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Clinical Observations |
1 Both authors: Departments of Internal Medicine and Hematology, Philipps University Marburg, Baldingerstrasse, 35043 Marburg/Lahn, Germany.
Received December 15, 2004;
accepted after revision February 3, 2005.
Address correspondence to C. Görg
(goergc{at}mailer.uni-marburg.de).
Abstract
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CONCLUSION. In patients with a perisplenic tumor of unknown cause, contrast-enhanced sonography enables the diagnosis or exclusion of accessory spleens.
Keywords: abdominal imaging • cancer • contrast media • spleen
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Accessory spleens probably are the most common splenic anomaly with a frequency of 10-25% of healthy individuals [6]. The location of accessory spleens is variable, but most are adjacent to the medial border of the spleen. Most are less than 1 cm in size, but they may occasionally be as large as 6 cm in diameter. With the widespread use of abdominal sonography, accessory spleens are increasingly visualized, and they may be mistaken for lymphadenopathy or neoplastic masses.
The purpose of this article is to present our experience with contrast-enhanced sonography and a second-generation contrast agent in the assessment of 14 consecutive patients with a perisplenic mass of unknown cause.
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The following B-mode sonographic parameters were evaluated: echotexture of lesions using the splenic echotexture as an in vivo reference (echo-free, hypoechoic, isoechoic, hyperechoic, or complex), number of lesions (solitary vs multiple), configuration (round vs irregular delineated), and maximal size of lesions (in case of multiple lesions, largest lesion was evaluated).
Vascularity of focal lesions was classified by color Doppler sonography using the splenic vascularity as an in vivo reference (avascular, reduced vascularity, isovascular, or marked vascularity). Color Doppler settings were optimized to achieve the greatest sensitivity for allowing detection of low flow.
Contrast-enhanced sonography studies were performed immediately after baseline sonography with a contrast-devoted unit (Acuson-Sequoia gastrointestinal, Siemens Medical Solutions) that had contrast-specific, continuous-mode software. A low-pressure setting was used. A sulfur hexafluoride-based microbubble contrast medium (SonoVue) was injected IV in 2 sec using a 20-gauge needle. A volume of 4.8 mL was administered followed by a 5-mL saline flush. Immediately after contrast medium injection, the perisplenic lesion and the spleen were observed for evidence of contrast uptake over a 5-min period [5]. All the perisplenic lesions, including the intrapanceatic lesion that was located in the tail of the pancreas (case 5), were in the same field of view as the spleen during contrast-enhanced scanning. Contrast-enhanced sonography studies were analyzed based on a review of images stored in the sonographic unit.
The following contrast-enhanced sonography patterns of perisplenic lesions using splenic tissue enhancement as an in vivo reference were considered: enhancement during the arterial phase 5-30 sec after injection and during the parenchymal phase 3-5 min after injection (absent, hypoechoic, isoechoic, hyperechoic, or complex echogenicity). Contrast-enhanced sonography was performed in all patients immediately after baseline sonography. The parameters were determined by a single observer. For characterization of potential interobserver variability, three other completely blinded observers with at least 5 years of sonography experience retrospectively analyzed the data based on a review of images stored in the sonographic unit. There was complete agreement (100% specificity) for accessory spleens by all three additional observers.
Histologic verification of the lesions was performed in two cases by surgery (cases 11 and 13). In the remaining cases (n = 12), diagnosis was confirmed by means of CT (n = 9), scintigraphy (n = 3), MRI (n = 2), endosonography (n = 1), and sonographic follow-up (n = 7). Follow-up ranged from 6 weeks to 12 months.
Final diagnosis of lesions included accessory spleens (n = 8), metastasis of neuroendocrine tumor (n = 2), metastasis of lung cancer (n = 1), gastrointestinal stromal tumor (n = 2), and insulinoma (n = 1).
In patients with accessory spleens, contrast-enhanced CT showed an isoenhancement of the perisplenic lesions in comparison with the spleen (cases 1, 6, 8, and 12). In patients without imaging confirmation (cases 3, 4, and 10), follow-up showed stable size of the perisplenic lesion for 5, 5, and 12 months, respectively. Table 1 summarizes the clinical data of all 14 patients.
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Vascularity by Color Doppler Sonography
Five lesions were found to be avascular. Nine patients revealed flow
signals within the lesion including five lesions with reduced vascularity, two
lesions with an isovascular pattern, and two lesions with a marked
vascularity.
Vascularity by Contrast-Enhanced Sonography
Enhancement effect with visualization of hilar splenic vessels ranged from
10 to 20 sec after contrast medium injection. In all but one patient (case 10
with splenectomy), enhancement of normal splenic tissue was observed and
preserved up to 5 min. During the arterial and parenchymal phases (listed here
as arterial/parenchymal, respectively), all 14 patients revealed contrast
enhancement within the lesion (Table
1). Isoechoic enhancement during both phases (arterial and
parenchymal) was found in all eight cases with the clinical diagnosis of an
accessory spleen (Figs. 1A,
1B,
1C,
2A, and
2B). In six cases, a different
pattern was seen (Figs. 2A and
2B). All these patients had
diagnoses other than an accessory spleen (Figs.
3A,
3B,
4A,
4B, and
4C).
Six patients had an underlying malignant disease, and sonography was performed for tumor staging. In seven cases the perisplenic tumor was found incidentally. One patient (case 13) had syncope. In two cases with malignant disease (cases 6 and 8), the final diagnosis of perisplenic mass was an accessory spleen (Figs. 2A and 2B), and in one case with an incidentally found perisplenic mass, a malignant disease was diagnosed (case 11) (Figs. 4A, 4B, and 4C).
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SonoVue is a novel second-generation sonographic contrast agent. Currently, the use of contrast agents such as SonoVue improves the diagnostic potential of sonographic examinations in different clinical applications including the assessment of carotid and brain arteries [2], renal arteries [2], splenic trauma [14], blunt abdominal trauma [15], and hepatic lesions [16]. During clinical studies, safety parameters (such as vital signs, ECG, oxygen saturation, neurologic examination, and clinical laboratory parameters) were monitored and no clinically meaningful changes were noted [2].
SonoVue can be prepared in a few seconds and can be administrated immediately after baseline sonography. In our institution, the contrast agent is kept in stock at all times so that this technique can be used at any time. In our series, the timeline for baseline sonography and contrast-enhanced sonography was a maximum of 15 min.
Sulfur hexafluoride-based microbubble contrast medium, SonoVue, has shown a spleen-specific enhancement that lasts longer (5 min) than the blood pool and liver enhancement phases [5]. This specific tropism of the microbubble contrast agent to the spleen is poorly understood, but it provides a useful alternative for the identification or confirmation of splenic tissue [17].
As shown in our study, all accessory spleens have a high specific contrast-enhanced sonography pattern characterized by marked contrast enhancement during the arterial and parenchymal phases. The isoechoic enhancement at the parenchymal phase appears to be the most important of these patterns of accessory spleens. It is important to mention the small size of our study as a limitation. The consistency of the findings is encouraging, but larger studies would be useful to support these findings. Although the real value of SonoVue is yet to be proven, our results show a new potential indication for this second-generation contrast agent. Our conclusion is that in patients with a perisplenic tumor of unknown cause, contrast-enhanced sonography enables the diagnosis or exclusion of accessory spleens.
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  C. Gorg, C. Graef, and T. Bert Contrast-Enhanced Sonography for Differential Diagnosis of an Inhomogeneous Spleen of Unknown Cause in Patients With Pain in the Left Upper Quadrant J. Ultrasound Med., June 1, 2006; 25(6): 729 - 734. [Abstract] [Full Text] [PDF]
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