Teaching Case

The patient presented with left upper quadrant abdominal pain of 3-weeks' duration. Examination revealed a febrile patient with a tender splenomegaly. Abdominal ultrasound revealed a hypoechoic heterogeneous lesion in the spleen. CT scanning demonstrated a large solitary low-density spleen lesion that did not enhance with intravenous contrast.

The patient presented with continuous fever, malaise, and left upper quadrant abdominal pain of 3-weeks' duration. There was no history of trauma. Examination revealed a febrile patient with a tender splenomegaly. The remainder of the examination was unremarkable.

An ultrasound of the abdomen (Fig. 1) revealed a 8.7cm x 5.5cm large hypoechoic heterogeneous lesion in the spleen, suggestive of a splenic abscess. A computerised tomography (CT) scan of the abdomen confirmed these findings. The CT scan demonstrated a large solitary low-density spleen lesion that did not enhance with intravenous contrast (Figs 2,3).

Serological evaluation for HIV, amoebiasis, urine culture, screening for sickle cell trait, lymphoma, immunoglobin and hydatid screening were all negative.

A percutaneous drain was inserted into the collection under US control and about 350cm³ of pus was aspirated. Culture of the aspirate yielded a mixed culture of gram positive and negative organisms. A repeat aspiration of about 100 cm³ was carried out on the third day. Serial ultrasound examinations of the abdomen were performed to assess the evolution of the abscess, which progressively diminished in size. Antibiotics were continued for 6 weeks and, after 3 months, ultrasound demonstrated normal splenic tissue.

Splenic abscess is a rare clinical entity with an incidence of 0.2-0.7% in autopsy-based studies. There are few reports of splenic abscess formation in previously healthy and fit young people.(1,2)

Splenic abscesses have diverse aetiologies. The commonest cause is haematogenous seeding of the spleen from an infective focus elsewhere in the body; infective endocarditis being the commonest source and accounting for 10-20% of all cases. Infections in contiguous areas, such as pancreatitis and pancreatic adenocarcinoma, retroperitoneal and subphrenic abscesses, or diverticulitis, may extend to involve the spleen. Splenic trauma is the other major cause of abscesses. Areas of splenic infarction in disorders such as the haemoglobinopathies (especially the sickle cell variant), leukaemias, and polycythaemia may become infected and evolve into splenic abscesses. Alcoholics, diabetics, and immunosuppressed individuals including patients with AIDS are more susceptible to developing a splenic abscess (1-5). None of these conditions could be identified in the patient in this case.

In primary disease, abscesses are usually solitary and the patient's illness is often limited to the spleen. In secondary disease, these abscesses tend to be multiple. Primary disease, usually a localised problem, generally has a better prognosis than secondary disease.

The mean symptomatic period for patients with splenic abscess is 16 days. Signs and symptoms of splenic abscess are nonspecific, often causing a delayed diagnosis.(2) Leucocytosis is invariably present in all patients.

Findings on abdominal radiographs are also nonspecific in patients with this diagnosis. Abnormal soft tissue density or gas pattern is identified in the left upper quadrant in up to 35% of patients.

A chest radiograph is important for preoperative evaluation but may reveal nonspecific findings with regard to the diagnosis of splenic abscess. The findings on chest radiograph are abnormal in 80% of patients, with elevated left hemidiaphragm (33%), pleural effusion (28%) or lower lobe atelectasis (3,4,5).

Ultrasonography of the abdomen lacks specificity to exclude this diagnosis. It demonstrates hypoechoic (87%) or anechoic (13%) lesions in the spleen, outlined in most cases by irregular walls (3,4,5). Ultrasound is low cost, noninvasive, and readily repeatable to evaluate for interval change.

A CT scan of the abdomen is the most reliable tool for the diagnosis of a splenic abscess, which appears as a low-density mass lesion with peripheral enhancement after intravenous contrast. The presence of a gas or fluid level within the spleen is diagnostic of a splenic abscess. The CT scan, by delineating the exact location of an abscess, also helps in planning therapeutic strategies like percutaneous drainage. Technetium 99m (99m Tc) and Gallium 67 scans are also sensitive, although less specific tools for the diagnosis of a splenic abscess.

Diagnostic aspiration using either ultrasound or CT scanning as a guide is quite useful in establishing the diagnosis as well as in obtaining a specimen for culture to guide antimicrobial choice.

Untreated, a splenic abscess may rupture into the peritoneal or pleural cavity or bowel, and the prognosis in these patients is bleak.

Most physicians regard splenectomy along with antibiotics as the treatment of choice for a splenic abscess. Recent trends in the management of splenic abscess have employed with success techniques such as percutaneous catheter drainage and fine needle aspiration of the abscess (3,4).