Infected splenic cyst: An unexpected cause of large abdominal mass in an immunocompromised patient

A 79-year-old woman with a history of anaemia, back pain, difficulty mobilising due to previous malignant spinal cord compression caused by aggressive presentation of multiple myeloma (high IgG kappa paraprotein of 71 g/L) presented a few months following complete remission post-chemotherapy with a distended abdomen and a painful palpable mass.

On reviewing all the cross-sectional imaging pre-chemotherapy, infiltrative splenic enlargement was seen on CT. Pre-chemotherapy PET study showed heterogeneous uptake in the spleen and peripherally FDG avid cystic lesions in the left flank which may be inflammatory.

Following her acute presentation with abdominal distension post-remission with chemotherapy, urgent CT neck, thorax, abdomen and pelvis performed demonstrated a complex abdominal wall cystic lesion measuring 20.8 x 14 x 16 cm tracking towards the atrophied and scarred spleen with evidence of old infarcts. Based on these findings, the haematology team initially considered that this may be a necrotic tumour simulating an abscess.

Drainage of abscess was done under imaging guidance, and 2 litres of thick pus was drained. Culture of the fluid grew both Streptococcus constellatus and Streptococcus anguinis confirming a final diagnosis of an infected haemorrhagic splenic cyst.

Multiple myeloma (MM) is a malignancy of the plasma cells which is the second most common haematological malignancy and represent 2% of all new cancer diagnosis in the United Kingdom. 80% of patients presents with lytic lesions. [1]

Extra-osseous involvement of MM is usually associated with anaplastic and undifferentiated form, which are aggressive. Abdominal manifestations of MM are extremely rare. CT findings of MM abdominal lesions usually show hypervascular focal masses with either homogenous or heterogenous enhancement. On ultrasound, the lesions may be focal, hypoechoic or heterogeneous. [2]

In this case, the patient presented with a new large abdominal mass which rapidly grew during the course of her chemotherapy treatment with VCD (bortezomib, cyclophosphamide, dexamethasone) while her myeloma was in ongoing biochemical remission. Due to her immunocompromised status, the clinical team considered this to be secondary to an aggressive malignant process.

Initial ultrasound confirmed a multiloculated midline superficial abdominal collection with 2 dominant locules with a large connection between them. The fluid within them was echogenic with no vascularity. Foul-smelling green infected fluid was aspirated, and 2 litres of thick pus was drained. The sample grew both Streptococcus constellatus and Streptococcus anguinis. She was started on intravenous antibiotics.

Based on the imaging findings of this patient, the impression was that of a previous splenic infarction and haemorrhage leading to peritoneal fluid tracking from the spleen to the umbilicus. This is evidenced by the atrophied and scarred spleen seen in later images. The intra-abdominal collection was infected and large, causing significant abdominal distension with a palpable mass.

Blood-borne malignancies are recognised to cause splenic infarcts. Splenic infarction can progress to form cyst or pseudocyst, haemorrhages and splenic rupture. In some instances, the infarcted spleen may become infected and lead to abscess formation.

As this case demonstrates, CT findings have been the key in prompting urgent diagnosis and management of an infected collection secondary to previous splenic infarct in a patient with a background of active haematological malignancy. This case also demonstrates the importance of multi-speciality input, with involvement of the haematology, radiology, general surgery and microbiology team in the management of such rare presentations.

We would like to thank the patient for agreeing for her case to be written for publication.