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The discovery of an intra-abdominal mass often poses significant diagnostic difficulties. The following case demonstrates this, and highlights some of the pitfalls.
A 73-year-old man presented with a 2-year history of lower limb paraesthesiae, macrocytosis and a recent onset of left upper quadrant pain. Examination revealed a large, slightly tender, smooth mass arising from the left upper quadrant of the abdomen with the lower edge in the left iliac fossa. Laboratory investigation, including the assessment of catecholamine levels, was non-contributory.
- What investigations might help to determine the nature of the mass?
- What is the probable diagnosis and what other imaging techniques might be useful?
- What is the nature and presumed aetiology of these lesions?
Grey-scale ultrasound examination is a useful primary investigation in determining the nature of discrete intra-abdominal masses, yielding information such as the size of the lesion and determining the mass to be solid or cystic. The structure from which the mass originates may be identified. In many cases ultrasound characteristics may be diagnostic.
In this case ultrasound was misleading, suggesting an enlarged spleen containing a partly sub-capsular/partly sub-splenic collection, with displacement of the kidney into the pelvis. In most cases involving an abdominal mass computed tomography (CT) and magnetic resonance imaging (MRI) are adequate to enable a confident diagnosis.1However, CT also suggested massive splenic enlargement as the cause of this lesion.
A gadolinium-enhanced MRI scan (see figure) demonstrated a 20-cm mainly cystic retroperitoneal mass displacing the spleen superiorly, the left kidney inferiorly, the tail of the pancreas anteriorly, but arising from none of these. The left adrenal gland could not be identified and was thus considered to be the probable site of origin of the mass.
The probable diagnosis, confirmed subsequently after excision, is of an adrenal pseudocyst. Pre-operative diagnosis of adrenal pseudocysts can be problematic, though a number of imaging modalities are helpful. Plain radiographs may show curvilinear calcification above the renal shadow2; speckled calcification suggests malignancy. Excretion urography may show downward displacement and rotation of the kidney, suggesting an often incidental suprarenal mass.3 Usually, particularly in the case of non-functioning adrenal lesions, CT and MRI are adequate. Both will demonstrate a mass with a thick wall and/or prominent septations, which may contain calcification. MRI has the advantage of being able to image in any anatomic plane, hence permitting evaluation of the relationship of the mass with adjacent retroperitoneal structures. This was vital in this case in making the diagnosis before operation. Pitfalls have been reported with both, however. Repeated haemorrhage with resultant multiple central punctate calcifications has caused the CT appearances of a pseudocyst to mimic those of a hydatid cyst.4 Unusual appearances at ultrasound, CT, and MRI have also caused benign lesions to be diagnosed as malignant.5 6 In such cases angiography and adrenal venography, showing the characteristic arching of venules over and around an avascular adrenal mass, may be helpful.2
Adrenal pseudocysts account for 39% of non-neoplastic adrenal cysts. They are cystic lesions with neither an epithelial nor an endothelial lining, thus precluding a more precise classification. Initial reports were of small cysts found incidentally at post mortem, though improved imaging techniques are resulting in a higher reported incidence.7 Most (75%) occur in women, with some suggesting them to be more common in the young and middle-aged. The cyst found here is one of the largest reported, the largest being 33 cm, removed from a West Indian woman.8
The aetiology of adrenal pseudocysts has been the subject of considerable debate. Studies suggest that the majority are of vascular origin,9 due to haemorrhage from a pre-existing vascular anomaly. Organisation of the haematoma results in the formation of a thick-walled pseudocyst. This is borne out by the histological analysis of the cyst reported here. The specimen was 21 cm in diameter, sections confirming a fibrous capsule without endo- or epithelium. The adrenal gland within the specimen was divided into nodules by bands of acellular collagen. A large blood vessel with an abnormal muscle wall was identified, one section of which showed haemorrhage. Haemorrhage in the absence of a vascular anomaly may occur due to crushing injury, birth trauma, or in systemic illnesses such as severe shock, endotoxaemia or haemorrhagic diatheses. Pseudocysts may also develop after bleeding into adrenal tumours. Thus the diagnosis of malignancy must be considered in all cases of pseudocyst, and exclusion of malignancy may, in the absence of symptoms, be the sole indication for surgical excision.
An adrenal pseudocyst.