Sandbox:splenic abscess

Overview

Splenic abscess is an uncommon and lifethreatening condition. Clinical presentation, etiological factors, natural history, treatment and prognosis depends on whether the abscess was solitary or multiple.

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.

Classification

Classification by Mechanism of infection

Splenic abscess is classified traditionally based on the mechanism of infection as follows:

• Hematogenous infection
• Contagious infection
• Splenic trauma
• Depressed immune defenses
• Primary splenic disease
• Abnormal blood flow due to hemoglobinopathies

• Unilocular abscess
• Bilocular abscess

• Solitary abscess
• Multiple abscesses: More common in HIV patients.

Pathophysiology

Splenic abscess can result from various sources such as:

• Splenic trauma or splenic laceration
• Hematogenous spread of bacteria
• Contiguous spread of bacteria

Hematogenous Dissemination

Hematogenous Dissemination or arterial dissemination is the most common mode of infection that results in splenic abscess often multiple.

Casuses

Spleenic 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.

• Primary diseases of spleen
• Hemoglobinopathies

Common causes includes:

• Esherichia coli
• Staphylococcus aureus
• Klebsiella pneumonia

Other causes include:

• Streptococcus pyogenes
• Streptococcus pneumonia
• Klebsiella pneumonia
• Bacteroides fragilis
• Pseudomonas aeruginosa
• Staphylococcus aureus
• Proteus mirabilis
• Bacillus cereus
• Salmonella typhi
• Malaria

Monomicrobial Most common causes

Risk Factors

Common risk factors of splenic abscess include:

• Diabetes mellitus
• Immunocompromised conditions such as AIDS
• Pulmonary tuberculosis
• Concomitant parenchymal liver disease such as cirrhosis
• Malignancies
• Trauma

Differentiating splenic abscess from other diseases

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

• Splenic cysts
• Splenic hematomas

Difference between Solitary abscess and Multiple septic abscesses

Characteristic	Solitary abscess	Multiple septic abscesses
Presentation	Common presentation is fever, abdominal pain, nausea and vomiting with signs of left upper abdominal quadrant tenderness, splenomegaly, left pleural effusion, and leukocytosis.	Most commonly present with generalized sepsis because of an ineradicable septic focus remote from the spleen
Caueses	Intravenous drug abuse Iatrogenic operative trauma to the spleen Direct extension from an extrasplenic focus Bacterialendocarditis Mastoiditis	Bacteroides Pseudomonas Serratia Enterobacter Klebsiella Escherichia coli Staphylococcus aureus Streptococcus viridans
Pathological findings	Gross findings: Enlarged spleen with due to large solitary abscesses with thick wall around the abscess to prevent dissemination Microscopic findings: Microscopically the abscess consist of necrotic tissue with a fibrous wall surrounded by inflammatory cell infiltration.	Gross findings: At the time of autopsy, spleen present as large and soft, and pus extruded organ from the cut surface. Microscopic findings: 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.
Complications		Pulmonary infection and abscess Uncontrolled nonsplenic abdominal suppuration Bacterial endocarditis Disseminated neoplasia with septicemia Immunosuppression with septicemia Meningoencephalitis
Treatment of choice	Best initial treatment is percutaneous drainage. If recurrent or not responding to combination of microbial therapy and drainage, then most appropriate treatment is splenectomy.	Splenectomy
Outcome		Most of the patient died of sepsis even though splenic infection had been eliminated

Epidemiology and Demographics

Incidence

Indceidence of spelenic abscess varies between 0.1% to 0.7%.

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.

Natural History, Complications and Prognosis

Splenic abscess is a rare cause of abdominal abscesss, but life-threatening. Because of it's rarity, splenic abscess usually diagnosed at the late stages or after the onset of complications. Early diagnosis, prompt treatment can prevent complications.

Demographics

Developing Countries

In Africa, splenic abscess is more common in hemoglobinopathies such as sickle cell disease [heterozygous (SA or SC) > homogygous(SS)].

Complications

Common complicaiton include:

• Bacterial sepsis or septicemia
• Respiratory complications such as post operative pneumonia

Other complications include:

• Wound infection
• Paralytic ileus
• Deep vein thrombosis
• Meningitis

Association

Splenic abscess is commonly associate with:

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

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.

History and Symptoms

Common symptoms of splenic abscess include:

• Fever
• Abdominal pain
• Nausea and vomiting

Physical Examination Findings

Abdominal Examination

• Tender splenomegaly
• Palpable 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 ratio (ESR)
• Blood culture

Imaging

As the clinical features of splenic absecess 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.

Computerised Tomography

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

• Can differentiate unolocular and multilocular abscesses
• Can identify the contents 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 per-cutaneous drainage.

Splenic Scan

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.

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

Percutaneous Drainage

Percutaneous drainage is the primary mode of tretament 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.

• 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
• 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

• Multiple or septated abscesses
• Anatomically inaccessible for drainage
• Coagulopathies
• Ascites

Splenectomy

Splenectomy is the most effective and definitive treatment of choice for splenic abscess.
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 staphylococcus aureus.
• Mortality rate varies between 0-20%
• Longer duration of hospital stay than percutaneous drainage procedure

Complications such as

• 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.