ADULT ANNULAR PANCREAS: A CASE REPORT

Annular pancreas is a rare congenital abnormality, more often seen in the pediatric patient population. This abnormality results from failure of the ventral pancreatic bud during normal migration during development. Ectopic pancreatic tissue persists, encircling the duodenum. Hence, this can lead to duodenal obstruction. Despite the fact that annular pancreas is extremely rare in an adult patient population, annular pancreas deserves to be a part of a clinician’s differential diagnosis. The authors describe a 61 year old man presenting with annular pancreas. A discussion of the typical presentation, prevalence, and surgical management is included. Purpose (a): In modern medicine, annular pancreas remains a rare congenital abnormality yet it is the second most common kind of pancreatic fusion abnormality after pancreas divisum.1 Annular pancreas is more often seen in the pediatric patient population so it is an uncommon find among adults. In the adult population, it usually presents between 20 and 50 years of age. This abnormality results from failure of the ventral pancreatic bud during normal migration during development. Ectopic pancreatic tissue persists, encircling the duodenum.2 Most commonly the second portion of the duodenum is involved in 74% of cases.1 Hence, this can lead to duodenal obstruction. Only 737 reported cases of annular pancreas are found in English scientific literature.1,2 Imaging modalities often have their limitations in the management of this anomaly as well. In addition, treatment is still not entirely straightforward in adults as this condition can mimic many other conditions that have to be ruled out. Treatment is always surgical once the diagnosis of symptomatic annular pancreas is clearly formulated.1 Surgical options include duodenoduodenostomy, gastrojejunostomy with vagotomy, duodenojejunostomy, or very rarely, pancreatic resection.1,2,3 In the following case, the patient underwent a duodenoduodenostomy, which is the treatment of choice. Methods (b): A 61 year-old Caucasian male presented to an outside facility with a one month history of intermittent, postprandial right upper quadrant pain and a knot-like sensation and fullness after meals. He arrived at the facility after one week of increasing pain precipitated after eating a Reuben sandwich. Though the patient did not have a history of dyspepsia, he described a burning pain much like indigestion that had become severe and was now located in the epigastric region. He reported no nausea, vomiting, or change in bowel movements. However, he did state an increase in eructation. Laying supine aggravated the pain while belching alleviated the pain. He had no fever, chills, shortness of breath, cough or chest pain. Nevertheless, his initial lab work indicated a white count of 12,600 with left shift. He also had no jaundice and labs indicated normal liver function tests (LFTs). His past medical history included hypertension, high cholesterol, and benign prostatic hyperplasia. Past surgical history included three orthopedic surgeries. At the outside facility he received computerized tomography (CT) of the abdomen and pelvis with IV and p.o. contrast. CT revealed an annular pancreas with no free air or free fluid in the pancreas along with a moderately dilated stomach, and nondilated fluid-filled small bowel loops in the right lower quadrant potentially suggesting gastroenteritis. After transfer to our facility, he was seen in clinic and admitted. His symptoms had abated by this point and his white blood count had fallen to 9,400. Next, he was seen by a gastroenterologist. An upper gastrointestinal series unmistakably revealed moderate to severe stricture of the second part of the duodenum. Repeat CT again indicated an annular pancreas with no free air or free fluid in the pancreas along with a moderately dilated stomach, nondilated fluid-filled small bowel loops in the right lower quadrant potentially suggesting gastroenteritis along with a normal appendix. Moreover, the gastroenterologist performed an esophagogastroduodenoscopy (EGD) that denoted gastritis in the antrum, food debris in the bulb of the duodenum, and stenosis in the descending portion of the duodenum. The endoscope could not be passed distally. Furthermore, the esophagus and gastroesophageal junction had a normal appearance. Surgery was recommended. The patient’s preoperative diagnoses were annular pancreas and gastric outlet obstruction. He consented to either a duodenoduodenostomy or duodenojejunostomy for bypass of the duodenal obstruction and he understood the risks involved. The patient was taken to the operating room, placed under general anesthesia in the supine postion, and the abdomen was prepped and draped sterilely. An upper midline incision was made, adhesions present in the right upper quadrant were removed, and the gallbladder was noted to be intact. Afterward, the duodenum was kocherized and isolated. An annular pancreas was noted that was causing obstruction. The duodenum was entirely mobilized and a side-to-side duodenoduodenostomy was created. This was done by making a transverse incision in the first portion of the duodenum followed by a longitudinal incision in the distal duodenum. A single layer anastomosis was created in a running fashion. Air leaks were checked for by threading the nasogastric (NG) tube through the anastomosis and insufflating air under water immersion. No bubbling was present. Subsequently, the omentum was placed over the right upper quadrant, an On-Q pain pump was positioned in the preperitoneal area and Seprafilm was applied. Finally, the abdomen was closed. The patient tolerated the procedure well and was discharged on the fifth postoperative day. The patient made a complete recovery and was in good health at his two week follow-up visit. Results (c): Annular pancreas was first described in 1818 by Tieddman and the first surgical intervention was implemented by Vidal in 1905.1,2 Though Vasconcelos and Sadek reported only a sole annular pancreas case among 22,243 autopsies, this incidence may not be accurate since duodenal dissection is not performed customarily during autopsy. Thus, the 1.14% incidence reported by Karasaki et al. may be more correct as it based on institutional CT scans.1 Many theories have been conceived about the possible origins of annular pancreas. In 1910, Baldwin speculated that this abnormality arose from aberrant movement and the failure of atrophy of the ventral pancreatic bud. Lecco theorized that adherence of the ventral pancreas to the duodenum in place of normal migration was responsible.1,2 Verga believed that a narrow duodenum was the primary problem; the pancreas simply attempted to rectify the defect by filling the space around the duodenum.2 Most reported cases are among the pediatric population and demonstrate a female preponderance. In the pediatric population, other congenital abnormalities such as cardiac defects, intestinal atresia, biliary anomalies, tracheoesophageal fistulae, intestinal malrotation and trisomy-21 are also often present with annular pancreas.5 In the adult population, 70% of patients present with abdominal pain while 47% present with nausea and vomiting because of proximal duodenal obstruction.2 Patients may also present with asymptomatic pancreatic hyperenzymemia.3 According to an estimate, only 33% of infants and adults are symptomatic.2 Annular pancreas is a great imitator of other conditions because of its variability in presentation among the adult population. Peptic ulcer disease, acute and chronic pancreatitis, and gastroduodenal tuberculosis (if in endemic areas) have to be ruled out. It is seldom associated with obstructive jaundice or malignancy.1,2 Many options exist for imaging including CT, Magnetic resonance cholangiopancreatography (MRCP), Endoscopic retrograde cholangiopancreatography (ERCP), and endoscopic ultrasound (EUS). CT clearly delineates the ventral pancreatic ring encircling the duodenum (a complete ring is not required for diagnosis).4 In fact, 75% of annular pancreas cases have a partial ring around the duodenum.3 MRCP can show a pancreatic duct surrounding the duodenum but a dilated pancreatic ductal system is mandatory.2 ERCP can also be used to rule out other conditions but it is an invasive procedure that can be impeded by stenosis of the duodenum. ERCP can also cause or worsen acute pancreatitis.2,3 EUS can assess not only the pancreatic duct but also the parenchyma.3 Surgery is indicated in all symptomatic cases.1,2 Duodenoduodenostomy is preferred because it produces the least amount of blind loop segment.1 Gastrojejunostomy can be performed if vagotomy is also done; vagotomy prevents the risk of peptic ulcer and anastomotic ulcer by decreasing gastric acid secretion.1,2 Pancreatic resection is frequently avoided because of the risk of pancreatic or duodenal fistula, pancreatitis, and pancreatic insufficiency. Even minor pancreatic leaks after resection can result in serious inflammation and fibrosis, ultimately leading to luminal compromise of nearby structures. Resection is only employed if malignancy cannot be excluded.1 Conclusions (d): In modern medicine, physicians are frequently instructed to think of horses, not zebras when they hear hoofbeats. Despite the fact that annular pancreas is extremely rare in an adult patient population, annular pancreas deserves to be a part of a clinician’s differential when a patient presents with abdominal pain, nausea and vomiting, and other signs of gastric outlet or duodenal obstruction. Certainly, other probable conditions like peptic ulcer disease and acute and chronic pancreatitis have to excluded. CT is the imaging modality that is most frequently utilized to derive a diagnosis of annular pancreas but modalities like EUS, MRCP, and ERCP are also viable options. In symptomatic patients, treatment remains strictly surgical. Duodenoduodenostomy or duodenojejunostomy remain as the preferred bypass techniques to relieve obstruction. Gastrojejunostomy with vagotomy is another potential surgical option.