What is the role of ultrasonography in the diagnosis of ulcerative colitis (UC)?

Updated: Feb 23, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Answer

Answer

Excluding infective and toxic states, Crohn disease and ulcerative colitis are the most common causes of chronic large bowel inflammation. US features are nonspecific and include bowel wall thickening, which may involve both the hypoechoic muscular coat and the echogenic mucosa. Wall thickening extends longitudinally, and there is decreased echogenicity and luminal narrowing. Localized perforation may lead to the formation of an abscess, which may be clinically silent if the patient is receiving steroid therapy.

Several criteria have been described for the detection of Crohn colitis and ulcerative colitis. A water-filled colon allows better definition of the large bowel mucosa. With Crohn colitis, the whole bowel wall is thickened; all layers are involved with edema, fibrosis, inflammation, and lymphangiectasis. On US, the wall is clearly thickened, hypoechoic, and homogeneous initially, but it may become inhomogeneous because of fat deposition. The layered anatomy of the bowel wall and the haustra are lost. The bowel becomes rigid, with diminished compressibility and peristalsis. The diameter of the wall is approximately 13 mm.

In ulcerative colitis, the wall thickness is not as great, averaging 7.8 mm. Early disease is confined to mucosa; wall stratification is preserved, but haustra are lost. In Crohn disease and ulcerative colitis, the presence of Doppler parietal flow throughout the affected thickened segment indicates an acute condition. Similarly, an abnormally high mean portal velocity of 30-48 cm/s (normal, 15 ± 7 cm/sec) and an abnormally low resistive index of 0.58-0.78 (normal, 0.908-0.026) are detected in the superior mesenteric artery (SMA). These values, which are determined on the basis of Doppler examination, are known to revert to normal with successful therapy.

Differentiation between ulcerative colitis and Crohn disease is important from a management viewpoint. The latter tends to be transmural disease; the former tends to be a superficial inflammatory process of the mucosa.

Endosonography (EUS) plays a limited role in discriminating ulcerative colitis from Crohn disease, but EUS evaluation of perirectal and perianal complications of Crohn disease has been demonstrated to be superior to fistulography and CT and equal or superior to MRI. [26, 27]

In a study by Bru and associates, hydrocolonic US demonstrated 100% sensitivity in identifying patients with active IBD, and it demonstrated greater overall accuracy (87%) than scintigraphy (77%) in the assessment of disease extension. In addition, a hydrocolonic US activity index was strongly correlated with clinical and endoscopic activity indexes. The authors prospectively compared the usefulness of hydrocolonic US and technetium-99m (99mTc) hexamethylpropylamine oxime (HMPAO)–labeled WBC scintigraphy in 68 patients with active IBD (34 patients had ulcerative colitis; 34 had Crohn disease), in 12 with inactive IBD, and in 10 control subjects. [28]  The authors concluded that their study provided precise US criteria for the definition of bowel involvement by active IBD.

Sigirci and associates concluded in their study that duplex Doppler US of the inferior mesenteric artery (IMA) and superior mesenteric artery (SMA) may be used to evaluate inflammatory disease of the large bowel, to assess the extent of disease, and to document the response to therapy. They evaluated Doppler US blood-flow parameters and spectral patterns in the IMA and the SMA in patients with active and inactive (remission-phase) ulcerative colitis. [29, 8]


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