Fetal echogenic gut: a marker of intrauterine gut ischaemia?

Echogenic bowel on second-trimester ultrasonography: evaluating the risk of adverse pregnancy outcome

OBJECTIVE

To estimate if echogenic bowel diagnosed on second-trimester ultrasonography has an independent risk association with intrauterine growth restriction (IUGR) and intrauterine fetal demise.

METHODS

This is a retrospective cohort study of all patients with singleton gestations who presented to our institution for second-trimester ultrasonography between 1990 and 2008. Study groups were defined by the presence or absence of echogenic bowel. Primary outcomes were IUGR, defined as birth weight less than the 10th percentile for gestational age and intrauterine fetal demise at 20 weeks or more of gestation. Univariable and multivariable logistic regression analyses were used to estimate the risk of intrauterine fetal demise and IUGR in fetuses with echogenic bowel. Analyses were repeated after excluding cases of aneuploidy, cytomegalovirus (CMV) infection, other major congenital anomalies, and abnormal second-trimester serum screening results.

RESULTS

Of 64,048 patients, the incidence of echogenic bowel was 0.4%. Of these, echogenic bowel was an isolated finding in 188 (72.3%) cases. There were 579 (0.9%) cases of intrauterine fetal demise and 8,173 (12.8%) cases of IUGR in the entire cohort. After excluding cases of aneuploidy and CMV infection, the incidence of intrauterine fetal demise was 7.3% in the echogenic bowel group compared with 0.9% in the nonechogenic bowel group, translating to an absolute risk increase of 6.4%. The incidence of IUGR in the echogenic bowel group was 19.5% compared with 12.9% in the nonechogenic bowel group (absolute risk increase, 6.6%). After controlling for potential confounders, echogenic bowel was significantly associated with both intrauterine fetal demise (adjusted odds ratio [OR] 9.6, 95% confidence interval [CI] 5.8-15.9) and IUGR (adjusted OR 2.1, 95% CI 1.5-2.9). This risk association remained significant even when evaluating echogenic bowel as an isolated sonographic finding.

CONCLUSION

The presence of echogenic bowel on ultrasonography is independently associated with an increased risk for both IUGR and intrauterine fetal demise. Serial growth assessment and antenatal testing may be warranted in these patients.

Hyperechogenic fetal bowel: an ultrasonographic marker for adverse fetal and neonatal outcome?

"Soft markers" are considered variants of normal and should be considered distinct from fetal anatomic malformations. Hyperechogenicity of the fetal bowel, is one of the few soft markers that can also associated with a variety of other pathologic conditions. In this review we will focalise our attention on the significate of an increased echogenicity of fetal bowel and on management of fetuses with this condition.

Transient Bowel Ischaemia of the Fetus

OBJECTIVE

To discover the different underlying conditions in 2 fetuses suffering from temporary bowel ischaemia.

METHODS

Abnormal bowel findings were detected using antenatal sonography.

RESULTS

The abnormal bowel findings disappeared postnatally. Transient ischaemia of the fetal bowel due to different causes has been advocated antenatally to explain the abnormal findings. When a normal blood supply to the bowel has been restored, either in utero or after birth, the abnormal findings disappear.

CONCLUSIONS

Whenever gut dilatation is detected in a fetus at risk of bowel ischaemia the possibility of a transient functional finding must be considered.

Blood flow parameters of the superior mesenteric artery as an early predictor of intestinal dysmotility in preterm infants

BACKGROUND

Blood flow parameters in the superior mesenteric artery (SMA) change with vasoconstriction or vasodilatation of the intestinal vascular bed. In cases of severe growth retardation as a result of haemodynamic disturbances, the blood flow changes persist into postnatal life.

OBJECTIVE

To assess early changes of Doppler sonographic blood flow parameters in the SMA for prediction of later intestinal motility disturbances in preterm infants and tolerance of enteral feeding during the first week of life.

MATERIALS AND METHODS

Doppler sonographic blood flow parameters in the SMA were measured on the first day of life and the following 5 days in 478 neonates with a birth weight below 1,500 g. According to the Doppler results, the neonates were divided into two groups-those with pathological parameters and those with normal blood flow parameters. Correlations between blood flow parameters, the development of intestinal dysmotility and the tolerated amount of enteral feeding were calculated.

RESULTS

Pathological blood flow parameters were observed in 148 neonates (group 1) and normal blood flow parameters in 330 neonates (group 2). Intestinal motility disturbance occurred in 125 neonates (83%) of group 1 and 47 neonates (15%) of group 2. Neonates in group 2 tolerated significantly more feed by the fifth day of life than neonates in group 1. Postnatal adaptation did not differ between the two groups, although the majority of neonates with intestinal dysmotility were small for gestational age. The predictive value of blood flow parameters for prediction of intestinal motility revealed high sensitivity and specificity by the first postnatal day, 2 or 3 days before development of clinical signs of intestinal dysmotility. There was a strong negative correlation between pathological pulsatility index on day 1 and the quantity of tolerated enteral feeding on day 5.

CONCLUSIONS

Pathological blood flow parameters in the SMA can predict problems of intestinal motility and tolerance of enteral feeding. With the early detection of these problems a prompt start of adequate therapy to avoid complications is possible.

Could the consequences of premature delivery be further attenuated by means of new prenatal strategies?

The last 10 years have already seen improvements in the short- and long-term prognosis for premature neonates. Nevertheless, progress in the prenatal evaluation of predictive factors for neonatal diseases and more detailed and reliable knowledge of fetal physiology could allow the development of new treatments with consequent expectations of further improvements in the prognosis for such premature newborns. Global strategies for the management of preterm labour, ranging from a policy for prenatal transfer to centres offering the appropriate level of perinatal care, should continue to be expanded, and long-term evaluations must also be continued.

Increased morbidity in severe early intrauterine growth restriction

OBJECTIVE

To determine the relative frequencies of complications in severe early intrauterine growth-restricted (IUGR) infants.

METHODS

All infants 32 weeks gestation or less with birth weight less than the fifth percentile admitted from January 1991 to December 1998 were identified retrospectively. Two infants were identified for each IUGR case: the subsequent admission with birth weight +/-100 g of the case, and the subsequent admission with the same gestational age. Infants with multiple congenital anomalies, congenital infections or admission after 48 hours of age were excluded. Maternal and neonatal demographic data, neonatal morbidity and mortality until discharge were gathered by chart review.

RESULTS

A total of 39 IUGR identified infants met criteria, with 41 gestational age infants and 33 birth weight infants. Mean birth weights and gestational ages for the IUGR group, gestational age group, and birth weight group were 744 g and 29.6 weeks, 1370 g and 29.7 weeks, and 781 g and 25.5 weeks respectively. Mortality was higher for IUGR infants than gestational age infants (20.5 vs 0%), but less than the birth weight infants (30%). In surviving infants, total ventilator days, total oxygen days, days to full feeds, and patent ductus arteriosis, were higher for IUGR infants than gestational age infants, but less than birth weight infants. Hypoglycemia, direct hyperbilirubinemia, necrotizing enterocolitis (NEC), thrombo-cytopenia, chronic lung disease and feeding difficulties occurred more frequently in IUGR infants than in both other groups. Length of stay for survivors and incidence of retinopathy of prematurity (ROP) was similar for the IUGR and birth weight infants.

CONCLUSIONS

Infants born prematurely who are also severely IUGR have higher neonatal morbidity and mortality when compared to infants of similar gestational age. The surviving IUGR infants had less intraventricular hemorrhage and periventricular leukomalacia than less mature infants of comparable birth weight, but a similar incidence of ROP and length of stay. They had a higher incidence of NEC, direct hyperbilirubinemia and chronic lung disease, probably due to end-organ damage in utero from chronic placental insufficiency. These findings highlight the unique pattern of mortality and morbidity seen in infants with severe early IUGR.

Quantitative assessment of fetal bowel echogenicity: comparison of harmonic, compound, and fundamental sonographic images

PURPOSE

The aims of this study were to assess normal fetal bowel echogenicity quantitatively and to compare the levels of bowel echogenicity observed with the use of 3 different sonographic image-processing techniques-harmonic plus compound imaging, harmonic imaging alone, and fundamental imaging-and 2 different broadband transducers.

METHODS

Women with normal singleton second-trimester fetuses underwent sonographic scanning with both a 2-5-MHz and a 4-7-MHz transducer. The use of the 3 imaging techniques and the 2 transducers resulted in 6 types of images: 2-5-HC (harmonic plus compound images), 2-5-H (harmonic images), and 2-5-F (fundamental images), and 4-7-HC, 4-7-H, and 4-7-F images. The relative echogenicities (brightness) of the fetal bowel and iliac bone were measured, and bowel echogenicity ratios (bowel echogenicity/iliac bone echogenicity x 100) were calculated using graphics software. The resulting data were analyzed to evaluate differences in echogenicity ratios between the 6 types of images.

RESULTS

We examined 37 fetuses during the study period. The bowel echogenicity ratios were highest on the images obtained with harmonic and compound-imaging techniques (2-5-HC, 84.7 +/- 23.4%; 4-7-HC, 98.5 +/- 36.4%). The bowel echogenicity ratio for the 2-5-HC images was significantly higher than those for the 2-5-H and the 2-5-F images (p < 0.01 and p < 0.001, respectively), and those for the 4-7-HC and 4-7-H images were higher than that for the 4-7-F images (p < 0.01 for both comparisons).

CONCLUSIONS

A sonographic finding of echogenic fetal bowel should be interpreted cautiously because the use of special image-processing techniques can artificially enhance the apparent level of echogenicity of the bowel. We recommend rescanning without the use of those techniques if the fetal bowel appears to have an increased level of echogenicity.

Role of platelet-activating factor in the pathophysiology of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal illness that affects predominantly preterm infants. Treatment options are limited and NEC remains a significant cause of morbidity and mortality. The precise aetiology of NEC remains unclear but evidence strongly suggests that the cause is multifactorial and there are four main aetiological factors: prematurity, hypoxia, enteral feeding and bacterial colonization. The presence of similar intestinal lesions, regardless of aetiological trigger, strongly implicates a final common pathway in the pathogenesis. There is now a substantial body of evidence to indicate that endogenous inflammatory mediators, particularly platelet-activating factor (PAF), play a vital role in this final pathway.

CONCLUSION

The use of agents that antagonize PAF may provide therapeutic options in the management of NEC.

Early feeding advancement in very low-birth-weight infants with intrauterine growth retardation and increased umbilical artery resistance

BACKGROUND

To investigate whether intrauterine growth retardation (birth weight <10th percentile), increased umbilical artery resistance (resistance index >90th percentile measured by Doppler velocimetry), or brain sparing (increased umbilical artery resistance and decreased middle cerebral artery resistance index <5th percentile) were associated with early feeding intolerance in very low-birth-weight (VLBW, <1,500 g) infants.

METHODS

From July 1999 to December 2000, 124 inborn VLBW infants were enrolled in a prospective trial evaluating early enteral nutrition after a standardized feeding protocol (daily feeding advancement, 16 mL/kg birth weight). Feeding tolerance was assessed as the age at which full enteral feeds (150 mL/kg daily) were achieved. Data are shown as median, 25th, and 75th percentiles.

RESULTS

Full enteral feeds were achieved at 15 days (range, 12-21 days) of age for all infants. Intrauterine growth retardation (full enteral feeding achieved at 14 days; range, 12-21 days), increased umbilical artery resistance (full enteral feeding achieved at 14 days; range, 11-16 days), and brain sparing (full enteral feeding achieved at 15 days; range, 14-20 days) were not associated with early feeding intolerance.

CONCLUSION

Very low-birth-weight infants with intrauterine growth retardation, increased umbilical artery resistance, and brain sparing tolerated enteral feeding as well as appropriate-for-gestational-age VLBW infants.

The subjective assessment of echogenic fetal bowel

OBJECTIVES

To assess the subjective interpretation of the echogenicity of fetal bowel compared to bone from antenatal ultrasound images taken during examinations conducted between 17 and 22 weeks of gestation.

METHODS

Eighty-seven women attending for their antenatal scan were selected in a random prospective manner over a 9-month period. Images of the fetal bowel were taken and evaluated by 10 sonographers, one consultant obstetrician and one consultant radiologist. Images from a further 13 fetuses, in which the subjective assessment of echogenic bowel was made, were also included. All ultrasound images were acquired on a dedicated ultrasound scanner, with a standard transducer, thermal paper printer and single operator using standardized equipment settings and reproducible image sections. Questionnaires with 100 sets of images of fetal bowel were distributed to the participants. Performance was assessed by means of percentage agreement and levels of chance corrected agreement (Kappa).

RESULTS

The subjective assessment of fetal bowel echogenicity is very variable. Intra- and inter-observer variation discrepancies in the assessment of bowel echogenicity compared to bone were demonstrated between the sonographers. Good agreement was identified between the consultants with good to almost perfect intra-observer agreement. Overall, only moderate agreement was observed between the sonographers and the consultants.

CONCLUSIONS

The lack of agreement demonstrated between sonographers when evaluating the echogenicity of fetal bowel should be addressed if this ultrasound marker is to be incorporated into routine fetal screening programs.

Enteral feeding of the micropremie

Clinical practice demands knowledge of gastrointestinal ontogeny and the factors that affect our ability to use enteral feeding in the micropremie. The decisions regarding milk type (when and how it should be given) are considered in the light of current physiologic and clinical evidence. Special considerations apply in the micropremie who is also small for gestational age and NEC must be avoided. Trophic feeding now has an established role, allowing the infant to benefit from enteral feeds even when full nutritive milk feeding is not possible.

Assessment of fetal cardiovascular function: ultrasound study of the fetal circulatory compartments

Recent advances in high-resolution ultrasonography combined with color-coded Doppler analysis have enabled a new insight to be gained into fetal physiology and allowed the investigation of small, previously inaccessible fetal vessels under normal and abnormal conditions. In addition, the findings in some cases contradict the accepted fetal pathophysiology derived from animal studies. The aim of the present study is to describe new reports assessing the major compartments of the fetal cardiovascular system (heart, lung, splanchnic and fetal venous circulations) and to discuss the developments in these fields.

Sonographic borderlands in the fetal abdomen

Ultrasonographic examination of the fetal abdomen is an integral part in all routine fetal sonograms and can provide significant information about the status and prognosis of the fetus. Although many types of fetal anomalies can be identified (i.e., gastroschisis, omphalocele, or congenital diaphragmatic hernia), there are several sonographic findings that are not clearly anomalous, but may be associated with poor fetal outcome. Echogenic fetal bowel, small or absent fetal stomach and fetal intra-abdominal calcifications all fall into this category. This article reviews the recent literature as it relates to these topics, including suggestions regarding the need for further action, and the types of further actions that are available to help identify abnormal fetuses and prevent unnecessary and/or invasive testing of normal ones.

Screening for chromosomal abnormality

Screening for fetal abnormalities has become one of the most high profile health care issues of modern times. This issue is predicated on major advances in health care technology that permit wider detection of fetal anomalies, including the development of more advanced biochemical markers and improvements in ultrasound imaging. The effectiveness of these screening methods and their rational application is a point of great controversy, and is the cause of considerable unease in clinical obstetrical practice. This article reviews the general concepts of fetal screening for fetal chromosome abnormalities and then focuses on certain aspects of ultrasound screening that are particularly controversial. The scientific basis for each ultrasound finding (e.g., nuchal translucency) is reviewed, as well as the frequently divergent clinical experience with the finding. Finally, a plea is made for the development of a more scientific database for fetal ultrasound screening, and the setting of fetal screening guidelines for practicing physicians based on diagnostic accuracy and cost-effectiveness.

Conflicting data on intervillous circulation in early pregnancy

According to classic embryological textbooks intervillous circulation is established early in the first trimester. This process starts with trophoblastic invasion of the decidua in which proteolytic enzymes facilitate the penetration and erosion of the adjacent maternal capillaries with formation of the lacunae. After the lacunar or previllous stage trophoblast invades deeper portions of endometrium with belonging spiral arteries. This gradual process finishes with direct opening of the spiral arteries in the intervillous space under the fully developed placenta. This classic concept of establishment of the intervillous circulation was challenged in 1987 and 1988 by the experiments of HUSTIN and SHAAPS. The authors believed that blood flow in the intervillous space is absent in incompletely development before 12 weeks of gestation. After the introduction of the new generation of far more sensitive color Doppler devices in the last few years, our group and several others reported a positive finding of intervillous circulation during the first trimester of pregnancy.

Echogenic fetal bowel in the third trimester associated with trisomy 18

We present the first case of trisomy 18 in which echogenic fetal bowel was detected in the third trimester after normal echogenicity was documented during the second trimester. Fetal karyotyping should be considered in cases of increased echogenicity of the fetal lower abdomen in the second as well as the third trimester.

Second-trimester echogenic bowel and intraamniotic bleeding: association between fetal bowel echogenicity and amniotic fluid spectrophotometry at 410 nm

OBJECTIVE

Our purpose was to determine whether the presence of heme pigments in amniotic fluid is associated with the ultrasonographic findings of increased fetal bowel echogenicity in the second trimester.

STUDY DESIGN

Spectrophotometric analysis of amniotic fluid for optical density at 410 nm was prospectively performed to study the presence of heme pigments in (1) 104 pregnancies undergoing second-trimester amniocentesis for routine cytogenetic indications and (2) in 14 pregnancies undergoing amniocentesis for prenatal karyotyping because of fetal strongly echogenic bowel. In the routine amniocentesis group the fetal small bowel echogenicity was assessed immediately before amniocentesis and classified as nonechogenic (n = 64), mildly echogenic (n = 36), or hyperechogenic (n = 4) with the fetal iliac wing and liver used as references. Only amniotic fluid specimens that were obtained at the first attempt and that were not blood-stained were included in this study, with the first milliliter being discarded in all samples.

RESULTS

In the routine amniocentesis group abnormal amniotic fluid optical density readings were significantly more frequent in fetuses with increased bowel echogenicity compared with those with nonechogenic bowel (8/40 [20%] vs 3/64 [5%], respectively; p < 0.001). In the hyperchogenic bowel group abnormal amniotic fluid optical density readings were found in four samples (29%). Overall, 12 of 54 fetuses (22%) with increased bowel echogenicity had a detectable peak at 410 nm. Three of the 12 (25%) fetuses with echogenic bowel and positive readings for hemoglobin were chromosomally abnormal.

CONCLUSIONS

Fetal small bowel echogenicity is associated with the presence of heme pigments in amniotic fluid as determined by amniotic fluid optical density at 410 nm. Swallowing of amniotic fluid after intraamniotic bleeding seems implicated in the etiology of second-trimester echogenic bowel in both euploid and aneuploid fetuses.