The gastrointestinal tract

The small intestine

 

The length of the small intestine varies among individuals between 3-10 metres. Fully distended as in an enteroclysis examination the calibre of the upper jejunum is 3-4 cm, the lower jejunum 2.5-3 cm and the ileum 2-2.5 cm. The values for a "follow-through" type examination are 3 cm for the jejunum and 2.5 cm for the ileum. The wall thickness is measurable when, on a contrast examination, two loops are parallel over a length of 4 cm during compression; the combined thickness of the apposing walls should not exceed 2 mm. The normal mucosal pattern of the small bowel depends on the method of examination. On enteroclysis, when there is optimal distension, the transverse mucosal folds (valvulae conniventes) occur at a dens it y of 6-12 every 5 cm length of bowel and are up to 2 mm thick; they extend "ladder-like" across the whole width of the lumen (Fig. 38). The folds are more prominent in the jejunum and are often absent in the distal ileum. On small bowel meal (follow through) examination the mucosal pattern is feathery due to secondary mucosal folds, which are effaced on enteroclysis.

Imaging techniques

In recent years there has been an increasing emphasis on the usefulness of CT in the diagnosis of small bowel disease and, with regard to contrast studies, more widespread use of enteroclysis techniques.

Plain radiographs

These are of limited use in non-acute disease (see chapter on the Acute Abdomen) but may be of help in patients with abdominal pain when subacute or recurrent obstruction is suspected.

Contrast studies
It is no longer appropriate to perform a follow-through examination as an adjunct to a barium meal, merely obtaining a few delayed spot films of the small bowel during the transit of barium. This is an inaccurate examination and, when performed after a double contrast barium meal, is usually technically inadequate as the high density barium does not lend itself to this application. The choice of barium study is between an enteroclysis examination (small bowel enema - SBE -; intubation study) and a dedicated small bowel series (small bowel meal). There is controversy as to which is the superior study for routine use. Some radiologists perform enteroclysis on all patients; others perform small bowel meals almost exclusively; still other use enteroclysis selectively. Each type of examination has its advantages and disadvantages. Although it is difficult to perform prospective comparative trials, there is a widespread consensus that enteroclysis is the more accurate examination, particularly for the depiction of proximal disease, skip lesions, subtle strictures and mucosal abnormalities. The infusion of contrast at enteroclysis leads to continuous flow through the small bowel with resultant maximal distension allowing detection of mild narrowing and the examination of individual loops with compression. However, enteroclysis requires greater technical skill, more radiologist's and room time, the relative discomfort of the passage of a nasojejunal tube, and greater radiation exposure. Many radiologists argue that, when performed with due attention to detail, the small bowel meal is sufficiently accurate and is arguably less demanding on patient and radiologist. Contraindications to both techniques include suspected bowel perforation and large bowel obstruction. In the latter, antegrade administration of barium may worsen the problem when the barium becomes inspissated proximal to an obstructing lesion. However, small bowel obstruction is not a contraindication since in these circumstances the contrast remains sufficiently thin in the already fluidladen small bowel to avoid exacerbation of the obstruction.

The small bowel meal is performed on a fasting patient. Purgatives to clear the caecum and terminal ileum of faces are desirable, but not universally used. Dilute barium sulphate suspension (about 45% w/v) to a volume of 300-600 ml is taken orally by the patient. Rapid and continuous gastric emptying is important to ensure a non-interrupted barium column in the small bowel. Therefore, the patient drinks laying on his/her right side and the rate of drinking is kept sufficient to maintain some barium at the pylorus. Metoclopramide 10-20 mg orally may also be used. The upper GI tract is screened and spot films taken to exc1ude gross gastroduodenal pathology. Films of the small intestine are taken at ten minutes (supine) and then at 20 minute intervals (prone) until the terminal ileum is reached. Any abnormality is fluoroscoped with compression and spot films obtained. The terminal ileum is always screened with and without compression. Several variations on this technique are employed, such as the use of hurrying agents, e.g. metoclopramide, or cholecystokinin, or a "peroral pneumocolon" procedure.

The small bowel enema (SBE) or enteroc1ysis examination is performed following bowel preparation to clear the right colon of faecal material. A nasojejunal tube is placed under topical anaesthesia. Various types are employed, the commonest being the size 12 French BilbaoDotter tube or a variation thereof. Others inc1ude balloon catheters designed to prevent reflux of barium into the duodenum and stomach. Some radiologists use a single-contrast dilute barium technique; others chase the barium with water to obtain a double-contrast effect in the jejunum; still others perform a biphasic examination using methylcellulose or air to provide double-contrast. There is little objective evidence that any technique is significantly superior. Intermittent fluoroscopic screening is carried out with spot films of jejunum and ileum with compression to separate individual loops. Filled and collapsed views of the terminal ileum are obtained. Whichever method of enteroc1ysis is employed it is axiomatic that accuracy depends on the two factors of maximal distension and compression views of individual loops.
In the context of the post-operative patient with a small bowel which is slow to become normally motile, some authors believe that a water-soluble small bowel follow-through using hyperosmolar contrast such as Gastrografin will accelerate the process of recovery. This is presumed to relate to the distension of the bowel caused by drawing into the lumen of fluid by the hyperosmolar agent.

Signs of disease to observe on contrast studies include:
Lumen changes: strictures, dilatation, compression, pseudodiverticula

Figure 39. Ultrasound of thickened bowel. Relatively hypoechoic thick walls (arrowed) with echogenic lumen. Appearances are non-specific - in this case, Crohn's disease of the ileum.

Wall abnormalities: wall thickening as evidenced by displacement of adjacent bowel loops.
Mucosal fold abnormalities: thickened folds, nodularity, crowding of folds, fold effacement. Submucosal oedema or infiltration tends to produce straight, thickened folds.
Ulcerations: aphthoid, transverse, longitudinal, "cobblestone" pattern (ulceronodular change produced by intersection of longitudinal and transverse ulceration with intervening oedema).
Nodules and filling defects: lymphoid hyperplasia, small and large nodules, polyps.
Sinuses and fistulae: to other parts of the bowel, other hollow organs or skin.

Ultrasonography
Bowel imaging with ultrasound suffers from limitations by the presence of bowel gas and faeces. However, abnormal bowel loops can be imaged when there is thickening of the wall; these have a sonolucent periphery, due to oedema or infiltration, and echogenic centre (Fig. 39). Extramural abscesses can be seen as usually relatively sonolucent masses containing internal echoes (Fig. 43). Omental and mesenteric masses may be identified, as well as enlarged lymph nodes, which are usually sonolucent.

Computed tomography
The ability of CT to demonstrate bowel wall thickening, extramural and mesenteric disease has seen its increasing use in suspected small bowel pathology. It is necessary to give adequate oral contrast to provide good lumenal distension (with the exception of high-grade small bowel obstruction, where there is often already distension by fluid content). Up to a litre or more of dilute water-soluble contrast or dilute barium is given in divided doses, starting about one hour prior to the scan. A hurrying agent such as sorbitol or metoclopramide may be added to the contrast. A dynamic bolus contrast-enhanced examination is performed. It may be necessary to obtain additional cuts through an area of interest, or to scan with thinner slices to provide greater resolution of the bowel wall. New generation scanners have the ability to acquire images of large volumes in a single breath-hold using helical scanning technology, and this may prove to be the technique of choice. Inflammatory diseases or ischaemia tend to cause symmetrical bowel wall thickening with homogeneous attenuation or a "double halo" or "target" appearance on enhanced images, whereas neoplastic lesions are associated with asymmetrical, irregular thickening.

Magnetic resonance imaging
The development of MR applications in the abdomen has been limited by motion artefacts, limitations in tissue contrast and, to some extent, by the lack of an ideal oral contrast agent - particularly a "negative" agent. Fat suppresion and the increasingly wider availability of fast pulse sequences (including echoplanar techniques) are likely to result in considerable increase in utility of MR in the GI tract. There is preliminary evidence that MR can help distinguish active inflammation from fibrosis in inflammatory disease and accurately delineate enteric fistulae and abscesses.

Pathology

Inflammatory diseases

Crohn's disease
Suspected Crohn's disease is one of the commonest indications for contrast studies of the small bowel in the developed world. The role of radiology encompasses diagnosis, assessment of extent and distribution of disease and the imaging of complications. Although the sensitivity of enteroclysis is reported as extremely good in detecting Crohn's disease, the radiographic features often do not correlate well with disease activity. Ultrasound examination is useful in demonstrating thickened bowel wall and it has been suggested for screening patients for a demonstrable cause of abdominal pain.

The features seen on small bowel contrast studies can be classified as superficial, transmural and extramural abnormalities.

Superficial abnormalities: "Early" changes that are described include thickened folds (which are straight, due to submucosal oedema), aphthoid ulcers, punctate collections of barium and small nodules. These may occur alone or in combination. However, these have not conclusively been shown to progress to the typical more advanced changes of Crohn's disease and many patients with such signs as aphthoid ulcers may have inflammatory diseases of other types, such as Yersinia infection; other signs may represent normal variants. True superficial abnormalities in Crohn's disease include aphthoid (Fig. 40) and "punched-out" u1ceration, mucosal granularity and transverse and longitudinal ulcers (Fig. 41). The latter may be short or long and usually occur along the mesenteric border where they are associated with contraction and concavity of that border. Cobblestoning is frequent. Abnormal mucosal folds are seen; these are thickened and may be nodular, especially when associated with aphthae. Thickened folds are of ten an early sign of recurrent disease proximal to a surgical anastomosis. When disease is longstanding the folds may become effaced.

Transmural abnormalities (Figs. 41-43): Crohn's disease is typically a transmural process; the signs associated with this constitute the classic features of this disease. Deep u1ceration is seen as fissure (transverse, "rose-thorn") ulcers and penetrating, discrete ulcers. It may be difficult to distinguish fissure ulcers and barium trapped in troughs between oedematous folds. Large excavated ulcers are very unusual and suggest an alternative diagnosis. Cobblestoning is a feature of intersecting longitudinal and transverse ulcers, with intervening heaped-up oedematous mucosa. Deep ulceration may result in the sinuses and fistulae characteristic of severe Crohn's disease. Thickened bowel wall may be manifest as separation of loops. Luminal narrowing is nearly always present to some degree and may be due to spasm and oedema during the acute phase, or

	Figure 40. Aphthoid ulceration of terminal ileum (small arrows)- Note also "cobblestoning" (larger arrows).
	Figure 41. Typical features of Crohn's disease of the distal ileum including fissure ulcers (small arrows), longitudinal ulcers (arrowhead), "cobblestoning" (open arrows), aphthoid ulcers (curved arrow) and stricturing. ic=ileocaecal valve.

compression from mesenteric disease, or, later, due to fibrotic strictures. Crohn's disease typically affects the bowel asymmetrically involving the mesenteric aspect and adjacent mesentery more severely than the antimesenteric border; as fibrosis occurs, shortening of the mesenteric side leads to redundancy of the antimesenteric border and, thus, sacculation. A typical feature of Crohn's disuse is a gradation of abnormalities along the affected segment of bowel; this may help in the differentiation from other pathologies, such as tuberculosis.

Extramural abnormalities: Mesenteric inflammatory masses and abscesses may produce compression and displacement of bowel loops. Fibrosis in the mesentery, as stated above, leads to shortening of the mesenteric and redundancy of the antimesenteric border.

	Figure 42. Crohn 's disease of distal ileum with stricturing and sacculation on the antimesenteric aspect (curved arrows), and fissure ulcers (small arrows). Open arrow points to ileo-caecal valve.
	Figure 43. Ultrasound image demonstrates pelvic abscess and enterocutaneous fistula complicating Crohn's disease. Abscess (arrows) contains internal echoes. Hyperechoic foci (arrowhead) represent gas in bladder (b) wall.

 
The distribution of small bowel Crohn's disease is best assessed by enteroclysis. The terminal ileum is nearly always involved in small bowel disease and is the only site in up to 30% of patients. "Skip" lesions are seen in up to 20%. Crohn's disease is typically asymmetrical- both circumferentially and longitudinally. Recurrent disease following bowel resection almost always involves the pre-anastomotic segment.

Complications of Crohn's disease are mainly related to its transmural nature. Strictures of ten lead to obstructive symptoms. It may be extremely difficult to distinguish bowel narrowing due to active Crohn's

Figure 44. Same patient as Fig. 43. CT of pelvis demonstrates thickened loop of ileum (small arrows), fistula to bladder (arrowhead) and gas in bladder wall (curved arrow) and in non-dependent aspect of bladder itself. More cranial image better showed associated abscess.

disease from fibrotic strictures, when other signs of activity, such as ulceration, are absent. There are preliminary data that MR may be useful in this distinction. Extramural complications often require ultrasound and/or CT for imaging. Sinuses and fistulae are common; fistulae may communicate with other loops of small bowel, colon, urinary or genital tract or skin. Enteroclysis will usually demonstrate such complications, but ultrasound or CT will demonstrate the extent of the disease and associated abscesses (Fig. 43). Sinograms may be helpful when there is cutaneous communication. Cross-sectional imaging is particularly useful in the diagnosis and management of abscesses complicating Crohn's disease. Many of these patients are young, and it is therefore reasonable to perform ultrasound initially to try to avoid ionising radiation, although a negative examination should usually be followed by CT since this is superior in the detection of abscesses, which may be interloop, intra- or retroperitoneal in site. CT is also the investigation of choice in suspected enterovesical fistula (Fig. 44). There is growing evidence of the sensitivity of MR in the detection of fistulae and abscesses related to Crohn's disease. As well as demonstrating these complications, CT in Crohn's disease will show the thickened bowel wall, mesenteric streaking and, sometimes, mesenteric nodules due to mildly enlarged lymph nodes.

The differential diagnosis of Crohn's disease on contrast studies is wide. There is usually no problem in the appropriate clinical setting where there are typical changes and distribution of disease. Difficulties occur when there is sparing of the terminal ileum, diffuse disease or there are atypical signs. Small bowel tuberculosis (TB; see below) may be indistinguishable from Crohn's disease and must be considered where TB

Figure 45. "Backwash ileitis" due to ulcerative colitis. Note features of chronic ulcerative colitis in right colon, patulous ileocaecal valve, dilated distal ileum with granular mucosa.

is endemic. Features that favour TB include a relatively abrupt change from normal to abnormal bowel, predominantly transverse ulcers (Japanese authors suggest that longitudinal ulcers are not a feature of TB), and marked caecal involvement with disproportionately less terminal ileal disease. Large excavated ulcers and discrete larger nodules without signs of mucosal inflammation favour lymphoma. Carcinoid produces a severe desmoplastic reaction in the mesentery, but does not usually lead to mucosal ulceration. Primary adenocarcinoma of the ileum may mimic Crohn's disease, but typically demonstrates the shouldered stricturing of a neoplasm. Acute infections (such as Yersinia) are not typically transmural processes. Ischaemic segmental strictures are of ten suspected by the history. Aphthoid ulcers are non-specific, occurring in a variety of pathologies including infections, such as Yersinia and TB, and lymphoma. "Backwash ileitis" is seen in ulcerative colitis when the whole of the colon is involved; the distal ileum is of normal or dilated calibre, the mucosa is granular but of smooth contour (Fig. 45).

Figure 46. Graft-versus-host disease in a bone marrow transplant recipient. There are several loops of ileum which demonstrate a featureless appearance - "ribbon bowel".

Miscellaneous inflammatory disorders
Behcet's disuse may affect the small bowel and produce changes similar to Crohn's disease. “Ring ulcers" have been described in the distal ileum and there is often a colitis. Long-standing use of non-steroidal anti-inflammatory drugs (NSAIDs) may result in a variety of small bowel abnormalities, including malabsorption, blood and protein loss, inflammation and ulceration. Single or multiple strictures, often short and weblike in configuration can give rise to obstructive symptoms. Other drugs, especially slow-release potassium-supplements may also lead to small bowel strictures. Graft-versus-host disease (GVHD) in bone marrow recipients can involve any or all parts of the bowel. In the small intestine fold thickening evolves into a featureless appearance with fold effacement ("ribbon bowel") on barium studies (Fig. 46). Acute GVHD is indistinguishable from viral enteritis on radiological findings alone and, indeed, these often co-exist. Gastric involvement and prolonged mucosal coating favour a viral pathology. Eosinophilic enteritis is characterised by episodic abdominal pain, diarrhoea and eosinophilia. Contrast examination demonstrates extensive or segmental thickened valvulae conniventes with moderate stricture formation. There is of ten nodularity or narrowing of the gastric antrum and enlarged or nodular rugal folds. In some patients there is oesophageal and/or colonic involvement.

Figure 47. Chronic ileocaecal tuberculosis. The caecum and ascending colon are retracted craniad and are fibrotic. scarred and saccilated (curved arrows). The terminal ileum in this patient is relatively patulous (straight arrows) and probably nodular. v=ileocaecal valve.

 

Infections

Tuberculosis
Tuberculosis, worldwide, is the most common chronic inflammatory disease of the small bowel. In addition, it is now increasingly seen in the developed world in association with HIV infection in immunocompromised hosts. The radiological features may be indistinguishable from Crohn's disease. Less than 50% of patients have demonstrable pulmonary involvement. The ileocaecal region is the commonest site in the bowel. Ulcerative and hypertrophic forms have been described. Early signs inc1ude thickening of the mucosal pattern and nodularity in the terminal ileum. In the acute phase there is spasm of the caecum with a narrowed and ulcerated distal ileum. Ulcers are transverse or circumferential in orientation. Occasionally large cavitating ulcers are seen which mimic those seen in lymphoma. Later the caecum becomes contracted and retracted in a cephalic direction as the hypertrophic granulomas lead to fibrosis (Fig. 47). The ileocaecal valve may be patulous, but as the disease progresses it may narrow. Strictures of the distal ileum are typical short and "hour-glass" in configuration. Complications include fistulas and perforations which are usually localised. CT will demonstrate the thick-walled bowel and may show tuberculous ascites and lymph node enlargement, which is typically greater than that seen in Crohn's disease, or an inflammatory mass that may surround the ileum. Nodes may be necrotic (caseating) and/or calcified. Other features that help distinguish Crohn's disease and tuberculosis are listed under Crohn's disease.

Other chronic infections such as South American Blastomycosis and disseminated Histoplasmosis can simulate Tuberculosis and Crohn's disease in the ileocaecal region. Actinomycosis has a particular propensity to form sinuses and fistulae in the right iliac fossa.

Yersinia Enterocolitica lnfection
This causes a self-limiting terminal ileitis or mesenteric adenitis. The distal 10-15 cm of ileum are involved, but the colon may also be abnormal. Aphtoid ulcers and lymphoid hyperplasia may be demonstrated on contrast studies. Ultrasound examination, of ten performed for suspected appendix inflammation, may show a circumferentially thickened distal ileal wall and/or hypoechoic regional mesenteric lymph node enlargement. Patients with iron-overload syndromes may be susceptible to more severe, even life-threatening, infection.

Giardiasis
Giardia lamblia infestation produces non-specific radiological changes. The proximal small bowel is maximally affected, where there is thickening of the valvulae conniventes. Giardiasis is associated with nodular lymphoid hyperplasia in patients with hypoglobulinaemia.

Strongyloidiasis
This may be asymptomatic when infestation is mild or produce symptoms related to the upper GI tract, often simulating peptic ulcer. Small bowel motility disturbances and hypersecretions may occur. On small bowel follow-through examinations there is a malabsorption pattern. Severe, even overwhelming, infestation is seen in immunosuppressed patients. Ulceration occurs in the proximal small bowel leading to strictures and loss of normal mucosal fold pattern (Fig. 48).

AIDS-related infections
A variety of opportunistic pathogens may affect the small intestine in AIDS patients. It may be difficult to separate out the features of

	Figure 48.Strongyloidiasis affecting the distal duodenum and proximal jejunum. There are multiple strictures and loss of normal folds. St=stomach.
	Figure 49. Nodular filling defects in small bowel of AIDS patient (same of which are arrowed) are consistent with the submucosal deposits of Kaposi sarcoma. Disease was present elsewhere in the bowel. Although unverified in this patient, the thickened folds and pa or coating probably represent co-existent opportunistic infection - most likely cryptosporidium.

individual organisms, since many produce similar radiographic abnormalities and since there may be multi-organism involvement (Fig. 49). However, there are characteristic patterns that may be recognised radiographically based on the distribution of disease, the presence of distortion of folds, nodularity and changes in small bowel calibre. Commoner pathogens include Cryptosporidium, Mycobacterium avium intracellularae (MAI) and Cytomegalovirus (CMV). Cryptosporidium is a protozoan that causes a cholera-like syndrome. It predominantly affects the proximal small bowel and on contrast studies causes thickened folds, a dilated lumen or spasm, nodular duodenal folds and hypersecretion leading to poor mucosal coating. Gastric involvement may also be seen, where it is commonly associated with CMV infection, and leads to antral narrowing. Small bowel changes similar to Cryptosporidium may also occur in giardia, hookworm, strongyloides, CMV and Isospora infections. Mycobacterial infections of the small bowel may be related to Mycobacterium tuberculosis or atypical mycobacteria such as MAI. The latter causes a disseminated disease affecting lungs, liver, spleen, marrow and lymph nodes, as well as the GI tract. In the small bowel MAI leads to radiographic features similar to Whipple's disease. There is mild dilatation, thickened folds and fine nodularity. In the ileum, particularly, a pattern may be seen consisting of prominent folds without wall thickening. CT scanning demonstrates mesenteric and retroperitoneal nodal enlargement, splenomegaly and ascites.

CMV affecting the small intestine causes a diffuse inflammation which may include the large bowel. CMV is associated with a vasculitis and therefore ischaemic necrosis and subsequent perforation is not uncommon. Radiographic changes may be diffuse or limited to the distal ileum, where it causes thickened walls and narrowing, sufficient to produce obstruction, submucosal nodularity and ulceration. Adenopathy is not a feature on CT scanning.

Other small bowel infections and infestations
In acute enteric infections such as Salmonella and Helicobacter (Campylobacter) apart from the occasional need for plain films, radiological investigation is rarely performed. Severe Salmonella infections are associated with a variable ileus on plain radiographs. In typhoid, plain films may be taken for the suspected complication of perforated bowel. Contrast radiography is rarely indicated in typhoid but demonstrates nodular thickening of the ileum, due to enlarged Peyer's patches, a dilated lumen and ulceration. Roundworm (Ascaris) infestation, when heavy, may be identified on plain radiographs by a tangle of worms outlined by gas in the lumen of the bowel. They may be associated with bowel obstruction. Barium studies will also outline them as filling defects and can also give rise to opacification of the GI tract of the worms. Ascaris may infest the bile duct. Hookworm infestation is accompanied by a normal barium study or non-specific changes of coarsened mucosal folds. Tapeworms can give rise to bowel obstruction. Rarely they may be seen on contrast examination as long linear radiolucent filling defects within the barium. Whipple's disease is a systemic disease caused by an unknown organism but classified as an infective disorder, in part due to its response to antibiotic therapy. The characteristic cells that are seen on small bowel and lymph node biopsy are "foamy macrophages". Radiographic changes on barium studies include thickened folds with a variable degree of dilatation of the lumen. These features are predominantly seen in the jejunum. On double-contrast enteroclysis tiny nodules of 12 mm are seen representing swollen villi. CT or ultrasound demonstrate abdominal lymph node enlargement in about half of the patients. The nodes may be of low attenuation on CT and are echogenic on US.

Malabsorption
In adults the most common causes of malabsorption are coeliac disease (non-tropical sprue) and tropical sprue but other specific entities leading to malabsorption include systemic sclerosis (q.v.), jejunal diverticulosis (q. v.), Whipple's disease (q. v.), small bowel resections and blind-loop syndromes. In most cases of malabsorption, when the clinical, biochemical and histological diagnosis of sprue is straightforward, radiology plays little part. Indications for imaging in adult patients with suspected coeliac disease, to exclude morphological abnormality, include: atypical presentation or equivocal small bowel histology; unresponsiveness to a gluten-free diet or recurrence of symptoms after initial response (to exclude lymphoma or ulcerative jejuno-ileitis - see below); elderly patients presenting with recent onset of symptoms; patients with other disease states such as scleroderma, a history of abdominopelvic radiotherapy, etc. Radiological investigations include small bowel contrast studies and, in selected patients, CT examination. Findings in adult sprue on barium studies depend on the method used. If a dedicated peroral small bowel meal is performed a "sprue or malabsorption pattern" will be evident, which is non-specific (Fig. 50). This comprises dilatation, segmentation and flocculation. The jejunum is moderately dilated and hypomotile with associated slow transit of barium. Excess fluid in the lumen leads to segmentation of the barium column into separated clumps (this sign is not prominent with the use of modem barium suspensions) and flocculation of barium in severe disease. A mold-like configuration of barium in the lumen is due to fold effacement (the "moulage" sign). The valvulae conniventes are of normal thickness unless there is hypoalbuminaemia. Transient non-obstructive intussusceptions are seen in 20 %. Enteroclysis demonstrates diagnostic signs in 75% of patients with

Figure 50. Barium "follow-through" in patient with gluten-enteropathy. The jejunum is mildly dilated with slightly thickened folds, segmentation and flocculation of barium.

adult coeliac disease. The jejunal folds are fewer than normal, three or less per inch length being highly suggestive of the diagnosis. There may be jejunization of the ileum, i.e. a greater number of folds per unit length than normal. Intussusceptions are not seen on enteroc1ysis. In approximately 10% a 1-2 mm polygonal mosaic mucosal pattern is seen. Double contrast studies of the duodenum may show a "bubbly bulb" appearance and/or Brunner's gland hyperplasia.

Complications of coeliac disease include ulcerative jejunoileitis, strictures, small bowel neoplasms (lymphoma or, less commonly, adenocarcinoma), cavitating mesenteric lymph node syndrome, splenic atrophy and oesophageal carcinoma. Ulcerative jejunoileitis is a very severe disease which may present de nova or in patients with a known history of coeliac disease. Acute symptoms may be due to haemorrhage, obstruction or perforation. Barium studies, if performed, will show areas of stricturing and thickened folds and often deep ulceration. This entity is probably part of the spectrum of small bowel lymphoma. Short strictures, frequently multiple, are seen in the chronic form of the disease. Lymphoma complicating coeliac disease is usually multifocal or diffuse. Differentiation radiologically from ulcerative jejunoileitis may be difficult, and indeed the two may coexist. CT examination will show any mesenteric nodes, but the presence of enlarged nodes in coeliac disease is not specific to lymphoma. CT or ultrasound scanning will also demonstrate the splenic atrophy that complicates coeliac disease. Cavitating mesenteric lymph node syndrome is a rare and usually fatal complication. Enlarged mesenteric nodes undergo cavitation and there is villous and splenic atrophy. CT scanning will demonstrate the enlarged nodes with diminished central attenuation; there may be fat/fluid levels within them.

Tumours
A variety of benign tumours occur including adenomas, leiomyomas and vascular tumours. These are most common in the jejunum, whereas malignant lesions, with the exception of adenocarcinoma, are more common in the ileum. Adenomas may be part of polyposis syndromes but are less frequent than in the duodenum. Pre-operative diagnosis of malignant small bowel tumours used to be achieved only in the minority of cases. A combination of enteroclysis and CT scanning can now detect and suggest the diagnosis in the majority of tumours. Lipomas, leiomyomas, leiomyosarcomas and carcinoid tumours can give a characteristic pattern on CT. Adenocarcinoma and