MRI examination of the upper intestinal tract

11 Current CT/MRI intestinal tract

examination of the upper

PATRICE TAOUREL JEAN PRADEL JEAN-MICHEL BRUEL

Computed tomography (CT) is . routinely used in examining patients with nonspecific abdominal symptoms. Discovery of an unsuspected alimentary tract disorder is a relatively common event in these patients. Furthermore CT is used more and more in the evaluation of patients with suspected gastrointestinal disorders. Even if endoscopy and standard barium examinations provided information about mucosal abnormalities which are not detectable with CT, the ability of CT to demonstrate the intramural and extramural components of the disease is an advantage. Furthermore CT has other important applications including the staging of gastrointestinal neoplasms, the assessment of extraluminal postoperative tumour recurrence or the guidance of interventional procedures. Because of this widespread use and interest of CT, radiologists and also gastroenterologists need to be aware of the CT findings of common alimentary tract diseases. Magnetic resonance imaging (MRI) is not routinely used for the gastrointestinal tract for a variety of reasons: artefacts due to lack of a good magnetic resonance contrast agent for the gut and most important high cost and limited availability. Nevertheless, some studies have assessed the utility of MRI compared to CT in evaluation of upper gastrointestinal tract disorders. This currently appears to be very limited and the few small advantages of MRI will be mentioned in this chapter. NORMAL

CT ANATOMY

The oesophagus

Delineation of the oesophagus in CT depends on the extent of surrounding mediastinal fat (Halber et al, 1979). The oesophagus may be divided into three parts. -The cervical oesophagus, which extends from the pharynx to the upper margin of the sternum, is surrounded by minimal fat tissue and has a poor CT demarcation. Bail&e’s Clinical GastvoenterologyVol. 8, No. 4, December 1994 ISBN&7020-1855-4

743 Copyright 0 1994, by Baillike All rights of reproduction in any form

Tindall reserved

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-The thoracic oesophugus lies from the aortic arch to the diaphragmatic hiatus. It is well visualized on CT scans as a thin-walled tubular structure anterior to the thoracic spine and posterior to the airways. A fat plan is rarely present between the oesophagus and the airways (Halber et al, 1979). Some technical meanings have been described for the filling and distension of the oesophagus. The most reliable is to ask the patient to swallow air during the slices (Raptopoulos, 1989). When the oesophagus is adequately distended, the wall thickness should be no more than 5 mm and is usually less (Moss, 1982; Desai et al, 1991) and a thickening over 5mm is considered abnormal (Moss and Thoeni, 1983). Even if the oesophagus is non-distended, air is often present in the lumen and should be located centrally (Desai et al, 1991). -The intra-abdominal oesophagus extends between the diaphragmatic hiatus and the cardia. The normal oesophagogastric junction can create a mass-like appearance because of the oblique course of the oesophagus before it enters the cardia (Marks et al, 1981; Reeders and Bartelsman, 1993).

The stomach Maximal distension of the stomach with oral contrast material or gas is required for proper evaluation. Under these circumstances, the normal wall except for the region of the gastro-oesophageal junction, measures 3-5 mm in thickness with 10mm being the thickest normal measurement. A transition in gastric wall thickness is often present at the gastric air-fluid level; in an air-filled stomach a 3 mm wall thickness is considered the highest normal limit. As it was stated (Hammermann et al, 1989), the gastric air-fluid sign is useful in CT assessment of gastric wall-thickening. With adequate gastric distension the folds which have symmetrical distribution are clearly visible.

The duodenum The normal duodenal wall is usually thinner than the stomach wall, measuring l-2mm in thickness. As the duodenum is the site of rigorous peristalsis, the use of gastrointestinal tonus modifying agents is frequently necessary for adequate distension.

The small intestine Adequate opacification with oral contrast material is required for a conclusive evaluation of bowel wall-thickening. The normal small bowel wall measures 2-3 mm with a wall thicker than 4 mm considered abnormal. Folds are commonly seen in the jejunum where they should be 3mm or less in diameter (Desai et al, 1991) but they are usually not visualized in the ileum.

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TUMOURS

Carcinoma The different steps in the diagnosis of a carcinoma include detection, characterization and staging of the tumour, and follow-up after treatment. Oesophageal carcinoma

For the detection of the tumour, CT is not accurate since thickening of the oesophagus is not usually found in early oesophageal cancer. When it is present, the CT sign of oesophageal carcinoma is a focal wall-thickening with eccentric or nonoesophageal lumen. This finding is very nonspecific in comparison to endoscopy with adequate biopsy specimens. So CT is not reliable in the characterization of oesophageal tumour. The fundamental utility of CT is in the staging of oesophageal cancer. This relates more to its role in treatment selection than its ability to place the patient in particular staging niches (Halvorsen and Thompson, 1989b; Reeders and Bartelsman, 1993). The key points for treating a patient by curative or palliative measures are as follows: the presence of a tracheobronchial invasion; the presence of an aortic invasion; the presence of pericardial invasion; the presence of metastasis; the presence of coeliac or gastrohepatic involved nodes which may, by their volume and their fixity, preclude gastric pull-through. Therefore it is necessary to study the CT criteria used in order to answer these key questions. Tracheobronchial invasion. CT is accurate for detecting tracheobronchial invasion with an accuracy of more than 95% (Quint et al, 1985). The extension of the tumour into the lumen of the airway is a specific sign of tracheobronchial involvement (Takashima et al, 1991). The indentation of the posterior wall of either the trachea or bronchus is a more sensitive sign of airway involvement (Figure l), this must be obtained during inspiration because posterior wall of the trachea or main bronchi may bow inwards during expiration (Thompson et al, 1983; Halvorsen and Thompson, 1989b; Reeders and Bartelsman, 1993). However, these criteria should not be used to stage cervical oesophageal carcinoma because indentation of the posterior wall of the cervical trachea by the cervical oesophagus is a normal finding due to the narrow anteroposterior diameter of the neck. Aortic invasion. CT assessment is more difficult for aortic invasion than for

tracheobronchial invasion. CT accuracies in detecting aortic invasion ranged from 66 to 90% (Picus et al, 1983; Lozac’h et al, 1989; Reeders and Bartelsman, 1993). The criteria used to predict invasion are an area of contact greater than 90” of the oesophageal circumference (Picus et al, 1983) between the tumour and aorta, and an obliteration of the triangular fat space between the oesophageal tumour, aorta and spine (Takashima et al, 1991). Pericardial invasion. To determine pericardial invasion, evaluation of multiple CT sections is required. If a fat plane separating the oesophageal

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Figure 1. Oesophageal carcinoma with tracheal invasion. CT demonstrates a large and eccentric thickening of the oesophageal wall. This oesophageal tumour gives a marked indentation of the posterior wall of trachea.

mass from the pericardium is visible on all CT sections then the scan should be interpreted as without evidence of pericardial invasion. When an oesophageal tumour mass extends directly to the pericardium without the intervening fat plane, the possibility of invasion must be considered. If a fat plane is detected between the oesophagus and pericardium immediately above and below the tumour mass, but obliterated at the level of the tumour, then invasion is likely. When fat planes are not detectable at any level, the study is considered indeterminate (Reeders and Bartelsmann, 1993). Metustuses. The most common

sites of distant metastases in oesophageal carcinoma are the liver and the lungs.

lymphadenopathies. Abdominal (coeliac and gastrohepatic) lymph nodes are as frequently invaded by oesophageal carcinoma than mediastinal nodes (Akiyama et al, 1981). On CT, nodes larger than 1 cm in their shortest diameter are usually considered metastatic. With this criterion, sensitivity is about 60% and specificity about 90% (Balfe et al, 1984; Takashima et al, 1991). The combination of low sensitivity and high specificity shows that enlarged lymph nodes on CT scans are generally involved by metastatic tumour whereas the absence of enlarged lymph nodes is an unreliable finding because normal-sized lymph nodes may also contain metastases. Other prognostic factors include the depth of tumour invasion and the presence of regional lymph nodes. CT is not accurate for evaluating the depth of invasion; it cannot differentiate submucosa invasion (‘Tl’ according to the TNM staging of malignant tumours) from muscularis propria invasion (‘T2’) and it underestimates the adventitial extension (‘T3’) Regional subdiaphragmatic

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because of microscopic invasion that cannot be detected. CT has a number of limitations in detecting mediastinal lymph node metastases. It cannot demonstrate lymph node metastases that have not caused significant enlargement of the node, and even when they are enlarged, nodes may not be detected when they are very close to the primary lesion. Thus, the sensitivity of CT for diagnosing mediastinal lymph node metastasis is about 50% (Halvorsen and Thompson, 1989b). These difficulties of CT in the pre-operative staging of oesophageal carcinoma have increased the use of endoscopic ultrasonography (ES) in oesophageal carcinoma. ES has three major advantages compared to CT. 1.

It can define the extent of wall invasion (Ziegler et al, 1991). Even if this is not always decisive for the treatment, the depth of invasion is a prognostic factor which can be studied when comparing different preoperative treatment modalities (Kelsen et al, 1990). 2. It could separate malignant lymph nodes from normal or benign but this role is still controversial (Botet et al, 1991a; Baker and Kopecky, 1991). 3. It could be more accurate than CT in diagnosing tracheobronchial, aortic invasion and pericardial invasion (Vilgrain et al, 1990; Botet et al, 1991a). However, further comparative studies are necessary in order to confirm that. On the other hand, ES is less accurate than CT in determining metastatic extension (Botet et al, 1991a) and it can be limited, in 20-50% of patients (Tio et al, 1989; Vilgrain et al, 1990; Botet et al, 1991a) due to the difficulty in passing the oesophageal ultrasound probe through a malignant stricture. In conclusion, we recommend the use of CT in the preoperative staging of oesophageal carcinoma. If CT shows obvious metastatic disease or local invasion, patients are candidates for palliative treatment only. If CT is inconclusive then ES must be performed to define the most accurate management. If CT does not show local invasion or distant metastases then the role of ES is still controversial. Moreover, CT is useful in the follow-up of the postoperative patient. As most recurrent disease is extramural, CT can detect recurrence prior to mucosal studies such as endoscopy or barium oesophagography (Becker et al, 1987). MRI has no advantage over CT in predicting resectability in patients with oesophageal carcinoma (Takashima et a!, 1991). Gastric carcinoma

As is the case for oesophageal carcinoma, CT is of little interest in the detection and characterization of gastric carcinoma. On CT scans, when it is found, the primary gastric carcinomas most frequently appear as an area of mural thickening which may be localized or diffuse (‘linitis plastica’). The causes of localized and diffuse mural thickening are numerous and this appearance is nonspecific. In some rare cases the abnormal gastric wall may contain calcifications or may show a density close to that of water because of its high mucin content which are suggestive of mutinous carcinoma

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(Nishimura et al, 1984; Miyake et al, 1989). The circumferential thickening of the gastric wall in linitis plastica may sometimes be a useful sign because of the low sensitivity of endoscopy with biopsies in diagnosing scirrhous tumours (Evans et al, 1985). The interest of CT for the preoperative staging of gastric carcinomas is still under debate. This interest is controversial since palliative surgery must be performed even for nonresectable tumours to prevent complications such as bleeding or obstruction. However, any decision about the feasibility of radical versus palliative surgery could be facilitated by adequate preoperative staging (Moss et al, 1981). The key points for management are: an extension of adjacent organs, the presence of intraperitoneal seeding, the involvement of secondary lymphatic sites and the presence of metastases. Extension to adjacent organs (pancreas, liver, colon). The distinction between invasion and contact is difficult, for instance the accuracy of CT in predicting pancreas invasion is only about 50% (Cook et al, 1986; Halvorsen and Thompson, 1989a). seeding. Peritoneal reflection surrounding the stomach explains the peritoneal involvement present in gastric carcinoma where some patients may show seeded metastases in the ovaries, known as Krukenberg tumours. The accuracy of CT in detecting peritoneal carcinomatosis is about 70% (Cook et al, 1986).

Zntraperitoneal

Lymph nodes. The preoperative demonstration of involved secondary lymph nodes located in the porta hepatitis, the hepatoduodenal ligament and the peripancreatic region is important because these nodes are not systematically removed during routine gastric cancer surgery. CT is more accurate in detecting secondary adenopathies than local adenopathies with accuracy ranging from 60 to 75%. Metastases. The most common site of haematogeneous metastases are the liver, the lung and the adrenals. The other prognostic factors without impact on operative management in gastric carcinoma are the depth of tumoral invasion and the local adenopathies. CT is unable to precisely evaluate the mural extension of the tumour and underestimates the serosal extension because of its inability to detect microscopic invasion. In gastric carcinoma, CT has the same limitations as in oesophageal carcinoma in detecting primary (peripyloric, gastrocolic or gastrohepatic) adenopathies. For evaluating the depth of tumour penetration and for diagnosing of local adenopathies, ES is dramatically more accurate than CT (Botet et al, 1991b). In conclusion, the usual operative management of gastric carcinomas and the failures of CT in staging make the role of CT controversial in gastric carcinomas. For some authors, CT must be performed systematically to preoperatively stage gastric carcinomas whereas for others CT must be reserved for debilitated patients with high surgical risks (Cook et al, 1986). For the follow-up, CT has a limited value in the assessment of local

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recurrence in the anastomotic regions where endoscopic explorations are relevant. However, relapses close to the anastomosis may be detected by CT but its efficiency compared to ES is not well defined. On MRI sagittal and particularly coronal images might be potentially helpful to assess tumour extension to other organs (Scatarige and Disantis, 1989). However, no report on the accuracy of MRI in staging gastric carcinoma have appeared in the literature. Small bowel carcinoma

Even if small bowel carcinoma is infrequent compared to oesophageal or gastric carcinoma, primary adenocarcinomas are the most common primary malignancy in the small intestine (Brookes et al, 1968). Duodenum and proximal jejunum are the most frequent sites. Diagnosis is generally delayed because the symptoms are nonspecific (Maglinte et al, 1991). Since endoscopy is often unreliable, CT, which is commonly used as a screening examination in patients with vague abdominal symptoms or with occlusive syndrome, has a role in the detection and characterization of tumours. CT has a detection rate of 80% comparable to accuracy of barium studies for small bowel tumour (Dudiak et al, 1989; Laurent et al, 1991). Criteria of small bowel tumour are the demonstration of either small intestine asymmetric wall-thickening of more than 1.5 cm or of mesenteric mass > 1.5 cm in diameter (James et al, 1987). Some CT patterns may suggest adenocarcinoma and differentiate them from other primary or secondary tumours, they include the proximal site of the turnout-, the existence of lumen narrowing and signs of obstruction (Dudiak et al, 1989; Laurent et al, 1991). However, adenocarcinoma may have an atypical presentation when ulcerated and simulating lymphoma, or when located in the duodenum where they are difficult to differentiate from pancreatic tumour (Laurent et al, 1991). For the staging of small bowel tumours, CT had the same limitations as for oesophageal and gastric tumour, particularly for the determination of local invasion and lymph node involvement. However, accurate staging has no significant impact on management since either palliative or curative resection is used to treat small bowel neoplasm. Lymphoma Seldom encountered in Hodgkin’s disease, gastrointestinal localizations are observed in l&20% of patients with non-Hodgkin’s lymphomas (NHL). Lymphoma can affect any portion of the alimentary tract. For a diagnosis of primary gastrointestinal lymphoma, the following criteria must be fulfilled (Dawson et al, 1961): -No superficial or mediastinal lymph nodes. -No involvement of the liver or spleen. -Normal white blood cell count. -Predominant alimentary tract tumour with lymph node involvement, any, confined to the drainage area of the involved segment of gut.

if

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According to Rubesin et al (1990), mesenteric nodal lymphoma with direct invasion of the small bowel must be classified as primary small bowel lymphoma. In both the primary and secondary forms, the stomach is most commonly involved followed by the small intestine whereas oesophageal involvement is very rare. The role of CT in gastrointestinal lymphoma is triple: it contributes to the positive diagnosis; it stages the lymphoma before treatment; and it follows the tumoral evolution in patients under treatment. Positive diagnosis of NHL CT patterns associate wall-thickening and ulceration. Parietal thickening is often severe (more than 2cm), extended and involving at times several distinct segments of the digestive tract. The luminal diameter is generally normal or widened (‘aneurysmal’ dilatation) (Figure 2). Except in mesenteric nodal form involving the small bowel, obstruction is uncommon because the infiltrating tumour weakens the muscularis propria and does not elicit a desmoplastic response. Ulcerations are relatively frequent. They initially extend into the intramural portion of the tumour but they may result in cavitation of the bulk of the tumour and this explains any perforation of the tumour in the mesentery with formation of an abscess (Rubesin et al, 1990). In gastrointestinal lymphoma, lymph node involvement is often severe and diffuse but may be lacking in a third of the cases. Staging of NHL CT has a very important role in evaluating the anatomic extent of lymphoma

Figure 2. Small bowel lymphoma. CT demonstrates a circumferential small bowel wall. The contrast-filled lumen is dilated. The dilatation’ of the lumen is suggestive of lymphoma.

marked thickening of the contrast-filled ‘aneurysmal

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because it can identify both associated visceral lesions (spleen, liver, kidneys, adrenals etc.) and lymph node enlargement. However, the anatomic extent is less important in non-Hodgkin’s disease since prognosis and management are based on histology type rather than on the number of involved sites (Castellino, 1991). Follow-up

of NHL

In patients under treatment, CT is useful in estimating the tumoral regression and in looking for recurrences after remission. For some authors, MRI may be very useful to characterize residual masses under treatment because residual scars can be distinguished from active lymphomas by the lower intensity of fibrosis on T2-weighted images (Negendank et al, 1990; Montalban et al, 1992). Smooth muscle tumours

Leiomyoma and leiomyosarcoma arise from the muscularis propria. Leiomyomas are the most common benign tumours in the upper gastrointestinal tract. Leiomyosarcomas are considerably less common than adenocarcinoma and account for less than 0.5% of oesophageal malignancy, l-3% of malignant gastric tumours and 20% of small bowel lesions (Philips et al, 1970; Wilson et al, 1975; Balthazar et al, 1981). The most frequent localization of leiomyoma and leiomyosarcoma is the stomach. Smooth tumours have a tendency to grow exophytically which limits the accuracy of endoscopy and barium studies. Furthermore positive biopsy specimens may not be obtained unless the overlying mucosa is ulcerated. Finally, even when tumoral specimens are biopsied it is often difficult to distinguish leiomyomas

Figure 3. Leiomyosarcoma mass, growing anteriorly

from

of the stomach. the stomach.

Well delineated, The compressed

non-homogeneously enhanced gastric lumen is seen posteriorly.

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from leiomyosarcomas on the basis of histopathological criteria. These failures explain the potential interest of CT in the diagnosis and characterization of smooth muscle tumours in the presence of gastrointestinal tumour. The CT signs (Figure 3) in favour of smooth muscle tumours are the exophytic growth of the tumour without circumferential gastrointestinal wall-thickening and the presence of ulcerations and foci of calcification (Megibow et al, 1985; Scatarige et al, 1985; Disler and Chew, 1992). Some criteria may distinguish malignant from benign tumours: leiomyosarcoma are larger than leiomyoma (average diameter, 12 cm versus 5 cm), less uniform in shape and more heterogeneous in density before and especially after bolus contrast where the central zone is not enhanced (Megibow et al, 1985). This last finding seems to be the most specific in suggesting malignant neoplasm. Leiomyoblastomas are currently large lobulated masses; the tumoral content is non-homogeneous with low density areas and parietal calcifications may be seen. Leiomyoblastomas are not considered to be active malignant tumours, but occasional cases of lymph nodes and hepatic metastases have been observed (Megibow, 1986). CT is also useful in the staging of leiomyosarcoma looking for peritoneal and hepatic metastasis whereas lymph node involvement is uncommon. Carcinoid

tumours

Carcinoids arise from the endocrine cells that are scattered among the exocrine or epithelial elements of various organs, that is, the diffuse endocrine system. They are slow growing tumours, always potentially malignant. Nearly 90% of carcinoids are found in the gastrointestinal tract

Figure 4. Ileum carcinoid tumour. pattern of linear densities. Note itself is not seen.

CT demonstrates the wall-thickening

a mesenteric mass with a radiating stellate of the adjacent loops. The ileal tumour

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(Godwin, 1975). After the appendix, where turnouts are usually benign, carcinoids are most frequently found in the ileum. Carcinoids are rare in the stomach and exceptional in the oesophagus (Buck and Sobin, 1990). Carcinoid syndrome very suggestive of the diagnosis is a late and uncommon clinical finding and on barium studies tumours are difficult to detect. This explains the role of CT in diagnosing carcinoid tumours. CT is helpful, not in detecting the primary site of the lesion but in showing the extent of the tumour in the mesentery (Picus et al, 1984). The extent of the tumour leads to a characteristic CT appearance (Figure 4) of a mesenteric mass with a radiating stellate pattern of linear densities (Cockey et al, 1985). This corresponds to the desmoplastic reaction attracting the intestinal loops. The thickening of affected bowel loops indicates oedema and/or ischaemia. Hepatic metastases are typically hypervascular, and they are often more visible before intravenous contrast bolus, as areas of decreased attenuation (Bressler et al, 1987). Metastases

Tumour cells involve the gastrointestinal

tract by different pathways:

extension, with tumour emboli seeding the submucosa along its anti-mesenteric border, which occurs in melanoma and in breast or lung cancers. -Lymphatic spread along the lymph system in the gastrointestinal wall which is important in the oesophagus where lymph drainage is longitudinal and explains gastric metastases produced by oesophageal carcinoma. -4ztruperitoneaZ spread, which occurs the most often from gastrointestinal tumours in men and from tumours of ovarian or uterine origin in women. -Direct extension from adjacent tumours or from non-contiguous tumours along fascias. -Huematogeneous

The mechanism of the extension depends on the localization of the gastrointestinal segment involved. -Metastatic disease to the oesophagus may occur with an epidermoid carcinoma of the lung. Direct extension of a medial tumour, and invasion from mediastinal lymph node metastasis are the two most common mechanisms of invasion. -Metastatic disease to the stomach may occur from direct invasion from pancreatic or colic tumour. -The most common pathways of metastatic spread to the small bowel are haematogeneous embolization and intraperitoneal seeding. In patients who have recovered from cancer surgery and who have occlusive syndrome, the obstruction may be due either to bowel metastases or to adhesions; CT may have an impact on the management of the obstruction in that it diagnoses the cause (Taourel et al, 1993). Metastases of the alimentary tract may be associated with liver metastases, abdominal lymph node metastases, or peritoneal carcinomatosis.

P. TAOUREL ET AL

Figure 5. Small bowel lipoma with an acute intussusception. CT demonstrates a distended intestinal loop with a double wall image. The inner content is non-homogeneous corresponding to the intussuscepted mesentery. The cause is clearly shown as a fatty density lesion due to a benign lipoma.

Other tumours

Other benign or malignant turnours, e.g. lipomas, easily characterized by CT (Figure 5) because of their fatty density, fibromas and fibrosarcomas, malignant histiocytomas, neurofibromas and schwannomas, are seldom found in the digestive tract area. INFLAMMATORY

DISEASES

Crohn’s disease

Crohn’s disease is a chronic inflammatory disorder of the alimentary tract characterized by involvement of the mucosa, the bowel wall and the surrounding mesentery. Any portion of the alimentary tract may be involved but the terminal ileum and proximal colon are most frequently diseased. CT is particularly helpful in the evaluation of patients with Crohn’s disease (Goldberg et al, 1983; Fishman et al, 1987). It is the best method to evaluate the mesenteric extension of the disease and it is useful for defining the full extent of the mural disease. However, because mucosal disease cannot be detected on CT, conventional barium studies remain the procedure of choice for early diagnosis of Crohn’s disease. Mural disease is shown on CT by bowel wall-thickening which is usually less than 15 mm, circumferential and symmetric (Figure 6), and often discontinuous as seen on barium studies (James et al, 1987). The bowel wall involved has a homogeneous soft-tissue density or exhibits alternative rings

‘IMRI OF THE UPPER INTESTINAL TRACT

(4

Figure 6. Crohn’s disease. (a) Moderate circumferential wall-thickening of two distal ileum loops. Note the fibrosclerolipomatosis changes in the mesentery. (b) More caudal CT slice showed a mass with a fluid-air content and enhanced wall. This abscess is developing in the mesentery.

of low and high attenuation referred to as a ‘double halo’ (two rings) or ‘target’ (three rings). These densities are related to rnucosal hyperaemia, submucosal oedema, inflammation, and/or fat deposition (Jones et al, 1986). Although originally described in Crohn’s disease, the ‘double halo’ and ‘target sign’ have since been reported in other benign small bowel diseases, such as ischaemic enteritis, infectious enteritis, radiation enteritis, eosinophilic gastroenteritis, Schdnlein-Henoch purpura, and bowel oedema associated with portal hypertension (Frager et al, 1983; Balthazar, 1991). Mesenteric abnormalities are common in Crohn’s disease. The most

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Figure 7. Jejunum haematoma. Circumferential intestinal wall-thickening with areas of spontaneous increased density, in a patient with anticoagulant therapy. CT also demonstrated a free perihepatic ascitis.

common is fibro-fatty proliferation or ‘creeping fat’ characterized by abnormal fat that has increased attenuation and strand-like densities. With more advanced disease, CT may show a phlegmon or an abscess (Figure 6(b) (liquid mass well defined, that may contain aeric images and contrast medium if there is communication with the digestive lumen). CT can guide percutaneous drainage of these abscesses, thereby circumventing the need for surgical intervention (Casola et al, 1987). Moreover, CT can demonstrate fistulas which were unsuspected by barium studies and define their full extent if contrast material is administered (Fishman et al, 1987). Fistulas may communicate with skin, muscle, vagina, adjacent solid organs, spine, bladder, or most commonly adjacent segments of gut. CT has the greatest impact in the evaluation and management of these complications (phlegmon, abscess, fistula) (Fishman et al, 1987). Other non-tumoral

causes of wall-thickening

A variety of other diseases causes wall-thickening of the organs in the upper alimentary tract (Figure 7). Even if the clinical setting and the clinical findings for each such disease are important assets when attempting a differential diagnosis, CT patterns may have an orientation value to characterize a parietal thickening (Table 1). SUMMARY

When properly performed, CT of the abdomen can provide valuable information about mural diseases of the alimentary tract. It can demonstrate

Stomach

Antrum more frequently than small bowel

Emphysematous gastritis

Eosinophilic gastroenteritis

Stomach (fundus and body)

Menetrier’s

disease

Stomach Duodenum

(annum)

Zollinger-Ellison syndrome

Hypertrophic gastritis

Infectious gastritis (Campylobacter, toxoplasmosis, cryptosporidiosis)

Stomach

Stomach

Peptic

disease

Oesophagus

Infectious oesophagitis

ulcer

Oesophagus

Gastro-oesophageal junction

Hiatal

Intramural pseudodiverticulosis

Distal oesophagus Proximal stomach

Varices

hernia

Site

Aetiology tubular

patterns

causes

wall thickening

thickening folds

wall and

Target

Multiple sign

intramural

gas bubbles

Marked thickening wall and coarsed rugal folds

Intermediate thickened

Focal thickening with sometimes gas or contrast-filled outpouchings from the lumen

Moderate

Marked thickening with intramural gas collection corresponding to the pseudo-diverticula

Formed by enhanced structures

suggestive

1. Non-tumorous

Wall-thickening

Table

Visualization (pancreas, Fluid-filled

hiatus

of gastrinoma duodenum) intestinal loops

oesophageal

et al, 1983

Smith,

1991

et al, 1986

et al, 1983

et al, 1991

De Lange

Fishman

Urban

Scatarige and Disantis, 1989

Pearlberg

Pujols and Ruzick, 1984

et al, 1987b

Widened

References Balthazar

CT findings

Abdominal venous collateral, splenomegaly cause of portal hypertension

Ancillary

of wall-thickening.

Vasculitis (rheumatoid vasculitis, HenochSchijnlein purpura, Behcet’s disease .)

diverticulitis

Small

Jejunum

Small

Whipple’s

Jejunal

Terminal Caecum

Typhlitis

disease

Terminal Caecum

Tuberculosis

bowel

bowel

ileum

ileum

Diffuse small bowel (jejunum ++)

Lymphangiectasia

ileum

Terminal Caecum

Bacterial ileocaecitis (Yersinia, Campylobacter, Salmonella)

Ubiquitous mostly distal ileum caecum

Crohn’s

disease

Site

I.-(conr.)

Aetiology

Table

sign

mural

mural

sign

Focal

Target

intramural

thickening

Low attenuation pneumatosis

area

bowel

patterns

of small

thickening

suggestive

Moderate thickening wall and folds

Moderate

Target

Wall-thickening

with

et al, 1991

1994

et al, 1984

Benya

Frick

Extramural involvement changes in the adjacent mesentery

planes

et al, 1990

et al, 1985

et al, 1986

Balthazar

Fakhri

Frik

Herlinger,

fluid of fascial

nodes

nodes

References

Nodal mass in the mesentery and retroperitoneum which contains fatty material

Mesenteric Thickening

lymph

Markedly enlarged with low density

lymph

bowel

mesenteric

signs (sclerolipomatosis abscess)

CT findings

Dilatation of small Ascitis Cause of secondary lymphangiectasis

Enlarged

Mesenteric phlegmon,

Ancillary

2t cm

Ubiquitous -jejunum (‘spontaneous’) -duodenum (posttrauma)

Depending on the radiation site mostly small bowel

Ubiquitous

Ubiquitous

Intramural haemorrhage

Radiation-induced gastrointestinal damage

Extragastrointestinal inflammatory process

Graft versus host disease (GVHD) after bone transplantation

bowel

bowel

Any portion of small bowel

small

small

Ischaemia

Diffuse

Diffuse

hypertension

Hypoprotidaemia

Portal

pneumatosis

zone

in the wall

adherence of the material to the luminal

attenuation

Prolonged contrast surface

Low

Areas of high attenuation within the wall eccentric in trauma circumferential in ‘spontaneous’

Parietal

of causal .)

lesion

the peritoneal

of loops of the mesentery

within

Renal enlargement Fatty infiltration of the liver

Demonstration (pancreatitis

Agglutination Thickening

Free blood cavity

Bowel dilatation portal and venous mesenteric gas Thrombosis of mesenteric artery or vein Ascitis

Jones

Fishman

et al, 1984

et al, 1987a

et al, 1988 et al, 1990

et al, 1985

Balthazar

Alpern Smerud

iz

s

Ii

i

2 $

760

P. TAOUREL

ET AL

the digestive origin of an abdominal mass, categorize a given lesion on the basis of its specific CT appearance and any associated CT findings, assess the extramural spread of gastrointestinal lesion, guide various interventional procedures (biopsy, drainage) and follow a patient’s response to therapy.

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