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805
Pictorial
Essay
1
Radiologic Wylie
J. Dodds,1
Imaging Andrew
J. Taylor,
of Splenic Scott
J. Erickson,
Anomalies Edward
T. Stewart,
and Thomas
L. Lawson
Knowledge of the anatomy, embryology, and congenital anomalies of the spleen is needed in order to avoid pitfalls in the interpretation of abdominal imaging studies such as CT and sonography. For this reason, this pictorial essay illustrates the anatomy, embryology, and radiologic images of congenital anom-
along the superior border of the splenic hilum (Fig. 3). Short gastric the gastrosplenic ligament.
alies
Embryology
of the
spleen.
In a 4- to 5-week embryo (Fig. 4A), the stomach is suspended by a ventral mesentery (ventral mesogastrium) and dorsal mesentery (dorsal mesogastrium). During the fifth week, the spleen develops in the dorsal mesogastrium from mesenchymal cells that migrate between the leaves of the
Anatomy As the largest unit of lymphatic tissue in the body, the spleen is a solid alimentary-tract organ located in the lateral posterior part of the left upper abdomen [1 ]. It is generally shaped like a curved wedge with a convex superior diaphragmatic surface, a gastric impression on its upper medial border,
a renal impression
along
its lower
medial
margin,
and, fre-
quently, a colonic impression at its inferior margin (Fig. 1). The pancreatic tail often abuts against and indents the spleen at its hilum (Fig. 2). In supine adults, the spleen lies in the left subphrenic space, posterolateral to the stomach. Its anterior margin seldom projects ventral to the anterior axillary line, while its blunt posterior border generally lies within 3-4 cm of the lumbar spine (Fig. 2). The long axis of the spleen parallels the tenth rib. The left lateral pulmonary diaphragmatic recess frequently extends caudad as far as the inferior border of the spleen. This fact should be considered when performing percutaneous
biopsy
or drainage
of splenic
lesions.
The
Gastric Impression
Ren
Pancreatic
1
April 2, 1990;
All authors:
Radiology,
Froedtert
AJR 155:805-810,
accepted
Department Memorial October
after revision
of Radiology, Lutheran
1990 0361 -803X/90/1
- Anterior
Impressen
Margin
Fig. 1.-Drawing
of splenic anatomy.
is a right anterior oblique view. and constitutes about 30-40%
Spleen seen from its medial border Note that splenic hilum is vertically oriented of vertical height of spleen.
May 20, 1990.
the Medical Hospital,
Impressn
in-
ferior splenic border often nestles against and is supported by the phrenocolic ligament. Located within the dorsal gastric mesentery, the spleen divides this mesentery into the gastrosplenic and splenorenal ligaments [2, 3]. Thus, the spleen and its ligaments form the lateral margin of the lesser peritoneal sac [3]. The splenic vessels, lymphatics, and nerves course Received
pancreas [4] to enter the vessels are located within
9200
College
of Wisconsin,
W. Wisconsin
554-0805
Ave.,
© American
Milwaukee, Milwaukee,
Roentgen
WI 53226.
WI 53226. Ray Society
Address
reprint
requests
to W. J. Dodds,
Department
of
806
DODDS
ET AL.
AJR:155,
October
1990
Fig. 2.-CT images of normal spleen from two patients. A, Location of spleen in left upper quadrant. Commonly, normal spleen has a kidney bean or boomerang shape on cross section. It comprises
a posterior part dorsal to stomach and an anterior
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part lateral
to stomach.
Rounded
medial
margin
of
posterior spleen is commonly within 3-4 cm of spine, whereas anterior margin of spleen rarely projects ventral to anterior axillary line. B, Relationship of pancreatic tail to spleen. As in this example, pancreatic tail commonly passes through splenorenal ligament to abut spleen at its
hilum. This anatomy
provides
inflammatory or neoplastic creatic tail to invade spleen.
Fig. 3.-Splenic
artery
a direct pathway processes
for
of
pan-
(SA) and splenic
vein
(SV) are seen to course along cephalic margin of pancreatic body to enter spleen at its hilum. St = stomach, Sp = spleen, P = pancreas, A = aorta, vC = vena cava, PV = portal vein.
mesentery
and
[2]. Thus,
coalesce
alimentary-tract structure that the gut or one of its anlagen. stomach enlarges and rotates larges and rotates to the right. swings to the left [3] to form
4B). Subsequently, lies against
a short
is the only
the most dorsal part of the mesogastrium
and fuses
residual
the spleen
does not develop directly from During the next 4-5 weeks, the to the left while the liver enThus, the dorsal mesogastrium the lesser peritoneal sac (Fig.
with
mesentery,
the posterior
peritoneum
to leave
called the splenorenal
ligament
4C). The location of the original mesentery is evident by the course of the splenic vessels that lie within the secondary anterior space of the left retroperitoneum [5]. The splenic
(Fig.
vessels
lie just cephalad
to the pancreas
and enter the spleen
through the splenorenal ligament (Fig. 3). Variation exists in the splenorenal ligament, the
extent
of fusion
of the
mesogastrium
with
depending the
posterior
on
peritoneum. The splenorenal ligament may persist narrow strut that creates a small bare area over margin
of the
spleen
(Fig.
5) or as a long
mesentery.
as a short, the medial The
tail
of the pancreas, located within the dorsal mesentery of the duodenum at a level slightly caudad to the spleen (Fig. 6), is commonly located within the splenorenal ligament and abuts the splenic hilum (Fig. 2A). Because the pancreatic tail is located within the splenorenal ligament, inflammatory or neoplastic processes of the pancreatic tail may extend directly into
the spleen
Congenital
(Fig.
7).
Anomalies
Splenic clefts, notches, or lobulations that persist from fetal lobulations should not be mistaken for splenic fractures due to trauma. Clefts usually occur on the diaphragmatic surface
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AJR:155,
October
SPLENIC
1990
A
ANOMALIES
807
Fig. 5.-Abdominal CT scan of splenorenal ligament of patient with recurrent pancreatitis and ascites. A 4-cm pseudocyst is seen interposed botween pancreatic body and stomach. Ascitic fluid in greater peritoneal cavity and lesser peritoneal sac outlines ruffled gastrosplenic ligament (curved arrow). A short splenorenal ligament (straight arrows) contains splenic vessels.
B
Fig. 6.-Upper
abdomen
in 8-week
embryo.
Liver (L) swings
to right
while stomach (St.), spleen (Sp), and dorsal pancreas (DP) swing leftward. Ventral pancreas (VP) anlage is seen slightly caudad to dorsal pancreas. Spleen and dorsal pancreas are in common dorsal mesentery of stomach and duodenum. This embryologic anatomy explains why pancreatic tail commonly runs through splenorenal ligament to abut on splenic hilum. Normally, dorsal duodenal mesentery folds against and fuses with postenor peritoneum so that pancreatic body becomes a secondary retroperitoneal structure. Ant. = anterior, Post. = posterior. (Modified and reprinted from Dodds et al. [5].)
C Fig. 4.-Schematic
cross
sections
of upper abdomen
of embryo
and
fetus. A, 5-week embryo. Stomach is supported by a dorsal mesentery (dorsal mesogastrium) and ventral mesentery (ventral mesogastrium). Spleen develops within dorsal mesogastrium while liver develops within ventral mesogastrium. B, 8-week embryo. As liver enlarges and swings to right, spleen and stomach swing leftward to form lesser peritoneal sac. Liver divides ventral
mesogastrium
into falciform
divides
mesogastrium into gastrosplenic (4), part of which will become
dorsal
mesogastrium
(1) and gastrohepatic
(2) ligaments.
Spleen
ligament (3) part of dorsal splenorenal ligament. This
ligament normally lies against and fuses with posterior peritoneum to form short splenorenal ligament. Failure of this fusion leads to a long splenic mesentery and a wandering spleen. C, Mature fetus. Almost all of posterior part of dorsal mesogastrium has fused with posterior peritoneum to leave a short splenorenal ligament (4). Gastrosplenic ligament, spleen, and splenorenal ligament form lateral margin of lesser peritoneal sac. L = liver, Sp = spleen, S = stomach, K = kidney, I = falciform ligament, 2 = gastrohepatic ligament, 3 = gastrosplenic ligament, 4 = splenorenal ligament. (Modified and reprinted from Dodds et al. [3].)
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808
DODDS
ET AL.
AJR:155,
October
1990
Fig. 7.-Disease invading spleen via splenorenal ligament on contrast-enhanced CT scans. Commonly, pancreas passes through splenorenal ligament to abut against hilum of spleen. Consequently, disease processes of pancreatic tail have access to a direct pathway to spleen. A, Pseudocyst (arrow) originating from pancreatic tail has extended into lower margin of splenic hilum. B, Carcinoma originating from tail of pancreas has invaded hilar area of spleen (arrows). Metastatic areas of low attenuation are seen in liver.
A
Fig. 8.-Example of splenic clefts on contrastenhanced abdominal CT scan. Two congenital clefts (arrows) are seen.
of the spleen medial part bus splenic
(Fig.
of the artery
8), whereas spleen and may (Fig. 9). Some
B
Fig. 9.-Example of splenic lobulation on a celiac arteriogram. A, Arterial phase. Accessory segmental artery (arrow) supplies upper medial margin of spleen. B, Capillary phase. Spleen exhibits a large lobulation (arrow) at its mediosuperior border.
lobulations occur along the be supplied by an anomalobulations cause a worn-
some extrinsic gastric impression. One or more accessory spleens, on splenculi, are present in about 1 0% of the population. Accessory spleens are most often located in the vicinity of the splenic hilum (Fig. 10), along the course of the splenic vessels, or within the gastrosplenic ligament or omentum, but they may occur anywhere in the abdomen. Accessory spleens may be single or multiple, but there are seldom more than six (Fig. 1 1). Characteristically, they are smooth with a round or oval shape and are about 1 .0-1 .5 cm in diameter. Because accessory spleens frequently overlap the pancreas and show a homogeneous stain on arteniography, they must be distinguished from an isletcell pancreatic tumor on angiography. On CT, their characteristic appearance and location within the embryologic dorsal mesenteny of the stomach and pancreas (Fig. 6) generally distinguish them from enlarged lymph nodes. Occasionally, an accessory spleen may be embedded along the greater curvature of the stomach to form an intramural mass. When
a splenectomy spleens should the
main
spleen
is done for a blood dyscrasia, all accessory be removed because they may enlarge once is removed.
Definitive
identification
of
an
accessory spleen is accomplished by a liver-spleen scan with technetium sulfur colloid, which labels splenic reticuloendothelial cells as well as those in the liver. Oblique views may be required. In some individuals, the dorsal part of the gastric mesentery (Fig. 4B) may not fuse with the dorsal peritoneum and thereby persist as a long mesentery. This anomaly results in a “wandening spleen,” which is highly mobile and may rotate to the center of the abdomen (Fig. 1 2). Frequently, the tail of the pancreas lies within the long splenic mesentery because of the proximity of the dorsal mesentery of the pancreas to the dorsal mesentery of the spleen during the first trimester of gestation (Fig. 6). A wandering spleen is often discovered as an asymptomatic mass in the anterior abdomen. Diagnostic evaluation by sonography, CT, or hepatic radionuclide scanning discloses that a normal spleen is not present in its typical location. Other confirmatory evidence of the diagnosis is that the splenic vessels pass to the ectopic mass. In some in-
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AJR:155,
October
SPLENIC
1990
Fig. 10.-Accessory
spleen
on slightly
oblique
Fig. 1 1.-Accessory
ANOMALIES
spleens
809
on contrast-enhanced
abdominal
CT scans.
A, Solitary accessory spleen (arrow) is located lateral to kidney and caudad to main spleen (not shown). Accessory spleen, a smooth 1.5-cm mass, had same attenuation as main spleen. Accessory
coronal view obtained by placing transducer head between ninth and tenth ribs in mid axillary line. Spleen acts as sonographic window. Splenic vein (curved arrow) is seen entering hilum of spleen. A sharply defined 2- by 3-cm mass (straight arrows) shows same echogenic characteristics as spleen, and is identified adjacent to inferior margin of splenic hilum. This mass, judged to bo an accessory spleen, was confirmed on abdominal CT.
spleen is located within original dorsal mesentery to stomach or duodenum. B, Multiple accessory spleens. On this CT image, three accessory spleens (arrow) of gastrorenal ligament. Three additional accessory spleens main spleen was absent. This patient did not have congenital
were present at more heart disease.
are seen in fat caudal
levels.
A
4 Fig. 12.-Ectopic
wandering
scintigram obtained soft midline mass
spleen on hepatic
Fig. 13.-Torsion and ischemic infarction of a wandering spleen. A, Contrast-enhanced CT scan bolow level of liver. Unenhanced mass (arrows), representing infarcted wandering spleen, is seen on left side of abdomen. B, Hepatic scintigram. Anterior view shows normal-appearing liver in upper abdomen, whereas
to evaluate asymptomatic, in middle abdomen that was
discovered on a routine physical examination. Anterior view shows normal-appearing liver in upper abdomen. Ventral wandering spleen (arrow) is seen in midline, just caudad to liver. A normal spleen
is not seen
stances, mesentery.
mia,
in left upper
a wandering Such
and the acute
CT, the ischemic
quadrant.
spleen
torsion
onset
spleen
spleen is not imaged.
undergoes
causes
vascular
of abdominal
does
a volvulus pain.
not enhance
injection (Fig. 1 3A). Also, a normal spleen, ischemic spleen, does not show radioactive isotope scan (Fig. 1 3B). Several congenital cardiosplenic syndromes consist
of complex
cardiac
malformations,
on its long
compromise,
ische-
On abdominal
after contrast as well uptake
as the on an
may occur
splenic
that
anomalies,
and intermediate situs. The asplenia type, predominant in females, has bilateral right-sided features of a horizontal midline liver, Howell-Jolly bodies in the peripheral blood resuIting from asplenia, and bilateral right lung morphology. The
polysplenic bilateral bladder
type, (Fig. 14), which occurs
be associated tract.
mainly in males, has
left-sided features consisting of absence and bilateral left lung morphology. Both The
with situs
asplenic
type
ambiguous is associated
of a galltypes may
of the gastrointestinal with
cyanotic
heart
DODDS
810
ET AL.
AJR:155, October 1990
Fig. 14.-Polysplenic cardiosplenic syndrome in child with complex congenital cardiac anomalies and polysplenism. A, Parasagittal sonogram through left kidney. Two round, 5- to 6-cm masses (asterisks) representing multiple spleens are seen Immediately
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ventralto
kidney. A third spleen was identified just
cephalad, but a normal-sized spleen was absent. B, Liver-spleen scintigram. Liver appears normal. Three spleens (asterisks) are seen in left upper abdomen.
Fig. 15.-Spleen (asterisk) located in eventration of left hemidiaphragm is seen on abdominal CT scan obtained to exclude malignancy in 20year-old patient. Diaphragmatic eventration was judged to bo congenital.
Fig. 16.-Anomalous bohind 15
location
of spleen (arrow)
left kidney.
16
disease and a poor prognosis. The spleen or spleens be sought mainly in the upper quadrant ipsilateral stomach because the spleen develops in the dorsal
should to the gastric
A relatively
mesentery.
Another
congenital
splenogonadal
syndrome,
anomaly wherein
involving
the
spleen
an association
is the
exists
be-
splenic and gonadal tissue [6]. In the first trimester of pregnancy, the developing anlage of the spleen and left gonadal anlage lie in close apposition (Fig. 4) when partial fusion occurs between the dorsal mesogastrium and left posterior penitoneum. At about 9 weeks of gestation, the left gonadal anlage begins to migrate toward the pelvis. A discontinuous type of splenogonadal anomaly occurs when some splenic tissue migrates with gonadal tissue. In this case, a normal single spleen is present in the left upper abdomen. In the continuous type of splenogonadal anomaly, a cord of splenic or fibrous tissue connects a normally located spleen with the testes, epididymis, ovary, or mesovarium. In males, left-sided cryptorchidism is present. Existence of the splenogonadal syndrome is generally documented as an unsuspected finding in individuals undergoing surgery for other tween
reasons,
identified on sonography in utero or diagnosed Children or young adults may exhibit congenital eventration (Fig. 15) or herniation.
such as a splenectomy
or oophorectomy.
Congenital herniation of the left hemidiaphragm may involve the spleen as well as the intestine. Such hemiations may be
posterior
common
location
congenital
of the spleen
16). This circumstance
anomaly behind
may occur
is a pronounced
the
when
in the neonate. diaphragmatic
left kidney
(Fig.
a deep penitoneal
lateral recess persists that is filled by the spleen or intestine [5]. Importantly, this anatomic anomaly must be considered when doing a percutaneous puncture for placement of a nephrostomy tube in the left kidney.
REFERENCES 1 . Goss CM, ed. Anatomy Febiger,
of the human
body,
28th ed. Philadelphia:
2. Moore KL, ed. The developing human: clinically oriented ed. Philadelphia: Saunders, 1977 3. Dodds WJ, Foley WD, Lawson TL, Stewart ET, Taylor imaging
Lea &
1966
of the lesser
peritoneal
sac. AJR
embryology,
2nd
A. Anatomy
and
1985;144:567-575
4. Netter FH. Upperdigestivetract. In: OppenheimerE, ed. TheCiba collection of medical illustrations, vol 3. Digestive system, part 1 . New York: Ciba, 1962 5. Dodds WJ, Darweesh RMA, Lawson TL, et al. The retropentoneal spaces revisited. AJR 1986;147: 1155-1161 6. Sty JR, Conway JJ. The spleen: development and functional evaluation. Semin NucI Med 1985;15:276-298
805
Pictorial
Essay
1
Radiologic Wylie
J. Dodds,1
Imaging Andrew
J. Taylor,
of Splenic Scott
J. Erickson,
Anomalies Edward
T. Stewart,
and Thomas
L. Lawson
Knowledge of the anatomy, embryology, and congenital anomalies of the spleen is needed in order to avoid pitfalls in the interpretation of abdominal imaging studies such as CT and sonography. For this reason, this pictorial essay illustrates the anatomy, embryology, and radiologic images of congenital anom-
along the superior border of the splenic hilum (Fig. 3). Short gastric the gastrosplenic ligament.
alies
Embryology
of the
spleen.
In a 4- to 5-week embryo (Fig. 4A), the stomach is suspended by a ventral mesentery (ventral mesogastrium) and dorsal mesentery (dorsal mesogastrium). During the fifth week, the spleen develops in the dorsal mesogastrium from mesenchymal cells that migrate between the leaves of the
Anatomy As the largest unit of lymphatic tissue in the body, the spleen is a solid alimentary-tract organ located in the lateral posterior part of the left upper abdomen [1 ]. It is generally shaped like a curved wedge with a convex superior diaphragmatic surface, a gastric impression on its upper medial border,
a renal impression
along
its lower
medial
margin,
and, fre-
quently, a colonic impression at its inferior margin (Fig. 1). The pancreatic tail often abuts against and indents the spleen at its hilum (Fig. 2). In supine adults, the spleen lies in the left subphrenic space, posterolateral to the stomach. Its anterior margin seldom projects ventral to the anterior axillary line, while its blunt posterior border generally lies within 3-4 cm of the lumbar spine (Fig. 2). The long axis of the spleen parallels the tenth rib. The left lateral pulmonary diaphragmatic recess frequently extends caudad as far as the inferior border of the spleen. This fact should be considered when performing percutaneous
biopsy
or drainage
of splenic
lesions.
The
Gastric Impression
Ren
Pancreatic
1
April 2, 1990;
All authors:
Radiology,
Froedtert
AJR 155:805-810,
accepted
Department Memorial October
after revision
of Radiology, Lutheran
1990 0361 -803X/90/1
- Anterior
Impressen
Margin
Fig. 1.-Drawing
of splenic anatomy.
is a right anterior oblique view. and constitutes about 30-40%
Spleen seen from its medial border Note that splenic hilum is vertically oriented of vertical height of spleen.
May 20, 1990.
the Medical Hospital,
Impressn
in-
ferior splenic border often nestles against and is supported by the phrenocolic ligament. Located within the dorsal gastric mesentery, the spleen divides this mesentery into the gastrosplenic and splenorenal ligaments [2, 3]. Thus, the spleen and its ligaments form the lateral margin of the lesser peritoneal sac [3]. The splenic vessels, lymphatics, and nerves course Received
pancreas [4] to enter the vessels are located within
9200
College
of Wisconsin,
W. Wisconsin
554-0805
Ave.,
© American
Milwaukee, Milwaukee,
Roentgen
WI 53226.
WI 53226. Ray Society
Address
reprint
requests
to W. J. Dodds,
Department
of
806
DODDS
ET AL.
AJR:155,
October
1990
Fig. 2.-CT images of normal spleen from two patients. A, Location of spleen in left upper quadrant. Commonly, normal spleen has a kidney bean or boomerang shape on cross section. It comprises
a posterior part dorsal to stomach and an anterior
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part lateral
to stomach.
Rounded
medial
margin
of
posterior spleen is commonly within 3-4 cm of spine, whereas anterior margin of spleen rarely projects ventral to anterior axillary line. B, Relationship of pancreatic tail to spleen. As in this example, pancreatic tail commonly passes through splenorenal ligament to abut spleen at its
hilum. This anatomy
provides
inflammatory or neoplastic creatic tail to invade spleen.
Fig. 3.-Splenic
artery
a direct pathway processes
for
of
pan-
(SA) and splenic
vein
(SV) are seen to course along cephalic margin of pancreatic body to enter spleen at its hilum. St = stomach, Sp = spleen, P = pancreas, A = aorta, vC = vena cava, PV = portal vein.
mesentery
and
[2]. Thus,
coalesce
alimentary-tract structure that the gut or one of its anlagen. stomach enlarges and rotates larges and rotates to the right. swings to the left [3] to form
4B). Subsequently, lies against
a short
is the only
the most dorsal part of the mesogastrium
and fuses
residual
the spleen
does not develop directly from During the next 4-5 weeks, the to the left while the liver enThus, the dorsal mesogastrium the lesser peritoneal sac (Fig.
with
mesentery,
the posterior
peritoneum
to leave
called the splenorenal
ligament
4C). The location of the original mesentery is evident by the course of the splenic vessels that lie within the secondary anterior space of the left retroperitoneum [5]. The splenic
(Fig.
vessels
lie just cephalad
to the pancreas
and enter the spleen
through the splenorenal ligament (Fig. 3). Variation exists in the splenorenal ligament, the
extent
of fusion
of the
mesogastrium
with
depending the
posterior
on
peritoneum. The splenorenal ligament may persist narrow strut that creates a small bare area over margin
of the
spleen
(Fig.
5) or as a long
mesentery.
as a short, the medial The
tail
of the pancreas, located within the dorsal mesentery of the duodenum at a level slightly caudad to the spleen (Fig. 6), is commonly located within the splenorenal ligament and abuts the splenic hilum (Fig. 2A). Because the pancreatic tail is located within the splenorenal ligament, inflammatory or neoplastic processes of the pancreatic tail may extend directly into
the spleen
Congenital
(Fig.
7).
Anomalies
Splenic clefts, notches, or lobulations that persist from fetal lobulations should not be mistaken for splenic fractures due to trauma. Clefts usually occur on the diaphragmatic surface
Downloaded from www.ajronline.org by 117.253.242.224 on 11/06/15 from IP address 117.253.242.224. Copyright ARRS. For personal use only; all rights reserved
AJR:155,
October
SPLENIC
1990
A
ANOMALIES
807
Fig. 5.-Abdominal CT scan of splenorenal ligament of patient with recurrent pancreatitis and ascites. A 4-cm pseudocyst is seen interposed botween pancreatic body and stomach. Ascitic fluid in greater peritoneal cavity and lesser peritoneal sac outlines ruffled gastrosplenic ligament (curved arrow). A short splenorenal ligament (straight arrows) contains splenic vessels.
B
Fig. 6.-Upper
abdomen
in 8-week
embryo.
Liver (L) swings
to right
while stomach (St.), spleen (Sp), and dorsal pancreas (DP) swing leftward. Ventral pancreas (VP) anlage is seen slightly caudad to dorsal pancreas. Spleen and dorsal pancreas are in common dorsal mesentery of stomach and duodenum. This embryologic anatomy explains why pancreatic tail commonly runs through splenorenal ligament to abut on splenic hilum. Normally, dorsal duodenal mesentery folds against and fuses with postenor peritoneum so that pancreatic body becomes a secondary retroperitoneal structure. Ant. = anterior, Post. = posterior. (Modified and reprinted from Dodds et al. [5].)
C Fig. 4.-Schematic
cross
sections
of upper abdomen
of embryo
and
fetus. A, 5-week embryo. Stomach is supported by a dorsal mesentery (dorsal mesogastrium) and ventral mesentery (ventral mesogastrium). Spleen develops within dorsal mesogastrium while liver develops within ventral mesogastrium. B, 8-week embryo. As liver enlarges and swings to right, spleen and stomach swing leftward to form lesser peritoneal sac. Liver divides ventral
mesogastrium
into falciform
divides
mesogastrium into gastrosplenic (4), part of which will become
dorsal
mesogastrium
(1) and gastrohepatic
(2) ligaments.
Spleen
ligament (3) part of dorsal splenorenal ligament. This
ligament normally lies against and fuses with posterior peritoneum to form short splenorenal ligament. Failure of this fusion leads to a long splenic mesentery and a wandering spleen. C, Mature fetus. Almost all of posterior part of dorsal mesogastrium has fused with posterior peritoneum to leave a short splenorenal ligament (4). Gastrosplenic ligament, spleen, and splenorenal ligament form lateral margin of lesser peritoneal sac. L = liver, Sp = spleen, S = stomach, K = kidney, I = falciform ligament, 2 = gastrohepatic ligament, 3 = gastrosplenic ligament, 4 = splenorenal ligament. (Modified and reprinted from Dodds et al. [3].)
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808
DODDS
ET AL.
AJR:155,
October
1990
Fig. 7.-Disease invading spleen via splenorenal ligament on contrast-enhanced CT scans. Commonly, pancreas passes through splenorenal ligament to abut against hilum of spleen. Consequently, disease processes of pancreatic tail have access to a direct pathway to spleen. A, Pseudocyst (arrow) originating from pancreatic tail has extended into lower margin of splenic hilum. B, Carcinoma originating from tail of pancreas has invaded hilar area of spleen (arrows). Metastatic areas of low attenuation are seen in liver.
A
Fig. 8.-Example of splenic clefts on contrastenhanced abdominal CT scan. Two congenital clefts (arrows) are seen.
of the spleen medial part bus splenic
(Fig.
of the artery
8), whereas spleen and may (Fig. 9). Some
B
Fig. 9.-Example of splenic lobulation on a celiac arteriogram. A, Arterial phase. Accessory segmental artery (arrow) supplies upper medial margin of spleen. B, Capillary phase. Spleen exhibits a large lobulation (arrow) at its mediosuperior border.
lobulations occur along the be supplied by an anomalobulations cause a worn-
some extrinsic gastric impression. One or more accessory spleens, on splenculi, are present in about 1 0% of the population. Accessory spleens are most often located in the vicinity of the splenic hilum (Fig. 10), along the course of the splenic vessels, or within the gastrosplenic ligament or omentum, but they may occur anywhere in the abdomen. Accessory spleens may be single or multiple, but there are seldom more than six (Fig. 1 1). Characteristically, they are smooth with a round or oval shape and are about 1 .0-1 .5 cm in diameter. Because accessory spleens frequently overlap the pancreas and show a homogeneous stain on arteniography, they must be distinguished from an isletcell pancreatic tumor on angiography. On CT, their characteristic appearance and location within the embryologic dorsal mesenteny of the stomach and pancreas (Fig. 6) generally distinguish them from enlarged lymph nodes. Occasionally, an accessory spleen may be embedded along the greater curvature of the stomach to form an intramural mass. When
a splenectomy spleens should the
main
spleen
is done for a blood dyscrasia, all accessory be removed because they may enlarge once is removed.
Definitive
identification
of
an
accessory spleen is accomplished by a liver-spleen scan with technetium sulfur colloid, which labels splenic reticuloendothelial cells as well as those in the liver. Oblique views may be required. In some individuals, the dorsal part of the gastric mesentery (Fig. 4B) may not fuse with the dorsal peritoneum and thereby persist as a long mesentery. This anomaly results in a “wandening spleen,” which is highly mobile and may rotate to the center of the abdomen (Fig. 1 2). Frequently, the tail of the pancreas lies within the long splenic mesentery because of the proximity of the dorsal mesentery of the pancreas to the dorsal mesentery of the spleen during the first trimester of gestation (Fig. 6). A wandering spleen is often discovered as an asymptomatic mass in the anterior abdomen. Diagnostic evaluation by sonography, CT, or hepatic radionuclide scanning discloses that a normal spleen is not present in its typical location. Other confirmatory evidence of the diagnosis is that the splenic vessels pass to the ectopic mass. In some in-
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AJR:155,
October
SPLENIC
1990
Fig. 10.-Accessory
spleen
on slightly
oblique
Fig. 1 1.-Accessory
ANOMALIES
spleens
809
on contrast-enhanced
abdominal
CT scans.
A, Solitary accessory spleen (arrow) is located lateral to kidney and caudad to main spleen (not shown). Accessory spleen, a smooth 1.5-cm mass, had same attenuation as main spleen. Accessory
coronal view obtained by placing transducer head between ninth and tenth ribs in mid axillary line. Spleen acts as sonographic window. Splenic vein (curved arrow) is seen entering hilum of spleen. A sharply defined 2- by 3-cm mass (straight arrows) shows same echogenic characteristics as spleen, and is identified adjacent to inferior margin of splenic hilum. This mass, judged to bo an accessory spleen, was confirmed on abdominal CT.
spleen is located within original dorsal mesentery to stomach or duodenum. B, Multiple accessory spleens. On this CT image, three accessory spleens (arrow) of gastrorenal ligament. Three additional accessory spleens main spleen was absent. This patient did not have congenital
were present at more heart disease.
are seen in fat caudal
levels.
A
4 Fig. 12.-Ectopic
wandering
scintigram obtained soft midline mass
spleen on hepatic
Fig. 13.-Torsion and ischemic infarction of a wandering spleen. A, Contrast-enhanced CT scan bolow level of liver. Unenhanced mass (arrows), representing infarcted wandering spleen, is seen on left side of abdomen. B, Hepatic scintigram. Anterior view shows normal-appearing liver in upper abdomen, whereas
to evaluate asymptomatic, in middle abdomen that was
discovered on a routine physical examination. Anterior view shows normal-appearing liver in upper abdomen. Ventral wandering spleen (arrow) is seen in midline, just caudad to liver. A normal spleen
is not seen
stances, mesentery.
mia,
in left upper
a wandering Such
and the acute
CT, the ischemic
quadrant.
spleen
torsion
onset
spleen
spleen is not imaged.
undergoes
causes
vascular
of abdominal
does
a volvulus pain.
not enhance
injection (Fig. 1 3A). Also, a normal spleen, ischemic spleen, does not show radioactive isotope scan (Fig. 1 3B). Several congenital cardiosplenic syndromes consist
of complex
cardiac
malformations,
on its long
compromise,
ische-
On abdominal
after contrast as well uptake
as the on an
may occur
splenic
that
anomalies,
and intermediate situs. The asplenia type, predominant in females, has bilateral right-sided features of a horizontal midline liver, Howell-Jolly bodies in the peripheral blood resuIting from asplenia, and bilateral right lung morphology. The
polysplenic bilateral bladder
type, (Fig. 14), which occurs
be associated tract.
mainly in males, has
left-sided features consisting of absence and bilateral left lung morphology. Both The
with situs
asplenic
type
ambiguous is associated
of a galltypes may
of the gastrointestinal with
cyanotic
heart
DODDS
810
ET AL.
AJR:155, October 1990
Fig. 14.-Polysplenic cardiosplenic syndrome in child with complex congenital cardiac anomalies and polysplenism. A, Parasagittal sonogram through left kidney. Two round, 5- to 6-cm masses (asterisks) representing multiple spleens are seen Immediately
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ventralto
kidney. A third spleen was identified just
cephalad, but a normal-sized spleen was absent. B, Liver-spleen scintigram. Liver appears normal. Three spleens (asterisks) are seen in left upper abdomen.
Fig. 15.-Spleen (asterisk) located in eventration of left hemidiaphragm is seen on abdominal CT scan obtained to exclude malignancy in 20year-old patient. Diaphragmatic eventration was judged to bo congenital.
Fig. 16.-Anomalous bohind 15
location
of spleen (arrow)
left kidney.
16
disease and a poor prognosis. The spleen or spleens be sought mainly in the upper quadrant ipsilateral stomach because the spleen develops in the dorsal
should to the gastric
A relatively
mesentery.
Another
congenital
splenogonadal
syndrome,
anomaly wherein
involving
the
spleen
an association
is the
exists
be-
splenic and gonadal tissue [6]. In the first trimester of pregnancy, the developing anlage of the spleen and left gonadal anlage lie in close apposition (Fig. 4) when partial fusion occurs between the dorsal mesogastrium and left posterior penitoneum. At about 9 weeks of gestation, the left gonadal anlage begins to migrate toward the pelvis. A discontinuous type of splenogonadal anomaly occurs when some splenic tissue migrates with gonadal tissue. In this case, a normal single spleen is present in the left upper abdomen. In the continuous type of splenogonadal anomaly, a cord of splenic or fibrous tissue connects a normally located spleen with the testes, epididymis, ovary, or mesovarium. In males, left-sided cryptorchidism is present. Existence of the splenogonadal syndrome is generally documented as an unsuspected finding in individuals undergoing surgery for other tween
reasons,
identified on sonography in utero or diagnosed Children or young adults may exhibit congenital eventration (Fig. 15) or herniation.
such as a splenectomy
or oophorectomy.
Congenital herniation of the left hemidiaphragm may involve the spleen as well as the intestine. Such hemiations may be
posterior
common
location
congenital
of the spleen
16). This circumstance
anomaly behind
may occur
is a pronounced
the
when
in the neonate. diaphragmatic
left kidney
(Fig.
a deep penitoneal
lateral recess persists that is filled by the spleen or intestine [5]. Importantly, this anatomic anomaly must be considered when doing a percutaneous puncture for placement of a nephrostomy tube in the left kidney.
REFERENCES 1 . Goss CM, ed. Anatomy Febiger,
of the human
body,
28th ed. Philadelphia:
2. Moore KL, ed. The developing human: clinically oriented ed. Philadelphia: Saunders, 1977 3. Dodds WJ, Foley WD, Lawson TL, Stewart ET, Taylor imaging
Lea &
1966
of the lesser
peritoneal
sac. AJR
embryology,
2nd
A. Anatomy
and
1985;144:567-575
4. Netter FH. Upperdigestivetract. In: OppenheimerE, ed. TheCiba collection of medical illustrations, vol 3. Digestive system, part 1 . New York: Ciba, 1962 5. Dodds WJ, Darweesh RMA, Lawson TL, et al. The retropentoneal spaces revisited. AJR 1986;147: 1155-1161 6. Sty JR, Conway JJ. The spleen: development and functional evaluation. Semin NucI Med 1985;15:276-298
