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*‘IAY, 1971
- I”roni the I)epartnient of Radiology, Indiana University Medical Center, Indianapolis, Indiana.
ANOMALIES OF THE ANTERIOR ABDOMINAL WALL:
CLASSIFICATION AND ROENTGENOLOGY*
By EDMUND A. F’RANKEN, JR., M.D.
INDIANAPOLIS, INDIANA
N UMEROUS articles concerning urn-
bilical anomalies and related malfor-
mations of the abdominal wall have been
published since the treatise of Cullen in
I 9 I 6,’ but relatively few publications9” con cern i ng tile perti nen t roen tgenology
have appeared. In recent years a better tin-
derstanding of the embryologic develop-
ment of the abdominal wall has defined the relationship of the various defects to one another.
The purpose of this paper is to correlate
the embryology, pathologic anatomy, and
applied roentgenology of the various ab-
dominal wall anomalies encountered in
clinical practice.
EM BRYO LOGY The primitive embryo is disk shaped,
with a dorsal ectoderm (continuous with
the amnion), ventral endoderm (continuous with the yolk sac), and intervening meso-
derm.6 With further growth the mesoderm
separates to form the extra-embryonic coe- lom (Fig. izl). This cavity soon extends in-
to the germinal disk, so that the ectoderm
and endoderm witil their associated por-
tions of mesoderm are separated by the
i ntra-embrvoni c coelom. The layer of meso-
derm associated with tile ecto(lerm is
termed somatopleure; tilat with the endo-
derm, splanchnopleure.
Closure of the embryo body is accom-
plished by ventral folding of the lateral
aspects of the embryo. Four folds can be distinguished: cephalic, caudal, and each lateral. The apex of the folds is the future umbilicus, and with their fusion the em-
brvo body is closed except for attachments
through the umbilicus (body stalk) (Fig. I, B and C). Failure of formation of any of the folds results in the malformation of
celosomia, i.e., hernia of the anterior ab-
dominal wall.
An upper celosomia occurs with failure of
formation of the cephalic fold. This con-
dition results in omphalocele and defects of the anterior chest wall and diaphragm with
ectopia cordis, as these structures arise
from the cephalic somatopleure. The ceph-
alic splanchnopleure, from which the
heart and great vessels develop, is present,
but accompanying car(liovascular malfor-
mations are common.
Middle celosomia occurs with failure of
descent of the lateral folds, and the um-
bilicus remains wide and patent. This is the
anomaly described as omphalocele.
With failure of formation of the caudal
fold, a complex malformation known clin- ically as extrophy of the cloaca is seen. This
consists of omphalocele, hindgut agenesis,
and extrophv of tile bladder with fistula of
intestine to the extrophied bladder.
An anomaly which must be distinguished
from omphalocele is that of gastroschisis.
In this condition the somatopleure of the lateral fold adjacent to the umbilicus fails
to differentiate. Secondary resorption of the
overlying ectoderm results in a perium- bilical defect through which bowel her-
niates. In contrast to omphalocele, no
amniotic sac covers the herniated bowel. Anomalies produced in later embryonic
life include persistence of the vitelline duct
connecting bowel lumen with the yolk sac
(omphalomesenteric duct), and patent ura-
chus (persistent allantoic canal between bladder and umbilicus). Classification of the various congenital
abnormalities of the umbilical region based
on the above embr\’ologic data is as fol-
lows:
I. Somatic Anomalies
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AMNION ECTODERM MESODERM
COELOM
Voi. 112, No. I !\nonialies of Anterior Abdominal \Vall 59
ENDODERM
YOLK SAC
FUTURE UMBILICUS
FIG. i. (A) Diagrammatic cross section of the disk shaped embryo. The ectoderm is continuous with the
amnion, the endoderm with the yolk sac. The intra-embryonic coelom divides the mesoderm into the somatopleure (adjacent to ectoderm) and splanchnopleure (adjacent to endoderm). (B) Ventral view of
the embryo during closure of the body wall (after 1)uhamel). Four folds are seen: cephalic, caudal, and
each lateral. These folds join at the future umbilical ring to produce the body stalk. (C) Cross section at
the level of the umbilicus after ventral closure of the abdominal wail. The folds fuse at the umbilicus (body
stalk). The ectoderm and somatopleure comprise the chest and abdominal walls and are separated from the endoderm and spianchnopleure by the coelomic cavity. The lumen of the future bowel communicates with the yolk sac through the body stalk by the vitelline duct.
A. Cephalic celosomia-midline oie- fect of abdominal and chest wall,
with deficient pericardium and
(liaphragm. B. Lateral wall celosom i a-om pha_ locele. C. Caudal celosom ia-extrophy of
cloaca.
D. Lack of differentiation of lateral
fold mesenchyme-gastroschisis.
II. Umbilical Anomalies A. Alimen tarv-complete or partial
Persistence of omphalomesen teric
(ltlCt. B. Urachal-complete or partial per-
sistence of urachus.
DISCUSSION CEPHALIC FOLD DEFECTS A specific constellation of defects is seen
ill these patients.3 Because of failure of
medial migration of the sternum, there is
an anterior defect in the chest wall, with a
wide cleft in the lower sternum, and the
heart is not covered by the rib cage. Dex-
troposition of the heart is invariably pres-
ent, but true ectopia cordis does not occur
in that the heart remains in the thorax. The
clinical appea ra lice of ectopi a cord is restil ts
from lack of covering of tile heart liv ru)
cage and epugastrium. An anterior midline
diaphragmatic (lefect occurs, with absence
of pericardium in the same region. There is
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FIG. 3. (A and B) Newborn with omphaloceie. The KUB (kidney, ureter, bladder) and lateral abdomen
studies demonstrate the large soft tissue mass of the omphalocele. The umbilical cord inserts on tile in- ferior aspect of the sac. The soft tissue mass within the sac is herniated liver.
VOL. 112, No. Anomalies of Anterior Abdominal Wall 61
be seen in the lateral projection. The main portion of the omphalocele is located in tile epigastnuum. If malrotation with intestinal
obstruction is present, the gas pattern
should reflect this.
Treatment of this syndrome consists of
omphalocele closure, repair of the (ha-
phragma tic defect, an(l appropriate surgery
for the heart disease present. The reader is referred to the excellent summary of Can- trell and associates3 for details of surgical correction.
OMPHALOCELE In this condition the abdominal wall de- fect is at the umbilicus. The size of the de- fect and its contents are variable. The pro- lapsed abdominal viscera are covered by a translucent membrane of amnion-peni-
toneum,7 and the umbilical cord is inserted
into the sac. The amount of viscera within the sac is proportional to the size of the sac and not to the size of the abdominal wall
defect. A small omphalocele may have a
single ioop of small bowel or a Meckel’s
diverticulum within it, while the larger sacs
may contain most of the abdominal portion of the gastrointestinal tract. A portion of the liver is found in 30-50 per cent of larger
sacs.7 This is continuous with the main por-
tion of liver in the penitoneal cavity. Less
frequently other abdominal viscera includ-
ing pancreas, spleen, and genital organs
are found in large omphaloceles.
Attachment of the intestinal mesenterv is abnormal in most cases of omphalocele, the base of the mesentery being fixed only by the superior mesentenic arter\’. This pre- disposes to midgut volvulus, and the duo-
denal bands accompanying malrotation are
frequent. Additional anomalies are present in 40- 8o per cent of omphalocele patients.7 Con- genital defects of the gastrointestinal tract
are most common, and include atresia or
stenosis of portions of the intestine an(l Meckel’s duverticulum.8 Cardiovascular and genitouninarv anomalies are also fre-
quent.
The role of radiology in the case of om-
phaloceles is principally related to detec-
tion of associated conditions. Preoperative
roentgenograms (Fig. 3, 4 and B) are not generally necessary, although they help de-
termine the presence of malrotation and
partial duodenal obstruction (Fig. 4, 4 and B). In the evaluation of postoperative
roentgenograms, one should recall the fre-
quent presence of duodenal bands asso-
ciated with malrotation, and the possu-
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)
(c2 Edmund A. Franken, Jr. Msv, 1971
11G. 4. Omphalocele with associated nialrotation. (A) Preoperative KUB study on this infant shows some
distention of the stomach and proximal duodenum, with minimal gas distally. Obstructing duodenal bands were lysed at surgery. (B) Barium meal examination on a Iostoperative omphalocele patient. The study
exhibits an abnormal duodenal loop indicative of malrotation. No ligament of Treitz is apparent, and the
proximal jejununl is on tile right. The dilatation of the small bowel loops is secondary to obstructive ad-
hesive bands in the distal small bowel.
bilutv of midgut volvulus. Liver wilich has
been partially included in an ompilalocele
may ilave an unusual shape when retu rued to
the abdominal cavity and thereby sim-
ulate a mass lesion (Fig. , zi-D).
The surgical treatment of omphalocele is
dependent upon tile size of tile sac.’ If liver
IS in the omphalocele, primary repair is
usually not feasible, and a 2 stage procedure
becomes necessary. Tile (letailS of surgery
are well (lescrube(i elsewhere.’’
EX1ROI’HV OF ‘IH E CI.0.\C.t
According to Duhamel,6 this term is
embryologically incorrect, in that the mal-
formation results from failure of develop-
ment of both somatic and splanchnic por-
tions of tile caudal fold. However, clinical
usage has assugne(l the term to this anom-
al\’. The anatom\’ of extrophy of the
cloaca is illustrated in Figure 6, 4 and B.
An omphalocele is present. An extrophied
bladder is inferior to the omphalocele. The
bladder mucosa is split in tile midline by a
gastrointestinal stoma through which bowel
prolapses. This is terminal ileum. The ureteral orifices are on both sides of the
prolapsed bowel. Inferior to tile ileal stoma
is another gastrointestinal opening. This
is the cutaneous presentation of the colon.
Tile length of tile colon is variable, and it
ends blindly, with high level imperforate
anus always present. ‘The gastrointestinal
anomaly has been somewhat variable in
patients seen at this institution, ranging
from total colon aplasia to a long segment of colon interposed between the ileum and
cutaneous tistula. The genital structures (in
either sex) are bifid, and an associated
rnyelomeningocele is common.
Because of tile complexity of tile above
syndrome, roentgenologic investigation
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64 Edmund A. Franken, Jr. Msv,^ i 7i
I
UMBILICAL CORD
PROLAPSED TERMINAL ILEUM
EXTROPHIED BLADDER
-URETER
STOMA OF COLON
BLIND COLON’
lic. 6. 1’xtrophy of the cloaca (after Swan and Christensen’4). (4) 1)iagrani of clinical appearance of ab-
dominal wall. The most cephahic structt re is an o nphalocele. Immediately c:tudal to this, an extrophied
bladder presents. The bladder mucosa is split in the midline by the stoma of the terminal ileum; charac-
teristically there is prolapse of bowel through this opening. Inferior to the terminal ileum is the cutaneous
presentation of a blind colon. (B) Diagrammatic cross section of the lower abdomen further delineates the nature of extrophy of the cloaca. The structures presenting in tile midline are, from superior to inferior, omphalocele, terminal ileum, and colon.
I’ic. 7. Extnophv of tile cloaca. (4) Roentgenogram of the pelvis at year of age. There is failure of midline
fusion of the pubic nami identical with the deformity noted in extrophv of the bladder. There are also Segmentation anomalies of the sacrum, and neural arch defects secondary to a small sacral meningocele.
(B) Lateral roentgenogranl (of another patient) shows herniated bowel loops extending anterior to the
pelvis through the lower abdominal defect.
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VOL. 112, No. Anomalies of Anterior Abdominal Wall 6
Gastrointestinal examination wi dl bar- ium is utilized to study the stomach and small bowel. The presence of malrotation is documented and the approximate length of small bowel can be determined. A search for localized stenosis or duplications is per- formed, as these defects have been reported to occur in this condition. The exact fistula from which the small bowel exits on the abdominal wall is also determined (Fig. 94). Ifan inferior stoma is present, this repre- sents the external presentation of the blind- ending colon. Contrast medium study through this opening determines the length and character of the colon remnant (Fig. 9, B and C). Absorbable contrast agents should be used in this examination since the colon ends blindly. This information is necessary to the surgeon, for if sufficient colon is available, repair should include anastomosis of small bowel to colon fol- lowed by colostomy. Surgical repair of extrophy of the cloaca is difficult and not usually productive, but isolated survivors have been reported.’3” A variety of procedures have been per- formed. The best results occur when the colon segment can be utilized as part of the gastrointestinal tract, thereby increasing the absorptive area. Both sexes have been reported with extrophy of the cloaca. Cytologic methods and/or surgical exploration may be neces- sary to determine genotypic sex. In view of the extensive external genital defects, the appropriate sex of rearing is probably fe- male. GASTROSCHISIS Gastroschisis differs from omphalocele in that it represents a complete defect in the abdominal wall adjacent to but not involv- ing the umbilicus.’0 It is clinically differ- entiated by the presence of normal attach- ment of the umbilical cord and lack of a covering amnionic sac. Because the pro- lapsed viscera are uncovered by a protective sac, exposure to the amnionic fluid may produce considerable reaction of the serosa
FIG. 8. Extrophv of the cloaca. A retrograde pyelo- gram demonstrates the laterally placed ureteral orifices. There is a pelvic kidney on the left.
of the bowel. Tile amount of serosal reac- tion, or peal, is apparently related to time of exposure of bowel to the amnionic fluid,
and perinatal and antenatal eviscerations
are described. The small and large bowel
are usually the eviscerated organs, but
other intra-abdominal organs may par-
ticipa te.
A matter of importance in gastroschisis is
the lack of significant associated anomalies
other than bowel malrotation. Moore’#{176}re- ports that only 3 of 31 cases had serious
associated defects, all these being atresia
of the small intestine. The roentgenologic importance of gas- troschisis is not great. Preoperative roent- genograms indicate the lack of a covering sac, with outlining of exterior herniated bowel by air (Fig. io). Intestinal obstruc- tion secondary to small bowel atresia should be roentgenologically detectable. The need of roentgenologic search for additional anomalies is not as great in gastroschisis as in omphalocele. Moore has summarized the surgery of gastroschisis’#{176}: a modification of the usual
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\oi.. 112, No. I Anomalies^ of^ Anterior^ Abdominal^ \Vall^67
Fic. 10. Gastroschisis. Preoperative KUB roent- genogritnl. 1 hlere is contrast material in the urinary bladder. 1’he prolapsed bowel loops are visible and surrounded by air on their external surfaces, in-
dicating loss of a covering sac. A ruptured omphai-
oceie could present an identical picture on the roen tgenogram.
associate(l with this condition. In omphalo_
cele, roentgenologic search for additional congenital anomalies, particularly of the
gastrointestinal tract, is important. Ex-
trophy of the cloaca, or cau(Ial fold defect, demands a thorough study of the intestine
for potential surgical correction. IlliS in-
cludes determination of the length and
character of the blind colon remnant, if this
is present. Gastroschisis is (hstinguished
from omphalocele principally by the physi- cal examination, and the incidence of ad-
ditional serious anomalies in this con(lition
is low.
I)epartment of Radiology
Indiana University Medical Center 1100 West Michigan Street
Indianapolis, Indiana 46202
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This article has been cited by:
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