The Role of Ultrasound in the Evaluation of Inflammatory Bowel Disease

Treat to transmural healing: how to incorporate intestinal ultrasound into the treatment of inflammatory bowel disease

Intestinal ultrasound (IUS) is emerging as a key tool to achieving the therapeutic target of transmural healing in inflammatory bowel disease (IBD). IUS is a non-invasive, radiation-free, imaging modality comparable to MRI, CT and ileocolonoscopy (IC). With the appropriate training and equipment, IUS can be an easily repeatable bedside test for IBD diagnosis and disease monitoring, including treatment response. Core to successful high quality IUS employment are appropriate training and expert techniques; however, the training pathway will not be explored in this review. Given the increasing shift towards objective assessment for tight disease control, gastroenterologist-led IUS should be incorporated into the armamentarium of imaging modalities alongside radiologists, to enhance our diagnostic and monitoring toolbox. This comprehensive review aims to outline the current literature around IUS and propose the placement of IUS in a treat-to-target algorithm in IBD. Ultimately, IUS facilitates timely management decisions to optimise patient care with potential to revolutionise patient outcomes, moving towards transmural healing as the holy grail of therapy in IBD.

Application of transabdominal ultrasound in Crohn's disease

Crohn's disease (CD), a chronic nonspecific intestinal inflammatory disorder of uncertain origin, is collectively referred to as inflammatory bowel disease with ulcerative colitis. In recent years, with the increasing incidence of CD, a greater demand has been put forward for disease diagnosis and inflammatory activity monitoring. With the development of ultrasound technology, transabdominal ultrasound has become more relevant for the diagnosis and follow-up of CD, providing an effective non-invasive examination tool for patients. This review summarizes several transabdominal ultrasound modalities and associated techniques that are presently being developed and utilized in clinical practice, describes the ultrasound manifestations of CD, and discusses the value and prospect of transabdominal ultrasonography in CD.

ACR Appropriateness Criteria® Crohn Disease

Three common clinical scenarios involving use of imaging in Crohn disease are covered. These include the initial evaluation of Crohn disease when the diagnosis has not been previously established, the evaluation for anticipated exacerbation of known disease, and the evaluation of disease activity during therapy monitoring. The appropriateness of a given imaging modality for each scenario is rated as one of three categories (usually appropriate, may be appropriate, usually not appropriate) to help guide evaluation. Pediatric presentation of Crohn disease and the appropriateness of imaging are not covered in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Bowel Ultrasound State of the Art: Grayscale and Doppler Ultrasound, Contrast Enhancement, and Elastography in Crohn Disease

Bowel ultrasound (US) is accurate for assessing bowel inflammation and complications in Crohn disease. Additionally, contrast-enhanced US provides a quantitative, objective measurement of inflammatory activity in inflammatory bowel disease, and shear wave elastography predicts the stiffness of bowel, an increase of which suggests less response to medical therapy, often necessitating surgery. Overall, bowel US is an excellent, safe, and repeatable choice for routine surveillance and for urgent imaging. We describe an approach to evaluating inflammatory bowel disease and review its features on standard grayscale US with Doppler imaging and show how contrast-enhanced US and shear wave elastography can distinguish between inflammatory and fibrostenotic bowel.

Ultrasound Shear Wave Elastography and Contrast Enhancement: Effective Biomarkers in Crohn's Disease Strictures

BACKGROUND

Inflammation, fibrosis, and muscular hypertrophy lead to thickened bowel in Crohn's disease forming strictures. Ultrasound shear wave elastography (SWE) measures bowel wall stiffness. Contrast-enhanced ultrasound (CEUS) uniquely detects bowel wall inflammation. We aim to correlate SWE of ileal Crohn's disease in vivo to CEUS peak enhancement and pathology grades of inflammation, fibrosis, and muscular hypertrophy.

METHODS

In a prospective institutional review board-approved study, 105 consecutive ileal patients with Crohn's disease received ultrasound. At maximal bowel wall thickness (>4 mm), SWE and CEUS were performed. Fifteen patients had ileal resection within a mean time interval of 71.0 ± 66.9 days. Pathology scores for inflammation, fibrosis, and muscular hypertrophy were compared with SWE and CEUS measurements.

RESULTS

Mean in vivo SWE velocity for patients with and without surgery was 2.8 ± 0.7 and 2.2 ± 0.8 m/s (P < 0.01), respectively. In all ileal specimens, chronic exceeded active inflammatory change (P < 0.001). There was an inverse relationship between CEUS peak enhancement and both fibrosis, r = -0.59, P = 0.02, and SWE velocity measurements, r = -0.61, P = 0.03. Strictured bowel specimens had more smooth muscle hypertrophy than fibrosis, P < 0.001. There was moderate correlation between SWE and muscular hypertrophy, r = 0.59, P = 0.02 and no significant relationship between SWE and fibrosis scores (P > 0.05).

CONCLUSIONS

Stiffer bowel from smooth muscle hypertrophy increases SWE measurements. We report a novel relation of high SWE with muscle hypertrophy, and inverse relationship with CEUS peak enhancement; providing differentiation between active and chronic bowel wall inflammation to improve selection between medical therapy and surgery.

ACR Appropriateness Criteria Crohn Disease

Crohn disease is a chronic inflammatory disorder involving the gastrointestinal tract, characterized by episodic flares and times of remission. Underlying structural damage occurs progressively, with recurrent bouts of inflammation. The diagnosis and management of this disease process is dependent on several clinical, laboratory, imaging, endoscopic, and histologic factors. In recent years, with the maturation of CT enterography, and MR enterography, imaging has played an increasingly important role in relation to Crohn Disease. In addition to these specialized examination modalities, ultrasound and routine CT have potential uses. Fluoroscopy, radiography, and nuclear medicine may be less beneficial depending on the clinical scenario. The imaging modality best suited to evaluating this disease may change, depending on the target population, severity of presentation, and specific clinical situation. This document presents seven clinical scenarios (variants) in both the adult and pediatric populations and rates the appropriateness of the available imaging options. They are summarized in a consolidated table, and the underlying rationale and supporting literature are presented in the accompanying narrative. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Considerations in Imaging Among Emergency Department Patients With Inflammatory Bowel Disease

Patients with inflammatory bowel disease who experience abdominal pain and gastrointestinal symptoms often seek care in the emergency department (ED). These patients commonly undergo abdominopelvic computed tomography (CT) as part of their evaluation, and the rate of imaging appears to be increasing without a corresponding increase in identification of clinically actionable findings or effect on disposition. Studies demonstrate that the yield of CT tends to be fairly high. Yet, because inflammatory bowel disease is often diagnosed at an early age, these patients are repeatedly imaged during their lifetime, a subset of whom accumulate high levels of ionizing radiation exposure, increasing their risk of cancer. This compounds an already increased risk of cancer in these patients because of inflammatory bowel disease alone. Lack of intimate knowledge of a patient's disease phenotype and disease progression contributes to uncertainty in distinguishing between an inflammatory exacerbation; a complication such as obstruction, abscess, perforation, fistula, or stricture; and a noninflammatory-bowel-disease-related condition. This uncertainty can lead to overuse of imaging with CT. Limited availability of and lack of awareness of alternate imaging modalities and strategies may prevent providers from pursuing strategies that avoid ionizing radiation. In this article, we review options for imaging inflammatory bowel disease patients in the ED and attempts undertaken to risk stratify these patients, and we discuss ways in which details of a patient's disease might guide imaging decisionmaking.

Pediatric inflammatory bowel disease: imaging issues with targeted solutions

To date, there have been many advances in inflammatory bowel disease (IBD) imaging in every cross-sectional imaging modality, particularly in children. The main emphasis in pediatric IBD imaging is on robust and reproducible measures of small bowel Crohn's disease inflammation, accurate diagnosis of IBD-related complications, and minimizing radiation burden to the patient, as repeat imaging is necessary over the course of their disease. In this article, we discuss the current state-of-the-art imaging techniques, in addition to routine fluoroscopy, including MR and CT enterography and bowel ultrasound. We also present the emerging use of new methods to characterize disease severity and distinguish active inflammation from fibrosis such as diffusion-weighted imaging, bowel elastography, and contrast-enhanced ultrasound. The diagnostic performance of particular examinations, their strengths and weaknesses, and role in IBD management will be discussed. Although these advanced imaging techniques applied to children are similar to those performed in adults, special considerations related to their application in pediatric patients will also be reviewed.

Impact of Intestinal Ultrasound on Classification and Management of Crohn's Disease Patients with Inconclusive Colonoscopy

Background and Aims. We aim to evaluate the benefit of ultrasound in the assessment of Crohn's disease and to demonstrate its potential contribution to disease management. Methods. We conduct a retrospective review of adult patients with Crohn's disease examined with sonography and colonoscopy within 30 days. Study patients were identified in whom colonoscopy did not access a pathological segment, detected and evaluated by ultrasonography. Changes in management were predominantly attributed to ultrasound in those cases where the diseased segment was not assessed on endoscopy. Results. From 115 patients with temporally related ileocolonoscopy and ultrasound, 41 had disease fully assessed on ultrasound only, with complications in 26/41. Twenty-nine of 41 had mild or no endoscopic inflammation with moderate or severe disease on ultrasound at the same segment or at a segment proximal to the reach of the endoscope. Changes in management were significantly attributed to ultrasound in 22 of these 29 patients. Conclusion. The benefit of cross-sectional imaging is invaluable for the comprehensive assessment of bowel not shown on ileocolonoscopy. Ultrasound may make a significant contribution to correct classification of disease extent and severity of Crohn's disease. Prospective studies are needed to further understand the contribution of US in patient management.

Clinic-based Point of Care Transabdominal Ultrasound for Monitoring Crohn's Disease: Impact on Clinical Decision Making

BACKGROUND AND AIMS

The use of cross-sectional imaging is important to characterise inflammatory bowel disease [IBD] activity, extent, and location and to exclude complications, regardless of symptoms. The aim of this study was to evaluate the impact of routine use of sonography in the management of inflammatory bowel disease.

METHODS

A total of 49 patients with Crohn's disease were prospectively evaluated. Clinical symptoms (Harvey-Bradshaw Index [HBI]), disease character, serological markers of inflammation [C-reactive protein], and endoscopic evaluation were collected and reviewed by two independent IBD-specialty physicians. Clinical decisions regarding management were recorded. A separate, blinded physician then performed bowel ultrasound [US] and graded disease activity:] as inactive, mild, or active. A second blinded physician read and graded a sub-set of the US images. Clinical decisions of both IBD-physicians after US were independently recorded. Changes in clinical management following US information and inter-rater agreement on US disease activity parameters were evaluated. The concordance between US, CRP and clinical symptoms [HBI] were analysed. Follow-up data after US evaluation were collected.

RESULTS

Clinical decisions were changed after ultrasound assessment in 30/49 [60%] and 28/48 [58%] of cases, for each physician respectively [p < 0.0001 for each]. Many [59%] of the patients seen in clinic were asymptomatic with an HBI of 3 or less [n = 29]; however, 52% [n = 15] of these had active disease found on US, resulting in alterations in clinical management. The agreement in overall score between the US reviewers was good, ĸ = 0.749 [0.5814, 0.9180], p < 0.001.

CONCLUSIONS

Clinic-based point of care US can play a significant role in guiding therapeutic management and is an important adjunct to routine clinical and laboratory assessment.

Growing indications for CEUS: The kidney, testis, lymph nodes, thyroid, prostate, and small bowel

Contrast enhanced ultrasonography (CEUS) is increasingly used for non-hepatic applications as well, so that nearly all organs have been investigated. Among them, there is a growing clinical use for a variety of pathologies of the kidney, testis, and small bowel. The possibility to differentiate benign from malignant nodes in cancer patients has been investigated. A new application is in the detection of sentinel nodes after intradermal microbubble injection. The need to distinguish thyroid nodules eligible for fine needle aspiration cytology has led to the use of CEUS in thyroid examinations as well. The potential of CEUS for prostate cancer detection has been extensively investigated, with encouraging initial results. Early promise, however, has not been fulfilled. New perspective regards evaluation of the extent of prostate tissue devascularization following ablative treatments.

Gut and mesenteric lymph node involvement in pediatric patients infected with human immunodeficiency virus

Background

The gastrointestinal tract is a primary target for human immunodeficiency virus (HIV). HIV infection causes a depletion of CD4+ T-lymphocytes in gut-associated lymphoid tissue and affects gastrointestinal mucosal integrity and permeability. The gastrointestinal tract has also been suggested as the main reservoir of HIV despite highly active antiretroviral therapy (HAART). We performed a prospective case-control study to assess gut involvement in HIV-infected patients, either naïve or on HAART, using noninvasive methods such as bowel ultrasound and fecal calprotectin.

Methods

Thirty HIV-infected children and youth underwent the following tests: CD4+ T-cell count and HIV viral load, fecal calprotectin, and bowel ultrasound, with the latter evaluating bowel wall thickness and mesenteric lymph nodes. Fecal calprotectin and bowel ultrasound were also assessed in 30 healthy controls matched for age and sex. Fecal calprotectin was measured using a quantitative immunochromatographic point-of-care test, and concentrations ranging from 0 to 200 μg/g were considered to be normal reference values in children.

Results

Fecal calprotectin was normal in 29 HIV-infected patients and was not significantly different from controls (mean values 63.8±42.5 μg/g and 68.3±40.5 μg/g, respectively; P=0.419), and did not correlate with HIV viral load, CD4+ T-cell absolute count and percentage, or HAART treatment. No significant changes were found on bowel ultrasound except for enlarged mesenteric lymph nodes, which were observed in seven HIV-infected patients (23.3%) and two controls (6.6%). This finding was significantly correlated with high HIV viral load (P=0.001) and low CD4+ T-cell percentage (P=0.004).

Conclusion

HIV-infected children did not have significant biochemical or ultrasonographic signs of bowel inflammation. A few patients showed enlarged mesenteric lymph nodes, which correlated with uncontrolled HIV infection.

Fibrogenesis and fibrosis in inflammatory bowel diseases: Good and bad side of same coin?

Fibrogenesis in inflammatory bowel diseases is a complex phenomenon aimed at mucosal repair. However, it may provoke intestinal fibrosis with the development of strictures which require surgery. Therefore, fibrogenesis may be considered as a “two-faced” process when related to chronic intestinal inflammation. Many types of cells may be converted into the fibrogenic phenotype at different levels of the intestinal wall. A complex interaction of cytokines, adhesion molecules and growth factors is involved in the process. We report an overview of recent advances in molecular mechanisms of stricturizing Crohn’s disease (CD) including the potential role of trasforming growth factor beta, protein kinase C and Ras, Raf and ERK proteins. Fibrotic growth factors such as vascular endothelial growth factor and platelet-derived growth factor, as well as the Endothelial-to-Mesenchymal Transition induced by transforming growth factor-β, are considered. Finally, our experience, focused on tumor necrosis factor α (the main cytokine of inflammatory bowel diseases) and the link between syndecan 1 (a heparan sulphate adhesion molecule) and basic fibroblast growth factor (a strong stimulator of collagen synthesis) is described. We hypothesize a possible molecular pattern for mucosal healing as well as how its deregulation could be involved in fibrotic complications of CD. A final clinical point is the importance of performing an accurate evaluation of the presence of fibrotic strictures before starting anti-tumor necrosis α treatment, which could worsen the lesions.