Recent Advances in Imaging of Small and Large Bowel

Comparing the Diagnostic Value of FDG PET or PET/CT With FDG PET/MR in Inflammatory Bowel Disease-A Systematic Review and Meta-analysis

BACKGROUND

The aim of this study was to compare the diagnostic value of 18 F-FDG PET or PET/CT with FDG PET/MR in patients with inflammatory bowel disease (IBD).

METHODS

A comprehensive search was performed in PubMed for studies reporting the diagnostic performance of FDG PET (PET/CT) and FDG PET/MR in IBD from the inception of the database to March 14, 2024, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Fourteen studies were included in this systematic review and meta-analysis. Pooled estimates of segment-based sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio for FDG PET (PET/CT) and FDG PET/MR were calculated alongside 95% confidence intervals. Summary receiver operating characteristic (SROC) curves were plotted, and the area under the SROC curve was determined alongside the Q * index.

RESULTS

The segment-based pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the SROC curve of FDG PET (PET/CT) for diagnosing IBD (9 studies) were 0.81, 0.86, 5.76, 0.22, 31.92, and 0.92, respectively. Those of FDG PET/MR (5 studies) were 0.78, 0.92, 10.97, 0.25, 51.79, and 0.95. There was no significant difference in the abilities of detecting or excluding IBD between FDG PET (PET/CT) and FDG PET/MR.

CONCLUSIONS

For diagnostic value in patients with IBD, there was no significant difference between FDG PET (PET/CT) and FDG PET/MR. Both FDG PET (PET/CT) and FDG PET/MR have demonstrated high diagnostic performance for accurate diagnosing in patients with IBD.

CRITICAL STEPS FOR HUMAN GUT EXFOLIOME RNA PROFILING ANALYSIS USING NON-INVASIVE STOOL SAMPLES

INTRODUCTION

Dietary exposure and drug treatments influence gut cellular pathways and hence growth and potentially even the gut-brain-microbiome axis. Since eukaryotic mRNA presents poly A sequence that distinguishes them from the prokaryotes mRNA, we could analyze the gene expression of human gut cells using exfoliated gut cells available in stool samples. However, the impact of the critical steps of these non-invasive methods must be analyzed.

METHODS

We tested prokaryote contamination in all the steps of different procedures to analyze human exfoliome by microarrays and the influence of the fecal sampling collection process.

RESULTS & CONCLUSION

The least bacterial contamination was found using RNA amplified with oligo dT from GeneChip 3´ IVT Pico Reagent kit or using RNA purified by both Oligotex® + oligodT. RNA later® collection of feces affects the microarray results compared to directly frozen fecal samples, although both methods produce similar cDNA quality. This technique is a potential non-invasive diagnostic tool that can be applied to larger studies to quantify intestinal gene expression in humans with non-invasive samples, but samples should always be collected and analyzed under the same procedure.

PET/computed tomography enterography

Interpretation of gastrointestinal PET/computed tomography (PET/CT) is often complicated by anatomy including bowel folds, flexures, variant redundancy, decompressed bowel segments and physiological uptake. This makes it very difficult to identify both true positives and true negatives, compromising both sensitivity and specificity. CT enterography is increasingly being integrated into the field of nuclear medicine to address these issues. This technique uses the combination of negative/neutral contrast to distend the lumen of the gut and iodinated contrast to enhance the gastrointestinal wall and pathological findings. Apart from augmentation in the diagnostic performance, the technique also improves the quality of the imaging, confidence of the reporting physician and inter-rater agreement. Therefore, this technique has found favor among nuclear medicine physicians, in the imaging of chronic inflammatory disorders and malignancies in and of the gut. It is a feasible and easily executable procedure with minimal and manageable side-effects and should be routinely recommended in cases where interference from physiologic findings is expected.

FDG-PET-CT Enterography Helps Determine Clinical Significance of Suspected Ileocecal Thickening: A Prospective Study

BACKGROUND

Ileocecal thickening (ICT) on imaging could result from diverse etiologies but may also be clinically insignificant.

AIM

Evaluation of role of combined 2-deoxy-2-fluorine-18-fluoro-D-glucose(¹⁸F-FDG)-positron emission tomography and computed tomographic enterography (PET-CTE) for determination of clinical significance of suspected ICT.

METHODS

This prospective study enrolled consecutive patients with suspected ICT on ultrasound. Patients were evaluated with PET-CTE and colonoscopy. The patients were divided into: Group A (clinically significant diagnosis) or Group B (clinically insignificant diagnosis) and compared for various clinical and radiological findings. The two groups were compared for maximum standardized uptake values of terminal ileum, ileo-cecal valve, cecum and overall.

RESULTS

Of 34 patients included (23 males, mean age: 40.44 ± 15.40 years), 12 (35.3%) had intestinal tuberculosis, 11 (32.4%) Crohn's disease, 3 (8.8%) other infections, 1 (2.9%) malignancy, 4 (11.8%) non-specific terminal ileitis while 3 (8.8%) had normal colonoscopy and histology. The maximum standardized uptake value of the ileocecal area overall (SUVmax-ICT-overall) was significantly higher in Group A (7.16 ± 4.38) when compared to Group B (3.62 ± 9.50, P = 0.003). A cut-off of 4.50 for SUVmax-ICT-overall had a sensitivity of 70.37% and a specificity of 100% for prediction of clinically significant diagnosis. Using decision tree model, the SUVmax-ICT with a cut-off of 4.75 was considered appropriate for initial decision followed by the presence of mural thickening in the next node.

CONCLUSION

PET-CTE can help in discrimination of clinically significant and insignificant diagnosis. It may help guide the need for colonoscopy in patients suspected to have ICT on CT.

Non-traumatic abdominal pain: assessment of diagnostic value of MDCT enterography in small bowel diseases—a retrospective study

Background

Because of its unique anatomy, overlap of its loops, and its continuous peristaltic motion, imaging of the small bowel is a big challenge. Non-traumatic abdominal pain of small bowel origin includes a spectrum of medical and surgical conditions ranging from minor to life-threatening conditions. Accurate diagnosis of these diseases is essential to reduce morbidity and mortality. The aim of our study is to assess the role of MDCT enterography in evaluation and diagnosis of different small bowel causes of non-traumatic abdominal pain.

Results

Data analysis of 47 patients’ files included in this study revealed a high diagnostic accuracy of MDCTE in diagnosing variable small bowel-related pathologies that were confirmed histopathologically.

Conclusion

MDCTE can be used as a reliable diagnostic imaging modality for the detection of small bowel diseases. However, operative data and tissue biopsy are still the confirmatory methods for diagnosis.