Congenital Pancreatic Cyst

Diagnosis and Management

Congenital pancreatic cysts are extremely rare and pose unique diagnostic and surgical challenges. They are generally asymptomatic and discovered as an incidental abdominal swelling but may become symptomatic as a result of pressure on adjacent viscera ^(1–3). They can attain a large size and are difficult to diagnose preoperatively because they may be confused with pancreatic pseudocysts or duplication cyst of the pancreas. Embryologically, they arise from a developmental anomaly of the pancreatic ductal system ⁽⁴⁾. A variety of procedures were described to treat congenital pancreatic cyst depending on its location and feasibility. These include cystoduodenostomy, a Roux-en-Y cystojejunostomy, total cystectomy, and total cystectomy with distal pancreatectomy ^(1,5,6). We report 2 cases of true congenital pancreatic cyst and the literature on the subject is reviewed.

PATIENT 1

A 1.5-year-old boy was referred to our hospital with an abdominal mass. The mass was noticed 6 months before presentation and was small to start with but increased gradually. Clinically, he was well but found to have a large right abdominal mass that was firm in consistency. His complete blood cell count, electrolytes, blood urea nitrogen, creatinine, liver function tests, and amylase were normal. Abdominal ultrasound revealed a large cystic swelling measuring 9 × 8 cm seen in the midline anterior to the spine and extending to the right side, having turbid fluid content (Fig. 1). Abdominal computed tomography (CT) scan showed a thick wall cystic swelling about 9.2 × 9.7 × 9.7 cm seen mainly in the right side of the abdomen extending from the anterior abdominal wall up to the right anterior pararenal space posteriorly. The pancreatic head was distorted by the cyst and the rest of the pancreas was displaced anteriorly (Fig. 2). Magnetic resonance imaging revealed similar findings to the CT scan with no communication with the visualized biliary duct (Fig. 2). He underwent exploration laparotomy, which revealed a large cystic swelling occupying most of the right side of the abdomen and extending to the midline. It had a thick wall and part of the pancreas was stretched over it (Fig. 3). The cyst was dissected until it was completely removed. It was attached to the body of the pancreas with a stalk of tissue that was transfixed, tied, and cut (Fig. 4). Part of the stretched pancreatic tissue was excised and sent for histology. Postoperatively, he did well and was discharged home on the eighth postoperative day. Histology of the resected cyst showed a large smooth-surface unilocular cyst displaying a uniformally thick fibrous focally inflamed wall containing pancreatic tissue and cystically dilated ducts, lined by flattened epithelium, and few macrophages seen in the lumen. The sections from the resected stretched pancreatic tissue revealed simple cuboidal cell lined cystically dilated structures, at places showing stag horn-type ramifications. These were embedded and surrounded by pancreatic tissue and fibrosis septae, displaying foci of inflammation.

FIGURE 1: Abdominal ultrasound showing a large abdominal cystic swelling.

FIGURE 2: Abdominal computed tomography scan and magnetic resonance imaging showing a large unilocular cyst with thick wall and in the region of pancreas.

FIGURE 3: Clinical intraoperative photograph showing the dissected congenital pancreatic cyst. Note also the stretched and dissected pancreatic tissue overlying the cyst (arrow).

FIGURE 4: Clinical intraoperative photograph showing the already dissected pancreatic cyst. Note the stalk of tissue attaching the cyst to the body of the pancreas (large arrow) and the already dissected and stretched pancreatic tissue (small arrows). The cyst after complete excision.

PATIENT 2

A 4-month-old girl was referred to our hospital because of nonbile-stained vomiting and abdominal distension. The vomiting started immediately after birth and was on and off, whereas the abdominal distension started 2 weeks before presentation and increased gradually. Clinically, she was well but found to have a large, smooth, and nontender abdominal swelling occupying most of his upper abdomen. Her investigations revealed a normal complete blood cell count, amylase, blood urea nitrogen, and creatinine. CT scan of the abdomen showed a large cystic swelling involving most of the abdomen and measuring about 12 cm in diameter. The patient underwent exploration laparotomy, which revealed a large cystic swelling pushing the intestines downward and to the left side. The swelling was dissected and found to be arising from the head and body of the pancreas. Aspiration of the fluid in the cyst revealed an amylase level >5000 IU/mL. The cyst could not be separated from the pancreas and was drained via a Roux-en-Y cystojejunostomy. A biopsy taken from the cyst wall showed a cyst lined by cuboidal epithelium with mild inflammatory cell infiltrate. Postoperatively, she did well and was discharged home 2 weeks postoperatively.

DISCUSSION

Pancreatic cysts are commonly seen in adults. In the pediatric age group, pancreatic cysts are extremely rare and in general are classified into 6 types: congenital, retention, duplication, pseudocysts, neoplastic, and parasitic cysts ⁽⁷⁾. Among these pancreatic pseudocysts, whether posttraumatic or postinflammatory, following acute pancreatitis are the most common. True congenital pancreatic cysts, however, are extremely rare. Clinically and radiologically, it is difficult to differentiate between these types. This may be also difficult pathologically for the first 3 types, which are also called true cysts. Congenital, retention, and duplication cysts are true developmental cysts and are lined by true epithelium. This is in contrast to the pseudopancreatic cyst, which does not have an epithelial lining.

The site of origin of congenital pancreatic cysts is variable and the majority is localized in the tail or neck of the pancreas (62%), whereas localization in the head of the pancreas was reported in 32% of cases ⁽²⁾. In both of our patients, the cysts were related to the head and body of the pancreas. Congenital pancreatic cysts originating in the neck and tail of the pancreas are often confused with duplication cyst of the stomach and pancreatic pseudocysts, whereas those originating in the head of the pancreas are often confused with choledochal cyst or duplication cyst of the duodenum.

The exact embryological origin of congenital pancreatic cyst is not known. It is believed to arise from a developmental anomaly of the pancreatic ductal system ⁽⁴⁾. Embryologically, the pancreatic ducts are replaced by permanent ones as they grow, and persistence or failure of these embryonic ducts to regress may lead to their obstruction, forming cysts that fill with fluid. In our first patient, the cyst was attached to the body of the pancreas by a stalk of tissue representing the communication to the pancreatic ductal system, whereas in our second patient, the site of attachment to the pancreas was broad, involving the head and part of the body of the pancreas. There are also reports of congenital pancreatic cyst arising from occlusion of the pancreatic duct ⁽⁸⁾. Congenital pancreatic cysts are extremely rare and generally asymptomatic, but they can attain a large size as in our 2 patients, leading to abdominal distension. They may also be symptomatic as a result of pressure on adjacent structures leading to abdominal distention, vomiting, jaundice, or pancreatitis ^(1–3). In our first patient, the cyst was asymptomatic apart from abdominal distension because of the large size of the cyst, whereas the second one had vomiting as well. The majority of patients present before the age of 2 years, and associated anomalies were found in 30% of cases. These include asphyxiating thoracic dysplasia (Jeune syndrome), short-limb dwarfism, polydactaly, von Hippel-Lindau disease, Beckwith-Wiedemann syndrome, hemihypertrophy, renal tubular ectasia, anorectal malformation, and polycystic kidneys ^(2,3,5).

Modern imaging techniques usually show a well-defined unilocular cyst; however, even with the combined use of laboratory data, clinical features, and diagnostic imaging, it may be difficult to accurately differentiate congenital pancreatic cyst from other nearby cystic lesions of the abdomen. This is especially true if they are large. Pathologically, the cysts in both of our patients were lined by cuboidal epithelium and in the first one there was pancreatic tissue in the wall of the cyst. These cysts also show a high amylase level in the fluid content as in our second patient.

The treatment of congenital pancreatic cyst is surgical. The type of surgical treatment depends on the site and size of the cyst. Total excision is the treatment of choice. This is usually feasible for those cysts located in the body and tail, which may necessitate distal pancreatectomy. Cysts located in the head of the pancreas are difficult to excise totally and better managed via internal drainage either cystoduodenostomy or Roux-en-Y cystojejunostomy ^(1,5,6).

In conclusion, although rare, congenital pancreatic cyst should be considered in the differential diagnosis of abdominal cystic masses in infants and children. Once diagnosed, the treatment is surgical. Total excision is the treatment of choice, but if this is not feasible, internal drainage in the form of cystoduodenostomy or a Roux-in Y cystojejunostomy should be done.