Severino Gianpiero
A. Davolio P. Alberti,
Hydatid
Marani, MD
MD
terms:
er, cysts, 761.2083 sites
Radiology
Echinococcosis,
761.2083 #{149} Liven,
1990;
C. Canossi, G. Monni, MD
Disease:
Fifteen patients with hydatidosis, 13 with hepatic echinococcosis and two with isolated lesions of the spleen and the shoulder, were examined with magnetic resonance (MR) imaging. Of the 13 patients with hepatic hydatidosis, four had secondary peritoneal lesions, and one also had involvement of the dorsal spine. The presence of a hypointense rim and a multiloculated or multicystic appearance are distinctive features. When evaluating the viability of hydatid cysts the authors found that MR imaging findings were not particularly valuable, as the MR imaging signs (daughter cysts and detachment of the membranes) are rare and are also evident at computed tomography and ultrasound examinations. T2 measurements were not useful due to the wide range of values obtained. Despite these limitations, MR imaging is still an important technique in the study of echinococcosis to depict the presence of a rim as a characteristic sign and to obtain a complete anatomic evaluation. Index
#{149} Giancarlo
#{149}Sebastiano
761.2083
echinococcosis, MR studies, 761.1214
#{149} Para-
175:701-706
H
disease
YDATID
A. Nicoli, M. Casolo, MD
Mediterranean
is very
rare
in
countries.
The
Unitin grow-
ing use of magnetic resonance (MR) imaging in the diagnosis of mass lesions of the liver prompted us to look for characteristic signs to distinguish hydatid disease from other nonparasitic
focal
lesions
and,
if possible,
to
define differential features of viable and sterile cysts. In cases of extrahepatic spread, MR imaging is very useful given its wide field of view and ability to include in a single section both the upper and the lower abdomen, considerably reducing examination time. To date, the MR imaging aspects have been described in only 15 cases of echinococcal cysts of the liver (35) and
in a few
cases
of extrahepatic
hydatidosis (6-8), mainly with units of medium to low field strength (0.i5-0.5 T); we therefore wanted to evaluate the use of a i.5-T unit.
ic comparison between results obtained with these techniques. All examinations were carried out on a superconductive unit at 1.5 T (GE Medical Systems,
AND
We examined
METHODS
15 patients,
13 with
echinococcal lated splenic
liver disease, involvement,
one with and one
echinococcal
disease
isowith
of the left scapula
and the soft tissues of the shoulder. In the latter case a hydatid cyst had been removed from the right lung 15 years earlien. Of the 13 patients with liver hydatid disease, five patients also had extrahepatfour
had
penitoneal
localiza-
tions, and one had involvement of the dorsal spine. The diagnosis of hydatid disease was based on clinical-nadiologic and anamnestic data (six patients had relapse on had residual lesions that were treated in the past). The histopathologic reports from surgery were available for nine patients. In nine patients computed tomography (CT) was also performed, and in six patients ultrasound (US) examination was performed. Because of the small number of patients who underwent both CT and US,
it was
impossible
to make
a systemat-
Milwaukee)
ty, and images
with
T2 weighting. were acquired
(SE) 400-800/20
Ti,
Axial with
spin-densi-
Ti-weighted a spin-echo
sequence
(repetition
time msec/echo time msec) with two tations. Axial spin-density and T2weighted images were obtained with
second
SE sequence
tion time asymmetric spectively
with
a long
excia
repeti-
(1,500-2,500 msec) and two echoes at 20 and 80 msec, re(two excitations). In some cases
we also used gradient-echo
sagittal and coronal views and first-order flow-com-
or
pensation sequences, the latter to evaluate the condition of the portosystemic cmculation. In the case of hydatid liven cysts
we methodically the spins outside to minimize We always
(reordered The field
used presaturation of the volume of interest
phase artifacts used respiratory
phase-encoding of view varied
of the vessels. compensation
techniques). between 32 and
40 cm, with section thicknesses of mm. In medium or large lesions (4 more) we measured the T2 on two at 20 and 80 msec. A retrospective evaluation of the sults
PATIENTS
MD
Study’
the United States and the ed Kingdom (i,2) but is frequent
ic spread;
1 From the Institute of Radiology (S.A.D.M., CCC.) and the Department of Surgery (S.C.M., P.M.C.), University of Modena, Modena, Italy, and the Department of Radiology and Nuclear Medicine (FAN., C.P.A.), Ospedale S Maria Nuova, Reggio Emilia, Italy. Received October 1 1, 1989; revision requested December 13; revision received February 5, 1990; accepted February 21. Address reprint requests to S.A.D.M., C so Adriano, 1, 41 100, Modena, Italy. RSNA, 1990
#{149} Franco
MR Imaging
#{149} Liv-
#{149} Liver,
MD #{149} Paolo
was
made
in
concert
by
authors who are well skilled imaging. In a case with widespread hydatidosis,
imaging
we
also
performed
examination
of part
5-10 cm on
echoes
three
reof the
in body
MR
peritoneal an
of the
MR
surgi-
cal specimen.
RESULTS Hepatic
Hydatidosis
In 13 patients, 20 lesions were discovered (one patient with four cysts, two patients with three cysts, and 10 patients with one); i7 of these were found on the right lobe and three on the left lobe. Two patients who had undergone surgery, one of whom had a postsurgical recurrence, also had some of the calcific pericyst re-
Abbreviation:
SE
=
spin
echo.
701
maining close to the vena cava (nesidual pseudocyst). Ten of the cysts had a diameter larger than 4 cm. The bordens were smooth in seven lesions and somewhat irregular in the others, with a multiloculated on multicystic aspect in seven lesions. The larger lesions without daughter cysts (a sign of viability) and without detachment of the membranes lesions
were with
most often seen smooth borders
as cystic (Fig 1).
A low-intensity rim with a maximum thickness of 4-5 mm was present in 19 of the 20 lesions, and
a.
this could be considered a characteristic sign when comparing these lesions with nonparasitic epithelial cysts. A more or less continuous rim
was much more weighted images ed or spin-density calcific rim was nadiognaphs
or CT
scans
(as
position
in relation direction,
possibility
of
of a chemical-shift
effect.
other
authors
rim
could
(4), nepre-
of the hydatid membrane rich in the host that is of
T2. The penicyst earlier stage than
proper native which
of
to the frequencyexcluded any
In agreement with we believe that the sent the outer layer cyst, the penicyst, a collagen created by short at an
in six
sign was also images (Fig
circumferential
the rim, encoding
1. MR images of a noncalcified hydatid cyst of the right lobe. (a) Axial SE 400/20 image depicts a large cystic lesion of the right lobe with low signal intensity, isointense with the spleen. (b) Axial SE 1,500/80 image of the cyst shows a high-intensity inhomogeneous signal and a hypointense rim that is more evident posteriorly (arrows).
evident on T2than on Ti-weightimages. When a already seen on plain
our cases), then the rim evident on Ti-weighted 2). The
b.
Figure
often the
calcifies other two
a.
b.
Figure 2. (b) images,
Calcified the
signal intensity mogeneous on
hydatid
cyst demonstrates of the lesion the 12-weighted
cyst of the right
lobe.
a hypointense, is medium to low image.
On axial
SE 550/20
continuous rim on the Ti-weighted
(a) and
of uneven image
1,500/80
thickness. and high
and
The ho-
layers of the parasite (germiand intermediate layer), are both very thin (9), and this
further
shortens
the
T2.
The signal intensity was homogeneous in five lesions (25%) and was the same as that of the biliary cysts except for the presence of the rim. The signal intensity was inhomogeneous in the remaining 15 lesions, especially
lated
in those
with
or multicystic
ticystic appearance ity of the borders to medical therapy
a multilocu-
aspect. and indicate (Fig
The
mul-
the
irregulara response 3). When
evaluating the signal intensity, we used the surrounding hepatic parenchyma as a reference in the qualitative evaluation of signal intensity on the images. In 100% of cases the signal
with
of the
lesions
Ti weighting
with T2 weighting. images there were
with
75%
of the
was
hypointense
and
hypermntense
On some
spin-density differences,
lesions
702
an average Radiology
#{149}
b.
Figure
3.
MR images
of a vital
cyst
after
medical
therapy
and
membranes. lobe with
Axial SE 1,500/20 (a) and 1,500/80 (b) images an exophytic proliferation on the anteromedial
weighted
image
membranes to medical
(b) the hypointense
are evident therapy.
(straight
rim arrow,
partial
show border
(open
arrow,
b) and
b). The
latter
is a sign
detachment
a hydatid (curved
the partial that
the
of the
cyst of the left arrow). On 12-
detachment parasite
of the
is responding
appearing
hypointense and 25% appearing isointense compared with the normal surrounding panenchyma. The T2 measurements of nine large lesions varied from 1 1 1 to 281 msec,
with
a.
of 173 msec,
which
is almost
the gical specimen. The presence
same
easily
ascertained
one lobe
case involved of the liver
as those
of the
sun-
involved
of daughter in
two
cysts
cases
was
only;
a cyst of the left (Fig 4) and the other
widespread
pelvic
hydati-
assessof daughter cysts of the liven, a sign of viability, is not reliable due to respiration-induced image blurring in the upper abdomen. It is also hindosis
(Fig
5).
The
MR
imaging
ment
June
1990
a. Figure 1,500/80
b. 4.
MR images (b)
images,
of a left lobe the
signal
cyst with
intensity
of the
daughter
cysts.
cyst
is inhomogeneous.
On axial
SE 1,500/20 At lapanotomy
(a) and the
cyst was almost completely full of daughter cysts that on spin-density image (a) have hypointense signal when compared with that of the hydatid matrix. On 12-weighted image (b) they have high signal intensity with some thin, inner, hypointense septations. The rim appears thicker posteriorly (arrow) with an exogeneous proliferation on its right anterior borden (arrowhead).
dened by the small number of cases with histopathologically verified viable cysts (only three patients) caused by the predominance of patients in relapse or with primitive or residual lesions who had already undergone medical treatment. With sterile cysts or acephalocysts, we could see the detachment of the proper membrane from the penicyst. If thick calcifications are present in the proper membrane, it is possible to see the MR imaging equivalent of the water lily sign (Fig 6). MR imaging, with its wide field of view, was very useful in the followup of residual lesions, of any possible recurrence (Fig 7), and of postsurgical results (Figs 7, 8). In most cases the pericyst is not completely nemoved during surgery because of its proximity to vital structures such as the vena cava. The residual cavity fills with blood cystlike lesions
or bile, that are
producing often multi-
loculated, with irregular bonders and a hypomntense rim that is thicker than that of the parasite due to healing factors (iO). The signal intensity of these lesions was high with T2 weighting and low with Ti weighting (Figs 7, 8). In this case the differential diagnosis of a possible recurnence is difficult. If the cavity is packed with omental fat, we should have seen, at least in the first few months following surgery, a high signal intensity also with Ti weighting (no such case arose in our study).
a.
b.
Extrahepatic
Hydatidosis
Extrahepatic
echinococcosis
has
many
different appearances. It may occur as isolated peritoneal lesions with the same characteristics as the hepatic cysts. It may demonstrate massive penitoneal spread (Fig 5), osseous localizations with multiloculated cysts (cyst inside a cyst), or polycystic aspects (Figs 9, 10). Multiple lesions are the most common findings. In the two observed cases of bone lesions,
several
The quent
discovery of a rim is also in extrahepatic localizations
(in d.
C.
Figure
5. MR images of massive peritoneal spread with several daughter cysts. (a) Axial SE 800/20 image depicts many hydatid cysts in the pelvis due to an open rupture into the peritoneum. The two cysts situated posteriorly (arrows) present several daughter cysts; their signal intensity is lower than that of intracystic fluid. (b) On axial SE 2,000/80 image the daughter cysts (arrows) tend to fade into the intracystic fluid as both are of high signal intensity. The anterior cyst has a multiloculated appearance (arrowheads, a and b) caused by the presence of several internal septa. (c, d) MR imaging examination of the surgical specimen. On SE 500/20 (c) and 2,000/80 (d) images, the rim is well represented even on the small daughter cysts. Some of these (arrows, c and d) have a lower signal intensity than othens on T2-weighted image also because of a smaller fluid content.
Volume
175
Number
#{149}
3
five
cysts
of seven
were
present.
cases),
while
frethe
characteristics of the signal are the same as those of hepatic lesions. T2 measurements registered a wide range of values, from 80 to 800 msec. When daughter cysts are present, they are seen as endogenous proliferations
minative
more
on less
layer,
with
joined
to the
ger-
a hypointense
signal compared to that of the intracystic fluid with Ti weighting and spin-density weighting. On T2-
Radiology
703
#{149}
weighted images the signal intensity of the daughter cysts was higher and was confused with that of the hydatid matrix (Fig 5). In cases of massive peritoneal spread, MR imaging examination of part of the surgical specimen (Fig 5c, 5d) rim
helped confirm that was easily
the seen
presence of a even in cysts
with a diameter smaller than 2 cm. Furthermore, in some of these cysts there was a lower signal intensity, on T2-weighted images, maybe due to a lower fluid content. These should be the least vital cysts. In extrahepatic hydatidosis differential diagnosis is not a problem because we are dealing with secondary localizations of an already necognized disease. In these cases the usefulness of MR imaging lays in the precise definition of anatomic relationships due to the multiplanar capabilities and the excellent contrast resolution for soft tissues.
b.
a. Figure axial
6.
MR images
SE 1,700/20
of a sterile
image
is seen
on the medial
proper
membranes
the
side,
cyst
with
situated
hydatid
cyst with detachment a bilobate appearance,
shows
the pericyst
internally
(open
located
more
arrows).
(b)
and
of the membranes. a hypointense,
externally Axial
(solid
arrows)
SE 1,700/80
MR imaging equivalent of the water lily sign: The proper membrane pointense because of calcification and freely floats on the intracystic intensity. The calcific pericyst is seen externally (solid arrows).
(a) On double rim
image
and
the
shows
the
(open arrows) is hyfluid with a high signal
DISCUSSION In hepatic and extrahepatic hydatidosis, the two techniques used currently, CT and US (iO-i2), are sufficient to obtain an anatomic evaluation. When results of serologic tests are positive, there are no problems of differential diagnosis with other types of nonparasitic cysts. When no characteristic signs of hydatidosis (ie, daughter cysts, hydatid sand,
or calcified
membranes)
are
present, the differential diagnosis can be facilitated with MR imaging, which almost always shows the typical findings of the presence of a rim or a multiloculated on multicystic featune. In the assessment of the rim, MR imaging appears more reliable than CT, as the latter shows the rim in a limited number of cases (i i). Since the rim is almost always found with
a. Figure
b. 7.
MR images
of a relapsing calcified cyst (no (a) and 2,000/80 (b) images, a cyst of the right anterior ty is inhomogeneous; the lower part, corresponding to generated material (*), has medium signal intensity on
nal intensity on 12-weighted the proper membranes that cially on 12-weighted all sequences (solid
with high,
vena
images, arrows).
the pseudocyst. inhomogeneous
cava
is compressed
On axial SE 700/20 The signal intensiand/or caseous de-
Ti-weighted images (a) and high sigimages (b). The upper part, consistent with calcified debris of have detached from the pericyst, has low signal intensity espewith Around
some the
The pseudocyst signal
histologic proof). segment is shown. the hydatid sand
has low signal
intensity
to some
small hyperintense vena cava there
extent
on
12-weighted
(open
are
intensity images
areas. some
The rim fragments
on Ti-weighted (arrowhead).
is evident with of the pericyst
images The
and
inferior
arrow).
Figure 8. Long-term postsurgical results. (a) On axial SE 500/20 image there is a zone of low signal intensity at the porta hepatis with unclear borders, possibly due to a perihilar fibrosis (open arrows). The intrahepatic portal vessels (arrowheads) are stretched and slightly enlarged and draw together toward this area of fibrosis. Portal hypertension is confirmed by the large spleen.
(b)
Axial
SE 2,500/80
image
ual, postsungical cavity sity near the vena cava ment of the pericyst intensity. The fibrous, isointense or slightly
pared with images.
704
the
Radiology
#{149}
normal
shows
of high (arrow).
maintains perihilar
the
resid-
signal intenThe fraglow signal tissue is
hyperintense comliver on 12-weighted a.
b.
June
1990
b.
a.
Figure 9. MR images of a spinal hydatid lesion (1-6 to 1-7) protruding into the right paraspinal gutter. Axial SE 1,700/20 (a) and 1,700/80 (b) images show the hydatid localization involving the vertebral body, the posterior arch, and the paravertebral tissues (arrows). The outlines are irregular and poorly defined. The signal is inhomogeneous, of medium intensity on spin-density weighted images (a) and of high intensity on 12-weighted images (b). (c) Sagittal SE 650/20 image does not show any compression of the medulla but only a slight reduction of the anterior subdunal space.
parenchymal hematoma also shows a double rim (16); the peripheral one is hypomntense and is caused by hemosiderin, and the inner one is hyperintense on Ti-weighted images due to methemoglobin, with a central hypointense core consisting of deoxyhemoglobin. The complete oxidative denatunation of deoxyhemoglobin into methemoglobin that follows removes any doubt regarding the diagnosis.
In all
pearance sufficient specific agnosis
of these
situations
the
ap-
of the rim is almost always to resolve the problem; elements for differential dialso exist. For example, fatty
degeneration
and
vascular
invasion
indicate hepatocarcinoma (13). With other mass lesions of the liver such as metastases, simple cysts, hemangiomas, and focal nodular hyperplasia (17,18), rim images have never been described, to our knowledge. At present MR imaging seems to be a.
b.
less
Figure 10. MR images of a shoulder lesion. On coronal SE 600/20 (a) and SE 2,000/80 (b) images the scapula and the soft tissues of the left shoulder are completely substituted several cysts of various sizes. The signal is inhomogeneous, of medium to low intensity Ti-weighted images and high intensity on 12-weighted images.
by
on
ble,
hydatid nosis
cysts, includes
the
differential
other
capsulated
diagmass
lesions of the liver, such as hepatocarcinoma, amebic abscess, and, less often, mntraparenchymal hematoma and hepatic adenoma. With hepatocellular carcinoma, the rim was found with a frequency ranging from 24% to 42% in the case studies in the literature (13,14). It is never as thick and continuous as it appears with hydatid cysts. Also with Volume
175
Number
#{149}
3
hydatid cysts, we have penitumoral edematous signal intensity surrounding sule with a double ring T2 weighting (14). The
seen ing
in hepatic stage,
after
liver abscess one concentric nal
intensity
ferent capsule.
(i5) and
from After
that
never zone
seen a of high the cappattern with rim is seldom
adenoma.
In the
treatment,
the
amebic
is seen as more ring with varying a signal
of the at least
pattern
healthan sigdif-
hydatid
cyst
3 weeks,
intra-
helpful
when
evaluating
vitality
on the effects of medical therapy. The MR imaging criteria used are the same as those used with CT and US: A smooth-bordered lesion with daughter cysts is most probably viawhile
tachment regular
capsular
calcifications,
of the membranes, edges are signs that
site
is succumbing.
are
difficult
Daughter
to see at MR
and the calcified at CT. Compared ing seems more
de-
and inthe paracysts
imaging,
rim is shown better with CT, MR imaguseful and reliable
when looking for the irregularities the rim bonders with considerable differences in thickness, probably signs of a partial membranes.
detachment
Radiology
of
of the
705
#{149}
Although, in theory, a reduction of the water content of the cyst is connected to a reduction in biological exchange between the parasite and
2.
host (9), not show
3.
the T2 measurements significant differences
did
its
high
signal-to-noise
capability does not this
more slight
ratio
Barley
and
but
detailed diagnostic
it does
anatomic gain.
provide
view
pont
of
611 cases from 1967; 99:660-667.
706
Radiology
#{149}
A.
1 12 cases
the
Iran
United
disease: and
States.
a review
AJR
1983;
24:A996.
Morris
DL,
epidemiology
England
F,
12.
diagof hyda-
and
Wales.
Gut
13.
J, Cregson
Buckley
R, Worresonance imagClin Radiol 1987;
Magnetic disease.
14.
338:141-144.
5.
Lupetin
6.
tune of hydatid cyst: MR findings. 1988; 151:491-492. Mikhael MA, Cinic IS, Tarkington
AR,
imaging
7.
in
Dash
S. Viale
and
magnetic
hydatidosis.
N.
spinal
ME, Glazer disease of 1987; 12:39-
Intrahepatic
echinococcosis.
put Assist Tornogn Pau A, Sirnonetti tas
CL.
JA. MR J Corn-
1985; 9:398-400. C, Tortori-Donati Computed
resonance Sung
rup-
1987;
in spinal 27:365-
Desnos
9.
Polyvisceral echinococcosis with cardiac involvement imaged by two-dimensional echocardiognaphy, computed tomography and nuclear magnetic resonance imaging. Am J Cardiol 1987; 59:383-384. Sommaniva V. L’idatidosi epatica. Arch Atti Soc It Chir 1984; 1:223-371. Kalavidouris A, Gouliamos A, Demou L, Vassilopoulos P. Vlachos L, Papavassiliou K. Postsurgical evaluation of hydatid disease with CT: diagnostic pitfalls. J Comput
a
reof
Assist
1 1.
Tomogr
Brochet
E, Cristofini
1984;
P. et al.
Niron EA, Ozer H. Ultrasound appearance of liver hydatid disease. Br J Radiol 1981; 54:335-338. Rummeny E, Weissleder R, Stark DD, et al. Primary liver tumors: diagnosis by MR imaging. AJR 1989; 152:63-72. Itoh K, Nishimura K, Togashi K, et al. Hepatocellular carcinoma: MR imaging. Radiology 1987; 164:21-25. Elizondo C, Weissleder R, Stark DD, et al. Amebic liver abscess: diagnosis and treatment evaluation with MR imaging. Radiology 1987; 165:795-800. Hahn PF, Saini 5, Stark DD, Papanicolaou N,
17.
P. Tur-
369. M,
16.
tomography
imaging
Neunol
15.
AJR
8.
U
Echinoccus from
in
Pritchard
Serological
Hoff FL, Aisen AM, Walden CM. MR imaging in hydatid the liver. Castrointest Radiol 42.
10.
Bonakdarpoun
current
disease
MJ,
DL.
4.
References 1.
Clarkson
Morris
thington BS. ing in hydatid
the
with
and
tid
to obtain thinner sections, modify the possibilities of
technique,
MF,
KW,
nosis
be-
tween fertile and sterile cysts, and the range of values was too wide to be of use. To conclude, MR imaging is of value in the study of hydatid disease. In hepatic localizations it can be used to determine the presence of a characteristic sign such as the rim, and in extrahepatic lesions it enables the evaluation of anatomic relationships. Compared with previous results obtained with MR imaging units of low to medium field strength, we believe that the use of a i.5-T unit, with
Stallbaumer
18.
Fenrucci
JT.
Intnaabdominal
hemato-
ma: the concentric ring sign in MR imaging. AJR 1987; 148:115-119. Wittenberg J, Stark DD, Forman BH, et al. Differentiation of hepatic metastases from hepatic hemangioma and cysts by using MR imaging. AJR 1988; 151:79-84. Mattison CR, Clazer CM, Quint LE, Francis IR, Bree LR, Ensminger WD. MR imaging of hepatic focal nodular hyperplasia: characterisation and distinction from primary malignant hepatic tumors. AJR 1987; 148:711-715.
8:1114-1119.
Pandolfo I, Blandino C, Scribano E, Longo M, Certo A, Chinico C. CT findings in hepatic involvement by Echinococcus granulosus. J Comput Assist Tomogr 1984; 8:839845.
June
1990
A. Davolio P. Alberti,
Hydatid
Marani, MD
MD
terms:
er, cysts, 761.2083 sites
Radiology
Echinococcosis,
761.2083 #{149} Liven,
1990;
C. Canossi, G. Monni, MD
Disease:
Fifteen patients with hydatidosis, 13 with hepatic echinococcosis and two with isolated lesions of the spleen and the shoulder, were examined with magnetic resonance (MR) imaging. Of the 13 patients with hepatic hydatidosis, four had secondary peritoneal lesions, and one also had involvement of the dorsal spine. The presence of a hypointense rim and a multiloculated or multicystic appearance are distinctive features. When evaluating the viability of hydatid cysts the authors found that MR imaging findings were not particularly valuable, as the MR imaging signs (daughter cysts and detachment of the membranes) are rare and are also evident at computed tomography and ultrasound examinations. T2 measurements were not useful due to the wide range of values obtained. Despite these limitations, MR imaging is still an important technique in the study of echinococcosis to depict the presence of a rim as a characteristic sign and to obtain a complete anatomic evaluation. Index
#{149} Giancarlo
#{149}Sebastiano
761.2083
echinococcosis, MR studies, 761.1214
#{149} Para-
175:701-706
H
disease
YDATID
A. Nicoli, M. Casolo, MD
Mediterranean
is very
rare
in
countries.
The
Unitin grow-
ing use of magnetic resonance (MR) imaging in the diagnosis of mass lesions of the liver prompted us to look for characteristic signs to distinguish hydatid disease from other nonparasitic
focal
lesions
and,
if possible,
to
define differential features of viable and sterile cysts. In cases of extrahepatic spread, MR imaging is very useful given its wide field of view and ability to include in a single section both the upper and the lower abdomen, considerably reducing examination time. To date, the MR imaging aspects have been described in only 15 cases of echinococcal cysts of the liver (35) and
in a few
cases
of extrahepatic
hydatidosis (6-8), mainly with units of medium to low field strength (0.i5-0.5 T); we therefore wanted to evaluate the use of a i.5-T unit.
ic comparison between results obtained with these techniques. All examinations were carried out on a superconductive unit at 1.5 T (GE Medical Systems,
AND
We examined
METHODS
15 patients,
13 with
echinococcal lated splenic
liver disease, involvement,
one with and one
echinococcal
disease
isowith
of the left scapula
and the soft tissues of the shoulder. In the latter case a hydatid cyst had been removed from the right lung 15 years earlien. Of the 13 patients with liver hydatid disease, five patients also had extrahepatfour
had
penitoneal
localiza-
tions, and one had involvement of the dorsal spine. The diagnosis of hydatid disease was based on clinical-nadiologic and anamnestic data (six patients had relapse on had residual lesions that were treated in the past). The histopathologic reports from surgery were available for nine patients. In nine patients computed tomography (CT) was also performed, and in six patients ultrasound (US) examination was performed. Because of the small number of patients who underwent both CT and US,
it was
impossible
to make
a systemat-
Milwaukee)
ty, and images
with
T2 weighting. were acquired
(SE) 400-800/20
Ti,
Axial with
spin-densi-
Ti-weighted a spin-echo
sequence
(repetition
time msec/echo time msec) with two tations. Axial spin-density and T2weighted images were obtained with
second
SE sequence
tion time asymmetric spectively
with
a long
excia
repeti-
(1,500-2,500 msec) and two echoes at 20 and 80 msec, re(two excitations). In some cases
we also used gradient-echo
sagittal and coronal views and first-order flow-com-
or
pensation sequences, the latter to evaluate the condition of the portosystemic cmculation. In the case of hydatid liven cysts
we methodically the spins outside to minimize We always
(reordered The field
used presaturation of the volume of interest
phase artifacts used respiratory
phase-encoding of view varied
of the vessels. compensation
techniques). between 32 and
40 cm, with section thicknesses of mm. In medium or large lesions (4 more) we measured the T2 on two at 20 and 80 msec. A retrospective evaluation of the sults
PATIENTS
MD
Study’
the United States and the ed Kingdom (i,2) but is frequent
ic spread;
1 From the Institute of Radiology (S.A.D.M., CCC.) and the Department of Surgery (S.C.M., P.M.C.), University of Modena, Modena, Italy, and the Department of Radiology and Nuclear Medicine (FAN., C.P.A.), Ospedale S Maria Nuova, Reggio Emilia, Italy. Received October 1 1, 1989; revision requested December 13; revision received February 5, 1990; accepted February 21. Address reprint requests to S.A.D.M., C so Adriano, 1, 41 100, Modena, Italy. RSNA, 1990
#{149} Franco
MR Imaging
#{149} Liv-
#{149} Liver,
MD #{149} Paolo
was
made
in
concert
by
authors who are well skilled imaging. In a case with widespread hydatidosis,
imaging
we
also
performed
examination
of part
5-10 cm on
echoes
three
reof the
in body
MR
peritoneal an
of the
MR
surgi-
cal specimen.
RESULTS Hepatic
Hydatidosis
In 13 patients, 20 lesions were discovered (one patient with four cysts, two patients with three cysts, and 10 patients with one); i7 of these were found on the right lobe and three on the left lobe. Two patients who had undergone surgery, one of whom had a postsurgical recurrence, also had some of the calcific pericyst re-
Abbreviation:
SE
=
spin
echo.
701
maining close to the vena cava (nesidual pseudocyst). Ten of the cysts had a diameter larger than 4 cm. The bordens were smooth in seven lesions and somewhat irregular in the others, with a multiloculated on multicystic aspect in seven lesions. The larger lesions without daughter cysts (a sign of viability) and without detachment of the membranes lesions
were with
most often seen smooth borders
as cystic (Fig 1).
A low-intensity rim with a maximum thickness of 4-5 mm was present in 19 of the 20 lesions, and
a.
this could be considered a characteristic sign when comparing these lesions with nonparasitic epithelial cysts. A more or less continuous rim
was much more weighted images ed or spin-density calcific rim was nadiognaphs
or CT
scans
(as
position
in relation direction,
possibility
of
of a chemical-shift
effect.
other
authors
rim
could
(4), nepre-
of the hydatid membrane rich in the host that is of
T2. The penicyst earlier stage than
proper native which
of
to the frequencyexcluded any
In agreement with we believe that the sent the outer layer cyst, the penicyst, a collagen created by short at an
in six
sign was also images (Fig
circumferential
the rim, encoding
1. MR images of a noncalcified hydatid cyst of the right lobe. (a) Axial SE 400/20 image depicts a large cystic lesion of the right lobe with low signal intensity, isointense with the spleen. (b) Axial SE 1,500/80 image of the cyst shows a high-intensity inhomogeneous signal and a hypointense rim that is more evident posteriorly (arrows).
evident on T2than on Ti-weightimages. When a already seen on plain
our cases), then the rim evident on Ti-weighted 2). The
b.
Figure
often the
calcifies other two
a.
b.
Figure 2. (b) images,
Calcified the
signal intensity mogeneous on
hydatid
cyst demonstrates of the lesion the 12-weighted
cyst of the right
lobe.
a hypointense, is medium to low image.
On axial
SE 550/20
continuous rim on the Ti-weighted
(a) and
of uneven image
1,500/80
thickness. and high
and
The ho-
layers of the parasite (germiand intermediate layer), are both very thin (9), and this
further
shortens
the
T2.
The signal intensity was homogeneous in five lesions (25%) and was the same as that of the biliary cysts except for the presence of the rim. The signal intensity was inhomogeneous in the remaining 15 lesions, especially
lated
in those
with
or multicystic
ticystic appearance ity of the borders to medical therapy
a multilocu-
aspect. and indicate (Fig
The
mul-
the
irregulara response 3). When
evaluating the signal intensity, we used the surrounding hepatic parenchyma as a reference in the qualitative evaluation of signal intensity on the images. In 100% of cases the signal
with
of the
lesions
Ti weighting
with T2 weighting. images there were
with
75%
of the
was
hypointense
and
hypermntense
On some
spin-density differences,
lesions
702
an average Radiology
#{149}
b.
Figure
3.
MR images
of a vital
cyst
after
medical
therapy
and
membranes. lobe with
Axial SE 1,500/20 (a) and 1,500/80 (b) images an exophytic proliferation on the anteromedial
weighted
image
membranes to medical
(b) the hypointense
are evident therapy.
(straight
rim arrow,
partial
show border
(open
arrow,
b) and
b). The
latter
is a sign
detachment
a hydatid (curved
the partial that
the
of the
cyst of the left arrow). On 12-
detachment parasite
of the
is responding
appearing
hypointense and 25% appearing isointense compared with the normal surrounding panenchyma. The T2 measurements of nine large lesions varied from 1 1 1 to 281 msec,
with
a.
of 173 msec,
which
is almost
the gical specimen. The presence
same
easily
ascertained
one lobe
case involved of the liver
as those
of the
sun-
involved
of daughter in
two
cysts
cases
was
only;
a cyst of the left (Fig 4) and the other
widespread
pelvic
hydati-
assessof daughter cysts of the liven, a sign of viability, is not reliable due to respiration-induced image blurring in the upper abdomen. It is also hindosis
(Fig
5).
The
MR
imaging
ment
June
1990
a. Figure 1,500/80
b. 4.
MR images (b)
images,
of a left lobe the
signal
cyst with
intensity
of the
daughter
cysts.
cyst
is inhomogeneous.
On axial
SE 1,500/20 At lapanotomy
(a) and the
cyst was almost completely full of daughter cysts that on spin-density image (a) have hypointense signal when compared with that of the hydatid matrix. On 12-weighted image (b) they have high signal intensity with some thin, inner, hypointense septations. The rim appears thicker posteriorly (arrow) with an exogeneous proliferation on its right anterior borden (arrowhead).
dened by the small number of cases with histopathologically verified viable cysts (only three patients) caused by the predominance of patients in relapse or with primitive or residual lesions who had already undergone medical treatment. With sterile cysts or acephalocysts, we could see the detachment of the proper membrane from the penicyst. If thick calcifications are present in the proper membrane, it is possible to see the MR imaging equivalent of the water lily sign (Fig 6). MR imaging, with its wide field of view, was very useful in the followup of residual lesions, of any possible recurrence (Fig 7), and of postsurgical results (Figs 7, 8). In most cases the pericyst is not completely nemoved during surgery because of its proximity to vital structures such as the vena cava. The residual cavity fills with blood cystlike lesions
or bile, that are
producing often multi-
loculated, with irregular bonders and a hypomntense rim that is thicker than that of the parasite due to healing factors (iO). The signal intensity of these lesions was high with T2 weighting and low with Ti weighting (Figs 7, 8). In this case the differential diagnosis of a possible recurnence is difficult. If the cavity is packed with omental fat, we should have seen, at least in the first few months following surgery, a high signal intensity also with Ti weighting (no such case arose in our study).
a.
b.
Extrahepatic
Hydatidosis
Extrahepatic
echinococcosis
has
many
different appearances. It may occur as isolated peritoneal lesions with the same characteristics as the hepatic cysts. It may demonstrate massive penitoneal spread (Fig 5), osseous localizations with multiloculated cysts (cyst inside a cyst), or polycystic aspects (Figs 9, 10). Multiple lesions are the most common findings. In the two observed cases of bone lesions,
several
The quent
discovery of a rim is also in extrahepatic localizations
(in d.
C.
Figure
5. MR images of massive peritoneal spread with several daughter cysts. (a) Axial SE 800/20 image depicts many hydatid cysts in the pelvis due to an open rupture into the peritoneum. The two cysts situated posteriorly (arrows) present several daughter cysts; their signal intensity is lower than that of intracystic fluid. (b) On axial SE 2,000/80 image the daughter cysts (arrows) tend to fade into the intracystic fluid as both are of high signal intensity. The anterior cyst has a multiloculated appearance (arrowheads, a and b) caused by the presence of several internal septa. (c, d) MR imaging examination of the surgical specimen. On SE 500/20 (c) and 2,000/80 (d) images, the rim is well represented even on the small daughter cysts. Some of these (arrows, c and d) have a lower signal intensity than othens on T2-weighted image also because of a smaller fluid content.
Volume
175
Number
#{149}
3
five
cysts
of seven
were
present.
cases),
while
frethe
characteristics of the signal are the same as those of hepatic lesions. T2 measurements registered a wide range of values, from 80 to 800 msec. When daughter cysts are present, they are seen as endogenous proliferations
minative
more
on less
layer,
with
joined
to the
ger-
a hypointense
signal compared to that of the intracystic fluid with Ti weighting and spin-density weighting. On T2-
Radiology
703
#{149}
weighted images the signal intensity of the daughter cysts was higher and was confused with that of the hydatid matrix (Fig 5). In cases of massive peritoneal spread, MR imaging examination of part of the surgical specimen (Fig 5c, 5d) rim
helped confirm that was easily
the seen
presence of a even in cysts
with a diameter smaller than 2 cm. Furthermore, in some of these cysts there was a lower signal intensity, on T2-weighted images, maybe due to a lower fluid content. These should be the least vital cysts. In extrahepatic hydatidosis differential diagnosis is not a problem because we are dealing with secondary localizations of an already necognized disease. In these cases the usefulness of MR imaging lays in the precise definition of anatomic relationships due to the multiplanar capabilities and the excellent contrast resolution for soft tissues.
b.
a. Figure axial
6.
MR images
SE 1,700/20
of a sterile
image
is seen
on the medial
proper
membranes
the
side,
cyst
with
situated
hydatid
cyst with detachment a bilobate appearance,
shows
the pericyst
internally
(open
located
more
arrows).
(b)
and
of the membranes. a hypointense,
externally Axial
(solid
arrows)
SE 1,700/80
MR imaging equivalent of the water lily sign: The proper membrane pointense because of calcification and freely floats on the intracystic intensity. The calcific pericyst is seen externally (solid arrows).
(a) On double rim
image
and
the
shows
the
(open arrows) is hyfluid with a high signal
DISCUSSION In hepatic and extrahepatic hydatidosis, the two techniques used currently, CT and US (iO-i2), are sufficient to obtain an anatomic evaluation. When results of serologic tests are positive, there are no problems of differential diagnosis with other types of nonparasitic cysts. When no characteristic signs of hydatidosis (ie, daughter cysts, hydatid sand,
or calcified
membranes)
are
present, the differential diagnosis can be facilitated with MR imaging, which almost always shows the typical findings of the presence of a rim or a multiloculated on multicystic featune. In the assessment of the rim, MR imaging appears more reliable than CT, as the latter shows the rim in a limited number of cases (i i). Since the rim is almost always found with
a. Figure
b. 7.
MR images
of a relapsing calcified cyst (no (a) and 2,000/80 (b) images, a cyst of the right anterior ty is inhomogeneous; the lower part, corresponding to generated material (*), has medium signal intensity on
nal intensity on 12-weighted the proper membranes that cially on 12-weighted all sequences (solid
with high,
vena
images, arrows).
the pseudocyst. inhomogeneous
cava
is compressed
On axial SE 700/20 The signal intensiand/or caseous de-
Ti-weighted images (a) and high sigimages (b). The upper part, consistent with calcified debris of have detached from the pericyst, has low signal intensity espewith Around
some the
The pseudocyst signal
histologic proof). segment is shown. the hydatid sand
has low signal
intensity
to some
small hyperintense vena cava there
extent
on
12-weighted
(open
are
intensity images
areas. some
The rim fragments
on Ti-weighted (arrowhead).
is evident with of the pericyst
images The
and
inferior
arrow).
Figure 8. Long-term postsurgical results. (a) On axial SE 500/20 image there is a zone of low signal intensity at the porta hepatis with unclear borders, possibly due to a perihilar fibrosis (open arrows). The intrahepatic portal vessels (arrowheads) are stretched and slightly enlarged and draw together toward this area of fibrosis. Portal hypertension is confirmed by the large spleen.
(b)
Axial
SE 2,500/80
image
ual, postsungical cavity sity near the vena cava ment of the pericyst intensity. The fibrous, isointense or slightly
pared with images.
704
the
Radiology
#{149}
normal
shows
of high (arrow).
maintains perihilar
the
resid-
signal intenThe fraglow signal tissue is
hyperintense comliver on 12-weighted a.
b.
June
1990
b.
a.
Figure 9. MR images of a spinal hydatid lesion (1-6 to 1-7) protruding into the right paraspinal gutter. Axial SE 1,700/20 (a) and 1,700/80 (b) images show the hydatid localization involving the vertebral body, the posterior arch, and the paravertebral tissues (arrows). The outlines are irregular and poorly defined. The signal is inhomogeneous, of medium intensity on spin-density weighted images (a) and of high intensity on 12-weighted images (b). (c) Sagittal SE 650/20 image does not show any compression of the medulla but only a slight reduction of the anterior subdunal space.
parenchymal hematoma also shows a double rim (16); the peripheral one is hypomntense and is caused by hemosiderin, and the inner one is hyperintense on Ti-weighted images due to methemoglobin, with a central hypointense core consisting of deoxyhemoglobin. The complete oxidative denatunation of deoxyhemoglobin into methemoglobin that follows removes any doubt regarding the diagnosis.
In all
pearance sufficient specific agnosis
of these
situations
the
ap-
of the rim is almost always to resolve the problem; elements for differential dialso exist. For example, fatty
degeneration
and
vascular
invasion
indicate hepatocarcinoma (13). With other mass lesions of the liver such as metastases, simple cysts, hemangiomas, and focal nodular hyperplasia (17,18), rim images have never been described, to our knowledge. At present MR imaging seems to be a.
b.
less
Figure 10. MR images of a shoulder lesion. On coronal SE 600/20 (a) and SE 2,000/80 (b) images the scapula and the soft tissues of the left shoulder are completely substituted several cysts of various sizes. The signal is inhomogeneous, of medium to low intensity Ti-weighted images and high intensity on 12-weighted images.
by
on
ble,
hydatid nosis
cysts, includes
the
differential
other
capsulated
diagmass
lesions of the liver, such as hepatocarcinoma, amebic abscess, and, less often, mntraparenchymal hematoma and hepatic adenoma. With hepatocellular carcinoma, the rim was found with a frequency ranging from 24% to 42% in the case studies in the literature (13,14). It is never as thick and continuous as it appears with hydatid cysts. Also with Volume
175
Number
#{149}
3
hydatid cysts, we have penitumoral edematous signal intensity surrounding sule with a double ring T2 weighting (14). The
seen ing
in hepatic stage,
after
liver abscess one concentric nal
intensity
ferent capsule.
(i5) and
from After
that
never zone
seen a of high the cappattern with rim is seldom
adenoma.
In the
treatment,
the
amebic
is seen as more ring with varying a signal
of the at least
pattern
healthan sigdif-
hydatid
cyst
3 weeks,
intra-
helpful
when
evaluating
vitality
on the effects of medical therapy. The MR imaging criteria used are the same as those used with CT and US: A smooth-bordered lesion with daughter cysts is most probably viawhile
tachment regular
capsular
calcifications,
of the membranes, edges are signs that
site
is succumbing.
are
difficult
Daughter
to see at MR
and the calcified at CT. Compared ing seems more
de-
and inthe paracysts
imaging,
rim is shown better with CT, MR imaguseful and reliable
when looking for the irregularities the rim bonders with considerable differences in thickness, probably signs of a partial membranes.
detachment
Radiology
of
of the
705
#{149}
Although, in theory, a reduction of the water content of the cyst is connected to a reduction in biological exchange between the parasite and
2.
host (9), not show
3.
the T2 measurements significant differences
did
its
high
signal-to-noise
capability does not this
more slight
ratio
Barley
and
but
detailed diagnostic
it does
anatomic gain.
provide
view
pont
of
611 cases from 1967; 99:660-667.
706
Radiology
#{149}
A.
1 12 cases
the
Iran
United
disease: and
States.
a review
AJR
1983;
24:A996.
Morris
DL,
epidemiology
England
F,
12.
diagof hyda-
and
Wales.
Gut
13.
J, Cregson
Buckley
R, Worresonance imagClin Radiol 1987;
Magnetic disease.
14.
338:141-144.
5.
Lupetin
6.
tune of hydatid cyst: MR findings. 1988; 151:491-492. Mikhael MA, Cinic IS, Tarkington
AR,
imaging
7.
in
Dash
S. Viale
and
magnetic
hydatidosis.
N.
spinal
ME, Glazer disease of 1987; 12:39-
Intrahepatic
echinococcosis.
put Assist Tornogn Pau A, Sirnonetti tas
CL.
JA. MR J Corn-
1985; 9:398-400. C, Tortori-Donati Computed
resonance Sung
rup-
1987;
in spinal 27:365-
Desnos
9.
Polyvisceral echinococcosis with cardiac involvement imaged by two-dimensional echocardiognaphy, computed tomography and nuclear magnetic resonance imaging. Am J Cardiol 1987; 59:383-384. Sommaniva V. L’idatidosi epatica. Arch Atti Soc It Chir 1984; 1:223-371. Kalavidouris A, Gouliamos A, Demou L, Vassilopoulos P. Vlachos L, Papavassiliou K. Postsurgical evaluation of hydatid disease with CT: diagnostic pitfalls. J Comput
a
reof
Assist
1 1.
Tomogr
Brochet
E, Cristofini
1984;
P. et al.
Niron EA, Ozer H. Ultrasound appearance of liver hydatid disease. Br J Radiol 1981; 54:335-338. Rummeny E, Weissleder R, Stark DD, et al. Primary liver tumors: diagnosis by MR imaging. AJR 1989; 152:63-72. Itoh K, Nishimura K, Togashi K, et al. Hepatocellular carcinoma: MR imaging. Radiology 1987; 164:21-25. Elizondo C, Weissleder R, Stark DD, et al. Amebic liver abscess: diagnosis and treatment evaluation with MR imaging. Radiology 1987; 165:795-800. Hahn PF, Saini 5, Stark DD, Papanicolaou N,
17.
P. Tur-
369. M,
16.
tomography
imaging
Neunol
15.
AJR
8.
U
Echinoccus from
in
Pritchard
Serological
Hoff FL, Aisen AM, Walden CM. MR imaging in hydatid the liver. Castrointest Radiol 42.
10.
Bonakdarpoun
current
disease
MJ,
DL.
4.
References 1.
Clarkson
Morris
thington BS. ing in hydatid
the
with
and
tid
to obtain thinner sections, modify the possibilities of
technique,
MF,
KW,
nosis
be-
tween fertile and sterile cysts, and the range of values was too wide to be of use. To conclude, MR imaging is of value in the study of hydatid disease. In hepatic localizations it can be used to determine the presence of a characteristic sign such as the rim, and in extrahepatic lesions it enables the evaluation of anatomic relationships. Compared with previous results obtained with MR imaging units of low to medium field strength, we believe that the use of a i.5-T unit, with
Stallbaumer
18.
Fenrucci
JT.
Intnaabdominal
hemato-
ma: the concentric ring sign in MR imaging. AJR 1987; 148:115-119. Wittenberg J, Stark DD, Forman BH, et al. Differentiation of hepatic metastases from hepatic hemangioma and cysts by using MR imaging. AJR 1988; 151:79-84. Mattison CR, Clazer CM, Quint LE, Francis IR, Bree LR, Ensminger WD. MR imaging of hepatic focal nodular hyperplasia: characterisation and distinction from primary malignant hepatic tumors. AJR 1987; 148:711-715.
8:1114-1119.
Pandolfo I, Blandino C, Scribano E, Longo M, Certo A, Chinico C. CT findings in hepatic involvement by Echinococcus granulosus. J Comput Assist Tomogr 1984; 8:839845.
June
1990
