Background: Increased small intestinal wall thickness correlates with both inflammatory activity and fibrosis in Crohn's disease (CD). Assessment of perfusion holds promise as an objective marker distinguishing between the two conditions. Our primary aim was to determine if relative bowel wall perfusion measurements correlate with histopathological scores for inflammation or fibrosis in CD
Methods: 25 patients were investigated prior to elective surgery for small intestinal CD. Unenhanced Ultrasonography (US) and MR Enterography (MRE) were applied to describe bowel wall thickness and ulcers.
Perfusion was assessed with Contrast Enhanced US (CEUS) and Dynamic Contrast Enhanced MRE (DCE-MRE). Histopathology was used as gold standard.
Results: Bowel wall thickness measured on histopathology was 8.7±1.6 mm, on US 9.1±2.1 mm and on MRE 10.0±2.6 mm. US measurements were 0.4 (−0.3 to 1.0) mm thicker, p=0.238 (LoA −2.7 to 3.5 mm), whereas MRE measured a mean of 1.4 (0.4 to 2.3) mm thicker bowel wall compared to histopathology, p=0.006 (LoA −3.0 to 5.7 mm). Ulcers defined as linear, rake, confluent, or large were present in 19 patients on histopathology. Sensitivity and specificity for ulcer detection by US and MRE are shown in Table 1.
No correlation was found between the severity of inflammation nor fibrosis on histopathology and neither DCE-MRE (r=−0.13, p=0.54 for inflammation and r=0.41, p=0.05 for fibrosis) nor CEUS (r=0.16, p=0.45 for inflammation and r=−0.28, p=0.19 for fibrosis). Wall thickness assessed with US was correlated with both histological inflammation (r=0.611, p=0.0012) and fibrosis (r=0.399, p=0.048). The same was not true for MR (r=0.41, p=0.047 for inflammation and r=0.29, p=0.16 for fibrosis).
Conclusions: In conclusion, we found no correlation between relative perfusion measurements and histological grading of inflammatory activity or fibrosis. This could be due to the chosen gold standard and the complicated nature of perfusion measurements. Bowel wall thickness remains the single parameter that correlates best with both activity and fibrosis and can be reliably estimated by MRE and especially US.