Clinical Imaging 38 (2014) 27–30
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
Characteristic CT features of heterotopic pancreas of the mesentery: “another pancreas” in the mesentery Nieun Seo, Jin Hee Kim ⁎ Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138–736, Korea
a r t i c l e
i n f o
Article history: Received 16 July 2013 Accepted 26 September 2013 Keywords: Heterotopic pancreas Mesentery MDCT
a b s t r a c t Purpose: To evaluate computed tomography (CT) findings of heterotopic pancreas of the mesentery (HPM). Methods: Two radiologists reviewed CT scans of seven patients with HPM to determine the location, relationship with the adjacent bowel, presence of a duct-like structure, and the enhancement pattern of HPM in consensus. Results: All HPMs were located in the jejunal mesentery and had morphologic features closely resembling those of the main pancreas and had unique relationship with the jejunum. Duct-like structures were observed in five lesions. The enhancement pattern varied. Conclusion: It is important to be aware of characteristic CT features of HPM to eliminate unnecessary surgeries. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Heterotopic pancreas (HP) is defined as pancreatic tissue in aberrant sites and lacks anatomic and vascular continuity with the main pancreas; its incidence in autopsy series ranged from 0.6% to 14% [1,2]. HP is usually located in the upper gastrointestinal tracts, but it is also rarely seen in other sites including the mesentery, jejunum, ileum, Meckel's diverticulum, bile duct, gallbladder, spleen, umbilicus, and mediastinum [2–13]. HP of the mesentery (HPM) is extremely rare, and only a few cases have been anecdotally reported in the literature [4–8]. To our knowledge, little is known regarding the imaging findings of HPM. We have recently experienced several cases of HPM with characteristic imaging features seen on computed tomography (CT). The purpose of this study was to describe the CT features of HPM.
2. Materials and methods 2.1. Patients This retrospective study was approved by our institutional review board, and informed consent was waived. We performed a search of our radiology database from January 2006 through December 2012 using the search terms, heterotopic or ectopic pancreas and mesentery, and identified nine patients with presumed HPM who had undergone contrast-enhanced CT of the abdomen. No HPM was pathologically confirmed. Two radiologists with 13 and 5 years of clinical experience ⁎ Corresponding author. Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-Gil 86, Songpa-Gu, Seoul 138–736, Korea. E-mail addresses: [email protected], [email protected] (J.H. Kim). 0899-7071/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clinimag.2013.09.008
in abdominal CT interpretation reviewed the CTs of these nine patients in order to verify in consensus the diagnosis of HPM using the following inclusion criteria: (a) the presence of a homogeneous, wellenhancing mass in the mesentery that closely resembled the morphology of the main pancreas, that is, elongated appearance with pancreas-like clefts or lobulations and with or without duct-like structures and (b) the presence of follow-up contrast-enhanced CT scans and constancy in the size and configuration of the mesenteric mass during a follow-up period of at least 2 years. All nine patients met the criteria (a); however, two patients did not meet the criteria (b) and were excluded. Finally, seven (three men, four women; mean age, 50 years; age range, 36–61 years) patients were enrolled in the study. The CT follow-up period for these seven patients ranged from 26 to 77 months (median, 39 months). All seven HPMs were incidentally detected on abdominal CT performed for the evaluation of other diseases, and none of the patients had any symptoms specifically associated with HPM. The clinical data of the study patients are summarized in Table 1. 2.2. Multidetector CT (MDCT) techniques CT examinations were performed on 16- or 64-MDCT scanners (LightSpeed 16 or Optima CT660, GE Healthcare, Milwaukee, WI, USA; Somatom Sensation 16, Siemens Medical Systems, Erlangen, Germany) using dual-phase or single portal-phase scanning. Dualphase scans were obtained during the arterial and portal phase using a 15- to 25-s delay with a bolus-tracking technique and a fixed 72-s delay, respectively, after intravenous injection of 150 ml of iopromide (Ultravist 370; Bayer Schering Pharma, Berlin, Germany) administered at a rate of 3 ml/s using an automatic injector. The section thickness was 3 to 5 mm. In six patients, CT scanning was performed at least once using a dual-phase protocol, whereas in the
28
N. Seo, J.H. Kim / Clinical Imaging 38 (2014) 27–30
Table 1 Clinical data of seven patients with HPM Patient no.
Sex/Age (year)
Reason for CT examination
CT follow-up period (month)
1 2 3 4 5 6 7
F/36 M/60 F/61 F/51 F/57 M/47 M/38
Crohn's disease Hepatocellular carcinoma Liver cirrhosis Breast cancer metastasis Chronic constipation Pancreatic cyst Duodenal GIST
48 35 50 39 29 26 77
MRI, and PET/CT were performed in four, one, and two patients, respectively. None of the four HPMs were detected on the barium small-bowel series. One HPM was barely visible on MRI with only unenhanced T1- and T2-weighted images. Two HPMs appeared isometabolic on PET/CT. Representative cases are presented in Figs. 1 and 2. 4. Discussion
F, female; M, male.
remaining patient, all CT scans were performed using only a single portal-phase protocol. 2.3. Image analysis Two board-certified radiologists reviewed the CT scans and determined in consensus the location of the HPM (jejunal, ileal, or colonic mesentery), the relationship between the HPM and the adjacent bowel (separated or attached), the presence of a duct-like structure along the center of the long axis of the HPM, and the degree of contrast enhancement of the HPM compared with that of the main pancreas and the adjacent bowel wall (hyper-, iso-, or hypoattenuation) on each phase. The maximum diameters of the HPM for both the long axis diameter (LD) and short axis diameter (SD) were measured, and the ratio of the LD to SD (LD/SD ratio) was calculated. The visibility of HPM using other imaging modalities, that is, barium small-bowel series, magnetic resonance imaging (MRI), or positron emission tomography (PET)/CT, if available, was also evaluated. 3. Results The CT findings of HPMs are summarized in Table 2. All of the seven HPMs were located in the jejunal mesentery. Six of them were located in the proximal jejunal mesentery, and the remaining one (Patient 6) was located in the distal jejunal mesentery. The mean LD, SD, and LD/SD ratios of HPMs were 4.4 cm, 1.5 cm, and 3.0, respectively. Duct-like structures were observed in five HPMs. The degree of contrast enhancement of HPM varied from hyper- to hypoattenuation compared with that of the main pancreas and the adjacent jejunal wall, as seen on both the arterial and portal phases. Regarding the relationship between the HPM and the adjacent jejunum, a common pattern was observed in all cases, that is, one side of the HPM, based on its long-axis orientation, was attached to the adjacent jejunal wall, and the opposite side was separated from the jejunum. The jejunal side of the HPM was relatively bulky and tapered toward the mesenteric side. A barium small-bowel series,
Our study is the first to describe the CT findings of HPM in a single series, although there have been a few case reports [4–8]. In our study, all seven HPMs were located in the jejunal mesentery and had several common CT findings that were thought to be characteristic of HPM. First, all HPMs demonstrated the morphologic feature of closely resembling the main pancreas, that is, a homogeneous, wellenhancing mass with an elongated appearance and pancreas-like clefts or lobulations. Second, in terms of the relationship between the HPM and the adjacent jejunum, a common pattern was observed, that is, one side of the HPM, used for its long-axis orientation, was more bulky and was attached to the adjacent jejunal wall, whereas the other side tapered toward the mesenteric side and was separated from the jejunum. Taking into account the distinctive relationship between the HPM and the jejunum, HPM might presumably be a unique form of jejunal HP, which consists of a predominantly exoenteric component and a tiny intramural component. Actually, the presence of pancreatic tissue in the submucosa, muscularis propria, or serosa of the jejunum has been identified by pathology examination in previous HPM reports [4,6,8]. In addition to the aforementioned characteristic morphologic features and the relationship with the jejunum, the presence of a duct running along the center of the long axis of the mass may be another key finding for the imaging diagnosis of HPM and can allow better definition of the mass as an HPM rather than any of the other differential considerations and, consequently, obviate the need for pathology confirmation. In our study, the duct was distinctly seen in five (71.4%) of seven HPMs, which may suggest that contrastenhanced CT with good image quality could be useful for finding the duct within the HPM. Meanwhile, as suggested in previous reports [7,8], magnetic resonance cholangiopancreatography (MRCP) could be used to confirm the presence of the duct in equivocal cases in which the duct is not clearly demonstrated on CT because the ability of MRCP to depict a fine duct is superior to that of CT. There has been some debate with regard to the enhancement pattern of the HP seen on CT, that is, whether it is similar to that of the main pancreas [4,6,7] or variable [10,11,14]. Our study results favor the latter as the enhancement pattern we saw in only one case was similar to that of the main pancreas on both the arterial and portal phases, but otherwise various patterns were observed from hyper- to hypoattenuation compared to the attenuation of the main pancreas.
Table 2 CT findings in seven patients with HPM Patient no.
Location
1 2 3 4 5d 6 7
Jejunum Jejunum Jejunum Jejunum Jejunum Jejunum Jejunum
Size (mm) LDa
SDa
LD/SDa
35 32 53 52 49 36 48
12 16 18 13 15 11 18
2.9 2.0 2.9 4.0 3.3 3.3 2.7
Duct-like structure
Contrast enhancement AP (P)b
PP (P)b
AP (B)c
PP (B)c
Present Absent Absent Present Present Present Present
hyper hypo iso hypo NA hyper hypo
hyper iso iso hypo iso hyper iso
hyper iso iso hypo NA hyper iso
hyper iso iso hypo iso hyper hyper
NA, not available. a LD, SD, and LD/SD indicates the maximum diameter of the HPM for the long and short axes and the ratio of the long to short axis diameter, respectively. b AP (P) and PP (P) indicate the attenuation of HPM compared with that of the main pancreas, as seen on the arterial and portal phases, respectively. c AP (B) and PP (B) indicate the attenuation of HPM compared with that of the adjacent bowel wall, as seen on the arterial and portal phases, respectively. d Patient 5 underwent CT scanning according to only a single portal-phase protocol.
N. Seo, J.H. Kim / Clinical Imaging 38 (2014) 27–30
29
Fig. 1. Thirty-six-year-old woman (Patient 1) with HPM. (A–C) Consecutive, axial arterial-phase CT images show an elongated, well-enhancing mass with lobulations (large arrows) in the proximal jejunal mesentery. One side of the mass is attached to the adjacent jejunum (A), and the other side is separated from the jejunum and tapered toward the mesentery (C). The duct is clearly seen (small arrow in C). (D) A coronal arterial-phase CT image shows that the mass (large arrow) appears hyperattenuated compared to the main pancreas (small arrow). (E) An axial portal-phase CT image obtained 35 months later demonstrates the constancy in the size and configuration of the mass (arrow).
Two radiology–pathology correlation studies showed that the enhancement pattern of HP varied depending on the microscopic composition of the lesion, for example, acini, ducts, or islet cells [10,11]. Therefore, the enhancement pattern seen on CT may be unreliable for differentiating HPM from gastrointestinal stromal tumor (GIST), carcinoid tumor, lymphoma, and metastasis as each of these tumors can manifest as a homogeneous, well-enhancing, softtissue mass located in the mesentery. Instead, the above-mentioned, characteristic morphologic features of HPM and its relationship to the adjacent bowel, as well as the ancillary findings suggesting the presence of a neoplasm such as lymphadenopathy, invasion of the adjacent structures, or metastasis to other organs, may be further helpful for differentiating between HPM and those tumors. The imaging features of HPM in our series definitely differed from those of HP in the stomach, which have been described in previous
studies [9–11], that is, the HPMs were elongated in shape, whereas gastric HPs were mostly round or oval, and thus, the mean LD/SD ratio of HPM was much greater than that of gastric HP (3.0 vs. 1.4–1.5). The maximum diameter of HPM was also greater than that of gastric HP (4.4 cm vs. 1.8–2.7 cm). Lastly, the exoenteric component was predominant, and the intramural component was substantially less in HPM, whereas the intramural component was predominant in gastric HP with a broad base on the gastric wall. The reason why four HPMs were not detected on our barium small-bowel series may be due to the lack of an intramural component. With regard to its clinical aspects, HP is usually asymptomatic, although rare complications, including pancreatitis, gastrointestinal bleeding, obstruction, intussusceptions, and cancer, have been reported [3–8,12–16], and all of the HPM cases reported in the literature presented with such complications [4–8]. However, in our
30
N. Seo, J.H. Kim / Clinical Imaging 38 (2014) 27–30
Fig. 2. Fifty-seven-year-old woman (Patient 5) with HPM. (A–C) Consecutive, coronal portal-phase CT images show an elongated mass (large arrows in A and B) with the duct (small arrow in A) in the proximal jejunal mesentery. The mass has a morphology closely resembling the main pancreas (arrow in C) and tapers toward the right mesenteric side. (D) An axial portal-phase CT image obtained 29 months later shows the unchanged mesenteric mass (arrow).
study, none of the patients had any symptoms or complications associated with HPM. Our study had some limitations. First, it included only a small number of patients due to the rarity of HPM. Second, pathology confirmation was not obtained in any of our study patients. Nonetheless, we believe that the unique morphology of HPMs and their constancy in size and configuration seen during the follow-up period of at least 2 years would be sufficient to exclude other diseases. In conclusion, in our study, HPM manifested as a large, homogeneous, well-enhancing mass that closely resembled the morphology of the main pancreas with the duct often detectable and a varying pattern of contrast enhancement seen on CT. It is, therefore, important to be aware of these characteristic CT features of HPM, namely “another pancreas in the mesentery,” so as to reduce unnecessary surgeries. References [1] Pearson S. Aberrant pancreas. Review of the literature and report of three cases, one of which produced common and pancreatic duct obstruction. AMA Arch Surg 1951;63:168–86. [2] Dolan RV, ReMine WH, Dockerty MB. The fate of heterotopic pancreatic tissue. A study of 212 cases. Arch Surg 1974;109:762–5. [3] Kung JW, Brown A, Kruskal JB, Goldsmith JD, Pedrosa I. Heterotopic pancreas: typical and atypical imaging findings. Clin Radiol 2010;65:403–7.
[4] Shin SS, Jeong YY, Kang HK. Giant heterotopic pancreas in the jejunal mesentery. AJR Am J Roentgenol 2007;189:W262–3. [5] Canbaz H, Colak T, Dusmez Apa D, Sezgin O, Aydin S. An unusual cause of acute abdomen: mesenteric heterotopic pancreatitis causing confusion in clinical diagnosis. Turk J Gastroenterol 2009;20:142–5. [6] Ginsburg M, Ahmed O, Rana KA, Boumendjel R, Dachman AH, Zaritzky M. Ectopic pancreas presenting with pancreatitis and a mesenteric mass. J Pediatr Surg 2013;48:e29–32. [7] Silva AC, Charles JC, Kimery BD, Wood JP, Liu PT. MR cholangiopancreatography in the detection of symptomatic ectopic pancreatitis in the small-bowel mesentery. AJR Am J Roentgenol 2006;187:W195–7. [8] Wong JC, Robinson C, Jones EC, et al. Recurrent ectopic pancreatitis of the jejunum and mesentery over a 30-year period. Hepatobiliary Pancreat Dis Int 2011;10:218–20. [9] Cho JS, Shin KS, Kwon ST, et al. Heterotopic pancreas in the stomach: CT findings. Radiology 2000;217:139–44. [10] Kim JY, Lee JM, Kim KW, et al. Ectopic pancreas: CT findings with emphasis on differentiation from small gastrointestinal stromal tumor and leiomyoma. Radiology 2009;252:92–100. [11] Park SH, Han JK, Choi BI, et al. Heterotopic pancreas of the stomach: CT findings correlated with pathologic findings in six patients. Abdom Imaging 2000;25:119–23. [12] Shin HO, Lee SW, Koo H, Hwang JY. Isolated heterotopic pancreas in ileoileal intussusception. J Ultrasound Med 2009;28:545–8. [13] Sandrasegaran K, Maglinte DD, Cummings OW. Heterotopic pancreas: presentation as jejunal tumor. AJR Am J Roentgenol 2006;187:W607–9. [14] Wall I, Shah T, Tangorra M, Li JJ, Tenner S. Giant heterotopic pancreas presenting with massive upper gastrointestinal bleeding. Dig Dis Sci 2007;52:956–9. [15] Makhlouf HR, Almeida JL, Sobin LH. Carcinoma in jejunal pancreatic heterotopia. Arch Pathol Lab Med 1999;123:707–11. [16] Okuhata Y, Maebayashi T, Furuhashi S, et al. Characteristics of ectopic pancreas in dynamic gadolinium-enhanced MRI. Abdom Imaging 2010;35:85–7.
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
Characteristic CT features of heterotopic pancreas of the mesentery: “another pancreas” in the mesentery Nieun Seo, Jin Hee Kim ⁎ Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138–736, Korea
a r t i c l e
i n f o
Article history: Received 16 July 2013 Accepted 26 September 2013 Keywords: Heterotopic pancreas Mesentery MDCT
a b s t r a c t Purpose: To evaluate computed tomography (CT) findings of heterotopic pancreas of the mesentery (HPM). Methods: Two radiologists reviewed CT scans of seven patients with HPM to determine the location, relationship with the adjacent bowel, presence of a duct-like structure, and the enhancement pattern of HPM in consensus. Results: All HPMs were located in the jejunal mesentery and had morphologic features closely resembling those of the main pancreas and had unique relationship with the jejunum. Duct-like structures were observed in five lesions. The enhancement pattern varied. Conclusion: It is important to be aware of characteristic CT features of HPM to eliminate unnecessary surgeries. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Heterotopic pancreas (HP) is defined as pancreatic tissue in aberrant sites and lacks anatomic and vascular continuity with the main pancreas; its incidence in autopsy series ranged from 0.6% to 14% [1,2]. HP is usually located in the upper gastrointestinal tracts, but it is also rarely seen in other sites including the mesentery, jejunum, ileum, Meckel's diverticulum, bile duct, gallbladder, spleen, umbilicus, and mediastinum [2–13]. HP of the mesentery (HPM) is extremely rare, and only a few cases have been anecdotally reported in the literature [4–8]. To our knowledge, little is known regarding the imaging findings of HPM. We have recently experienced several cases of HPM with characteristic imaging features seen on computed tomography (CT). The purpose of this study was to describe the CT features of HPM.
2. Materials and methods 2.1. Patients This retrospective study was approved by our institutional review board, and informed consent was waived. We performed a search of our radiology database from January 2006 through December 2012 using the search terms, heterotopic or ectopic pancreas and mesentery, and identified nine patients with presumed HPM who had undergone contrast-enhanced CT of the abdomen. No HPM was pathologically confirmed. Two radiologists with 13 and 5 years of clinical experience ⁎ Corresponding author. Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-Gil 86, Songpa-Gu, Seoul 138–736, Korea. E-mail addresses: [email protected], [email protected] (J.H. Kim). 0899-7071/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clinimag.2013.09.008
in abdominal CT interpretation reviewed the CTs of these nine patients in order to verify in consensus the diagnosis of HPM using the following inclusion criteria: (a) the presence of a homogeneous, wellenhancing mass in the mesentery that closely resembled the morphology of the main pancreas, that is, elongated appearance with pancreas-like clefts or lobulations and with or without duct-like structures and (b) the presence of follow-up contrast-enhanced CT scans and constancy in the size and configuration of the mesenteric mass during a follow-up period of at least 2 years. All nine patients met the criteria (a); however, two patients did not meet the criteria (b) and were excluded. Finally, seven (three men, four women; mean age, 50 years; age range, 36–61 years) patients were enrolled in the study. The CT follow-up period for these seven patients ranged from 26 to 77 months (median, 39 months). All seven HPMs were incidentally detected on abdominal CT performed for the evaluation of other diseases, and none of the patients had any symptoms specifically associated with HPM. The clinical data of the study patients are summarized in Table 1. 2.2. Multidetector CT (MDCT) techniques CT examinations were performed on 16- or 64-MDCT scanners (LightSpeed 16 or Optima CT660, GE Healthcare, Milwaukee, WI, USA; Somatom Sensation 16, Siemens Medical Systems, Erlangen, Germany) using dual-phase or single portal-phase scanning. Dualphase scans were obtained during the arterial and portal phase using a 15- to 25-s delay with a bolus-tracking technique and a fixed 72-s delay, respectively, after intravenous injection of 150 ml of iopromide (Ultravist 370; Bayer Schering Pharma, Berlin, Germany) administered at a rate of 3 ml/s using an automatic injector. The section thickness was 3 to 5 mm. In six patients, CT scanning was performed at least once using a dual-phase protocol, whereas in the
28
N. Seo, J.H. Kim / Clinical Imaging 38 (2014) 27–30
Table 1 Clinical data of seven patients with HPM Patient no.
Sex/Age (year)
Reason for CT examination
CT follow-up period (month)
1 2 3 4 5 6 7
F/36 M/60 F/61 F/51 F/57 M/47 M/38
Crohn's disease Hepatocellular carcinoma Liver cirrhosis Breast cancer metastasis Chronic constipation Pancreatic cyst Duodenal GIST
48 35 50 39 29 26 77
MRI, and PET/CT were performed in four, one, and two patients, respectively. None of the four HPMs were detected on the barium small-bowel series. One HPM was barely visible on MRI with only unenhanced T1- and T2-weighted images. Two HPMs appeared isometabolic on PET/CT. Representative cases are presented in Figs. 1 and 2. 4. Discussion
F, female; M, male.
remaining patient, all CT scans were performed using only a single portal-phase protocol. 2.3. Image analysis Two board-certified radiologists reviewed the CT scans and determined in consensus the location of the HPM (jejunal, ileal, or colonic mesentery), the relationship between the HPM and the adjacent bowel (separated or attached), the presence of a duct-like structure along the center of the long axis of the HPM, and the degree of contrast enhancement of the HPM compared with that of the main pancreas and the adjacent bowel wall (hyper-, iso-, or hypoattenuation) on each phase. The maximum diameters of the HPM for both the long axis diameter (LD) and short axis diameter (SD) were measured, and the ratio of the LD to SD (LD/SD ratio) was calculated. The visibility of HPM using other imaging modalities, that is, barium small-bowel series, magnetic resonance imaging (MRI), or positron emission tomography (PET)/CT, if available, was also evaluated. 3. Results The CT findings of HPMs are summarized in Table 2. All of the seven HPMs were located in the jejunal mesentery. Six of them were located in the proximal jejunal mesentery, and the remaining one (Patient 6) was located in the distal jejunal mesentery. The mean LD, SD, and LD/SD ratios of HPMs were 4.4 cm, 1.5 cm, and 3.0, respectively. Duct-like structures were observed in five HPMs. The degree of contrast enhancement of HPM varied from hyper- to hypoattenuation compared with that of the main pancreas and the adjacent jejunal wall, as seen on both the arterial and portal phases. Regarding the relationship between the HPM and the adjacent jejunum, a common pattern was observed in all cases, that is, one side of the HPM, based on its long-axis orientation, was attached to the adjacent jejunal wall, and the opposite side was separated from the jejunum. The jejunal side of the HPM was relatively bulky and tapered toward the mesenteric side. A barium small-bowel series,
Our study is the first to describe the CT findings of HPM in a single series, although there have been a few case reports [4–8]. In our study, all seven HPMs were located in the jejunal mesentery and had several common CT findings that were thought to be characteristic of HPM. First, all HPMs demonstrated the morphologic feature of closely resembling the main pancreas, that is, a homogeneous, wellenhancing mass with an elongated appearance and pancreas-like clefts or lobulations. Second, in terms of the relationship between the HPM and the adjacent jejunum, a common pattern was observed, that is, one side of the HPM, used for its long-axis orientation, was more bulky and was attached to the adjacent jejunal wall, whereas the other side tapered toward the mesenteric side and was separated from the jejunum. Taking into account the distinctive relationship between the HPM and the jejunum, HPM might presumably be a unique form of jejunal HP, which consists of a predominantly exoenteric component and a tiny intramural component. Actually, the presence of pancreatic tissue in the submucosa, muscularis propria, or serosa of the jejunum has been identified by pathology examination in previous HPM reports [4,6,8]. In addition to the aforementioned characteristic morphologic features and the relationship with the jejunum, the presence of a duct running along the center of the long axis of the mass may be another key finding for the imaging diagnosis of HPM and can allow better definition of the mass as an HPM rather than any of the other differential considerations and, consequently, obviate the need for pathology confirmation. In our study, the duct was distinctly seen in five (71.4%) of seven HPMs, which may suggest that contrastenhanced CT with good image quality could be useful for finding the duct within the HPM. Meanwhile, as suggested in previous reports [7,8], magnetic resonance cholangiopancreatography (MRCP) could be used to confirm the presence of the duct in equivocal cases in which the duct is not clearly demonstrated on CT because the ability of MRCP to depict a fine duct is superior to that of CT. There has been some debate with regard to the enhancement pattern of the HP seen on CT, that is, whether it is similar to that of the main pancreas [4,6,7] or variable [10,11,14]. Our study results favor the latter as the enhancement pattern we saw in only one case was similar to that of the main pancreas on both the arterial and portal phases, but otherwise various patterns were observed from hyper- to hypoattenuation compared to the attenuation of the main pancreas.
Table 2 CT findings in seven patients with HPM Patient no.
Location
1 2 3 4 5d 6 7
Jejunum Jejunum Jejunum Jejunum Jejunum Jejunum Jejunum
Size (mm) LDa
SDa
LD/SDa
35 32 53 52 49 36 48
12 16 18 13 15 11 18
2.9 2.0 2.9 4.0 3.3 3.3 2.7
Duct-like structure
Contrast enhancement AP (P)b
PP (P)b
AP (B)c
PP (B)c
Present Absent Absent Present Present Present Present
hyper hypo iso hypo NA hyper hypo
hyper iso iso hypo iso hyper iso
hyper iso iso hypo NA hyper iso
hyper iso iso hypo iso hyper hyper
NA, not available. a LD, SD, and LD/SD indicates the maximum diameter of the HPM for the long and short axes and the ratio of the long to short axis diameter, respectively. b AP (P) and PP (P) indicate the attenuation of HPM compared with that of the main pancreas, as seen on the arterial and portal phases, respectively. c AP (B) and PP (B) indicate the attenuation of HPM compared with that of the adjacent bowel wall, as seen on the arterial and portal phases, respectively. d Patient 5 underwent CT scanning according to only a single portal-phase protocol.
N. Seo, J.H. Kim / Clinical Imaging 38 (2014) 27–30
29
Fig. 1. Thirty-six-year-old woman (Patient 1) with HPM. (A–C) Consecutive, axial arterial-phase CT images show an elongated, well-enhancing mass with lobulations (large arrows) in the proximal jejunal mesentery. One side of the mass is attached to the adjacent jejunum (A), and the other side is separated from the jejunum and tapered toward the mesentery (C). The duct is clearly seen (small arrow in C). (D) A coronal arterial-phase CT image shows that the mass (large arrow) appears hyperattenuated compared to the main pancreas (small arrow). (E) An axial portal-phase CT image obtained 35 months later demonstrates the constancy in the size and configuration of the mass (arrow).
Two radiology–pathology correlation studies showed that the enhancement pattern of HP varied depending on the microscopic composition of the lesion, for example, acini, ducts, or islet cells [10,11]. Therefore, the enhancement pattern seen on CT may be unreliable for differentiating HPM from gastrointestinal stromal tumor (GIST), carcinoid tumor, lymphoma, and metastasis as each of these tumors can manifest as a homogeneous, well-enhancing, softtissue mass located in the mesentery. Instead, the above-mentioned, characteristic morphologic features of HPM and its relationship to the adjacent bowel, as well as the ancillary findings suggesting the presence of a neoplasm such as lymphadenopathy, invasion of the adjacent structures, or metastasis to other organs, may be further helpful for differentiating between HPM and those tumors. The imaging features of HPM in our series definitely differed from those of HP in the stomach, which have been described in previous
studies [9–11], that is, the HPMs were elongated in shape, whereas gastric HPs were mostly round or oval, and thus, the mean LD/SD ratio of HPM was much greater than that of gastric HP (3.0 vs. 1.4–1.5). The maximum diameter of HPM was also greater than that of gastric HP (4.4 cm vs. 1.8–2.7 cm). Lastly, the exoenteric component was predominant, and the intramural component was substantially less in HPM, whereas the intramural component was predominant in gastric HP with a broad base on the gastric wall. The reason why four HPMs were not detected on our barium small-bowel series may be due to the lack of an intramural component. With regard to its clinical aspects, HP is usually asymptomatic, although rare complications, including pancreatitis, gastrointestinal bleeding, obstruction, intussusceptions, and cancer, have been reported [3–8,12–16], and all of the HPM cases reported in the literature presented with such complications [4–8]. However, in our
30
N. Seo, J.H. Kim / Clinical Imaging 38 (2014) 27–30
Fig. 2. Fifty-seven-year-old woman (Patient 5) with HPM. (A–C) Consecutive, coronal portal-phase CT images show an elongated mass (large arrows in A and B) with the duct (small arrow in A) in the proximal jejunal mesentery. The mass has a morphology closely resembling the main pancreas (arrow in C) and tapers toward the right mesenteric side. (D) An axial portal-phase CT image obtained 29 months later shows the unchanged mesenteric mass (arrow).
study, none of the patients had any symptoms or complications associated with HPM. Our study had some limitations. First, it included only a small number of patients due to the rarity of HPM. Second, pathology confirmation was not obtained in any of our study patients. Nonetheless, we believe that the unique morphology of HPMs and their constancy in size and configuration seen during the follow-up period of at least 2 years would be sufficient to exclude other diseases. In conclusion, in our study, HPM manifested as a large, homogeneous, well-enhancing mass that closely resembled the morphology of the main pancreas with the duct often detectable and a varying pattern of contrast enhancement seen on CT. It is, therefore, important to be aware of these characteristic CT features of HPM, namely “another pancreas in the mesentery,” so as to reduce unnecessary surgeries. References [1] Pearson S. Aberrant pancreas. Review of the literature and report of three cases, one of which produced common and pancreatic duct obstruction. AMA Arch Surg 1951;63:168–86. [2] Dolan RV, ReMine WH, Dockerty MB. The fate of heterotopic pancreatic tissue. A study of 212 cases. Arch Surg 1974;109:762–5. [3] Kung JW, Brown A, Kruskal JB, Goldsmith JD, Pedrosa I. Heterotopic pancreas: typical and atypical imaging findings. Clin Radiol 2010;65:403–7.
[4] Shin SS, Jeong YY, Kang HK. Giant heterotopic pancreas in the jejunal mesentery. AJR Am J Roentgenol 2007;189:W262–3. [5] Canbaz H, Colak T, Dusmez Apa D, Sezgin O, Aydin S. An unusual cause of acute abdomen: mesenteric heterotopic pancreatitis causing confusion in clinical diagnosis. Turk J Gastroenterol 2009;20:142–5. [6] Ginsburg M, Ahmed O, Rana KA, Boumendjel R, Dachman AH, Zaritzky M. Ectopic pancreas presenting with pancreatitis and a mesenteric mass. J Pediatr Surg 2013;48:e29–32. [7] Silva AC, Charles JC, Kimery BD, Wood JP, Liu PT. MR cholangiopancreatography in the detection of symptomatic ectopic pancreatitis in the small-bowel mesentery. AJR Am J Roentgenol 2006;187:W195–7. [8] Wong JC, Robinson C, Jones EC, et al. Recurrent ectopic pancreatitis of the jejunum and mesentery over a 30-year period. Hepatobiliary Pancreat Dis Int 2011;10:218–20. [9] Cho JS, Shin KS, Kwon ST, et al. Heterotopic pancreas in the stomach: CT findings. Radiology 2000;217:139–44. [10] Kim JY, Lee JM, Kim KW, et al. Ectopic pancreas: CT findings with emphasis on differentiation from small gastrointestinal stromal tumor and leiomyoma. Radiology 2009;252:92–100. [11] Park SH, Han JK, Choi BI, et al. Heterotopic pancreas of the stomach: CT findings correlated with pathologic findings in six patients. Abdom Imaging 2000;25:119–23. [12] Shin HO, Lee SW, Koo H, Hwang JY. Isolated heterotopic pancreas in ileoileal intussusception. J Ultrasound Med 2009;28:545–8. [13] Sandrasegaran K, Maglinte DD, Cummings OW. Heterotopic pancreas: presentation as jejunal tumor. AJR Am J Roentgenol 2006;187:W607–9. [14] Wall I, Shah T, Tangorra M, Li JJ, Tenner S. Giant heterotopic pancreas presenting with massive upper gastrointestinal bleeding. Dig Dis Sci 2007;52:956–9. [15] Makhlouf HR, Almeida JL, Sobin LH. Carcinoma in jejunal pancreatic heterotopia. Arch Pathol Lab Med 1999;123:707–11. [16] Okuhata Y, Maebayashi T, Furuhashi S, et al. Characteristics of ectopic pancreas in dynamic gadolinium-enhanced MRI. Abdom Imaging 2010;35:85–7.
