Pancreatitis can be fatal and remains a serious disease. It occurs in two forms as acute and chronic with different clinic, morphological and histological features.1 Chronic pancreatitis is characterized by progressive inflammation, fibrosis of pancreas leading to irreversible structural changes.1 Excessive alcohol consumption, cigarette smoking, autoimmunity, high protein diet, heredity factor and also several morphological anomalies of the pancreaticobiliary ductal system like abnormal pancreaticobiliary junction and
Normal variants and congenital anomalies of the pancreas and the pancreatic duct may not be detected in asymptomatic patients until maturity and even when they are detected, it is often incidental.4, 5 The variations and anomalies of the pancreatic and the biliary ductal system are commonly experienced during radiologic examinations.6 Endoscopic retrograde cholangiopancreatography (ERCP) is considered as the gold standard for the evaluation of pancreatic ductal system and chronic pancreatitis because of its superior spatial resolution and its ability to show main duct and side branch abnormalities with severity assessed using the Cambridge classification. The Cambridge classification divides chronic pancreatitis to five severity groups according to morphologic changes of the main pancreatic duct and its side branches from normal or equivocal to mild, moderate, severe.7 Magnetic resonance cholangiopancreatography (MRCP) is becoming more commonly used in the noninvasive evaluation of the pancreatic and the biliary ducts.1–8 MRCP detects pancreatic ductal system and also these variations with similar accuracy as the invasive technique of endoscopic retrograde cholangiopancreatography (ERCP).3, 9 In MRCP, heavily T2 weighted sequences are used to image fluid filled structures without using contrast agent. MRCP has certain advantages over ERCP, it is safer (no exposure to ionizing radiation, no using contrast agent, no premedication), it can be used for staging malignancy and it does not carry the risk of developing complications, can be applied during acute attacks of pancreatitis and cholangitis, gives the chance to view the extraductal structures by using the conventional T1–T2-weighted images.10 Also, the Cambridge classification has been modified for the MRCP technique.11–13 The using of MRCP in adult patients with persistent and unexplained signs and symptoms such as abdominal pain, nausea and vomiting resulting from chronic pancreatitis or gastric outlet obstruction gives an option to look for a developmental anomaly of pancreas and pancreatic duct. It is important to recognize of these anomalies because they may be a surgically correcTable cause of recurrent pancreatitis or the cause of gastric outlet obstruction. Awareness of these anomalies may provide useful information in surgical planning and prevent of inadvertent ductal injury.
We retrospectively reviewed MRCPs obtained at our radiology department between January 1, 2013 and August 30, 2015 after obtaining the approval of the ethical board. A total of 1312 cases were examined, 154 cases with less than optimal results due to imaging limitations, failure to visualize the main pancreatic duct and with a history of surgery on pancreas, were excluded from the study. A total of 1158 cases were included in the study. The study was performed according the Helsinki Declaration and the Institutional Review Board Committee was approved it.
We performed the MRI examinations of the patients in our radiology department using a 1.5 T MR device (Philips Achiva, Philips Medical System, the Netherlands). Patients were informed about the MRCP imaging and following a 6-hour fasting period and after any metal items or objects on the patients which may produce artifacts were removed. Oral or intravenous contrast material was not used during the investigations. But in some cases, we also performed abdominal MRI with intravenous contrast material at the time of MRCP or sometimes after MRCP when we found some lesions which need additional information.
In all patients, MR examinations were made including coronal and axial T2-weighted turbo spin echo (TSE) images (repetition time [TR]: 962 ms, echo time [TE]:100 ms, Matrix: 256 x 256, number of slice: 24, slice thickness: 6 mm, field of view [FOV]: 350–400 mm, SENSE factor: 4, number of signal acquired [NSA]: 2), coronal and axial gradient-recalled echo (GRE) balanced turbo field echo (TFE) images (TR: 4 ms, TE: 1.24 ms, Matrix: 156 × 213, number of slice: 24, slice thickness: 7 mm, FOV: 300–400 mm, Flip angle: 80, NSA: 2). The choledochus was located in the images in the axial-coronal plane, then respiratory-triggered high-resolution with SENSE 3D-TSE T2-weighted (TR: 1466 ms, TE: 650 ms, echo train length [ETL]: 128, matrix: 256 × 256, NSA: 1, slice thickness: 0.8 mm, FOV: 250–300 mm); para-coronal MRCP source and maximum intensity projection (MIP) reformatted images were obtained. MRCP is performed with heavily T2-weighted sequences with a torso phased-array coil (Table 1).
MRI sequence parameters
TR | TE | MATRIX | N OF SLICE | SLICE THICKNESS | FOV | NSA | TSE-TFE FACTOR | SLAB THICK | |
---|---|---|---|---|---|---|---|---|---|
962ms | 100 ms | 256x256 | 24 | 6 mm | 350-400 mm | 2 | 158 | - | |
4 ms | 1.24 ms | 156x213 | 24 | 7 mm | 300-400 mm | 2 | 219 | - | |
1466 ms | 650 ms | 256x256 | 1 | 0.8 mm | 250-300 mm | 1 | 105 | 40 mm |
Ax = axial; ETL = echo train length; GRE = gradient-recalled echo; N = number; NSA = number of signal acquired; TE = echo time; TFE = turbo field echo; TR = repetition time; TSE = turbo spin echo; W = weighted
Two radiologists with experience in abdominal imaging of 15 years (Z.H.A.) and 1 year (M.A.) reviewed the MRCP images retrieved from Picture Archiving and Communication System (PACS) of our hospital. Discordant interpretations were subsequently resolved by consensus of the 2 radiologists.
The course of the pancreatic duct was evaluated as descending (Figure 1), sigmoid (Figure 2), vertical (Figure 3), and loop (Figure 4) shaped courses.5, 14
The ductal configuration was evaluated as Type 1–Type 5 (Figure 5). At Type 1, there was a bifid configuration with dominant duct of Wirsung, at Type 2, there was a dominant duct of Santorini Type 5, where the duct of Santorini formed an inferior loop and connected with a side branch of the duct of Wirsung in the
Three variants of
Anomalous pancreaticobiliary ductal junction was described the abnormal junction of the common biliary duct (CBD) and the pancreatic duct outside the duodenal wall forming a long common channel (> 15 mm).5, 6
We used the Cambridge classification system which has been modified for the MRCP technique: Cambridge 1 (normal pancreas): pancreatic ducts are normal; Cambridge 2 (
Fisher’s exact test and χ square test were used as statistical methods in the study. When samples were small and the assumptions for the χ square were violated, the Fisher’s exact test was used. For example, in a 2 x 2 Table when expected cell counts were less than 5, or any were less than 1 even, Yates correction does not work and Fisher exact test was used without
We retrospectively evaluated the results of 1312 patients who underwent MRCP at our radiology department prior to liver resection surgery or due to suspicion of pancreatobiliary disease. One-hundred fifty four cases were excluded from the study for low MRCP image quality, pancreatic head mass making it impossible to analyze the ductal system, and with history of pancreatic surgery. Finally 1158 patients were included in the study, 668 were female (57.69%) and 490 were male (42.31%). The mean age was 60.8
When we evaluated the course of pancreatic duct, descending type was the most commonly observed (62.5%), and the second most common course type was sigmoid type (30%). The distribution of the pancreatic course types was summarized in Table 2.
Number of variations n (%) | Male n (%) | Female n (%) | |
---|---|---|---|
Descending type | 724 (62.5) | 321 (65.5) | 403 (60) |
Sigmoid type | 343 (30) | 134 (27.5) | 199 (30) |
Vertical type | 68 (5.5) | 17 (5.4) | 51 (7.8) |
Loop type | 23 (2) | 8 (1.6) | 15 (2.2) |
The most commonly observed pancreatic duct configuration was Type 3 in 528 patients (45.6%) where 521 patients (45%) had Type 1 configuration. The distribution of the ductal configuration of pancreas is shown in Table 3.
The distribution of ductal configuration types of main pancreatic duct
Variation in configuration | Number of Variations, n (%) | Male, n (%) | Female, n (%) |
---|---|---|---|
Type 1 | 521 (45) | 233 (47.5) | 288 (43.1) |
Type 2 | 42 (3.6) | 11 (2.3) | 31 (4.6) |
Type 3 | 528 (45.6) | 220 (44.9) | 308 (46.1) |
Type 4 | 54 (4.6) | 19 (3.9) | 35 (5.3) |
Type 5 | 13 (1.2) | 7 (1.4) | 6 (0.9) |
Type 1 = a bifid configuration with a dominant duct of Wirsung; Type 2 = a bifid configuration with dominant duct of Santorini without
The distribution of
Number of variations | Male, n (%) | Female, n (%) | |
---|---|---|---|
24 (44.4) | 8 (40) | 16 (47) | |
20 (37) | 7 (35) | 13 (38.2) | |
10 (18.6) | 5 (25) | 5 (14.8) | |
There were only two female patients (0.17%) who had pancreatobiliary junction anomaly.
The relationship between Cambridge types and the distribution of the course types, ductal configuration types of main pancreatic duct,
The relationship between Cambridge classification and the distribution of the course types, ductal configuration types of main pancreatic duct,
Cambridge 1; n - (%) | Cambridge 2 and 3; n - (%) | Cambridge 4; n - (%) | Cambridge 5; n - (%) | TOTAL n - (%) | |
---|---|---|---|---|---|
Descending type | 612 (85) | 82 (11) | 25 (3) | 5 (1) | 724 (62.5) |
Sigmoid type | 292 (85) | 34 (10) | 13 (4) | 4 (1) | 343 (30) |
Vertical type | 57 (84) | 7 (10) | 3 (4) | 1 (2) | 68 (5.5) |
Loop type | 17 (74) | 4 (17) | 2 (9) | 0 (0) | 23 (2) |
Type 1 | 445 (85) | 54(10) | 18 (4) | 4 (1) | 521 (45) |
Type 2 | 34 (81) | 6 (14) | 2 (5) | 0 (0) | 42 (3.6) |
Type 3 | 447 (84) | 57 (11) | 19 (4) | 5 (1) | 528 (45.6) |
Type 4 | 44 (81) | 8 (15) | 2 (4) | 0 (0) | 54 (4.6) |
Type 5 | 8 (62) | 2 (15) | 2 (15) | 1 (8) | 13 (1.2) |
PD subtype 1 | 19 (79) | 4 (17) | 1 (4) | 0 (0) | 24 (44.4) |
PD subtype 2 | 16 (80) | 3 (15) | 1 (5) | 0 (0) | 20 (37) |
PD. subtype 3 | 9 (90) | 1 (10) | 0 (0) | 0 (0) | 10 (18.6) |
PD =
Besides the anatomical variations of pancreatic duct, we did not observe any
The pancreas and the pancreatic ductal embryology is moderately complicated, a number of congenital ductal variations have been described such as complete or incomplete
Our study has the largest sample size in the literature to the best of our knowledge, was to evaluate the frequency of anatomic variations of pancreatic duct by using MRCP during a certain time interval. When we evaluated the course of pancreatic ducts of our study population, descending type was the most common type (62.59%) where sigmoid type was the second one as seen in Table 2. In literature, the course of the pancreatic duct varies greatly and the most common one is a descending course with 50%.5, 14 Itoh
In our study, the most commonly observed pancreatic duct configuration was Type 3 in 528 patients (45.6%) where 521 patients (45%) had Type 1 configuration. These two Wirsung dominant configurations had a rate of 90.6% totally. In literature, the bifid configuration with dominant duct of Wirsung drainage is most common (60%), a rudimentary, non-draining duct of Santorini (30%), or dominant duct of Santorini without
Anomalous pancreaticobiliary ductal junction was found in 2 female patients (0.17%). In this condition, pancreatobiliary reflux occurs into the ducts because of the failure of the sphincter of Oddi.18 In literature, complications or associated conditions with anomalous pancreaticobiliary ductal junction are cholodochal cyst, recurrent cholangitis, bile duct, choledocholithiasis, gallbladder cancer and peritonitis caused by spontaneous perforation.18 Our two patients had solo anomalous pancreaticobiliary ductal junction, they did not have its complications or associated conditions. We follow up these patients.
During embryonic development,
In our study population, female to male ratio was 1.36. When we consider pancreatic duct anatomic variations, we found that female-to-male ratios of Type 2 (p = 0.03) configuration and vertical course (p = 0.0048) of pancreatic duct were statistically significant. The gender distributions between the other types of configurations of the pancreatic duct were not statistically significant (for Type 1, p = 0.35; for Type 3, p = 0.80; for Type 4, p = 0.29; for Type 5, p = 0.40) (Table 3). And also there were not statistically significant differences between the gender for the descending (p = 0.38), loop (p = 0.46) and sigmoid (p = 0.49) course of the pancreatic duct (Table 2). When we analyzed the distributions of subtypes of
It has been shown that MRCP has been sensitive and specific (85%–100 % for 1.5 Tesla systems) for evaluating pancreatic ductal system.1, 9, 16 The ductal changes of main pancreatic duct are demonstrated on MRCP, however subtle side branch changes can be missed.1 One of the major limitation of MRCP is the lack of functional information and inability to image the ductal system in distended condition. According to the previous MRCP-based studies, ductal alterations suggesting chronic pancreatitis were reported in approximately 16%.23 Our study was concordant with the literature; we could only demonstrate dilated side branches of main pancreatic duct in approximately 15% of the cases (Table 5). This can be overcome by using secretin which is known as secretin stimulated MRCP (s-MRCP). Secretin injection during MRCP enhances the morphology of the main pancreatic duct and side branches and provides information on pancreatic outflow dynamics at the same time.23–25 Secretin is a safe drug and can be administered without any serious side effect. In normal pancreas, the side branches are not visualized after secretin but in patient with early chronic pancreatitis the side branches can show dilatation which is not seen on conventional MRCP.1, 23–25 Thus s-MRCP has the capability to provide both the structural and functional information.
In our study population, dilatation of pancreatic side branches as a chronic pancreatitis feature was observed in 15% of the patients (Table 5) and 85% of the patients had normal caliber of main pancreatic duct and side branches. When we evaluated the distributions of Cambridge classification between course types and configuration types of the pancreatic duct, only Type 5 configuration (which was
There are some limitations of our study. One of them is that we do not have a reference standard such as ERCP or surgery because of ethical issues. Second is the retrospective nature of the study. And third limitation is that most of our patients underwent MRCP at our radiology department with suspected biliary or pancreatic disease, because of that our study population may not sample the whole population.
In conclusion, the results of our study indicated that variants of