Pediatric Annals

Feature Article 

Meandering Main Pancreatic Duct in Association with Choledochal Cysts and Acute Pancreatitis in Pediatrics

Arvind V. Panchoo, MD; Juan C. Infante, MD; Edgardo D. Rivera Rivera, MD

Abstract

Meandering main pancreatic duct (MMPD) is an uncommon anomaly of the main pancreatic duct characterized by an abnormal curvature at the pancreatic head region. This variant can be diagnosed on imaging, particularly magnetic resonance cholangiopancreatography (MRCP). Although its clinical significance remains debatable, recent research suggests an association with recurrent acute pancreatitis. To our knowledge, no pediatric cases of acute or recurrent acute pancreatitis have been attributed to the presence of MMPD. In this article, we report on two patients. The first case is of a 15-year-old girl with MMPD discovered on investigation of idiopathic acute pancreatitis. The second case is of a 5-year-old boy who presented with his second episode of acute pancreatitis. In this patient, MRCP imaging revealed MMPD and type IVA choledochal cyst. With appropriate care, both patients experienced clinical improvement with resolution of abdominal pain. This article highlights MMPD as a distinct entity that should be considered in pediatric patients with recurrent attacks of acute pancreatitis. This report also describes the first association of MMPD with choledochal cysts. [Pediatr Ann. 2019;48(10):e412–e416.]

Abstract

Meandering main pancreatic duct (MMPD) is an uncommon anomaly of the main pancreatic duct characterized by an abnormal curvature at the pancreatic head region. This variant can be diagnosed on imaging, particularly magnetic resonance cholangiopancreatography (MRCP). Although its clinical significance remains debatable, recent research suggests an association with recurrent acute pancreatitis. To our knowledge, no pediatric cases of acute or recurrent acute pancreatitis have been attributed to the presence of MMPD. In this article, we report on two patients. The first case is of a 15-year-old girl with MMPD discovered on investigation of idiopathic acute pancreatitis. The second case is of a 5-year-old boy who presented with his second episode of acute pancreatitis. In this patient, MRCP imaging revealed MMPD and type IVA choledochal cyst. With appropriate care, both patients experienced clinical improvement with resolution of abdominal pain. This article highlights MMPD as a distinct entity that should be considered in pediatric patients with recurrent attacks of acute pancreatitis. This report also describes the first association of MMPD with choledochal cysts. [Pediatr Ann. 2019;48(10):e412–e416.]

Acute pancreatitis is on the rise in the pediatric population, with a reported incidence of approximately 1 in 10,000 children annually, which is a rate approaching that seen in adults.1 In most pediatric patients, pancreatitis is self-limiting and reversible, but can be lethal.2,3

Causes of acute pancreatitis in the pediatric setting include trauma, systemic illness, structural anomalies, biliary stones, or hereditary factors such as gene mutations.1 In general, most cases of acute pancreatitis do not require thorough testing. However, if warranted, further testing may reveal etiologies that predispose to recurrent episodes or severe presentations of pancreatitis.4

In investigating severe and recurrent cases of acute pancreatitis, abnormalities of the main pancreatic duct such as anomalous arrangement of the pancreaticobiliary ductal system, pancreas divisum, and ansa pancreatica are occasionally encountered.5 Meandering main pancreatic duct (MMPD) is another such variant. This entity is characterized by an abnormal curvature of the pancreatic duct at the pancreatic head region, with the ventral duct taking either a loop (loop type) or hairpin (reverse-Z type) turn before emptying into the major papilla of the duodenum.4

MMPD can be easily diagnosed on review of coronal images of endoscopic retrograde cholangiopancreaticography (ERCP) or magnetic resonance cholangiopancreatography (MRCP).4

Although its clinical significance remains debatable, recent research suggests an association with recurrent acute pancreatitis.4 To our knowledge, no pediatric cases of acute or recurrent acute pancreatitis have been attributed to the presence of MMPD. In this article, we present two pediatric cases of loop type MMPD that were discovered on further analysis of acute episodes of pancreatitis.

Illustrative Case 1

A 15-year-old girl presented to the emergency department with a 2-week history of worsening abdominal pain. She described that initially the pain was located in the umbilical region but had progressed to involve the entire lower abdomen and had significantly increased in intensity. The pain was constant and was not associated with any food intake or periodicity. It was associated with a 1-day history of nausea, vomiting, diarrhea, and decreased oral intake. This was the first episode of such severe pain, but she did describe intermittent episodes of vague lower abdominal pain occurring sporadically for the past 3 months that would resolve spontaneously. No history of trauma, alcohol use, or commencement of any new medications in the recent past was noted. Physical examination was significant for diffuse lower abdominal tenderness with stable vital signs.

Initially, consideration was given to acute gastroenteritis by the general pediatric service, but with persistence of symptoms despite conservative therapy the pediatric gastroenterology team was consulted and further investigation was pursued. Laboratory evaluation revealed elevated amylase at 284 U/L (reference range 30–110 U/L) and lipase at 1,565 U/L (reference range 23–300 U/L). Extensive testing was done to identify the source of the pancreatitis, but no culprits were identified. Her triglyceride level, electrolytes, bilirubin, and hepatic function panel were all within normal limits. Also, she had a negative autoimmune screen. MRCP imaging, to rule out anatomical abnormalities that could potentially explain this episode, was performed and was significant for a loop in the ventral pancreatic duct at the head of the pancreas, consistent with MMPD (Figure 1 and Figure 2). No other abnormalities of the abdomen or pancreaticobiliary tract were appreciated.

Post-processed three-dimensional maximum intensity projection magnetic resonance cholangiopancreatography image showing abnormal curvature of the ventral pancreatic duct, forming a loop in the region of the head of pancreas.

Figure 1.

Post-processed three-dimensional maximum intensity projection magnetic resonance cholangiopancreatography image showing abnormal curvature of the ventral pancreatic duct, forming a loop in the region of the head of pancreas.

Post-processed three-dimensional volume rendered magnetic resonance cholangiopancreatography image showing abnormal curvature of the ventral pancreatic duct, forming a loop in the region of the head of pancreas.

Figure 2.

Post-processed three-dimensional volume rendered magnetic resonance cholangiopancreatography image showing abnormal curvature of the ventral pancreatic duct, forming a loop in the region of the head of pancreas.

With continued care the patient's oral tolerance steadily improved and the nausea, vomiting, diarrhea and abdominal pain resolved. Lipase levels decreased through discharge and were normalized (68 U/L) on outpatient follow up (Table 1).

Lipase Value Trend for Illustrative Case 1

Table 1:

Lipase Value Trend for Illustrative Case 1

Illustrative Case 2

A 5-year-old boy presented with a 1-week history of worsening abdominal pain and a 1-day history of nausea, vomiting, and decreased oral intake. This pain was located in the epigastric region but with no radiation to the back. It was described as constant and was not associated with any food intake or periodicity. No history of trauma or concurrent illness in the recent past was noted. Physical examination was significant for upper abdominal tenderness with stable vital signs. Laboratory evaluation revealed elevated amylase at 630 U/L (reference range 30–110 U/L) and lipase at 6,538 U/L (reference range 23–300 U/L). Ultrasound of the abdomen was notable for a cystic structure in the region of the pancreatic head. After stabilization of this acute episode of pancreatitis, the patient was transferred to our institution for further management.

The patient's parents gave a history of similar pain associated with hyperamylasemia and hyperlipasemia 2 years prior. Imaging during that episode revealed a pancreatic fluid collection that required endoscopic drainage.

Extensive testing was done to identify the source of recurrent pancreatitis. Electrolytes, bilirubin, and hepatic function panel were all grossly normal. An MRCP scan (Figure 3 and Figure 4) to further delineate the anatomy of the pancreaticobiliary ductal system was significant for a loop in the ventral pancreatic duct and choledochal cysts of the common bile duct (measuring 2.6 cm × 3.4 cm) and left hepatic duct (measuring 1.2 cm × 2.8 cm).

Coronal magnetic resonance cholangiopancreatography images depicting looping (white arrows) of main pancreatic duct in pancreatic head region

Figure 3.

Coronal magnetic resonance cholangiopancreatography images depicting looping (white arrows) of main pancreatic duct in pancreatic head region

Post-processed three-dimensional volume rendered magnetic resonance cholangiopancreatography images showing type IVA choledochal cyst. Note fusiform common bile duct dilatation (arrow) and cystic left intrahepatic dilatation (star).

Figure 4.

Post-processed three-dimensional volume rendered magnetic resonance cholangiopancreatography images showing type IVA choledochal cyst. Note fusiform common bile duct dilatation (arrow) and cystic left intrahepatic dilatation (star).

Given the size of the common bile duct biliary cyst and risk of malignant progression, the pediatric surgery team was consulted. The patient underwent a laparoscopic choledochal cyst excision with Roux-en-Y hepaticojejunostomy and cholecystectomy. His postoperative course was uneventful, and he was discharged with no abdominal pain and good oral tolerance. At his outpatient follow-up appointment 2 weeks later, his lipase had trended down to 228 U/L (Table 2) and he remained asymptomatic with no further episodes of abdominal pain.

Lipase Value Trend for Illustrative Case 2

Table 2:

Lipase Value Trend for Illustrative Case 2

Discussion

MMPD is a recently described entity, formally grouped and defined in 2012 by Gonoi et al.4 It has two subtypes: the loop type (as seen in the patients discussed here) and the reverse-Z type. It is a relatively uncommon entity, with one study estimating the prevalence to be 2.2% in the general population.4

The etiology remains largely unknown, but given its location in the pancreatic head, where other fusion variants such as pancreas divisum, anomalous arrangement of the pancreaticobiliary ductal system, and ansa pancreatica exist, it has been postulated by some to result from aberrant fusion of the dorsal and ventral pancreatic anlagen during fetal development.4

In a cross-sectional study performed at a tertiary center, MMPD was noted to have 40% prevalence in cases of idiopathic recurrent pancreatitis. The results of univariate analysis of this study revealed a significant positive association of MMPD to the onset of pancreatitis (P = .0002; odds ratio 4.01 [95% confidence interval (CI), 1.92–6.11]) and recurrent acute pancreatitis (P = .0001; odds ratio 26.2 [95% CI, 22.2–30.2]).4

The mechanism by which MMPD induces attacks of pancreatitis is not well established. Initial cases of MMPD were not associated with pancreatic duct dilatation, leading Gonoi et al.4 to conclude that mechanical hypertension due to altered pancreatic duct anatomy plays little role in provoking episodes of pancreatitis. However since the publication of that article, there have been a few reports of MMPD accompanied with prominent main pancreatic duct and side branches, suggesting a larger role for mechanical obstruction in leading to pancreatitis.5,6 Neither one of our cases demonstrated dilation of pancreatic duct or its side branches on imaging, although it must be noted that initial imaging was either delayed (difficulty in diagnosing acute pancreatitis in first case) or unavailable (initial ultrasound done at another institution and MRCP not obtained until after resolution of acute pancreatitis episode in the second case).

Some readers may question whether the patient described in Illustrative Case 1 should be diagnosed with acute pancreatitis given the nonspecific nature of her abdominal pain. However, the “classic” presentation of epigastric pain radiating to the back occurs in only 1.6% to 5.6% of pediatric patients, with diffuse abdominal pain being seen in as much as 20% of pediatric cases.1

In the patient described in Illustrative Case 2 with recurrent acute pancreatitis, MRCP imaging revealed the presence of type IVA choledochal cysts (Figure 4). Choledochal cysts are rare dilatations of the biliary tree seen primarily in children.7 Type IVA consists of both intrahepatic and extrahepatic cystic dilatations and they are the second most common type of choledochal cysts.8 Although it is thought to be congenital, the exact pathogenesis remains incompletely understood. They are associated with significant complications such as cholangiocarcinoma, cholangitis, perforation, and hepatic failure. Hence, when possible, prompt surgical excision is generally performed, as in our patient.7

A number of reports have described choledochal cysts in association with pancreas divisum,9–13 a congenital abnormality of the pancreatic ducts. However, this article is the first reported finding of such cysts in association with MMPD.

Gonoi et al.,4 after review of patients with MMPD-associated pancreatitis at their health care center, suggested that pancreatitis in patients with MMPD may be less severe than pancreatitis in patients without MMPD. However, our second patient's initial episode of pancreatitis required endoscopic drainage of a pancreatic fluid collection; this would allow classification of his first pancreatic episode as moderately severe acute pancreatitis according to the classification scheme proposed by the North America Society of Pediatric Gastroenterology, Hepatology and Nutrition Pancreas Committee.14

MMPD can be diagnosed on review of coronal images of ERCP or MRCP. MRCP is preferred due to its noninvasive nature, lack of post-procedure pancreatitis, and high sensitivity and specificity (approaching 100%) in visualizing the pancreatic ducts.4

One issue that became apparent during review of imaging is the potential confusion in differentiating MMPD versus ansa pancreatica, an S-shaped anomaly of the pancreatic ducts.15,16 Initially, the MRCP images of both cases were read as ansa pancreatica by our radiology team. Indeed, some pieces of literature we reviewed seem to refer to MMPD as ansa pancreatica.17,18 Anecdotally, one of the authors has had experience with a gastrointestinal endoscopist who referred to the MMPD appearance as “ansa pancreatica.” This is to say that there appears some inconsistency in how these terms are used in the literature and possibly in clinical practice, but we want to emphasize that MMPD and ansa pancreatica are two distinct entities with differing radiologic appearances that should be clearly defined on imaging before ascribing a diagnosis of either entity. All involved should be aware of this distinction so an accurate diagnosis can be made. Accurate diagnosis will allow true prevalence rates to be established and will aid in determining and contrasting clinical significance and long-term sequela among these uncommon pancreatic duct variants.

At present, the management of MMPD-associated pancreatitis follows that of acute pancreatitis of other causes.5,6 In both of our cases, once the diagnosis of acute pancreatitis was made, appropriate fluid hydration and pain control was initiated, leading to gradual resolution of symptoms. With a better understanding of the pathophysiology and evolution of pancreatitis in MMPD, more specific treatment protocols can be tailored to this disease process.

Conclusion

Using these cases, we hope to highlight MMPD as a consideration in pediatric patients with recurrent attacks of acute pancreatitis. Although still an uncommon cause of pancreatitis, MMPD should be sought when no other abnormalities are noted in a patient's testing.

This article also describes the first association of MMPD with choledochal cysts. If MMPD or other pancreatic ductal variants are detected, exploration for choledochal cysts should be done because they may require surgical resection to prevent considerable sequela.

Care should be taken to avoid confusing MMPD with other pancreatic duct abnormalities. Management of MMPD-associated pancreatitis follows that of acute pancreatitis of other causes, with adequate fluid resuscitation and pain control.

Further population studies to determine prevalence and significance in the pediatric population are warranted, and long-term follow-up must be considered because this entity can lead to repeated episodes of pancreatitis during a patient's life.

References

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  14. Abu-El-Haija M, Kumar S, Szabo F, et al. NASPGHAN Pancreas Committee. Classification of Acute Pancreatitis in the Pediatric Population: Clinical Report From the NASPGHAN Pancreas Committee. J Pediatr Gastroenterol Nutr.2017;64(6):984–990. https://doi.org/10.1097/MPG.0000000000001583 PMID: doi:10.1097/MPG.0000000000001583 [CrossRef]28333771
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Lipase Value Trend for Illustrative Case 1

Date Lipase Value, U/La
02/28/17 976
03/01/17 1,565
03/02/17 1,134
03/03/17 1,146
03/05/17 555
03/06/17 508
03/20/17 68

Lipase Value Trend for Illustrative Case 2

Date Lipase Value, U/La
03/18/16 6,358
03/24/16 1,882
03/26/16 3,283
03/27/16 3,729
03/28/16 3,378
03/29/16 2,664
03/31/16 2,222
04/02/16 612
04/03/16 435
04/04/16 832
04/05/16 1,166
04/06/16 1,424
04/14/16 228
Authors

Arvind V. Panchoo, MD, is a Pediatric Resident, Jackson Memorial Hospital. Juan C. Infante, MD, is an Assistant Professor of Pediatric Radiology, University of Miami Miller School of Medicine; and the Chief of Imaging Informatics, Department of Radiology, Jackson Memorial Hospital. Edgardo D. Rivera Rivera, MD, is a Pediatric Gastroenterologist, Pediatric Gastroenterology Hepatology and Nutrition, Parkview Health System.

Address correspondence to Edgardo D. Rivera Rivera, MD, Pediatric Gastroenterology Hepatology and Nutrition, Parkview Health System, 11123 Parkview Plaza Drive, Suite 200, Fort Wayne, IN 46845; email: Edgardo.RiveraRivera@parkview.com.

The authors thank Miguel Saps, MD (Division of Pediatric Gastroenterology and Nutrition, University of Miami), for reviewing the final manuscript.

Disclosure: The authors have no relevant financial relationships to disclose.

10.3928/19382359-20190916-01

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