The pocket of doom - carcinoma of the duodenal diverticulum

INTRODUCTION

Duodenal diverticular carcinoma is an extremely rare malignancy that arises within a diverticulum of the duodenum, which constitutes an outpouching of the duodenal wall. The clinical presentations are often nonspecific and may overlap with symptoms of other gastrointestinal disorders, typically characterised by vague abdominal discomfort or pain, gastrointestinal bleeding, and obstructive symptoms.^[1] These aspects can result in a delayed diagnosis, with such symptoms sometimes being erroneously attributed to a duodenal ulcer. The identification of carcinoma within a diverticulum poses significant therapeutic challenges due to its atypical anatomical location and clinicians' limited experience in managing such cases. We present two cases observed over a three-month period, in which both patients had duodenal diverticula that underwent malignant transformation. The first case was accurately diagnosed through contrast-enhanced computed tomography (CECT) as duodenal diverticular cancer. Conversely, the second case was misdiagnosed as mass-forming pancreatitis, primarily due to the rarity of this pathology and the nonspecific nature of the associated symptoms.

CASE SERIES

CASE-1

A 68-year-old male presented with epigastric pain and a single episode each of hematemesis and melena for the past day. He had a previous history of intermittent episodes of diffuse abdominal pain that had persisted for many years. Routine blood tests, including liver function tests, were within the reference range, except for a decreased haemoglobin level of 10.2 g/dL. The carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9) were raised. The chest X-ray revealed mild emphysematous changes, with no evidence of a mass lesion or nodules. Abdominal sonography showed a well-defined, round hypoechoic mass abutting the head of the pancreas with a few heterogeneously hypoechoic lesions in the liver. For further workup, a triple-phase CECT scan was performed, which showed a well-defined, round, enhancing mass measuring 5.7 x 4.0 x 3.1 cm in the C loop, abutting the medial wall of the second segment of the duodenum, with evidence of luminal communication with it. The mass contained air at its centre and showed loss of fat planes with the head of the pancreas. Furthermore, a few arterially peripherally enhancing lesions were identified in both lobes of the liver, exhibiting washout during the portal venous and hepatic venous phases, suggestive of metastasis [Figure 1]. The biliary system and the pancreatic duct were not dilated. No significant abdominal lymphadenopathy or ascites was observed. Based on the computed tomography (CT) findings and in the absence of any other known primary tumour, a diagnosis of carcinoma of the duodenal diverticulum with hepatic metastasis was proposed. The second-closest differential diagnosis for duodenal validates the CT diagnosis, which revealed an ulcerated mass-filled duodenal diverticulum located at the junction of the first and second segments of the duodenum. An endoscopy-guided biopsy was obtained from the site of ulceration, and histopathological examination confirmed the presence of moderately differentiated adenocarcinoma. The surgery was deferred in view of hepatic metastasis. The patient underwent chemotherapy but succumbed to his illness within a month of diagnosis.

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Figure 1:

Case 1 - Contrast-enhanced computed tomography (CECT) (a) Axial image shows first part of the duodenum (star) and metastasis in segment VI of the liver (arrowheads), (b) Axial image shows nodular enhancing mass (thick arrow) in the duodenal diverticulum communicating with the duodenal lumen (thin arrow), (c) Axial image shows second and third segments of the duodenum (stars), (d) Coronal image shows mass in duodenal diverticulum (thick arrow) and duodenal lumen (stars), (e) Oblique image shows duodenal diverticular mass (thick arrow), duodenal lumen (stars), hepatic metastasis (arrowhead) and communication of diverticulum with the duodenal lumen (thin arrow).

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CASE-2

A comparable case involved a 66-year-old male who presented with complaints of abdominal pain, jaundice and notable weight loss over the past six months. He had a history of repeated episodes of pancreatitis attributable to alcohol. The blood investigations showed severe anaemia with a haemoglobin level of 7.4 g%. The liver transaminase, total bilirubin, direct bilirubin, and amylase and lipase values were raised. CEA and CA 19-9 levels were also elevated in this case. An abdominal ultrasound revealed a heterogeneous, hypoechoic mass-like thickening of the duodenum abutting the pancreatic head. CECT abdomen [Figure 2a-d] showed an enhancing mass along the medial wall of the second part of the duodenum, infiltrating into the pancreatic head. It contained a few air foci. It was compressing the lower end of the common bile duct and the pancreatic duct, causing a complete and abrupt cutoff with subsequent upstream dilatation of the biliary system and the pancreatic duct. The pancreatic neck, body and tail were normal. A few small lymph nodes, averaging 4-5mm in size, were observed adjacent to this mass. There was no ascites. 18-FDG positron emission tomography (PET) [Figure 2e] showed increased tracer uptake in the mass. Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) [Figures 2f-k] were interpreted as showing a heterogeneously hypoenhancing mass located in the pancreatic head, with adjacent thickening of the duodenum in the D2 segment. It was showing patchy areas of diffusion restriction. The intrahepatic as well as extrahepatic biliary system was dilated. The pancreatic duct was also dilated. Inflammatory changes in the form of fat stranding surrounding the mass and the gall bladder were also seen. Based on the patient's medical history, which included pancreatitis, elevated serum amylase and lipase levels, and imaging findings, a diagnosis of mass-forming pancreatitis in the pancreatic head was initially made. However, an upper gastrointestinal endoscopy revealed an asymmetric, fungating growth within a duodenal diverticulum. Histopathological examination of the specimen confirmed the presence of duodenal adenocarcinoma. A retrospective analysis of the CECT images indicated a suspicious connection between the mass and the duodenal lumen [Figure 2a], thin arrow. The patient refused surgery and left against medical advice. On a 2-month telephonic follow-up, the patient had succumbed to death with a plausible cause attributed to cachexia and a severe anaemic profile of the patient that might have led to heart failure.

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Figure 2:

Case 2 - CECT (a) Coronal image shows an enhancing mass (thick arrow) in the duodenal diverticulum with communication with the duodenal lumen (thin arrow). The adjacent duodenal loop is well seen (stars), (b) Sagittal image shows diverticular mass (thick arrow), (c) Oblique image shows diverticular mass (thick arrow), duodenal lumen (star) and communication of duodenal diverticular mass with duodenal lumen (thin arrow), (d) Axial image shows diverticular mass (thick arrow), (e) Axial image 18-FDG Positron emission tomography (PET) scan shows increased tracer uptake within the duodenal mass (arrow). Magnetic resonance imaging (MRI), (f) Axial T2-weighted image shows duodenal diverticular mass (arrow), (g) Coronal T2-weighted image show duodenal mass (arrow) and duodenal lumen (star), (h) Magnetic resonance cholangiopancreatography (MRCP) image shows dilated biliary system and main pancreatic duct with abrupt cut off by the mass (arrow) and duodenal lumen (star), (i) Post-contrast T1-weighted fat- saturated axial image shows enhancement of the diverticular mass (arrow), (j) Diffusion weighted (arrow) and (k) Corresponding ADC image shows restricted diffusion within the duodenal diverticular mass (arrow).

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Informed consent was obtained from the patients’ attendants before reporting the cases. The case reports have been prepared in accordance with the CARE checklist and Equator guidelines.

DISCUSSION

The duodenum is the second most common site of gastrointestinal diverticula, after the colon.^[2,3] The reported prevalence of duodenal diverticula ranges from 5% to 32%.^[4] The most common site of a duodenal diverticulum is the second part (62%), followed by the third (30%) and fourth (8%) parts.^[5] Periampullary diverticula are those that arise within a 2 to 3 cm radius of the major papilla.^[3] Duodenal diverticula can be classified as congenital or acquired. Congenital diverticula are rare, contain all layers of the duodenal wall, and may be classified as intraluminal or extraluminal. Acquired diverticula are more common and can be classified into two subtypes: primary and secondary. The primary subtype arises from the protrusion of the duodenal mucosa through weak points in the duodenal wall, particularly in regions adjacent to the common bile duct, pancreatic duct, or vascular structures. In contrast, the secondary subtype results from an outpouching of the duodenal wall adjacent to a healing duodenal ulcer.^[5,6] These diverticula may make cannulation of the common bile duct difficult during an endoscopic retrograde cholangiopancreatography. Duodenal diverticula can be readily identified during upper gastrointestinal barium studies and are typically well visualised on CT and MRI, provided they are filled with fluid and air and are situated in the distinctive periampullary region. However, misinterpretation of a duodenal diverticulum on CT or MRI as a pancreatic tumour, metastatic lymph node, pancreatic pseudocyst, or pancreatic abscess has been reported.^[2,6] A completely fluid-filled duodenal diverticulum may mimic a cystic neoplasm of the pancreatic head.^[4] Usually a silent anomaly, approximately 5% of patients with duodenal diverticula develop clinical symptoms, most commonly because of complications such as haemorrhage, acute diverticulitis, perforation, pancreatitis or choledocholithiasis.^[2,3,5] The duodenal diverticulum can present as obstructive jaundice in cases of Lemmel’s syndrome, where the diverticulum arising near the ampulla of Vater exerts mass effect upon the distal common bile duct, leading to upstream biliary dilatation.^[7] But the most dreaded complication is its sinister transformation into malignancy, predominantly adenocarcinoma.

Primary duodenal adenocarcinomas have been considered rare, reportedly accounting for only 0.3% - 0.4% of gastrointestinal cancers.^[4,8] The duodenum is also an infrequent site for metastasis, the primary tumours predominantly being melanoma, lung carcinoma, renal cell carcinoma, and seminoma.^[6] Malignant transformation of the duodenal diverticulum remains rarer. The exact etiopathogenesis remains unclear, but chronic irritation, inflammation, and stasis within the diverticulum are considered to contribute to its development. Histologically, duodenal diverticular carcinoma is predominantly classified as adenocarcinoma and exhibits similarities with other gastrointestinal malignancies. Clinical symptoms are nonspecific, often mimicking peptic ulcer disease or other benign conditions, which can lead to missed or delayed diagnosis. Imaging and endoscopic evaluations may facilitate detection by revealing features indicative of neoplastic transformation, such as asymmetrical thickening, nodular and irregular margins, and abnormal wall enhancement.

Management protocols for duodenal diverticular carcinoma are not well established due to the rare incidence of this condition. In the first case, metastatic liver lesions had precluded curative surgery. In contrast, in the second case, the patient succumbed to complications of malignancy, highlighting the aggressive course and poor prognosis associated with this condition. Surgical resection is the primary treatment modality, with the extent of the surgical intervention determined by factors such as tumour location, size, and invasiveness. Although the rarity of this condition has resulted in the absence of specific management guidelines, early detection and complete surgical excision are associated with improved outcomes. Overall, duodenal carcinoma carries a dismal prognosis, with five-year survival rates reported as less than 30%, primarily due to late presentation, advanced stage at diagnosis, and limited treatment options.^[9]

CONCLUSION

Carcinoma arising in duodenal diverticula is infrequently encountered and should be considered as a potential differential diagnosis when evaluating periampullary pathology. Misdiagnosis in such cases may result in delayed therapeutic interventions, as exemplified in our case reports. Therefore, early recognition of this condition is paramount for ensuring optimal and timely management of the patient.