British Journal of Radiology 75 (2002),78-84 © 2002 The British Institute of Radiology
CT of duodenal pathology
R Zissin, MD
1
A Osadchy, MD
1
G Gayer, MD
2 and
M Shapiro-Feinberg, MD
1
1Department of Diagnostic Imaging, Sapir Medical Center, Kfar Saba 44281 and 2Department of Diagnostic Imaging, Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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Abstract
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This pictorial review presents the CT findings in different pathological entities of the duodenum. The aim of the article is to demonstrate the contribution of a common imaging modality, i.e. abdominal CT, in the diagnosis of various duodenal disorders.
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Introduction
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The current widespread use of abdominal CT has resulted in the detection, sometimes as an incidental finding, of various duodenal abnormalities. CT provides a comprehensive view of any possible gastrointestinal tract (GIT) pathology as it permits demonstration of the lumen, wall and adjacent extramural structures. This review illustrates the CT features of a variety of pathological conditions affecting the duodenum.
CT images were obtained on a non-helical scanner (Elscint 2400 Elite; Elscint, Haifa, Israel) following administration of both oral and iv contrast medium. The latter was manually injected, therefore the enhancement shown in the following images is variable and some images are not dynamically enhanced. Increasing use of multislice CT should give improved anatomical detail.
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Anatomy
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The duodenum, a retroperitoneal structure (except for the duodenal bulb) lying within the anterior pararenal space, is a 30 cm C-loop segment of the GIT that extends in the retroperitoneum from the pylorus (to the right of the midline) to the ligament of Treitz (to the left of the midline).
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Congenital anomalies
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Malrotation
Midgut malrotation, a spectrum of congenital positional anomalies of the intestine, results from inadequate rotation of the primitive intestinal loop around the axis of the superior mesenteric artery (SMA) during fetal life. The classification of malrotation relates to the embryological stage of development. It may occur as an isolated congenital anomaly in patients with situs solitus or as a component of visceral situs anomalies, including situs inversus and situs ambiguus. Inferior vena cava anomalies, polysplenia, short pancreas and pre-duodenal portal vein may be associated findings [1].
Type Ia malrotation is defined as non-rotation of the colon and the duodenum. This is the most common type of intestinal malrotation. It is usually asymptomatic and often found incidentally on imaging studies or at surgery or autopsy. Complications are rare and tend to be of the benign, obstructive type. The characteristic CT findings of uncomplicated intestinal non-rotation include superior mesenteric vein inversion, aplasia or hypoplasia of the uncinate process of the pancreas, a right-sided small bowel, a left-sided colon and absence of the horizontal duodenum (Figure 1
). However, inversion of the superior mesenteric vessels is not specific for intestinal malrotation. Type IIc intestinal malrotation is defined as reversed rotation of the duodenum only. The duodenum passes anterior to the SMA, and the large bowel passes in front of both of them, features that are clearly demonstrated on CT (Figure 2).
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Figure 1. Non-rotation type intestinal malrotation. Contrast enhanced CT at the level of the pancreatic head showing right-sided contrast-filled small bowel loops (arrows), left-sided colon (c) and absence of the horizontal duodenum. Note an abnormal relationship of the superior mesenteric vessels (open arrow) as well as aplasia of the uncinate process of the pancreas (arrowhead).
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Figure 2. Type IIc intestinal malrotation in a 49-year-old man with chronic abdominal pain. The horizontal duodenum passes anteriorly to the vertically oriented superior mesenteric vessels (arrowhead), with a normally located colon (c) in front of it. (Reprinted, with permission, from Abdom Imaging [1]).
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Duplication
Duodenal duplication or duplication cyst is a rare congenital anomaly, accounting for 5.5–7% of all GIT duplications. It has a 1–2 mm thick wall of functional mucosa and a muscular layer of smooth muscle, which in most cases connects with the muscular layer of the normal intestinal wall. The cyst does not usually communicate with the lumen [2]. Duplication cyst is often found along the mesenteric side of the first and second portions of the duodenum, presenting as a cystic lesion (Figure 3), and may contain mobile enteroliths within the fluid content. The differential diagnosis of duodenal duplication includes a choledochocele, a pancreatic pseudocyst and intraluminal diverticulum [3]. Ultrasound, especially endoscopic, is helpful in establishing the correct diagnosis of a duodenal duplication by demonstrating a pathognomonic multilayered wall or the presence of peristaltic activity of the cyst.
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Figure 3. Contrast enhanced CT shows a cystic mass in the medial portion of the descending duodenum (arrow), which proved to be a duplication cyst.
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Diverticulum
Duodenal diverticulum, either congenital or acquired, is a frequent incidental finding and is found in 6% of upper GIT barium studies [4]. It is most often located in the mesenteric border of the descending duodenum near the ampulla of Vater and pancreatic head. The diverticulum is seen on CT as an air-filled pocket or as an air–fluid/orally digested contrast material level that may contain debris, medial to the duodenal loop (Figure 4) [4]. Infection, perforation, haemorrhage, pancreatitis or biliary obstruction may rarely complicate duodenal diverticulum and duodenal duplication.
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Figure 4. Duodenal diverticulum. A rounded collection of orally digested contrast medium with an air–fluid level (D.D) is connected by a thin neck (small arrow) to the medial aspect of the duodenal loop.
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Peptic disease and its complications
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Peptic ulceration is usually diagnosed by endoscopy or a barium upper GIT series [5, 6]. However, abdominal CT performed for non-specific upper abdominal complaints may disclose marked thickening (Figure 5) and even an ulcer crater (Figure 6) within the duodenal wall or pneumoperitoneum resulting from perforation of the ulcer (Figure 5) [7]. Duodenal wall thickening is a non-specific finding and detailed clinical information is needed to establish a correct radiological diagnosis. For example, duodenal mural thickening may be seen in Zollinger–Ellison syndrome, in which high resolution arterial CT may be required to demonstrate the non-beta islet cell tumour of the pancreas.
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Figure 5. Contrast enhanced CT of a 77-year-old man with acute abdomen shows free peritoneal fluid and air (small arrows) and irregular mural thickening of the proximal duodenum (arrow) owing to perforated ulcer disease.
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Figure 6. Marked asymmetric mural thickening of the medial aspect of the proximal duodenum with an ulcer crater (arrow) in a patient with peptic ulceration.
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Inflammatory disease
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Crohn's disease
Aphtoid ulcers in the upper GIT mucosa occur in 20–40% of patients with established disease in the ileum and/or colon, but imaging findings are seen in only 4% of patients [6, 8]. CT features range from non-specific thickening of the valvulae conniventes to a tubular stricture in more advanced disease (Figure 7).
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Figure 7. Contrast enhanced CT of a 52-year-old man with Crohn's disease shows mural thickening ofthe horizontal portion of the duodenum, with a tubular stricture causing a pre-stenotic dilatation. Note the slightly enlarged mesenteric nodes.
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Extrinsic inflammatory diseases affecting the duodenum
As the duodenum is in close proximity to the pancreatic head, the adjacent phlegmonous exudate in acute pancreatitis may cause oedema and mural thickening of the duodenal loop. Similar findings may also be seen in acute cholecystitis (Figure 8).
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Figure 8. Contrast enhanced CT of a 38-year-old woman with acute cholecystitis shows a distended gall bladder with marked mural thickening and thickening of the adjacent duodenum wall (arrows).
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Neoplasms
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Duodenal tumours account for about one-third of small bowel neoplasms, which represent only 5–6% of all GIT neoplasia [9]. Benign tumours include adenoma, adenomatous polyp, lipoma and leiomyoma. The only criterion used to predict a benign lesion is the intraluminal location of a mass [9]. Owing to its characteristic fat density, lipoma is the only intraluminal lesion that can be diagnosed by CT (Figure 9).
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Figure 9. Lipoma. An intraluminal filling defect within the duodenum with low attenuation values of fat density (arrow).
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Multiple adenomatous duodenal polyps occur in 24–33% of patients with Gardner's syndrome [10]. Most polyps are located within the proximal half of the duodenum, mainly in the periampullary region (Figure 10). An adenoma–carcinoma sequence of these lesions has been observed, with periampullary carcinomas reported in 4–12% of patients with Gardner's syndrome.
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Figure 10. A 45-year-old man with Gardner's syndrome presented with jaundice. A small polypoid lesion of soft tissue density (arrow) at the medial aspect of the descending duodenum, the level of the ampulla of Vater, proved to be adenocarcinoma. Note the hydronephrotic right kidney.
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Primary malignant tumours include adenocarcinoma, which comprise about 80–90% of all primary duodenal malignant neoplasm, leiomyosarcoma and lymphoma [5, 6, 9].
Primary adenocarcinoma of the duodenum is usually found in the periampullary region as either a polypoid mass or an irregular, annular constricting lesion with mural thickening causing deformity of the lumen (Figure 11). Additional CT findings, such as invasion of retroperitoneal fat planes or surrounding organs, lymph node enlargement, vascular encasement and distant metastases help in predicting tumour resectability [9]. As with gastric carcinoma, helical CT with water as a negative contrast medium, together with drug-induced hypotonia and iv contrast injection, may be the best preparation for tumour staging when endoscopically and histologically proven duodenal cancer is known [11]. This technique is useful in evaluating local tumour invasion, as filling the duodenum with water reduces beam-hardening artefacts caused by oral contrast agents. Duodenal leiomyosarcoma, as elsewhere in the GIT, typically has a large extraluminal component, usually with necrotic and haemorrhagic changes (Figure 12). The tumour mass is usually greater than 5 cm, and metastatic spread may be found at the time of diagnosis. A leiomyoma, however, may have features of a malignant tumour, including a marked exophytic component with necrosis, ulceration or haemorrhagicchanges. Unless distant metastases are present, leiomyoma may therefore be indistinguishable from leiomyosarcoma on imaging grounds alone, even when a smooth muscle tumour is seen on endoscopy [9].
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Figure 11. Adenocarcinoma of the descending duodenum seen as circumferential thickening of the duodenal wall.
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Figure 12. Leiomyosarcoma. Contrast enhanced CT of a 48-year-old man with a necrotic extramural mass arising from the medial wall of the descending duodenum (D).
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Most duodenal lymphomas are of the non-Hodgkin's type, usually resulting from contiguous spread of gastric lymphoma. CT findings include asymmetrical mural thickening that seldom causesobstruction, or a large polypoid mass with necrosis or cavitation, similar to leiomyosarcoma (Figure 13). Aneurysmal dilatation of the affected duodenal segment is a diagnostic clue (Figure 14). Additional visceral or retroperitoneal lymphadenopathy as well as splenomegaly also suggest the diagnosis.
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Figure 13. Contrast enhanced CT of a 44-year-old man. A large extramural mass with a hypodense component in the distal portion of the horizontal duodenum proved to be lymphoma. The tumour narrows the duodenal lumen (arrows) with proximal dilatation.
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Figure 14. Contrast enhanced CT of a 57-year-old-woman with abdominal pain and vomiting. Irregular mural thickening at the ligament of Treitz with aneurysmal dilatation and ulceration (U) was due to lymphoma.
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Metastases
Direct extension from close visceral organs mayoccur in various primary neoplasms; pancreatic carcinoma (Figure 15), right colon cancer (Figure 16), gall bladder and right renal tumours may directly invade the medial or lateral aspect of the duodenal wall, and gastric tumours may spread across the pylorus. Colonic metastases spread across the mesocolon, extending between the hepatic flexure and the descending duodenum or via the lymphatic drainage to the mesenteric nodes surrounding the duodenum. Enlarged lymph nodes in lymphoma may encase the duodenum.
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Figure 15. Contrast enhanced CT of a 51-year-old man with a large necrotic carcinoma of the pancreatic head shows duodenal invasion as marked circumferencial mural thickening.
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Figure 16. Contrast enhanced CT of a 57-year-old man shows a large tumour of the ascending colon with direct extension (arrow) to the duodenum.
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Haematogenous spread from various primary tumours may reach the duodenum, especially from malignant melanoma, lung and breast cancer. A metastasis may be seen as a large soft tissue mass, sometimes with necrosis or cavitation, indistinguishable from lymphoma or leiomyosarcoma.
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Post-operative disorders
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Afferent loop syndrome, caused by obstruction of the duodenum and jejunum proximal to the gastrojejunostomy anastomosis, is an uncommon complication of subtotal gastrectomy with the Bilroth II procedure. The obstructive symptoms may occur acutely within days of surgery or may become manifest as a chronic syndrome years later. The dilated afferent loop is seen on CT in the mid abdomen as a U-shaped cystic mass, not opacified with oral contrast medium, with an approximately equal diameter throughout [12]. A few stretched valvulae conniventes are sometimes seen within it (Figure 17), as well as distention ofthe biliary system. The caudal portion of theafferent loop is typically located behind the superior mesenteric vessels, which may be displaced anteriorly.
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Figure 17. Afferent loop syndrome. Contrast enhanced CT of the upper abdomen shows a U-shaped tubular structure filled with fluid and identifiable valvulaeconniventes (small arrows). In addition, CT findings of intestinal non-rotation are seen. C, colon; large arrows, small bowel loops.
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Trauma
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Blunt duodenal injury occurs rarely, with a reported rate of 0.2% in a retrospective study from 22 163 blunt trauma patients [13], resulting in either perforation of this hollow viscus or intramural haematoma. A thickened duodenal wall or fluid in the anterior right pararenal space may be seen in both types of duodenal injury. Only free gas and/or oral contrast medium in the right anterior pararenal space are specific signs of duodenal perforation [14], while mixed attenuation within the wall of a thickened duodenum is characteristic of an intramural haemorrhage (Figure 18) [15].
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Figure 18. A 19-year-old man following blunt abdominal trauma. A large intramural duodenal haematoma with characteristic mixed attenuation. Fluid, probably blood (arrow), is also present in the right anterior pararenal space.
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Spontaneous haematoma
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Spontaneous intramural haematoma, with an identical CT appearance to post-traumatic haemorrhage, was once considered rare but is reported more often nowadays in association with anticoagulant treatment and blood dyscrasias [16].
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Bezoar
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A bezoar is composed of accumulated foreign material within the GIT, trichobezoars and phytobezoars being the two commonest. Trichobezoar, a concentrated ingested ball of hair, occurs mainly in young women. It usually fills the stomach and the first portion of the duodenum (Figure 19) but may extend through a long segment of the small bowel and even reach the ileocaecal valve. The CT appearance of a trichobezoar is characteristic of a large, heterogeneous, entirely intraluminal mass. Entrapped air within the mass is considered a helpful diagnostic sign [17].
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Figure 19. Trichobezoar. CT of a 14-year-old girl with epigastric pain and anaemia. A large intraluminal heterogeneousmass, with mottled gas within the stomachand third part of the duodenum, surrounded by oral contrast medium.
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Received for publication October 31, 2000.
Revision received March 23, 2001.
Accepted for publication April 17, 2001.
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Abstract
Introduction
