DOI:10.2214/AJR.05.1252
AJR 2007; 188:422-428
© American Roentgen Ray Society
Contrast-Enhanced Sonography of Intrapancreatic Accessory Spleen in Six Patients
Se Hyung Kim1,
Jeong Min Lee1,2,
Jae Young Lee1,
Joon Koo Han1,2 and
Byung Ihn Choi1,2
1 Department of Radiology, Seoul National University Hospital and College of
Medicine, 28, Yongon-dong, Chongno-gu, Seoul 110-744, Korea.
2 Institute of Radiation Medicine, Seoul National University Hospital and
College of Medicine, Seoul 110-744, Korea.
Received July 19, 2005;
accepted after revision August 22, 2005.
Address correspondence to J. M. Lee
(leejm{at}radcom.snu.ac.kr).
Abstract
OBJECTIVE. The purpose of this article is to describe the
characteristic findings of intrapancreatic accessory spleen over time on
contrast-enhanced sonography.
CONCLUSION. On contrast-enhanced sonography, intrapancreatic
accessory spleens showed a characteristic inhomogeneous enhancement on the
early vascular phase, enhancement similar to the main spleen during the
postvascular phases, and prolonged enhancement on the delayed hepatosplenic
phase.
Keywords: contrast media • pancreas • sonography • spleen abnormalities
Introduction
An accessory spleen is a congenital anomaly consisting of ectopic
splenic tissue separated from the main body of the spleen; it occurs in
approximately 10-30% of the population
[1]. The most common site of an
accessory spleen is the splenic hilum, with the pancreatic tail the second
most common site [1].
Although an accessory spleen usually appears as an isolated asymptomatic
abnormality, it may have clinical significance in some situations. In
particular, when the accessory spleen is located in the pancreas, it may mimic
a well-enhancing solid pancreatic tumor. There have been sporadic reports
regarding imaging findings of intrapancreatic accessory spleen in which the
tentative preoperative diagnosis included islet cell tumor, solid
pseudopapillary neoplasm, and metastatic renal cell carcinoma
[2-4].
Given that an accessory spleen does not usually require treatment, accurate
preoperative diagnosis will obviate surgery.
Radionuclide splenic scanning using 99mTc heat-damaged RBCs
(HDRBC) has been regarded as a highly specific test for differentiating
splenic tissue from other tissue based on showing functioning splenic tissue
by means of the phagocytic activity of the reticuloendothelial system (RES)
cells. However, 99mTc HDRBC scintigraphy offers far inferior
anatomic resolution compared with sonography, CT, and MRI, which may limit
detection of small splenic tissue.
Recently, superparamagnetic iron oxide (SPIO)-enhanced MRI has been
proposed as an alternative diagnostic tool for imaging of the intrapancreatic
accessory spleen because of its higher spatial resolution compared with
scintigraphy [5]. Because the
specific diagnosis of intrapancreatic accessory spleen is based on RES
function on both scintigraphy and SPIO-enhanced MRI, we assume that
contrast-enhanced sonography using galactose and palmic acid (Levovist [SH U
508A], Schering), which is known to be exclusively accumulated by the hepatic
and splenic parenchyma due to RES activity on the delayed phase, can provide
valuable information for the diagnosis of intrapancreatic accessory spleen
[6]. Until now, there has been
only one case report describing the contrast-enhanced Doppler findings of
intrapancreatic accessory spleen
[7]; however, to our knowledge
there has been no report addressing the enhancing patterns over time on
contrast-enhanced sonography. Therefore, the aim of this study is to describe
the findings of intrapancreatic accessory spleen on baseline and
contrast-enhanced sonography and to determine the role of contrast-enhanced
sonography for the diagnosis of intrapancreatic accessory spleen.
Materials and Methods
Patients
During the 12-month period from June 2004 to June 2005, we encountered six
patients (four men and two women; mean age, 53 years; age range, 32-70 years)
whose routine CT examinations revealed solid pancreatic lesions suspected of
being intrapancreatic accessory spleens. These patients underwent baseline and
contrast-enhanced sonography examinations using Levovist for characterization
of the pancreatic lesion. The final diagnosis was established by
99mTc HDRBC scintigraphy in three patients and by SPIO-enhanced MRI
in the other three patients. This study was approved by our hospital's
institutional review board. Before undergoing sonography, all subjects gave
their informed consent to allow their data to be used for research
purposes.
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Fig. 1A —45-year-old man with intrapancreatic accessory spleen detected
incidentally during workup for small-bowel submucosal tumor (patient 1). Axial
CT image obtained in portal venous phase shows ovoid, well-enhanced nodule
(arrow) in pancreatic tail. Attenuation of this lesion is
hyperattenuated to pancreas and similar to that of spleen (S).
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Fig. 1B —45-year-old man with intrapancreatic accessory spleen detected
incidentally during workup for small-bowel submucosal tumor (patient 1).
Transverse gray-scale sonography image shows homogeneous and isoechoic nodule
(large arrows) with subtle hyperechoic rim and posterior acoustic
enhancement (double arrows) in tail of pancreas
(arrowheads). Echogenicity of this lesion is similar to that of
pancreas (arrowheads) and spleen (S).
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Fig. 1C —45-year-old man with intrapancreatic accessory spleen detected
incidentally during workup for small-bowel submucosal tumor (patient 1). On
vascular phase contrast-enhanced sonogram obtained 6 seconds after arrival of
contrast material, feeding pedicle (arrowhead) enters into
intrapancreatic accessory spleen (arrow). Degree and pattern of
enhancement of this lesion were similar to those of main spleen (not shown).
LK = left kidney.
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Fig. 1D —45-year-old man with intrapancreatic accessory spleen detected
incidentally during workup for small-bowel submucosal tumor (patient 1).
Serial contrast-enhanced agent detection imaging (ADI software, Siemens
Medical Solutions) sonograms, obtained 34 seconds (upper left), 101
seconds (upper right), and 4 minutes (lower images) after
contrast injection, show homogeneous enhancement of intrapancreatic accessory
spleen (arrows) on postvascular phases (upper images) and
delayed prolonged enhancement (arrow) on hepatosplenic parenchymal
phase (lower left). Degree of enhancement of intrapancreatic
accessory spleen (arrow, lower left) on hepatosplenic
parenchymal phase is similar to that of main spleen (S). LK = left kidney.
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Fig. 1E —45-year-old man with intrapancreatic accessory spleen detected
incidentally during workup for small-bowel submucosal tumor (patient 1). Axial
99mTc heat-damaged RBC SPECT image shows clear accumulation of
radionuclide (arrow) near splenic hilum and confirms diagnosis of
intrapancreatic accessory spleen. L = liver, S = spleen.
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Baseline and Contrast-Enhanced Sonography Acquisition
All baseline and contrast-enhanced sonography examinations were performed
by one abdominal radiologist with 8 years of experience using a Sequoia 512
scanner (Acuson) equipped with a convex 3-5 MHz transducer and agent detection
imaging software (ADI, Siemens Medical Solutions). Before receiving the
contrast agent, all patients underwent baseline examinations including
gray-scale and color or power Doppler sonography examinations.
Levovist, which consists of galactose microparticles (99.9%) and palmitic
acid (0.1%), was injected through a brachial vein as a bolus (within 10
seconds) at 300 mg/mL followed by a 10-mL flush of 0.9% saline solution. After
engaging the ADI function, machine settings, such as the region-ofinterest box
covering the lesion, depth, focus, and time-gain compensation, were
readjusted. The default settings of the other machine parameters for ADI were
as follows: maximum mechanical index, 1.9; a low level of line density; and
frame rate, 9 Hz with no frame averaging (persistence). We used a similar
scanning protocol as that used during our previous studies regarding focal
hepatic lesions [8].
Even though Levovist is one of the most widely available sonographic
contrast agents, it is known to have a weak harmonic response when insonated
with an ultrasound beam at a low mechanical index. Therefore, destruction of
the bubble is required for its detection. Broadband harmonic imaging, such as
phase-inversion harmonic imaging, can effectively show the nonlinear echoes
produced from disruption of microbubbles by the incidental ultrasound beam
[9]. However, with
phase-inversion harmonic imaging, which uses two alternately phased pulses and
adds echoes from both pulses together, the fundamental tissue echoes are
summed to zero and are not detected, but the tissue harmonics and contrast
agent responses are detected together; therefore, the technique is not
literally contrast-specific. On the contrary, with ADI, using two pulses with
the same polarity and subtracting the signals from the two pulses, only
fundamental and harmonic contrast agent signals remain; therefore, ADI may be
referred to as contrast-only imaging. As a result, ADI may depict signals from
microbubbles better than phase-inversion harmonic imaging, and the use of an
intermittent imaging strategy (interval delay) with ADI may effectively reveal
the vascularity of focal lesions and also may help in lesion
characterization.
Four rapid serial sweeps were obtained—that is, vascular phase
(real-time scanning during the 7 seconds after the first arrival of contrast
material), postvascular phases (arterial and portal phases: 30 and 90 seconds
after contrast injection, respectively), and a delayed hepatosplenic
parenchymal phase (3-5 minutes after contrast injection). All baseline and
contrast-enhanced sweeps were obtained as cine loops and transferred to a
PACS.
Standard of Reference Examinations
99mTc HDRBC SPECT—In three patients,
99mTc HDRBC SPECT of the spleen was performed according to the
following protocol. Ten milligrams of sodium pyrophosphate in 3 mL of isotonic
saline was injected IV. Thirty minutes later, 10 mL of blood was withdrawn
from a vein into a heparinized syringe. Next, 20 mCi (740 MBq) of freshly
eluted 99mTc pertechnetate was added to the blood, and the mixture
was heated in a water bath at 49.5°C for 30 minutes. The damaged cells
were then cooled to room temperature and reinjected into the patient.
Abdominal SPECT scintigraphy was performed using a dualhead gamma camera with
low-energy, high-resolution collimators in a 128 x 128 matrix. One
experienced nuclear physician reviewed the scintigraphic images. The
diagnostic criterion used for intrapancreatic accessory spleen was the
presence of a marked increase in uptake of 99mTc HDRBC exceeding
the cardiac blood pool at the site of the suspected intrapancreatic accessory
spleen [10].
SPIO-enhanced MRI—In three patients, SPIO-enhanced MRI was
used as a confirmatory tool to diagnose the intrapancreatic accessory spleen
[5]. A 1.5-T scanner (Sonata,
Siemens Medical Solutions) with a body phased-array coil was used. Before
injection of SPIO (ferucarbotran [Resovist, Schering]), fat-saturated
T2-weighted turbo spinecho (TSE); T2*-weighted gradient-refocused
echo (GRE); and T1-weighted dual-echo GRE images were obtained. Imaging
parameters for T2-weighted TSE sequences were as follows: TR/TE, 1,700/100;
echo-train length, 13; signal acquisitions, 3; slice thickness, 7 mm with
interslice gap of 25%; and matrix, 320 x 280. T2*-weighted
images were obtained using the following parameters: 130/10; 1 signal
acquisition; slice thickness, 9 mm with interslice gap of 25%; and matrix, 256
x 125. The parameters for T1-weighted GRE sequences were 110/5.1 for
in-phase and 110/2.4 for opposedphase; 1 signal acquisition; slice thickness,
7 mm with interslice gap of 25%; and matrix, 320 x 224. Ten minutes
after SPIO administration, T2- and T2*-weighted images using the
same parameters as the unenhanced images were obtained. The dose of
ferucarbotran ranged between 8.0 and 12.0 µmol Fe/kg. The diagnostic
criterion used for intrapancreatic accessory spleen was a loss of signal
intensity of the lesion similar to normal spleen on SPIO-enhanced T2- and
T2*-weighted images
[5].
Image Analysis
Sonography images were evaluated by consensus by two additional
radiologists who were not blinded to the diagnosis of intrapancreatic
accessory spleen. The reviewers determined the location, size, shape,
echogenicity, and homogeneity of the lesion on baseline gray-scale sonography
images. The echogenicity of the lesion was compared with those of the pancreas
and main spleen as one of the three echotextures: low, isotexture, or high. In
addition, the presence of a hyperechoic rim and posterior acoustic enhancement
were also recorded. The presence of vascular hilum within the lesion, which is
known to be a characteristic feature of an accessory spleen, was also
determined on color or power Doppler sonography images
[11].
For contrast-enhanced sonography images, the echo enhancement of the lesion
relative to that of the pancreas and spleen was evaluated on all four
sonography phases. The echogenicity was assigned one of three
characteristics—isoechoic, low, or high—compared with those of the
reference organs. Reviewers also determined whether lesion enhancement on each
phase was inhomogeneous or homogeneous. In addition, the presence of the
vascular hilum entering into the lesion was also determined on the real-time
vascular phase.
Results
Clinical Findings
The pancreatic abnormalities were detected incidentally in all patients.
The indications for the initial CT were the staging of small-bowel tumor and
colon cancer, nonspecific abdominal discomfort, liver abscess, confirmation of
the residual stone after open cholecystectomy and choledocholithotomy, and
common bile duct stone and liver abscess. The mean duration between the CT
revealing the pancreatic abnormality and the diagnosis was 14.3 months (range,
1-53 months).
Findings at 99mTc HDRBC Scintigraphy and SPIO-Enhanced MRI
In three patients, 99mTc SPECT scans confirmed the diagnosis of
intrapancreatic accessory spleen by showing a single focal area of intense
radiotracer uptake near the hilum of the normal spleen on 99mTc
scintigraphy (Fig. 1A,
1B,
1C,
1D,
1E). In the other three
patients, SPIO-enhanced MR images confirmed the diagnosis of intrapancreatic
accessory spleen by showing a significant signal decrease on T2- and
T2*-weighted MR images, similar to signal changes of the spleen
(Fig. 2A,
2B,
2C,
2D,
2E,
2F).
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Fig. 2A —70-year-old woman with intrapancreatic accessory spleen (patient 4).
Baseline gray-scale sonography shows round nodule (single arrow) 1.1
cm in diameter in pancreatic tail. This lesion has lower echotexture than
pancreas (arrowheads) and similar echotexture to that of spleen (S).
Note peripheral high-echoic rim surrounding lesion and acoustic enhancement
(double arrows) posterior to lesion.
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Fig. 2B —70-year-old woman with intrapancreatic accessory spleen (patient 4).
On color Doppler sonography, vascular hilum (open arrow) around
lesion (solid arrow) is suspected but is not definite.
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Fig. 2C —70-year-old woman with intrapancreatic accessory spleen (patient 4).
Contrast-enhanced sonogram obtained 9 seconds after first arrival of contrast
material to splenic artery clearly shows feeding pedicle (open
arrows) entering into intrapancreatic accessory spleen (solid
arrow) from splenic artery.
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Fig. 2D —70-year-old woman with intrapancreatic accessory spleen (patient 4).
Serial contrast-enhanced agent detection imaging (ADI software, Siemens
Medical Solutions) sonograms, obtained 23 seconds (upper left), 37
seconds (upper right), 84 seconds (lower left), and 4
minutes (lower right) after contrast administration, show early
heterogeneous enhancement (upper), late homogeneous enhancement
(lower left), and delayed homogeneous and prolonged enhancement
(lower right). Intrapancreatic accessory spleen (arrow)
shows almost same echogenicity to main spleen (S) on all contrast-enhanced
sonography phases. Both intrahepatic accessory spleen and main spleen show
higher echogenicity than pancreas on all contrast-enhanced sonography
phases.
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Fig. 2E —70-year-old woman with intrapancreatic accessory spleen (patient 4).
On unenhanced MR images, intrapancreatic accessory spleen (arrow)
shows low signal intensity on T1-weighted image (E) and high signal
intensity on fatsaturated T2-weighted image (F).
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Fig. 2F —70-year-old woman with intrapancreatic accessory spleen (patient 4).
On unenhanced MR images, intrapancreatic accessory spleen (arrow)
shows low signal intensity on T1-weighted image (E) and high signal
intensity on fatsaturated T2-weighted image (F).
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Findings at Sonography
Baseline sonography findings—All lesions were located on the
pancreatic tail. The diameter of the intrapancreatic accessory spleen varied
between 1.1 and 2.4 cm (mean, 1.6 cm). All intrapancreatic accessory spleens
were well marginated and were round in three patients, ovoid in two, and
lobulated in one (Figs. 1A,
1B,
1C,
1D,
1E and
2A,
2B,
2C,
2D,
2E,
2F). The echogenicity of the
intrapancreatic accessory spleen was low compared with the pancreatic
parenchyma in five patients (Fig.
2A,
2B,
2C,
2D,
2E,
2F) and isoechoic in one (Fig.
1A,
1B,
1C,
1D,
1E). In all intrapancreatic
accessory spleens, the echogenicity was homogeneous and was identical to that
of the main spleen. Five intrapancreatic accessory spleens showed posterior
acoustic enhancement and all six had hyperechoic rims (Figs.
1A,
1B,
1C,
1D,
1E and
2A,
2B,
2C,
2D,
2E,
2F). On color or power Doppler
sonography images, the blood supply to the intrapancreatic accessory spleens
from the splenic artery or vein could be shown in two patients and was
suspicious in one (Fig. 2A,
2B,
2C,
2D,
2E,
2F).
Contrast-enhanced sonography findings— The contrast-enhanced
sonography features of the six intrapancreatic accessory spleens are presented
in Table 1. On the vascular
phase, the vascular pedicle was clearly visualized in three patients,
including the patient in whom it was suspicious on the color Doppler
sonography image (Fig. 2A,
2B,
2C,
2D,
2E,
2F). All six lesions showed an
inhomogeneous enhancement, well known as the zebra-striped pattern, of the
spleen seen on dynamic CT or MRI
[12] (Fig.
1A,
1B,
1C,
1D,
1E). On the arterial phase,
there was inhomogeneous enhancement in three patients (Fig.
2A,
2B,
2C,
2D,
2E,
2F) and homogeneous
enhancement in the other three (Fig.
1A,
1B,
1C,
1D,
1E). In all six patients, the
intrapancreatic accessory spleen became homogeneous on the portal phase,
showing dense persistent enhancement for as long as 3-5 minutes (Figs.
1A,
1B,
1C,
1D,
1E and
2A,
2B,
2C,
2D,
2E,
2F). In comparison with the
pancreatic parenchyma, the intrapancreatic accessory spleen appeared to be
hyperechoic during all dynamic sonography phases. The echo enhancement of all
intrapancreatic accessory spleens, however, was identical to that of the
spleen on all phases.
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Fig. 2G —70-year-old woman with intrapancreatic accessory spleen (patient 4).
Superparamagnetic iron oxide (SPIO)-enhanced T2*-weighted image
obtained 10 minutes after SPIO administration shows signal drop similar in
degree to that in lesion (arrow) and spleen (S).
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Discussion
With the widespread use of cross-sectional imaging techniques, such as
sonography and CT, for evaluating abdominal diseases, it has become more
common for radiologists to encounter nonsymptomatic benign solid lesions,
including intrapancreatic accessory spleen in the pancreas. As several
previous reports have indicated
[2-4],
however, it may still be difficult to differentiate intrapancreatic accessory
spleen from pancreatic neoplasms such as islet cell tumor, solid
pseudopapillary tumor, hypervascular metastasis, or even ductal adenocarcinoma
and, accordingly, to make a correct diagnosis of intrapancreatic accessory
spleen before surgery. In such circumstances, specific imaging of the
functioning splenic tissue, such as 99mTc HDRBC scintigraphy, is
necessary [10]. Although
99mTc scintigraphy allows selective splenic visualization with an
excellent spleen-to-liver ratio, splenic visualization is still difficult in
conditions in which minimal functioning splenic tissue is present, such as in
cases of an accessory spleen
[13]. Furthermore, a small
accessory spleen of less than 1 cm in diameter may escape detection on
scintigraphy because of low spatial resolution. Given that Levovist has a
capability of being taken up by RES and sonography has high spatial and
temporal resolution compared with scintigraphy, contrast-enhanced sonography
using Levovist may be beneficial for the diagnosis of intrapancreatic
accessory spleen.
In this study, contrast-enhanced sonography showed characteristic
enhancement features that allowed the diagnosis of intrapancreatic accessory
spleen. During the four phases of contrast-enhanced sonography,
intrapancreatic accessory spleens showed enhancement patterns identical to
those of the spleen. In particular, prolonged enhancement of the
intrapancreatic accessory spleen on the hepatosplenic parenchymal phase,
similar to that of the spleen, was observed in all patients. Although the
mechanism of this trapping of Levovist in the spleen and liver on the
hepatosplenic parenchymal phase is not yet completely understood, phagocytosis
of the microbubbles by the cells of the RES, including Kupffer cells, has been
proposed as a most likely explanation
[14]. This mechanism of
enhancement of splenic tissue on the hepatosplenic phase of contrast-enhanced
sonography is theoretically similar to those of 99mTc HDRBC
scintigraphy [10] and
SPIO-enhanced MRI [5]. Given
that sonography offers superior spatial resolution to scintigraphy without the
risk of radiation exposure, is more cost-effective, and requires less imaging
acquisition time than MRI, sonography may be a valuable alternative to
scintigraphy or MRI.
In addition, we also observed inhomogeneous enhancement in all
intrapancreatic accessory spleens on the vascular phase and in most
intrapancreatic accessory spleens on the arterial phase. According to Catalano
et al. [12], between the 12
seconds after contrast material bolus injection when splenic artery
opacification usually begins and 50 seconds after contrast material bolus
injection, there is inhomogeneous enhancement of the splenic parenchyma
resembling the well-known arciform or zebra-striped pattern seen on dynamic CT
or MRI [14]. The inhomogeneous
enhancement of the spleen on the early phase (within 50-70 seconds) is known
to be related to the different flow rates through the red and white pulp
[15]. Therefore, inhomogeneous
enhancement on the early phase could provide another clue to the diagnosis of
intrapancreatic accessory spleen.
Multiphasic CT or dynamic MRI can provide hemodynamic data of focal
pancreatic lesions; this would allow most intrapancreatic accessory spleens to
be diagnosed by showing a similar enhancement pattern to that of the spleen on
all phases. However, contrast-enhanced sonography may provide many advantages
over CT. First, it allows real-time scanning with a greater time window (more
than four phases) than that of CT without any risk related to radiation
exposure and the use of iodinated contrast material. Furthermore, although we
used a high mechanical index, contrast-enhanced sonography technique, and
Levovist, a combined use of second-generation sonography contrast agents and
the low-mechanical-index technology allows real-time scanning and therefore
provides more accurate hemodynamic information
[12]. Therefore, in the
clinical scenario in which a hypervascular lesion in the pancreatic tail is
seen on single-phase CT, contrast-enhanced sonography can be used instead of
additional acquisition of multiphasic CT images.
In addition, all intrapancreatic accessory spleens showed hyperechogenicity
to the pancreas and isoechogenicity to the spleen in all four enhanced
sonography phases. Although some other hypervascular tumors, such as islet
cell tumor, may show a similar enhancement pattern, they usually become low-
or isoechoic to the pancreas on the portal or delayed phase
[16,
17]. Therefore, the prolonged
enhancement relative to the pancreas on contrast-enhanced sonography provides
another clue to the correct diagnosis. Furthermore, islet cell tumor can show
a ringlike enhancement on the arterial phase that differs from the homogeneous
enhancement pattern of intrapancreatic accessory spleen
[16].
Our study has some limitations. First, the inherent limitation of
pancreatic sonography, which is a poor sonic window for the pancreas, also
clearly persists on contrast-enhanced studies. However, because
intrapancreatic accessory spleen is exclusively located in the pancreatic
tail, the sonic window for the pancreatic tail could be achieved through the
spleen with little difficulty. Indeed, all cases in our study could be clearly
depicted on both baseline and contrast-enhanced sonography. Second, because we
used a high-mechanical-index harmonic technique and Levovist in this study,
intermittent scanning was necessary to avoid excessive bubble destruction.
Such intermittent scanning requires much operator skill and may therefore be
responsible for making contrast-enhanced sonography difficult to perform.
Although continuous real-time scanning using low-mechanical-index technology
and more stable second-generation sonography contrast agents could provide
better information regarding the hemodynamics of intrapancreatic accessory
spleen, we believe that the intermittent scanning technique using Levovist,
which has an RES-specific uptake, remains a valuable option for the diagnosis
of intrapancreatic accessory spleen.
In conclusion, Levovist-enhanced sonography revealed the characteristic
enhancement features of intrapancreatic accessory spleen and allowed the
specific diagnosis of intrapancreatic accessory spleen to be made. The
characteristic features of intrapancreatic accessory spleen on
contrast-enhanced sonography were an inhomogeneous enhancement on the early
vascular phase, similar enhancement to the spleen during the postvascular
phase, and prolonged enhancement on the hepatosplenic parenchymal phase.
References
- Halpert B, Gyorkey F. Lesions observed in accessory spleens of 311
patients. Am J Clin Pathol 1959;32
: 165-168[Medline]
- Hamada T, Isaji S, Mizuno S, et al. Laparoscopic spleen-preserving
pancreatic tail resection for an intrapancreatic accessory spleen mimicking a
nonfunctioning endocrine tumor: report of a case. Surg
Today 2004; 34:878
-881[Medline]
- Sica GT, Reed MF. Case 27: intrapancreatic accessory spleen.
Radiology 2000;217
: 134-137[Free Full Text]
- Harris GN, Kase DJ, Bradnock H, Mckinley MJ. Accessory spleen
causing a mass in the tail of the pancreas: MR imaging findings.
AJR 1994; 163:1120
-1121[Free Full Text]
- Boraschi P, Donati F, Volpi A, Campori G. Intrapancreatic accessory
spleen: diagnosis with RES-specific contrast-enhanced MRI. (letter)
AJR 2005; 184:1712
-1713[Free Full Text]
- Blomley MJ, Albrecht T, Cosgrove DO, et al. Improved imaging of
liver metastases with stimulated acoustic emission in the late phase of
enhancement with the US contrast agent SH U 508A: early experience.
Radiology 1999;210
: 409-416[Abstract/Free Full Text]
- Ota T, Ono S. Intrapancreatic accessory spleen: diagnosis using
contrast enhanced ultrasound. Br J Radiol2004; 77:148
-149[Abstract/Free Full Text]
- Kim SH, Lee JM, Lee JY, et al. Value of contrast-enhanced
sonography for the characterization of focal hepatic lesions in patients with
diffuse liver disease: receiver operating characteristic analysis.
AJR 2005; 184:1077
-1084[Abstract/Free Full Text]
- Burns PN, Wilson SR, Simpson DH. Pulse inversion imaging of liver
blood flow: improved method for characterizing focal masses with microbubble
contrast. Invest Radiol 2000;35
: 58-71[CrossRef][Medline]
- Ota T, Tei M, Yoshioka A, et al. Intrapancreatic accessory spleen
diagnosed by technetium-99m heat-damaged red blood cell SPECT. J
Nucl Med 1997; 38:494
-495[Abstract/Free Full Text]
- Subramanyam BR, Balthazar EJ, Horii SC. Sonography of the accessory
spleen. AJR 1984;143
: 47-49[Abstract/Free Full Text]
- Catalano O, Sandomenico F, Matarazzo I, Siani A. Contrast-enhanced
sonography of the spleen. AJR 2005;184
: 1150-1156[Abstract/Free Full Text]
- Hayward I, Mindelzun RE, Jeffrey RB. Intrapancreatic accessory
spleen mimicking pancreatic mass on CT. J Comput Assist
Tomogr 1992; 16:984
-985[Medline]
- Forsberg F, Goldberg BB, Liu JB, Merton DA, Rawool NM, Shi WT.
Tissue-specific US contrast agent for evaluation of hepatic and splenic
parenchyma. Radiology 1999;210
: 125-132[Abstract/Free Full Text]
- Paterson A, Frush DP, Donnelly LF, Foss JN, O'Hara SM, Bisset GS
3rd. A pattern-oriented approach to splenic imaging in infants and children.
RadioGraphics 1999;19
: 1465-1485[Abstract/Free Full Text]
- Ding H, Kudo M, Onda H, Nomura H, Haji S. Sonographic diagnosis of
pancreatic islet cell tumor: value of intermittent harmonic imaging.
J Clin Ultrasound 2001;29
: 411-416[CrossRef][Medline]
- Imai H, Horiguchi Y, Kubo H, et al. Color Doppler signal
enhancement with SH/TH-508 in pancreatic tumors [in Japanese].
Nippon Rinsho 1998;56
: 1018-1023[Medline]
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Abstract
Introduction
