David H. Bruining

Purpose To evaluate the feasibility of use of dark borosilicate oral contrast media (DBOCM) in abdominopelvic CT in comparison with conventional oral contrast media (COCM) in a multi-institutional setting. Methods Patients with known or suspected inflammatory bowel disease (IBD) (Site A) or suspected peritoneal carcinomatosis (Site B), who had undergone initial standard-of-care CT using COCM (positive, n = 10; neutral n = 22), underwent research CT with DBOCM. Attenuation differences between bowel wall and lumen using COCM and DBOCM were measured. Three radiologists independently examined all examinations with COCM and DBOCM. Patient tolerance and safety were recorded. Bowel wall visualization, distention, distended bowel length, and radiologist preference for bowel visualization were rated. Imaging findings using both oral contrast media were recorded, and a final consensus evaluation was performed to evaluate whether additional findings detected with DBOCM were visible with COCM. Results Thirty-two patients (IBD, n = 15; suspected peritoneal carcinomatosis, n = 17) were included. No severe adverse effects were seen with DBOCM. Compared to COCM, DBOCM yielded significantly higher attenuation differences between bowel wall and lumen (P < .001). Bowel wall visualization, distention, and distended bowel length was significantly higher from the stomach to the ileum using DBOCM (P < .001). DBOCM was preferred by each reader over COCM for all intestinal segments, but significance was not achieved in pooled results. Additional imaging findings were found in seven patients (22% [7/32]; 95% CI 9–40%) using DBOCM. Conclusion Compared to COCM, DBOCM yielded improved bowel wall visualization and distention, also revealing additional imaging findings.

Because of a renewed focus on diagnostic and prognostic imaging biomarkers of small bowel strictures in Crohn disease, radiologists can use CT and MR enterography to identify these biomarkers to diagnose and measure strictures, especially those at high risk for surgery.

Crohn’s disease is a transmural inflammatory bowel disease, which can progress to stricturing and internal penetrating complications. Computed tomography enterography (CTE) and magnetic resonance enterography (MRE) are utilized with endoscopy to detect and stage small bowel Crohn’s disease. Small bowel strictures and associated penetrating complications are commonly missed complications of fibrostenosing Crohn’s disease at CTE/MRE. This educational review focuses on factors contributing to unreported or overcalled strictures including disease location, postoperative anatomy, erroneous understanding of threshold dilation for stricture diagnosis, and underappreciation for how stricture diagnosis can improve patient care, emphasizing current understanding of Crohn’s small bowel strictures using illustrative cases. In addition, we explain emerging consensus for how strictures and their associated obstruction can be consistently measured and described. We also review frequently missed complications of fibrostenosing Crohn’s disease such as chronic mesenteric venous occlusion and penetrating complications, including blind-ending sinus tracts, and ileoappendiceal and complex enteroenteric fistulas. Finally, common mimics of fibrostenosing Crohn’s disease including NSAID enteropathy, radiation enteritis, and other entities are discussed, highlighting key distinguishing imaging and clinical features. Radiologists must be proactive in identifying strictures to improve patient outcomes and prevent unnecessary delay in surgical intervention or access to targeted biologic therapies.

Purpose Crohn’s disease (CD) is characterized by enteric inflammation, often resulting in strictures and penetrating complications, which may alter patient management prior to the initiation of biologic therapy. Our aim is to assess the frequency of missed stricturing and internal penetrating complications in CD patients on computed tomography enterography (CTE) and magnetic resonance enterography (MRE) performed prior to anti-TNF therapy. Methods We retrospectively reviewed patients from two tertiary centers who underwent CTE\MRE within six months before starting anti-TNF therapy. Patients with prior intestinal surgery, anti-TNF therapy, or radiology reports indicating strictures or penetrating complications were excluded. Two GI radiologists re-evaluated CTE\MRE images for active inflammation, small bowel strictures (SAR/AGA/SPR criteria), and internal penetrating complications. Senior radiologists reviewed CTE/MRE exams with missed findings and identified potential causes of error. Descriptive statistics were used to summarize the prevalence of missed findings. Where applicable, comparisons were made using chi-square test. Results 250 CD patients were included. 239 (96%) exhibited active terminal ileal (TI) inflammation by expert review of CTE\MRE images. Missed TI strictures were identified in 56 patients (22%). 16 patients (6.4%) had unreported penetrating complications, including ileoappendiceal fistulas (n = 6), sinus tracts (n = 6), complex fistulas (n = 4), inflammatory masses (n = 3), ileocecal fistula (n = 1), and abscess (n = 1). There were no significant differences between institutions in the rates of strictures (18/69 vs. 38/181, P = 0.4) or penetrating complications (5/69 vs. 11/181, P = 0.77). 46% of the strictures appeared obvious upon re-evaluation by senior radiologists, potentially implicating a failure to measure associated small bowel dilation. 38% of missed strictures had multifocal areas of luminal narrowing, and maximal proximal dilation was located 10 cm or more proximal to a stricture in 27%. Conclusion A substantial proportion of strictures and penetrating complications in CD are missed at baseline CTE/MRE prior to anti-TNF therapy initiation, even in specialized centers.

This consensus by the Society of Abdominal Radiology Inflammatory Bowel Disease Disease Focused Panel provides an updated imaging-based definition of small bowel Crohn disease stricture for CT and MR enterography.

Purpose To evaluate correlation between terminal ileal (TI) stricture diagnosis at MR enterography (MRE) and ileocolonoscopy (IC) in patients with Crohn’s disease (CD). Methods One hundred and four patients with CD (51% females; 41 ± 15 years) underwent IC and MRE within 3 months in this retrospective case–control study. Positive cases had TI strictures diagnosed by endoscopy (n = 35); or MRE (threshold small bowel dilation ≥ 3cm; n = 34). Negative controls did not have stricture by either modality (n = 35). Three radiologists examined MRE exams, with per-patient stricture diagnosis based on majority agreement. Sensitivity for stricture diagnosis using threshold dilation of 2.5 cm at MRE was also evaluated. Results There were 69 CD TI strictures (57 by endoscopy; 43 by MRE). Sensitivity by endoscopy and MRE criteria were 82.6% (57/69) and 62.3% (43/69), respectively, with additional 20.3% (14/69) of MRE exams classified as “probable stricture” by SAR/AGA/SPR criteria. Lowering MRE small bowel dilation threshold to 2.5 cm increased MRE sensitivity for endoscopically-diagnosed strictures to 71.9% (41/57; up from 56.1% [32/57]), without sacrificing interobserver agreement (κ = 0.684 vs. κ = 0.587). Of 25 new patients diagnosed with a TI stricture using a 2.5 cm threshold by 2 or more readers, 96% (24/25) had hospitalization, small bowel obstruction, endoscopic dilation, and/or surgical resection during clinical follow-up. Nine false negative MRE exams had short strictures with bowel dilation ≥ 2.5 cm. Conclusion Either IC or MRE alone is insufficient to diagnose Crohn’s small bowel strictures. Diagnostic criteria should incorporate endoscopic and MRE findings. Lowering threshold dilation to 2.5 cm increases sensitivity in stricture diagnosis and identifies clinically significant strictures.

Objective Ultrasound microvessel imaging (UMI) may offer noninvasive, highly sensitive microvessel imaging for assessing Crohn’s disease (CD). However, a quantification metric that demonstrates a strong correlation with pathological inflammation is preferred. The objective was to determine if UMI can enhance IBD imaging interrogations. Methods UMI was performed on bowel wall segments from patients with CD requiring surgery (n = 55 patients). The vessel-length ratio (VLR) measured by UMI was compared with that obtained using color flow imaging (CFI) and with a histopathologic standard evaluated on all bowel layers. Correlations between VLR and pathological inflammation and receiver operating characteristic (ROC) curves between different groups were analyzed to demonstrate the advantages of VLR with UMI. Results The correlation between VLR from UMI and pathological inflammation (R = 0.80) outperformed that of VLR from CFI (R = 0.59). UMI showed a significant difference (p < 0.01) between mild and non-mild inflammation cases, while CFI could not (p = 0.014). In the ROC analysis, VLR with UMI demonstrated an area under the curve (AUC) of 0.93, compared to the AUC of 0.80 for VLR with CFI, indicating better identification of pathological inflammation between mild and non-mild cases. For a sub-cohort of patients with stricture without penetrating complications (n = 19), VLR using UMI also showed better correlation (R = 0.93) with pathological inflammation scores and a higher AUC (0.96) than those of VLR using CFI (R = 0.66 and 0.88, respectively). Conclusions UMI enhances vessel detection sensitivity compared to CFI and more accurately reflects transmural inflammation in small bowel Crohn’s disease. VLR using UMI strongly correlates with pathological inflammation, distinguishing between mild and non-mild cases, notably including patients with stricture without penetrating complications. Key Points Question Bowel wall thickness and Limberg score from ultrasound are insufficient quantitative metrics for reliable diagnosis of inflammation severity for Crohn’s disease. Findings Ultrasound microvessel imaging (UMI) with vessel-length ratio (VLR) is strongly correlated with pathological inflammation and had improved distinction between mild and non-mild inflammation cases. Clinical relevance UMI with VLR has the potential to enhance clinicians’ ability to assess disease activity and evaluate therapeutic responses, thereby improving Crohn’s disease patient outcomes. Graphical Abstract

Stricture length, maximal stricture wall thickness, and maximal associated small bowel dilation at MR enterography can reliably assess Crohn disease stricture severity and serve as eligibility and efficacy criteria in clinical trials.

Maximal associated small bowel dilation, stricture length, and maximal stricture wall thickness at CT enterography can reliably describe Crohn disease stricture severity and serve as eligibility or efficacy criteria in antistricture therapy trials.