The accessory spleen: prevalence and imaging findings in 1735 consecutuve patients examined by multidetector CT

Abstract

Accessory spleens represent congenital variants of small isles of normally encapsulated splenic tissue with its own arterial and venous vascularisation and their prevalence seems to range between 10 and 20% (1-5). Accessory spleens do undergo the same pathophysiological mechanisms as the main spleen and, therefore, they may show all the potential lesions that may be observed in the main spleen, ranging from shrinking to swelling, from calcification to cyst or tumor formation and from haemorrhage to infarction. Most accessory spleens are located near the pancreatic tail and the splenic hilum and accurate identification of an accessory spleen may be important to avoid misinterpretation and differentiation from pathologic findings in the upper abdomen (6-8).The only study on accessory spleens -detected by CT -reported even a prevalence of 16% around ten years ago (9). However, this study was performed at the beginning of the era of multidetector computed tomography -using dual phase CT with a collimation of 8 mm for both, the unenhanced and the enhanced portal venous phase scans. Therefore, the present study was initiated with the intention to analyze if an increased spatial resolution by using triple phase MDCT with a slice contrast material (Visipaque 320, GE Medical, Milwaukee, USA) was injected with a flow rate of 2-3 ml/sec. Arterial phase CT data acquisition started 35-40 seconds and portal-venous phase CT started 70-75 seconds after the intravenous administration of 100 ml of contrast material. CT parameters were as follows: Rotation time 0.8, helical thickness: 1.25 mm, pitch: 1.375:1, speed 27.5 mm, interval: 0.6 mm, KV 120, mAs (auto-mA): 400. Reconstructed slice thickness (and interval) was 5 mm for the unenhanced and the portal-venous phase images and 3.75 mm for the arterial phase images. Image analysis was performed on an integrated RIS/PACS work station (Centricity, GE Milwaukee, USA).All CT examinations were retrospectively analyzed by a radiologist, specialized in abdominal imaging on a double monitor work station of an integrated RIS/PACS System (Centricity, GE, Milwaukee) using both, slice after slice and cineviewing -technique in the axial plane, whereas multiplanar reconstructions were used only in selected and unclear cases. The reader was unaware of the reasons for the CT examination and of the clinical histories of the patients. Special emphasis was given on the presence, size, number and location, and if present, on visible pathologies of accessory spleens.The presence of an accessory spleen was confirmed only if it could be clearly depicted as a well circumscribed mass with similar attenuation and contrast enhancement as thickness of 3.75-5 mm would be able to detect more accessory spleens in the normal human population than reported in the literature until present. The present study addresses the CT-prevalence of accessory spleens in the normal population followed by a discussion of normal imaging findings, differential diagnoses and potential pitfalls that all may be helpful for their co...

Accessory Spleen in the Splenic Hilum: a Cadaveric Study with Clinical Significance

“…In addition, the maximum length of accessory spleen was more than that in American people. Romer and Wiesner studied CT-examination of 1735 patients in Switzerland, the accessory spleen was found in 11% of patients (8). …”

“…In the USA, the incidence of accessory spleen was found at autopsy in 10-30% of American population (4). In a European study was found that the accessory spleen was present in 11% of patients undergoing abdominal CT-scan (8). The incidence of accessory spleen ranged between 4.5% and 24.28% in Asian population (9-11).…”

Untitled

“…AS can be encountered on CT in 11.0-18.8% of cases [3,4]. In up to 40% of these cases, the patient has two or more (up to four) AS [4].…”

Epidermoid cyst within an intrapancreatic accessory spleen

“…Approximately 60% are found at the splenic hilum and 33% at the lower pole of the spleen 2. Other locations of accessory spleens, although more rare, include the fundus of the stomach,3 pancreatic tail,4 greater omentum,5 retroperitoneum6 7 and pelvis 8…”