Dale R. Cyr

Three-dimensional ultrasonic angiography using power-mode Doppler

To visualize the vascular anatomy of parenchymal organs, we have developed a system for producing three-dimensional ultrasonic angiograms (3D USA) from a series of two-dimensional power-mode Doppler ultrasound (PDU) scans. PDU scans were acquired using a commercial scanner and image-registration hardware. Two-dimensional images were digitized, and specially designed software reconstructed 3D volumes and displayed volume-rendered images. The geometric accuracy of our system was assessed by scanning a flow phantom constructed from tubing. The system was tested on patients by scanning native and transplanted kidneys, and placentas. Three-dimensional images of the phantoms depicted the spatial relationships between flow within the tubing segments and contained less than 1 mm of geometric distortion. Three-dimensional images of the kidney and placenta demonstrated that spatial relationships between vasculature structures could be visualized with 3D USA. Applications of this new technique include analysis of vascular anatomy and the potential assessment of organ perfusion.

Fetal bowel. Normal sonographic findings.

The normal sonographic appearance of fetal colon and small bowel is reported in a prospective study of 130 fetuses. The colon, which appeared as a continuous tubular structure located around the perimeter of the abdominal cavity, was seen in some fetuses as early as 22 menstrual weeks and in all fetuses examined after 28 weeks. Colon diameter demonstrated a linear relation (r = 0.82) with menstrual age, reaching a maximum of 18 mm at term. In comparison, small bowel was located centrally and individual segments never exceeded 7 mm in diameter or 15 mm in length. Small bowel loops were seen in only 30% of fetuses examined after 34 weeks. Peristalsis was routinely demonstrated of the small bowel, but was not observed in the colon.

The Dandy-Walker malformation prenatal sonographic diagnosis and its clinical significance.

To determine the usual sonographic findings and clinical significance of the Dandy‐Walker malformation (DWM) identified in utero, we reviewed seven proven cases diagnosed by prenatal ultrasound during a 6‐year period. All patients demonstrated complete or partial absence of the cerebellar vermis and a posterior fossa cyst. Other central nervous system (CNS) findings included hydrocephalus (five cases) and agenesis of the corpus callosum (one case). Extra‐CNS abnormalities were prospectively identified in 3 of 4 fetuses with multiple anomalies. Chromosomal analysis was performed on all four fetuses with multiple extra‐CNS anomalies, yielding 2 abnormal karyotypes (trisomy 18 and mosaic trisomy 13). Fetal mortality was directly dependent on the presence of extra‐CNS anomalies. Five fetuses ultimately died, including all four with multiple extra‐CNS anomalies. The remaining two patients are alive at 1.5 and 6 years of age. We conclude that DWM has a distinctive sonographic appearance that can be identified by prenatal ultrasound and that identification of DWM should initiate a careful search for concurrent anomalies as well as consideration of chromosomal analysis.

Prenatal diagnosis of an intrapericardial teratoma. A cause for nonimmune hydrops.

A 26-week gestation was referred to our Institution for the evaluation of a possible fetal thoracic mas!l. The mother was gravida 3, para 0, abortions 2, with no family history of con· genital disease. Sonographic evaluation demonstrated a breech fetus with growth parameters concordant with 26 weeks. Within the fetal thorax a 5 X 6 mm soft tissue mass was positioned on the rightside of the heart and appeared to con· tain small areas of echogenic foci. It was thought these foci could represent calcifications that were too small to cause acoustic shadowing. The heart was positioned normally within the chest. A large pericardia! effusion was also noted (Fig. 1). The fetal lungs were visualized in the posterior aspect of the thorax. Because the lungs were not surrounded or float·

Exencephaly--clinical and ultrasonic correlation to anencephaly.

&NA; The antenatal sonographic diagnosis of exencephaly in four gestations is reported. Exencephaly is an uncommon malformation of the cranium that characteristically involves a large, disorganized mass of cerebral tissue. The flat bones of the calvaria are absent, leaving the brain mass uncovered. Secondarily, anencephaly may develop as a result of prolonged exposure of the developing encephalon to amniotic fluid and trauma in utero. As in anencephaly, facial structures and the bony base of the calvarium are often preserved in exencephaly. Sonographically, the outstanding feature of exencephaly is the cerebral mass, with convolutions or “pseudo” sulcal patterns present. These findings correlate well with the pathologic examination and define a clinical entity that is incompatible with human life.

Efficacy of thromboresistant umbilical artery catheters in reducing aortic thrombosis and related complications

Previous in vitro and in vivo reports suggest that catheters constructed of polyurethane with heparin bonded to the surface (HB-PU) are less thrombogenic than catheters made of polyvinyl chloride (PVC). A randomized trial sufficiently large (power 80%) to detect a reduction in the incidence of umbilical artery (UA) catheter complications, including aortic thrombus formation, from 45% to 20% was conducted in 125 infants. The infants were monitored for complications possibly related to the use of a UA catheter, such as systemic hypertension and abnormalities of lower extremity perfusion. The presence of aortic thrombi was assessed by ultrasound study 3.5 +/- 1.2 (SD) days and 11.1 +/- 2.3 days after insertion of the catheter. The use of HB-PU umbilical catheters did not lead to a significant reduction in the incidence of complications and aortic thrombi compared with the use of PVC catheters. The lack of reduction may have been related to the prolonged duration of catheter use in both groups. A much larger study would have been required to detect a smaller, but perhaps clinically significant, reduction in catheter-associated complications.

Assessment of fetal and placental blood flow in primates using contrast enhanced ultrasonography.

Ultrasonographic contrast agents that stay within the vascular space and do not cross the placenta may permit differentiation between the maternal and fetal portions of the placenta and may be clinically useful for diagnosis of placental abnormalities. This study was performed to assess the effects of Levovist (Schering AG, Berlin) on the placental circulation and to determine whether hemodynamic effects on the fetus occur. Ten studies were performed in five pregnant macaques (median weight, 9.15 kg; range, 6.15 to 11 kg; median gestational age, 121 days; range, 34 days to term) under anesthesia. Gray scale, color, and duplex Doppler sonographic scans of the fetus and placenta were acquired using a 5 MHz curved array transducer. Fetal heart rate, resistive index, and systolic‐diastolic ratios were measured in the fetal middle cerebral artery, aorta, umbilical artery, and uterine artery before and after administration of contrast agent. The following dose regimen was tested: 5 ml of physiologic saline solution followed by 0.1 ml/kg of 300 mg/ml Levovist (diagnostic dose), 0.5 ml/kg of 400 mg/ml Levovist (maximum dose), and 5 ml physiologic saline solution. The order of diagnostic dose and maximal dose was randomized among animals. Color enhancement of the basal portions of the placenta was documented after administration of contrast agent. Heart rate and middle cerebral artery systolic‐diastolic ratio did not change between baseline and injections. A 7% decrease of the resistive index from baseline to maximum dose was measured in the uterine artery (not significant). A 7.7% decrease in the systolic‐diastolic ratio from baseline to maximum dose was recorded in the umbilical artery. However, an identical change was measured after saline solution was injected. The resistive index in the aorta increased by 2.6% from baseline to maximum dose, a change that was not significant (P > 0.5). Ultrasonographic contrast enhancement of the maternal circulation in placenta is demonstrated to be without significant effects on the fetal circulation as measured in this limited population.

Isolated fetal choroid plexus cysts and karyotype analysis: is it necessary?

The purpose of this study was to evaluate the risk of fetal aneuploidy in the presence of isolated choroid plexus cysts and to evaluate the results obtained from our institution and those reported previously in the English literature. All patients with fetal choroid plexus cysts on prenatal ultrasonography were offered genetic counseling and amniocentesis for fetal karyotyping. Seven of 274 fetuses, 2.6% (95% confidence interval = 1.0 to 5.2%), with isolated choroid plexus cysts were aneuploid. Literature analysis located 23 other reports of 1537 fetuses with isolated choroid plexus cysts; 26 were karyotypically abnormal, 1.7% (95% confidence interval = 1.0 to 2.4%). When evaluating only those patients whose indication for amniocentesis was choroid plexus cysts (i.e., eliminating those patients with advanced maternal age or abnormal serum screening) the risk of having a fetus with trisomy 18 changed little, 1.9% (95% confidence interval = 0.4 to 5.5%). Our data, combined with those of the literature, suggest that the risk of finding an abnormal fetal karyotype in the presence of isolated choroid plexus cysts is at least 1% and may be as high as 2.4%. On the basis of these results, genetic counseling and prenatal diagnosis should be offered to these patients.

Prenatal diagnosis of agenesis of the corpus callosum.

The prenatal sonographic findings in seven cases of agenesis of the corpus callosum (AGCC) are reported. Findings that suggest AGCC on standard transverse views of the fetal cranium are emphasized. All seven cases demonstrated ventricular abnormalities including four fetuses (57%) who demonstrated laterally displaced lateral ventricles and/or disproportionate enlargement of the occipital horns. Two additional fetuses demonstrated a large midline fluid collection, representing a dilated third ventricle. The remaining case demonstrated atypical findings of a septated periventricular cystic mass. Following birth, additional malformations were found in 5 of the 7 fetuses (71%), including one fetus with trisomy 8. We conclude that AGCC can be suggested on the basis of prenatal sonographic findings and that awareness of typical findings should permit more frequent detection of this anomaly in utero. Due to the frequency of concurrent anomalies, identification of AGCC should initiate a careful search for additional malformations.

Rate-based management of fetal supraventricular tachycardia.

We reviewed the ultrasonographic studies and the clinical course of 22 fetuses with supraventricular tachycardia to determine whether the heart rate alone could serve as a basis for conservative management. Hydrops was not encountered with heart rates under 230 beats per minute. The conditions of all 22 fetuses stabilized without invasive administration of medications. Eighteen were delivered vaginally and only four by cesarean section. No fetal or neonatal losses occurred. Regardless of the type of supraventricular tachycardia, reducing heart rate in these fetuses to levels preventing or resolving hydrops allowed term vaginal delivery, thereby reducing the substantial problems of ventilating an immature or hydropic neonate.