Keywords
disconnected pancreatic duct syndrome - acute necrotizing pancreatitis - magnetic
resonance cholangiopancreatography - pancreatic fistula - pancreatic pseudocyst
Introduction
Disconnected pancreatic duct syndrome (DPDS) is most frequently seen in cases of acute
necrotizing pancreatitis and usually goes unrecognized and untreated because of its
varied clinical presentation, absence of clearly defined diagnostic criteria, and
low degree of recognition by clinicians.[1]
[2]
[3]
[4]
Early detection of DPDS in acute pancreatitis is essential since a delayed diagnosis
could result in increased morbidity, longer hospital stays, and higher medical costs.
Cross-sectional imaging is primarily used for diagnosis because it is noninvasive
and permits pancreatic imaging distal to the disconnection, as opposed to the invasive
traditional gold standard technique of endoscopic retrograde cholangiopancreatography
(ERCP), which only shows termination of the duct's proximal portion and carries a
higher risk of complications. Studies have explored computed tomography (CT), magnetic
resonance cholangiopancreatography (MRCP), and ERCP to identify the best option for
diagnosis. They have concluded that although the invasive traditional gold standard
ERCP is both a diagnostic and therapeutic procedure,[5] MRCP is preferred due to its noninvasive nature and lesser risk of complications.[6]
DPDS occurs in roughly 50% of walled-off pancreatic necrosis patients who receive
percutaneous drainage[7]
[8] and a majority of DPDS cases do not respond to conservative therapies which calls
for hybrid approaches. Surgical methods of management of DPDS are no longer favored
due to their invasive nature.[9]
[10] Endoscopic transluminal drainage is currently the standard preferred procedure for
managing these patients.[1]
[11]
[12]
Although it may become a significant long-term issue in instances of necrotizing pancreatitis,
only a few studies have discussed the imaging characteristics of DPDS. However, neither
the standardized diagnostic criteria nor the management strategy for DPDS is currently
recognized worldwide.[13] With improved understanding and the application of various imaging aspects, DPDS
can be detected early via imaging, leading to a rapid diagnosis and early treatment.
We thus aim to evaluate the radiological imaging features in establishing the diagnosis
of pancreatic duct disconnection along with outlining the effective management protocols.
Materials and Methods
Patients and Control Subjects
Our study is a retrospective observational study having a study population of 63 patients
in the age group of 18 to 70 years with radiological or clinical suspicion or diagnosis
of pancreatic duct disconnection. The study was conducted after Institutional Review
Board and Ethics Committee approval of the study protocol. Data collection was undertaken
after obtaining consent from the Institutional Ethics Committee and Medical Superintendent
in December 2022. A sample size of 63 patients was identified after applying inclusion
and exclusion criteria.
Inclusion criteria comprised patients with radiological or clinical suspicion/diagnosis of pancreatic
duct disconnection who undergo imaging.
Exclusion criteria comprised patients with imaging of suboptimal quality for visualization of ductal
anatomy or with early resolution of symptoms of pancreatitis.
ERCP findings confirming the diagnosis and raised amylase values in the necrotic collection
higher than three times the reference range were considered as proven cases of DPDS.[13]
[14]
Image Acquisition and Postprocessing
Upon clinical diagnosis, patients underwent contrast-enhanced CT abdomen and pelvis
using Philips Incisive 128-slice or Philips Brilliance Big Bore 64- slice CT machines
and/or magnetic resonance imaging (MRI) abdomen with MRCP using 1.5-T MR imager (Philips
Signa) with a phased-array torso coil.
CT images were acquired in axial sections in arterial and portal venous phase; parenchymal
phase and delayed portal venous phase were acquired if indicated. Raw data was generated
in axial planes with 3-mm thickness and later reconstructed in coronal and sagittal
planes with a section thickness of 3 mm. T2-weighted SSFP (axial and coronal), axial
and coronal three-dimensional (3D) MRCP, axial T2 FS, axial diffusion-weighted imaging,
and axial two-dimensional FIESTA sequences were acquired on MRI. MRCP was obtained
in the coronal plane using T2-weighted acquisitions, and the individual slices and
reconstructed maximum intensity projections were used to display the 3D MRCP. Images
were transferred to picture archiving and communication system for review.
Image Analysis
The following definitions were used to retrospectively analyze and diagnose DPDS.
CT parameters included length of parenchymal necrosis involving the entire width of the pancreas
with a cutoff value of > 2 cm; presence of disconnection of main pancreatic duct (MPD)
with the presence of a variable portion of viable parenchyma upstream to the disconnection;
site of duct disconnection; collection replacing the parenchyma along the course of
MPD; communication of MPD with the collection; angle of MPD with the collection; and
presence of viable pancreatic tissue upstream to disconnection ([Fig. 1]).
Fig. 1 Postcontrast axial computed tomography (CT) section of the abdomen (A) and (B) showing acute necrotizing pancreatitis with necrotic collection in the body of pancreas
and upstream dilated duct communicating with it. (C) Postcontrast oblique coronal CT section of the abdomen showing upstream duct communicating
with the collection at an angle of 90 degrees.
MRCP/MRI parameters assessed were length of parenchymal necrosis involving the entire width of the pancreas
with a cutoff value of > 2 cm; presence of disconnection of MPD with the presence
of a variable portion of viable parenchyma upstream to the disconnection; site of
duct disconnection; collection replacing the parenchyma along the course of MPD; presence
of upstream dilated MPD; and angle of MPD with the collection ([Fig. 2]).
Fig. 2 Site of disconnection of main pancreatic duct (MPD) as seen on postcontrast axial
computed tomography (CT) section (A) and axial section on magnetic resonance cholangiopancreatography (MRCP) (B).
Apart from this, the laboratory parameters such as serum amylase/lipase and amylase/lipase
values from the collection were assessed and the clinical management and outcome on
follow-up was studied.
The collected data was tabulated and analyzed to identify the various imaging features
of pancreatic duct disconnection syndrome on CT and MRI. The single most accurate
parameter and a combination of parameters to aid in the diagnosis of DPDS were also
evaluated. The comparison of overall accuracy of CT and MRI in diagnosing DPDS along
with the clinical management and respective outcome on follow-up was studied.
Statistical Analysis
The presentation of categorical variables was done in the form of number and percentage
(%). The quantitative data were presented as the means ± standard deviation and as
median with 25th and 75th percentiles (interquartile range) while comparison of the
accuracy rate was analyzed using Fisher's exact test. A p-value of less than 0.05 was considered statistically significant. The data entry
was done in a Microsoft Excel spreadsheet and the final analysis was done with the
use of Statistical Package for Social Sciences (SPSS) software (IBM, Chicago, United
States, ver 25.0.) and Microsoft Word and Excel were used to generate graphs and tables.
Results
A total of 63 patients were included among which majority of the subjects were in
the age group of 31 to 40 years (31.75%) and ethanol consumption was the most common
etiologic factor (60.31% cases). Clinical diagnosis in 29 cases was acute necrotizing
pancreatitis and 14 cases were of acute on chronic pancreatitis. Nine cases of recurrent
acute pancreatitis, six cases of chronic pancreatitis, and five cases of traumatic
pancreatic transection were also included. The most common complaint at the time of
presentation was epigastric pain abdomen in 59 cases.
We considered either ERCP findings or raised amylase values in the necrotic collection
higher than three times the reference range as proven cases of DPDS,[13]
[14] since all cases included in our study were not proven using the conventional gold
standard technique of ERCP. This resulted in 36 proven cases out of which 31 had undergone
CT and 30 had undergone MRI.
CT Evaluation
CT was available for 54 out of 63 patients at the time of study ([Table 1]). DPDS was diagnosed on CT in 55.55% cases overall. Presence of viable parenchyma
upstream to the disconnection, length of necrotic component in the pancreas > 2 cm,
and ductal discontinuity were the most frequently identified parameters. The accuracy
rate of CT parameters in 31 proven cases of pancreatic duct disconnection was highest
for the length of necrotic component in the pancreas > 2.0 cm and collection along
the course of MPD and ductal discontinuity (83.87% each). The overall accuracy rate
of DPDS diagnosed on CT in proven cases was 61.29%.
Table 1
Distribution of CT parameters (n = 54)
|
CT parameters
|
Frequency
|
Percentage
|
|
Length of necrotic component in pancreas (cm) {> 2 cm}
|
46
|
85.18
|
|
Collection along the course of MPD
|
46
|
85.18
|
|
Presence of dilated MPD with disconnected segment
|
28
|
51.85
|
|
Presence of viable parenchyma upstream to the disconnection
|
50
|
92.6
|
|
Ductal discontinuity
|
|
No
|
6
|
11.11
|
|
Suspicious
|
1
|
1.85
|
|
Yes
|
47
|
87.03
|
|
Communication of MPD with collection
|
|
No
|
8
|
14.81
|
|
Suspicious
|
7
|
12.96
|
|
Yes
|
32
|
59.25
|
|
N/A
|
7
|
12.96
|
|
Angle between WON and duct (90°)
|
|
< 90°
|
1
|
1.85
|
|
90°
|
28
|
51.85
|
|
N/A
|
25
|
46.29
|
Abbreviations: CT, computed tomography; MPD, main pancreatic duct; N/A, not available;
WON, walled-off necrosis.
MRI Evaluation
MRI was available for 50 out of 63 patients at the time of study ([Table 2]). DPDS was diagnosed on MRI in 84% cases. Ductal discontinuity, communication of
MPD with collection, and dilated MPD with disconnected segment were the most frequently
identified parameters. In 30 proven cases of pancreatic duct disconnection, ductal
discontinuity and communication of MPD with collection were the most accurate parameters
in diagnosing DPDS (86.67% each). Angle of 90 degrees between the MPD and presence
of collection were the next most accurate parameters (83.3% each). The overall accuracy
rate of MRI in diagnosing DPDS in proven cases was 90.00%.
Table 2
Distribution of MRI parameters (n = 50)
|
MRI parameters
|
Frequency
|
Percentage
|
|
Length of necrotic component in pancreas (cm) {> 2 cm}
|
39
|
78.00
|
|
Ductal discontinuity
|
46
|
92.00
|
|
Collection along the course of MPD
|
39
|
78.00
|
|
Communication of MPD with collection
|
41
|
82.00
|
|
Presence of dilated MPD with disconnected segment
|
40
|
80.0
|
|
Angle between WON and duct (90°)
|
|
< 90°
|
1
|
2.0
|
|
90°
|
39
|
78.00
|
|
N/A
|
10
|
20.0
|
Abbreviations: MPD, main pancreatic duct; MRI, magnetic resonance imaging; WON, walled-off
necrosis.
On assessing imaging features of pancreatic duct disconnection in 30 proven cases,
the diagnostic accuracy rate of CT (61.29%) was significantly lower as compared with
MRI (90%) (p-value = 0.03). Majority of the cases of DPDS underwent cystogastrostomy (44.44%),
ERCP stenting was performed in 19.05% cases, 15.87% cases received conservative management,
11.11% cases underwent pigtail drainage, and 6.35% cases underwent surgical procedures
such as pancreaticojejunostomy or open necrosectomy.
On follow-up of 63 patients, 29 had resolution of symptoms, clinical reduction of
symptoms was seen in 12 cases while 9 cases developed recurrence; 5 cases succumbed
to other causes and 8 cases developed complications such as postoperative jejunal
fistula, gastric outlet obstruction, pancreatic diabetes, splenic artery pseudoaneurysm,
and pancreatic ascites (1 case each) while 3 patients developed pancreaticopleural
fistula.
Discussion
We undertook this study to identify and establish the imaging features of DPDS, identify
the most important radiological imaging criterion for diagnosis and evaluate the management
protocols of pancreatic duct disconnection. The management of subjects with the outcome
on clinical or radiological follow-up was also assessed.
Based on existing literature, multiple parameters were identified and studied on CT
and MRI of selected patients to formulate an approach on imaging to aid in early diagnosis
of DPDS. Out of 63 identified cases included in our study, 36 of them were confirmed
to have DPDS on ERCP or raised amylase levels in the necrotic collection (more than
three times the reference range) and were treated clinically as DPDS.[13]
[14]
The accuracy rate of CT parameters in our 36 proven cases of pancreatic duct disconnection
was highest for the length of necrotic component in the pancreas (> 2.0 cm), collection
along the course of MPD, and ductal discontinuity (83.87% each). It was therefore
seen that a combination of these parameters was accurate for diagnosis on CT. However,
communication of MPD with collection and presence of an angle of 90 degrees between
the collection and MPD had a lower accuracy rate, thus proving the poor sensitivity
of CT in depicting ductal anatomy.
MRI/MRCP is now considered the first-line diagnostic modality for evaluation of ductal
pathologies considering its noninvasive nature and excellent depiction of pancreaticobiliary
pathologies.[6]
[15]
[16] Secretin-enhanced MRCP was not a part of the routine MRCP protocol in our institution
due to its higher cost, increased scanning time, and lesser availability.
Ductal discontinuity and communication of MPD with collection had an accuracy of 86.67%
each on MRI. MRI was seen to be a better modality in depicting ductal anatomy compared
with CT. The overall accuracy rate of CT in diagnosing DPDS was significantly lower
as compared with MRI (63.33% vs. 90%, respectively) (p-value = 0.03; significant) ([Fig. 3]).
Fig. 3 Contrast-enhanced computed tomography (CT) section of the abdomen (A) in pancreatic parenchymal phase shows acute necrotizing pancreatitis with necrotic
collection in the neck and proximal body of pancreas with upstream dilated duct communicating
with it; axial magnetic resonance cholangiopancreatography (MRCP) section (B) and three-dimensional (3D) MRCP reconstructed image (C) confirming the same.
Therefore, MRCP can be considered more precise in diagnosing DPDS before clinical
symptoms develop. A single best parameter could not be established on both CT and
MRI; however, a combination of parameters as described above can be used to diagnose
DPDS.
A study performed in by Kamal et al[6] in 2014 in 28 patients demonstrated that the pancreatic duct communication with
a collection could be included or excluded in 19 (68%) cases on CT and an uncertain
diagnosis was given in 9 (32%) cases, while on MRI/MRCP a certain diagnosis was made
in 26 (93%) cases and an uncertain diagnosis in 2 (7%) cases ([Table 3]).
Table 3
Presence of ductal communication with pancreatic collection compared with a prior
study conducted by Kamal et al[6]
|
Kamal et al (39)
|
Our study
|
|
Ductal communication with a collection (n = 28)
|
Ductal communication with a collection
|
|
CT
|
MRI
|
CT (n = 31)
|
MRI (n = 30)
|
|
Present
|
13
|
20
|
18
|
26
|
|
Absent
|
6
|
6
|
5
|
4
|
|
Uncertain
|
9
|
2
|
8
|
0
|
Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging.
Trauma cases are exceptions as there is no well-defined collection or obvious ductal
injury seen on the first presentation, hence, only a suspicion of duct disconnection
can be raised in such cases. ERCP is feasible in these patients due to the nonfriability
of MPD and can be accompanied by therapeutic stenting as seen in most of our cases
(3 out of 5 cases of trauma to the pancreas). Thus, the criteria for diagnosis of
DPDS defined in our study are not applicable to such patients ([Fig. 4]).
Fig. 4 Postcontrast axial (A) computed tomography (CT) section of the abdomen showing American Association for
the surgery of Trauma (AAST) grade III pancreatic injury with possible ductal disconnection.
Coronal (B) magnetic resonance cholangiopancreatography (MRCP) image of the same patient on
follow-up showed significant pancreatic and peripancreatic collection with prominent
upstream duct showing communication with the collection. Poststenting imaging (C and D) showed near total resolution of the collection with sustained prominence of the
duct.
The presence of DPDS could not be evaluated in cases of chronic pancreatitis[17] due to the absence of collections and preexisting presence of dilated ducts and
strictures in these cases. However, these cases were treated as confirmed cases of
DPDS on clinical suspicion and ductal discontinuity was eventually confirmed on ERCP
([Fig. 5]).
Fig. 5 Axial computed tomography (CT) (A) and magnetic resonance cholangiopancreatography (MRCP) (B) images of a 40-year-old female patient with pancreatic adenocarcinoma masquerading
as acute necrotizing pancreatitis and pancreatic duct disconnection syndrome. Features
of necrotizing pancreatitis are seen with dilated duct communicating with necrotic
collection in the body of the pancreas.
One of the cases was that of pancreatic adenocarcinoma masquerading as acute necrotizing
pancreatitis with duct disconnection. Histopathological examination of the tissue
obtained during ERCP confirmed the diagnosis. It was thus noted that the remote possibility
of underlying malignancy should be ruled out in patients with persistent collections
which do not resolve despite treatment.
The traditional modality of open surgical management has been demoted to the position
of last resort as a therapeutic approach with minimally invasive treatment preferred
currently.[7]
[9]
[14]
Management has switched from early debridement to delayed intervention, which has
been found to have decreased morbidity and mortality. Radiological approaches are
used to monitor treatment efficacy and provide direction for draining collections
in treating problems due to acute pancreatitis.
Thiruvengadam et al[18] performed a study in 2022 where 171 patients with necrotizing pancreatitis undergoing
conservative and/or surgical management ([Table 2]) were identified and followed up. Forty-eight patients (28.1%) developed DPDS and
the rate of DPDS incidence was 40% (42 patients) in 104 patients who had at least
36 months of the radiographic follow-up ([Table 4]). Chen et al[5] in 2019 conducted a retrospective analysis on the effectiveness of endoscopic transpapillary
drainage along with the beneficial long-term results in 31 patients of DPDS. A relatively
small number of adverse outcomes and a failure rate of 13.3% (2/15) were observed,
which highlighted that initial surgery is not mandatory for all DPDS patients.
Table 4
Comparison of treatment strategies with a prior study conducted by Thiruvengadam et
al[18]
|
Treatment strategy
|
Thiruvengadam et al[15]
|
Our study
|
|
Conservative management
|
29 (17.0%)
|
10 (15.87%)
|
|
Percutaneous drainage
|
67 (39.2%)
|
7 (11.11%)
|
|
Therapeutic endoscopic procedures
|
48 (28.1%)
|
40 (63.50%)
|
|
Minimally invasive surgery alone
|
7 (4.1%)
|
1 (1.59%)
|
|
Open surgery
|
20 (11.7%)
|
5 (7.93%)
|
Among the cases included in our study, it was found that endoscopic procedures such
as cystogastrostomy were performed in most of the patients of DPDS with the next preferred
modality being ERCP stenting, both of which led to significant resolution or reduction
of collection along with clinical improvement on follow-up, thus highlighting the
fact that early diagnosis on imaging could improve the overall outcome of DPDS.
Out of 28 patients who underwent cystogastrostomy, 25 showed reduction or resolution
of collection. Only one patient underwent open necrosectomy and four underwent pancreaticojejunostomy
in our study. One patient who underwent video-assisted retroperitoneal drainage developed
postoperative jejunal fistula. Patients who underwent percutaneous drainage (10 out
of 63) of the collections also developed complications or recurrence.
Limitations to this study include its retrospective nature and selection bias which
may have influenced the final overall result. Moreover, the subject of this study
pertains to a niche and sparsely researched aspect of acute necrotizing pancreatitis.
Conclusion
Both CT and MRI features along with assessment of amylase and lipase in the collection
instead of invasive diagnostic procedures like ERCP can aid in the early and accurate
diagnosis of DPDS. Minimally invasive endoscopic procedures such as cystogastrostomy
and stenting are the currently preferred modalities for treatment of DPDS as these
cause lesser complications compared with surgical management.
