ConditionDigestive system
Intra-abdominal Abscess
An intra-abdominal abscess is a collection of pus inside the abdomen, walled off by inflamed tissue. It usually follows a burst appendix, diverticulitis, Crohn's disease, a bowel perforation or abdominal surgery. Symptoms include fever, abdominal pain and tenderness, and feeling generally unwell, often days after the original illness or operation. It is diagnosed with a CT scan and treated with antibiotics plus drainage, usually through a needle guided by imaging.
Also called: Abdominal abscess, peritoneal abscess, pelvic abscess, subphrenic abscess, abscess inside the abdomen
At a glance
- What it is
- A walled-off pocket of pus in the abdomen or pelvis.
- Common causes
- Ruptured appendicitis, diverticulitis, Crohn's disease, abdominal surgery, perforated ulcer, pancreatitis.
- Symptoms
- Fever, abdominal pain, tenderness, chills, loss of appetite, diarrhea or urinary symptoms.
- Diagnosis
- CT scan with contrast. Ultrasound in some cases.
- Treatment
- Antibiotics plus drainage, usually by a needle and catheter placed under CT or ultrasound guidance.
- Risk if untreated
- Sepsis, which can be life-threatening.
When to get help
Call 911 or go to the ER
- Fever with severe abdominal pain, a rigid belly, confusion, fast breathing, low blood pressure or a racing heart
- Sudden worsening abdominal pain after recent surgery, with vomiting and inability to pass stool or gas
See a doctor within a day or two
- Fever and abdominal pain in the days or weeks after abdominal surgery, appendicitis or diverticulitis
- Fever with lower abdominal or pelvic pain, diarrhea or painful urination
- Redness, swelling or pus from a surgical wound with fever
Book a routine appointment
- Ongoing low-grade fever, loss of appetite and tiredness after recovering from an abdominal infection
How an abdominal abscess forms
When bacteria leak from the bowel or an infected organ, the body tries to contain the infection. The omentum (a fatty apron in the abdomen), loops of bowel and inflamed tissue wall it off, and pus collects inside. Without this containment, infection would spread through the abdomen as generalized peritonitis.
Abscesses are named by location:
| Location | Common sources |
|---|---|
| Right lower abdomen or pelvis | Appendicitis |
| Left lower abdomen or pelvis | Diverticulitis |
| Under the diaphragm (subphrenic) | After upper abdominal surgery, perforated ulcer |
| Between bowel loops | Crohn's disease, surgery |
| Pelvis | Pelvic inflammatory disease, gynecologic or colorectal surgery |
| Pancreas region | Infected pancreatic necrosis after pancreatitis |
| Liver, spleen | Bloodstream spread, biliary infection |
Causes and risk factors
- ruptured appendix, the most common cause in children and young adults
- complicated diverticulitis
- Crohn's disease, which can cause fistulas and abscesses
- bowel perforation from ulcers, trauma or cancer
- anastomotic leak after bowel surgery
- infected collections after pancreatitis
- abdominal trauma
- weakened immunity, diabetes and steroid use increase risk
Symptoms
- fever and chills, often spiking
- abdominal pain, localized or diffuse
- tenderness or a mass felt in the abdomen
- loss of appetite, nausea and vomiting
- diarrhea, or urgency and rectal discomfort with a pelvic abscess
- painful or frequent urination if near the bladder
- shoulder tip pain or hiccups with an abscess under the diaphragm
- general malaise and fatigue
Symptoms may appear 5 to 10 days after surgery or the original illness, sometimes after initial improvement. Antibiotics can mask symptoms, delaying diagnosis.
Diagnosis
- CT scan with contrast is the main test. It shows a fluid collection with an enhancing rim, sometimes with gas, and its relationship to nearby organs.
- Ultrasound helps in children, pregnancy and for pelvic or liver abscesses.
- Blood tests: raised white cell count and CRP, blood cultures, kidney and liver function.
- Fluid sampling during drainage to culture the bacteria and guide antibiotics.
Treatment
Antibiotics
Broad-spectrum antibiotics covering bowel bacteria, including anaerobes, are started promptly and adjusted to culture results. With adequate drainage, a short course of about 4 days after source control is often sufficient for many patients, based on the STOP-IT trial, though complex cases need longer.
Drainage
- Percutaneous drainage: an interventional radiologist inserts a needle and thin catheter through the skin into the abscess using CT or ultrasound guidance. This is the first choice for most accessible abscesses. The drain stays in for days until output falls and a repeat scan shows resolution.
- Small abscesses (under about 3 cm) may be treated with antibiotics alone.
- Transrectal or transvaginal drainage for some deep pelvic abscesses.
Surgery
Surgery is needed when drainage is not possible or fails, for multiple or complex abscesses, or to treat the source, such as removing the appendix (sometimes weeks later) or a diseased segment of colon.
Complications
- sepsis and septic shock
- fistula formation between bowel and skin, bladder or vagina
- bowel obstruction
- recurrence
- spread to the bloodstream, liver or chest
Outlook
With drainage and antibiotics, most intra-abdominal abscesses resolve. Outcomes are worse in older adults, people with weakened immunity, and when diagnosis is delayed or sepsis develops.
Frequently asked questions
What causes an intra-abdominal abscess?
Most are caused by bacteria leaking from the bowel after a ruptured appendix, diverticulitis, Crohn's disease, a perforated ulcer or abdominal surgery. Infected collections after pancreatitis and abdominal injuries are other causes.
What are the symptoms of an abdominal abscess?
Common symptoms are fever, chills, abdominal pain and tenderness, loss of appetite, nausea and feeling generally unwell. Depending on location, there may be diarrhea, urinary symptoms or shoulder pain. Symptoms often appear days after surgery or an infection.
How is an abdominal abscess treated?
Treatment combines antibiotics with drainage. Most abscesses are drained by a radiologist using a needle and catheter guided by CT or ultrasound. Small ones may respond to antibiotics alone, and surgery is used when drainage is not possible or the source needs repair.
Can an abdominal abscess go away on its own?
Very small abscesses sometimes resolve with antibiotics alone. Larger abscesses usually need drainage, because antibiotics penetrate pus poorly. An untreated abscess can rupture or cause sepsis.
How long does it take to recover from an abdominal abscess?
Many people feel better within days of drainage and antibiotics. The drain usually stays in for several days to 2 weeks. Full recovery takes a few weeks, and longer if surgery was needed or the abscess was complex.
Sources
This guide was written from current patient and clinical guidance, including:
- Surgical Infection Society / IDSA: Guidelines for the Diagnosis and Management of Complicated Intra-abdominal Infection (2010, revised 2017)
- World Society of Emergency Surgery: 2017 Guidelines for Management of Intra-abdominal Infections
- MedlinePlus: Intra-abdominal abscess
- American College of Radiology: Image-guided percutaneous drainage
- Merck Manual: Intra-abdominal Abscesses