Enteritis--is it an ultrasonographic diagnosis (Proceedings)

Thickening of the intestinal wall is the most common ultrasonographic finding in inflammatory bowel diseases.   Inflammation is often characterized by extensive and symmetric wall thickening.  The wall layering is usually still maintained, although it may be altered.  

Enteritis may produce different ultrasonographic appearances depending on the localization, duration and severity of the inflammatory condition.  Common inflammatory changes such as lymphocytic plasmocytic enteritis (LPE) can be detected by mild to moderate thickening of one or several intestinal segments.  Mildly thickened bowel (about 4 mm thick) usually can be identified by comparison to other intestinal segments of the same animal.  In addition, the affected segment(s) can appear hypomotile and “rigid” as a small amount of fluid and/or ingesta floats in the lumen. 

As in people, the early stages of LPE primarily affect the mucosa and submucosa.  The prominent mucosa is unevenly increased in echogenicity, and the demarcation between the mucosa and submucosa may be indistinct.  It is also important to acknowledge that inflammatory bowel disease and (small cell) lymphosarcoma can share similar ultrasonographic features, and therefore a cytological or histopathological diagnosis is recommended to confirm the diagnosis.

The presence of bright mucosal speckles, perpendicular or parallel lines can be observed in several intestinal segments. The mucosal hyperechoic speckles are of unknown origin and clinical relevance.  The linear hyperechoic lines within the mucosa, aligned perpendicular to the lumen axis most likely represent dilated lacteols.

This finding is commonly associated with protein-losing enteropathy and lymphangiectasia, and seldomly seen in infiltrative tumors.  ThA linear, hyperechoic line, parallel to the submucosa is likely representing mucosal fibrosis.  This recently reported feature can be encountered in animals with or without digestiverelated clinical signs.  The submucosa can appear thickened and uneven.  In some conditions, the muscularis layer is moderately thickened. 

This thickening may correspond to an idiopathic hypertrophy of the smooth muscle layer. In instances of moderately altered layering, a “daisy-like” pattern of the affected segments of bowel can be seen.  This pattern describes the circular, convoluted appearance of the mucosa seen in transverse section. Smooth muscle thickening can be present in chronic enteritis, particularly in cats, but this finding is not specific and also can be present in other disorders, such as mechanical obstruction secondary to foreign material or tumoral infiltration. Mild to moderate regional reactive lymph nodes enlargement is often encountered in inflammatory GI diseases.

Corrugated intestines appear as undulated bowel segments. This nonspecific finding can be seen in association with regional inflammation such as enteritis, pancreatitis, peritonitis, or abdominal neoplasia, or bowel ischemia.

In cases of severe inflammatory changes encountered with lymphoplasmacytic, eosinophilic, or granulomatous enteritis, edema, hemorrhage and fibrosis can severely disrupt the wall layering and be associated with mass lesions mimicking a tumoral process.

In perforation secondary to foreign-body migration, deep ulceration, or postoperative dehiscence, the affected wall is thickened and hypoechoic, and there can be local loss of layering.  At times, a hyperechoic tract can be seen crossing the wall, and the adjacent mesentery/omemtum is significantly increased in echogenicity because of focal steatitis or/peritonitis.  Fluid accumulation is often noted near the perforation or dehiscence site, and free peritoneal gas can sometimes be detected as short, bright, linear interfaces associated with comet-tail artifacts. 

Colon can be a more challenging portion of the digestive tract to evaluate ultrasonographically because of its thinner wall, the variable degree of distention with gas and feces, and the redundancy of the folds that can mimic wall thickening.  Mild to moderate thickening can affect part or most of the colonic wall.  Wall layering can be less distinct but is usually preserved.  In addition to these changes, ulcerative colitis may be associated with poorly distinct wall layers and irregular lumen contours secondary to numerous superficial mucosal ulcers.

Parasitic infestations such as peritoneal cestodiasis are rare. Cystic subserosal lesions have been described on the GI tract of affected dogs or cats.

References

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