Gastrointest Radiol 2, 4 1 - 4 7 (1977)
Gastrointestinal
Radiology
i~ by Springer-Verlag 1977
Congenital Positional Anomalies of the Colon:
Radiographic Diagnosis and Clinical Implications
I. Abnormalities of Rotation
Emil J. Balthazar
Department of Radiology, New York Medical College, New York, New York, USA
Abstract. Positional anomalies of the colon may be cussed in the radiographic literature [l 3]; (2) posi-
explained by an arrest in the normal development tional abnormalities related to an embryologic aberra-
process of the distal midgut. Aberrations involving tion and fully explained by the development process.
the incipient stages of rotation lead to severe malposi- The latter group can be further divided and discussed
tions, while those involving the latter stages to milder as (a) malpositions related mainly to the process of
forms. The normal embryology of the distal (post- intestinal rotation and (b) positional anomalies re-
arterial) segment, as well as forms of complete and lated only to the process of intestinal fixation.
partial nonrotations, are discussed and illustrated. A The purpose of this report is to present a compre-
survey of 39 consecutive cases of rotational abnorma- hensive review of the radiographic appearance, diag-
lities of the midgut with special emphasis on the con- nosis, and clinical implications of congenital malposi-
figuration of the colon is presented. There is a high tions of the colon as observed in the adult population.
incidence of associated failure of fixation resulting Although most of these abnormalities have no imme-
in mobile colons that can be demonstrated ra- diate clinical significance it is nevertheless important
diographically. In addition, the great majority of colo- to recognize them promptly. Understanding the
nic malrotations demonstrate rotational abnorma- mechanism of the normal embryologic development
lities involving the proximal intestinal tract. Their of the colon is crucial in identifying such abnorma-
clinical implication is related to the presence of other lities. Their correct recognition avoids confusing ra-
incidental congenital anomalies or to complications diographic interpretations and embarrassing diagnos-
derived from faulty mesenteric fixations such as peri- tic errors. It allerts the radiologist and the clinician
toneal bands, adhesions, kinking, or intestinal vol- to the possibility of associated congenital anomalies
vulus. in the upper gastrointestinal tract and other organs.
Finally, it may provide a basis for the explanation
Key words: Colon - Malrotation -- Congenital
of ill-defined, long-standing, and intermittent abdom-
anomalies.
inal complaints produced by complications sometimes
associated with such abnormalities.
Positional anomalies of the colon are common find-
ings encountered during routine barium enema exami- Embryologic Background
nations. One can divide such abnormalities into two
large groups: (1) acquired positional abnormalities In the first weeks of embryologic development, the gastrointestinal
related to organomegaly or to intra-abdominal soft tract is represented by a straight tubular structure [4]. Its rapid
tissue masses compressing and displacing the colon. growth leads to the development of a curvature in the middle
The characteristic radiographic findings of such ac- one-third with the apex at the level of the insertion of the vitelline
duct (yolk stalk). Exiting from the posteriorly situated abdominal
quired anomalies as well as an analysis of the normal aorta, the superior mesenteric artery (SMA) enters the center of
anatomic relationships of the colon have been dis- the bulge travelling within the leaves of the primitive dorsal mesen-
tery; its distribution defines the length of the midgut from the
Ad~h'ess reprint requests to : E.J. Balthazar, M.D., Associate Profes- middle third of the descending d u o d e n u m to the distal transverse
sor, Department of Radiology, New York Medical College, 5th colon. The intestinal tract distal to the splenic flexure is defined
Avenue and 106th Street, New York, NY 10029, USA as the hindgut while the proximal intestinal segment is the foregut,
42 E.J. Balthazar: Congenital Positional Anomalies of the Colon. I
Table 1. Position of the colon in 39 cases of malrotation of the A
midgut in adults
Type of abnormality Cases
J
/
Normal rotation, colon normal position 15
Nonrotation, colon m left side of abdomen 14
Partial rotation, colon overlapping spine 9
Nonrotation common mesentery, midline colon 1
\
The normal and abnormal development of the midgut, and particu-
larly of its segment distal and inferior to the axis of SMA (the
post-arterial segment), is the subject of this presentation.
In the fourth week of gestation (5 mm embryo), the midgut
is located within the peritoneal cavity. Its rapid development leads ,/
to its migration into the umbilical cord at the beginning of the /
fifth week of gestation. The herniation of the midgut into the
/
umbilical cord, its rotation around the axis of the SMA and its
return to the abdominal cavity were described at the end of the
19th century [5]. In 1923, Dott arbitrarily divided the development
process into three separate stages of evolution and offered a classifi-
cation of congenital malpositions based upon these stages [6]. It
has been assumed that the midgut rotates as a unit and that in
cases of failure of rotation, the return of the intestine to the peri-
toneal cavity will result in a characteristic and monotonous pre-
sentation: small bowel located on the right, and the colon on
the left side of the abdomen.
Other investigators however, after examining human embryos
during the first 12 weeks of gestation, recognized the existence
of a number of intermediate stages of development involving suc- C
cessively the proximal (we-arterial) and the distal (post-arterial)
segment [7]. These transitional stages of evolution relate to the
process of rotation as well as to the return of the midgut to the
abdomen.
Snyder and Chaffin [8] pointed out that the rotation of the
J
midgut follows the initial movement of two leading loops of bowel:
the duodenojejunal loop in the proximal (pre-arterial) segment and
the cecocolic loop in the distal (post-arterial) segment. The inter-
mediate stages of development of the distal (post-arterial) segment
are as follows.
Before the rotation starts at the fourth week of gestation (5 mm
embryo), the cecocolic loop is located beneath the SMA. Beginning
with the fifth week of gestation (10 mm embryo), it moves to
the left of the SMA, accomplishing a 90 ~ rotation. During the
10th week of gestational development (40 mm embryo), the ceco-
colic loop drops back into the abdominal cavity and is stiU situated
to the left of the SMA in the upper abdomen. At this time the
D
rotation of the proximal (pre-arterial) segment and its return to
the abdomen is already accomplished. In the abdomen, the ceco-
colic loop gradually moves over the SMA in a superior and anterior
direction fulfilling a 180 ~ rotation. The process of rotation proceeds
by a continuous movement to the right of the SMA towards the
right upper quadrant, shortly after the 10th week of gestation,
completing a total 270 ~ counterclockwise rotation. After the
process of rotation is completed (about the 12th week), the growth
of the colon forces the descent of the cecum fi'om the right upper /
quadrant into the right lilac fossa, where it reaches its final location
by the fifth month of gestation [5]. The adult configuration of
the colon is achieved with the fixation of the colonic mesentery Fig. 1. The most c o m m o n configurations of the colon in cases
to the posterior abdominal wall. of complete or partial nonrotations of the distal midgut
