The Role of Magnetic Resonance Enterography in Crohn’s Disease: A Review of Recent Literature

Inflammatory bowel disease (IBD) is the term used to identify a form of chronic inflammation of the gastrointestinal tract that primarily contemplates two major entities: ulcerative colitis (UC) and Crohn’s disease (CD). The classic signs are abdominal pain and diarrhoea that correlate with the localization of gastro-enteric disease, although in this pathology extraintestinal symptoms may coexist. The diagnosis of CD relies on a synergistic combination of clinical, laboratory (stool and biochemical), cross-sectional imaging evaluation, as well as endoscopic and histologic assessments. The purpose of this paper is to prove the role of imaging in the diagnosis and follow-up of patients with CD with particular focus on recent innovations of magnetic resonance enterography (MRE) as a pivotal diagnostic tool, analysing the MRE study protocol and imaging features during the various phases of disease activity and its complications.

Gastrointestinal Manifestations of Immunodeficiency: Imaging Spectrum

There is a wide spectrum of hereditary and acquired immunodeficiency disorders that are characterized by specific abnormalities involving a plethora of humoral, cellular, and phagocytic immunologic pathways. These include distinctive primary immunodeficiency syndromes due to characteristic genetic defects and secondary immunodeficiency syndromes, such as AIDS from HIV infection and therapy-related immunosuppression in patients with cancers or a solid organ or stem cell transplant. The gut mucosa and gut-associated lymphoid tissue (the largest lymphoid organ in the body), along with diverse commensal microbiota, play complex and critical roles in development and modulation of the immune system. Thus, myriad gastrointestinal (GI) symptoms are common in immunocompromised patients and may be due to inflammatory conditions (graft versus host disease, neutropenic enterocolitis, or HIV-related proctocolitis), opportunistic infections (viral, bacterial, fungal, or protozoal), or malignancies (Kaposi sarcoma, lymphoma, posttransplant lymphoproliferative disorder, or anal cancer). GI tract involvement in immunodeficient patients contributes to significant morbidity and mortality. Along with endoscopy and histopathologic evaluation, imaging plays an integral role in detection, localization, characterization, and distinction of GI tract manifestations of various immunodeficiency syndromes and their complications. Select disorders demonstrate characteristic findings at fluoroscopy, CT, US, and MRI that permit timely and accurate diagnosis. While neutropenic enterocolitis affects the terminal ileum and right colon and occurs in patients receiving chemotherapy for hematologic malignancies, Kaposi sarcoma commonly manifests as bull's-eye lesions in the stomach and duodenum. Imaging is invaluable in treatment follow-up and long-term surveillance as well. Online supplemental material is available for this article. ^©RSNA, 2022.

Imaging in Diagnosis of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease characterized by fibrosis in skin and internal organs, progressive vascular obliteration, and the production of autoantibodies. Diagnostic imaging is irreplaceable in both diagnosing and monitoring patients suffering from systemic sclerosis. In addition to routinely used methods, such as comparative X-ray of the hands or a contrast-enhanced examination of the upper gastrointestinal tract or chest, there is an array of less widespread examinations, with an emphasis on magnetic resonance imaging (MRI) and ultrasonography, not only in the evaluation of the musculoskeletal system. This article will review the various imaging modalities available for SSc imaging and assessment, focusing on their utility as tissue-specific diagnosis and treatment monitoring.

Unravelling the Mysteries of the Mesentery

The mesentery and its folds tether the small bowel loops to the posterior abdominal wall. It transmits nerves, vessels, and lymph ensconced in a fatty sponge layer wrapped in a thin glistening peritoneum, from and to the small bowel. Not only does this flexible dynamic fatty apron house various localized primary benign and malignant lesions, it is often involved in and gives an indication of generalized or systemic diseases in the body. An understanding of the anatomy, components, and function of the mesentery helps to classify mesenteric abnormalities. This further allows for characterizing radiological patterns and appearances specific to certain disease entities. Recent reviews of mesenteric anatomy have kindled new interest in its function and clinical applications, heralding the possibility of revision of its role in diseases of the abdomen.

Diagnosis of Bleeding Meckel's Diverticulum in Adults

BACKGROUND AND AIMS

Various modalities have been used to diagnose Meckel's diverticulum (MD) in practice, but with their diagnostic accuracy deemed to be unsatisfactory for clinical practice. Moreover, the usefulness of these modalities has not been evaluated for the diagnosis of bleeding MD in adults, due to the relative rarity of this condition. Therefore, the aim of our multicenter study was to determine the most accurate modality for the preoperative diagnosis of bleeding MD in adults.

METHODS

We conducted a retrospective analysis of the diagnostic accuracy for small bowel bleeding associated with MD of different modalities in patients ≥18 years old who underwent assessment for MD, with confirmation at the time of explorative surgery. Diagnostic accuracy of the different modalities was evaluated against the diagnosis obtained using technetium-99m pertechnetate scintigraphy (also known as Meckel's scan), considered to be the gold standard for the diagnosis of bleeding MD in pediatrics.

RESULTS

Thirty-five adults were identified with bleeding in MD over the study period, between 2005 and 2012. Among these patients, only 24 (68.6%) were diagnosed with MD preoperatively. The mean (95% confidence interval) diagnostic accuracy of selected modalities was as follows: Meckel's scan, 21.4% (5.7%-51.2%); capsule endoscopy, 35.7% (14.0%-64.4%); balloon-assisted enteroscopy (BAE), 85.0% (61.1%-96.0%); angiography, 0.0% (0.0%-80.2%); computed tomography, 31.8% (14.7%-54.9%); and small-bowel follow-through, 62.5% (25.9%-90.0%). The diagnostic accuracy was significantly higher for BAE than for Meckel's scan (P = 0.001).

CONCLUSIONS

Among available diagnostic modalities, BAE provides the highest accuracy for the diagnosis of bleeding MD in adults and, therefore, should be considered as the preferred modality for preoperative diagnosis.

Abdominal manifestations of histiocytic disorders in adults: imaging perspective

Histiocytic disorders (HDs) are a diverse group of diseases characterized by pathologic infiltration of normal tissues by cells of the mononuclear phagocyte system. The spectrum of these diseases ranges from treatable infectious diseases to rapidly progressive, life-threatening conditions. Although they are rare and difficult diagnoses, HDs can be diagnosed with the help of clinical and laboratory analyses, imaging features and tissue biopsy. The clinicopathology and imaging spectrum of select entities belonging to this disorder are presented in this review.

Gastrointestinal manifestations of systemic disease: a multimodality review

Systemic diseases have many different presentations, including imaging findings in the bowel. Recognizing the imaging findings in these diseases is important in making the correct diagnosis. Although certain imaging features overlap, knowledge of specific findings along with the clinical presentation aid in narrowing the differential or in making an imaging diagnosis. The pictorial review will focus on the gastrointestinal manifestations of systemic diseases, including amyloidosis, angiotensin converter enzyme inhibitor-induced angioedema, celiac sprue, distal intestinal obstruction syndrome, graft-versus-host disease, hemolytic uremic syndrome, hemophilia, Henoch-Schönlein purpura, intestinal lymphangiectasia, mastocytosis, scleroderma, systemic lupus erythematosus, Wegener's granulomatosis, and Whipple's disease. The aforementioned diseases can be subdivided based upon the underlying process leading to the disease. The diseases discussed are categorized into autoimmune, infiltrative, treatment related, congenital/hereditary, and infectious etiologies.

Radiologic manifestations of angioedema

OBJECTIVES

The purpose of this pictorial review is to present imaging findings of angioedema involving the various organs.

CONCLUSION

The role of imaging for patients with angioedema includes the evaluation of the upper airway for obstruction and the exclusion of other possible aetiologies, such as neoplastic or infectious processes. Glossomegaly is a common finding of head and neck angioedema. Angioedema may involve organ systems beyond the superficial regions and the head and neck including the gastrointestinal and genitourinary tracts. Angioedema of the visceral organs is often accompanied by adjacent fluid, and it is commonly diffuse or concentric but can also be multifocal and asymmetric.

TEACHING POINTS

• The evaluation of the upper airway obstruction is important for head and neck angioedema. • Glossomegaly with decreased attenuation is common in head and neck angioedema. • Angioedema of the visceral organs can be multifocal and asymmetric. • Angioedema of the visceral organs is often accompanied by adjacent fluid. • It is important to include clinical and laboratory findings for the diagnosis of angioedema.

Mucosal microfolds augment mixing at the wall of the distal ileum of the brushtail possum

BACKGROUND

Recent work suggests that mixing in the small intestine takes place in central luminal and peripheral compartments. However, while movements of villi have been described, the mechanisms by which peripheral mixing are engendered remain unclear.

METHODS

We examined the disposition and movement of mucosa and associated villi during contractions of the everted terminal ileum of the brushtail possum. We then simulated the effect of these movements on peripheral mixing.

KEY RESULTS

Compression of the intestinal mucosa by phasic longitudinal or radial contractions created short-lived microfolds, which were of similar scale to the attached villi. The packing density of the villous tips increased in the concavities and decreased on the crests of these microfolds. Simulations showed that these caused liquid digesta to be expelled from, or drawn into, intervillous spaces, significantly augmenting peripheral, but not bulk, luminal mixing.

CONCLUSIONS & INFERENCES

We describe a mechanism by which peripheral mixing may be engendered by mucosal microfolds without requiring the coordinated contraction of individual villi or groups of villi.

Imaging of scleroderma

Systemic sclerosis is a rare autoimmune condition that affects a variety of organ systems. Knowledge of the imaging features in this patient population is essential in facilitating accurate diagnosis and guiding treatment. Common and rare imaging features of systemic sclerosis are reviewed in this article. Skin, musculoskeletal, pulmonary, cardiac, gastrointestinal, renal, and oral imaging are discussed. Conventional radiography, computed tomography of the chest, echocardiography, enterography, scintigraphy, and panorex dental imaging are reviewed. In addition, the evolving applications of ultrasonography and magnetic resonance imaging to evaluate the musculoskeletal and cardiac features of systemic sclerosis are discussed.

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.

Peritoneal Bands: A Review of Anatomical Distribution and Clinical Implications

The complexity of embryological development of the gastrointestinal tract and mesentery provides a platform for the formation of a wide variety of variant veils, folds, and membranes, collectively termed peritoneal bands. These structures, which represent anatomically unabsorbed portions of the omentum and mesentery, although often benign, have the potential to cause clinically significant manifestations in both the neonate and adult. Although these deviant structures may be identified over a broad range of the abdominal cavity, they are most commonly identified in the regions of the duodenum, duodenojejunal flexure, ileocecal junction, and ascending colon. As a result of the diverse location of these variant structures, clinical manifestations are highly variable, ranging from acute presentations of intestinal necrosis as a result of strangulated midgut volvulus to chronic, vague abdominal pain. This article seeks to highlight the importance of a thorough anatomical understanding of the distribution of the various abnormal peritoneal folds, bands, and ligaments, which may result from aberrations in embryonic gastrointestinal development and their respective clinical implications. Moreover, to advance the knowledge of peritoneal bands, this article discusses the appropriate diagnostic studies and treatment interventions required for these variant structures.

Giant Diverticulum of the Duodenum

A 50-year old female presented herself with abdominal bloating and pain in the Emergengy Department. The symptoms persisted and a clinical evaluation was made. A lesion suspect for a giant duodenal diverticulum was seen on the CT-scan, which was confirmed by enteroclysis. Surgical resection was performed. The diagnosis was histological confirmed after surgery. Small bowel diverticula are relatively common, with an estimated 5 - 22% incidence in the healthy population. They are usually asymptomatic, but can present with abdominal pain and weight loss. Complications such as bleeding and perforation can occur. Surgical resection is the treatment of choice in symptomatic patients.

Avaliação e seguimento de pacientes adultos com síndrome do intestino curto pelo exame contrastado de trânsito intestinal

A síndrome do intestino curto é definida pela incapacidade da superfície do intestino delgado em manter as condições adequadas de absorção de nutrientes, ocasionando deficiências nutricionais. Em adultos, as principais causas de síndrome do intestino curto são as ressecções cirúrgicas amplas ou múltiplas, secundárias a infarto mesentérico, doença de Crohn e enterite actínica. Além de avaliar o tempo de trânsito até o intestino grosso, o exame contrastado de trânsito intestinal pode ser utilizado na medição da extensão do intestino remanescente e no acompanhamento dos fenômenos de adaptação estrutural das alças delgadas e colônicas. Em pacientes com síndrome do intestino curto, a adaptação estrutural do intestino delgado consiste na hiperplasia das vilosidades e das pregas mucosas, que se tornam mais numerosas, profundas e de maior diâmetro, assim como a dilatação do segmento remanescente. Esses achados morfológicos são mais pronunciados e bem estabelecidos nas alças ileais, evidenciando sua maior capacidade adaptativa. O conhecimento dos achados por imagem das características morfológicas e adaptativas do intestino delgado é de grande importância na abordagem multidisciplinar da síndrome do intestino curto.

Intestinal lymphangiectasia mimicking primary peritoneal carcinoma

Intestinal lymphangiectasia is an obstruction of the lymphatic system. We report on a patient with mesenteric adenopathy and an elevated CA125 level, which were suspicious for peritoneal carcinoma. Further evaluation and bowel resection identified intestinal lymphangiectasia. This disease should be considered in patients with mesenteric adenopathy and a small bowel mass.

Enteroscopy and its relationship to radiological small bowel imaging

The field of radiological small bowel imaging is changing rapidly, as is small bowel enteroscopy. New techniques allow the depiction of intraluminal, mural, and extraintestinal features of various small bowel disorders, such as Crohn disease, small bowel polyposis syndromes, small intestinal malignancies, and celiac disease. For patients requiring repeated small bowel imaging, modalities that do not use ionizing radiation, such as ultrasound or magnetic resonance imaging, should be considered.