Studies of the sensitivity of CTE vs MRE for small-bowel pathology have shown mixed results, (7,10-12) while at least one study has shown improved sensitivity of CTE for distinguishing perienteric features due to increased conspicuity of the mesentery on CTE.
Diffusion weighted imaging is also used to improve sensitivity for detecting diseased bowel-wall segments and perienteric soft tissues.
Typical US imaging appearance of CD was defined as bowel wall thickening (>3mm), losing or preserving the gut signature, while the extramural disease was defined as perienteric
fluid and creeping fat which separates bowel loops .
(29, 43, 44) Although generally submucosal based, a majority of tumors extend into the muscularis propria and in rare cases extend transmurally into the perienteric
connective tissue or even metastasize to regional lymph nodes.
High-resolution ultrasound probes (frequencies > 7.5 Mhz) exhibit stratification of SB wall--with five different concentric layers--the first from the lumen is echogenic interface between lumen content and mucosa, then hypoechogenic mucosa, echogenic submucosa in the middle of wall, next hypoechogenic muscularis propria and the fifth--outer echogenic layer represents serosa and interface with perienteric structures.
Reliability of sonographic examination depends on goodclass ultrasound device with standard abdominal (2.5-6 Mhz) convex and high resolution linear or convex probe(7.5-14 MHz), both with harmonic mode, pulse wave doppler (PWD) for quantitative evaluation of celiac and superior mesentery flows, color flow doppler (CFD) and contrast enhanced ultrasonography (CEUS) software for detection and quantification of intramural vascularisation in thickened bowel wall and perienteric structures.
Searching for secondary signs of regional inflammation, such as increased mesenteric vascularity ("comb sign") or perienteric fluid or enhancement can prove particularly fruitful in identifying regions of active inflammation (Figure 5).
Perienteric and interloop abscesses may form, but may be difficult to detect on MR, and thorough investigation of bowel loops and the mesentery in all available planes should be undertaken.
Other findings, such as the Comb sign (engorgement of the vasa recta), fibrofatty proliferation, and stranding in the perienteric fat also indicate active inflammation.
CT of prominent pericolic or perienteric vasculature in patients with Crohn's disease: Correlation with clinical disease activity and findings on barium studies.