DOI:10.2214/AJR.04.1668
AJR 2006; 186:104-109
© American Roentgen Ray Society
CT of Acute Biliopancreatic Limb Obstruction
Kumaresan Sandrasegaran1,
Dean D. T. Maglinte1,
Arumugam Rajesh2,
John C. Lappas1 and
Thomas J. Howard3
1 Department of Radiology, Indiana University School of Medicine, UH 0279, 550 N
University Blvd., Indianapolis, IN 46202.
2 Department of Radiology, University Hospitals of Leicester, Leicester General
Hospital, Leicester, LE5 4 PW, United Kingdom.
3 Department of Surgery, Indiana University School of Medicine, Indianapolis, IN
46202.
Received October 26, 2004;
accepted after revision December 17, 2004.
Address correspondence to K. Sandrasegaran
(ksandras{at}iupui.edu).
Abstract
OBJECTIVE. Our objective was to report the CT features of
biliopancreatic limb (afferent loop) obstruction.
CONCLUSION. Acute biliopancreatic limb obstruction has typical CT
features. Given its high morbidity and rate of reoperation, it is useful to
make this specific diagnosis instead of reporting the findings as
postoperative small bowel obstruction.
Keywords: afferent loop • biliopancreatic loop • CT imaging • intestinal obstruction • postoperative complications
Introduction
The loop of bowel draining the biliary and exocrine pancreatic secretions
after gastrointestinal surgery is termed the "biliopancreatic
limb." The biliopancreatic limb is an afferent loop. However, in some
types of abdominal surgery, such as Roux-en-Y gastric bypass, there are two
afferent segments, one at the gastrojejunostomy and another at the
jejunojejunostomy. To avoid confusion, many surgeons use the term
biliopancreatic limb to describe the latter
[1]. The biliopancreatic limb
constructed in pancreatic surgery such as the Whipple procedure is
anatomically different from the loop used in gastric surgery such as Billroth
II and Roux-en-Y gastric bypass (Figs.
1A and
1B). Obstruction of this loop
is a rare but significant postoperative complication. Clinical diagnosis of
this condition is difficult because symptoms such as nausea and postprandial
fullness are common postsurgical complaints and nonspecific. Abdominal
distention due to bowel obstruction is hard to discern in the morbidly obese
after Roux-en-Y gastric bypass. The best preoperative imaging technique for
assessing bowel obstruction is widely recognized as CT
[2,
3], although even with CT,
diagnosis is not always easy.
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Fig. 1A —Line diagrams showing anatomy after Whipple and gastric
bypass surgery. Illustrations courtesy of Office of Visual Media, Indiana
University Trustees, Indianapolis, IN. Anatomy after pylorus-preserving
Whipple procedure in which cuff of duodenum is spared. Original Whipple
procedure is shown (inset). Procedure entails radical dissection of pancreatic
head, adjacent nodes, right half of omentum, gallbladder, common bile duct,
and most or all of duodenum, followed by gastrojejunostomy/duodenojejunostomy,
pancreaticojejunostomy, and hepaticojejunostomy. Position of pyloric sphincter
is marked with PS.
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Fig. 1B —Line diagrams showing anatomy after Whipple and gastric
bypass surgery. Illustrations courtesy of Office of Visual Media, Indiana
University Trustees, Indianapolis, IN. Anatomy after Roux-en-Y gastric bypass
surgery. Retrocolic version is shown. Note short afferent loop, usually less
than 2.5 cm in length, at gastrojejunostomy (labeled afferent limb). Efferent
loop of jejunum joins second much longer afferent loop (labeled duodenum) at
jejunojejunostomy. Second afferent loop is biliopancreatic limb.
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There are case reports and small series of CT features of biliopancreatic
(afferent) limb obstruction. These reports have almost been exclusively
related to Billroth II surgery and were published before availability of MDCT
and coordinated multiplanar reformatting
[4–19].
A literature review revealed sparse information on CT findings of
biliopancreatic limb obstruction after other more commonly performed abdominal
surgeries. We present the CT features seen in eight patients who had acute
postoperative biliopancreatic limb obstruction.
Materials and Methods
We reviewed the surgical database of 478 patients with pancreatic and
gastric surgery performed at our affiliated institutions between January 2002
and December 2003. The surgical procedures were bariatric Roux-en-Y gastric
bypass (n = 328), other gastric surgery including total gastrectomy
with Roux-en-Y esophagojejunostomy (n = 41), Whipple procedure
(n = 82), and other pancreatic surgery including Puestow
pancreaticojejunostomy, a Frey procedure, and Roux-en-Y cystojejunostomy
(n = 27). This review revealed 11 patients (2.3% of review group)
with suspected biliopancreatic limb obstruction. Three patients had either no
imaging studies (n = 2) or only upper gastrointestinal contrast
series (n = 1) supporting the diagnosis. The remaining eight patients
with appropriate CT examinations formed the study group.
A total of 15 CT examinations and one CT enteroclysis performed in these
patients between presentation with symptoms of biliopancreatic limb
obstruction and operative treatment were evaluated. One patient had a CT
examination without oral contrast followed by CT enteroclysis on the same day
of acute presentation. Two other patients presented with recurrent symptoms
over 2- and 6-month periods and had five and four CT examinations,
respectively. Within 12 hr of the final CT examination, emergency surgery was
performed on these two patients. CT studies were performed using the Mx8000
(4-channel) or IDT (16-channel) CT scanners (Philips Medical Systems). Of the
15 CT examinations, 13 were performed with 500–750 mL of 2% meglumine
diatrizoate (Gastrografin, Bracco) as oral contrast. IV contrast medium was
given in all CT examinations; 150 mL of iopamidol (Isovue-300, Bracco) was
used. The effective slice width was 6.5 mm for the 4-channel scanner and 5 mm
for 16-channel scanners with a longitudinal reconstruction of 3.0 and 2.5 mm,
respectively.
A CT enteroclysis examination was performed under conscious sedation and
topical anesthesia was applied to the nasopharynx. A nasoenteric tube
(Maglinte multipurpose tube, Cook) was placed in the proximal jejunum under
fluoroscopic guidance. Positive enteral contrast was infused. CT was performed
subsequently without IV contrast using parameters described elsewhere
[20]. Reformats performed in
the coronal and sagittal planes were routinely saved on the PACS and were
available for review.
The images were reviewed to initially confirm the presence of a distended
segment of small bowel. Its position, course, relationship to the mesenteric
root, site of obstruction, and possible cause or complications were recorded
by two experienced abdominal radiologists in consensus. Images obtained before
June 2002 were viewed on hard copy. More recent images were evaluated on
Extended Brilliance workstations (Philips Medical Systems) with multiplanar
reformats. A one-tailed Student's t test (Excel, Microsoft) was used
to determine if nonvisualization of valvulae was associated with a more
distended bowel statistically.
Results
The study group consisted of four men and four women. The mean age was 60.6
years (range, 48 to 76 years). The patients had pancreatic (n = 4) or
gastric (n = 4) surgery. One patient had previous pancreatic surgery
at an outside hospital on an unknown date. In the other seven patients, the
presentation with biliopancreatic limb obstruction occurred 1–169 days
after surgery (mean, 33 days).
The CT findings and other results are summarized in
Table 1. Obstructed loops
originated from the right upper quadrant and extended inferiorly to midline or
left of abdomen. The course of the biliopancreatic limb was best seen on
coronal images in all patients (Figs.
2A,
2B,
2C,
3A, and
3B). The site of obstruction
was usually in the midleft abdomen. In patients with Roux-en-Y gastric bypass,
however, the transition zone was variable in location and obstructed loops
could be found in the right or left abdomen (Figs.
2A,
2B,
2C, and
4). In all cases the transition
point was short, less than 5 cm, and was definable on axial CT or coronal
reformats. Obstructed loops in all patients were completely or almost
completely fluid filled with paucity of luminal air. Orally ingested contrast
medium was seen in only two obstructed loops. The maximum caliber of the
obstructed loop ranged from 3.1 to 6.4 cm in diameter. Nonvisibility of
valvulae tended to be associated with greater distention of the obstructed
loop (0.05 < p < 0.1).
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Fig. 2A —49-year-old woman with Roux-en-Y gastric bypass surgery
(patient 1 in Table 1). Images
taken 12 days after surgery. Contrast-enhanced axial CT image of abdomen.
Distention of duodenum (black arrow) is seen. Proximal
biliopancreatic loop runs behind superior mesenteric vessels (white
arrowheads).
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Fig. 2B —49-year-old woman with Roux-en-Y gastric bypass surgery
(patient 1 in Table 1). Images
taken 12 days after surgery. Distention of proximal jejunum (white
arrows) is seen. Point of obstruction is at site of surgical clips
(black arrowhead) close to midline. Obstructed loops are on right
side.
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Fig. 3B —50-year-old man with previous pancreaticocystojejunosotmy
(patient 5 in Table 1). Axial
image shows that loop (white arrow) lies anterior to mesenteric root
containing branches of superior mesenteric vessels (black arrows).
Note valvulae in obstructed loop (arrowheads). Transition point (not
shown) was abrupt and adhesions were found on subsequent surgery.
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Fig. 4 —48-year-old woman (patient 2 in
Table 1) with Roux-en-Y gastric
bypass. Axial CT image obtained 1 day after surgery shows distended duodenum
without significant wall thickening or enhancement (white arrow).
More distant biliopancreatic limb shows wall enhancement and thickening
(black arrows). There is edema of adjacent mesentery and blurred
mesenteric vessels that are soft signs for bowel ischemia (white
arrowhead). Surgery on same day showed necrosis with volvulus of
biliopancreatic loop. Unlike in Figs.
2A,
2B, and
2C, distended loops are on
left. Note pancreatic head (black arrowhead).
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The cause of obstruction could be identified on CT in seven cases. In
patient 1 (Table 1), the
transition point was at the site of surgical staples and associated with
distention of the gastric remnant (Figs.
2A,
2B, and
2C); the obstruction was due to
an anastomotic stricture. Patients 3, 4, 5, and 7 showed narrow zones of
transition; adhesions were thought to be the cause and proven on subsequent
surgery. CT examination of patient 2 showed thickened, enhancing
biliopancreatic limb, adjacent mesenteric edema, and blurred mesenteric
vessels consistent with bowel ischemia
(Fig. 4). Surgery performed 7
hr after the scan found a volvulized afferent loop with transmural necrosis.
In case 8, both the efferent and biliopancreatic loops were distended with
intense enhancement of the midjejunum over a 15-cm segment. Bowel ischemia and
probable volvulus were predicted based on CT findings. Subsequent surgery
showed an internal hernia of the afferent and efferent loops with bowel
necrosis. The cause of biliopancreatic limb obstruction was incorrectly
surmised as adhesions in patient 6. The CT showed high-density material in the
obstructed biliopancreatic limb (Figs.
5A and
5B). At surgery, a bleeding
vessel was ligated from the staple line and intraluminal hematomas were
evacuated. The biliopancreatic limb obstruction subsequently resolved.
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Fig. 5A —64-year-old man with gastric cancer (patient 6 in
Table 1). Coronal reformats of
CT performed with IV but without oral contrast 2 days after Roux-en-Y
esophagojejunostomy. Image shows possible benefit of using water rather than
positive oral contrast in diagnosis of biliopancreatic limb obstruction.
Obstruction was found at surgery to be intraluminal hematoma from bleeding
vessel.
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Fig. 5B —64-year-old man with gastric cancer (patient 6 in
Table 1). Distended
biliopancreatic limb with high-density material (white arrows) is
seen. Note distended common bile duct (arrowheads, A and
B) and nondistended collapsed distal small bowel loops (black
arrow).
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Complications after biliopancreatic limb obstruction were seen in five
patients and included bile leak (n = 1), pancreatitis (n =
1), perforation (n = 2), abscess (n = 2), and fistula
(n = 1). Gastric perforation was noted in one patient at surgery.
The original dictated reports in three of the CT examinations and
corresponding CT enteroclysis examination diagnosed afferent loop obstruction.
The remaining imaging studies were initially interpreted as postoperative
small bowel obstruction (n = 10) or ileus (n = 2). All eight
patients had surgical reexploration after 0–2 days of diagnosis of
imaging to treat the obstruction or its complication.
Discussion
An afferent loop may be created during an esophago-, gastro-, or
enteroenterostomy. In Billroth II surgery this is the blindly ending duodenal
remnant that drains the biliary and pancreatic secretions. Gastroenterostomy
is also created during pancreatic or bariatric surgery. Whipple procedure is
the only curative surgery for patients with carcinoma of the head of the
pancreas (Fig. 1A). The
afferent loop in this surgery is the blindly ending segment of jejunum that
drains the biliary and pancreatic secretions. Surgical procedures for chronic
pancreatitis, such as the Puestow and Frey procedures, also have a blindly
ending jejunal segment forming the pancreatic limb. Rouxen-Y gastric bypass is
the preferred method of bariatric gastric surgery
[21], resulting in reduction
of the excess weight and resolution of comorbidities such as type 2 diabetes
mellitus, hypertension, and sleep apnea within 1 year of this surgery
[22]. The surgical anatomy of
this operation is shown in Fig.
1B. The second afferent (biliopancreatic) loop made up of the
duodenum and proximal jejunum drains the biliary and pancreatic secretions.
This loop is excluded from the digestive pathway and is typically 75 cm long
in the morbidly obese (body mass index [BMI] > 40 kg/m2) and at
least 150 cm in the super obese (BMI > 50 kg/m2)
[23]. Thus, the afferent loop
fashioned during bariatric surgery is much longer than that constructed in
Billroth surgery.
The term biliopancreatic limb obstruction is preferred over afferent loop
obstruction by our surgeons for two reasons. First, some of the unusual
complications of obstruction of this loop are due to its role as conduit of
bile and pancreatic exocrine secretions. Second, in some surgical procedures,
such as Roux-en-Y gastric bypass, two afferent loops are present.
Previous reports have described the CT features of biliopancreatic limb
obstruction in a total of 21 patients, 18 of whom had Billroth II surgery
[4–19].
This procedure is less commonly performed now because of the efficacy of
medical therapy against peptic ulcer disease. Two previous reports
[12,
18] included cases of Whipple
and esophagojejunostomy but did not draw attention to the differences in
appearance of biliopancreatic limb obstruction in patients with bariatric or
pancreatic surgery. The presence of a dilated loop behind the superior
mesenteric vessels and in front of the aorta has been regarded as a sign of
biliopancreatic limb obstruction
[7,
9–11,
13,
18]. This applies to cases of
Billroth II gastrectomy, Roux-en-Y esophagojejunostomy, and Roux-en-Y gastric
bypass in which the duodenum is preserved. After some types of pancreatic
surgery, including Whipple procedure, the biliopancreatic loop is a segment of
jejunum and therefore lies anterior to the mesenteric root (Figs.
3A and
3B). Another well-described
appearance of biliopancreatic limb obstruction is the passage of the
obstructed loop across midline to the left side of the abdomen. This
appearance was seen after pancreatic surgery and esophagojejunostomy. However,
after Roux-en-Y gastric bypass, in which the biliopancreatic limb can be very
long, the site of obstruction was variable. The presence of valvulae has also
been regarded as a cardinal feature in discriminating this type of obstruction
from fluid collections. This feature may not be reliable; as the
biliopancreatic limb becomes more distended, the valvulae may become effaced.
The course of the obstructed fluid-filled loops of bowel and its connection
with the nondistended small bowel at the point of obstruction are sufficient
features to separate biliopancreatic limb obstruction from postoperative fluid
collection. We found coronal reformats helpful to identify the course of the
obstructed loop, allowing differentiation from fluid collections. Associated
findings include mesenteric edema, and biliary and pancreatic duct
dilation.
The incidence of biliopancreatic limb obstruction after gastric surgery
(Billroth II and Roux-en-Y gastric bypass) is low, approximately
0.3–0.6% [1,
24]. In our series, the
incidence was 2.3% (11/478), which may be partly explained by inclusion of
pancreatic operative procedures and by the complexity of surgery at our
institutions. Some patients in our series had corrective surgery after
procedures performed elsewhere. The cause of this type of obstruction includes
adhesions, recurrent tumor, marginal ulceration, bezoar, anastomotic
stricture, retrograde intussusception, volvulus, and internal hernia
[1,
25]. It is important for the
radiologist to identify the cause of the obstruction because this may affect
clinical management. At our institution, partial adhesive obstruction, even
high grade, is treated initially with nasojejunal suction. Internal hernia or
volvulus requires emergent surgery. Tumor recurrence may necessitate a
combination of surgery and oncologic therapy. Bezoar is usually treated
conservatively.
Biliopancreatic limb obstruction has unique complications. Although we are
not aware of comparative studies, our experience suggests that adverse events
are more frequent with this type of obstruction compared with routine
postoperative small bowel obstruction. Five of eight patients in this study
had at least one complication. As this loop is blindly ending, it may be
subject to higher pressures when obstructed and is more likely to become
ischemic. Perforation of the obstructed loop with enterocutaneous fistula or
abdominal abscess may occur. Gastric perforation is a rare but often fatal
complication [26].
Pancreatitis may occur after biliopancreatic limb obstruction, probably
because of increased pancreatic ductal pressure
[12,
15,
27]. Bile duct dilation or
perforation may also be seen
[8]. All patients in our series
required emergency or semiemergency surgical correction of the obstruction or
its complications. In this study we have discussed acute biliopancreatic limb
obstruction. This article does not deal with afferent loop syndrome, which is
a more indolent type of obstruction with a different presentation, such as
malabsorption from bacterial overgrowth, and prognosis.
Our study has the limitations of a retrospective survey. A prospective
study in a reasonable time frame is impractical given the relative rarity of
this condition. Although the number of cases is small, this series is one of
the largest radiologic reviews to date of this important postoperative entity.
Many of the original dictated CT reports did not make the diagnosis of
biliopancreatic limb obstruction and merely indicated the presence of
postoperative small bowel obstruction. Given the incidence of complications
and the almost universal need for surgical reexploration in biliopancreatic
limb obstruction, we think it is worth making this specific diagnosis. The
radiologist should also ascertain the cause and possible complications of this
type of bowel obstruction.
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Abstract
Introduction
