Annular pancreas: a review of its molecular embryology, genetic basis and clinical considerations

Antenatal Diagnosis of Complete Annular Pancreas With Postnatal Surgical Follow-Up: A Case Report

Annular pancreas is a rare congenital disorder, which is characterized by partial or complete pancreatic tissue surrounding the second part of the duodenum. It can be diagnosed antenatally on ultrasound. We are reporting a case where a double bubble sign on an antenatal scan was seen, which was followed up after the delivery of the baby, and radiography also confirmed the findings. Both investigations suggested duodenal obstruction (duodenal atresia and annular pancreas were kept as possible causes). The child was taken for surgery and pancreatic tissue surrounding the second part of the duodenum was seen, confirming the diagnosis of annular pancreas.

Exploring the clinical characteristics and prevalence of the annular pancreas: a meta-analysis

BACKGROUND

The annular pancreas (AP) is a rare gastrointestinal congenital malformation, in which malrotation of the pancreatic ventral bud in the seventh week of embryonic development manifests in a partial or complete ring of tissue around the second part of the duodenum.

METHODS

The main online medical databases such as PubMed, ScienceDirect, Wiley online library, Web of Science, and EBSCO discovery service were used to gather all relevant studies on the AP.

RESULTS

A total of 12,729,118 patients were analyzed in relation to the prevalence of AP. The pooled prevalence of AP was 0.0045% (95% CI: 0.0021%-0.0077%). The most frequent comorbidity in adults and children was duodenal obstruction, with a pooled prevalence of 24.04% and 52.58%, respectively (95% CI: 6.86%-46.48% and 35.56%-69.31%, respectively). The most frequent operation in adult patients with AP was duodenojejunostomy, with pooled prevalence established at 3.62% (95% CI: 0.00%-10.74%).

CONCLUSION

The diagnostic complexity of AP is accentuated by its nonspecific clinical symptoms, making accurate identification reliant on imaging studies. Therefore, having a thorough knowledge of the clinical characteristics of the AP and its associated anomalies becomes paramount when faced with this rare congenital condition.

The role of noncoding RNAs in pancreatic birth defects

Congenital defects in the pancreas can cause severe health issues such as pancreatic cancer and diabetes which require lifelong treatment. Regenerating healthy pancreatic cells to replace malfunctioning cells has been considered a promising cure for pancreatic diseases including birth defects. However, such therapies are currently unavailable in the clinic. The developmental gene regulatory network underlying pancreatic development must be reactivated for in vivo regeneration and recapitulated in vitro for cell replacement therapy. Thus, understanding the mechanisms driving pancreatic development will pave the way for regenerative therapies. Pancreatic progenitor cells are the precursors of all pancreatic cells which use epigenetic changes to control gene expression during differentiation to generate all of the distinct pancreatic cell types. Epigenetic changes involving DNA methylation and histone modifications can be controlled by noncoding RNAs (ncRNAs). Indeed, increasing evidence suggests that ncRNAs are indispensable for proper organogenesis. Here, we summarize recent insight into the role of ncRNAs in the epigenetic regulation of pancreatic development. We further discuss how disruptions in ncRNA biogenesis and expression lead to developmental defects and diseases. This review summarizes in vivo data from animal models and in vitro studies using stem cell differentiation as a model for pancreatic development.

Exome sequencing findings in children with annular pancreas

BACKGROUND

Annular pancreas (AP) is a congenital defect of unknown cause in which the pancreas encircles the duodenum. Theories include abnormal migration and rotation of the ventral bud, persistence of ectopic pancreatic tissue, and inappropriate fusion of the ventral and dorsal buds before rotation. The few reported familial cases suggest a genetic contribution.

METHODS

We conducted exome sequencing in 115 affected infants from the California birth defects registry.

RESULTS

Seven cases had a single heterozygous missense variant in IQGAP1, five of them with CADD scores >20; seven other infants had a single heterozygous missense variant in NRCAM, five of them with CADD scores >20. We also looked at genes previously associated with AP and found two rare heterozygous missense variants, one each in PDX1 and FOXF1.

CONCLUSION

IQGAP1 and NRCAM are crucial in cell polarization and migration. Mutations result in decreased motility which could possibly cause the ventral bud to not migrate normally. To our knowledge, this is the first study reporting a possible association for IQGAP1 and NRCAM with AP. Our findings of rare genetic variants involved in cell migration in 15% of our population raise the possibility that AP may be related to abnormal cell migration.

Annular pancreas: Beneath the intestinal obstruction-A case report

Annular pancreas is an uncommon congenital anomaly which is a rare cause of congenital duodenal obstruction. It is normally identified during the neonatal period, but may also be identified in adolescence or adulthood. This diagnosis is often overlooked in adult patients who present with symptoms suggestive of duodenal obstruction. We present a case of AP detected in a 23-year-old man, with complaints of continuous vomiting and abdominal discomfort over the last 6 months. An upper gastrointestinal study revealed a constricted second part of the duodenum. A computed tomography scan revealed a complete ring of pancreatic tissue around the second part of the duodenum. Diagnostic and therapeutic surgery decompresses the external obstruction. The patient had an early post-operative activation. No specific guidelines and protocols exist about the management of such cases. Given the rarity of this congenital anomaly, presenting with chronic partial duodenal obstruction, and its successful surgical treatment, have prompted us to report the case along with a brief review of literature about the subject.

The Epidemiology of Annular Pancreas in the United States: A Population-based Study

BACKGROUND AND AIMS

Annular pancreas is a rare congenital condition where the second part of the duodenum is encircled by pancreatic tissue. There is a scarcity of data on its natural history therefore, we aimed to evaluate the epidemiology of annular pancreas and identify underlying associations using a large database.

METHODS

A multi-institutional database (Explorys) was surveyed. A cohort of patients with a Systematized Nomenclature of Medicine-Clinical Terms diagnosis of "MRI, CT, EUS and/or ERCP" between April 2015 and April 2020 was identified. Subsequently a cohort of patients with history of "annular pancreas" was identified.

RESULTS

There were a total of 40,075,980 individuals in the database with 6,162,600 (15.38%) who had an magnetic resonance imaging, computed tomography, endoscopic retrograde cholangiopancreatography, and/or endoscopic ultrasound. There were 210 (3.4/100,000) had a diagnosis of annular pancreas. When compared with the control group, patients with annular pancreas were more likely to have a history of alcohol use, smoking, acute pancreatitis, chronic pancreatitis, gastritis, duodenitis, jaundice, and gastrointestinal outlet obstruction.

CONCLUSIONS

This is the largest study evaluating the epidemiology of annular pancreas. We found the estimated prevalence rate of annular pancreas to be 3.4/100,000 in those who had abdominal imaging. Annular pancreas was more likely to be diagnosed in patients with symptoms pertaining to acute or chronic pancreatitis, biliary, and gastric outlet obstruction.

Congenital anomalies of the gastrointestinal tract: the liver, extrahepatic biliary tree and pancreas

Congenital anomalies of the liver, biliary tree and pancreas are rare birth defects, some of which are characterized by a marked variation in geographical incidence. Morphogenesis of the hepatobiliary and pancreatic structures initiates from two tubular endodermal evaginations of the most distal portion of the foregut. The pancreas develops from a larger dorsal and a smaller ventral outpouching; emergence of the two buds will eventually lead to the fusion of the duct system. A small part of the remaining ventral diverticulum divides into a "pars cystica" and "pars hepatica", giving rise to the cystic duct and gallbladder and the liver lobes, respectively. Disruption or malfunctioning of the complex mechanisms leading to the development of liver, gallbladder, biliary tree and pancreas can result in numerous, albeit fortunately relatively rare, congenital anomalies in these organs. The type and severity of anomalies often depend on the exact moment in which disruption or alteration of the embryological mechanisms takes place. Many theories have been brought forward to explain their embryological basis; however, no agreement has yet been reached for most of them. While in some cases pathological evaluation might be more centered on macroscopic evaluation, in other instances small biopsies will be the keystone to understanding organ function and treatment results in the context of congenital anomalies. Thus, knowledge of the existence and histopathological characteristics of some of the more common conditions is mandatory for every pathologist working in the field of gastrointestinal pathology.

Prenatal Detection of Congenital Duodenal Obstruction—Impact on Postnatal Care

Background: Duodenal obstruction is a rare cause of congenital bowel obstruction. Prenatal ultrasound could be suggestive of duodenal atresia if polyhydramnios and the double bubble sign are visible. Prenatal diagnosis should prompt respective prenatal care, including surgery. The aim of this study was to investigate the rate and importance of prenatally diagnosed duodenal obstruction, comparing incomplete and complete duodenal obstruction. Methods: A retrospective, single-center study was performed using data from patients operated on for duodenal obstruction between 2004 and 2019. Prenatal ultrasound findings were obtained from maternal logbooks and directly from the investigating obstetricians. Postnatal data were obtained from electronic charts, including imaging, operative notes and follow-up. Results: A total of 33/64 parents of respective patients agreed to provide information on prenatal diagnostics. In total, 11/15 patients with complete duodenal obstruction and 0/18 patients with incomplete duodenal obstruction showed typical prenatal features. Prenatal diagnosis prompted immediate surgical treatment after birth. Conclusion: Prenatal diagnosis of congenital duodenal obstruction is only achievable in cases of complete congenital duodenal obstruction by sonographic detection of the pathognomonic double bubble sign. Patients with incomplete duodenal obstruction showed no sign of duodenal obstruction on prenatal scans and thus were diagnosed and treated later.

Novel compound heterozygous CCDC40 mutations in a familial case of primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by motile ciliary dysfunction and impaired ultrastructure. Despite numerous studies, the genetic basis for about 30% of PCD cases remains to be elucidated. Here, we present the identification and functional analysis of two novel mutations in the gene encoding coiled-coil domain-containing protein 40 (CCDC40), which are found in a familial case of PCD. These novel CCDC40 mutations, NM_017950.4: c.2236-2delA and c.2042_2046delTCACA, NP_060420.2: p.(Ile681fs), were identified by whole-exome sequencing (WES). Sanger sequencing was then performed to confirm the WES results and determine the CCDC40 gene sequences of the proband's parents. The c.2042_2046delTCACA mutation disrupts the reading frame of the protein and is therefore predicted to produce a non-functional protein. Using a minigene assay with the pcDNA3.1(+) plasmid, we further investigated the potential pathogenic effects of the c.2236-2delA mutation and found that this mutation leads to formation of a truncated protein via splicing disruption. Thus, in summary, we identified two mutations of the CCDC40 gene that can be considered pathogenic compound heterozygous mutations in a case of familial PCD, thereby expanding the known mutational spectrum of the CCDC40 gene in this disease.

Investigation of annular pancreas through multiple detector spiral CT (MDCT) and MRI

BACKGROUND AND PURPOSE

To investigate annular pancreas in adults using imaging features displayed on computed tomography (CT) and magnetic resonance imaging (MRI).

METHODS

Retrospective review of annular pancreas in patients undergoing CT or MRI examinations. Two abdominal radiologists blindly reviewed the CT, MRI, and magnetic resonance cholangiopancreatography (MRCP) images from the Picture Archiving and Communication Systems (PACS). A Kruskal-Wallis test was performed to evaluate subjective scoring, with Mann-Whitney test for the comparison. A p-value less than 0.05 was considered statistically significant.

RESULTS

Eleven patients (45.8%) presented a complete ring of pancreatic tissue surrounding duodenum, displayed as circular, triangular, or sandwich sign configuration, the other 13 patients (54.2%) had incomplete annular pancreas which displayed a crocodile jaw appearance, pancreatic tissue extending in a posterolateral or anterolateral direction towards duodenum. When comparing CT images of each sequence, the arterial phase group had the highest score compared with the venous phase and the plain film group (χ²  = 58.21, p < 0.05). When comparing MRI enhancement volumetric interpolated breath-hold examination (VIBE) sequences, arterial phase group scores were the highest (χ²  = 18.98, p < 0.05).

CONCLUSIONS

Both CT and MRI could detect annular pancreas, with artery phase being the best sequence to diagnose annular pancreas.

The development of zebrafish pancreas affected by deficiency of Hedgehog signaling

The pancreas development depends on complex regulation of several signaling pathways, including the Hedgehog (Hh) signaling via a receptor complex component, Smoothened, which deficiency blocks the Hh signaling. Such a defect in birds and mammals results in an annular pancreas. We showed that in developing zebrafish, the mutation of Smoothened or inhibition of Hh signaling by its antagonist cyclopamine caused developmental defects of internal organs, liver, pancreas, and gut. In particular, the pancreatic primordium was duplicated. The two exocrine pancreatic primordia surround the gut. This phenomenon correlates with a significant reduction of the gut's diameter, causing the annular pancreas phenotype.

Clinical characteristics of adult-type annular pancreas: A case report

BACKGROUND

Annular pancreas (AP) is a rare congenital abnormal rotation of the pancreas. AP rarely occurs in adults. Pancreatic tumors and ampullary tumors are related to AP, so the discovery and treatment of AP are essential.

CASE SUMMARY

This study investigated the clinical manifestations, imaging features, complications, and treatment of six patients diagnosed with AP at the Department of Hepatobiliary and Pancreatic Surgery, First Hospital of Jilin University from January 2010 to June 2020. There were four males and two females, with an average age of 56.00 ± 9.86 years old. In this study, abdominal pain and jaundice were the main clinical manifestations. Imaging can show the “crocodile jaw sign” or “double bubble sign”.

CONCLUSION

For patients with duodenal or biliary obstruction, physicians should give priority to AP when imaging examinations suggest that the duodenum is wrapped with tissue similar to the density of the pancreas. Symptomatic patients should actively undergo surgical treatment.

Animal Models of Pancreas Development, Developmental Disorders, and Disease

The pancreas is a glandular organ responsible for diverse homeostatic functions, including hormone production from the endocrine islet cells to regulate blood sugar levels and enzyme secretion from the exocrine acinar cells to facilitate food digestion. These pancreatic functions are essential for life; therefore, preserving pancreatic function is of utmost importance. Pancreas dysfunction can arise either from developmental disorders or adult onset disease, both of which are caused by defects in shared molecular pathways. In this chapter, we discuss what is known about the molecular mechanisms controlling pancreas development, how disruption of these mechanisms can lead to developmental defects and disease, and how essential pancreas functions can be modeled using human pluripotent stem cells. At the core of understanding of these molecular processes are animal model studies that continue to be essential for elucidating the mechanisms underlying human pancreatic functions and diseases.

Sufu- and Spop-mediated downregulation of Hedgehog signaling promotes beta cell differentiation through organ-specific niche signals

Human embryonic stem cell-derived beta cells offer a promising cell-based therapy for diabetes. However, efficient stem cell to beta cell differentiation has proven difficult, possibly due to the lack of cross-talk with the appropriate mesenchymal niche. To define organ-specific niche signals, we isolated pancreatic and gastrointestinal stromal cells, and analyzed their gene expression during development. Our genetic studies reveal the importance of tightly regulated Hedgehog signaling in the pancreatic mesenchyme: inactivation of mesenchymal signaling leads to annular pancreas, whereas stroma-specific activation of signaling via loss of Hedgehog regulators, Sufu and Spop, impairs pancreatic growth and beta cell genesis. Genetic rescue and transcriptome analyses show that these Sufu and Spop knockout defects occur through Gli2-mediated activation of gastrointestinal stromal signals such as Wnt ligands. Importantly, inhibition of Wnt signaling in organoid and human stem cell cultures significantly promotes insulin-producing cell generation, altogether revealing the requirement for organ-specific regulation of stromal niche signals.

Annular pancreas in a 24-year-old woman with persistent abdominal pain

Annular pancreas (AP) is a rare diagnosis in the adult population but can cause significant morbidity if not correctly identified. In adults, the most common symptoms are abdominal pain, nausea and vomiting. While these are not specific to AP, they are important clues to this diagnosis in the right clinical context. We present the case of a 24-year-old woman presenting with a 6-year history of progressive abdominal pain and dyspepsia in the context of an extensive negative workup. Upper gastrointestinal (GI) series and MRI revealed partial duodenal obstruction, concerning for AP. While patients with chronic abdominal pain and vague GI complaints may be diagnosed with functional bowel disorders, it is important to appropriately address the possibility of an underlying structural lesion such as AP. This strategy is not only cost-effective but also saves the patient discomfort associated with unnecessary procedures and allows a timely intervention.

Laparoscopic Roux-en-Y duodenojejunostomy for annular pancreas in adults: case report and literature review

Annular pancreas is in adults is a rare congenital anomaly which incidence varied from 0.005% to 0.015%. Although 33% of the cases are symptomatic, the symptoms are most commonly associated with gastric outlet obstruction. Here we presented an adult diagnosed with annular pancreas treated by laparoscopic Roux-en-Y side to side duodenojejunostomy.

GATA4 and GATA6 regulate pancreatic endoderm identity through inhibition of hedgehog signaling

GATA4 and GATA6 are zinc finger transcription factors that have important functions in several mesodermal and endodermal organs, including heart, liver and pancreas. In humans, heterozygous mutations of either factor are associated with pancreatic agenesis; however, homozygous deletion of both Gata4 and Gata6 is necessary to disrupt pancreas development in mice. In this study, we demonstrate that arrested pancreatic development in Gata4(fl/fl); Gata6(fl/fl); Pdx1:Cre (pDKO) embryos is accompanied by the transition of ventral and dorsal pancreatic fates into intestinal or stomach lineages, respectively. These results indicate that GATA4 and GATA6 play essential roles in maintaining pancreas identity by regulating foregut endodermal fates. Remarkably, pancreatic anlagen derived from pDKO embryos also display a dramatic upregulation of hedgehog pathway components, which are normally absent from the presumptive pancreatic endoderm. Consistent with the erroneous activation of hedgehog signaling, we demonstrate that GATA4 and GATA6 are able to repress transcription through the sonic hedgehog (Shh) endoderm-specific enhancer MACS1 and that GATA-binding sites within this enhancer are necessary for this repressive activity. These studies establish the importance of GATA4/6-mediated inhibition of hedgehog signaling as a major mechanism regulating pancreatic endoderm specification during patterning of the gut tube.

Differential role of Hedgehog signaling in human pancreatic (patho-) physiology: An up to date review

Since the discovery of the Hedgehog (Hh) pathway in drosophila melanogaster, our knowledge of the role of Hh in embryonic development, inflammation, and cancerogenesis in humans has dramatically increased over the last decades. This is the case especially concerning the pancreas, however, real therapeutic breakthroughs are missing until now. In general, Hh signaling is essential for pancreatic organogenesis, development, and tissue maturation. In the case of acute pancreatitis, Hh has a protective role, whereas in chronic pancreatitis, Hh interacts with pancreatic stellate cells, leading to destructive parenchym fibrosis and atrophy, as well as to irregular tissue remodeling with potency of initiating cancerogenesis. In vitro and in situ analysis of Hh in pancreatic cancer revealed that the Hh pathway participates in the development of pancreatic precursor lesions and ductal adenocarcinoma including critical interactions with the tumor microenvironment. The application of specific inhibitors of components of the Hh pathway is currently subject of ongoing clinical trials (phases 1 and 2). Furthermore, a combination of Hh pathway inhibitors and established chemotherapeutic drugs could also represent a promising therapeutic approach. In this review, we give a structured survey of the role of the Hh pathway in pancreatic development, pancreatitis, pancreatic carcinogenesis and pancreatic cancer as well as an overview of current clinical trials concerning Hh pathway inhibitors and pancreas cancer.

Symptomatic annular pancreas in adult: Report of two different presentations and treatments and review of the literature

Annular pancreas (AP) in adults is a rare embryologic abnormality detected after development of complications or as incidental finding. Diagnosis and treatment strategies for symptomatic adult AP remain controversial.

We describe two different presentation of AP: a woman with a specific upper abdominal pain treated with medical therapy and a man with upper gastroenteric obstructive symptoms which underwent surgical duodeno-jejunal by-pass. English language literature about annular pancreas etiology, diagnosis and treatment was reviewed.

No specific guidelines and protocols exist about management of AP, therefore, treatment and operative approaches must be individualized. In consideration of the possible post-operative complications, surgical treatment should be reserved in case of failure of conservative medical therapies.

Annular pancreas: Culprit or innocent bystander?

Annular pancreas is a rare congenital anomaly that has been often implicated in duodenal and biliary obstructions. However, the true incidence of such presentation is very low. We present a case of a 57-year-old female with mixed hepatocellular and obstructive jaundice where annular pancreas was an innocent bystander.

Pancreas divisum: a common developmental variant that deserves attention in preclinical medical education

Clinical literature indicates that pancreas divisum (PD) is present in 3-22% of the population and may be associated with an increased risk of pancreatitis. PD is a developmental variant wherein the duct systems derived from the dorsal and ventral pancreatic buds are not fused. Hence secretions from the head, neck, body, and tail, which develop from the dorsal bud, must pass through the minor duodenal papilla. The smaller uncinate process, derived from the ventral bud, drains through the major duodenal papilla. The purpose of this study was: (1) to do a cadaveric dissection to confirm whether PD is common in donors who had not been selected because they had pancreatitis and (2) to determine the frequency of PD descriptions in anatomy, embryology, pathology, and surgery books in our libraries. For our anatomical study, pancreata of eight human donors were dissected. Dye was injected into the ducts so that any communications between main and accessory ducts could be easily located. For our literature review, 22 anatomy, 14 embryology, 11 pathology, and 26 surgery books were examined for mention of PD. PD was unambiguously identified in two donor cadavers. However, only 14% of the anatomy plus embryology books compared to 70% of the surgery plus pathology books describe PD. Cadaveric dissection confirms that PD is indeed prevalent. The prevalence of PD with its increased risk of pancreatitis merits inclusion of this topic in textbooks of anatomy and embryology.

Annular pancreas concurrent with pancreaticobiliary maljunction presented with symptoms until adult age: case report with comparative data on pediatric cases

Background

Annular pancreas (AP) concurrent with pancreaticobiliary maljunction (PBMJ), an unusual coexisted congenital anomaly, often presented symptoms and subjected surgical treatment at the early age of life. We reported the first adult case of concurrent AP with PBMJ presented with symptoms until his twenties, and performed a literature review to analyze the clinicopathological features of such cases comparing with its pediatric counterpart.

Case presentation

The main clinical features of this case were abdominal pain and increased levels of plasma amylase as well as liver function test. A complete type of annular pancreas with duodenal stenosis was found, and dilated common bile duct with high confluence of pancreaticobiliary ducts was also observed. Meanwhile, extremely high levels of bile amylase were detected both in common bile duct and gallbladder. The patient received duodenojejunostomy (side-to-side anastomosis) as well as choledochojejunostomy (Roux-en-Y anastomosis), adnd was discharged in a good condition.

Conclusion

AP concurrent with PBMJ usually presents as duodenal obstruction in infancy, while manifests as pancreatitis in adulthood. Careful long-term follow-up is required for children with AP considering its association with PBMJ which would induce various intractable pathologic conditions in the biliary tract and pancreas.