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Splenic abscess

Posted Sun, 04/04/2010 - 09:45 by Norman Loberant

Images

Figure 1a- Initial chest CT.

Figure 1b- Initial chest CT.

Figure 1c- Initial chest CT.

Figure 2- sonography of the spleen showing hypoechoic round lesion and nearby anechoic renal cyst.

Figure 3a- CECT of abdomen.

Figure 3b- CECT of abdomen- coronal reformat.

Figure 4- CT from 2 years previously.

Figure 5- percutaneous drainage.

Figure 6- I week follow up sonography.

Figure 7- 2 week follow up CT.

Figure 8- 3 week follow up sonography.

Figure 9- 5 week follow up sonogram

Clinical History:

An 82-year-old male nursing home resident with multiple medical problems was referred to the hospital because of 2 weeks of fever unresponsive to empirical antibiotic treatment. Because of an abnormal chest x-ray, the patient underwent unenhanced chest CT which showed bilateral pleural effusion and bibiasilar consolidation, presumably compressive atelectasis (Figures 1a and 1b). On the most caudal images of the chest CT, a focal hypoattenuating lesion was seen in the spleen (Fig. 1c). The lesion was denser than the nearby fluid-density large renal cyst, and abdominal sonography also suggested thick fluid content (Fig.2). Contrast-enhanced abdominal CT showed no enhancement of the splenic lesion (Figures 3a and b). The patient had undergone prior abdominal CT two years previously and the spleen and lung bases had been normal (Fig. 4). A new hypodense lesion in the setting of persistent fever suggested splenic abscess and percutaneous drainage was performed, yielding thick pus (Fig. 5). At the time of drainage, penetration of the abscess capsule was found to be difficult, suggesting a chronic process. Although the patient's blood cultures yielded enterococcus, the abscess aspirate was sterile. Subsequent echocardiography showed vegetations on both the mitral and aortic valves. Follow up sonography and CT of the spleen showed no reaccumulation of fluid in the abscess cavity(Figures 6,7,8). After removal of the drainage catheter, a five-week post-drainage ultrasound showed a normal-appearing spleen (Figure 9). The patient’s fever resolved, and he is currently receiving long-term continued antibiotic treatment.

Findings:

Figure 1a. Unenhanced CT of the chest showing bilateral pleural effusion and basilar compressive atelectasis.
Figure 1b. Unenhanced CT of the chest showing bilateral pleural effusion and basilar compressive atelectasis.
Figure 1c. A hypoattenuating splenic lesion is seen as an incidental finding.
Figure 2. Sonography of the spleen confirms a hypoechoic 6.5 cm lesion in the lower pole of the spleen.
Figure 3a. CECT of the abdomen shows the nonenhancing solitary splenic lesion.
Figure 3b. Coronal reformat shows the splenic lesion in proximity to a large renal cyst. Pleural effusion is also noted.
Figure 4. Abdominal CT from two years previously shows normal spleen.
Figure 5. CT image from percutaneous drainage procedure with the catheter coiled in the abscess cavity.
Figure 6. One week post-procedure sonography shows an ill-defined hypoechoic focus in the spleen.
Figure 7. Eleven day post-procedure CT shows the catheter in place, and no visible fluid collection.
Figure 8. Three weeks post-drainage, and the catheter is seen in the lower pole of the spleen with a small amount of surrounding hypoechoic tissue.
Figure 9. The drainage catheter was removed and follow up sonographic exam 5 weeks after drainage shows a normal-appearing spleen (F= pleural fluid).

Diagnosis:

Splenic abscess (developing in a patient with endocarditis)

Discussion:

Splenic abscesses vary in both severity and incidence, from very rare multiple or multilocular abscesses occurring in mostly immunocompromised patient populations, to the more common and more successfully treated single, unilocular lesions. Mortality from the former type approaches 80% while it is estimated to be 15-20% in the latter, healthier patient population (1). Approximately two-thirds of splenic abscesses are solitary in adults, while approximately two-thirds are multiple in children. Predisposing conditions include diabetes mellitus, malignancy, polycythemia vera, endocarditis, previous trauma, sickle cell disease, UTI, IV drug use, and AIDS and other immunocompromised conditions. The most common methods of spread are hematogenous, in cases of endocarditis, osteomyelitis, or IV drug use, and spread from a contiguous site of infection.
Splenic abscess is suspected in cases of fever that is recurrent or unresponsive to antimicrobial treatment. They most commonly present with a triad of clinical and laboratory symptoms: fever, left upper abdominal pain (though pain can be localized elsewhere in the abdomen or in the left chest), and leukocytosis (2). Other symptoms and signs can include peritonitis, chills, and constitutional symptoms.
Diagnosis by CT scan is most accurate, but ultrasound can effectively demonstrate many of the characteristics of splenic abscess. One review of 22 cases of splenic abscess found that while CT detected the abscess in every case, ultrasound failed to detect it in 4 cases, producing a sensitivity for sonography of 69 % (3). Radiological findings most commonly associated with splenic abscess include gas content, progressive enlargement of the lesion, and extrasplenic fluid collections found both on CT scan and sonographic exam. Cystic-like lesions can be seen on CT, and complex internal echogenicity can be found on sonogram (2). In a Taiwanese study of 30 patients with splenic abscess, it was found that 59% of cases had at least one of the above radiological findings, and when examined in combination with the above clinical and laboratory criteria, a diagnosis of splenic abscess could be specified in 87 % of cases (2).
Treatment of splenic abscesses is multifaceted. Unilocular abscesses respond well to IV antibiotics and CT or ultrasound-guided percutaneous drainage, while multilocular abscesses most commonly require splenectomy, and sometimes drainage of the left upper quadrant of the abdomen, as well as IV antibiotics (1). Specific antibiotic therapy is preferred if culture of the infectious agent is possible. Common bacteriological findings in splenic abscesses in Asian populations include E. Coli, Streptococci, Staphylococci, and anaerobes like Bacteriodes (4). In the Spanish study cited above, Mycobacterium tuberculosis was the most common infectious agent, followed by Candida and gram positive-cocci, though this is most likely reflective of the patient population of the study, the majority of whom were immunosuppressed (3).
In conclusion, the combination of clinical, laboratory, and radiological findings reviewed above are fairly diagnostic of splenic abscesses. Splenic abscesses can be associated with a high mortality rate in very ill patients, patients with multiple abscesses, and patients with delayed diagnosis and treatment of the abscess. With timely diagnosis and treatment, however, solitary splenic abscesses have a favorable outcome after treatment with IV antibiotics and CT-guided percutaneous drainage. Multiple abscesses have a poorer prognosis and usually require treatment with IV antibiotics and splenectomy.

References / Suggested Reading:

1. Townsend, C. M., et al, ed. Sabiston’s Textbook of Surgery. (Philadelphia: Saunders/Elsevier), 2008. p. 1635.
2. Ng, Koon-Kwan, et al. “Splenic Abscess: Diagnosis and Management”. Hepato-Gastroenterology 2002; 49:567-571.
3. Llenas-Garcia, J., et al. “Splenic abscess: A review of 22 cases in a single institution”. European Journal of Internal Medicine 2009; 20: 537-539.
4. Koon-Kwan, et al. “Splenic Abscess: Diagnosis and Management”. Hepato-Gastroenterology 2002; 49:567-571.

Author

Linden Karas (1), Norman Loberant (2)

(1) Boonshoft School of Medicine, Wright State University, Dayton OH, (2) Department of Radiology, Western Galilee Hospital, Nahariya, Israel