Contribution of fetal magnetic resonance imaging and amniotic fluid digestive enzyme assays to the evaluation of gastrointestinal tract abnormalities.

OBJECTIVE

To analyze the contribution of fetal magnetic resonance imaging (MRI) and amniotic fluid digestive enzyme (AFDE) assays to the evaluation of gastrointestinal tract abnormalities.

METHODS

This was a prospective study involving 24 fetuses suspected of having gastrointestinal tract abnormalities on ultrasound examination. MRI was used to analyze the location of the obstruction, the visibility of the small bowel not involved in the obstruction, and the visibility and size of the colon and rectum. Abnormalities were further evaluated by AFDE assays. The final diagnosis was based on postnatal or fetopathological examination.

RESULTS

In duodenojejunal obstructions, MRI (6/6) and AFDE assays (4/4) correctly identified the level of obstruction, but were less accurate for small bowel obstructions (MRI, 10/11; AFDE assays, 7/11). The small bowel not involved in the obstruction was correctly evaluated by MRI as being viable in six cases and as abnormal in eight cases (multiple obstructions or necrosis). However, it was thought antenatally to be abnormal by MRI in four cases in which it was found to be normal on postnatal findings. Three cases in which the colon was found to have abnormal echogenicity were considered normal both by MRI and AFDE assay, in agreement with postnatal findings. Two cases of microcolon-megacystis-intestinal hypoperistalsis syndrome (MMIHS) were diagnosed both by MRI and AFDE assay. Of the three anorectal malformations, two were overlooked by ultrasonography and one by MRI. MRI also overlooked 2/3 associated rectourethral fistulas.

CONCLUSION

MRI and enzyme analysis are good complementary tools to ultrasonography for identifying the level of gastrointestinal obstruction and diagnosing MMIHS. MRI can assess the normality of the intestinal tract not involved in the obstruction, but not multiple obstructions, necrosis and small urodigestive fistulas.