Splenic abscesses, like abscesses elsewhere, are localised collections of necrotic inflammatory tissue caused by bacterial, parasitic or fungal agents.
Splenic abscesses are uncommon, and their incidence in various autopsy series is estimated at ~0.4% (range 0.14-0.7%) 2,15. The incidence may be rising due to a rise in the use of immunosuppressive agents and prevalence of immunosuppressive states, higher survival of leukaemic patients, and high incidence of drug abuse 13,15.
The main causes of splenic abscesses include:
- infection: anaerobes are thought to be most common infective agents 8
- splenic infarction with superimposed infection
- immunodeficiency conditions (e.g. chemotherapy/transplant recipients, leukaemia and AIDS): especially in those with multiple splenic abscesses 11
Splenic abscesses often present with vague, nonspecific signs. Fever is common 3. Patients may present with left upper quadrant tenderness accompanied by rigours, chills, and vomiting. In most immunocompetent patients, a complete blood count will show marked leukocytosis with a left shift.
A plain abdominal radiograph is insensitive in the evaluation of splenic abscesses. Indirect signs include gas within the abscess, and a reactive left sided pleural effusion 3.
Splenic abscesses are typically poorly demarcated with a variable appearance, ranging from predominantly hypoechoic with some internal echoes to hyperechoic. They may contain septae of varying thickness. The presence of gas bubbles may also be seen, although the majority of splenic abscesses do not contain gas.
Ultrasound may also be used to guide abscess aspiration 22 .
Normally are centrally low-density lesions (20-40 HU 17). Minimal peripheral contrast enhancement may be present once a capsule has developed.
May show solitary, multiple, or multilocular intrasplenic lesions. MR imaging characteristics can vary dependant on the size and infectious agent.
Usually, the abscesses are of fluid signal intensity 15, 20:
- T1: low signal (T1 signal may increase if there are proteinaceous content)
- T2: high signal
T1 C+ (Gd)
- there can be minimal peripheral enhancement once a capsule develops 15
- larger lesions can also show peripheral and perilesional enhancement 16
The clinical context is vital in interpreting nuclear medicine images.
In some cases, 99mTc-HMPAO leukocyte scans or 99mTc-HIG (human polyclonal immunoglobulin) scans may show one or more intrasplenic defects 5.
111In leukocyte scans and 67Ga scans may also show a photo-deficient abscess cavity 19.
Treatment and prognosis
Traditional treatment for splenic abscess has been splenectomy and antibiotic therapy but image-guided percutaneous aspiration and drainage can also be considered. While many advocate image-guided drainage 9-10, several publications suggest that splenectomy has a better outcome than percutaneous drainage or intravenous antibiotics alone 3-4.
As a broad differential for splenic abscesses, you could consider other splenic lesions and anomalies.
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- normal appearance of the spleen
- pseudolesion of the spleen: inhomogeneous splenic enhancement
splenic lesions and anomalies
- congenital anomalies
- mass lesions
- infiltrative processes
- incidental splenic lesion (approach)