Small bowel imaging- a rapidly changing field and a challenge to radiology

[New solutions for an old problem : Current developments in oral contrast agents]

BACKGROUND

Several radiological societies in Europe have so far spoken out in favor of MRI of the small intestine over CT, since MRI is said to provide more detailed image information. Due to the limited availability of MRI machines, long waiting times arise for many patients who clinically require small bowel imaging.

OBJECTIVES

These circumstances guided our search for an improved CT technique that would provide scans that mimic the image impression of T1 sequence in MRI, i.e. with IV contrast-enhanced intestinal wall versus low/no signal lumen.

MATERIAL AND METHODS

The oral use of fat or oil is poorly tolerated by patients, as is the placement of a naso-duodenal tube for air insufflation. We have now succeeded in creating a foamy drink with 44% air content, which is kept stable by protein together with buffers, and can be easily administered orally. CT with the Lumentin® beverage as bowel filling agent has been tested on healthy adult volunteers; oncology patients; and Crohn's disease patients who, for comparison, also underwent MRI of the small bowel with conventional oral contrast.

RESULTS

The results so far with Lumentin® show a very good distribution throughout the entire small intestine with good lumen distension, images with strongly enhanced contrast of the intestinal mucosa, and lesions that are detected at the same or increased frequency as compared with MRI. Side effects were few and mild, and overall fewer than with commonly used oral agents. Lumentin's foamy consistency was unfamiliar to a few patients, but it wasn't difficult to drink.

CONCLUSIONS

The new and innovative luminal HU-negative contrast agent Lumentin® improves the diagnostic CT image quality. In addition, Lumentin® experimental MRI tests have provided promising results, which are currently leading to further clinical MRI studies.

Multidisciplinary management of gastrointestinal fibrotic stenosis in Crohn's disease

Crohn's disease (CD) is a chronic inflammatory bowel disease that can involve virtually any part of the gastrointestinal tract. CD complications are the main indications for surgery. A large proportion of these interventions are due to stricturing disease. Although immunosuppressive treatments have been used more frequently during the last 25 years, there is no significant decrease in the need for surgery in patients with CD. Unfortunately, surgery is not curative, as the disease ultimately reoccurs in a substantial subset of patients. To best identify the patients who will require a specific treatment and to plane the most appropriate therapeutic approach, it is important to precisely define the type, the size, and the location of CD stenosis. Diagnostic approaches aim to distinguish fibrotic from inflammatory strictures. Medical therapy is required for inflammatory stenosis. Mechanical treatments are required when fibrotic CD strictures are symptomatic. The choice between endoscopic balloon dilation, stricturoplasty, and laparoscopic or open surgery is based on the presence of perforating complications, the remaining length of small bowel, and the number and length of strictures. The non-hierarchical decision-making process for the treatment of fibrotic CD therefore requires multidisciplinary clinical rounds with radiologists, gastroenterologists, interventional endoscopists, and surgeons.

Fusion of gamma scintigraphic and magnetic resonance images improves the anatomical delineation of radiotracer for the assessment of gastrointestinal transit

OBJECTIVES

This paper describes the use of gamma scintigraphic and magnetic resonance (MR) fusion images for improving the anatomical delineation of orally administered radiotracers used in gastrointestinal (GI) transit investigations.

METHODS

Ten healthy volunteers ingested enteric-coated gelatin capsules containing 4.4 ± 1.1 MBq SmCl3-labelled resin. Four external body markers containing Sm and Gd-DTPA were placed on the left and right lower costal margins and iliac crests of each volunteer. Anterior and posterior planar images were acquired hourly for 9 h, followed by a final single photon emission computed tomography (SPECT) image and subsequent T1-weighted images using a 1.5 T MR system. Coronal scintigraphic images were fused with MR images and assessed for diagnostic information.

RESULTS

The fused images revealed a combination of the tissue and organ anatomy with an overlay of the distribution of the tracer. Compared with conventional scintigraphic imaging alone, SPECT-MR fused images improved the localization of spatial and temporal movements of the radiotracer throughout the GI tract.

CONCLUSION

Fusion of SPECT and MR images in conjunction with sequential scintigraphic images improved the assessment of segmental GI transit. These have the potential to provide more accurate diagnostic results and are visually powerful images that would have more widespread acceptance by nonspecialists.

Effectiveness of MR enterography for the assessment of small-bowel diseases beyond Crohn disease

The use of cross-sectional imaging techniques for the noninvasive evaluation of small-bowel disorders is increasing. The effectiveness of magnetic resonance (MR) enterography for the evaluation of Crohn disease, in particular, is well described in the literature. In addition, MR enterography has an evolving though less well documented role to play in the evaluation of other small-bowel diseases, including various benign and malignant neoplasms arising in isolation or in polyposis syndromes such as Peutz-Jeghers, inflammatory conditions such as vasculitis and treatment-induced enteritis, infectious processes, celiac disease, diverticular disease, systemic sclerosis, and bowel duplication. MR enterography may be useful also for the evaluation of intermittent and low-grade small-bowel obstructions. Advantages of MR imaging over computed tomography (CT) for enterographic evaluations include superb contrast resolution, lack of associated exposure to ionizing radiation, ability to acquire multiplanar primary image datasets, ability to acquire sequential image series over a long acquisition time, multiphasic imaging capability, and use of intravenous contrast media with better safety profiles. MR enterography also allows dynamic evaluations of small-bowel peristalsis and distensibility of areas of luminal narrowing and intraluminal masses by repeating sequences at different intervals after administering an additional amount of the oral contrast medium. Limitations of MR enterography in comparison with CT include higher cost, less availability, more variable image quality, and lower spatial resolution. The advantages and disadvantages of MR enterography performed with ingestion of the oral contrast medium relative to MR enteroclysis performed with infusion of the oral contrast medium through a nasoenteric tube are less certain.

Accuracy of imaging for predicting operative approach in Crohn's disease

Background

The aim of this study was to assess the accuracy of preoperative imaging in detecting the extent of disease and predicting the operative approach in patients with Crohn's disease.

Methods

Patients with Crohn's disease who were scheduled to undergo operation were evaluated before operation using computed tomography enteroclysis (CTE) and magnetic resonance enterography (MRE). Preoperative imaging findings were correlated with intraoperative and pathological findings to estimate the capabilities of preoperative imaging in detecting lesions due to Crohn's disease. The operative approach determined before surgery was compared with the procedure actually performed, which was based on intraoperative findings.

Results

Fifty-two patients with Crohn's disease were studied; 26 were evaluated before surgery with CTE and 26 with MRE. Eighty-nine lesions due to Crohn's disease were confirmed surgically (60 small bowel stenoses, 21 fistulas and 8 abscesses). CTE confirmed the presence of 38 of 41 lesions (sensitivity 93 per cent) and MRE 48 of 48 lesions (sensitivity 100 per cent); a correct estimation of the disease with an exact prediction of the operative approach was obtained in 49 (94 per cent) of 52 patients. Discrepant findings between preoperative imaging and operative findings were observed in three patients (6 per cent), who had CTE.

Conclusion

Preoperative imaging using CTE or MRE is highly accurate for assessing Crohn's disease lesions before operation, allowing correct prediction of the operative approach.

Recent advances in intestinal imaging

In recent years, advances in scanner technology and competition from other specialties have produced rapid changes in the way the intestines are imaged. MRI and CT scan along with the traditional enteroclysis examination have emerged at the forefront of intestinal imaging. Functional modalities such as diffusion and perfusion imaging are also changing the way tumors and inflammatory bowel diseases are evaluated. CT colonography is now a valid alterative to optical colonoscopy. Contrast-enhanced USG is being used for the assessment of inflammation and post-treatment changes. In this review, recent advances in intestinal imaging are described.

Comparison of neutral and positive enteral contrast media for MDCT enteroclysis

OBJECTIVE

To compare neutral and positive enteral contrast media for MDCT enteroclysis (MDCTE) in various small bowel diseases.

MATERIALS AND METHODS

40 patients with suspicion of small bowel diseases were divided randomly into two equal groups. In one group, water was used as neutral enteral contrast and in other group, 2% water soluble iodinated contrast was used as positive enteral contrast. All MDCTE were done on a 16-slice multidetector row CT unit. The findings of MDCTE were compared with the standards of reference.

RESULTS

There were 12 cases of abdominal tuberculosis (30%), 5 cases of bowel masses (12%), 4 cases of Crohn's disease (10%), 3 cases of small bowel adhesions (7%), 2 cases of midgut volvulus (5%), 2 cases of segmental enteritis (5%) and 12 of all cases (30%) were normal. There was no statistically significant difference between neutral and positive enteral contrast with regards to bowel distention, contrast reflux and evaluation of duodenum. Abnormal bowel wall enhancement was appreciated only with use of neutral enteral contrast (n=12). Evaluation of ileocaecal junction was possible in all 20 patients (100%) with positive enteral contrast but in only 17 patients (85%) with neutral enteral contrast. Overall sensitivity and specificity of MDCTE with use of neutral contrast medium (100 and 88% respectively) was greater for evaluation of small bowel diseases, when compared to MDCTE using positive enteral contrast medium (92.8 and 83.3% respectively).

CONCLUSIONS

Water is a good enteral contrast medium for MDCT enteroclysis examination and allows better evaluation of abnormal bowel wall enhancement. Ileocaecal junction evaluation is better with positive enteral contrast medium.

Imaging of malignant neoplasms of the mesenteric small bowel: new trends and perspectives

This article describes the recent advances in radiological imaging of malignant neoplasms of the mesenteric small bowel and provides an outline of new trends and perspectives that can be anticipated. The introduction of multidetector row technology, which allows the acquisition of submillimeter and isotropic voxels, has dramatically improved the capabilities of computed tomography in the investigation of the mesenteric small bowel. This technology combined with optimal filling of small bowel loops through the use of appropriate enteral contrast agents has markedly changed small bowel imaging. Computed tomography-enteroclysis, which is based on direct infusion of enteral contrast agent into the mesenteric small bowel through a naso-jejunal tube, provides optimal luminal distension. By contrast, computed tomography-enterography is based on oral administration of enteral contrast agent. These two techniques are now well-established ones for the detection and the characterization of small bowel neoplasms. During the same time, combining the advantages of unsurpassed soft tissue contrast and lack of ionizing radiation, magnetic resonance imaging has gained wide acceptance for the evaluation of patients with suspected small bowel neoplasms. Rapid magnetic resonance imaging sequences used in combination with specific enteral contrast agents generate superb images of the mesenteric small bowel so that magnetic resonance-enteroclysis and magnetic resonance-enterography are now considered as effective diagnostic tools for both the detection and the characterization of neoplasms of the mesenteric small bowel. Recent improvements in image post-processing capabilities help obtain realistic three-dimensional representations of tumors and virtual enteroscopic views of the small bowel that are useful for the surgeon and the gastroenteroenteologist to plan surgical or endoscopic interventions. Along with a better knowledge of the potential and limitations of wireless capsule endoscopy and new endoscopic techniques, these recent developments in radiological imaging reasonably suggest that substantial changes in the investigation of small bowel tumors may be anticipated in a near future, thus potentially create a new paradigm shift after standard small bowel follow-through study has been universally abandoned.

Frequency and nature of incidental extra-enteric lesions found on magnetic resonance enterography (MR-E) in patients with inflammatory bowel diseases (IBD)

Background

The aim of this study was to determine the occurrence of extra-enteric findings in a large cohort of patients undergoing magnetic resonance enterography (MR-E) and to classify the clinical significance of these findings.

Materials and Methods

We retrospectively analyzed 1154 MR-E performed in 1006 patients referred to our radiological department between 1999–2005. The reasons for referral were suspected or proven inflammatory bowel diseases (IBD) (n = 710), further diagnostic work-up for small bowel disease because of non-specific abdominal symptoms (SBD; n = 182) or suspected small bowel malignancies (SBM; n = 114). All extra-enteric findings were reviewed by a radiologist and a gastroenterologist and were classified as having high, moderate, or low significance for further diagnostic or therapeutic procedures.

Results

The average age of all patients was 40±16 (Mean±SD) years (y) (IBD 35±13 y; SBD 49±16 y; SBM 57±15 y). A total of 1113 extra-enteric findings were detected in 600 of 1006 patients (59.6%). Of these findings 180 (16.2%) were judged as having a high, 212 (19.0%) a moderate and 721 (64.8%) a low significance. On a per group basis in patients with IBD 12.0% of the findings were of major clinical significance compared to 13.7% and 33.3% in patients with SBD and SBM, respectively. The most common major findings were abscesses (69.9%) in the IBD group and extraintestinal tumors, metastases or masses in the SBD and SBM groups (41.9% and 74.2%, respectively).

Conclusions

MR-E reveals a substantial number of extra-enteric findings, supporting the role of a cross-sectional imaging method for the evaluation of the small bowel.

Hypotonic MR duodenography with water ingestion alone: feasibility and technique

To date, cross-sectional imaging of the duodenum has a number of inadequacies, most likely a reflection of its tortuous and complex anatomical course, resulting in somewhat suboptimal imaging. The purpose of this study was to describe and assess the feasibility of performing a 'tubeless', per-oral, single contrast, hypotonic magnetic resonance (MR) duodenography technique. Secondly, to assess the efficacy of intravenous Buscopan in facilitating duodenal distension at cross-sectional MR imaging. Ten healthy volunteers prospectively underwent MR imaging of the duodenum pre- and post-Buscopan immediately after consuming 1,000 ml of water. Images were qualitatively (using a visual assessment grading scale of 1-3) and quantitatively evaluated with regard to degree of small bowel distension by two observers. The contrast medium was successfully ingested and MR examination was completed in all participants. Quantitatively and qualitatively, the per-oral, hypotonic duodenography technique yielded superior distension scores and was significantly greater in diameter in comparison with the per-oral non-hypotonic duodenography technique (p < 0.003, p < 0.002). Per-oral, single-contrast, hypotonic MR duodenography is a feasible, simple, fast mode of investigation of the duodenum, which does not involve radiation and represents a useful technique in the armamentarium of the radiologist.

Quality, clinical influence and tolerance of computed tomography enteroclysis in patients with suspected small bowel disease

BACKGROUND

Computed tomography enteroclysis (CTE) may be superior to other small bowel imaging techniques, detecting subtle mucosal lesions and extraluminal pathology. This study aimed to define the technical success, clinical influence and tolerance of CTE in patients with suspected small bowel disease.

METHODS

CTE scans of 42 consecutive patients (aged 21-78 years, 12 men) were reviewed by a single radiologist for technical adequacy and diagnosis. A panel of gastroenterologists reviewed clinical information. At a telephone interview, tolerance of CTE was graded numerically from 1 (unbearable) to 10 (excellent) and descriptively as unbearable, fair, good or excellent.

RESULTS

Good or optimal distension of small bowel was achieved in 98%. The entire small bowel was imaged in 88%. Eighteen patients had a normal small bowel, whereas 12 (29%) had active small bowel Crohn disease, 4 intussusception, 3 small bowel diverticula and 7 having other diagnoses. Mesenteric lymphadenopathy was evident in 11 and fat stranding in 5. CTE resulted in a new or altered diagnosis in 13 (31%) patients and identified more extensive Crohn disease in a further 8 (19%). A change in management plan was instituted in 18 (43%) patients, with subsequent clinically significant improvement in 12. 33 (85%) described the procedure as 'fair' or 'unbearable' rather than 'good' or 'excellent'. The median tolerance score was 3 out of 10.

CONCLUSION

CTE provided high-quality images in nearly all patients and had an effect on diagnosis, management or outcome in most, but was not well tolerated.

Inflammatory bowel disease diagnosed with US, MR, scintigraphy, and CT: meta-analysis of prospective studies

PURPOSE

To compare, by performing a meta-analysis, the accuracies of ultrasonography (US), magnetic resonance (MR) imaging, scintigraphy, computed tomography (CT), and positron emission tomography (PET) in the diagnosis of inflammatory bowel disease (IBD).

MATERIALS AND METHODS

MEDLINE, EMBASE, CINAHL, and Cochrane databases were searched for studies on the accuracy of US, MR imaging, scintigraphy, CT, and PET, as compared with a predefined reference standard, in the diagnosis of IBD. Sensitivity and specificity estimates were calculated on per-patient and per-bowel-segment bases by using a bivariate random-effects model.

RESULTS

Thirty-three studies, from a search that yielded 1406 articles, were included in the final analysis. Mean sensitivity estimates for the diagnosis of IBD on a per-patient basis were high and not significantly different among the imaging modalities (89.7%, 93.0%, 87.8%, and 84.3% for US, MR imaging, scintigraphy, and CT, respectively). Mean per-patient specificity estimates were 95.6% for US, 92.8% for MR imaging, 84.5% for scintigraphy, and 95.1% for CT; the only significant difference in values was that between scintigraphy and US (P = .009). Mean per-bowel-segment sensitivity estimates were lower: 73.5% for US, 70.4% for MR imaging, 77.3% for scintigraphy, and 67.4% for CT. Mean per-bowel-segment specificity estimates were 92.9% for US, 94.0% for MR imaging, 90.3% for scintigraphy, and 90.2% for CT. CT proved to be significantly less sensitive and specific compared with scintigraphy (P = .006) and MR imaging (P = .037)

CONCLUSION

No significant differences in diagnostic accuracy among the imaging techniques were observed. Because patients with IBD often need frequent reevaluation of disease status, use of a diagnostic modality that does not involve the use of ionizing radiation is preferable.

MRI scoring system including dynamic motility evaluation in assessing the activity of Crohn's disease of the terminal ileum

RATIONALE AND OBJECTIVES

We sought to investigate the value of a MRI scoring system including dynamic motility evaluation in the assessment of small bowel Crohn's disease activity.

MATERIALS AND METHODS

From March 2005 to December 2006, 52 patients with suspected Crohn's disease onset or relapse underwent MRI on a 1.5-T magnet. Bowel distention was achieved orally assuming a mean of 1.6 L of a polyethyleneglycol (PEG) preparation. Per-patient assessment of disease activity was based on a scoring system including evaluation of morphology and motility of the small bowel and perivisceral structures (true-FISP, cine-true-FISP, and HASTE T2W sequences) and dynamic assessment of parietal contrast enhancement (FLASH T1W sequence). Patients were included in three categories, using endoscopic biopsy as the standard reference: no activity/quiescent disease, mild activity, or moderate-to-severe activity. Patients without terminal ileum involvement were excluded from data analysis.

RESULTS

MRI allowed a detailed and panoramic evaluation of the small bowel in all subjects examined. MRI properly assessed 14 of 16 (87.5%) cases of no activity/quiescent disease, 12 of 14 (85.7%) cases of mild activity, and 15 of 15 (100%) cases of severe activity. Overall, activity score led to a per-patient misdiagnosis of disease activity in a nonsignificant proportion of subjects (4 of 45; 8.8%) (P > .05), determining two false-positive and two false-negative results of mild disease activity. Sensitivity, specificity, PPV, NPV, and overall accuracy in assessing disease activity were 93.1%, 87.5%, 93.1%, 87.5%, and 91.1%, respectively.

CONCLUSION

Accurate assessment of Crohn's disease activity is achieved by using an activity score providing an overall interpretation of MRI findings.

Capsule enteroscopy and radiology of the small intestine

In a very few years, the video capsule for small bowel enteroscopy has gained widespread clinical acceptance. It is readily ingested, disposable, and allows for a complete, low-invasive endoscopic examination of the entire mucosa of the small bowel. It is a patient-friendly method and a first-line procedure in the difficult evaluation of obscure gastrointestinal bleeding. It has the highest proven figure of diagnostic sensitivity for detecting lesions of the mucosa, irrespective of aetiology. The limitations of capsule endoscopy include difficulty in localising mucosal lesions anatomically and its restricted use in patients with dysphagia, strictures or motor dysfunction. Strictures, transmural and extra-mural lesions in patients with small bowel Crohn's disease are evaluated by MRI- enterography and CT-enterography.

CT enteroclysis: techniques and applications

CT enteroclysis overcomes the individual deficiencies of both barium enteroclysis and conventional CT and combines the advantages of both into one technique whose clinical applicability has been simplified and made more reliable with multidetector CT technology. This article examines the techniques of CT enteroclysis and presents an overview of its clinical applications relative to other methods of small bowel imaging.

[CT enteroclysis: a pictorial essay]

The objective of the CT-enteroclysis is to distend the entire small intestine equally and sufficiently using a nasojejunal probe and an enteroclysis catheter for administration of a neutral opacifying agent. Today this is the best radiological method available to explore the small intestine because of its good spatial resolution and the rapidity of the exam. It is a high-performance exam when searching for transmural and extramural pathologies, in particular small tumoral lesions. It remains less effective in the exploration of anomalies of the lumen's mucosal lining, contrary to videocapsule endoscopy and the double-balloon enteroscope. It has been recognized that the CT-enteroclysis is a high-performance examination that should replace the small-bowel follow-through exam. However, there are undeniable disadvantages: higher does of radiation, patient discomfort during placement of the enteroclysis catheter, false-positive results, long interpretation time, and the impossibility of exploring the endoluminal aspect of the intestinal mucosal lining. All radiologists should therefore become familiar with the problems involved with this exam and its signs and patterns, which are illustrated in this pictorial review.

Enteroclysis in older children and teenagers

BACKGROUND

Enteroclysis (EC) has been widely and successfully used for evaluation of the small bowel in adults for about 30 years. However, despite recently improved intubation and examination techniques, in many paediatric radiology centres it is still not the preferred conventional barium study for the evaluation of small bowel pathology in children.

OBJECTIVE

To share our 10 years of experience and review the feasibility of EC in 83 older children and teenagers, in terms of both technique and pathological findings.

MATERIALS AND METHODS

Between 1996 and 2006, EC was performed by the standard technique described by Herlinger to 83 children between 7 and 18 years of age. The indication for the study was jointly decided by the paediatric radiologist and the clinician. None of the examinations was converted to follow-through studies because of patient refusal or technical failure. Morphological changes, mucosal abnormalities, luminal abnormalities, perienteric structures, the location of the disease, indirect findings regarding the bowel wall and functional information were evaluated.

RESULTS

All the children tolerated the procedure without difficulty. Out of 83 patients, 63 had abnormal findings. The spectrum of diagnoses were Crohn disease (n = 23), nonspecific enteritis (n = 10), malabsorption (n = 8), intestinal tuberculosis (n = 6), intestinal lymphoma (n = 5), Peutz-Jegher syndrome (n = 3), adhesions (n = 2), Behçet disease (n = 2), back-wash ileitis due to ulcerative colitis (n = 2), common-variable immune deficiency (n = 1) and lymphangiectasis (n = 1).

CONCLUSION

EC can easily be performed in children over 7 years of age and when performed using a correct technique it shows high diagnostic performance without any complications in the evaluation of small bowel diseases in older children and teenagers.

Assessment of colonic transit time using MRI: a feasibility study

The aim of this pilot study was to evaluate a new, non-invasive examination method using MRI for the quantification of the colonic transit time after oral administration of gadolinium-saline solution filled capsules. Healthy volunteers without previous or acute symptoms of gastrointestinal disorders were enrolled. After a 3-day diet for the standardization of gastrocolonic content the volunteers swallowed five Gd-DTPA/saline 0.9%-filled capsules. Seven different concentrations of Gd-DTPA/saline 0.9% solution between 1:0 and 0:1 were tested in a dilution series. Following ingestion of capsules, coronal Flash T1 and True Fisp sequences using a 1.5 Tesla system were obtained at 0 h, 3 h, 6 h, 12 h, 24 h, 36 h and 60 h. Sequences were analyzed by two independent experts for locating the capsules. Overall colonic transit time was separately analyzed for both genders. Fifteen healthy volunteers (7 females, 8 males; mean age 34+/-13 years) were enrolled. The phantom study provided the best contrast in both the T1-and T2-weighted sequences defining a ratio of 1:10 for Gd-DTPA/saline 0.9% solution. The mean transit time accounted for 41+/-9 h in women and for 31+/-10 h in men. MRI is an adequate method for the assessment of colonic transit time offering the advantages of no exposure to radiation, short examination time, possible dynamic evaluation of the transit and the practicability in terms of a future adoption to clinical routine.