Deep learning for automatic volumetric bowel segmentation on body CT images

OBJECTIVES

To develop a deep neural network for automatic bowel segmentation and assess its applicability for estimating large bowel length (LBL) in individuals with constipation.

MATERIALS AND METHODS

We utilized contrast-enhanced and non-enhanced abdominal, chest, and whole-body CT images for model development. External testing involved paired pre- and post-contrast abdominal CT images from another hospital. We developed 3D nnU-Net models to segment the gastrointestinal tract and separate it into the esophagus, stomach, small bowel, and large bowel. Segmentation accuracy was evaluated using the Dice similarity coefficient (DSC) based on radiologists' segmentation. We employed the network to estimate LBL in individuals having abdominal CT for health check-ups, and the height-corrected LBL was compared between groups with and without constipation.

RESULTS

One hundred thirty-three CT scans (88 patients; age, 63.6 ± 10.6 years; 39 men) were used for model development, and 60 for external testing (30 patients; age, 48.9 ± 15.8 years; 16 men). In the external dataset, the mean DSC for the entire gastrointestinal tract was 0.985 ± 0.008. The mean DSCs for four-part separation exceeded 0.95, outperforming TotalSegmentator, except for the esophagus (DSC, 0.807 ± 0.173). For LBL measurements, 100 CT scans from 51 patients were used (age, 67.0 ± 6.9 years; 59 scans from men; 59 with constipation). The height-corrected LBL were significantly longer in the constipation group on both per-exam (79.1 ± 12.4 vs 88.8 ± 15.8 cm/m, p = 0.001) and per-subject basis (77.6 ± 13.6 vs 86.9 ± 17.1 cm/m, p = 0.04).

CONCLUSION

Our model accurately segmented the entire gastrointestinal tract and its major compartments from CT scans and enabled the noninvasive estimation of LBL in individuals with constipation.

KEY POINTS

Questions Automated bowel segmentation is a first step for algorithms, including bowel tracing and length measurement, but the complexity of the gastrointestinal tract limits its accuracy. Findings Our 3D nnU-Net model showed high performance in segmentation and four-part separation of the GI tract (DSC > 0.95), except for the esophagus. Clinical relevance Our model accurately segments the gastrointestinal tract and separates it into major compartments. Our model potentially has use in various clinical applications, including semi-automated measurement of LBL in individuals with constipation.

[Practical guideline for short bowel syndrome]

Short bowel syndrome is a rare complex disease that mainly develops due to extensive bowel resections and can lead to chronic intestinal failure. Due to the decreased intestinal surface absorption of macronutrient, micronutrient and/or fluids is reduced. Correspondingly manifold symptoms arise as diarrhoea, weight loss, vitamin deficiencies, chronic kidney disease, hepatopathy and others with great impact on quality of life of patients. Therapy is complex and needs interdisciplinary collaboration between dieticians, gastroenterologists, surgeons and also a dense monitoring of general practitioners. Commonly patients need permanent home-parenteral support. Therapies have to be decided individually and have to be reviewed regularly for effectivity and side effects. Furthermore, periodic monitoring of several clinical and laboratory tests should be performed. Morbidity and mortality of this disease complex is high and lead by appearance and management of complications. This practical guide should give an overview about the disease, diagnostics and management and should enable the best possible care of these complex patients.

Crohn's Disease: Radiological Answers to Clinical Questions and Review of the Literature

Background: Crohn's disease (CD) is a chronic, progressive inflammatory condition, involving primarily the bowel, characterized by a typical remitting-relapsing pattern. Despite endoscopy representing the reference standard for the diagnosis and assessment of disease activity, radiological imaging has a key role, providing information about mural and extra-visceral involvement. Methods: Computed Tomography and Magnetic Resonance Imaging are the most frequently used radiological techniques in clinical practice for both the diagnosis and staging of CD involving the small bowel in non-urgent settings. The contribution of imaging in the management of CD is reported on by answering the following practical questions: (1) What is the best technique for the assessment of small bowel CD? (2) Is imaging a good option to assess colonic disease? (3) Which disease pattern is present: inflammatory, fibrotic or fistulizing? (4) Is it possible to identify the presence of strictures and to discriminate inflammatory from fibrotic ones? (5) How does imaging help in defining disease extension and localization? (6) Can imaging assess disease activity? (7) Is it possible to evaluate post-operative recurrence? Results: Imaging is suitable for assessing disease activity, extension and characterizing disease patterns. CT and MRI can both answer the abovementioned questions, but MRI has a greater sensitivity and specificity for assessing disease activity and does not use ionizing radiation. Conclusions: Radiologists are essential healthcare professionals to be involved in multidisciplinary teams for the management of CD patients to obtain the necessary answers for clinically relevant questions.

Preoperative Magnetic Resonance Enterography to Predict Pathological Specimen Length in Crohn's Disease

BACKGROUND

The European Crohn's and Colitis Organization guidelines have highlighted the importance of the preoperative evaluation of the affected segment length in patients with ileocolic Crohn's disease to determine the best surgical approach.

OBJECTIVE

This study aimed to evaluate the accuracy of preoperative magnetic resonance enterography in assessing the length of the affected segment in patients with ileocolic Crohn's disease.

DESIGN

This observational study was conducted with a prospectively maintained database and retrospective analysis.

SETTINGS

This study was conducted in a tertiary center.

PATIENTS

This study included consecutive patients undergoing ileocolic resection for Crohn's disease between August 2014 and June 2020. All patients underwent a preoperative magnetic resonance enterography.

MAIN OUTCOME MEASURES

The correlation between the length measured on magnetic resonance enterography and pathological examination was evaluated.

RESULTS

A total of 96 patients were included. The median time between magnetic resonance enterography and surgery was 65.5 (3-331) days. The length of the affected segment on magnetic resonance enterography was correlated with the length assessed on pathological evaluation ( R = 0.48, p < 0.001). No correlation was found between the 2 measurements when imaging was performed >6 months before surgery ( R = 0.14, p = 0.62). The presence of an abscess underestimated the length affected by Crohn's disease on imaging compared to pathology, whereas the presence of a fistula was associated with magnetic resonance enterography overestimation of the length of the affected segment.

LIMITATIONS

Limitations included single-center study and retrospective analysis.

CONCLUSION

In Crohn's disease, preoperative magnetic resonance enterography is a highly reliable tool for predicting the length of the affected segment compared to pathology examination in the absence of an abscess or fistula. See Video Abstract at http://links.lww.com/DCR/C26 .

ENTEROGRAFA POR RESONANCIA MAGNTICA PREOPERATORIA PARA PREDECIR LA LONGITUD DE MUESTRAS PATOLGICAS EN LA ENFERMEDAD DE CROHN

ANTECEDENTES:Las guías de la Organización Europea de Crohn y Colitis han resaltado la importancia de la evaluación preoperatoria de la longitud del segmento afectado para determinar el mejor abordaje quirúrgico.OBJETIVO:Evaluamos la precisión de la enterografía por resonancia magnética preoperatoria para evaluar la longitud del segmento afectado en pacientes con enfermedad de Crohn ileocólica.DISEÑO:Realizamos un estudio observacional con una base de datos mantenida prospectivamente y un análisis retrospectivo.CONFIGURACIÓN:Este estudio se realizó en un centro terciario.PACIENTES:Se incluyeron pacientes consecutivos sometidos a resección ileocólica por enfermedad de Crohn entre Agosto de 2014 y Junio de 2020. A todos los pacientes se les realizó una enterografía por resonancia magnética preoperatoria.PRINCIPALES MEDIDAS DE RESULTADO:Se evaluó la correlación entre la longitud medida en la enterografía por resonancia magnética y el examen patológico.RESULTADOS:Se incluyeron un total de 96 pacientes. El tiempo mediano entre la enterografía por resonancia magnética y la cirugía fue de 65,5 (3-331) días. La longitud del segmento afectado en la enterografía por resonancia magnética se correlacionó con la longitud evaluada en la evaluación patológica ( R = 0,48, p < 0,001). No hubo correlación entre las 2 mediciones cuando las imágenes se realizaron más de 6 meses antes de la cirugía ( R = 0,14, p = 0,62). La presencia de un absceso subestimó la longitud afectada por la enfermedad de Crohn en las imágenes en comparación con la patología, mientras que la presencia de una fístula se asoció con una sobrestimación de la longitud del segmento afectado por enterografía por resonancia magnética.LIMITACIONES:Las limitaciones incluyeron un estudio de un solo centro y un análisis retrospectivo.CONCLUSIÓNES:En la enfermedad de Crohn, la enterografía por resonancia magnética preoperatoria es una herramienta altamente confiable para predecir la longitud del segmento afectado en comparación con el examen de patología, en ausencia de absceso o fístula. Consulte el Video Resumen en http://links.lww.com/DCR/C26 . (Traducción-Dr. Yesenia Rojas-Khalil ).

The Challenge of Small Intestine Length Measurement: A Systematic Review of Imaging Techniques

BACKGROUND

Short bowel syndrome is the most common cause of intestinal failure, with morbidity and mortality linked to remanent small intestine length. There is no current standard for noninvasive bowel length measurement.

MATERIALS AND METHODS

The literature was systematically searched for articles describing measurements of small intestine length from radiographic studies. Inclusion required reporting intestinal length as an outcome and use of diagnostic imaging for length assessment compared to a ground truth. Two reviewers independently screened studies for inclusion, extracted data, and assessed study quality.

RESULTS

Eleven studies met the inclusion criteria and reported small intestinal length measurement using four imaging modalities: barium follow-through, ultrasound, computed tomography, and magnetic resonance. Five barium follow-through studies reported variable correlations with intraoperative measurements (r = 0.43-0.93); most (3/5) reported underestimation of length. US studies (n = 2) did not correlate with ground truths. Two computed tomography studies reported moderate-to-strong correlations with pathologic (r = 0.76) and intraoperative measurements (r = 0.99). Five studies of magnetic resonance showed moderate-to-strong correlations with intraoperative or postmortem measurements (r = 0.70-0.90). Vascular imaging software was used in two studies, and a segmentation algorithm was used for measurements in one.

CONCLUSIONS

Noninvasive measurement of small intestine length is challenging. Three-dimensional imaging modalities reduce the risk of length underestimation, which is common with two-dimensional techniques. However, they also require longer times to perform length measurements. Automated segmentation has been trialed for magnetic resonance enterography, but this method does not translate directly to standard diagnostic imaging. While three-dimensional images are most accurate for length measurement, they are limited in their ability to measure intestinal dysmotility, which is an important functional measure in patients with intestinal failure. Future work should validate automated segmentation and measurement software using standard diagnostic imaging protocols.

Growth of Intestinal Neomucosa on Pedicled Gastric Wall Flap, a Novel Technique in an Animal Model

Background: Short bowel syndrome (SBS) remains an unsolved issue in modern medicine. Numerous experimental surgical techniques have been proposed in the attempt to increase the intestinal absorptive capacity.Materials and Methods: Ten female Landrace pigs, divided in two groups of 5 (A and B), were explored through a midline incision. A spindle-shaped vascularized full-thickness gastric wall flap (GWF) consisting of part of the major curvature with the gastroepiploic arch preserved was de-epithelialized and then placed as a "patch" to cover an antimesenteric border defect of either a nonfunctional blind intestinal loop (group A) or a functional intestinal loop of the gastrointestinal tract (group B). A spindle-shaped curved, rigid, low density polyethylene (LDPE) splint was sutured on the external surface of the patch in order to prevent shrinkage of GWF and collapse of the intestinal wall in group A.Results: There was a decrease of both dimensions of the patch. Microscopically a thin layer of columnar epithelial cells covered the center of the patch, evolving in shorter, blunt, poorly developed villi with increasing maturation laterally. The patch surface was covered by nearly 90%. In the three animals that died prematurely the coverage of GWF was negligent or suboptimal directly dependent on the length of survival.Conclusions: The hereby-described patching technique demonstrated the growth of intestinal neomucosa on the GWF. The capability of the stomach to provide large flaps and the advantages of the use of native tissues render this animal model valuable for the future research in the field.

ECCO Topical Review Optimising Reporting in Surgery, Endoscopy, and Histopathology

BACKGROUND AND AIMS

Diagnosis and management of inflammatory bowel diseases [IBD] requires a lifelong multidisciplinary approach. The quality of medical reporting is crucial in this context. The present topical review addresses the need for optimised reporting in endoscopy, surgery, and histopathology.

METHODS

A consensus expert panel consisting of gastroenterologists, surgeons, and pathologists, convened by the European Crohn's and Colitis Organisation, performed a systematic literature review. The following topics were covered: in endoscopy: [i] general IBD endoscopy; [ii] disease activity and surveillance; [iii] endoscopy treatment in IBD; in surgery: [iv] medical history with surgical relevance, surgical indication, and strategy; [v] operative approach; [vi] intraoperative disease description; [vii] operative steps; in pathology: [viii] macroscopic assessment and interpretation of resection specimens; [ix] IBD histology, including biopsies, surgical resections, and neoplasia; [x] IBD histology conclusion and report. Statements were developed using a Delphi methodology incorporating two consecutive rounds. Current practice positions were set when ≥ 80% of participants agreed on a recommendation.

RESULTS

Thirty practice positions established a standard terminology for optimal reporting in endoscopy, surgery, and histopathology. Assessment of disease activity, surveillance recommendations, advice to surgeons for operative indication and strategies, including margins and extent of resection, and diagnostic criteria of IBD, as well as guidance for the interpretation of dysplasia and cancer, were handled. A standardised report including a core set of items to include in each specialty report, was defined.

CONCLUSIONS

Interdisciplinary high-quality care requires thorough and standardised reporting across specialties. This topical review offers an actionable framework and practice recommendations to optimise reporting in endoscopy, surgery, and histopathology.

A Systematic Review of Technical Parameters for MR of the Small Bowel in non-IBD Conditions over the Last Ten Years

Technical guidelines for magnetic resonance imaging (MRI) of the small bowel (SB) in the setting of inflammatory bowel diseases (IBDs) were detailed in a 2017 consensus issued by European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and European Society of Pediatric Radiology (ESPR); however, MRI for non-IBD conditions was not addressed. Hence, we performed a systematic review collecting researches on SB MRI for non-IBDs. The literatures were then divided into morphologic group and functional group. Information about the MRI techniques, gastrointestinal preparation, and details of cine-MRI protocols was extracted. We found that a 1.5 T MRI system, prone positioning, and MR enterography were frequently utilized in clinical practice. Gadolinium contrast sequences were routinely implemented, while diffusion-weighted imaging (DWI) was much less performed. The gastrointestinal preparation varied throughout the studies. No uniform protocols for cine imaging could be established. SB MRI examinations for non-IBDs are far from standardized, especially for functional studies. Recommendations for standard parameters in cine-MRI sequences are difficult to make due to lack of evidentiary support. MRI investigations in non-IBD conditions are needed and the standardization of non-IBD imaging in clinical practice is required.

Three-dimensional CT enterography versus barium follow-through examination in measurement of remnant small intestinal length in short bowel syndrome patients

PURPOSE

To evaluate the feasibility and accuracy of remnant small intestinal length measured by barium follow-through (BaFT) examination and three-dimensional CT enterography (CTe).

MATERIALS AND METHODS

Twenty-nine consecutive short bowel syndrome patients (SBS) who underwent BaFT, CTe, and prior surgical measurements of small intestine were included. Measurements of total remnant small intestinal length on BaFT and CTe were compared to surgical measurements using Spearman's rank correlation coefficients, Bland-Altman plots, and paired t test.

RESULTS

The average remnant intestinal length was 73.1 ± 37.2 cm according to surgical measurement. There was a significant positive correlation between CTe and surgical measurement (r² = 0.99; p < 0.0001), and a relatively weaker correlation between BaFT and surgical measurement (r² = 0.71; p < 0.001). Compared with surgical measurement, the percentage differences of CTe and BaFT were 5.71 ± 6.71% and 27.14 ± 18.41% (mean ± SD), respectively. Furthermore, Bland-Altman plots showed good agreement between CTe and surgical measurement, whereas relatively poor agreement between BaFT and surgical measurement. However, significant difference was found among the three measurement methods by paired t test (p < 0.0001).

CONCLUSIONS

Assessment of remnant small intestinal length by CTe is accurate and acceptable for clinical application, whereas BaFT is less accurate although BaFT is more convenient and cheaper for clinical application. And CTe can provide a cost-effective and noninvasive determination of remnant small intestinal length in planning surgical and nutritional intervention in SBS patients.

Preoperative Prediction of Small Bowel Length Using CT Scan and Tridimensional Reconstructions: a New Tool in Bariatric Surgery?

PURPOSE

During Roux-en-Y-gastric Bypass, the limb lengths are preoperatively determined regardless of individual small bowel length (SBL), which presents a great variability. Few studies highlighted anthropometric factors associated with SBL, and none attempted to predict SBL preoperatively.

OBJECTIVE

The aim of this study is to evaluate factors correlated to SBL (anthropometric and radiologic) and to establish a preoperative SBL prediction.

MATERIAL AND METHODS

In this single-center prospective study, 30 adult patients who underwent laparotomy with a preoperative CT scan were included. Intraoperative SBL measurement was performed with an umbilical tape. Anthropometric parameters were age, gender, height, and BMI. 2D radiological measurements consisted of subcutaneous thickness, abdominal diameters, waist circumference, and mesenteric root length. 3D radiological volumetric reconstructions consisted of whole small bowel and mesentery (WSBM), lean small bowel and mesentery (LSBM), and fat small bowel and mesentery (FSBM).

RESULTS

Mean intraoperative measurement of SBL was 531 ± 105 cm. Among the clinical and radiological measurements, the FSBM volume presented the greatest dispersion. Height (p < 0.02) and LSBM volume (p < 0.01) were significantly correlated to the SBL in univariate analysis. LSBM volume was the only measurement significantly associated with SBL in multivariate analysis (p < 0.006). From the multivariate model, a formula was created to predict SBL. The mean percentage difference between predicted and intraoperative SBL measurements for all patients was 13.7%, and 8.4% for obese patients.

CONCLUSION

LSBM volume is significantly correlated to the SBL. A preoperative SBL prediction with low percentage error could be performed with LSBM volume.

The accuracy of preoperative imaging in measuring the length of the ileocolic segment affected by Crohn's disease: a prospective cohort study

AIM

The study aimed to evaluate the accuracy of imaging for measurement of the length of the ileocolic segment affected by Crohn's disease.

METHOD

Fifty-four consecutive patients who underwent resection between 2011 and 2014 for ileocolic Crohn's disease were prospectively studied. All had preoperative MR or CT enterography. Two independent radiologists measured the length of the diseased intestinal segment. The measurements were compared with the length of disease assessed on pathology of the non-fixed surgical specimen.

RESULTS

The median preoperative length of the Crohn's disease segment on imaging was 20.5 (2-73) cm and 20 (3-90) cm, as measured by the two radiologists. Interobserver agreement was substantial (κ = 0.69) with a correlation coefficient (r) of 0.82 (P < 0.001). The median length of the Crohn's disease segment on pathological examination was 16.5 (2-75) cm and was closely correlated with the radiological measurement (r = 0.76, P < 0.001). The length of the Crohn's disease segment on imaging was correct to within 5 cm of the value on pathology. It was correct in 30 (55%) patients and was underestimated and overestimated in 6 (11.1%) and 18 (33.3%). A length of disease of less than 20 cm found on imaging in 26 patients was confirmed in 25 (96%) on pathology, whereas a length of more than 20 cm found on imaging in 28 patients was confirmed in 18 (64%) on pathology. The sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of imaging for predicting a length of less than 20 cm were 71%, 95%, 96%, 64% and 79%.

CONCLUSION

Imaging accurately identifies the length of the ileocolic segment of Crohn's disease when it is 20 cm or less on pathological examination. In patients with more extensive disease, imaging tends to overestimate the length and should be interpreted with caution.

A Novel Approach to Calculating Small Intestine Length Based on Magnetic Resonance Enterography

BACKGROUND

Bowel length is an important factor in the management of patients with intestinal failure and short bowel syndrome. However, it is difficult to accurately measure the length of the small intestine. Our aim was to demonstrate the feasibility of a dedicated software algorithm for calculating small intestine length based on magnetic resonance enterography (MRE) images.

STUDY DESIGN

A custom algorithm for image thresholding, wall identification, segmentation, and path extraction was designed and implemented. Algorithm output included the Euclidean distance from the pylorus to the terminal ileum and coordinates of points along that route. For validation, 10 C57BL/6 mice underwent bowel preparation before MRE. After sacrifice, the entire small bowel was removed and the ex vivo small intestine length was measured in a standardized manner. Calculated and ex vivo length measurements were compared.

RESULTS

Mean absolute difference and mean percentage difference between the 2 modalities were 1.8 ± 3.8 cm (p = 0.24) and 9.4% ± 6.0%, respectively.

CONCLUSIONS

This study demonstrates the feasibility of a dedicated, computer-vision-based algorithm that can reliably and accurately calculate the length of the small intestine using MRE images. A validated, noninvasive approach to measuring small intestine length that can be implemented using available clinical imaging can have a dramatic clinical impact on management in patients with short bowel syndrome, Crohn's disease, and other intestinal disorders.

Influence of repeated measurements on small bowel length

Purpose

Measurement of small bowel length (SBL) is a common procedure in gastrointestinal surgery. When required, repeated SBL measurements can be done during surgery. Our aim was to evaluate whether these repeated measurements differ in SBL results.

Methods

Small bowel length was measured during laparotomy in 28 patients between ligament of Treitz and caecum, using a standard measure, two times in each patient consecutively by two different surgeons from the anti-mesenteric border of the bowel.

Results

The median age was 33 (19–67) including 18 male. There were 16 healthy donors for living related liver transplantations. Second measurements, performed immediately after the first measurements, significantly shortened the measured SBLs in the same patients (580 ± 103 vs. 485 ± 78 cm, p < 0.001).

Conclusions

During surgery, repeated length measurements caused contractions in the small bowel and this resulted to a significant decrease in the SBL. This should be keep in mind to prevent mismeasurements.

Accurate assessment of bowel length: the method of measurement matters

PURPOSE

Small intestinal length has prognostic significance for patients with short bowel syndrome, and accurate measurement of Roux-en-Y limbs is considered important. The flexible elasticity of bowel makes its measurement highly subjective, yet a recommended method for intestinal measurement allowing accurate comparisons between surgeons remains undefined. Measurement of intestinal length has been described, but no comparison of the fidelity of measurement technique has been made. We hypothesized that silk suture and umbilical tape would yield the most consistent measurements.

METHODS

This institutional review board-approved prospective trial enrolled 12 volunteer surgeons and two Institutional Animal Care and Use Committee-donated rabbits. Participants were asked to measure short, medium, and long segments of small intestine in a euthanized rabbit using common operating room tools: 18-in silk suture, 75-cm umbilical tape, 15-cm straight ruler, laparoscopic Dorsey bowel graspers. Data were analyzed by analysis of variance repeated measures model.

RESULTS

Over short segments, intestinal measurements by grasper were significantly shorter than those by tape (P = 0.002) and ruler (P = 0.039). Over medium lengths of bowel, measurements by grasper were significantly shorter than those by suture (P = 0.032) and tape (P = 0.046), and measurements by ruler also were significantly shorter than those by suture (P = 0.008). Over the long intestinal segment, measurements by ruler resulted in the greatest variability, and comparison of variance across all possible pairs of groups found significant difference by method of measurement (P = 0.049). There was a significant difference in measurements taken along the mesenteric border compared with those taken along the antimesenteric border (P = 0.001).

CONCLUSIONS

Measurement technique along short segments matters less; however, rigid tools underestimate length, and smaller variances in measurement by silk suture and umbilical tape suggest that these methods are more reliable across longer distances.

Management and Complications of Short Bowel Syndrome: an Updated Review

Short bowel syndrome (SBS) is defined as loss of bowel mass from surgical resection, congenital defects, or disease. Intestinal failure (IF) includes the subset of SBS unable to meet nutrition needs with enteral supplements and requires parenteral nutrition (PN). The parenteral treatment of SBS is now a half-century old. Recent pharmacologic treatment (GLP-2 analogues) has begun to make a significant impact in the care and ultimate management of these patients such that the possibility of reducing PN requirements in formerly PN-dependent patients is a now a real possibility. Finally, newer understanding and possible treatment for some of the complications related to IF have more recently evolved and will be an emphasis of this report. This review will focus on developments over the last 10 years with the goal of updating the reader to new advances in our understanding of the care and feeding of the SBS patient.

[Modern MRI of the small bowell]

CLINICAL METHODOLOGICAL ISSUES

The radiological diagnostics of diseases of the small intestine have undergone a great change in the last two decades. Through rapid progress with new treatments and an increasing therapeutic focus on transmural healing, a complete evaluation of the gastrointestinal tract is now crucial.

STANDARD RADIOLOGICAL METHODS

With the introduction of endoscopy, gastrointestinal imaging with a relatively high radiation exposure had only limited applications. The development of cross-sectional imaging allowed a much broader radiological evaluation of abdominal diseases. Due to rapid investigation techniques, excellent soft tissue contrast and the distinct advantage of eliminating exposure to radiation, magnetic resonance imaging (MRI) of the gastrointestinal tract has gained increasing importance. With sufficient filling of the intestinal lumen, simultaneous imaging of all the intestinal wall layers, the perienteric structures and associated abdominal pathologies is now possible.

METHODOLOGICAL INNOVATIONS

New MR sequences, such as diffusion-weighted sequences, dynamic contrast-enhanced sequences and MR fluoroscopy, enable the detection of morphological changes, with additional characterization of affected bowel loops as well as the assessment of functional pathologies with dynamic information about intestinal motility disturbances.

ACHIEVEMENTS

Recent guidelines of European radiological and gastroenterological organizations have confirmed the importance of cross-sectional imaging and particularly of MRI for diagnostics and follow-up in patients with Crohn's disease. Due to the possibility of assessment of all the layers of the intestinal wall and the presence of extramural complications, MRI has a significant impact on further therapeutic treatment in patients with inflammatory bowel disease.

PRACTICAL RECOMMENDATIONS

Especially in patients with inflammatory bowel disease, MR enterography and MR enteroclysis should be the methods of choice for the evaluation of small bowel pathologies because of radiation issues and the great diagnostic value they provide. A variety of MR sequences has enabled not only the detection but also the characterization of pathological changes of the small intestine, which are vital for further treatment of these patients.

Distinct management issues with Crohn's disease of the small intestine

PURPOSE OF REVIEW

Small bowel Crohn's disease can present with clinical challenges that are specific to its location. In this review, we address some of the areas that present particular problems in small bowel Crohn's disease.

RECENT FINDINGS

A key issue specific to small bowel Crohn's disease relates to its diagnosis given that access to the small bowel is limited. Radiological advances, particularly in small bowel ultrasonography and MRI, as well as the introduction of capsule endoscopy and balloon enteroscopy are helping to address this. In addition, our ability to differentiate small bowel Crohn's disease from other causes of inflammation, such as tuberculosis, is improving on the basis of better understanding of the features that differentiate these conditions. It is also becoming apparent that jejunal Crohn's disease represents a distinct disease phenotype with potentially worse clinical outcomes. Finally, because it is a rare complication, our understanding of small bowel cancer associated with Crohn's disease remains limited. Recent publications are, however, starting to improve our knowledge of this condition.

SUMMARY

Although small bowel Crohn's disease presents specific management issues not seen in patients with Crohn's disease elsewhere in the gastrointestinal tract, our knowledge of how to manage these is improving.