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 to range between ~0.4% (range 0.14-0.7%) 2,15. The incidence may be rising due to a rise in use of immunosuppressive agents and prevalence of immunosuppressive states, higher survival of leukemic patients, and to the great incidence of drug abuse 13,15.
The main causes of splenic abscesses include
- infection: anaerobes are thought to be most common infective agent 8
- metastatic infection
- blood bacterial dissemination, such as sepsis
- infective endocarditis
- continuous infection, such as perinephric abscess or infected pancreatitis
- metastatic infection
- splenic infarction and superimposed infection
- immunodeficiency conditions (e.g. chemotherapy / transplant recipients, leukaemia and AIDS): especially for those with multiple splenic abscesses 11
Splenic abscesses often present with either vague or nonspecific signs. Pyrexia is common 3. Patients may present with left upper quadrant tenderness with rigors, chills, leukocytosis, and vomiting.
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 (still with some internal echoes however) to hyperechoic. They may contain septae of varying thicknesses. The presence of gas bubbles may also be seen, although the majority of splenic abscesses do not contain air.
Normally are centrally low density lesions (20-40 HU 17). Minimal peripheral contrast enhancement may be present when a capsule has developed.
May show be 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 - i.e.
- T1: low signal (T1 signal may increase if there are proteinaceous content 20)
- T2: high signal
- 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, 99mTc-HIG (human polyclonal immunoglobulin) scans may show one of 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 splenectomy having a better outcome than percutaneous drainage or intravenous antibiotics alone 3-4.
As a broad differential for splenic lesions you could consider other splenic lesions and anomalies.
- 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)
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