic shock (in late severe cases): low blood pressure, dizziness, confusion, shortness of breath, fast heartbeats, and coma.

When to suspect diverticular abscess?

The problem with diverticular abscesses is that they may develop late in the course of diverticulitis. So, They can be missed by your doctor or even by abdominal imaging in the first few days.

Suspect the presence of abscess if (reference):

  • Fever is high grade or persistent for several days.
  • Pain is not improving after three days of antibiotic treatment.
  • Presence of localized tender mass (often in the left lower abdominal region).

The below table summarizes the main differences between uncomplicated diverticulitis and diverticular abscess.


Clinical symptoms

Uncomplicated diverticulitis

Diverticulitis abscess

Abdominal pain+++++++ or +++++
Localized tendernessrareCommon
A sense of tender massUnlikelySometimes felt as a mass if large.
Fever+ or ++++ up to ++++
Septic shock (low blood pressure)RareMore common.
Response to antibioticsGoodPoor, need strong intravenous antibiotics.


As we explained before, Diverticular abscesses are difficult to detect based on symptoms only due to:

  • The symptoms are almost identical to simple uncomplicated diverticulitis in small abscesses and early stages.
  • They may develop days after the onset of acute diverticulitis.

To diagnose diverticulitis, Your doctor will need some investigations such as:

  • Computed tomography scan (CT) Of the abdomen: The abscesses are seen as a small fluid collection inside the abdomen.
  • Abdominal ultrasound is a faster and cheaper alternative, but it is less accurate in the detection of small abscesses.
  • Magnetic resonance imaging (MRI).
  • Other investigations that may help include total leucocyte count (elevated), C-reactive protein level or CRP (elevated), and abdominal plain X-ray.

Treatment of diverticulitis abscess:

A. Initial Treatments (Intravenous antibiotics, fluids, and analgesics).

If you have an abscess with diverticulitis, you’ll need in-hospital admission and treatment.

  • Intravenous fluids such as Ringer’s lactate or normal saline.
  • Medications to reduce abdominal pain (such as acetaminophen or ketorolac).
  • Intravenous antibiotics.
  • Liquid diet or complete bowel rest (no eating at all) in severe cases.

B. Drainage.

The drainage (evacuation) of pus from the abscess can be done without surgery.

The drainage procedure for diverticulitis abscess is carried out by an interventional radiologist. The radiologist will insert a specialized long syringe through the abdominal wall guided by CT or ultrasound device. Then, he will aspirate the contents of the abscess with the syringe.

The diverticulitis abscess drainage color is often greyish, brownish, or reddish (bloody) in nature. The color is variable and depends on the size and the degree of liqification inside the abscess.

Drainage is indicated for:

  • Diverticular abscesses are larger than 4 Cm in diameter (when accessible).
  • Abscesses that don’t respond to intravenous antibiotics.

After the drainage is done, you will need at least 24 to 48 of hospital admission. During the admission, Your doctor will follow up on your condition and you will complete the course of antibiotics.

If you are getting better, your doctor will discharge you to complete treatment at home.

If the drainage fails, your doctor may decide to go for surgery.

C. Surgery for diverticulitis abscess.

Surgery for a diverticular abscess is indicated for patients who fail to respond to intravenous antibiotics or drainage. Resection of the area with the abscess and re-anastomosis of the colon is the main surgery procedure for diverticular abscess treatment.

Indications of surgery in diverticular abscess include:

  • Patients who fail to improve after three days of antibiotics treatment.
  • Failure or inability to perform percutaneous drainage.
  • Deterioration of the condition despite drainage and antibiotic therapy (increased pain, fever, and elevated white blood cell count).

After diverticulitis surgery, you will need to stay in the hospital for a few days depending on your condition. You will receive antibiotics, pain medications, and intravenous fluids to prevent complications after the surgery.