MRI for small bowel diseases

MRI of the bowel - beyond inflammatory bowel disease

MR enterography is traditionally used to evaluate inflammatory bowel disease (IBD) both at initial presentation and at follow-up. MR enterography can also be used to evaluate non-IBD conditions such as polyps or other masses of the gastrointestinal tract. In this article, we emphasize how to recognize bowel conditions beyond IBD on conventional abdominal MRI without a specific enterographic technique. In this overview we discuss common and uncommon pediatric bowel conditions beyond IBD seen on MRI including infectious and inflammatory conditions, congenital diseases and tumor and tumor-like conditions. Radiologists should become familiar with the salient imaging features of these bowel conditions to help guide management.

Differential diagnosis of Crohn's disease versus ileal tuberculosis

Both intestinal tuberculosis and Crohn's disease are chronic granulomatous inflammatory diseases of the bowel having overlap of clinical, endoscopic, radiological, and histological features. Differentiating between the two disorders is relevant not only in Asian countries but also in the West. In spite of diagnostic criteria for both diseases being available, still the dilemma of segregating the two diseases remains. Nearly one third of the patients with Crohn's disease may receive anti-tuberculosis treatment also. Diagnosis should be based on the combination of all disease-specific and corroborative evidences.

Malignant small-bowel neoplasms: spectrum of disease on MR imaging

Malignant neoplasms of the small bowel are among the rarest types of cancer, accounting for only 2% of all gastrointestinal neoplasms. Owing both to the intrinsic difficulty of common radiographic and endoscopic methods in visualising the entire small bowel and the lack of typical physical findings, a delay in diagnosis is common. Recently, magnetic resonance (MR) imaging has become a widely accepted imaging modality in the study of suspected small-bowel neoplasms due to its ability to depict, without exposure to ionising radiation and with excellent soft-tissue contrast, intraluminal disorders in conjunction with mural, extraparietal and regional abnormalities. The aim of this pictorial review is to illustrate the MR appearance of malignant small-bowel neoplasms.

Differentiating intestinal tuberculosis from Crohn's disease: a diagnostic challenge

With the changing epidemiology of Crohn's disease (CD) and intestinal tuberculosis (ITB), we are in an era where the difficulty facing physicians in discriminating between the two diseases has increased, and the morbidity and mortality resulting from a delayed diagnosis or misdiagnosis is considerably high. In this article, we examine the changing trends in the epidemiology of CD and ITB, in addition to clinical features that aid in the differentiation of both diseases. The value of various laboratory, serological, and the tuberculin skin tests are reviewed as well. The use of an interferon-gamma-release assay, QuantiFERON-TB Gold, in the workup of these patients and its value in populations where the bacillus Calmette-Guérin vaccine is still administered is discussed. Different radiological, endoscopic, and pathological similarities and features that can aid the clinician in reaching a rapid diagnosis are reviewed as well. The association between mycobacteria and CD, the concerns with the practice of antituberculosis medication trials in areas where tuberculosis (TB) is endemic, as well as extrapulmonary TB induced by the use of antitumor necrosis factor-alpha agents are delineated in this article. Furthermore, we propose an algorithm for the investigation of patients in whom the differential diagnosis encompasses CD and ITB.

Evaluation of small bowel tumors: MR enteroclysis

Magnetic resonance imaging (MRI) of the small bowel has become widely accepted at centers dedicated to the diagnosis and treatment of inflammatory bowel disease, due to the method's diagnostic efficacy. MR enteroclysis is an imaging modality that combines the advantages of enteroclysis and multiplanar MR and allows the detection and the manifestations of small bowel diseases wherever they are located (intraluminal, intramural, or extramural). Magnetic resonance enteroclysis (MRE) is an emerging technique used for the detection and evaluation of small bowel neoplasms. This article illustrates the imaging appearances of small bowel tumors on MRI and the usefulness of MR enteroclysis in the diagnosis and categorization of these tumors, also discussing the role of MRE in comparison with other diagnostic modalities.

Diagnosis and staging of small bowel tumours

Small bowel neoplasms comprise only 1% of gastrointestinal neoplasms. Despite their rarity, it is important to diagnose small bowel tumours early to maximize patient survival.

Obscure gastrointestinal bleeding

Obscure GI bleeding is a relatively common problem facing internists, gastroenterologists, and surgeons in a typical clinical practice. The etiology is occasionally suggested by the patient's age, history, and medications. Management is complicated and typically requires a team-oriented approach, with input from the internist, gastroenterologist, radiologist, and surgeon alike. SBFT and enteroclysis seem to have a limited role, unless there is a high suspicion of a small bowel mass lesion or Crohn's disease. Scintigraphy may be performed in patients with active bleeding in whom endoscopy has failed oris contraindicated. Angiography may be used in patients with an early positive nuclear imaging or failed endoscopic therapy. Provocative angiography probably has a lower diagnostic yield than previously reported, and should be performed only in experienced centers. Helical CT is a new and potentially important option in patients with obscure bleeding, but is currently considered experimental. All patients with obscure GI bleeding should undergo repeat upper endoscopy and perhaps colonoscopy to rule out missed lesions. SBE seems to be complementary to capsule endoscopy, and it is unknown whether this should be performed before capsule endoscopy or only if capsule endoscopy yields a positive proximal small bowel finding. Double balloon enteroscopy seems promising, but the technique requires further study. Surgery should be reserved for patients who have a positive capsule endoscopy requiring surgical therapy or patients who have persistent GI bleeding requiring recurrent blood transfusions in whom all other modalities have failed. Treatment for vascularectasias, the most common cause of obscure GI bleeding, is currently inadequate,and typically requires a combination of multiple management approaches.

MR enteroclysis: imaging technique of choice in diagnosis of small bowel diseases

MR enteroclysis is becoming a very important imaging modality in the workup and follow-up of small bowel diseases. The technique has many advantages, including the absence of ionizing radiation, ability to control luminal distension, superior tissue characterization, multiplanar capabilities, and mural and extramural visualization. These capabilities can be obtained with a simple protocol showing excellent agreement with conventional enteroclysis. In 29 (18 with new or known Crohn's disease) of the 50 patients pathology was detected, with a very good clinical correlation. In 14 patients MR enteroclysis data altered the therapeutic strategy. This contributes to the acceptance of this modality as a primary tool in small bowel diseases.

GI carcinoid tumours: appearance of the primary and detecting metastases

Gastrointestinal carcinoid tumours are notoriously difficult to diagnose in the absence of the carcinoid syndrome. The clinical presentation is typically non-specific, and patients often go undiagnosed for years. Recent advances in computed tomography (CT), magnetic resonance (MR), endoscopic ultrasound, and nuclear scintigraphy have combined to improve the diagnosis and staging of this fascinating tumour. In this chapter the applications of cross-sectional imaging in patients with gastrointestinal carcinoid tumours is presented.