Discussion
"Wandering" spleen is a rare entity, accounting for less than 0,3% of splenectomies [3,4], in which the spleen is “displaced” from its normal anatomic position, due to congenital or acquired absence or laxity of its ligamentous attachments [1-5].
In children, “wandering” spleen is caused by congenital absence of its anchoring ligaments,with the spleen being displaced from its normal anatomic position, “hanging” freely by a long pedicle that contains the splenic vessels and, often, the pancreatic tail [2-5]. This hypermobile spleen can migrate freely within the peritoneal cavity and, due to its long pedicle, is predisposed to torsion [1,4]. Most commonly, it is found at the left midabdomen.
Congenital “wandering” spleen typically presents between 3 months and ten years old children with a peak presentation before the age of 1 year [2].
Clinical presentation is variable. Patients may be asymptomatic, with an incidentally discovered palpable abdominal mass, or may have atypical abdominal pain or colic [1-5]. The most common complication is torsion of the vascular pedicle, which can be acute or intermittent, spontaneous or following trauma [1,3-5]. 50% of the cases present with an acute abdomen, due to torsion. Vascular obstruction results in splenomegaly, infarction, abscess formation and gangrene [4]. Intermittent abdominal pain is the presenting symptom in cases of vascular congestion and episodes of torsion and spontaneous detorsion [1,4,5]. Splenomegaly, hypersplenism and gastric or esophageal varices with subsequent episodes of gastrointestinal bleeding can develop in these cases. The pancreatic tail can also be involved in acute or intermittent splenic torsion, resulting in acute necrotic pancreatitis or recurrent episodes of acute pancreatitis, respectively [2,4]. Furthermore, due to the absence of the spleen from the left upper quadrant and absence of the gastrosplenic ligament, organo-axial volvulus of the stomach can occur [2]. Other complications include intestinal obstruction [4] and obstruction of the urinary tract.
The diagnosis of “wandering” spleen is established by imaging. Plain radiographs may demonstrate the absence of a splenic shadow at its normal position, presence of bowel gas under the left diaphragm and a soft tissue mass in the lower abdomen or pelvis [1,2,4].
Gray-scale sonography can be diagnostic, demonstrating the absence of a normally positioned spleen and the presence of a well-circumscribed abdominal or pelvic mass with the shape, echotexture and hilar morphology of the spleen [4]. Color-Doppler sonography provides important information about the blood flow within the hilar vessels and the splenic parenchyma [1,4]. It can also demonstrate collateral venous flow in cases of congestive splenomegaly, provided that the examination is not hindered by bowel gas.
Possible pitfalls include:
a) splenic displacement towards the left hypochondrium by palpation,
b) left hepatic lobe enlargement and extension to the left upper quadrant, which can be mistaken for a normally situated spleen,
c) bowel loops filled with gas in the left subdiaphragmatic area or in the midabdomen, hindering optimal sonographic evaluation [3].
CT, with no image degradation by bowel gas is the preferred method for diagnosis.
The most important CT manifestations include:
a) absence of the spleen anterior to the left kidney and posterior to the stomach,
b) a typically comma-shaped ectopic splenic mass [3,4].
After bolus injection of contrast material, splenic vascular and parenchymal enhancement and homogeneity can be evaluated. Venous collaterals, if present, can be traced to their origin.
With MRI, normal displaced splenic mesenchyma can be easily recognized, typically being of low signal on T1-weighted images and of high signal on T2-weighted images.
