British Journal of Radiology (2005) 78, 562-564
© 2005 British Institute of Radiology
doi: 10.1259/bjr/52543195
Duodenal diverticulum mimicking a cystic pancreatic neoplasm
A Hariri, BSc1,
S S Siegelman, MD1 and
R H Hruban, MD2
Departments of 1 Radiology and 2 Pathology, The Johns Hopkins Hospital, Baltimore, Maryland, USA
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Abstract
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Duodenal diverticula occur very commonly, with a prevalence as high as 22%. They are most frequently located in the second or third portions of the duodenum, and by nature of their proximity to the head of the pancreas, can be mistaken for cystic pancreatic neoplasms by diagnostic imaging. Patients with presumed cystic neoplasms of the pancreas often receive pancreaticoduodenectomies, which at high volume medical centres carry mortality and morbidity rates of 2–4% and 29–44%, respectively. Although most duodenal diverticula are recognized in single or repeat CT scans by the presence of air or contrast medium within the diverticula, we present a case in which serial CTs failed to yield any clue to the diverticulum's true nature and pancreaticoduodenectomy was performed. For presumed cystic lesions adjacent to the duodenum, barium studies, endoscopy, and/or endoscopic ultrasound-guided aspiration should therefore be pursued in addition to all available CT evidence prior to surgery.
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Introduction
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Diverticula of the duodenum occur very commonly. Autopsy studies have revealed their prevalence to be as high as 22% [1]. Although they can cause diverticulitis, perforation, obstruction, or haemorrhage, the majority of duodenal diverticula are asymptomatic [2].
Most duodenal diverticula occur in the second or third portions of the duodenum, within 2.0 cm of the ampulla of Vater [3]. Owing to their proximity to the head of the pancreas, fluid-filled duodenal diverticula can be confused with cystic pancreatic neoplasms by diagnostic imaging [1]. We report such a case in which the patient underwent a Whipple resection for a putative cystic pancreatic neoplasm. Serial CT scans over 3 years failed to yield any clue to the diverticulum's true nature.
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Case report
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A 77-year-old woman with an ascending aortic aneurysm presented with a 2.0 cm cystic mass closely associated with the pancreas. The mass was identified by CT and presumed to be a cystic pancreatic lesion. Her thoracic aortic aneurysm, 5.4 cm in diameter, had been diagnosed by echocardiography. The decision was made to follow her with serial CT scans. During the first of those CT scans, the cystic lesion within the head of the pancreas was detected.
CT scans were obtained approximately every 6 months for 3 years (Figure 1
). There was a perception that the mass had increased in size from 2 cm to 4 cm. The cystic lesion never filled with orally administered contrast medium. At no point was gas seen within the lesion. The diagnosis of duodenal diverticulum was never considered. The patient was asymptomatic. Her abdominal examination was benign and she was not jaundiced. Laboratory findings were normal. On the basis of an enlarging mass presumed to be in the head of the pancreas, the patient received a pylorus preserving pancreaticoduodenectomy. At pathological examination, the lesion proved to be a duodenal diverticulum embedded in the head of the pancreas (Figure 2).
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Figure 1. Duodenal diverticulum embedded in pancreatic head of a 77-year-old woman. Axial enhanced CT scan of abdomen shows a multiloculated cystic mass within the head of the pancreas, measuring 4.1 cm by 3.1 cm. The lesion is thin-walled, does not fill with oral contrast medium, and contains no gaseous densities.
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Figure 2. Gross pathology of the lesion demonstrating: (a) duodenal diverticulum embedded in the head of the pancreas; (b) diverticular orifice, which possesses a very small diameter relative to the diverticulum; (c) duodenum with multiple additional diverticulae.
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Discussion
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While the majority of cystic lesions of the pancreas are post-inflammatory pseudocysts, a wide spectrum of other cystic pancreatic lesions with varying prognoses are regularly encountered during imaging [4, 5]. Cystic pancreatic neoplasms occur in 0.7% of people and range from benign to malignant in nature. Owing to the difficulty of ascertaining the malignant potential of a cystic pancreatic lesion, some have advised surgery in patients who have radiological evidence of increasing cyst size, are symptomatic, or are fit, older patients (60% of cystic lesions in patients over 70 years are malignant) [6]. Clinical history, biopsy, and fluid aspiration can aid in narrowing the differential diagnoses of lesions. However, challenges associated with the pre-operative diagnosis and management of cystic pancreatic lesions have prompted others to advocate resection of all cystic lesions other than pseudocysts [5].
In the case presented, examination of the specimen following surgery revealed a benign lesion, a duodenal diverticulum. Pancreaticoduodenectomy, or Whipple resection, for a condition which proves to be benign is not unusual. Surveys from high-volume medical centres have shown that 9.2% of pancreaticoduodenectomies are performed for benign disorders where there is pre-operative suspicion of malignancy [7]. This is not insignificant given a mortality rate of 2–4%, and morbidity rate ranging from 29–44% depending on whether a standard or radical pancreaticoduodenectomy is performed [8]. Proper diagnosis and recognition of benign entities that could masquerade as cystic pancreatic neoplasms is therefore of paramount importance.
Our case report demonstrates one such entity: a duodenal diverticulum embedded in the head of the pancreas. A recent Finnish study of 1735 patients who had an indication for endoscopic retrograde cholangiopancreatography identified duodenal diverticula in 123 of them, with an equal male to female ratio [9]. After the colon, the duodenum is the second most common location for diverticulae; most are actually pseudodiverticula, resulting from increased intraluminal pressure causing herniation of the mucosa through the muscularis at weak points in the wall, usually where mesenteric vessels enter [2].
In the first study of duodenal diverticula mimicking cystic pancreatic neoplasms, Macari et al [1] looked at seven patients with diverticula ranging in size from 10 cm to 25 cm. MRI or CT was used to identify the lesions. Owing to their small size and benign appearance by imaging, clinical observation was deemed appropriate for six of the seven lesions. The seventh patient, whose CT demonstrated bile and pancreatic duct dilatation, received a pancreaticoduodenectomy. Notably, all diverticula – including the one for which surgery was performed – were correctly identified in imaging studies. Four were identified by the presence of gas in follow-up CT scans, one by gas and another by gas and barium in previous CT scans, and the last in a follow-up upper gastrointestinal barium exam. Even retrospectively, with the knowledge that all seven of these lesions were duodenal diverticula, Macari et al [1] found that with only a single examination, and without the benefit of past or future scans, it was not possible to definitively identify four of the diverticula.
The duodenal diverticulum in this case report presented a diagnostic dilemma. It was only 4.1 cm by 3.1 cm at its maximum size, small enough that both surgery and continued observation were considered plausible options. Despite serial CT scans performed every 6 months for 3 years, at no point did the diverticulum fill with oral contrast or gas. This was likely due to the small diameter of the diverticular orifice (Figure 2b
). Although duodenal diverticula can be symptomatic – most often causing abdominal pain or bleeding [10] – the majority are asymptomatic, as in our case. While 38% of patients with cystic pancreatic neoplasms present with pain and 8% with nausea or fullness, the majority of these patients (51%) are also asymptomatic [6]. Therefore, history and physical exam did not yield a clue to the nature our patient's mass. Fluid aspiration would have been non-specific, as it is impossible to distinguish duodenal contaminants from the true composition of a presumed cyst. Nonetheless, endoscopic ultrasound-guided fluid aspiration can be useful in evaluating cystic pancreatic masses, as aspiration of mucin and mucinous fluid suggests a neoplasm (intraductal papillary mucin producing neoplasm or mucinous cystic neoplasm) that may require surgical excision.
Clinicians should therefore be aware that although most duodenal diverticula will be observed to fill with oral contrast medium or gas upon repeat imaging, there are exceptions to this rule. In addition, a diverticulum may appear to increase in size, further raising questions of malignancy. Owing to the morbidity and mortality associated with pancreaticoduodenectomy, careful review of prior imaging studies should always be performed. If previous studies do not demonstrate gas or contrast medium within a cystic lesion adjacent to the duodenum, barium studies, endoscopy, and/or endoscopic ultrasound-guided fluid aspiration should be pursued prior to surgery.
Received for publication October 22, 2004.
Revision received December 19, 2004.
Accepted for publication January 31, 2005.
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References
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Abstract
Introduction
