DOI:10.2214/AJR.06.0898
AJR 2007; 189:52-55
© American Roentgen Ray Society
Diagnosis of Transmesocolic Internal Hernia as a Complication of Retrocolic Gastric Bypass: CT Imaging Criteria
Suraj A. Reddy1,
Caroline Yang1,
Leslie A. McGinnis1,
Richard E. Seggerman1,
Ernesto Garza2 and
Kenneth L. Ford, III1
1 Department of Radiology, Baylor University Medical Center, 3500 Gaston Ave.,
Dallas, TX 75231.
2 Department of Surgery, Baylor University Medical Center, Dallas, TX.
Received July 10, 2006;
accepted after revision October 11, 2006.
Address correspondence to S. A. Reddy
(surajreddy02{at}yahoo.com).
Abstract
OBJECTIVE. The purpose of this study was to define the CT findings
of surgically proven transmesocolic internal hernia after laparoscopic gastric
bypass.
CONCLUSION. Use of four CT signs should give radiologists a high
degree of accuracy and confidence in recognizing internal hernia in patients
who have undergone gastric bypass surgery.
Keywords: abdominal imaging • CT • emergency radiology • gastrointestinal radiology • small bowel
Introduction
Morbid obesity has become a nation-wide health problem, the prevalence
increasing each year. Gastric bypass is the fastest growing surgical procedure
in the United States, and bariatric operations have become an increasingly
common method of weight loss, weight maintenance, and reduction of chronic
health problems associated with obesity
[1–3].
The various forms of laparoscopic bariatric surgery include antecolic and
retrocolic Roux-en-Y bypass and vertical gastric banding. Each procedure
carries unique benefits and complications.
The purpose of this study was to describe the CT findings of transmesocolic
internal hernia developing after laparoscopic Roux-en-Y gastric bypass. The
complications of retrocolic Roux-en-Y gastric bypass include anastomotic leak,
anastomotic stricture, bleeding, bowel obstruction, and internal hernia
[1]. The most frequent
complication at our institution is internal hernia, which can cause severe
morbidity and mortality if not recognized early. Rapid weight loss and dynamic
restructuring of the abdominal contents after bypass can lead to loosening of
the Roux-en-Y limb that has been fixed to the transverse mesocolon. Multiple
loops of small bowel and the distal anastomosis can then herniate through and
above the level of the transverse mesocolic defect
[1]
(Fig. 1). The hernia can cause
intermittent obstruction, volvulus, and ischemia of the Rouxen-Y limb
[3,
4]. Effective use of CT for
early detection of this complication can markedly reduce the risk of further
complications [3,
4].
Materials and Methods
Review of the weight loss surgery program database at our institution
yielded approximately 1,000 patients who underwent retrocolic laparoscopic
Roux-en-Y gastric bypass surgery over a 12-month period. Analysis of the data
showed 49 of these patients subsequently underwent laparoscopic surgical
repair of transmesocolic internal hernia. Review of these patients' medical
and radiologic records to find patients who had undergone abdominopelvic CT in
preparation for the hernia operation yielded 27 such patients. Twenty-five of
these patients were women, and two were men. The average age was 36 years. The
93% preponderance of women in this sample approximated the proportion of women
undergoing gastric bypass at our institution.
The 27 patients felt vague intermittent abdominal pain an average of 7.7
months (range, 1–18 months) after the gastric bypass surgical procedure.
Helical CT of the abdomen and pelvis was performed to evaluate the source of
abdominal pain. The CT scans were acquired with a slice thickness of 5 mm
after administration of approximately 8 ounces (237 mL) of water-soluble oral
meglumine diatrizoate (Gastrografin, Bristol-Myers Squibb) and 100 mL of
low-osmolar nonionic IV iohexol 350 (Omnipaque, Nycomed). The patients were
usually given 5–6 ounces (148–177 mL) of the contrast agent to
drink at their own pace and then were asked to drink the last 2–3 ounces
(59–89 mL) immediately before imaging to improve distention and
visualization of the gastric pouch.
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Fig. 3A —37-year-old woman after gastric bypass. Axial CT images 10 mm
apart show multiple redundant loops of small bowel (solid arrow)
adjacent to pouch (dashed arrow, A) in left upper
quadrant.
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Fig. 3B —37-year-old woman after gastric bypass. Axial CT images 10 mm
apart show multiple redundant loops of small bowel (solid arrow)
adjacent to pouch (dashed arrow, A) in left upper
quadrant.
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Fig. 6 —38-year-old woman after gastric bypass. Axial CT image shows
distal jejunojejunostomy anastomosis (solid arrow) at level of
tightly clustered vessels (dashed arrow) indicating mesocolic defect
and suture lines from proximal gastrojejunostomy. Findings are consistent with
high position of anastomosis.
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Imaging reports were analyzed to determine the percentage of CT scans on
which transmesocolic internal hernia was prospectively identified. Other
diagnoses included small-bowel obstruction and no findings of an acute process
in the abdomen. In a second group of five patients with symptoms similar to
those of the study group, the preoperative CT diagnosis of internal hernia
proved false; no evidence of internal hernia was found at surgery.
All patients underwent surgery within the first 24 hours after CT because
of high clinical suspicion of internal hernia or because of persistent
symptoms. To assist in accurate future diagnosis, the CT scans of these
patients were retrospectively reviewed for identifiable similarities to and
differences from surgically proven cases of the presence and absence of
internal hernia.
Each case was retrospectively reviewed by two radiologists experienced in
abdominal imaging. In retrospective analysis, four signs were repeatedly
visualized in most of the surgically proven cases. A fifth sign seen in
approximately one half of patients in both groups helped to identify the
location of the mesocolic defect for further assessment of the presence of
internal hernia.
Results
Two experienced abdominal radiologists identified several recurring signs
on abdominopelvic CT scans of the 27 patients with surgically proven internal
hernia. In all 27 patients, the reviewers found multiple loops of small bowel
cephalic to the transverse mesocolic defect. A single Roux limb normally would
be seen exiting the gastric pouch and taking an inferior course through the
mesocolic defect to reach the jejunojejunostomy
(Fig. 2). In the patients with
internal hernia, the reviewers found multiple loops of bowel cephalic to the
transverse mesocolon between the stomach and spleen in the left upper quadrant
(Figs. 3A,
3B, and
4).
The second CT sign, identified in 26 (96%) of the 27 patients, was a high
position of the distal jejunal anastomosis. The distal anastomosis normally
would be located midlevel in the abdomen at approximately the midlevel of the
left kidney (Fig. 5). The
distal anastomosis never should be seen at or above the level of the defect or
the proximal anastomosis (Figs.
6 and
7). The third CT sign, seen in
all 27 patients, was an ascending course of tightly clustered blood vessels in
the small-bowel mesentery. Because multiple loops of small bowel had herniated
through the mesocolic defect, the vascular supply to these loops was
visualized traversing the defect as a tightly clustered group of vessels
ascending to the left upper quadrant (Figs.
6 and
8). Normally this finding would
not be seen because the single efferent limb would have only two vessels
coursing to it. The fourth CT sign, identified in 13 (48%) of the patients,
was dilatation (diameter > 3 cm) of the efferent jejunal limb. The patients
with this sign had more severe symptoms than the other patients. In some
cases, the internal hernia caused obstruction of the Roux limb, which became
dilated and fluid filled (Figs.
9 and
10).
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Fig. 10 —27-year-old woman after gastric bypass. Axial CT image shows
dilated efferent jejunal limbs (solid arrow) and pinching of jejunal
efferent limb (dashed arrows) as it passes through mesocolic
defect.
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A fifth CT sign identified in our study was the pinch sign, which is not
seen in all patients. In this study it was found in patients with and those
without internal hernia, depending on the laxity of the mesocolic defect. The
pinch sign consists of a pinching mass effect on herniated small-bowel loops
or the jejunal efferent limb where they pass through the fatty defect in the
transverse mesocolon. We used this sign to assist us in recognizing the
cephalocaudal location of the mesocolic defect and thus the cephalocaudal
location of the transverse mesocolon so that multiple loops of jejunum
cephalic to this level might be more easily recognized (Figs.
10 and
11). If multiple redundant
loops of small bowel are seen in the left upper quadrant of the abdomen
cephalic to the level of the jejunum where it passes through the transverse
mesocolic defect, internal hernia can be confidently diagnosed.
Discussion
Radiologists are usually attuned to the more serious complications of
bariatric surgery, such as anastomotic leak, anastomotic strictures, and
bleeding secondary to severe clinical presentation. Among patients who arrive
in emergency departments and outpatient imaging centers with vague abdominal
pain after gastric bypass surgery, internal hernia has become an increasingly
more recognized complication. Because the morbidity and mortality of internal
hernia are similar to those of other serious complications, an understanding
of the less well understood imaging findings of this complication is important
[1].
Knowledge of the initial retrocolic Rouxen-Y gastric bypass surgical
procedure is considered critical to appreciating the complications. The
surgical technique consists of first making a transverse mesocolic defect
through which the small bowel can be accessed. The jejunum is divided
approximately 15–30 cm from the ligament of Treitz; 100–150 cm of
jejunum distal to the division is pulled up; and a side-to-side
jejunojejunostomy anastomosis is made to reconnect the proximal jejunum to the
efferent limb. The efferent limb is pulled through the surgically created
defect in the transverse mesocolon, and a suture is placed at the defect to
hold the Roux limb in place. With rapid weight loss, it is this defect that
can become lax and allow herniation of small bowel. The fundus is stapled to
produce an approximately 30-mL gastric pouch. To complete the bypass
procedure, a side-to-side gastrojejunostomy anastomosis is made between the
pouch and the 100- to 150-cm Roux limb. An overview of the procedure is shown
in Figures 12A,
12B,
12C, and
12D.
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Fig. 12B —Overview of retrocolic Roux-en-Y gastric bypass procedure.
(Reprinted with permission from
www.laparoscopy.com;
courtesy of Schauer P, Cleveland Clinic, Cleveland, OH) Drawing shows
construction of retrogastric–retrocolic tunnel (circle) in
mesocolon anterolateral in relation to ligament of Treitz. Roux limb will be
passed through tunnel.
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Fig. 12C —Overview of retrocolic Roux-en-Y gastric bypass procedure.
(Reprinted with permission from
www.laparoscopy.com;
courtesy of Schauer P, Cleveland Clinic, Cleveland, OH) Drawing shows distal
end of Roux limb attached to proximal segment of jejunum (arrowhead)
approximately 15–30 cm from ligament of Treitz. Proximal end (dashed
arrow) of Roux limb is pulled through mesocolic tunnel
(circle).
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Fig. 12D —Overview of retrocolic Roux-en-Y gastric bypass procedure.
(Reprinted with permission from
www.laparoscopy.com;
courtesy of Schauer P, Cleveland Clinic, Cleveland, OH) Drawing shows
anastomosis between gastric pouch (solid arrows) and proximal Roux
limb (dashed arrows). Inset shows stapled anastomosis reinforced with
stitches.
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In our evaluation, 13 (48%) of 27 surgically proven internal hernias were
prospectively identified as internal hernias, and seven (26%) were diagnosed
as small-bowel obstruction. In the other seven cases, the findings were
reported as negative for acute abdominal abnormality. Retrospective analysis
of these cases led to the description of four CT signs of internal hernia.
These signs were the presence of multiple small-bowel loops cephalic to the
transverse mesocolon, high position of the distal jejunal anastomosis,
ascending course of tightly clustered small-bowel mesenteric blood vessels,
and dilatation of the efferent jejunal limb. None of these signs was present
in the five cases in which the initial diagnosis of internal hernia was proved
incorrect at surgery.
The purpose of the study was to increase the sensitivity and specificity of
diagnosis of internal hernia to assist surgeons in accurate initial diagnosis
and treatment. A limitation was the small size of the control group. We hope
these signs will be useful to general abdominal radiologists who are not
familiar with gastric bypass or the altered anatomic features associated with
this surgical procedure.
Acknowledgments
We thank the Weight Loss Surgery Program at Baylor University Medical
Center, Joseph A. Kuhn, and Todd M. McCarty.
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Abstract
Introduction
