Imaging the small bowel

Small bowel adenocarcinoma of the jejunum detected by double contrast enhanced ultrasound: a case report of a novel ultrasound modality

Background

Small Bowel Adenocarcinoma (SBA) is rare, occult and life-threatening malignancy in digestive system. Given low incidence and nonspecific symptoms, SBA is frequently detected in later stages. Double contrast enhanced ultrasound (DCEUS) is an innovative imaging technique applied to visualize the gastrointestinal tract, merging intravenous contrast-enhanced ultrasound with oral contrast-enhanced ultrasound. In this case, DCEUS was utilized and successfully detected an SBA of the jejunum.

Case presentation

A Chinese woman, aged 64, sought consultation in the gastroenterology department at our hospital, reporting symptoms of abdominal pain. Three months before entering the hospital, she underwent gastroscopy and colonoscopy which suggested chronic gastritis, and she was treated with oral drugs. However, her symptoms were not relieved, and even worsened. To further investigate, DCEUS was performed. The oral contrast agent dilated the luminal space of the upper gastrointestinal tract, resolving the hindrance caused by gas in the gastrointestinal tract and creating an acoustic window for scanning. Through this acoustic window, oral agent contrast-enhanced ultrasound (OA-CEUS) revealed a localized thickening of jejunal intestinal wall measuring 4x3 cm. Following intravenous injection of ultrasound contrast agent, the jejunal lesion exhibited faster enhancement and heterogeneous hyper-enhancement. Finally, the patient underwent jejunal tumor resection. Pathological examination revealed a jejunal adenocarcinoma.

Conclusion

The timely diagnosis of SBA can be challenging. DCEUS may have the potential to contribute to diagnosis and detailed evaluation of SBA, particularly in cases involving jejunum. Further researches are needed to fully explore the benefits of DCEUS in the standard diagnostic approach for small bowel diseases.

Imaging spectrum of non-neoplastic and neoplastic conditions of the duodenum: a pictorial review

Given its crucial location at the crossroads of the gastrointestinal tract, the hepatobiliary system and the splanchnic vessels, the duodenum can be affected by a wide spectrum of abnormalities. Computed tomography and magnetic resonance imaging, in conjunction with endoscopy, are often performed to evaluate these conditions, and several duodenal pathologies can be identified on fluoroscopic studies. Since many conditions affecting this organ are asymptomatic, the role of imaging cannot be overemphasized. In this article we will review the imaging features of many conditions affecting the duodenum, focusing on cross-sectional imaging studies, including congenital malformations, such as annular pancreas and intestinal malrotation; vascular pathologies, such as superior mesenteric artery syndrome; inflammatory and infectious conditions; trauma; neoplasms and iatrogenic complications. Because of the complexity of the duodenum, familiarity with the duodenal anatomy and physiology as well as the imaging features of the plethora of conditions affecting this organ is crucial to differentiate those conditions that could be managed medically from the ones that require intervention.

Video Capsule Endoscopy Plays an Important Role in the Management of Crohn's Disease

Crohn's disease (CD) is a chronic inflammatory disorder characterized by a transmural inflammation that may involve any part of the gastrointestinal tract. An evaluation of small bowel involvement, allowing recognition of disease extent and severity, is important for disease management. Current guidelines recommend the use of capsule endoscopy (CE) as a first-line diagnosis method for suspected small bowel CD. CE has an essential role in monitoring disease activity in established CD patients, as it can assess response to treatment and identify high-risk patients for disease exacerbation and post-operative relapse. Moreover, several studies have shown that CE is the best tool to assess mucosal healing as part of the treat-to-target strategy in CD patients. The PillCam Crohn's capsule is a novel pan-enteric capsule which enables visualization of the whole gastrointestinal tract. It is useful to monitor pan-enteric disease activity, mucosal healing and accordingly allows for the prediction of relapse and response using a single procedure. In addition, the integration of artificial intelligence algorithms has showed improved accuracy rates for automatic ulcer detection and the ability to shorten reading times. In this review, we summarize the main indications and virtue for using CE for the evaluation of CD, as well as its implementation in clinical practice.

Optical tissue clearing associated with 3D imaging: application in preclinical and clinical studies

Understanding the inner morphology of intact tissues is one of the most competitive challenges in modern biology. Since the beginning of the twentieth century, optical tissue clearing (OTC) has provided solutions for volumetric imaging, allowing the microscopic visualization of thick sections of tissue, organoids, up to whole organs and organisms (for example, mouse or rat). Recently, tissue clearing has also been introduced in clinical settings to achieve a more accurate diagnosis with the support of 3D imaging. This review aims to give an overview of the most recent developments in OTC and 3D imaging and to illustrate their role in the field of medical diagnosis, with a specific focus on clinical applications.

GRAPH-BASED SMALL BOWEL PATH TRACKING WITH CYLINDRICAL CONSTRAINTS

We present a new graph-based method for small bowel path tracking based on cylindrical constraints. A distinctive characteristic of the small bowel compared to other organs is the contact between parts of itself along its course, which makes the path tracking difficult together with the indistinct appearance of the wall. It causes the tracked path to easily cross over the walls when relying on low-level features like the wall detection. To circumvent this, a series of cylinders that are fitted along the course of the small bowel are used to guide the tracking to more reliable directions. It is implemented as soft constraints using a new cost function. The proposed method is evaluated against ground-truth paths that are all connected from start to end of the small bowel for 10 abdominal CT scans. The proposed method showed clear improvements compared to the baseline method in tracking the path without making an error. Improvements of 6.6% and 17.0%, in terms of the tracked length, were observed for two different settings related to the small bowel segmentation.

A Graph-theoretic Algorithm for Small Bowel Path Tracking in CT Scans

We present a novel graph-theoretic method for small bowel path tracking. It is formulated as finding the minimum cost path between given start and end nodes on a graph that is constructed based on the bowel wall detection. We observed that a trivial solution with many short-cuts is easily made even with the wall detection, where the tracked path penetrates indistinct walls around the contact between different parts of the small bowel. Thus, we propose to include must-pass nodes in finding the path to better cover the entire course of the small bowel. The proposed method does not entail training with ground-truth paths while the previous methods do. We acquired ground-truth paths that are all connected from start to end of the small bowel for 10 abdominal CT scans, which enables the evaluation of the path tracking for the entire course of the small bowel. The proposed method showed clear improvements in terms of several metrics compared to the baseline method. The maximum length of the path that is tracked without an error per scan, by the proposed method, is above 800mm on average.

A novel food-based foam as oral contrast agent with negative Hounsfield units for demarcation of small bowel loops on abdominal CT: tolerability and bowel distension in 25 volunteers

BACKGROUND

Diseases of the bowel are not always displayed on conventional abdominal computed tomography (CT). The studied oral contrast agent aims to improve this.

PURPOSE

To investigate whether the use of a novel oral contrast for abdominal CT enables the same diagnostic advantages as seen in magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Twenty-five consented volunteers drank up to 1400 mL of a stable, drinkable foam. Comments on acceptance and side effects were noted immediately and 24 h later. Foam palatability was documented through interviews, and distribution in the small bowel by Hounsfield units from the CT software. The CT results were compared with age- and sex-matched controls, pretreated according to routine. A non-enhanced abdominal CT protocol of lowest possible radiation dose was used. External referees evaluated all data obtained.

RESULTS

Foam was considered odd to swallow, and fullness was reported by all volunteers after 950 mL. Five had difficulties in drinking the last 320 mL and two abstained from it. All adverse symptoms were mild. The distribution in the small bowel was on par with standard agents. Foam density revealed stability with intraluminal values of around -550 HU from stomach to terminal ileum, satisfying the requirement of a great bowel lumen-to-wall contrast. External reviewers re-evaluated all our data, and one predicted the foam to offer a potential for improved diagnostics.

CONCLUSION

A CT true-negative bowel filling agent was formulated, with high acceptance, few side effects, and a potential to mimic T1-weighted MRI images.

Capsule Endoscopy in Crohn's Disease-From a Relative Contraindication to Habitual Monitoring Tool

Crohn’s disease (CD) is a chronic inflammatory disorder that may involve the gastrointestinal tract from the mouth to the anus. Habitual disease monitoring is highly important during disease management, aiming to identify and treat disease exacerbations, in order to avoid immediate and future complications. Currently, ilio-clonoscopy is the gold standard for mucosal assessment. However, the procedure is invasive, involves sedation and allows for visualization of the colon and only a small part of the terminal ileum, while most of the small bowel is not visualized. Since CD may involve the whole length of the small bowel, the disease extent might be underestimated. Capsule endoscopy (CE) provides a technology that can screen the entire bowel in a non-invasive procedure, with minimal side effects. In recent years, this technique has gained in popularity for CD evaluation and monitoring. When CE was first introduced, two decades ago, the fear of possible capsule retention in the narrowed inflamed bowel lumen limited its use in CD patients, and a known CD located at the small bowel was even regarded as a relative contraindication for capsule examination. However, at present, as experience using CE in CD patients has accumulated, this procedure has become one of the accepted tools for disease diagnosis and monitoring. In our current review, we summarize the historic change in the indications and contraindications for the usage of capsule endoscopy for the evaluation of CD, and discuss international recommendations regarding CE’s role in CD diagnosis and monitoring.

Unsupervised Domain Adaptation for Small Bowel Segmentation using Disentangled Representation

We present a novel unsupervised domain adaptation method for small bowel segmentation based on feature disentanglement. To make the domain adaptation more controllable, we disentangle intensity and non-intensity features within a unique two-stream auto-encoding architecture, and selectively adapt the non-intensity features that are believed to be more transferable across domains. The segmentation prediction is performed by aggregating the disentangled features. We evaluated our method using intravenous contrast-enhanced abdominal CT scans with and without oral contrast, which are used as source and target domains, respectively. The proposed method showed clear improvements in terms of three different metrics compared to other domain adaptation methods that are without the feature disentanglement. The method brings small bowel segmentation closer to clinical application.

Deep Small Bowel Segmentation with Cylindrical Topological Constraints

We present a novel method for small bowel segmentation where a cylindrical topological constraint based on persistent homology is applied. To address the touching issue which could break the applied constraint, we propose to augment a network with an additional branch to predict an inner cylinder of the small bowel. Since the inner cylinder is free of the touching issue, a cylindrical shape constraint applied on this augmented branch guides the network to generate a topologically correct segmentation. For strict evaluation, we achieved an abdominal computed tomography dataset with dense segmentation ground-truths. The proposed method showed clear improvements in terms of four different metrics compared to the baseline method, and also showed the statistical significance from a paired t-test.

Low-Dose Computed Tomography for the Optimization of Radiation Dose Exposure in Patients with Crohn's Disease

Magnetic resonance imaging (MRI) is the mainstay method for the radiological imaging of the small bowel in patients with inflammatory bowel disease without the use of ionizing radiation. There are circumstances where imaging using ionizing radiation is required, particularly in the acute setting. This usually takes the form of computed tomography (CT). There has been a significant increase in the utilization of computed tomography (CT) for patients with Crohn's disease as patients are frequently diagnosed at a relatively young age and require repeated imaging. Between seven and eleven percent of patients with IBD are exposed to high cumulative effective radiation doses (CEDs) (>35–75 mSv), mostly patients with Crohn's disease (Newnham E 2007, Levi Z 2009, Hou JK 2014, Estay C 2015). This is primarily due to the more widespread and repeated use of CT, which accounts for 77% of radiation dose exposure amongst patients with Crohn's disease (Desmond et al., 2008). Reports of the projected cancer risks from the increasing CT use (Berrington et al., 2007) have led to increased patient awareness regarding the potential health risks from ionizing radiation (Coakley et al., 2011). Our responsibilities as physicians caring for these patients include education regarding radiation risk and, when an investigation that utilizes ionizing radiation is required, to keep radiation doses as low as reasonably achievable: the “ALARA” principle. Recent advances in CT technology have facilitated substantial radiation dose reductions in many clinical settings, and several studies have demonstrated significantly decreased radiation doses in Crohn's disease patients while maintaining diagnostic image quality. However, there is a balance to be struck between reducing radiation exposure and maintaining satisfactory image quality; if radiation dose is reduced excessively, the resulting CT images can be of poor quality and may be nondiagnostic. In this paper, we summarize the available evidence related to imaging of Crohn's disease, radiation exposure, and risk, and we report recent advances in low-dose CT technology that have particular relevance.

Intraluminal rectal cancer metastasis to the small bowel: An extremely rare case report

Prolonged survival in patients suffering from colorectal cancer (CRC) may lead to the emergence of rare metastatic sites that are not well-documented in the literature. We herein describe a very rare case of an intraluminal small intestinal metastasis in a patient with previously resected CRC. A 71-year-old Caucasian male patient with a history of rectosigmoid junction cancer was initially treated with anterior resection. The tumor was classified as pT3pN0 (0/26) M0, stage II. Eighteen months after the primary surgery, local recurrence was detected in the presacral region, and the patient received combined image-guided radiotherapy and chemotherapy. Two months later, due to residual disease at the level of the anastomosis, the patient underwent additional low anterior resection with a diverting stoma. During extensive adhesiolysis, a small palpable intraluminal mass was identified in the jejunum, and segmental small bowel resection was performed. Pathological examination of the resected specimen confirmed that the lesion was a metastasis from the CRC primary. The precise mechanism and clinical significance of CRC metastasis to the small bowel remain unclear. There is limited clinical experience with this condition, as <20 cases have been reported in the literature to date. The main symptoms leading to evaluation, diagnosis and surgical resection are bowel obstruction and bleeding. The present case highlights the possibility of uncomplicated presence of metastatic CRC in the small bowel. Therefore, dilligent inspection of the peritoneal cavity, including the entire length of the gastrointestinal canal, is of paramount importance, particularly in cases of recurrent CRC.

Enteroscopy and radiology for the management of celiac disease complications: Time for a pragmatic roadmap

Celiac disease is the most common autoimmune enteropathy in Western countries, and is usually associated with a good response to the gluten free diet and an excellent prognosis. However, a minority of patients develop complications of the disease, such as refractory celiac disease, ulcerative jejunoileitis and neoplastic complications such as adenocarcinoma of the small bowel and enteropathy associated T cell lymphoma. Neoplastic complications described in association with celiac disease have a high mortality rate, due to their aggressive behavior and to the usual advanced stage at the time of diagnosis. In recent years, the detection of small bowel lesions has dramatically improved thank to the availability of highly performing radiologic and endoscopic techniques. The diagnostic delay of malignant complications in patients with celiac disease may be improved by establishing a pragmatic flowchart for the identification and follow up of "at risk" patients. We performed a comprehensive review of the articles published on this issue in order to promote a roadmap to be applied when facing with celiac patients with suspected small bowel complications.

MRI for Crohn's Disease: Present and Future

Crohn's disease (CD) is a chronic inflammatory condition with relapsing-remitting behavior, often causing strictures or penetrating bowel damage. Its lifelong clinical course necessitates frequent assessment of disease activity and complications. Computed tomography (CT) enterography has been used as primary imaging modality; however, the concern for radiation hazard limits its use especially in younger population. Magnetic resonance (MR) imaging has advantages of avoiding radiation exposure, lower incidence of adverse events, ability to obtain dynamic information, and good soft-tissue resolution. MR enterography (MRE) with oral contrast agent has been used as primary MR imaging modality of CD with high sensitivity, specificity, and interobserver agreement. The extent of inflammation as well as transmural ulcers and fibrostenotic diseases can be detected with MRE. Novel MR techniques such as diffusion-weighted MRI (DWI), motility study, PET-MRI, and molecular imaging are currently investigated for further improvement of diagnosis and management of CD. MR spectroscopy is a remarkable molecular imaging tool to analyze metabolic profile of CD with human samples such as plasma, urine, or feces, as well as colonic mucosa itself.