Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
525
Hydatid
Disease
Imaging
T. Franquet1 M. Montes2 F. J. Lecumberri3 J. Esparza4 J. M. Bescos1
Findings
of the Spleen: in Nine Patients .
,
Splenic involvement is uncommon in patients with hydatid disease. The radiologic and clinical findings in nine patients with splenic hydatidosis are described. The three men and six women were 41-76 years old (mean, 58 years). Their histories and physical findings, the results of serologic tests for hydatidosis, and imaging procedures were evaluated. Plain abdominal radiographs were obtained in all nine patients, sonograms in six, and CT scans in seven. Plain films showed calcification of the cyst wall in four of the nine patients. On sonograms, five lesions were anechoic and one was echogenic. On CT scans, all lesions except one were of lower attenuation than the surrounding spleen. None of the lesions enhanced after administration of IV contrast material. Although rare, splenic hydatidosis should be included in the differential diagnosis when a cystic splenic lesion is identified with sonography or CT. March
i54:525-528,
AJR
1990
Splenic involvement in hydatid disease is uncommon, representing less than 2% of all human infestations by Echinococcus [i -3]. To our knowledge, previous descriptions of the imaging findings in splenic hydatidosis have been based on sporadic case reports [4-6] and lack pathologic correlation. We studied the imaging findings in nine cases of serologically or surgically proved splenic hydatid disease and correlated the results with clinical and pathologic data. Materials
and
Methods
We retrospectively whom
splenic
reviewed
hydatidosis
three men and six women results
of
serologic
immunosorbent six patients; used.
Received August 18. 1989; accepted after revision October
11. 1989.
sonographic
(1) calcification,
Department of Radiology. Hospital Virgen del Camino, c/lrunlarrea s/n, 31 008 Pamplona, Spain.
three
patients
Address reprint requests to T. Franquet. 2 Department of Pathology, Hospital Virgen del
Intraperitoneal
Camino.”
that
Spain.
Department of Radiology. de Navarra, Pamplona. Spain. 3
Department of Radiology. de Navarra. Pamplona. Spain. 4
Chinica Universitaria
Capron when
0361 -803X/90/1 543-0525 © American Roentgen Ray Society
Provincial
was
and
left
spread
tested
of hydatid the
position
in the
sera
from
value, in five
in one
disease presence
with
of nine patients
and
Histories,
1988.
There
in
were
physical
findings,
and
enzyme-linked
agglutination,
and who
was observed of an antigen as a band
human
patients.
immunoelectrophoretic
to echo
in seven evaluated
patients.
patient
Sonography
and
Other also
pattern.
and
pre- and following
of contrast
(3) degree
symptoms
had
performed
in
transducers
texture
patients: for the
was
definition
of
postcontrast CT findings:
enhancement. included
fever
hydatid
disease.
pulmonary
in
in two patients. specific
for
of characteristic
They
was
with 3.5- or 5-MHz regard
performed lesion was
initially pain
equipment
evaluated were Each
immunoelectrophoretically against
58 years).
radiography.
real-time
attenuation
chest
findings 1982
were evaluated.
were
present
et al. [7] reported
appeared
relative Hospital
available studies
pain
between latex
by conventional
(2) precontrast
Abdominal
and radiohogic
treated
years old (mean,
for hydatidosis
examined
commercially
The
and
(immunoelectrophoresis,
the splenic mass. CT examinations images were available in all cases.
I
31 008 Pamplona,
were
records
diagnosed
4i -76
tests
assay)
All patients
the medical
was
named The
this arc
Echinococcus morphology band
arc
5 of Capron
granulosus and
location
5 because was
present
of its in
seven patients and absent in two patients who had calcified hydatid cysts. In calcified hydatid cysts it is postulated that the physical status of the hydatid cyst membranes influences the degree of antigen stimulation of the immune system of the host and therefore affects the success
of the
immunodiagnostic
test
[7. 8].
526
FRANQUET
Surgical
Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
measured
specimens 8-16
were
cm.
available
in six patients.
Macroscopically,
the
cyst
At surgery,
walls
were
cysts
white
and
smooth in all cases. Most of the cysts (five cases) were fluid-filled; small daughter cysts were observed in one case (Fig. 1 B). A dense yellow material was present in one case that also had small peripheral calcifications (Fig. 2C). Microscopically, the cysts comprised three characteristic layers: (1 ) external layer or adventitia formed by com-
pressed and fibrotic splenic tissue with a diffuse infiltration of lymphocytes, plasma cells, and eosinophils; (2) intermediate layer or cuticula formed by noncellular (3) intimal or germinal
scoleces cyst
and microcysts.
consisted
hooklets,
laminated layer
and
of debris,
eosinophihic formed by
At microscopic
a mixture which
of was
infolded part
of the
tissue 1 mm a discontinuous
study,
thick; and layer of
the semisolid
membranes, hydatid
filled
fragmented “sand.”
Results
The most common radiographic finding, cases, was splenomegaly, or a soft-tissue
seen in five of nine mass, in the left
ET AL.
AJR:154,
March
1990
upper quadrant (with or without calcification). One patient had associated pulmonary involvement. Linear calcification of the spleen was observed on plain radiographs in four of nine patients (Fig. 3). The cysts were partly calcified in two patients and completely calcified in the remaining two. Serologic tests for hydatidosis were negative in patients with intensely calcified cysts. On sonography (six cases), five masses were anechoic, often with considerable homogeneity. A single cysts was observed in all cases. An intracystic small daughter cysts was seen in one patient (Fig. i ). Only one lesion showed an echogenic (solid) pattern with sonography, corresponding to intracystic infolded membranes and hydatid sand (Fig. 2). On abdominal CT (seven cases), calcification was evident in four cases. In all cases, the mass or masses were sharply delineated on precontrast and/or postcontrast scans (Fig. 4). All lesions except one were of lower attenuation than the
Fig. 1.-48-year-old datidosis. A, Oblique
sonogram
woman
with splenic
of left upper
hy-
quadrant
shows spherical anechoic mass containing small cystic lesion. B, Corresponding gross specimen shows splenic hydatid cyst with whitish cuticular and granular germinal layer. Two small daughter cysts are visible within lesion (arrows).
A
B
Fig. 2.-5plenic hydatid cyst in 45-year-old woman with abdominal pain. A, Oblique sonogram shows echogenic (solid) mass corresponding to hydatid cyst. Cyst is filled by echogenic material composed of hydatid folded membranes (arrowheads), and debris. B, Unenhanced CT scan shows hypodense splenic mass with discontinuous peripheral rim calcification (arrows). C, Corresponding gross specimen shows that cyst is occupied by membranes, debris, and fibrin. Calcifications are visible in peripheral layer. membranes leave clefts occupied by aqueous liquid evident on sonography.
sand,
in-
Infolding
Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
Fig. 3.-63-year-old man with splenic hydatid disease. A, Plain film shows rounded calcified mass in left upper quadrant. B, Unenhanced CT scan shows large intrasplenic mass with high CT numbers. Peripheral calcification is also seen clearly on CT. Density of mass is similar to that of liver and spleen.
Fig. 4.-Splenic hydatidosis in 57-year-old man with decompensated liver cirrhosis. A, Longitudinal sonogram of left upper quadrant shows loculated anechoic splenic lesion. B, Contrast-enhanced CT scan shows multiloculated hypodense splenic mass, hypertrophied caudate lobe of liver, and ascitic fluid.
:)
surrounding spleen. No lesion enhanced after administration of IV contrast material. Multiple cysts were observed in two patients (Fig. 5). CT provided additional information in three cases: one patient had a small splenic cysts not observed sonographically and another had a calcified hydatid cyst in the liver (Fig. 6); in the third, who had decompensated liver cirrhosis, multiple focal splenic lesions were seen that were highly suggestive of splenic infarcts. In two cases, intraperitoneal hydatid spread was clearly shown on both sonography and CT. The internal cystic content was better delineated by sonography than by CT in one case that showed an echogenic (solid) pattern on sonography.
Discussion
Hydatid disease is caused by the larval form of the genus Echinococcus, of which Echinococcus granulosus is the most common. The liver and lungs are the most frequently involved organs. Splenic hydatidosis has been found in about 2% of all patients with echinococcosis [1]. Systemic dissemination and intraperitoneal spread from a ruptured liver cyst constitute the two most important sources of splenic infestation. The clinical manifestations of splenic hydatid disease are nonspecific. Abdominal pain, enlarged spleen, and fever are the most frequently encountered symptoms. However, secondary infection, cyst rupture, and anaphylactic shock may
develop [4-6]. tic for hydatid
.
immunologic tests are highly diagnosThe presence of the arc 5 of Capron [7] on immunoelectrophoresis is the most reliable laboratory
finding
Several disease.
in human
hydatidosis
[7, 8].
However,
in residual
or
calcified hydatidosis, the arc 5 may be absent. Falsepositive serologic test results have been reported in patients with malignant disease [9]. The radiographic appearance of splenic hydatidosis varies and is influenced mainly by the location of the cyst, age of the cyst, and associated complications, such as secondary infection and rupture [5]. Before the development of crosssectional imaging, radiographic evaluation of focal splenic lesions was limited to plain abdominal films and isotopic studies. At present, sonography and CT are the most valuable imaging techniques for the diagnosis and evaluation of focal splenic diseases [3]. CT findings of splenic hydatid disease are not specific, although the usefulness of CT in the diagnosis is well established. Our data suggest that CT findings in splenic hydatidosis are similar to those previously described for liver echinococcosis [1 0-i 2]. The CT attenuation in hydatidosis depends on the intracystic content. Hydatid cysts usually have a homogeneous fluid content showing water attenuation values on CT. However, hydatid cysts may show high CT values on unenhanced CT scans. The presence of intracystic debris, hydatid sand, and inflammatory cells are presumed to cause the high CT values highly
Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
528
FRANQUET
ET AL.
AJR:154, March 1990
Fig. 5.-Multiple splenic hydatid cysts in asymptomatic 62-year-old man. Unenhanced CT scan shows multiple hypodense lesions corresponding to multiple splenic echinococcal cysts.
Fig. 6.-62-year-old tosplenic
hydatidosis.
man with residual Unenhanced
CT
hepascan
shows large calcified splenic hydatid cyst.
in these cases [1 2]. Calcification may occur in the wall of the cyst after the death of the parasite and may be observed on plain abdominal radiographs. However, CT is more sensitive than plain films or sonograms in depicting subtle cyst wall calcification. When there is calcification, it will be shown better on unenhanced CT because IV contrast material may cause the calcification to be masked by the surrounding enhanced splenic parenchyma. Similarly, the sonographic findings of splenic hydatid cysts are not specific, even if the typical findings of solitary, anechoic lesions are demonstrated. Various sonographic patterns of hydatid cysts have been described [1 3-1 7]. In our series, most of the surgically removed splenic cysts were fluid-filled. These pathologic findings support the fact that an anechoic pattern was observed most often. The mixture of infolded membranes, scoleces, and hydatid sand may produce a highly echogenic (solid) pattern on sonography because of the large acoustic impedance differences between the intracystic components. This unusual sonographic pattern was observed in only one case in our series and was demonstrated posteriorly on the corresponding gross specimen. Recent published reports indicate that MR may be an important imaging technique in the diagnosis and evaluation of hydatid disease [i 8, i 9]. However, we believe that MR should not be used as the first imaging method in the study of patients with proved or suspected hydatid disease. The main problem in the diagnosis of splenic hydatidosis is in differentiating it from other splenic cystic lesions that have similar appearances on sonography and CT. The differential diagnosis of such lesions includes epidermoid cyst, pseudocyst, large solitary abscess or hematoma, intrasplenic pancreatic pseudocyst, and cystic neoplasm of the spleen [3]. Hydatidosis should be suspected in patients with splenic cystic lesions, particularly in endemic areas. The diagnosis of splenic hydatidosis should be favored if daughter cysts are present within a large cystic lesion or if cystic lesions are observed in other organs such as the liver. In conclusion, the diagnosis of splenic hydatid disease relies on documentation of the lesion with imaging techniques supported by specific serologic tests. Sonography and CT are the most valuable imaging methods in the evaluation of pa-
tients with clinical, hydatid disease.
biochemical,
or radiologic
suspicion
for
REFERENCES 1 . Bonakdarpour A. Echinococcus disease: report of 1 1 2 cases from Iran and a review of 61 1 cases from the United States. AJR 1967;99:660-667 2. Beggs I. The radiology of hydatid disease. AJR 1985:145:639-648 3. Dachman AH, Ros PR, Murari PJ, Olmsted WW, Lichtenstein JE. Nonparasitic splenic cysts: a report of 52 cases with radiologic-pathologic correlation. AJR 1986:147:537-542 4. Narasimharao KL, Venkateswarlu K, Mitra 5K, Metha S. Hydatid disease of the spleen treated by cyst enucleation and splenic salvage. J Pediatr Surg 1987:22:138-139 5. Caballero P. Ocon E, Robledo AG, Diaz FJ. Splenic hydatid cysts opening to the colon. AJR 1986; 147 :859-860 6. Varghese C, Balakrishnam V. Hydatid cyst of the spleen-an unusual presentation. J Assoc Physicians India 1979:27:1039-1041 7. Capron A, Yarzabal LA, Vernes A, Fruit J. Le diagnostic immunologique de l’echinococcose humaine (bilan personnel a propos de 400 observations). Patho! Biol (Paris) 1970:18:357-365 8. Yarzabal LA. Leiton J, Lopez-Lemes H. The diagnosis of human pulmonary hydatidosis by the immunoelectrophoresis test. Am J Trop Med Hyg 1974:23:662-666 9. Dar FK, Buhidma MA, Kidwai SA. Hydatid false positive serological test results in malignancy. Br Med J 1984:288:1197 10. De Diego JC, Lecumberri FJO, Franquet TC, Ostiz SZ. Computed tomography in hepatic echinococcosis. AJR 1982:138:699-702 1 1 . Kalovidouris A, Pissiotis C. Pontifex G, Gouhiamos A, Pantea S. Papayassihiou C. CT characterization of multivesicular hydatid cysts. J Comput Assist Tomogr 1986:10:428-431 12. Lewall DB, Bailey TM, McCorkehl SJ. Echinococcal matrix: computed tomographic, sonographic and pathologic correlation. J Ultrasound Med 1987;5:33-35 13. Shulman A, Van Jaarsveld J, Loxton AJ, Grove WH. Pseudosohid appearance of simple and echinococcal cysts in ultrasonography. S Afr Med J
1983:63:905-906 14. Niron EA, Ozer H. Ultrasound appearance of hydatid disease. Br J Radio! 1981;54:335-338 1 5. ltzchak Y. Rubinstein Z, Heyman Z, Gerzof S. Role of ultrasound in the diagnosis of abdominal hydatid disease. JCU 1980:8:341-345 16. Gharbi HA, Hassine W, Brauner NW, Dupuch K. Ultrasound examination of the hydatid liver. Radiology 1981 ; 1 39 :459-463 17. Lewall DB, McCorkell SJ. Hepatic echinococcal cysts: sonographic appearance and classification. Radiology 1985:1 55 :773-775 18. Hoff FL, Alsen AM, Walden ME, Glazer GM. MR imaging in hydatid disease of the liver. Gastrointest Radio! 1987;1 2:39-42 19. Lupetin AR, Dash N. Intrahepatic rupture of hydatid cyst: MR findings. AJR 1988;151 :491 -492
525
Hydatid
Disease
Imaging
T. Franquet1 M. Montes2 F. J. Lecumberri3 J. Esparza4 J. M. Bescos1
Findings
of the Spleen: in Nine Patients .
,
Splenic involvement is uncommon in patients with hydatid disease. The radiologic and clinical findings in nine patients with splenic hydatidosis are described. The three men and six women were 41-76 years old (mean, 58 years). Their histories and physical findings, the results of serologic tests for hydatidosis, and imaging procedures were evaluated. Plain abdominal radiographs were obtained in all nine patients, sonograms in six, and CT scans in seven. Plain films showed calcification of the cyst wall in four of the nine patients. On sonograms, five lesions were anechoic and one was echogenic. On CT scans, all lesions except one were of lower attenuation than the surrounding spleen. None of the lesions enhanced after administration of IV contrast material. Although rare, splenic hydatidosis should be included in the differential diagnosis when a cystic splenic lesion is identified with sonography or CT. March
i54:525-528,
AJR
1990
Splenic involvement in hydatid disease is uncommon, representing less than 2% of all human infestations by Echinococcus [i -3]. To our knowledge, previous descriptions of the imaging findings in splenic hydatidosis have been based on sporadic case reports [4-6] and lack pathologic correlation. We studied the imaging findings in nine cases of serologically or surgically proved splenic hydatid disease and correlated the results with clinical and pathologic data. Materials
and
Methods
We retrospectively whom
splenic
reviewed
hydatidosis
three men and six women results
of
serologic
immunosorbent six patients; used.
Received August 18. 1989; accepted after revision October
11. 1989.
sonographic
(1) calcification,
Department of Radiology. Hospital Virgen del Camino, c/lrunlarrea s/n, 31 008 Pamplona, Spain.
three
patients
Address reprint requests to T. Franquet. 2 Department of Pathology, Hospital Virgen del
Intraperitoneal
Camino.”
that
Spain.
Department of Radiology. de Navarra, Pamplona. Spain. 3
Department of Radiology. de Navarra. Pamplona. Spain. 4
Chinica Universitaria
Capron when
0361 -803X/90/1 543-0525 © American Roentgen Ray Society
Provincial
was
and
left
spread
tested
of hydatid the
position
in the
sera
from
value, in five
in one
disease presence
with
of nine patients
and
Histories,
1988.
There
in
were
physical
findings,
and
enzyme-linked
agglutination,
and who
was observed of an antigen as a band
human
patients.
immunoelectrophoretic
to echo
in seven evaluated
patients.
patient
Sonography
and
Other also
pattern.
and
pre- and following
of contrast
(3) degree
symptoms
had
performed
in
transducers
texture
patients: for the
was
definition
of
postcontrast CT findings:
enhancement. included
fever
hydatid
disease.
pulmonary
in
in two patients. specific
for
of characteristic
They
was
with 3.5- or 5-MHz regard
performed lesion was
initially pain
equipment
evaluated were Each
immunoelectrophoretically against
58 years).
radiography.
real-time
attenuation
chest
findings 1982
were evaluated.
were
present
et al. [7] reported
appeared
relative Hospital
available studies
pain
between latex
by conventional
(2) precontrast
Abdominal
and radiohogic
treated
years old (mean,
for hydatidosis
examined
commercially
The
and
(immunoelectrophoresis,
the splenic mass. CT examinations images were available in all cases.
I
31 008 Pamplona,
were
records
diagnosed
4i -76
tests
assay)
All patients
the medical
was
named The
this arc
Echinococcus morphology band
arc
5 of Capron
granulosus and
location
5 because was
present
of its in
seven patients and absent in two patients who had calcified hydatid cysts. In calcified hydatid cysts it is postulated that the physical status of the hydatid cyst membranes influences the degree of antigen stimulation of the immune system of the host and therefore affects the success
of the
immunodiagnostic
test
[7. 8].
526
FRANQUET
Surgical
Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
measured
specimens 8-16
were
cm.
available
in six patients.
Macroscopically,
the
cyst
At surgery,
walls
were
cysts
white
and
smooth in all cases. Most of the cysts (five cases) were fluid-filled; small daughter cysts were observed in one case (Fig. 1 B). A dense yellow material was present in one case that also had small peripheral calcifications (Fig. 2C). Microscopically, the cysts comprised three characteristic layers: (1 ) external layer or adventitia formed by com-
pressed and fibrotic splenic tissue with a diffuse infiltration of lymphocytes, plasma cells, and eosinophils; (2) intermediate layer or cuticula formed by noncellular (3) intimal or germinal
scoleces cyst
and microcysts.
consisted
hooklets,
laminated layer
and
of debris,
eosinophihic formed by
At microscopic
a mixture which
of was
infolded part
of the
tissue 1 mm a discontinuous
study,
thick; and layer of
the semisolid
membranes, hydatid
filled
fragmented “sand.”
Results
The most common radiographic finding, cases, was splenomegaly, or a soft-tissue
seen in five of nine mass, in the left
ET AL.
AJR:154,
March
1990
upper quadrant (with or without calcification). One patient had associated pulmonary involvement. Linear calcification of the spleen was observed on plain radiographs in four of nine patients (Fig. 3). The cysts were partly calcified in two patients and completely calcified in the remaining two. Serologic tests for hydatidosis were negative in patients with intensely calcified cysts. On sonography (six cases), five masses were anechoic, often with considerable homogeneity. A single cysts was observed in all cases. An intracystic small daughter cysts was seen in one patient (Fig. i ). Only one lesion showed an echogenic (solid) pattern with sonography, corresponding to intracystic infolded membranes and hydatid sand (Fig. 2). On abdominal CT (seven cases), calcification was evident in four cases. In all cases, the mass or masses were sharply delineated on precontrast and/or postcontrast scans (Fig. 4). All lesions except one were of lower attenuation than the
Fig. 1.-48-year-old datidosis. A, Oblique
sonogram
woman
with splenic
of left upper
hy-
quadrant
shows spherical anechoic mass containing small cystic lesion. B, Corresponding gross specimen shows splenic hydatid cyst with whitish cuticular and granular germinal layer. Two small daughter cysts are visible within lesion (arrows).
A
B
Fig. 2.-5plenic hydatid cyst in 45-year-old woman with abdominal pain. A, Oblique sonogram shows echogenic (solid) mass corresponding to hydatid cyst. Cyst is filled by echogenic material composed of hydatid folded membranes (arrowheads), and debris. B, Unenhanced CT scan shows hypodense splenic mass with discontinuous peripheral rim calcification (arrows). C, Corresponding gross specimen shows that cyst is occupied by membranes, debris, and fibrin. Calcifications are visible in peripheral layer. membranes leave clefts occupied by aqueous liquid evident on sonography.
sand,
in-
Infolding
Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
Fig. 3.-63-year-old man with splenic hydatid disease. A, Plain film shows rounded calcified mass in left upper quadrant. B, Unenhanced CT scan shows large intrasplenic mass with high CT numbers. Peripheral calcification is also seen clearly on CT. Density of mass is similar to that of liver and spleen.
Fig. 4.-Splenic hydatidosis in 57-year-old man with decompensated liver cirrhosis. A, Longitudinal sonogram of left upper quadrant shows loculated anechoic splenic lesion. B, Contrast-enhanced CT scan shows multiloculated hypodense splenic mass, hypertrophied caudate lobe of liver, and ascitic fluid.
:)
surrounding spleen. No lesion enhanced after administration of IV contrast material. Multiple cysts were observed in two patients (Fig. 5). CT provided additional information in three cases: one patient had a small splenic cysts not observed sonographically and another had a calcified hydatid cyst in the liver (Fig. 6); in the third, who had decompensated liver cirrhosis, multiple focal splenic lesions were seen that were highly suggestive of splenic infarcts. In two cases, intraperitoneal hydatid spread was clearly shown on both sonography and CT. The internal cystic content was better delineated by sonography than by CT in one case that showed an echogenic (solid) pattern on sonography.
Discussion
Hydatid disease is caused by the larval form of the genus Echinococcus, of which Echinococcus granulosus is the most common. The liver and lungs are the most frequently involved organs. Splenic hydatidosis has been found in about 2% of all patients with echinococcosis [1]. Systemic dissemination and intraperitoneal spread from a ruptured liver cyst constitute the two most important sources of splenic infestation. The clinical manifestations of splenic hydatid disease are nonspecific. Abdominal pain, enlarged spleen, and fever are the most frequently encountered symptoms. However, secondary infection, cyst rupture, and anaphylactic shock may
develop [4-6]. tic for hydatid
.
immunologic tests are highly diagnosThe presence of the arc 5 of Capron [7] on immunoelectrophoresis is the most reliable laboratory
finding
Several disease.
in human
hydatidosis
[7, 8].
However,
in residual
or
calcified hydatidosis, the arc 5 may be absent. Falsepositive serologic test results have been reported in patients with malignant disease [9]. The radiographic appearance of splenic hydatidosis varies and is influenced mainly by the location of the cyst, age of the cyst, and associated complications, such as secondary infection and rupture [5]. Before the development of crosssectional imaging, radiographic evaluation of focal splenic lesions was limited to plain abdominal films and isotopic studies. At present, sonography and CT are the most valuable imaging techniques for the diagnosis and evaluation of focal splenic diseases [3]. CT findings of splenic hydatid disease are not specific, although the usefulness of CT in the diagnosis is well established. Our data suggest that CT findings in splenic hydatidosis are similar to those previously described for liver echinococcosis [1 0-i 2]. The CT attenuation in hydatidosis depends on the intracystic content. Hydatid cysts usually have a homogeneous fluid content showing water attenuation values on CT. However, hydatid cysts may show high CT values on unenhanced CT scans. The presence of intracystic debris, hydatid sand, and inflammatory cells are presumed to cause the high CT values highly
Downloaded from www.ajronline.org by UCSF LIB & CKM/RSCS MGMT on 04/13/15 from IP address 169.230.243.252. Copyright ARRS. For personal use only; all rights reserved
528
FRANQUET
ET AL.
AJR:154, March 1990
Fig. 5.-Multiple splenic hydatid cysts in asymptomatic 62-year-old man. Unenhanced CT scan shows multiple hypodense lesions corresponding to multiple splenic echinococcal cysts.
Fig. 6.-62-year-old tosplenic
hydatidosis.
man with residual Unenhanced
CT
hepascan
shows large calcified splenic hydatid cyst.
in these cases [1 2]. Calcification may occur in the wall of the cyst after the death of the parasite and may be observed on plain abdominal radiographs. However, CT is more sensitive than plain films or sonograms in depicting subtle cyst wall calcification. When there is calcification, it will be shown better on unenhanced CT because IV contrast material may cause the calcification to be masked by the surrounding enhanced splenic parenchyma. Similarly, the sonographic findings of splenic hydatid cysts are not specific, even if the typical findings of solitary, anechoic lesions are demonstrated. Various sonographic patterns of hydatid cysts have been described [1 3-1 7]. In our series, most of the surgically removed splenic cysts were fluid-filled. These pathologic findings support the fact that an anechoic pattern was observed most often. The mixture of infolded membranes, scoleces, and hydatid sand may produce a highly echogenic (solid) pattern on sonography because of the large acoustic impedance differences between the intracystic components. This unusual sonographic pattern was observed in only one case in our series and was demonstrated posteriorly on the corresponding gross specimen. Recent published reports indicate that MR may be an important imaging technique in the diagnosis and evaluation of hydatid disease [i 8, i 9]. However, we believe that MR should not be used as the first imaging method in the study of patients with proved or suspected hydatid disease. The main problem in the diagnosis of splenic hydatidosis is in differentiating it from other splenic cystic lesions that have similar appearances on sonography and CT. The differential diagnosis of such lesions includes epidermoid cyst, pseudocyst, large solitary abscess or hematoma, intrasplenic pancreatic pseudocyst, and cystic neoplasm of the spleen [3]. Hydatidosis should be suspected in patients with splenic cystic lesions, particularly in endemic areas. The diagnosis of splenic hydatidosis should be favored if daughter cysts are present within a large cystic lesion or if cystic lesions are observed in other organs such as the liver. In conclusion, the diagnosis of splenic hydatid disease relies on documentation of the lesion with imaging techniques supported by specific serologic tests. Sonography and CT are the most valuable imaging methods in the evaluation of pa-
tients with clinical, hydatid disease.
biochemical,
or radiologic
suspicion
for
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