Mediastinal Extension of Pancreatic Pseudocyst: A Rare Pediatric Presentation.

Pancreatic pseudocysts are cystic cavities which are localized collection of pancreatic secretions, rich in amylase and other enzymes, present in and around pancreas, encased in a false epithelial lining of fibrous or reactive granulation tissue. Extension of a pancreatic pseudocyst into the mediastinum is rare. We are reporting a case of a 5-year-old child with mediastinal pancreatic pseudocyst which was successfully drained by cystojejunostomy. Copyright:

INTRODUCTION

Pancreatic pseudocysts are localized collections of pancreatic secretions without an epithelial lining. Thoracic extension can occur due to pancreatic duct disruption, causing secretions to pass through the diaphragmatic orifices into the mediastinum. There are fewer than 100 cases of mediastinal pancreatic pseudocyst reported in the literature.[1] They can occur at any age, with chronic alcoholism as a common cause in adults, while >60% of reported cases in children occur due to blunt abdominal trauma.[2] Galligan and Williams reported the first case of mediastinal pancreatic pseudocyst in 1966.[3] We are reporting a case of a 5-year-old child with pancreatic pseudocyst, having mediastinal extension, who underwent a cystojejunostomy.

CASE REPORT

A 5-year-old boy had a history of repeat episodes of dull aching upper abdominal pain for 3 years. He underwent extensive radiological investigations and was diagnosed to have pancreatic pseudocyst with mediastinal extension. Endoscopic or open intervention was not attempted, and he was managed conservatively. He continued to have recurrent symptoms. At presentation to us, the child was asymptomatic but had a prominent barrel-shaped chest. Primary investigations revealed raised serum amylase – 359 U/L. Magnetic resonance imaging (MRI) abdomen and chest reported diffuse pancreatic atrophy with large collection below the body of pancreas extending into posterior mediastinum through esophageal hiatus of diaphragm [Figure 1]. Left gastric artery was seen traversing through the base, while thoracic component was abutting posterior pericardium, compressing left atrium, and esophagus was coursing through it. Cardiac assessment was normal. Endoscopic drainage was deemed inadvisable due to the proximity of the gastric artery to the base of cyst. An exploratory laparotomy was performed, where cyst was noted at the posterior aspect of stomach. It was aspirated through a small incision, and dye was injected to gauge connection to the mediastinal component. Wide communication between thoracic and abdominal components was established under fluoroscopic guidance [Figure 2]. Cystogastrostomy was not attempted in view of proximity to the left gastric artery, so the patient underwent a cystojejunostomy with Roux-en-Y loop creation [Figure 3]. Amylase level of aspirated fluid was 33370 U/L. The postoperative period was uneventful. Ultrasound done after a week reported a small residual collection adjacent to the body of pancreas. Serum amylase levels dropped to 81 U/L. Follow-up ultrasound after a month reported complete resolution of the mediastinal pseudocyst, and the child is asymptomatic.

Figure 1

Magnetic resonance imaging showing the intrathoracic extension and gastric artery at the base of pseudocyst

Figure 2

Opening of pseudocyst

Figure 3

Cystojejunostomy

DISCUSSION

One of the early sequelae of acute pancreatitis is pseudocyst of pancreas, as per the Revised Atlanta classification.[4] Although 2% of cases of pancreatitis result in pseudocyst formation, intrathoracic extension can only be seen in 0.4% of cases, which makes it quite a rare complication.[5] Pseudocysts are usually located within head and body of pancreas, but extrapancreatic extensions can occur anywhere around liver, spleen, mediastinum, neck, and pelvis.

When the pancreatic duct gets disrupted, the amylase-rich secretions seep along the path of least resistance. A thoracopancreatic fistula will arise if the disruption occurs in the retroperitoneal space and leaks through aortic or esophageal openings into the thoracic cavity. These fistulae can be further subdivided into pancreaticopericardial, pancreaticopleural, pancreaticobronchial, or a mediastinal pseudocyst.[6]

We shall now focus the discussion to one of the varieties, the mediastinal pseudocyst, which was the final diagnosis of our case. To the best of our knowledge, only nine cases and a case series have been reported in the pediatric age group, in addition to ours[7] [Table 1]. These patients usually present with complaints of vague/diffuse upper abdominal pain, dysphagia, dyspnea, or retrosternal discomfort. The symptoms can often be misleading as they are mostly an end result of compression of mediastinal structures. However, as noted in our case, patients might only have occasional symptoms, and even abdominal palpation might not reveal significant findings as the pseudocyst can decompress into thorax through diaphragmatic hiatus.[8]

Table 1

Pediatric mediastinal pancreatic pseudocyst cases reported in literature

Study	Age	Symptoms	Abdominal mass	Route of extension	Suspected cause	Treatment	Associated pancreatitis
Kirchner et al.	7 months	Dyspnea	No	Foramen of Morgagni	Idiopathic	Roux-en-Y cystojejunostomy	No
Crombleholme et al.	2 years	Vomiting	No	Esophageal hiatus	Anomalous duct	Roux-en-Y cystojejunostomy	No
-	7 years	Pain in abdomen	No	Esophageal hiatus	Anomalous duct	Puestow’s procedure	Yes
Kotb et al.	7 years	Dyspnea	No	Esophageal hiatus	Idiopathic	Cystogastrostomy	No
Sharma et al.	8 years	Dyspnea, chest pain	No	Traumatic diaphragmatic hernia	Trauma	Cystogastrostomy	No
Galligan et al.	10 years	Nausea, vomiting, anorexia	Yes	Esophageal hiatus	Idiopathic	Cystogastrostomy	No
Bonnard et al.	11 years	Not mentioned	Not mentioned	Not mentioned	Anomalous duct	Thoracoscopic drainage	Not mentioned
Nabi et al.	11 years	Pain in abdomen	No	Not mentioned	Idiopathic	Endoscopic - Transgastric drainage	Yes
Laird et al.	15 years	Nausea, vomiting, anorexia	No	Esophageal hiatus	Trauma	Puestow procedure	No
Lakhtakia S et al.	4 patients	Pain in abdomen, vomiting, dysphagia	No	Not mentioned	Not mentioned	EUS-guided transesophageal drainage with double pigtail stent	Not mentioned
Our case	5 years	Pain in abdomen	No	Esophageal hiatus	Idiopathic	Roux-en-Y cystojejunostomy	No

As the physical examination is mostly inconclusive, investigations play a bigger role in establishing the diagnosis. Blood investigations help to point the etiology toward a pancreatic origin as serum amylase in invariably raised. However, the diagnosis of a mediastinal pseudocyst is typically established by various radiologic investigations such as ultrasound, computed tomography (CT), and magnetic resonance cholangiopancreatography (MRCP). Ultrasound abdomen can easily demonstrate a peripancreatic collection but might be less helpful in delineating a mediastinal pseudocyst, owing to its location. CT of abdomen and chest with contrast enhancement not only outlines the pancreatic anomaly but also detects the mediastinal component. However, MRI of the abdomen provides detailed information about pancreatic ductal morphology, while MRCP is the best modality to detect stricture/dilatation of duct and communication with pseudocyst. Endoscopic ultrasound can be diagnostic and therapeutic modality as it not only detects mediastinal extension of pseudocyst but also can be used for cyst aspiration.[9] Our patient had a raised serum amylase level, and the definitive diagnosis was made with MRI of abdomen and chest with contrast enhancement.

Individualized treatment plan is made according to the underlying cause, anomaly of the pancreatic duct, and symptoms experienced by the patient [Figure 4]. Conservative management of pediatric mediastinal pancreatic pseudocyst entails the following. Octreotide and bromhexine hydrochloride can be used to decrease pancreatic secretions, while supportive management can be in the form of low-fat diet, antibiotics, analgesics, and intravenous fluid, if required. These methods rarely end in spontaneous regression, as it requires strict compliance and follow-up. It was also unsuccessful in our case, as evidenced by symptom recurrence in patient. Thus, surgical options were explored.

Figure 4

Management flowchart for mediastinal pseudocyst

Endoscopic cyst drainage procedures through transesophageal, transgastric, or transpapillary routes have been described in literature.[10] These methods are mainly reported in the adult population as endoscopic cyst drainage in pediatric age group requires expertise and is often deemed unfeasible due to possible difficulty of scope negotiation or stent placement.

The mainstay of surgery in pediatric as well as adult age group is cyst drainage by creating an outlet within the gastrointestinal system, commonly in the stomach or jejunum. Open surgeries include internal or external drainage or pancreatic resection. Procedures commonly done include cystogastrostomy, Roux-en-Y cystojejunostomy, and Puestow's procedure, largely depending on the anatomic location of the cyst. Cystogastrostomy is preferred for retrogastric cyst adherent to stomach, while pseudocysts located at the base of transverse mesocolon are best drained by cystojejunostomy with preferential drainage of secretions into the Roux loop of jejunum. The Roux loop prevents reflux of food and bile into the cyst and also prevents activation of the pancreatic secretions until they reach jejunum.[11] If a wide tract is patent between the abdominal and thoracic components of pancreatic pseudocyst, drainage of the abdominal collection can reduce the pressure in thoracic compartment, leading to resolution of mediastinal pseudocyst. A successful outcome is described as resolution of symptoms and decrease in the size/disappearance of the cyst, documented by radiological investigations, as seen in our case.

CONCLUSION

Mediastinal pancreatic pseudocyst is a rare pathology, but it should be considered a differential diagnosis of any cystic mediastinal mass. Radiological investigations can establish communication between a cystic structure in the mediastinum with peripancreatic collection. Open drainage procedure can be a safer alternative in children as endoscopic procedures require expertise.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.