Continuing Education Activity

An intraabdominal abscess is a localized collection of pus within the peritoneal or retroperitoneal space, often resulting from infections, surgical complications, or trauma. If unrecognized or untreated, these abscesses can lead to significant morbidity and mortality. Diagnosis often requires a high index of suspicion and imaging studies like computed tomography scans, while treatment involves antibiotics, drainage, and, in some cases, surgical intervention. Factors such as comorbidities, delayed diagnosis, and antibiotic resistance can complicate outcomes, emphasizing the need for a systematic, interprofessional approach to care.

Clinicians participating in this course gain a comprehensive understanding of the pathophysiology, diagnosis, and management of intraabdominal abscesses. They learn to integrate evidence-based strategies into clinical practice, optimize antibiotic stewardship, and improve interprofessional communication and coordination. This course enhances clinician's ability to recognize complications, employ effective interventions, and improve patient-centered outcomes, ultimately contributing to reduced morbidity, mortality, and healthcare costs.

Objectives:

• Identify the clinical signs and symptoms of an abdominal abscess, such as fever, localized pain, and signs of systemic inflammation, to initiate timely evaluation.

• Assess intraabdominal abscess size, location, and complexity using various imaging modalities to guide treatment planning.

• Implement appropriate management strategies, including initiating antibiotics and drainage based on clinical condition and abscess location.

• Collaborate with interventional radiologists, surgeons, infectious disease specialists, and other members of the interprofessional team, fostering a multidisciplinary approach to abdominal abscesses that will improve patient outcomes.

Introduction

Intraabdominal abscesses represent a critical clinical condition characterized by the localized collection of cellular debris, enzymes, and microorganisms encapsulated within a pseudo capsule that forms part of the host's immune response to infection, inflammation, trauma, or malignancy. These abscesses can arise from various etiologies, including gastrointestinal perforation, postoperative complications, trauma, or infection spreading from adjacent organs such as the appendix, pancreas, or biliary system. Intraabdominal infections may precede abscess formation, originate from inflammatory or infectious infiltration of abdominal organs, or spread through direct contact, bloodstream, or lymphatics.

Intraabdominal abscesses are often polymicrobial, involving bacteria, fungi, and sometimes parasitic organisms, though aseptic collections also occur. An intraabdominal abscess can impact systemic functioning, delay recovery, cause additional complications, and should be considered with any adverse postoperative changes or slow progress.[1] The condition can remain localized or progress to peritonitis, signifying significant clinical dysfunction.[2] The pathophysiology of abscess formation includes the interplay of host immune defenses and the hypoxic, acidotic microenvironment within the abscess, which limits antibiotic efficacy and complicates treatment.[3] Additionally, abscesses are frequently walled off by omentum, mesentery, or other intraabdominal structures, further hindering therapeutic penetration.

Prompt diagnosis and management of intraabdominal abscesses are essential to prevent high morbidity and mortality. If left untreated, these abscesses can lead to systemic dysfunction, delayed recovery, and severe complications, including sepsis and multiorgan failure. Advances in imaging modalities and minimally invasive drainage techniques have improved the ability to diagnose and effectively treat this condition. However, optimal outcomes require a multidisciplinary approach considering abscess location, microbial etiology, patient comorbidities, and resistance patterns. Generally, perforation of the upper gastrointestinal tract is associated with less morbidity and mortality than leaks from a colonic perforation or injury; however, any condition giving rise to an abscess must be promptly diagnosed and treated to avoid high morbidity and mortality.[4][5][6]

This review provides a comprehensive overview of abdominal abscesses, addressing their pathophysiology, clinical manifestations, diagnostic strategies, and management options. Special attention is given to the role of interventional radiology, surgical approaches, antimicrobial therapy, and emerging trends and treatment challenges. By synthesizing current evidence to manage this complex and potentially life-threatening condition, this course aims to inform clinical practice and improve patient outcomes.

Etiology

The causes for an intraabdominal abscess can be broadly categorized into inflammatory, infectious, malignant, traumatic, and iatrogenic. This condition can arise de-novo in the abdominal compartment, derive from an intraabdominal structure, or be disseminated from extraabdominal sources. While there are case reports detailing an intraabdominal abscess from various sources, most intraabdominal abscesses contain colonic flora. Microbe speciation depends on geographical location and the affected person's overall health.[7]

Sources for an intraabdominal abscess include but are not limited to diverticulitis, perforated ulcer, appendicitis, gangrenous cholecystitis, bowel infarction, splenic infarct or infection, inflammatory bowel disease, trauma, anastomotic leak, and intraoperative contamination.[8] Systemic infectious agents can give rise to an abscess, including rare cases of echinococcosis or amebiasis, in adults and the pediatric population.[9][10][11] Periodontal disease is an important potential source for bacterial dissemination that may give rise to an abscess.[12] Foreign bodies such as peritoneal dialysis catheters or rare retained objects may also result in an intraabdominal abscess.[13][14] A splenic abscess as a consequence of endocarditis is rare but conveys significant clinical consequences.[15] Persons with Crohn disease may form spontaneous abscesses, and there are cases of familial adenomatous polyposis associated with desmoid tumors complicated by abscesses.[16][17][18] Dropped gallstones causing postoperative abscesses have been reported.[19] Rarely an appendicolith can lead to a postoperative abscess.[20] Uncommon causes include the case report of an inflammatory left lower quadrant abscess from a colonic mucosa-associated lymphoid tissue lymphoma in a man aged 68.[21] Further, an intraabdominal process may rarely create distant abscesses, as in the case of a diverticular sigmoid perforation localizing to an abscess in the left inguinal region.[22]

Colonic flora is commonly found within intraabdominal abscesses, and predominant organisms include Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter, Streptococci, Enterococci, Neisserium, and a spectrum of anaerobic bacteria including Bacteroides, Clostridium, and Chlamydia trachomatis.[23][24][25][26][27] Coliform bacteria often contribute to early stages and anaerobes to later sequelae of abscess formation.[28] Candida species have been reported in infections originating from the gastrointestinal tract, particularly in those taking precedent antibiotics with a history of recurrent infection or being immunocompromised.[29][30] Intraabdominal infections in hospital settings contain nosocomial pathogens, including Pseudomonas aeruginosa and other organisms prone to drug resistance.[31][32]

Postoperative abscess is a common occurrence. There is an estimation that approximately 70% of intraabdominal abscesses are postsurgical, with around 6% of patients undergoing colorectal surgery developing a postoperative abscess. Hepatic abscesses account for 13% of all intraabdominal abscesses. Most hepatic abscesses involve the right lobe, likely due to the larger size and greater blood supply.[33] Prediction models have been created to anticipate risk factors for postoperative complications.[34][35] Results from a study of individuals who underwent pancreaticoduodenectomy and had bile sampling performed intraoperatively after transection of the common bile duct found that of the 539 persons included, over 80% had a positive bile culture, and these patients had a higher incidence of intraabdominal abscess compared to those without bile contamination.[36] Results from another study found C-reactive protein (CRP) level on postoperative day 3 to be an independent predictor of abscess following distal pancreatectomy. Abscess following appendectomy was associated with elevated CRP and perforation as per the results from a study on 423 persons who underwent laparoscopic appendectomy.[37]

There are cases of sterile abscess collections. Transabdominal injections occasionally result in the formation of a sterile intraabdominal abscess.[38] Aseptic abscess syndrome is a rare but known complication in those with inflammatory bowel disease and occasionally may be the first indicator of the diagnosis. Cultures of the abscess are sterile. Most cases are initially misdiagnosed and treated with antibiotics to which the patient does not respond, but the collections respond well to immunosuppressive therapy. A report from the British Medical Journal documents the case of a 43-year-old woman with Crohn disease who developed multiple abscesses through her abdominal cavity and lungs and was ultimately diagnosed with aseptic abscess syndrome, successfully treated with high-dose intravenous steroids.[39] 

Intraabdominal sources of infection may migrate to extraabdominal locations. A case series of 3 colorectal perforations presenting as thigh abscesses has been published. These cases involved colectomies for malignancy, and the diagnosis of perforation was delayed with ensuing high morbidity and mortality.[40] A tubo ovarian abscess, which can occur in young, nonsexually active persons as well as adults, can have significant clinical consequences with high morbidity and can arise from a gynecologic but also a gastrointestinal source.[41][42] 

Epidemiology

Intraabdominal abscesses are relatively common and have significant implications for patient morbidity and mortality. Over 60% of these abscesses are hospital-acquired, highlighting the substantial contribution of healthcare-associated infections to their prevalence. Hospital-acquired abscesses are more likely to be associated with severe complications, including sepsis and multiorgan failure, often necessitating intensive care. Delays in diagnosis, antimicrobial resistance, and coexisting conditions markedly increase mortality rates in these patients.

Appendicitis and diverticulitis are among the most frequent etiologies of intraabdominal abscesses, posing the greatest risks.[7] In a study of 243 cases, results showed that appendicitis accounted for most infections, followed by diverticulitis. Polymicrobial infections were prevalent, identified in 81.9% of cases. The study isolated 428 microorganisms, including 412 bacteria and 16 Candida species. Among these, Escherichia coli and Bacteroides fragilis were the most commonly identified pathogens in community-acquired infections, while hospital-acquired cases showed a higher prevalence of Enterococcus faecium. The bacterial distribution also varied by anatomical location; E coli and B fragilis predominated in submesocolic abscesses, whereas Candida species were more frequent in supramesocolic infections. Resistance to antibiotics such as cefotaxime-metronidazole was more pronounced in hospital-acquired infections, likely due to the higher proportion of enterococci in these settings.[7]

Pediatric cases offer distinct epidemiological insights. Results from a study of 66 children with intraabdominal abscesses revealed that over 80% of these children presented with leukocytosis and elevated CRP levels, underscoring the importance of these markers in the pediatric population. The most common pathogens were E coli and B fragilis, with specific organisms varying by infection site. For instance, E coli was frequently isolated from renal sources, while Streptococcus viridans were predominant in hepatic abscesses.[43] Nonsexually active adolescents with tubo ovarian abscesses often demonstrated anaerobic gut flora as the primary cause.[41] Risk factors and immune responses may differ in specialized populations. Results from a study examining inflammatory cytokines in individuals with type 2 diabetes found significant differences in interleukin (IL)-8 and IL-10 levels between those with and without intraabdominal abscesses, suggesting that biochemical markers of infection vary based on underlying health conditions.[44] 

Pathophysiology

Intrabdominal abscesses result from a complex interaction between infection, inflammation, and the body’s attempt to localize the insult; they may be focal or widespread within the peritoneal cavity and often arise following gastrointestinal perforation, trauma, or surgery. Postoperative fluid collections, for instance, are typically organized over 5 to 7 days into encapsulated abscesses. These localized purulent collections are walled off by adhesions involving the omentum or nearby viscera, serving as a containment strategy by the host immune system.

The formation of an abscess begins with the invasion of pathogens, often polymicrobial, including aerobic and anaerobic bacteria such as E coli and B fragilis. Pathogens trigger an inflammatory cascade involving neutrophils, macrophages, and cytokines such as tumor necrosis factor-alpha (TNF-α), IL-1, and IL-6. These immune responses create a hypertonic microenvironment that expands the abscess cavity. For example, the polysaccharide capsule of B fragilis enhances its virulence by enabling its survival and proliferation within the anaerobic and acidic milieu of the abscess.[3]

Anaerobic metabolism within the abscess cavity contributes to tissue hypoxemia, diminished oxygen diffusion across capillary membranes, and increases in lactate, which is associated with increased mortality.[45] These conditions impair oxygen diffusion and create conditions resistant to antibiotic therapy and immune clearance. This environment not only sustains the abscess but also increases the risk of systemic complications such as sepsis if left untreated.[8][46][47] The encapsulating pseudo-capsule, primarily composed of fibrin and collagen, limits pathogen dissemination but also inhibits antibiotic penetration and neutrophil function, making the abscess a protected niche for microbial survival. In cases of Crohn disease, the proinflammatory state leads to stricturing, fibrostenosis, and the potential for perforation, which can cause abscess formation and fistulization between structures such as the bowel, bladder, and abdominal wall.[3] Similarly, aseptic abscess syndrome, often associated with inflammatory bowel disease, features sterile neutrophilic infiltrates and granulomatous reactions surrounding the collections, distinguishing it from infectious abscesses.

Without treatment, abscesses can expand due to ongoing inflammation, anaerobic bacterial activity, and the hypertonic environment. This can lead to further complications, including peritonitis and systemic sepsis, which significantly increase morbidity and mortality. Aseptic abscess syndrome, while not infectious, shares a similar immune-mediated inflammatory basis and is often characterized by granulomatous reactions distinct from other neutrophilic conditions such as pyoderma gangrenosum.[39]

History and Physical

History

A thorough history is critical in evaluating a patient suspected of having an intraabdominal abscess. Patients often present with nonspecific symptoms such as fever, malaise, fatigue, and localized or diffuse abdominal pain, typically dull, persistent, and exacerbated by movement or deep inspiration. Nausea, vomiting, and anorexia are common, particularly if the abscess causes gastrointestinal obstruction or inflammation. Chronic symptoms, including weight loss or night sweats, may suggest a more prolonged or insidious process. Understanding the timeline of symptom onset and progression is vital, as acute abscesses, such as those following appendicitis or diverticular perforation, often present rapidly with severe pain and systemic infection. At the same time, more chronic presentations may suggest underlying conditions like Crohn disease or postsurgical complications.

A detailed surgical history is essential, given that over 60% of intraabdominal abscesses are hospital-acquired, frequently resulting from anastomotic leaks, foreign body retention, or surgical contamination. A history of recent abdominal or pelvic surgery, trauma, or invasive procedures like peritoneal dialysis is highly relevant. Preexisting conditions such as inflammatory bowel disease, diverticulitis, or malignancy may predispose individuals to abscess formation. Infectious history is also critical; for example, endocarditis may point to splenic or hepatic abscesses, while a history of tuberculosis or amebiasis in endemic regions may suggest less common infectious causes. Social and environmental factors, such as intravenous drug use, travel to areas endemic for specific pathogens like Entamoeba histolytica, or dietary habits, may further inform the evaluation.

Risk factors such as diabetes mellitus, malignancy, immunosuppressive therapy, or recent antibiotic use can increase susceptibility to infection and complicate management, with poorly controlled diabetes associated with severe or polymicrobial abscesses. A review of systems can uncover related symptoms, such as diarrhea, constipation, urinary frequency, or dysuria, which may suggest abscesses adjacent to the gastrointestinal or urinary tract. For instance, pelvic pain might indicate a tubo ovarian abscess, while right upper quadrant pain with referred shoulder pain could suggest a hepatic abscess. Attention should also be given to systemic signs of sepsis, including high fever, chills, hypotension, tachycardia, and mental status changes, as these indicate advanced infection requiring urgent intervention. A comprehensive history enables clinicians to narrow the differential diagnosis, identify infection sources, and effectively guide diagnostic and therapeutic strategies.

Physical

The physical examination of a patient with an abdominal abscess often reveals signs of localized or systemic infection, ranging from subtle findings in mild cases to overt evidence of sepsis in severe presentations. The patient's general appearance may indicate distress, fatigue, or malaise, with potential pallor, diaphoresis, and tachypnea if sepsis or systemic inflammatory response syndrome is present. Fever is a common finding, though it may be absent in immunosuppressed individuals or those with chronic abscesses. Tachycardia, hypotension, and altered mental status suggest hemodynamic instability, a marker of advanced infection or septic shock. Many patients will be dehydrated and oliguric.[8][48]

Abdominal examination typically reveals tenderness, often localized to the abscess region, though generalized tenderness may be present in cases of associated peritonitis. Guarding, rebound tenderness, or rigidity may indicate irritation of the peritoneum. Palpation might reveal a palpable mass or fullness, particularly with superficial or large abscesses. For example, a pelvic abscess might be appreciated as tenderness in the lower abdomen, whereas a subphrenic abscess could cause referred shoulder pain or tenderness in the right upper quadrant.[49] Percussion may elicit tympany if an abscess has caused bowel obstruction or a dull note over a large collection. Auscultation may reveal diminished bowel sounds suggestive of ileus or inflammation affecting gastrointestinal motility.

Additional signs may point to specific abscess locations or complications. For example, jaundice or hepatomegaly may accompany a hepatic abscess, while flank tenderness or costovertebral angle pain might suggest a retroperitoneal or renal source. Pelvic examination in female patients may reveal adnexal tenderness, a palpable mass, or cervical motion tenderness, raising suspicion for a tubo ovarian abscess or pelvic inflammatory disease. A rectal examination might identify tenderness, fluctuance, or masses suggesting a perirectal or deep pelvic abscess.

The presentation and physical findings may also vary based on the etiology and location of the abscess. For example, Crohn disease is commonly associated with abdominal pain and weight loss, which may precede the formation of an abscess.[50] In postsurgical individuals, the diagnosis of an abdominal abscess may be delayed due to analgesia, but fever, pain, nausea, and anorexia may raise suspicion. A subphrenic abscess may present with shoulder pain, hiccups, or atelectasis.[49] A tubo ovarian abscess may present with abdominal pain, nausea, vomiting, diarrhea, and fevers.[41] A foul odor and crepitance upon palpation often characterize anaerobic infections.[51] If the abscess extends into extraabdominal locations, such as the chest, lower back, gluteals, sacrum, coccyx, or leg, it will cause pain in these areas.[40] If the abscess is retroperitoneal or located deep in the pelvis, signs and symptoms may be vague and relatively minor, including fever, mild liver dysfunction, or prolonged ileus.[52]

In patients with signs of systemic infection or instability, physical examination should extend beyond the abdomen to assess for complications like respiratory distress (suggestive of subphrenic abscess) or joint or extremity findings that could indicate hematogenous spread or septic arthritis. Findings like erythema, warmth, or induration overlying the abdomen might indicate a superficial abscess or cellulitis. In all cases, physical exam findings should be correlated with the clinical history and imaging studies to confirm the diagnosis and guide management.

Evaluation

The evaluation of a patient with suspected intraabdominal abscess begins with a thorough history and physical examination, followed by targeted diagnostic testing to confirm the diagnosis, determine the abscess's location, and assess for complications. Key components of the evaluation include bloodwork, imaging, and microbiological cultures. Laboratory results often reveal leukocytosis, abnormal liver function, anemia, and thrombocytopenia. Blood cultures may be negative, but when positive, they frequently show anaerobic organisms, with B fragilis being one of the most common.

Other markers, such as CRP and procalcitonin, can help assess the level of inflammation or infection, guiding further management. Serum markers like cancer antigen 125 may also be useful in predicting disease severity in cases such as complicated diverticulitis, where higher levels correlate with larger abscesses and a need for more invasive interventions.[53] A retrospective cohort designed to establish a prediction model for the detection of postoperative organ space and surgical site infection in those who underwent gastrointestinal or hepatopancreatobiliary cancer resection determined that laboratory data on postoperative day 3 was predictive of infection.[54]

Imaging is crucial in confirming the diagnosis and determining the abscess’s location and relationship to other structures. Ultrasound is often the first imaging modality, especially in children, due to its availability and lack of radiation. For adults, contrast-enhanced computed tomography (CT) is the gold standard for diagnosing intraabdominal abscesses. This imaging can reveal detailed information about the abscess’s size, location, and relationship with surrounding organs, and it can also help identify the source of contamination, such as perforated diverticula, appendicitis, or bowel perforation. CT is preferred because it is less affected by bandages or drains and allows for better visualization when intravenous contrast is used. In pregnant individuals, ultrasound or magnetic resonance imaging (MRI) is preferred due to the need to avoid radiation.[8][45] MRI is rarely used but can provide detailed soft tissue imaging, especially in complex cases.

CT-guided aspiration is another key diagnostic tool, allowing for sampling the abscess for microbiological cultures and, if necessary, placing an indwelling drain to help resolve the infection.[48][55][56][57] Repeat imaging and cultures may be necessary if there is no clinical response to antibiotics after several days, especially in cases caused by anaerobes.[45] Indications that anaerobes are present include odor, gas formation within the abscess, bowel and vascular structures, and the portal venous system.[51] 

In addition to standard imaging, experimental technologies are being explored to improve diagnosis and treatment outcomes. Results from a study describe a method for measuring the optical properties of an abscess cavity and the uptake of methylene blue as part of a technique for photodynamic therapy, which may help treat recurrent or antibiotic-resistant collections.[58] Finally, specific recommendations from the 2024 Clinical Practice Guidelines from the Infectious Diseases Society of America for adults and adolescents with suspected intraabdominal abscesses suggest that CT should be the initial imaging modality, with the option of intravenous contrast to improve visualization of the abscess wall. In cases where imaging fails to provide a clear diagnosis or in the absence of clinical response to treatment, repeated imaging and cultures may be warranted to assess for complications or to guide therapeutic interventions.

Treatment / Management

Source control is paramount in treating intraabdominal abscesses and involves a combination of antibiotics, drainage, debridement, and removal of foreign bodies. Broad-spectrum antibiotics are initiated early and tailored based on culture results. The decision between drainage and antibiotics alone is debated, with abscess size and biomarkers like CRP playing a role in guiding management.[59] Adjuncts, including nasogastric tubes and parenteral nutrition, may support recovery.[43][60][61] Percutaneous image-guided drainage has been shown to decrease the duration of hospitalization. In most patients, improvement occurs within 48 hours after drainage. CT-guided drainage has a success rate of over 90% for localized abscesses and is the standard of care. Algorithms for drain management are based on the size and etiology of the abscess. Crohn disease, for example, is associated with fistula formation, and persons with related abscesses may require additional imaging.[62] An abscess that fails drain management or is inaccessible to percutaneous drainage requires surgical drainage.[63][64][65] 

The Infectious Disease Society of America published an update on intraabdominal infections in adults, children, and pregnant persons, including guidance regarding an intraabdominal abscess. Recommendations include risk stratification, using the Acute Physiology and Chronic Health Evaluation II score, which estimates mortality at intensive care unit (ICU)-level care, or the World Society of Emergency Surgery Sepsis Severity Score to assess the severity of illness for use within 24 hours of hospital or ICU admission. The authors note the absence of such a scoring system for pediatric individuals and recommend a CT for initial imaging in nonpregnant persons and adolescents with a suspected intraabdominal abscess, including intravenous contrast and ultrasound for children. CT or MRI is designated as an alternative, although either may require sedation. For pregnant persons, MRI or ultrasound is the suggested imaging modality.[66]

The Surgical Infection Society Guidelines for Management of Intraabdominal Infection include recommendations for antimicrobial therapy formulated from analysis of clinical trial data based on risk stratification and provide detailed guidance depending on the organism and calculated patient risk. General recommendations include initiation of antimicrobial therapy within an hour in high-risk patients with sepsis and warning that delays over 6 hours increase mortality.[67] The World Journal of Emergency Surgery published guidelines of the Multidisciplinary and Intersociety Italian Council for the Optimization of Antimicrobial Use in intraabdominal infections. Using an effective antibiotic improves outcomes, including minimizing antibiotic resistance and opportunistic infections. The guidelines note the growth of multidrug-resistant organisms, especially gram-negative bacteria, and emphasize early source control, including image-guided drainage. The council also recommends early empiric antibiotic treatment to improve outcomes in septic persons. The guidelines emphasize an individualized approach to antibiotic therapy to improve efficacy and reduce resistance. Guidelines for specific disease entities are provided in the publication.[45] A recent study's results demonstrated gram-negative bacteria within an intraabdominal abscess were most responsive to meropenem, followed by piperacillin-tazobactam, and gram-positive bacteria were over 80% responsive to amoxicillin-clavulanic acid, piperacillin-tazobactam, and meropenem.[7][68] 

The approach to abscess treatment varies by anatomic location. While a subdiaphragmatic abscess can be drained percutaneously, a pelvic abscess is accessed transrectally or transvaginally. Endoscopic ultrasound-guided drainage provides a safe and effective minimally invasive treatment option.[69][70] Transesophageal and transgastric approaches have been used for a subphrenic abscess.[71] Splenic abscesses have been traditionally treated with splenectomy, but percutaneous drainage has been correlated with lower mortality and complication rates.[72] Results from a study showed that abscess size, age, inflammatory markers, leukocytosis, and erythrocyte sedimentation rate were predictive of the need for surgical intervention due to failure of pharmacologic treatment.[73]

Study results have demonstrated the benefits of using a nonoperative approach with drain placement for appendicitis with abscesses. These include fewer complications, shorter hospitalizations, fewer wound infections, and reduced incidence of ileus.[65][74][75] A multicenter study on the impact of a prophylactic drain in the setting of perforated appendicitis in adults provided results that showed drain placement did not reduce the incidence of an abscess and was associated with a longer hospital stay. Operative grade, as described by the American Association for the Surgery of Trauma, was associated with abscess risk.[76] An abscess size of less than 4 cm is associated with successful percutaneous drain management of appendicitis-related abscesses in the pediatric population.[77] Results from a postoperative study in pediatric perforated appendicitis with abscess demonstrated the interval between diagnosis and percutaneous drainage was not associated with the need for additional intervention, drain dwell time, or length of stay.[78] In a study of 1766 postappendectomy abscesses in children treated with antibiotics, 67 of whom had abscesses smaller than 6 cm, and 22 of whom had an abscess larger than 6 cm, results showed that abscess size did impact the duration of intravenous treatment and hospital stay.[79]

Abscess size amenable to percutaneous drainage differs by anatomical location and etiology. An abscess of 3 to 6 cm is generally accepted as a cutoff for a diverticular abscess that can be successfully treated with percutaneous drainage.[77] Results from a study indicated that surgical intervention for collections of less than 4 cm lowers the risk of a recurrent diverticular abscess.[80] A multicenter study in Spain evaluated outcomes following the first-time diagnosis of a diverticular abscess to develop a model to predict the need for emergency surgery. Per the study's results, immunosuppression, CRP, free air, and larger abscess size were associated with the need for emergency surgery.[81]

Persons with Crohn disease may form spontaneous abscesses, and treatment, either immediate resection or nonoperative management, depends on clinical presentation. Study results show good surgical outcomes following initial nonoperative management of a Crohn abscess.[82] A study evaluating the treatment of Crohn abscess across periods of 1, 2, and 5 years found abscess diameter, width of sinus, and abscess location associated with the need for invasive treatment.[83] Results from additional studies have shown that factors including bowel wall thickness, dilation, length of the involved segment, and abscess greater than 6 cm are related to the need for subsequent surgery.[84] A study compared antibiotics, percutaneous drainage, and surgical drainage in persons with Crohn disease; the results described abscess size to be a factor in treatment efficacy. Where abscesses greater than 30 mm were responsive to antibiotics, surgery was superior to percutaneous drainage for an abscess less than 50 mm but with a higher complication rate. The authors concluded that percutaneous drainage is safer than surgery and generally as effective.[17] Those who recover following nonoperative treatment of a Crohn abscess are shown to benefit from anti-tumor necrosis factors. This biologic medication decreases inflammation by blocking the tumor necrosis factor protein. Biologic therapy is most successful in those who have not previously undergone resection.[17][18][50]

Studies have been conducted on the ideal timing for surgical intervention in those with Crohn disease who have undergone percutaneous drainage of an intraabdominal abscess. A multicenter study assessed outcomes in those with Crohn disease who underwent percutaneous drainage of an abscess within 6 weeks before resection, and the results showed morbidity and anastomotic leak higher in that group.[85] A multicenter cohort looked at 30-day postoperative complications and intraoperative adverse events, including sepsis, surgical site infections, postoperative ileus, and abscess recurrence in those undergoing resection for Crohn disease following nonoperative abscess drainage. The author's results showed that age, residual abscess, smoking status, low serum albumin, and time interval to surgery were associated with postoperative complications.[86] 

For aseptic abscess syndrome in those with inflammatory bowel disease, antibiotics are ineffective, and most persons respond to intravenous corticosteroids followed by maintenance therapy with biologic therapy consisting of antibodies or disease-modifying antirheumatic drugs and steroids. Some patients relapse on steroids alone, and relapse must be differentiated from opportunistic infections that can be prompted by immunosuppressive therapy.[39] Innovation continues to expand the treatment arsenal for an intraabdominal abscess.

A newer therapy intended for difficult-to-treat, persistent, or recurrent abscesses involves photodynamic therapy, using reactive oxygen species as an antimicrobial, used in conjunction with methylene blue as a photosensitizer. Evaluating absorbed light and photosensitization, researchers published results from the first study that measured the optical properties of an abscess. An optical probe collected data within the abscess, and the cavity was infused with methylene blue. The uptake of methylene blue was measured, and photodynamic therapy was implemented within the abscess. There was no statistical difference in methylene blue uptake between antimicrobial-resistant and susceptible microbes.[58]

Differential Diagnosis

The differential diagnosis for an intraabdominal abscess is broad, as the presenting symptoms are nonspecific and can overlap with various conditions. These symptoms often include fever, abdominal pain, nausea, and vomiting. Many intraabdominal space-occupying masses can be distinguished radiographically, and a thorough history, physical examination, and early radiographic findings are essential in narrowing the diagnosis. Conditions that may present similarly to an intraabdominal abscess include:

• Malignancy
  • Tumors or cancers, particularly in the gastrointestinal tract (eg, colorectal cancer), pancreas, liver, or ovaries, may present with a mass-like lesion that could be mistaken for an abscess. Malignant tumors may also undergo necrosis, leading to fluid collections that resemble abscesses.
• Benign mass
  • Nonmalignant masses, such as fibroids or lipomas, could present with similar clinical features as an abscess, particularly if they are large and cause localized abdominal pain or discomfort.
• Fever of unknown origin
  • An intraabdominal abscess may present with fever, but fever of unknown origin has a broad differential, including infections, malignancies, and inflammatory conditions, all of which need to be considered.
• Hernia
  • Abdominal hernias, particularly those that are incarcerated or strangulated, can present with localized pain, fever, and abdominal distension, mimicking the presentation of an abscess.
• Hematoma
  • Abdominal hematomas resulting from trauma or surgery can present with a mass, tenderness, and pain that may be difficult to differentiate from an abscess, particularly in the postoperative setting.
• Organ infarction
  • Infarction of intraabdominal organs, such as the spleen or liver, can cause localized pain and form fluid collections resembling an abscess.
• Ascites
  • The accumulation of fluid within the peritoneal cavity due to liver disease, malignancy, or heart failure can present with abdominal distension and tenderness. While ascites can sometimes be complicated by infection, this condition should be distinguished from an abscess.
• Peritonitis
  • An infection or inflammation of the peritoneum can cause symptoms and signs that mimic an abscess, including fever, tenderness, and abdominal distension.
• Other considerations
  • Pancreatic pseudocysts 
  • Inflammatory bowel diseases 

Pertinent Studies and Ongoing Trials

Yuan et al studied factors associated with the development of an intraabdominal abscess following laparoscopic appendectomy for perforated appendicitis in older adults. Their results found a correlation between a lower prognostic nutritional index and increased risk for abscess within 30 days.[87] Smith et al conducted a retrospective study within 13 level I and II trauma centers, including adults with grade 3 and higher trauma to the liver who underwent operative intervention to determine risk factors associated with abscess formation. Out of the 372 persons studied, 79 (21.2%) developed an abscess. The study results described that the mechanism of injury, initiation of intraoperative massive transfusion protocol, presence of bile leak, hospital length of stay, and additional injuries were independent risk factors for the development of an abscess.[88]

Intrabdominal abscess following pancreatic surgery was found to be an independent risk factor for delayed postpancreatectomy hemorrhage, more likely to occur in those who did not undergo drainage for their abscess.[89] Zheng et al studied perforated appendicitis in pediatric patients to determine predictive laboratory values for the formation of an abscess; the results showed significant overlap between those with and without an abscess.[90]

A study of the efficacy of intraoperative peritoneal lavage on the prevention of postoperative abscess evaluated 10 randomized controlled trials, including 1318 persons with appendicitis or peritonitis, and the results demonstrated that this practice was not associated with reduced mortality, abscess, surgical site infections, complications, reoperation, or readmission.[91] Jen et al studied the impact of postdischarge antibiotics on the formation of an abscess in children treated for perforated appendicitis at their institution, and the results showed that antibiotics did not reduce the incidence of an abscess.[92]

Results from a retrospective study of 592 pediatric patients who underwent surgery for acute appendicitis demonstrated that those who received antibiotics in the first 8 hours of diagnosis reduced the incidence of an intraabdominal abscess from 25% to 5.5%.[93] A multicenter study was conducted of persons who underwent nonoperative treatment of a diverticular abscess with either antibiotics alone or in conjunction with percutaneous drainage to identify independent risk factors for those who require emergency surgery. Of the included persons, 27% needed emergency surgery, and predictors of nonoperative treatment failure included a Hinchey abscess classification IIb or greater, air within the abscess cavity, and smoking status.[94]

Results from a study conducted in Italy by Frediani et al demonstrated the efficacy of intraperitoneal irrigation with cefazolin at the end of a laparoscopic appendectomy in preventing a postoperative abscess.[95] Researchers generated a classification system utilizing the degree of contamination in perforated appendicitis to predict outcomes. They demonstrated more postoperative complications, including intraabdominal abscess, in the group with the most widespread contamination than other groups evaluated.[96]

Prognosis

Several critical factors, including timely diagnosis and intervention, patient comorbidities, abscess characteristics, and management effectiveness, influence the prognosis of intraabdominal abscesses. Complicated intraabdominal infections can carry mortality rates of up to 40%, particularly when associated with sepsis, delayed diagnosis, or inadequate source control.[33] Key variables such as advanced age, malnutrition, diabetes, chronic anemia, and limited access to surgical centers exacerbate the clinical severity, increasing the risks of perforation, peritonitis, and abscess formation.[97]

Prognostic Factors and Outcomes

Timely and effective source control, such as image-guided drainage, is pivotal in reducing morbidity and improving survival rates. Delays in treatment—especially beyond 6 hours in patients with sepsis—markedly increase mortality.[45] Sepsis, recurrent surgeries, and loculated abscesses further elevate the risks.[33] Additionally, prognostic laboratory markers like elevated CRP (>12.06 mg/dL) and blood urea nitrogen (>21 mg/dL) are associated with a higher likelihood of requiring inotropic support and poorer outcomes.[48]

Study results highlight the importance of abscess size in determining the success of conservative management. Larger abscesses, particularly in diverticular disease, are more likely to fail nonsurgical interventions.[98] Postoperative intraabdominal infections, especially in individuals with cancer, may negatively impact short-term outcomes such as recurrence-free intervals but do not significantly affect long-term survival in colorectal cancer patients.[99]

Mortality and Complications

If untreated or misdiagnosed, intraabdominal abscesses have a very high mortality rate. Key factors contributing to mortality and morbidity include:

• Sepsis and organ dysfunction
• Delay in initiating appropriate treatment
• Advanced age and associated frailty
• Presence of multiple comorbidities, such as diabetes or immunosuppression
• Loculated or complex abscess collections that require advanced drainage techniques

Advances in Management and Prognosis

Image-guided drainage, often the first-line intervention for accessible abscesses, significantly reduces morbidity by avoiding invasive surgery. Surgical options, including laparotomy or laparoscopy, can achieve effective source control for abscesses resistant to percutaneous drainage. The size of the abscess and the presence of other complications often influence elective or urgent surgery for diverticular abscesses.

Complications

An intraabdominal abscess, often arising as a complication of surgery or untreated intraabdominal infections, can lead to significant morbidity and mortality if not managed appropriately. Local complications include peritonitis due to abscess rupture, fistula formation into adjacent organs, bowel obstruction from inflammatory edema or adhesions, and erosion into vascular structures resulting in catastrophic hemorrhage. Chronic inflammation may also lead to adhesions, fibrosis, and recurrent abscesses, complicating future surgeries. Systemic complications include sepsis, septic shock, multiorgan dysfunction syndrome, bacteremia, infective endocarditis, thromboembolic events, and systemic inflammatory response syndrome. Long-term sequelae, such as chronic pain, malnutrition, and recurrent abscesses, are common, especially in patients with underlying comorbidities.

Drainage of abscesses, whether percutaneous or surgical, is a critical component of treatment but carries its risks. Incomplete drainage may leave a residual abscess cavity prone to biofilm formation and antibiotic resistance.[58] Drain-related complications include perforation of nearby viscera or blood vessels, retrograde infection due to prolonged indwelling time, and clogging from drain sampling for culture.[100] Persistent infection or inadequate drainage can result in septic sequelae, including deep vein thromboses and complications like fistula formation.

Timely and effective source control, such as early drainage and appropriate antibiotic therapy, is essential to reduce morbidity and mortality. Prognosis is heavily influenced by factors such as the patient’s age, comorbidities (eg, diabetes or chronic anemia), sepsis, and the timeliness of intervention. Preventing complications requires a multidisciplinary approach, including precise imaging for diagnosis, careful selection of drainage techniques, and vigilant postprocedure monitoring for signs of recurrence or systemic deterioration.

Postoperative and Rehabilitation Care

Postoperative and rehabilitative care for patients recovering from an intraabdominal abscess focuses on promoting healing, preventing recurrence, and addressing complications. Regular clinical assessments and imaging, such as ultrasound or CT scans, are essential to confirm abscess resolution and detect potential complications like recurrent abscesses, fistulas, or persistent infections. Continued antibiotic therapy tailored to culture results is critical for eradicating residual infection, with vigilance for signs of sepsis or secondary infections. Proper management of surgical or percutaneous drains, including timely removal, helps minimize the risk of retrograde infections or clogging. Nutritional support is vital, focusing on a high-protein, nutrient-rich diet or supplemental enteral or parenteral nutrition for those with significant weight loss or poor oral intake.

Rehabilitation programs should gradually reintroduce physical activity to prevent complications such as deep vein thrombosis and promote overall recovery. Optimizing chronic conditions like diabetes, anemia, or immunosuppression is crucial to enhance recovery and reduce the risk of recurrence. Additionally, addressing mental health needs and providing psychological support can help patients manage stress or anxiety related to their illness or prolonged recovery. Comprehensive, interdisciplinary care is essential to ensure a successful recovery and minimize long-term sequelae.    

Consultations

Care for a person with an intraabdominal abscess necessitates a collaborative, interprofessional approach involving multiple specialists. Radiologists and interventional radiologists are critical for diagnosing and managing abscesses with imaging and percutaneous drainage. General surgeons oversee surgical interventions when drainage is insufficient, or the abscess is inaccessible. Gastroenterologists may assist in managing underlying conditions such as Crohn disease, while oncologists and gynecologists may be involved depending on the etiology, such as malignancy or gynecologic sources. Pharmacists ensure appropriate antibiotic stewardship and infectious disease experts guide antimicrobial therapy based on culture data. This teamwork is essential for optimizing outcomes and patient safety.

Deterrence and Patient Education

Deterrence and patient education are vital components in managing and preventing intraabdominal abscesses. Patients should be counseled on the importance of timely medical evaluation for abdominal pain, fever, or signs of infection, as delays in diagnosis and treatment can lead to severe complications. Educating patients about the risks associated with surgical procedures, particularly those with predisposing factors such as diabetes, immunosuppression, or malnutrition, can help them understand their role in preventing infections. Patients should be advised on the importance of adhering to prescribed antibiotics and completing the full course of therapy to reduce the risk of recurrence or resistance.

For those undergoing surgical or percutaneous interventions, proper wound care and awareness of signs of wound infection are crucial. Maintaining optimal nutrition and controlling underlying chronic conditions, such as diabetes or anemia, are essential preventive strategies. In cases where abscess formation is linked to specific diseases, such as diverticulitis or inflammatory bowel disease, patients should be educated about managing these conditions and recognizing early signs of complications. Encouraging regular follow-ups and imaging studies when indicated ensures ongoing monitoring and early intervention if needed. Empowering patients with knowledge and resources fosters better outcomes and reduces the likelihood of recurrence.      

Pearls and Other Issues

Antibiotic stewardship is important and reduces healthcare-associated infections and associated costs. Recommendations include using the hospital antibiogram and screening for carbapenemase-producing Enterobacter. Also, monitoring the intraperitoneal flora throughout hospitalization to avoid increasingly resistant strains during subsequent intervention is important. Consulting with a pharmacist and an infectious disease specialist will help guide decision-making.[7][45] Results from a study of pediatric patients who developed a postappendectomy abscess, 50% of collections cultured contained a resistant organism, including 20% E coli, over 92% Pseudomonas, and 100% Enterococcus, suggesting the need for culture results to target antibiotic therapy.[101]

The immediate physiologic impact of an intraabdominal abscess is significant. While many suspect pulmonary embolus as the etiology for decompensation following trauma laparotomy or prolonged hospitalization, in a study of persons who underwent CT scan for clinical deterioration after a trauma laparotomy, only 3 had a central pulmonary embolus, 18 peripheral emboli, and 222 had an abscess, phlegmon or pseudoaneurysm.[102] Postoperative infection in persons with malignancy contributes to recurrence and reduced overall and disease-free survival.[103][104]

Visceral fat may be correlated with risk for postoperative complications, including intraabdominal abscess.[105][106] A study of patients undergoing laparoscopic pancreaticoduodenectomy provided results showing that those with greater abdominal depth to body mass ratio had a higher prevalence of complications. Researchers found a ratio greater than 2.7 m³/kg to be an independent risk factor for postoperative complications.[107] Improving the nutrition of those with low skeletal muscle mass may reduce postoperative infections.[108] Preoperative enteral nutrition may reduce postoperative complications, including an abscess in persons with Crohn disease.[109] Individuals who were part of an enhanced recovery after surgery program following gastrectomy for gastric cancer had fewer intraabdominal abscesses compared with those who were not part of the program.[110] Sarcopenic persons who underwent hepatectomy for hepatocellular carcinoma had an increased incidence of intraabdominal abscess and bile leak, and sarcopenia was found to be an independent risk factor for these events.[111] Imaging in aseptic abscess syndrome may reveal multiple abscesses within the spleen, liver, lungs, kidney, pancreas, lymph nodes, brain, and testes. If a person with this presentation has not been previously diagnosed with inflammatory bowel disease, they will require a colonoscopy.[39] 

Enhancing Healthcare Team Outcomes

Managing an intraabdominal abscess requires a coordinated interprofessional approach involving clinicians, nurses, pharmacists, and other healthcare professionals. Only through a systematic clinical interprofessional team approach can the morbidity and mortality of an abdominal abscess be reduced.[112][113] These abscesses can be challenging to diagnose and treat, and timely, effective communication among the team is crucial. Nurses and advanced clinicians play a key role in continuous monitoring for signs of deterioration, including drain output and patient’s clinical status. The surgical team oversees interventions, ensuring timely source control and managing any complications.

Pharmacists are integral to directing antibiotic therapy, ensuring regimens are tailored to culture results and hospital antibiograms, which help combat resistant organisms. Nutritionists contribute significantly by calculating caloric needs and addressing dietary deficiencies, particularly for patients requiring total parenteral nutrition. The surgical team provides critical oversight, monitoring drain outputs and clinical status to prevent delays in treatment, which could lead to adverse events and increased healthcare costs. The key to improving outcomes for intraabdominal abscesses is a coordinated interprofessional approach, with prompt diagnosis, vigilant monitoring, and early, targeted treatment.[114][38]