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1213
Pictorial Essay #{149}
#{149}
#{149}
CT of Acquired Andrew
#{149}
Abnormalities
J. Taylor,1 Wylie J. Dodds,
of the Spleen
Scott J. Erickson, and Edward
T. Stewart
Imaging considerations and features when assessing acquired abnormalities of the spleen with CT are described. Indexes of normal size and the implications of splenomegaly are discussed, as well as the CT appearances and types of neoplasia, cysts, traumatic injuries, infarction, and inflammatory changes.
Size
In a recent report, we described the radiologic splenic anatomy, embryology, and developmental
upper limit of normal for splenic size. However, because of wide variation in shape, there is no direct correlation in the
[1]. In this essay, we describe malities
CT findings
Although
features of anomalies
of acquired
spleen’s
abnor-
large
in children,
the
spleen
progres-
length
to its overall
volume
as there
is for other
organs such as the kidney. A product oflength (a craniocaudal measure of approximately 1 2 cm) times depth (an anteroposterior dimension of approximately 7 cm) times width (the thickness at the hilum of about 4 cm) has been used to define
of the spleen.
General
relatively
sively decreases in size with age. In middle-aged patients, the spleen is about the size of a fist, weighting approximately 150 g. A craniocaudal measure of 13 cm is frequently used as the
Considerations
tough capsule, the spleen consists of a lattice of lymphatic follicles and reticuloendothelial cells (white pulp) with interspersed vascular lakes (red pulp). On unenhanced CT scans,
splenic size. Normal limits of this volume range up to 480 cm3 [2]. A more arduous measure of size is adding the volume of each slice on the CT scan. As a practical matter, judgment about the spleen size is usually based on visual inspection and experience.
the spleen has an attenuation similar to that of the liver, approximately 40 H. Normally, the liver and spleen densities are within 1 5 H on unenhanced scans and within 25 H on
The causes of splenomegaly are numerous. The most common cause of splenomegaly in our practice is cirrhosis with its attendant portal hypertension (Fig. 2). Approximately
dynamic contrast-enhanced scans. The spleen generally remains a constant reference point in CT attenuation values, as various metabolic states can decrease (fatty infiltration) or increase (hemochromatosis) the attenuation of the liver. Because of the difference in timing of enhancement of red and white pulp during the early phases of the dynamic contrastenhanced CT, the spleen may be inhomogeneous initially (Fig. 1).These changes vary from subtly to markedly inhomogeneous. Repeating images of the spleen within minutes will show a homogeneous pattern.
30% of splenomegaly cases are caused by lymphoma. AIDS and IV drug abuse increasingly deserve consideration because they cause mild to moderate splenic enlargement either from reactive hyperplasia (Fig. 3) or from complications related
The
largely
characteristics
Received 1
of the
by its underlying
May 6, 1991;
accepted
All authors: Department
Address
reprint
requests
AJR 157:1213-1219,
spleen
histologic
on CT are determined
anatomy.
after revision
of Radiology,
Covered
by a
to these disease complexes. Massive splenomegaly is usually caused by chronic myelogenous leukemia, lymphoma, polycythemia vera, myelofibrosis, or, in the appropriate population of patients, malaria. At times, spontaneous rupture may occur as a complication of splenomegaly, particularly with mononucleosis or leukemia.
July 2, 1991.
Medical College
of Wisconsin,
Froedtert
Memorial
Lutheran
to A. J. Taylor.
December
1991 0361-803X/91/1576-1213C
American
Roentgen
Ray Society
Hospital,
9200
W. Wisconsin
Ave.,
Milwaukee,
WI 53226.
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1214
TAYLOR
ET
AL.
AJR:157,
December
1991
Fig. 1.-Normal spleen with marked inhomogenefty during early contrast enhancement. A, CT image obtained early during single-level dynamic scanning shows variegated appearance of spleen. (Note lack of hepatlc parenchymal and hepatlc venous enhancement.) B, On an image obtained 35 sec later, spleen is homogeneous.
2.-Cirrhosis. CT scan shows enlarged with homogeneous parenchyma, a manifestation of portal hypertension. Also, note large splenic hilar varices (straight solid white arrows), recanallzed perlumbilical vein (open arrow), nodular liver edge (black arrows), and ascites (curved arrows). Fig. spleen
Fig. 3.-AIDS-related splenomegaly. CT scan shows moderate splenomegaly as part of a generalized lymphoid hyperplasia. No neoplastic or inflammatory cause was found in follow-up.
Fig. 4.-Lymphoma. A, On this CT scan, non-Hodgkin lymphoma is manifested by numerous, small, low-attenuation areas representing nests of tumor. Laterally, these deposits are beginning to coalesce (arrow). B, In another patient, CT scan shows a less common pattern of splenic Iymphoma: discrete large masses within spleen.
Neoplasia Both benign and malignant neoplastic involvement of the spleen occur, although a malignant cause is more frequent. Primary malignant tumors of the spleen, such as angiosarcoma, are rare. Much more common is hematologic malig-
nancy or metastatic disease. Lymphoma is the most common malignant tumor involving the spleen [2]. Approximately one third of all patients with lymphoma (Hodgkin disease and nonHodgkin disease) have splenic involvement, usually with nests of cells smaller than 1 cm in diameter. This infiltrative pattern makes detection of disease difficult on CT (Fig. 4). Conversely,
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AJR:157,
ACQUIRED
December1991
SPLENIC
ABNORMALITIES
ON
1215
CT
Fig. 5.-Metastatic disease. CT scan shows well-circumscribed low-attenuation splenic mass (open arrow) in patient with ovarian carcinoma. This appearance is typical for splenlc metastases. Other evidence of metastatic spread is usually present; In this case, adenopathy is present in retrocrural space (curved arrow) and gastrohepatic ligament (straight solid arrow).
Fig. 6.-Lymphangioma. CT scan shows wellcircumscribed, low-attenuation masses throughout spleen (arrows). These lesions correlated wIth cystic-appearing lesions seen on sonography. Having these typical findings of lymphangioma,
this 85-year-old tively.
patient
was treated
conserva-
Fig. 7.-Traumatic
cyst. This 23-year-old woman was in an auto accident 7 years earlier and now quadrant. A, CT scan shows markedly enlarged spleen with low-attenuation mass replacing most of splenic substance. Internal architecture of cyst is relatively homogeneous, and berders appear fairly smooth. However, there is some subtie inhomogenelty, particularly along lateral aspect of cyst (arrow). B, Sonogram obtained immediately after CT more accurately depicts archftectural changes within this mass. Thickened, irregular septa are present. This case illustrates that traumatic cysts can show complex internal architecture similar to that associated with epidermoid cysts. Findings were confirmed at surgery.
had Increasing pain in left upper
Fig. 9.-Ecchinococcal
cyst. CT scan shows a calcified rim in spleen. Adjacent tiny low-attenuation masses (arrows) represent daughter cysts. These findings suggest an ecchlnococcal cyst, which was proved at surgery. (Courtesy of J. Sty, Milwaukee, WI.)
cystic mass with a partially
Fig. 10.-Splenic pseudocyst. Patient had a history of alcohol abuse. CT shows a lobulated cystic mass that was found at surgery to be an Intra-
splenic pseudocyst.
Fig. 8.-Epidermoid cyst. CT scan through center of markedly enlarged spleen has an appearance similar to that seen in Fig. 7. An epithelial lining was found at surgery, a true or epidermoid cyst.
however,
making
this
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1216
TAYLOR
the enlargement of up to 30% of spleens in lymphoma patients is not due to lymphoma directly but is related to reactive hyperplasia or congestion [2]. Metastatic involvement of the spleen is seen in approximately 2-4% of routine autopsies in patients who died of cancer [3]. Melanoma is the most common source, followed by carcinoma of the lung, breast, gastrointestinal tract, and ovary (Fig. 5). Metastatic deposits to the spleen usually appear late in the course of malignant disease. These deposits may be single or multiple. As in lymphoma, reactive hyperplasia may be the cause of splenic enlargement in cancer patients. Benign tumors of the spleen are rare. The radiologic distinction between benign and malignant lesions is not always clear. Frequently, a splenectomy will be needed to make the final differentiation. The most frequent benign tumors of the spleen are hemangioma, hamartoma, lymphangioma, and epidermoid cyst. Hemangioma and hamartoma may appear as solid or complex masses on CT. The hemangioma will not necessarily show the typical enhancement pattem that is seen in its hepatic counterpart. The lymphangioma usually contains cystic masses, and, at times, septa may be seen within these
cysts (Fig. 6).
ET
AL.
AJR:157,
December
1991
Cysts The majority of splenic “cysts” fall into one of three categories. Most cysts are false and do not have a true epithelial lining. Trauma is the presumed cause, although a supportive history is obtained in only a minority of cases. These cysts may have some calcification within their wall, and they may exhibit trabeculation (Fig. 7). A true cyst, or epidermoid cyst, is the second most common type of cyst (Fig. 8) and is probably developmental. Calcification within the cyst wall may be less prominent, but septa may be more prominent than in
the traumatic usually has and within lobulated if type of cyst the splenic
cyst.
The third type, the ecchinococcal
cyst,
more prominent calcification, both within the wall the cyst itself (Fig. 9). Its margins may be more daughter cysts are present. A fourth, and rarer, is a pancreatic pseudocyst, which dissects into substance (Fig. 10).
Trauma The spleen is the most frequently injured intraabdominal organ in blunt trauma. Owing to the current trend toward a more conservative approach to injury, there has been inFig. 1 1.-Subcapsular hematoma. CT scan shows subcapsular hematoma resulting from surgery on pancreatic flattened medIally
tall. Typical
lenticular
shape
is
as collection begins to recede
during healIng.
Fig. 12.-Laceration. This patient had blunt abdominal trauma hours earlier. On CT scan, a small linear parenchymal defect traversing capsule laterally (solid arrow) represents splenic laceration. Irregular posteromedial margin of spleen with associated perisplenic blood (open arrows) is another manifestation of splenic injury.
Fig.
13.-Fracture.
wide parenchymal
CT scan shows relatively defects, coursing from one cap-
sular surface to another, constituting splenic fractures. These bands, representing blood, are cr1ented in different planes, thus segregating islands of enhancing spleen. lntraperltoneal blood (straight arrow) and left rib fracture (curved arrow)
are also present.
Fig. 14.-Sequential hemorrhage causing an onion-skin appearance. On this CT image, layers of different-attenuation blood clot in perisplenic bed show differences In maturation of blood products after sequential episodes of hemorrhage. More peripheral, high-attenuation clot (solid arrows) in this patient represents mature blood clot. Fluid immediately surrounding spleen (open arrows) is from a more recent episode of hemor-
rhage.
AJR:157,
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creased
December
ACQUIRED
1991
emphasis
on identifying,
staging,
SPLENIC
and follow-up
ABNORMALITIES
in
imaging of splenic trauma. Dynamic contrast-enhanced CT scanning is very sensitive (95%) for detection of splenic injuries. The subcapsular hematoma is a peripheral, welldefined, lenticular, relatively low-attenuation mass that displaces the splenic parenchyma inwardly (Fig. 1 1). Rarely, an intrasplenic contusion or hematoma can be seen as a small, irregular, low-attenuation mass within the splenic parenchyma. Splenic laceration is seen as a cleft, usually with irregular borders, extending through the capsule into the parenchyma (Fig. 1 2). It is associated with perisplenic or intraabdominal fluid. The laceration traversing two capsular surfaces is designated a fracture (Fig. 1 3). Repeated episodes of bleeding may lead to a perisplenic clot with an onion-skin appearance (Fig. 14). More subtle signs of splenic trauma are
a minor surface irregularity, or the presence of a pensplenic clot next to an otherwise normal-appearing spleen, the socalled sentinel clot sign [4]. All of the imaging abnormalities do not necessarily have a direct correlation with a patient’s outcome, either with the need for surgery or with the subsequent development ofdelayed rupture. Pitfalls in the diagnosis of splenic trauma include clefts and a prominent left hepatic
lobe (Fig. 15).
Fig. 15.-Pitfalls in CT of splenic trauma. A, Lateral, low-attenuation crescent (arrows) could be confused with a subcapsular hematoma In this recently injured patient. Note fatty liver. B, On a higher section, crescent is actually part of fatty liver that extends around spleen. Peripheral hepatic vessels (straight solid arrow) and a bridge of liver parenchyma (curved arrow) help to confirm crescent’s true identity. Smooth, congenital splenic clefts (open arrows) are also seen at this level.
Fig. 16.-Physiologic change in size with trauma. A, CT scan in a recently injured patient shows normal-appearing spleen. B, With reversal of transient physiologic changes that may accompany trauma, spleen enlarges to original size 12 days later. There was a 10-mm increase in waist of spleen and a 12-mm Increase In length from tip to tip.
ON
1217
CT
CT can be used to monitor sequential regression of intra-
healing also, evidenced by the and pensplenic clots as well as
the progressive diminution of laceration defects. On followup studies, an enlarging spleen is not necessarily an ominous sign; the spleen may transiently decrease in size shortly after the traumatic event because of the associated decrease in the patient’s intravascular volume or because of the evoked adrenergic response [5]. Subsequent show an increase in splenic size, actually
imaging returning
studies will the splenic
volume to normal (Fig. 16). Rarely, after abdominal causing a severely damaged spleen, splenic tissue scattered
about
the abdomen,
resulting
in a condition
trauma may be called
splenosis. Infarction Splenic
infarction
is a relatively
common
clinical
tion. At times, the acute event causes symptoms
considera-
referable
to
the left upper quadrant. However, splenic infarction may be asymptomatic, with residual features seen on future imaging studies. Splenic infarction is usually the result of local vascular compromise. Frequently, it is caused by arterial emboli (usually from the heart), or from involvement of the local vascular
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1218
TAYLOR
bed by atherosclerosis, arteritis, or RBC sludging. Relative ischemia produced by splenomegaly may also cause infarction. Central inflammatory or neoplastic involvement of the splenic vasculature can also lead to infarction. The classic peripheral, wedge-shaped, low-attenuation defect seen on CT causes no problem in diagnosis. However, the appearance of the infarct can vary. Attenuation can change during maturation; initially, a higher attenuation or a mottled appearance may be present, followed by a progressive decrease in attenuation with age [6]. The shape may vary from spherical or geographic areas of altered texture (Fig. 17). Rarely, the entire spleen may be infarcted, leaving only a rim of enhancing capsule (Fig. 18). Differentiation from splenic abscess, hematoma, or neoplasm usually requires clinical correlation or, if necessary, percutaneous fine-needle aspiration biopsy.
Inflammatory
Changes
The spleen may involved secondarily. abscess formation
be the primary focus of infection or be Primary infections of the spleen with are rare, reported in less than 1% of
ET AL.
AJR:157,
December
1991
autopsy series [7]. Patients at risk frequently have a previously normal spleen with an underlying septic focus, such as bacterial endocarditis, seeding the spleen. Trauma, hematologic malignancy, hemoglobinopathy, IV drug abuse, alcoholism, and other forms of immunocompromised states are all risk factors as well. The study of choice for identification of inflammatory change is CT. Septic involvement of the spleen may occur as a single focus, which is seen as a low-attenuation area on a contrast-enhanced study. Peripheral rim enhancement may or may not be apparent when dynamic scanning techniques are used. Fluid levels, septa, or gas within the splenic mass may be present (Fig. 1 9). Alternatively, numerous, small, low-attenuation areas representing microabscesses may be present within the spleen (Fig. 20). Certain primary infections of the spleen, such as mononucleosis, show only mild to moderate splenomegaly without textural abnormality. Percutaneous aspiration can be used to establish the diagnosis of splenic abscess. Although surgical splenectomy is the treatment of choice for splenic abscess, percutaneous treatment may be used in the unstable patient [7]. More commonly, the spleen is involved with a secondary disease such as pancreatitis. Pancreatitis may cause thromFig. 17.-Infarction.
A 33-year-old
man with sic-
kle cell-hemoglobin C disease had pain in left upper quadrant for 6 days. CT scan shows peripheral crescent of low attenuation with irregular bordora (arrowheads). This geographic pattern is one appearance of infarction.
Fig. 18.-Global infarct. This 23-year-old IV drug abuser had upper quadrant pain. CT scan shows entire spleen is of abnormally low attenuation, except for an enhancing capsule and scattered central high-attenuation islands. This residual capsular enhancement is reminiscent of that seen in renal infarction. Having no septic symptoms, patient was managed conservatively and did well.
I-
#{149}
-.
--:.--
--#{149}
.;.
-
Fig. 19.-Abscess. A, In this febrile patient, CT scan shows a wellcircumscribed, apparently homogeneous mass (arrow) in anterosuperior spleen that could be mistaken for a splenic cyst. B, Sonogram, obtained immediately after CT scan, shows fluid-fluid level. An abscess was confirmed at surgery. This illustrates importance of correlating Imaging and clinical history of patient. (Courtesy of J. Sty, Milwaukee, WI.)
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AJR:157,
December
ACQUIRED
1991
Fig. 20.-Abscess. Another manifestation septic spleen is a myriad of tiny low-attenuation
of
areas, as shown on this CT scan. In this immunocompromised
patient,
pattern
of microabscesses was cultured
suggests fungal infection. Candida from patient.
bosis
of the splenic
vein leading
vessels or, less frequently, enlargement.
Rarely,
splenic
necrosis
ON CT
placed by infected collection with air-fluid level (arrowheads). This resulted from a benign postehor gastric ulcer (open arrows) that perforated spleen. High-attenuation material in splenic abscess (solid arrow) is oral contrast agent.
of collateral
in splenic congestion or hemorrhage
and
occurs.
A pseudocyst may extend from the pancreatic tail into the splenic hilum via the splenorenal ligament and eventually become intrasplenic (Fig. 1 0). Rarely, the spleen may become affected by other adjacent inflammatory processes in the abdomen
ABNORMALITIES
Fig. 21.-Abscess from local inflammatory process. A chronically ill man presented with sepsis. On CT scan, splenic parenchyma is re-
to development
resulting
SPLENIC
(Fig. 21).
1219
Fig. 22.-Sickle cell disease. End-stage spleen In sickle cell disease is usually small or absent. In this adult with sickle cell disease, a CT scan shows size of this diffusely calcified spleen Is preserved. Note Increased attenuation of liver from transfusion hemochromatosis
hemoglobin may cause
C disease or sickle cell-thalassemia disease), mild splenomegaly of normal texture. These spleens are at greater risk than those in patients without hemoglobinopathies for developing complications of infarcts (Fig. 17), abscesses, hemorrhage, or sequestration crises (sudden enlargement of the spleen with a concomitant drop in hematocrit). In hemoglobinopathies leading to severe anemia, the spleen becomes a site of extramedullary hemato-
poiesis. Miscellaneous
Splenic calcifications are a fairly frequent finding on abdominal CT. Most are granulomas, related to prior infections with histoplasmosis or tuberculosis. However, calcifications may occur as the result of a previous traumatic, infectious, or vascular insult. As previously mentioned, some tumors may contain calcifications. In AIDS patients, calcifications may be due to disseminated Pneumocystis carinll infection. Certain hemoglobinopathies, classically, homozygous sickle cell disease, may lead to splenic calcification (Fig. 22). By age 5, the patient with sickle cell disease is functionally asplenic with only residual calcifications. However, sickle cell trait, or a combination of hemoglobinopathies (i.e., sickle cell-
REFERENCES WJ, Taylor AJ, Erickson SJ, Stewart ET, Lawson TL. Radiologic of splenic anomalies. AiR 1990;: 155:805-810 2. Shirkhoda A, Ros R, Farah J, et al. Lymphoma of the solid abdominal 1. Dodds
imaging
viscera. Radio! Gun North Am 1990;28:785-799 3. Morehouse I-IT, Thomhill BA. Splenic disease: a modem approach. Postgrad Radio! 1987;7: 1 12-1 30 4. Orwig D, Federle MP. Localized clotted blood as evidence of visceral trauma on CT: the sentinel clot sign. AJR 1989;153:747-749 5. Goodman LR, Aprahamian C. Changes in splenic size after abdominal trauma. Radio!ogy 1990;176:629-632 6. Balcar I, Seltzer SE, Davis 5, Geller S. CT pattems of splenic infarction: a clinical and experimental study. Radio!ogy 1984;151 :723-729 7. Gleich 5, Wolin DA, Herbsman H. A review of percutaneous drainage in splenic abscess. Surg Gynecol Obstet 1988;167:21 1-216
1213
Pictorial Essay #{149}
#{149}
#{149}
CT of Acquired Andrew
#{149}
Abnormalities
J. Taylor,1 Wylie J. Dodds,
of the Spleen
Scott J. Erickson, and Edward
T. Stewart
Imaging considerations and features when assessing acquired abnormalities of the spleen with CT are described. Indexes of normal size and the implications of splenomegaly are discussed, as well as the CT appearances and types of neoplasia, cysts, traumatic injuries, infarction, and inflammatory changes.
Size
In a recent report, we described the radiologic splenic anatomy, embryology, and developmental
upper limit of normal for splenic size. However, because of wide variation in shape, there is no direct correlation in the
[1]. In this essay, we describe malities
CT findings
Although
features of anomalies
of acquired
spleen’s
abnor-
large
in children,
the
spleen
progres-
length
to its overall
volume
as there
is for other
organs such as the kidney. A product oflength (a craniocaudal measure of approximately 1 2 cm) times depth (an anteroposterior dimension of approximately 7 cm) times width (the thickness at the hilum of about 4 cm) has been used to define
of the spleen.
General
relatively
sively decreases in size with age. In middle-aged patients, the spleen is about the size of a fist, weighting approximately 150 g. A craniocaudal measure of 13 cm is frequently used as the
Considerations
tough capsule, the spleen consists of a lattice of lymphatic follicles and reticuloendothelial cells (white pulp) with interspersed vascular lakes (red pulp). On unenhanced CT scans,
splenic size. Normal limits of this volume range up to 480 cm3 [2]. A more arduous measure of size is adding the volume of each slice on the CT scan. As a practical matter, judgment about the spleen size is usually based on visual inspection and experience.
the spleen has an attenuation similar to that of the liver, approximately 40 H. Normally, the liver and spleen densities are within 1 5 H on unenhanced scans and within 25 H on
The causes of splenomegaly are numerous. The most common cause of splenomegaly in our practice is cirrhosis with its attendant portal hypertension (Fig. 2). Approximately
dynamic contrast-enhanced scans. The spleen generally remains a constant reference point in CT attenuation values, as various metabolic states can decrease (fatty infiltration) or increase (hemochromatosis) the attenuation of the liver. Because of the difference in timing of enhancement of red and white pulp during the early phases of the dynamic contrastenhanced CT, the spleen may be inhomogeneous initially (Fig. 1).These changes vary from subtly to markedly inhomogeneous. Repeating images of the spleen within minutes will show a homogeneous pattern.
30% of splenomegaly cases are caused by lymphoma. AIDS and IV drug abuse increasingly deserve consideration because they cause mild to moderate splenic enlargement either from reactive hyperplasia (Fig. 3) or from complications related
The
largely
characteristics
Received 1
of the
by its underlying
May 6, 1991;
accepted
All authors: Department
Address
reprint
requests
AJR 157:1213-1219,
spleen
histologic
on CT are determined
anatomy.
after revision
of Radiology,
Covered
by a
to these disease complexes. Massive splenomegaly is usually caused by chronic myelogenous leukemia, lymphoma, polycythemia vera, myelofibrosis, or, in the appropriate population of patients, malaria. At times, spontaneous rupture may occur as a complication of splenomegaly, particularly with mononucleosis or leukemia.
July 2, 1991.
Medical College
of Wisconsin,
Froedtert
Memorial
Lutheran
to A. J. Taylor.
December
1991 0361-803X/91/1576-1213C
American
Roentgen
Ray Society
Hospital,
9200
W. Wisconsin
Ave.,
Milwaukee,
WI 53226.
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/21/15 from IP address 128.122.253.228. Copyright ARRS. For personal use only; all rights reserved
1214
TAYLOR
ET
AL.
AJR:157,
December
1991
Fig. 1.-Normal spleen with marked inhomogenefty during early contrast enhancement. A, CT image obtained early during single-level dynamic scanning shows variegated appearance of spleen. (Note lack of hepatlc parenchymal and hepatlc venous enhancement.) B, On an image obtained 35 sec later, spleen is homogeneous.
2.-Cirrhosis. CT scan shows enlarged with homogeneous parenchyma, a manifestation of portal hypertension. Also, note large splenic hilar varices (straight solid white arrows), recanallzed perlumbilical vein (open arrow), nodular liver edge (black arrows), and ascites (curved arrows). Fig. spleen
Fig. 3.-AIDS-related splenomegaly. CT scan shows moderate splenomegaly as part of a generalized lymphoid hyperplasia. No neoplastic or inflammatory cause was found in follow-up.
Fig. 4.-Lymphoma. A, On this CT scan, non-Hodgkin lymphoma is manifested by numerous, small, low-attenuation areas representing nests of tumor. Laterally, these deposits are beginning to coalesce (arrow). B, In another patient, CT scan shows a less common pattern of splenic Iymphoma: discrete large masses within spleen.
Neoplasia Both benign and malignant neoplastic involvement of the spleen occur, although a malignant cause is more frequent. Primary malignant tumors of the spleen, such as angiosarcoma, are rare. Much more common is hematologic malig-
nancy or metastatic disease. Lymphoma is the most common malignant tumor involving the spleen [2]. Approximately one third of all patients with lymphoma (Hodgkin disease and nonHodgkin disease) have splenic involvement, usually with nests of cells smaller than 1 cm in diameter. This infiltrative pattern makes detection of disease difficult on CT (Fig. 4). Conversely,
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/21/15 from IP address 128.122.253.228. Copyright ARRS. For personal use only; all rights reserved
AJR:157,
ACQUIRED
December1991
SPLENIC
ABNORMALITIES
ON
1215
CT
Fig. 5.-Metastatic disease. CT scan shows well-circumscribed low-attenuation splenic mass (open arrow) in patient with ovarian carcinoma. This appearance is typical for splenlc metastases. Other evidence of metastatic spread is usually present; In this case, adenopathy is present in retrocrural space (curved arrow) and gastrohepatic ligament (straight solid arrow).
Fig. 6.-Lymphangioma. CT scan shows wellcircumscribed, low-attenuation masses throughout spleen (arrows). These lesions correlated wIth cystic-appearing lesions seen on sonography. Having these typical findings of lymphangioma,
this 85-year-old tively.
patient
was treated
conserva-
Fig. 7.-Traumatic
cyst. This 23-year-old woman was in an auto accident 7 years earlier and now quadrant. A, CT scan shows markedly enlarged spleen with low-attenuation mass replacing most of splenic substance. Internal architecture of cyst is relatively homogeneous, and berders appear fairly smooth. However, there is some subtie inhomogenelty, particularly along lateral aspect of cyst (arrow). B, Sonogram obtained immediately after CT more accurately depicts archftectural changes within this mass. Thickened, irregular septa are present. This case illustrates that traumatic cysts can show complex internal architecture similar to that associated with epidermoid cysts. Findings were confirmed at surgery.
had Increasing pain in left upper
Fig. 9.-Ecchinococcal
cyst. CT scan shows a calcified rim in spleen. Adjacent tiny low-attenuation masses (arrows) represent daughter cysts. These findings suggest an ecchlnococcal cyst, which was proved at surgery. (Courtesy of J. Sty, Milwaukee, WI.)
cystic mass with a partially
Fig. 10.-Splenic pseudocyst. Patient had a history of alcohol abuse. CT shows a lobulated cystic mass that was found at surgery to be an Intra-
splenic pseudocyst.
Fig. 8.-Epidermoid cyst. CT scan through center of markedly enlarged spleen has an appearance similar to that seen in Fig. 7. An epithelial lining was found at surgery, a true or epidermoid cyst.
however,
making
this
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/21/15 from IP address 128.122.253.228. Copyright ARRS. For personal use only; all rights reserved
1216
TAYLOR
the enlargement of up to 30% of spleens in lymphoma patients is not due to lymphoma directly but is related to reactive hyperplasia or congestion [2]. Metastatic involvement of the spleen is seen in approximately 2-4% of routine autopsies in patients who died of cancer [3]. Melanoma is the most common source, followed by carcinoma of the lung, breast, gastrointestinal tract, and ovary (Fig. 5). Metastatic deposits to the spleen usually appear late in the course of malignant disease. These deposits may be single or multiple. As in lymphoma, reactive hyperplasia may be the cause of splenic enlargement in cancer patients. Benign tumors of the spleen are rare. The radiologic distinction between benign and malignant lesions is not always clear. Frequently, a splenectomy will be needed to make the final differentiation. The most frequent benign tumors of the spleen are hemangioma, hamartoma, lymphangioma, and epidermoid cyst. Hemangioma and hamartoma may appear as solid or complex masses on CT. The hemangioma will not necessarily show the typical enhancement pattem that is seen in its hepatic counterpart. The lymphangioma usually contains cystic masses, and, at times, septa may be seen within these
cysts (Fig. 6).
ET
AL.
AJR:157,
December
1991
Cysts The majority of splenic “cysts” fall into one of three categories. Most cysts are false and do not have a true epithelial lining. Trauma is the presumed cause, although a supportive history is obtained in only a minority of cases. These cysts may have some calcification within their wall, and they may exhibit trabeculation (Fig. 7). A true cyst, or epidermoid cyst, is the second most common type of cyst (Fig. 8) and is probably developmental. Calcification within the cyst wall may be less prominent, but septa may be more prominent than in
the traumatic usually has and within lobulated if type of cyst the splenic
cyst.
The third type, the ecchinococcal
cyst,
more prominent calcification, both within the wall the cyst itself (Fig. 9). Its margins may be more daughter cysts are present. A fourth, and rarer, is a pancreatic pseudocyst, which dissects into substance (Fig. 10).
Trauma The spleen is the most frequently injured intraabdominal organ in blunt trauma. Owing to the current trend toward a more conservative approach to injury, there has been inFig. 1 1.-Subcapsular hematoma. CT scan shows subcapsular hematoma resulting from surgery on pancreatic flattened medIally
tall. Typical
lenticular
shape
is
as collection begins to recede
during healIng.
Fig. 12.-Laceration. This patient had blunt abdominal trauma hours earlier. On CT scan, a small linear parenchymal defect traversing capsule laterally (solid arrow) represents splenic laceration. Irregular posteromedial margin of spleen with associated perisplenic blood (open arrows) is another manifestation of splenic injury.
Fig.
13.-Fracture.
wide parenchymal
CT scan shows relatively defects, coursing from one cap-
sular surface to another, constituting splenic fractures. These bands, representing blood, are cr1ented in different planes, thus segregating islands of enhancing spleen. lntraperltoneal blood (straight arrow) and left rib fracture (curved arrow)
are also present.
Fig. 14.-Sequential hemorrhage causing an onion-skin appearance. On this CT image, layers of different-attenuation blood clot in perisplenic bed show differences In maturation of blood products after sequential episodes of hemorrhage. More peripheral, high-attenuation clot (solid arrows) in this patient represents mature blood clot. Fluid immediately surrounding spleen (open arrows) is from a more recent episode of hemor-
rhage.
AJR:157,
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creased
December
ACQUIRED
1991
emphasis
on identifying,
staging,
SPLENIC
and follow-up
ABNORMALITIES
in
imaging of splenic trauma. Dynamic contrast-enhanced CT scanning is very sensitive (95%) for detection of splenic injuries. The subcapsular hematoma is a peripheral, welldefined, lenticular, relatively low-attenuation mass that displaces the splenic parenchyma inwardly (Fig. 1 1). Rarely, an intrasplenic contusion or hematoma can be seen as a small, irregular, low-attenuation mass within the splenic parenchyma. Splenic laceration is seen as a cleft, usually with irregular borders, extending through the capsule into the parenchyma (Fig. 1 2). It is associated with perisplenic or intraabdominal fluid. The laceration traversing two capsular surfaces is designated a fracture (Fig. 1 3). Repeated episodes of bleeding may lead to a perisplenic clot with an onion-skin appearance (Fig. 14). More subtle signs of splenic trauma are
a minor surface irregularity, or the presence of a pensplenic clot next to an otherwise normal-appearing spleen, the socalled sentinel clot sign [4]. All of the imaging abnormalities do not necessarily have a direct correlation with a patient’s outcome, either with the need for surgery or with the subsequent development ofdelayed rupture. Pitfalls in the diagnosis of splenic trauma include clefts and a prominent left hepatic
lobe (Fig. 15).
Fig. 15.-Pitfalls in CT of splenic trauma. A, Lateral, low-attenuation crescent (arrows) could be confused with a subcapsular hematoma In this recently injured patient. Note fatty liver. B, On a higher section, crescent is actually part of fatty liver that extends around spleen. Peripheral hepatic vessels (straight solid arrow) and a bridge of liver parenchyma (curved arrow) help to confirm crescent’s true identity. Smooth, congenital splenic clefts (open arrows) are also seen at this level.
Fig. 16.-Physiologic change in size with trauma. A, CT scan in a recently injured patient shows normal-appearing spleen. B, With reversal of transient physiologic changes that may accompany trauma, spleen enlarges to original size 12 days later. There was a 10-mm increase in waist of spleen and a 12-mm Increase In length from tip to tip.
ON
1217
CT
CT can be used to monitor sequential regression of intra-
healing also, evidenced by the and pensplenic clots as well as
the progressive diminution of laceration defects. On followup studies, an enlarging spleen is not necessarily an ominous sign; the spleen may transiently decrease in size shortly after the traumatic event because of the associated decrease in the patient’s intravascular volume or because of the evoked adrenergic response [5]. Subsequent show an increase in splenic size, actually
imaging returning
studies will the splenic
volume to normal (Fig. 16). Rarely, after abdominal causing a severely damaged spleen, splenic tissue scattered
about
the abdomen,
resulting
in a condition
trauma may be called
splenosis. Infarction Splenic
infarction
is a relatively
common
clinical
tion. At times, the acute event causes symptoms
considera-
referable
to
the left upper quadrant. However, splenic infarction may be asymptomatic, with residual features seen on future imaging studies. Splenic infarction is usually the result of local vascular compromise. Frequently, it is caused by arterial emboli (usually from the heart), or from involvement of the local vascular
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1218
TAYLOR
bed by atherosclerosis, arteritis, or RBC sludging. Relative ischemia produced by splenomegaly may also cause infarction. Central inflammatory or neoplastic involvement of the splenic vasculature can also lead to infarction. The classic peripheral, wedge-shaped, low-attenuation defect seen on CT causes no problem in diagnosis. However, the appearance of the infarct can vary. Attenuation can change during maturation; initially, a higher attenuation or a mottled appearance may be present, followed by a progressive decrease in attenuation with age [6]. The shape may vary from spherical or geographic areas of altered texture (Fig. 17). Rarely, the entire spleen may be infarcted, leaving only a rim of enhancing capsule (Fig. 18). Differentiation from splenic abscess, hematoma, or neoplasm usually requires clinical correlation or, if necessary, percutaneous fine-needle aspiration biopsy.
Inflammatory
Changes
The spleen may involved secondarily. abscess formation
be the primary focus of infection or be Primary infections of the spleen with are rare, reported in less than 1% of
ET AL.
AJR:157,
December
1991
autopsy series [7]. Patients at risk frequently have a previously normal spleen with an underlying septic focus, such as bacterial endocarditis, seeding the spleen. Trauma, hematologic malignancy, hemoglobinopathy, IV drug abuse, alcoholism, and other forms of immunocompromised states are all risk factors as well. The study of choice for identification of inflammatory change is CT. Septic involvement of the spleen may occur as a single focus, which is seen as a low-attenuation area on a contrast-enhanced study. Peripheral rim enhancement may or may not be apparent when dynamic scanning techniques are used. Fluid levels, septa, or gas within the splenic mass may be present (Fig. 1 9). Alternatively, numerous, small, low-attenuation areas representing microabscesses may be present within the spleen (Fig. 20). Certain primary infections of the spleen, such as mononucleosis, show only mild to moderate splenomegaly without textural abnormality. Percutaneous aspiration can be used to establish the diagnosis of splenic abscess. Although surgical splenectomy is the treatment of choice for splenic abscess, percutaneous treatment may be used in the unstable patient [7]. More commonly, the spleen is involved with a secondary disease such as pancreatitis. Pancreatitis may cause thromFig. 17.-Infarction.
A 33-year-old
man with sic-
kle cell-hemoglobin C disease had pain in left upper quadrant for 6 days. CT scan shows peripheral crescent of low attenuation with irregular bordora (arrowheads). This geographic pattern is one appearance of infarction.
Fig. 18.-Global infarct. This 23-year-old IV drug abuser had upper quadrant pain. CT scan shows entire spleen is of abnormally low attenuation, except for an enhancing capsule and scattered central high-attenuation islands. This residual capsular enhancement is reminiscent of that seen in renal infarction. Having no septic symptoms, patient was managed conservatively and did well.
I-
#{149}
-.
--:.--
--#{149}
.;.
-
Fig. 19.-Abscess. A, In this febrile patient, CT scan shows a wellcircumscribed, apparently homogeneous mass (arrow) in anterosuperior spleen that could be mistaken for a splenic cyst. B, Sonogram, obtained immediately after CT scan, shows fluid-fluid level. An abscess was confirmed at surgery. This illustrates importance of correlating Imaging and clinical history of patient. (Courtesy of J. Sty, Milwaukee, WI.)
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AJR:157,
December
ACQUIRED
1991
Fig. 20.-Abscess. Another manifestation septic spleen is a myriad of tiny low-attenuation
of
areas, as shown on this CT scan. In this immunocompromised
patient,
pattern
of microabscesses was cultured
suggests fungal infection. Candida from patient.
bosis
of the splenic
vein leading
vessels or, less frequently, enlargement.
Rarely,
splenic
necrosis
ON CT
placed by infected collection with air-fluid level (arrowheads). This resulted from a benign postehor gastric ulcer (open arrows) that perforated spleen. High-attenuation material in splenic abscess (solid arrow) is oral contrast agent.
of collateral
in splenic congestion or hemorrhage
and
occurs.
A pseudocyst may extend from the pancreatic tail into the splenic hilum via the splenorenal ligament and eventually become intrasplenic (Fig. 1 0). Rarely, the spleen may become affected by other adjacent inflammatory processes in the abdomen
ABNORMALITIES
Fig. 21.-Abscess from local inflammatory process. A chronically ill man presented with sepsis. On CT scan, splenic parenchyma is re-
to development
resulting
SPLENIC
(Fig. 21).
1219
Fig. 22.-Sickle cell disease. End-stage spleen In sickle cell disease is usually small or absent. In this adult with sickle cell disease, a CT scan shows size of this diffusely calcified spleen Is preserved. Note Increased attenuation of liver from transfusion hemochromatosis
hemoglobin may cause
C disease or sickle cell-thalassemia disease), mild splenomegaly of normal texture. These spleens are at greater risk than those in patients without hemoglobinopathies for developing complications of infarcts (Fig. 17), abscesses, hemorrhage, or sequestration crises (sudden enlargement of the spleen with a concomitant drop in hematocrit). In hemoglobinopathies leading to severe anemia, the spleen becomes a site of extramedullary hemato-
poiesis. Miscellaneous
Splenic calcifications are a fairly frequent finding on abdominal CT. Most are granulomas, related to prior infections with histoplasmosis or tuberculosis. However, calcifications may occur as the result of a previous traumatic, infectious, or vascular insult. As previously mentioned, some tumors may contain calcifications. In AIDS patients, calcifications may be due to disseminated Pneumocystis carinll infection. Certain hemoglobinopathies, classically, homozygous sickle cell disease, may lead to splenic calcification (Fig. 22). By age 5, the patient with sickle cell disease is functionally asplenic with only residual calcifications. However, sickle cell trait, or a combination of hemoglobinopathies (i.e., sickle cell-
REFERENCES WJ, Taylor AJ, Erickson SJ, Stewart ET, Lawson TL. Radiologic of splenic anomalies. AiR 1990;: 155:805-810 2. Shirkhoda A, Ros R, Farah J, et al. Lymphoma of the solid abdominal 1. Dodds
imaging
viscera. Radio! Gun North Am 1990;28:785-799 3. Morehouse I-IT, Thomhill BA. Splenic disease: a modem approach. Postgrad Radio! 1987;7: 1 12-1 30 4. Orwig D, Federle MP. Localized clotted blood as evidence of visceral trauma on CT: the sentinel clot sign. AJR 1989;153:747-749 5. Goodman LR, Aprahamian C. Changes in splenic size after abdominal trauma. Radio!ogy 1990;176:629-632 6. Balcar I, Seltzer SE, Davis 5, Geller S. CT pattems of splenic infarction: a clinical and experimental study. Radio!ogy 1984;151 :723-729 7. Gleich 5, Wolin DA, Herbsman H. A review of percutaneous drainage in splenic abscess. Surg Gynecol Obstet 1988;167:21 1-216
