Ectopic Pancreas at the Ampulla Diagnosed With Endoscopic Snare Papillectomy: A Case Report

Abstract

Ectopic pancreas, also known as heterotopic pancreas, is a rare condition in which the pancreatic tissue is found outside its usual location in the gastrointestinal (GI) tract. It is commonly asymptomatic and benign, and is often discovered incidentally during routine imaging, endoscopy, surgery, or autopsy. However, complications can arise, such as inflammation, bleeding, obstruction, or even malignant transformation, necessitating surgical intervention in some cases. Ectopic pancreas at the ampulla of Vater (EPAV) is an extremely rare condition and a diagnostic and therapeutic nightmare. Most cases have been diagnosed through invasive surgery due to concerns for malignancy, which carries significant morbidity and mortality. In our case, endoscopic snare papillectomy (ESP) was employed to establish a diagnosis. Thus far, only one other case has been reported in which ESP was used to diagnose and resect a pancreatic heterotopia at the ampulla.

Introduction

Ectopic pancreas, also known as heterotopic pancreas or pancreatic rest, refers to the presence of pancreatic tissue outside its standard anatomical location, without vascular or anatomical continuity with the primary pancreas.^1-5 Ectopic pancreas is most commonly found in the stomach, duodenum, and jejunum.^1,6 Sporadic cases involving the esophagus, spleen, bile ducts, and gallbladder have also been reported. Ectopic pancreas at the ampulla of Vater (EPAV) is exceedingly rare, often raising concerns for ampullary cancer. ¹ Since ampullary masses are managed surgically, ampullary mimics, such as EPAV predispose patients to significant perioperative morbidity and mortality.

In a detailed review of the literature from 1940 to 2021, Vyawahare and Musthyla ¹ found 44 cases of EPAV, of which 42 (95%) were diagnosed surgically via pancreaticoduodenectomy or transduodenal ampullectomy. Endoscopic snare papillectomy (ESP) is a novel and minimally invasive procedure that aids in en bloc resection and the diagnosis of ampullary masses.^1,7-9 Herein, we describe an exceedingly rare case of EPAV diagnosed via en bloc resection of the ampulla with ESP. To our knowledge, this is the second reported case in the literature. ¹

Case Presentation

A 78-year-old female with a history of coronary artery disease, hypertension, and ovarian cyst status post cystectomy (2 years prior) presented to the emergency room (ER) complaining of acute-onset abdominal pain and emesis. The patient was recently admitted to our hospital for ischemic stroke and was discharged earlier in the week to a rehabilitation facility for medical optimization. The abdominal pain was described as diffuse in nature, constant, and rated as 8/10 in intensity. The pain occasionally radiated to the lower back, and was associated with constipation and nausea. Prior to the ER visit, the patient experienced one episode of bilious emesis but without frank blood. She denied fever, chest pain, dyspnea, palpitations, acid reflux, acute dysphagia, mucus in the stool, diarrhea, melena, hematochezia, dysuria, or gross hematuria.

In the ER, the patient appeared in mild distress due to pain and nausea. She was afebrile and saturated well on room air. The blood pressure was elevated (172/91 mmHg), with tachycardia (114 beats per minute). A focused physical examination revealed a soft, obese abdomen that was tender on light palpation. The patient exhibited voluntary guarding on deep palpation but without rigidity or rebound tenderness. Murphy’s sign was positive, and the patient had hypoactive bowel sounds in all quadrants. There was no flank ecchymosis, icteric sclera, or jaundice. Rainbow laboratory values were significant for hypokalemia (potassium, 3.1 mEq/L), transaminitis (alkaline phosphatase, 341 unit/L; aspartate aminotransferase [AST], 338 unit/L; alanine transaminase [ALT], 487 unit/L), hyperbilirubinemia (total bilirubin, 3.7 mg/dL), and mild leukocytosis (white blood cell count, 11.2 × 10³/mm³). Lactic acid, serum lipase level, and troponin levels were unremarkable. An electrocardiogram (ECG) showed normal sinus rhythm with no acute ischemic changes. Chest X-ray was normal and abdominal X-ray revealed fecal stasis with no evidence of bowel perforation.

The patient was administered a bolus of lactated ringer solution, a 0.5 mg dose of hydromorphone intravenously (IV), and 80 mg of pantoprazole. A contrast-enhanced computed tomography (CECT) of the abdomen and pelvis showed findings suggestive of acute calculous cholecystitis, mild thickening of the distal esophagus, mild gastric dilatation, small hiatal hernia, and a 1.1 × 1.3 × 2.3 cm nodular lesion at the duodenal papilla. A nasogastric tube (NGT) was inserted and connected to intermittent suction for gastric decompression. Ultrasound of the abdomen confirmed the acute calculous cholecystitis along with a dilated common bile duct. Tumor markers, including alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and cancer antigen 19-9 (CA 19-9), were within the normal ranges.

The patient was admitted for acute calculous cholecystitis and duodenal papillary stenosis. She was started on piperacillin-tazobactam 3.375 g IV, Q8H, and continued on analgesics and anti-emetics for symptomatic treatment. Esophagogastroduodenoscopy (EGD) showed a 2-cm hiatal hernia with no gross lesions in the stomach, duodenal bulb, or second part of the duodenum. The endoscopic ultrasound (EUS) revealed an oval intramural (subepithelial) lesion in the ampulla, which was concerning for malignancy (Figure 1). The lesion was hypoechoic and measured 24.2 and 12.7 mm. There was no evidence of significant pathology in the pancreas, common bile duct, or the liver.

Figure 1.

EUS image showing a hypoechoic and oval intramural lesion in the ampulla measuring 24.2 and 12.7 mm.

A follow-up endoscopic retrograde cholangiopancreatography (ERCP) showed a major papilla bulging with an ampullary lesion (Figure 2). The ampulla was injected to attain a successful lift, and snare papillectomy of the ampulla was performed. The biliary tree was swept, and nothing was found. One plastic stent was placed in the ventral pancreatic duct, and one covered metal stent was placed in the common bile duct. The pathology of the ampullary lesion showed benign fragments of the ampulla/duodenum with prominent pancreatic tissue, consistent with ectopic pancreas at the ampulla (Figure 3). A biopsy of the residual ampullary tissue revealed a benign fragment of the duodenal mucosa. The patient underwent laparoscopic cholecystectomy on day 8 of admission and was discharged on postoperative day 4 without any complications. After 3 months, the biliary stents were removed, and there was no evidence of additional lesions or recurrence.

Figure 2.

Endoscopic image showing a bulging lesion at the level of the major papilla. The second image shows the resected subepithelial lesion.

Figure 3.

Histology slide showing pancreatic tissue with ducts and acini, consistent with ectopic pancreas at the ampulla.

Discussion

Ectopic pancreas is characterized by pancreatic tissue that does not exhibit vascular or anatomical connectivity with the typical pancreatic body. This condition is rare with an incidence of 0.2% during laparotomy ⁵ and 0.5% to 13.7% on autopsy. ⁸ Ectopic pancreatic tissue can occur in any part of the gastrointestinal (GI) tract, including the stomach, duodenum, jejunum, gallbladder, common bile duct, spleen, and ampulla of Vater.^1,2,10 Despite the use of advanced diagnostic tools, the preoperative diagnosis of pancreatic heterotopia at the ampulla remains challenging. ¹ Herein, we report a second case of ampullary ectopic pancreas that was diagnosed and treated with ESP sparing the patient the perioperative morbidity associated with surgery.

Although most pancreatic rests are small and asymptomatic, some may manifest as vaguely localized abdominal pain.^2,11-13 Depending on the size and the location of the ectopic tissue, some patients may present with obstructive symptoms, such as early satiety, nausea, vomiting, bloating, and weight loss.^2,11 In some cases, ectopic pancreatic tissue can obstruct the flow of pancreatic juices resulting in recurrent pancreatitis, chronic pancreatitis, and pancreatic pseudocysts. ¹ Inflammation caused by the pancreatic enzymes can also irritate and weaken the duodenal lining causing ulcers, GI bleeding, and subsequent anemia.^11,14 In rarer cases, pancreatic rests can become malignant, resulting in ductal adenocarcinoma, pancreatic intraepithelial neoplasia, acinar cell carcinoma, papillary neoplasms, or insulinomas.^5,12,13 In our case, the patient’s GI symptoms were most likely due to the calculous acute cholecystitis and duodenal papillary stenosis in the setting of an ampullary mass.

Given its rarity, indolent course, and heterogeneous presentation, ectopic pancreas is often an incidental diagnosis during routine imaging, laparotomy, endoscopy, or autopsy. However, a definitive diagnosis can only be made based on histopathology.^1,5 Triage blood tests can be significant for acute blood loss anemia, elevated pancreatic enzymes, or CA 19-9.^15,16 On endoscopy, ectopic pancreatic tissue appears as a solid subepithelial or submucosal lesion, with a normal-appearing overlying mucosa.^10,17 Central umbilication is a unique feature of these lesions and represents the opening of the duct. ⁵ Endoscopic biopsies have limited utility in the evaluation of pancreatic heterotopia due to the subepithelial nature of the lesions.

Endoscopic ultrasound is a novel tool for the evaluation and diagnosis of subepithelial lesions within the GI tract.^10,18 It enables high-resolution imaging and accurate assessment of lesions, especially those less than 1 cm in diameter. On EUS, ectopic pancreas appears as hypoechoic or anechoic lesions, primarily situated in the submucosal layer.^10,17 However, these findings are often non-specific and require surgical or endoscopic resection for a more definitive diagnosis. In our case, the patient’s advanced age, signs and symptoms, and duodenal papillary stenosis on imaging prompted endoscopic intervention via the ESP.

The treatment of ectopic pancreas is dictated by signs and symptoms and the potential for complications. Given its tendency to mimic periampullary and ampullary neoplastic lesions, pancreatic rest at the ampulla is typically surgically resected for histopathological examination. Surgery ensures a complete removal of the aberrant tissue and allows for the management of associated complications, such as bowel obstruction. ¹⁹ Endoscopic snare papillectomy is a minimally invasive procedure used for the treatment of benign ampullary tumors, including adenomas and early-stage adenocarcinomas.^1,7,8 This technique involves the endoscopic resection of lesions located on the ampulla of Vater using a snare device, allowing for en bloc or piecemeal removal of the tumor.^1,8 Studies have shown that ESP is a viable alternative to surgery and endoscopic mucosal resection, with high rates of complete resection and low recurrence rates. ⁷ Complications, such as hemorrhage, pancreatitis, and perforation can occur but are generally manageable.^1,8

Conclusion

Ectopic pancreas is a rare condition in which pancreatic tissue is found outside its usual location within the GI tract. Most cases of pancreatic heterotopia are diagnosed incidentally on routine imaging, endoscopy, surgery, or autopsy. Ectopic pancreas at the ampulla of Vater is an exceedingly rare condition, often warranting surgery for definitive diagnosis. Ectopic pancreas at the ampulla of Vater can mimic ampullary and periampullary neoplasms, and histopathology provides a more definitive diagnosis. Endoscopic snare papillectomy is a minimally invasive intervention for the diagnosis and resection of subepithelial lesions, such as pancreatic rests. This novel intervention spares the patient from perioperative morbidity and mortality associated with surgery. Herein, we report the second case of EPAV diagnosed via en bloc resection of the ampulla with ESP.