AJR 2003; 181:1101-1108
© American Roentgen Ray Society
Comparing Thin-Section and Thick-Section CT of Pericardial Sinuses and Recesses
Fumiko Kodama1,2,
Patrick J. Fultz1 and
John C. Wandtke1
1 Department of Radiology, University of Rochester Medical Center, 601 Elmwood
Ave., Box 648, Rochester, NY 14642.
2 Present address: Department of Radiology, Faculty of Medicine Tottori
University, 36-1 Nishi-cho, Yonago, Tottori 683-8504, Japan.
Received August 23, 2002;
accepted after revision April 14, 2003.
Address correspondence to F. Kodama.
Abstract
OBJECTIVE. The aim of this study was to assess the prevalence and
appearance of the pericardial sinuses and recesses on thin-section (2.5- or
3-mm) CT scans compared with thick-section (5- or 7-mm) CT scans.
MATERIALS AND METHODS. Nine hundred forty-one consecutive
contrast-enhanced chest CT scans were retrospectively evaluated. Three hundred
sixty-five patients underwent thin-section CT, and 576 patients underwent
thick-section CT. The prevalence and appearance of every pericardial recess
were determined.
RESULTS. Large recesses such as the superior aortic recess were
depicted in 12.5–30.4% of patients using thick-section CT, whereas
smaller recesses such as the postcaval recess were depicted in fewer than 5%
of patients. With thin-section CT, the depiction rates increased significantly
compared with thick-section CT (p < 0.01). Large recesses were
depicted in 28.7–44.7% of patients, and smaller recesses were recognized
in 10.8–19.8% of patients. Generally, most recesses were linear if they
were small and became band-shaped as the fluid increased. However, the
recesses were often visualized as crescent, triangle, spindle, ovoid,
hemisphere, or irregular shapes.
CONCLUSION. Pericardial sinuses and recesses are more frequently and
better depicted on thin-section CT scans. Knowledge of their locations and
shapes is helpful for distinguishing pericardial fluid from abnormal findings
such as lymphadenopathy and cystic lesions.
Introduction
Within the pericardial cavity, small pockets are formed by the reflection
of the pericardium, in which fluid can collect. These pockets are called
pericardial sinuses or recesses, which include the transverse sinus (aortic
recess and pulmonic recess), oblique sinus, postcaval recess, and pulmonary
venous recess [1]. On CT, these
sinuses and recesses can be recognized as areas of water attenuation around
the great vessels. Some of the larger sinuses and recesses are relatively easy
to recognize and unlikely to present a diagnostic problem. However, others,
especially the less well-known ones, are difficult to differentiate from
mediastinal or hilar abnormal lesions because they can simulate
lymphadenopathy or cystic lesions. An understanding of their normal location
and appearance, coupled with a knowledge of common pitfalls, prevents the
misinterpretation of normal pericardial recesses as abnormal lesions. Previous
reports described the CT appearance of some of these sinuses and recesses, and
superior aortic recess and pulmonic recess have become well known
[2–7].
However, many of these researchers used thicker collimation CT and described
only one or a few recesses. Only three reports describe all pericardial
sinuses and recesses in a small number of cases
[8–10].
To our knowledge, ours is the first report that describes all recesses in a
large number of cases using thinsection CT, including multidetector CT. We
describe the prevalence and appearance of all pericardial sinuses and recesses
and also determine whether there is a significant difference between the
visualization of these sinuses and recesses on thin-section CT and on
thick-section CT.
Materials and Methods
We retrospectively reviewed 365 consecutive thin-section CT scans and 576
thick-section CT scans of the chest obtained in our institution from January
2001 to July 2001 in 895 patients. Fortysix patients underwent both
thin-section and thick-section CT. Each procedure was separated by an interval
of 1–4 weeks. All images were acquired after the administration of IV
contrast material. This study group consisted of 464 females and 431 males who
were 17–97 years old (mean, 55.1 years). Thin-section CT scans were
obtained to evaluate suspected pulmonary embolism, whereas thick-section CT
scans were obtained for a routine check or for evaluation of metastatic
disease, known or suspected lung cancer, pleural effusion, pulmonary
infiltrates, or nodules. Patients who had pericardial effusion were excluded
from this study.
CT scans were obtained using a multidetector CT scanner (LightSpeed QX/i,
General Electric Medical Systems, Milwaukee, WI) and helical CT scanners
(HiSpeed Advantage and HiSpeed CT/i, General Electric Medical System).
Thin-section CT was performed on a LightSpeed QX/i scanner with 2.5-mm
collimation and on HiSpeed Advantage and CT/i scanners with 3-mm collimation.
Standard protocol involved 120–140 kV, 260–320 mA, and 29- to
42-cm field of view. With the QX/i scanner, we used 0.8 sec/rotation and a
pitch of 6, and with a HiSpeed Advantage or CT/i scanner, we used 1.0
sec/rotation. Contiguous axial sections were obtained from the lung apices to
the diaphragm after 150 mL of nonionic contrast material was injected into an
antecubital vein at a rate of 3.5 mL/sec. The scanning delay range was
20–25 sec. Thick-section CT was performed using HiSpeed Advantage, and
CT/i scanners with 5- or 7-mm collimation also scanned the whole lung after a
bolus injection of 100–150 mL of contrast material at a rate of 2.0
mL/sec. Standard protocol involved 120 kV, 240–300 mA, 28- to 42-cm
field of view, and 1.0 sec/rotation.
We defined the pericardial cavity according to previous researchers
[1,
2]
(Fig. 1). The transverse sinus
was defined as the sinus behind the ascending aorta and pulmonary trunk, and
it was divided into the following recesses: superior aortic recesses, inferior
aortic recess, and left and right pulmonic recesses. The superior aortic
recess can be divided into two parts: anterior and posterior portions. The
anterior superior aortic recess lies in front of the ascending aorta, and the
posterior superior aortic recess lies dorsal to the ascending aorta. There is
a connection between them. The inferior aortic recess lies between the aortic
root and the right atrium. It connects upward to the superior aortic recess.
The left pulmonic recess lies beneath the left pulmonary artery extending
posterolaterally to the proximal right pulmonary artery. The left pulmonic
recess is continuous with the superior aortic recess anteriorly and with the
transverse sinus laterally. The right pulmonic recess is the space surrounded
mainly by the following three structures: the left atrium, the aortic root,
and the proximal right pulmonary artery. The left atrium forms the floor and
inferior boundary, and the aortic root and right pulmonary artery form the
posterior and superior boundaries of this recess, respectively. The right
pulmonic recess continues on the posterior superior aortic recess. The oblique
sinus is the sinus behind the left atrium including posterior pericardial
recess. Pericardial reflection between the right and left superior pulmonary
veins transversely separates the oblique sinus and the transverse sinus. The
oblique sinus is contiguous with the subcarinal region, which is called the
posterior pericardial recess. The pericardial cavity proper includes the
following three recesses: the left and right pulmonary venous recesses and the
postcaval recess. The postcaval recess is posterior and right lateral to the
superior vena cava and between the inferior vena cava and the coronary sinus.
The left and right pulmonary venous recesses exist between the superior and
inferior pulmonary veins on each side.
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Fig. 1. —Drawing shows posterior aspect of heart. Transverse sinus,
mainly behind ascending aorta and pulmonary artery, is divided into anterior
(1) and posterior (2) portions of superior aortic recess, inferior aortic
recess (3), and left (4) and right (5) pulmonic recesses. Oblique sinus (6)
lies posterior to left atrium. Pericardial sinus proper includes postcaval
recess (7) and left (8) and right (9) pulmonary venous recesses. Note
connections (arrows) between sinuses and recesses. Ao = aorta, SVC =
superior vena cava, lPA = left pulmonary artery, rPA = right pulmonary artery,
lPVs = left pulmonary veins, rPVs = right pulmonary veins, LA = left atrium,
IVC = inferior vena cava.
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CT scans were analyzed by two experienced radiologists who were unaware of
the clinical information and CT technique. When there was a difference of
opinion about CT findings, the final judgment was reached by consensus. To
differentiate fluid in a pericardial sinus and recess from disease, we defined
fluid in the pericardial cavity, using the criteria presented in prior
reports; well-marginated homogenous near-water-attenuation structures (
–10 to 30 H) without a wall or rim of material with higher attenuation
in an expected location of a sinus or recess. We measured attenuation values
to confirm that they were consistent with those of fluid. We recorded the
volume of every pericardial fluid pocket (small, moderate, or large). On
thin-section CT, we also recorded the shape (point, line, band, crescent,
spindle, hemisphere, ovoid, round, triangle, rhomboid, or irregular)
(Fig. 2). The recesses that
were difficult to distinguish from artifacts, occupied by mass lesions, or
adjacent to pleural effusion and consolidation, were excluded from the
analysis. The frequency of the fluid in every recess was statistically
compared between each CT technique using the Mann-Whitney U test. The
volume of the fluid was scored as follows: 0, no fluid; 1, small volume; 2,
moderate volume; 3, large volume. Differences were considered statistically
significant when p values were less than 0.01.
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Fig. 2. —Drawing shows shapes of pericardial sinuses and recesses:
line (1), band (2), spindle (3), crescent (4), point (5), hemisphere (6),
ovoid (7), round (8), triangle (9), rhomboid (10), and irregular (11).
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Results
The frequency and the volume of every pericardial sinus and recess detected
on thin- and thick-section CT are summarized in
Table 1. Large recesses such as
the anterior and posterior superior aortic recesses, left and right pulmonic
recesses, and oblique sinus, which were easily identified using thick-section
CT (7.7–30.4% prevalence), were depicted at 28.7–44.7% prevalence
using thin-section CT. The small recesses such as the left and right pulmonary
venous recesses, inferior aortic recess, and postcaval recess, which were
hardly recognized using thick-section CT (2.5–4.7% prevalence), were
depicted at 10.8–19.8% prevalence using thin-section CT. The prevalence
significantly increased for every sinus and recess depicted on thin-section CT
scans compared with those on thick-section CT scans (p < 0.01)
(Fig. 3A,
3B).
The appearances of pericardial sinuses and recesses are summarized in
Table 2. A small effusion in
the anterior and posterior superior aortic recesses was seen as triangular to
crescentic and crescentic to hemispheric, respectively
(Fig. 4). As the volume of
these recesses increased, their shapes became crescentic to band and ovoid,
respectively. The shape of the inferior aortic recess was observed as linear
to band when small in volume and became a thick band as fluid increased
(Fig. 5). The left pulmonic
recess was linear to crescentic when small in volume
(Fig. 6) and became a thick
band to spindle shape as it increased. The shape of the right pulmonic recess
varied. It was generally observed as rhomboid to a more complex irregular
configuration regardless of its volume and sometimes had a band shape
(Fig. 7). The shape of oblique
sinus was observed as linear to band when small in volume and became a thick
band as it increased (Fig. 3A).
The postcaval recess appeared triangular when small in volume and became
band-shaped when large in volume (Fig.
7). The right pulmonary venous recess often appeared as a small
hemisphere surrounding the pulmonary vein
(Fig. 8) and became round to
band-shaped when large in volume. The left pulmonary venous recess was often
recognized as linear to band-shaped when small in volume and became a thick
band shape when large in volume (Fig.
9).
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Fig. 4. —63-year-old woman with metastatic lung cancer. CT scan
obtained with 3-mm collimation shows moderate volume of fluid (arrow)
in triangular anterior portion of superior aortic recess. Note moderate volume
of fluid (arrowhead) in hemispheric posterior portion of superior
aortic recess.
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Fig. 5. —82-year-old woman with history of aortic aneurysm. CT scan
obtained with 2.5-mm collimation shows small volume of fluid in linear
inferior superior aortic recess (arrow) between ascending aorta and
left atrium.
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Fig. 6. —48-year-old man with bilateral pleural effusions. CT scan
obtained with 2.5-mm collimation shows linear left pulmonic recess
(arrow) between right pulmonary artery and left superior pulmonary
vein.
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Fig. 7. —70-year-old woman with chest pain. CT scan obtained with
2.5-mm collimation shows fluid (arrow) in band-shaped postcaval
recess and moderate volume of fluid in irregular-shaped right pulmonic recess
(arrowhead). Note small lymph node adjacent to oblique sinus
(asterisk).
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Fig. 8. —48-year-old woman with malignant lymphoma. CT scan obtained
with 3-mm collimation shows small volume of fluid (arrow) in
hemispheric right pulmonary venous recess, which is projecting into lung
parenchyma.
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Fig. 9. —65-year-old man with chronic heart failure. CT scan obtained
with 2.5-mm collimation shows fluid in band-shaped left pulmonary venous
recesses (arrow). Note lymph node (asterisk) adjacent to
oblique sinus. E = esophagus.
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Discussion
The pericardial cavity, which lies between the outer fibrous and inner
serous pericardium, has several sinuses and recesses. Cadaveric studies have
described the normal anatomy of these recesses
[6,
8]. Vesely and Cahill
[1] systematically described
and named pericardial sinuses and recesses in their cross-sectional anatomic
study. On CT, these sinuses and recesses are often observed as
near-water-density structures even in patients without significant pericardial
effusion. Initial CT studies using thick-section CT depicted some of these
recesses, especially the larger ones such as the superior aortic recess and
left pulmonic recess, which were seen in approximately 20% of patients.
Protopapas and Westcott [4]
reported that the left pulmonic recess was recognized in 14 (23%) of 61
patients without pericardial effusion. Although our results using
thick-section CT had similar frequencies compared with those of previous
studies, our results had a wider range depending on their size and location.
Large recesses were identified at 7.7–30.4% prevalence, whereas smaller
less-known ones were recognized in less than 5% of the cases.
Recently, multidetector CT and helical CT, which offer faster scanning
times and better image quality, are often being used to evaluate various lung
diseases. Modern CT scanners have contributed to the improvement of the
depiction rate. Kubota et al.
[2] reported that the
transverse sinus was seen at 37–47% prevalence in 133 patients using
helical CT with 3-mm collimation. Our study using thin-section CT also
resulted in a remarkable increase in recognition of pericardial recesses.
Large recesses, which are also easily identified on thick-section CT even when
small in volume, were depicted at almost two to three times greater frequency.
The small recesses, which are hardly recognized on thick-section CT because of
their size (< 1 cm), were depicted at almost a five times greater
frequency. The recesses easily affected by cardiac motion such as the inferior
aortic recess were also recognized at approximately five times greater
frequency. There is great advantage to using thin-section CT in detecting
pericardial sinuses and recesses, especially smaller ones. Our results suggest
that the risk of misdiagnosis of these recesses as an abnormal process may
increase with better visualization of normal recesses.
In our study, the shapes of the pericardial sinuses and recesses varied.
Their shapes are supposed to be related to their location and size. The
anterior superior aortic recess and oblique sinus tended to be linear to
band-shaped because they exist adjacent to the cardiac surface and extend
parallel to the cardiac contour. On the other hand, the recesses surrounded by
the vessels and cardiac structures such as the posterior superior aortic
recess, the bilateral pulmonic recesses, and the inferior aortic recess tended
to have various appearances depending on the gap formed by surrounding
structures. The smaller recesses such as the right pulmonary venous recess and
the postcaval recess tended to be triangular to round due to their small
size.
There is a potential to misdiagnose these normal recesses as abnormal
processes. A large recess is easily recognized and is unlikely to present a
diagnostic problem, but the crescentic fluid in the anterior superior and
inferior aortic recesses can mimic aortic dissection
[11,
12]
(Fig. 10). Chiles et al.
[11] reported that the
characteristic shape and location of the recess may prevent an erroneous
diagnosis of type A aortic dissection. The band- or irregular-shaped fluid in
the anterior superior aortic recess sometimes could be confused with a
mediastinal mass, pericardial cysts, thymic cysts, or the thymus
[13,
14]. Winer-Muram and Gold
[14] reported that valuable
signs are the lack of enhancement after contrast administration. Moreover,
various mediastinal and hilar lymph nodes lie adjacent to every pericardial
recess [15]. For example,
paraaortic lymph nodes lie near the anterior superior aortic recess; lower
paratracheal lymph nodes, near the posterior superior aortic recess; subaortic
lymph nodes, near the left pulmonic recess; hilar and inferior mediastinal
lymph nodes, near the right pulmonic recess; paraesophageal and inferior
mediastinal lymph nodes, near the oblique sinus; azygous and hilar lymph
nodes, near the postcaval recess; and lower lobar lymph nodes and pulmonary
ligament nodes, near bilateral pulmonary venous recesses. Although most lymph
nodes appear denser than most fluid collections on contrast-enhanced CT, it
may still be difficult to distinguish lymph nodes from fluid collections in
ovoid or round recesses. Above all, the posterior superior aortic recess is
often separated from the ascending aorta by a fat plane and becomes ovoid to
round [5]. The right pulmonary
venous recess also tends to become round, projecting into the lung parenchyma
(Fig. 11). Other recesses may
even become ovoid or round when collecting a moderate to large volume of
fluid. Furthermore, lymph nodes can appear to have near-water-density necrotic
centers. To distinguish some lymph nodes from pericardial fluid, we believe
the finding of an enhanced rim may be helpful in establishing the diagnosis of
necrotic isodense lymph nodes
[2].
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Fig. 10. —67-year-old woman with pleural effusion. CT scan obtained
with 2.5-mm collimation shows crescentic anterior superior aortic recesses
(asterisk) that mimics aortic dissection. Fluid attenuation was 21.1
H.
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Fig. 11. —50-year-old woman with bilateral lower lobe pulmonary
embolism. CT scan obtained with 3-mm collimation shows fluid in round right
pulmonary venous recess projecting into lung parenchyma, which mimics lower
lobar lymph node (arrow). Fluid attenuation was 26.7 H.
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Although thin-section CT improved the depiction rate of every pericardial
sinus and recess, it has some limiting factors. Our protocol for thin-section
CT was based on the clinical suspicion of pulmonary embolism. Therefore, bolus
injection at a high rate resulted in a severe streak artifact from contrast
material in the superior vena cava. The postcaval recess is small, and it is
the recess most affected by this artifact, which was difficult to evaluate in
many cases. We could assess only 63.8% of cases when evaluating the postcaval
recess using thin-section CT, whereas thick-section CT at a slower injection
rate allowed assessment of 82.3% of cases. Longer scanning delays or slower
injection rates may help to prevent this artifact.
In addition, because pericardial effusion has been reported to influence
the visualization of the pericardial sinuses and recesses, we excluded the
cases with pericardial effusion
[8]. However, patients with a
suspected pulmonary embolism might have a greater prevalence of right cardiac
failure with consequent increased fluid in the pericardial recesses.
Levy-Ravetch et al. [8]
reported that pericardial effusions were associated with more frequent
visualization of pericardial recesses using 10-mm-thick CT slices. Although
these researchers did not mention shape, every recess must no longer have
appeared loculated but instead had become a thick band because every recess
communicates with the others. When the fluid is distributed to the entire
pericardial sac, the connection between every recess might be more easily
identified.
Cardiac motion also influences the visualization of the pericardial sinuses
and recesses and sometimes reduces image quality. The superior aortic recess
and left pulmonic recess are not surrounded by mobile structures and are
seldom affected by cardiac motion, whereas the inferior aortic recess, left
pulmonary venous recess, and right pulmonic recess abutting the left atrium or
ventricle are often blurred because of cardiac motion. Electron beam CT
offered better image quality that was less affected by cardiac motion
[9]. Groell et al.
[10] reported that the
depiction rate of recesses ranged from 23% to 81% of 100 patients without
pericardial effusion, using ECG-triggered electron beam CT. However, electron
beam CT has not become a commonly available technique. For better image
quality with fewer artifacts, ECG-triggered thin-section CT is preferable.
In conclusion, thin-section CT provides improved visualization of
pericardial sinuses and recesses. Fluid collections in these spaces, including
less well-known spaces, can be observed more frequently on thin-section CT
scans than on thick-section CT scans, even in cases without pericardial
effusions. The results were not particularly unexpected; however, an
understanding of the location and various appearances of fluid collections
helps the radiologist avoid a misdiagnosis of lymphadenopathy or other
mediastinal or hilar disease.
References
- Vesely TM, Cahill DR. Cross-sectional anatomy of the pericardial
sinuses, recesses and adjacent structures. Surg Radiol
Anat 1986;8:221
–227[Medline]
- Kubota H, Sato C, Ohgushi M, Haku T, Sasaki K. Fluid collection in
the pericardial sinuses and recesses. Invest Radiol1996; 31:603
–610[Medline]
- Olson MC, Harold VP, McDonald V, Wisneiwski R, Moncada R. Computed
tomography and magnetic resonance imaging of the pericardium.
RadioGraphics1989; 9:633
–649[Abstract]
- Protopapas Z, Westcott JL. Left pulmonic recess of the pericardium:
findings at CT and MR imaging. Radiology1995; 196:85
–88[Abstract/Free Full Text]
- Duvernoy O, Larsson SG, Thuren J, Rauschning W. Epicardial fat
causing pitfalls in CT and MR imaging of the pericardium. Acta
Radiol 1992;33:1
–5[Medline]
- Aronberg DJ, Peterson RR, Glazer HS, Sagel SS. The superior sinus
of the pericardium: CT appearance. Radiology1984; 153:489
–492[Abstract/Free Full Text]
- Choi YW, McAdams HP, Jeon SC, Seo HS, Hahm CK. The
"high-riding" superior pericardial recess: CT findings.
AJR 2000;175:1025
–1028[Abstract/Free Full Text]
- Levy-Ravetch M, Auh YH, Rubenstein WA, Whalen JP, Kazam E. CT of
the pericardial recesses. AJR1985; 144:707
–714[Abstract/Free Full Text]
- Budoff MJ, Lu B, Mao S, et al. Evaluation of fluid collection in
the pericardial sinuses and recesses: noncontrast-enhanced electron beam
tomography. Invest Radiol2000; 35:359
–365[Medline]
- Groell R, Schaffler GJ, Rienmueller R. Pericardial sinuses and
recesses: findings at electrocardiographically triggered electron-beam CT.
Radiology1999; 212:69
–73[Abstract/Free Full Text]
- Chiles C, Baker ME, Silverman PM. Superior pericardial recess
simulating aortic dissection on computed tomography. J Comput
Assist Tomogr 1986;10:421
–423[Medline]
- Batra P, Bigoni B, Manning J, et al. Pitfalls in the diagnosis of
thoracic aortic dissection at CT angiography.
RadioGraphics2000; 20:309
–320[Abstract/Free Full Text]
- Shin MS, Jolles PR, Ho KJ. CT evaluation of distended pericardial
recess presenting as a mediastinal mass. J Comput Assist
Tomogr 1986;10:860
–862[Medline]
- Winer-Muram HT, Gold RE. Effusion in the superior pericardial
recess simulating a mediastinal mass. AJR1990; 154:69
–71[Free Full Text]
- Ko JP, Drucker EA, Shepard JA, et al. CT depiction of regional
nodal stations for lung cancer staging. AJR2000; 174:775
–782[Free Full Text]
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Abstract
Introduction
