Splenic abscess

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Venkata Sivakrishna Kumar Pulivarthi M.B.B.S [2]

Synonyms and keywords:Abscess of spleen
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Overview

Splenic abscess is an uncommon and life-threatening condition. Clinical presentation, etiological factors, natural history, treatment and prognosis depends on whether the abscess was solitary or multiple. It is always fatal if left untreated. Most commonly associated with immunodeficient patients especially and hematological disorders such as leukemia and sickle cell disease. Diagnostic needle aspiration is very important in the management with antibiotics as blood culture may not be the best correlate as abscess culture. Antibiotic of choice depends on the organism but aggressive and early surgical intervention of splenic abscess should be encouraged especially when the risk factors are present. High suspicion of splenic abscess with history of risk factors, broad-spectrum empirical antibiotic therapy should be initiated.

Definition

Splenic abscess is defined as any infectious suppurative process involving identifiable macroscopic filling defects either in the parenchyma of the spleen or in the sub-capsular space.

Historical Perspective

• Since the times of Hippocrates, splenic abscess has been reported several times and he described the natural history and prognosis of splenic abscess.
• In the early days of 20th century, splenic abscess most commonly caused by typhoid and then followed by malaria.
• Ooi et al described significant etiological differences such increase in the percentage of abscess cases due to anaerobics as compared to aerobics (7 vs 18-28%), fungi (1 vs 18-41%) as well as mycobacterium tuberculosis (0.8 vs. 14%) in the second half of 20th century.

Classification

Classification by Mechanism of pathogenesis	Classification by Etiology	Classification by Pathological Findings
Splenic abscess is classified traditionally by Chun and colleagues based on the predisposing causes as follows: Hematogenous or Metastatic infection: Seen in endocarditis Embolic phenomenon: splenic abscess developed as consequence of cellular embolism in hemoglobinopathies such as sickle cell disease Contagious infection: Splenic abscesses can develop through continuity of infection from primary sources which are anatomically close (e.g. subphrenic abscesses) Splenic trauma: secondary infections may developed due to splenic trauma. Depressed immune defenses: chemotherapy-induced abscesses developed particularly in leukemias	Classification of splenic abscesses based on the etiological factors is as follows: Mono-microbial abscess Poly-microbial abscess (~10-15%) Sterile abscess (~30%)	Lawhorne and Zuidema classified splenic abscees based on pathological findings as follows: Unilocular abscess Bilocular abscess

Pathophysiology

Splenic abscess can result from various sources such as:

Pathogenic Mechanism	Description
Hematogenous Dissemination	Hematogenous dissemination or arterial dissemination is the most common mode of infection that results in splenic abscess. It is a metastatic infection through hematologic seeding from distant infections such as infective endocarditis, purulent teeth-related infections and urinary tract infections Most common organism involved is staphylococcs aureus Often results in multiple abscesses
Secondary infection of splenic infarction	Embolic or thrombotic non-infectious events due to red cell abnormalities such as hemolytic and sickle cell anemia causes ischemia followed by superinfection of emboli which tend to obstruct free blood flow and oxygen delivery to the spleen on the microscopic level.
Contiguous spread of bacteria	It is a mode of infection spread to the spleen from anatomically neighboring structures such as stomach or large bowel perforation, infected pancreatic cyst, perisplenic or subpleuric abscess. Can cause either solitory or multiple abscesses
Trauma or Surgery	Secondary infections may developed due to splenic trauma during any intra-abdominal procedures. Trauma leads to hematoma formation. In case of penetrating trauma to the spleen or intraabdominal surgery, direct inoculation of the spleen with pathogens may form a septic focus which, left untreated, may lead to formation of an abscess.
Immunodeficiency	It is major factor involved in the course of splenic abscess especially if the causative organism is fungi or any other atypical organism.

Gross Findings

Solitary splenic abscess

• Enlarged spleen with due to large solitary abscesses with thick wall around the abscess to prevent dissemination is seen

Multiple splenic abscess

• At the time of autopsy, spleen present as large and soft, and pus extruded organ from the cut surface.

Microscopic Findings

Solitary splenic abscess

• Microscopically the abscess consist of necrotic tissue with a fibrous wall surrounded by inflammatory cell infiltration.

Multiple splenic abscess

• Multiple microscopically visible foci of infection riddled homogeneously throughout the spleen
• Abscesses are filled with polymorphonuclear leukocytes which were scattered throughout the parenchyma, intermixed with other foci of microinfarction and coagulation necrosis

Association

Splenic abscess is commonly associate with:

• Paranchymal liver disease
• Pancreatitis
• Pleural effusion
• Renal cysts
• Ovarian cysts
• Abdominal lymphadenopathy

Causes

Splenic abscess is caused mostly by monomicrobial but some times it can be caused by polymicrobial agents. Bacteria is more common than other microbial agents such as fungi, protozoa which can cause splenic abscess in immunocompromised patients.

Common causes

The most common causative bacteria of the splenic abscess in 50% of the cases is the aerobic bacteria.

Other common causes of splenic abscess includes:

Aerobes	Anaerobes	Fungal	Parasite
Staphylococcus species Streptococcal species Salmonella species Escherichia coli Klebsiella pneumoniae Pseudomonas aeruginosa Enterococcus species Mycobacterium	Bacteroides Actinomyces Propionibacteriums species Clostridium Fusobacterium	Candida albicans Candida tropicalis Aspergillus	Entamoeba histolytica

Less common causes

• Aureobasidium pullulans
• Bacillus cereus
• Brucella
• Citrobacter freundii
• Cryptococcus neoformans
• Diphtheroides
• Echinococcus
• Enterobacter
• Malaria
• Nocardia
• Proteus mirabilis
• Schistosomiasis
• Shigella
• Staphylococcus epidermidis
• Streptococcus pneumonia
• Streptococcus pyogenes
• Vibrio cholerae

Differentiating Splenic abscess from Other Diseases

Splenic abscess should be differented from other causes of left upper quadrent pain:

• Splenic cysts
• Splenic infarct
• Splenic hematomas
• Subphrenic abscess

Epidemiology and Demographics

Incidence

Incidence of splenic abscess varies between 0.1% to 0.7% based on population based autopsy studies. Incidence of splenic abscess due to hematogenous spread is gradually declining due to increased antibiotic use, but incidence due to fungal infection is increasing due to aggressive chemotherapeutic methods.

Prevalence

Prevalence of splenic abscess is increasing gradually due to increased risk factors and increased imaging modalities that can diagnose more accurately.

Case Fatality Rate

Splenic abscesses are associate with increased morbidity and mortality. If left untreated, mortality is definite (100%). Mortality rate also varies with treatment of choice such as splenectomy, percutaneous drainage, anti microbial therapy carries 8%, 29%, 20% of mortality rate respectively.

Age

Splenic abscess shows bimodal distribution in age of the patients, with peak incidence seen in thirties and sixties. First peak of age group is people < 40 years of age who are immunosuppressed or intravenous drug abusers, who commonly present multilocular abscesses. Second peak of age group patients > 70 years with diabetes or nonendocardic septic focus and commonly develop a unilocular abscess.

Gender

Splenic abscess is more predominant in male compared to female (~2 folds).

Developing Countries

In Africa, splenic abscess is common due to prevalence of hemoglobinopathies such as sickle cell disease, which is a common risk factor for this disease.

Risk Factors

Spleen abscess often co-exists with several risk factors, but the major one is the patient’s immunodeficiency. Common risk factors of splenic abscess include:

Infectious risk factors	Non infectious risk factors
Endocarditis Urinary tract infection Immunocompromised conditions such as AIDS Intensive care unit patients Pulmonary tuberculosis Appendicitis Pneumonia Brucellosis Lung abscess Malaria Diverticulitis Amebiasis Septic syndrome	Diabetes mellitus Concomitant parenchymal liver disease such as cirrhosis Hemoglobinopathies Malignancies Trauma Pre-existing splenic pathology such as splenic cysts, hemangiomas.

Screening

No specific screening test for splenic abscess.

Natural History, Complications and Prognosis

Natural History

Splenic abscess is a rare cause of abdominal abscesses, but life-threatening. Because of it's rarity, splenic abscess usually diagnosed at the late stages or after the onset of complications. Solitory abscess present with delayed onset of presentation with history of trauma, sepsis, or adjacent organ disease with fever, abdominal pain, nausea and vomiting where as multiple splenic abscess most commonly present with generalized sepsis because of an ineradicable septic focus remote from the spleen. Early diagnosis, prompt treatment can prevent complications. Mortality rate is very high if left untreated.

Complications

Life threatening complications	Common complications	Less common complications
Septic shock Splenic rupture and peritonitis	Bacterial sepsis or septicemia Respiratory complications such as post operative pneumonia Fistula formation with abscess	Wound infection Paralytic ileus Deep vein thrombosis Meningitis

Prognosis

Prognosis of splenic abscess depends on the time of diagnosis and treatment. Delay in the management can lead to splenic rupture followed by spilling into peritoneal cavity or an adjacent organ which can lead to septicemia and death in severe cases.

Diagnosis

Splenic abscess commonly present with a triad of symptoms include fever, nausea, vomiting and abdominal pain along with palpable spleen on examination. Early diagnosis with imaging studies and prompt drainage is required to reduce morbidity and mortality. Presence of fever, left upper abdominal pain, leukocytosis and radiologic evidence shows pathology in the left chest X-ray especially in immunocompromised patients are the indications for high suspicion of splenic abscess.

History and Symptoms

Common symptoms of splenic abscess include:

• Fever
• Abdominal pain localized in the left upper quadrant or mesogastrium
• Nausea and vomiting
• Constitutional symptoms such as fatigue, loss of body weight, sweating and chills

Other symptoms include:

• Referred pain in the left shoulder
• Confusion
• Pain in the left lower hemithorax
• Cough

Appearance

Patient with splenic abscess appear ill appearing and diaphoretic

Vital signs

• High-grade fever
• Tachycardia

If patient present with sepsis:

• Hypotension
• Tachycardia
• Increased capillary refill time

Signs of sepsis indicate that splenic abscess is most likely due to bacterial cause than fungal source.

Heart

• New onset murmur may be present

Lungs

• Left sided pleural effusion may be present with signs of:
  • Decreased breath sounds on left side
  • Dullness to percussion on left side
  • Absent tactile fremitus on left side
  • Friction rub over the left chest

Abdomen

Palpation

• Tender splenomegaly
• Palpable spleen or abdominal mass

Auscultation

• Friction rub over the spleen

Blood Tests

Blood tests such leukocytosis are increased but not significant in the diagnosis of splenic abscess because these tests may not be appropriate in immunocompromised patients.

• CBC with differential
• Erythrocyte sedimentation rate (ESR)
• Microbiological tests: In solitary abscesses blood culture is not sensitive in the initial stages when as in multiple abscesses it is helpful in prompt diagnosis and early treatment.
  • Gram stain
  • Bacterial culture
  • Abscess culture
• Mycological tests
  • KOH test
  • Fungal culture

Diagnostic Evaluation of Splenic abscess

Suspicion of splenic abscess (Patients with immunodeficiency disorders, fever, changes in chest X-ray, abdominal pain)

Blood culture

Patient with immunodeficiency disorders?

If immunodeficent patient Initiate wide spectrum antibiotics + antifungal medication

If immunocompetent patient Initiate wide spectrum antibiotics

Ultrasound of abdominal cavity, CT scan with contrast

If imaging shows negative or equivocal with high clinical suspicion of splenic abscess

Arteriography

Presence of indications for minimally invasive procedures

Absence of indications for minimally invasive procedures

Aspiration or abscess drainage under US or CT guidance

Abscess cavity content culture, modification of antibiotic therapy according to culture results; Prolonged antibiotic therapy

If ineffective drainage or recurrent abscess

Spleenectomy or Open abscess drainage

Abscess cavity content culture, modification of antibiotic therapy according to culture results; Prolonged antibiotic therapy

Imaging Findings

As the clinical features of splenic abscess are non specific and vague such as abdominal pain, fever and vomiting, that makes diagnosis is challenging and relied on imaging modalities. Imaging studies such as ultrasound, computerized tomography made the diagnosis early and more accurate that reduces morbidity and mortality.

X-ray

Advantages

• High sensitivity
• Directly points to pathological changes
• It is the first line of examination for patients suspected of an ongoing infection
• Can determine phrenic/ diaphragmatic dome positioning and air-fluid level in the left hypochondrium

Common chest x- ray findings includes:

• Elevated and immobile left diaphragm
• Ipsilateral pleural effusion
• Atelectalic and inflammatory changes in interior lung lobe

Common abdominal x- ray findings includes:

• Shift of the stomach and colon by a soft tissue mass (splenic abscess) which is more rectangular than in other causes of splenomegaly
• Increased air-fluid levels with extra alimentary gas collection in the left upper quadrant

Case courtesy of Dr Hani Salam, Radiopaedia.org, rID: 19149

Ultrasound

Ultrasound shows lesions of mixed echogenicity i.e anechoic central zone with a surrounding hyperechoic area.

Advantages

• Emergency radiography with high sensitivity (75-100%)
• Non invasive
• Cost effective
• Determine the size of the spleen, size of the abscess, its location and echogenicity

CT images

Computerised tomography with contrast is both diagnostic and therapeutic test of choice for splenic abscess.
Advantages

• High sensitivity (88-100%)
• Can differentiate unolocular and multilocular abscesses
• Can identify the contents of abscess
• Can determine the density index of abscess.
• Can differentiate splenic abscess from splenic cysts and splenic hematomas
• More precise and accurate than ultrasonography, in identifying the location of abscess in relation to other internal organs during percutaneous drainage.
• It is superior to all other diagnostic tests for splenic abscess.

|valign=top| Scintigraphic studies include technetium-99m liver and spleen scans, gallium scans, and indium scans. Splenic scan is diagnostic modality to identify abscesses which relies upon splenic uptake of the radionuclide 99m technetium which shows abscess as a negative or filling defect.

Advantages

• High specificity: If patient showing high suspicion of splenic abscess and scan supports the diagnosis, then splenectomy can be performed.

Disadvantages:

• Scan can not identifie or visualize incurable small abscesses.
• Less sensitive: If the scan shows negative or equivocal results for splenci abscess but clinical suspicion remains, an arteriogram should be ordered.

Other Imaging Studies

Scintigraphic studies

Scintigraphic studies include technetium-99m liver and spleen scans, gallium scans, and indium scans. Splenic scan is diagnostic modality to identify abscesses which relies upon splenic uptake of the radionuclide 99m technetium which shows abscess as a negative or filling defect.

Advantages

• High specificity: If patient showing high suspicion of splenic abscess and scan supports the diagnosis, then splenectomy can be performed.

Disadvantages:

• Scan can not identifie or visualize incurable small abscesses.
• Less sensitive: If the scan shows negative or equivocal results for splenic abscess but clinical suspicion remains, an arteriogram should be ordered.

Arteriography

Arteriography is the technique that involves injection of contrast material through a catheter passed retrograde into the splenic artery followed by rapid exposure of sequential x-ray films which shows abscesses as filling defects in the spleen.

Advantages:

More reliable and precise than splenic scan in diagnosing small abscesses.

Disadvantages:

• Invasive technique

Treatment

Medical Therapy

Antibiotic regimen should start before the procedure and continue until 7 days after the procedure. Diagnostic needle aspiration is very important in the management with antibiotics as blood culture may not be the best correlate as abscess culture. Antibiotic of choice depends on the organism, but aggressive and early surgical intervention of splenic abscess should be encouraged especially when the risk factors are present. High suspicion of splenic abscess with history of risk factors, broad-spectrum empirical antibiotic therapy should be initiated. Empiric antibiotic should cover streptococci, staphylococci, and aerobic gram-negative rods such as vancomycin or oxacillin plus an aminoglycoside, a third- or fourth-generation cephalosporin, fluoroquinolone or carbapenem. If culture shows fungi as causative organism, start Amphotericin B immediately and continue for 6-24 weeks and during the procedure amphotericin B should be administered directly into the abscess.

Surgery

Treatment of splenic abscess depends on etiology. In bacterial abscesses, splenectomy combined with post-operative antibiotic therapy is the most appropriate treatment of choice with least mortality rate when compared to percutaneous drainage or antimicrobial therapy.

Percutaneous Drainage

Percutaneous drainage is the initial tretament of choice for splenic abscess even though splenectomy is the definitive treatment because of increased risk of infections in splenectomised patient. It is genereally done under the guidance of imaging studies such as ultrasound or computerised tomography and under the guidence of imaging efficy of percuteneous drainage is equivalent to splenectomy.

• First line of treatment for splenic abscess
• Safe and effective than surgery in both unilocular and bilocular abscesses, especially in peripherally located abscesses.
• Preferred in critically ill patient and patients unfit for general anesthesia

Advantages

• Preserves spleen so, it became the treatment of choice in children to prevent post-splenectomy septicemia
• No abdominal spillage of abscess contents
• Less expensive, high acceptance rate and less operative risk

Complications

• Splenic haemorrhage
• Injury to other abdominal organs
• Septicemia
• Empyema
• Pneumothorax
• Fistula formation
• Deep vein thrombosis

Contraindications or limitations

• Multiple or septated abscesses
• Anatomically inaccessible for drainage such as upper pole or hilar of the spleen,
• Uncontrolled coagulopathies
• Ascites
• Simultaneous surgical procedure required of other indications such as subphrenic abscess
• Abscess perforation or bleeding
• Refractoriness to abscess-content drainage
• Secondary infected spleen hematoma

Splenectomy

Splenectomy is the most effective and definitive treatment of choice for splenic abscess. Splenectomy can be performed either from left subcostal incision or from midline epigastric entry.
Advantages

• Definitive treatment for splenic abscess
• Treatment of choice if more than 2 abscesses are present
• Patients with failed percutaneous drainage
• Patient with recurrent abscesses

Disadvantages

• Splenecetomisesd patients are more prone to infections especially catalase positive bacteria such as Streptococcus pneumoniae.
• Mortality rate varies between 0-20%
• Extended duration operation time, larger volume of intra-operative blood loss
• Longer duration of hospital stay than percutaneous drainage procedure

Complications

• Lung infection
• Wound infection
• Septicemia
• Paralytic ileus
• Deep vein thrombosis

Prevention

Primary Prevention

Primary prevention for splenic abscess can prevent in specific cases especially patients who are at high risk such as immunocompromised patients (e.g. recipients of renal transplants or patients on immunosuppressive drugs for other reasons).

• In transplant patients best way to prevent splenic abscess is by splenectomy, where as in patients with other immunocompromised states it can be achieved by proper care, early detection and aggressive treatment of minor infections.
• Avoid intravenous drug abuse