The kidney should not be in the field of view. The stomach is seen but not in relationship to the umbilical vein or portal sinus.
The long axis of the diaphysis of the femur is most accurately measured when the ultrasound beam of insonation is perpendicular to the shaft. The cartilage at the ends of the femur should not be included in the measurement. Only the diaphysis should be measured between the epiphysis, which represents the portion of the long bone formed by the primary ossification center.
The principles of HL measurement correspond to those of the femur. The insonation of the ultrasound beam is best directed in a perpendicular fashion and the diaphysis alone is measured after the forearm and shoulder region are identified. The fetal foot measurement is taken from the tip of the longest toe typically the second toe to the tip of the heal.
The ulna is longer than the radius. Note that it extends into the elbow, higher than the radius. The radius is on the thumb side and the ulna is on the 5th digit or little finger side of the forearm. Again, the measurement is easier to establish when the ultrasound beam is perpendicular to the long bone.
Among the bones of the lower leg, the fibula is smaller than the tibia. The tibia is longer than the fibula and the tibia originates closer to the knee compared to the fibula. The orbits and the lens of the eye can be viewed when both orbits are in a coronal or axial view and are most easily visualized when the fetal head is in a direct occiput posterior position.
The BOD is measured from the outer edge of one orbit to the outer edge of the other orbit. These measurements may be useful in assessing certain syndromes, potential karyotype abnormalities, severe growth restriction, or in assessing fetal age when other measurements are difficult to obtain.
The IOD represents the outer edge to outer edge distance between the orbits. It may be measured for the same reasons that BOD is measured and when facial anomalies are suspected. After being suspected of a uterine anomaly on two-dimensional scanning, 60 women were evaluated with 3-D ultrasound and with MRI. For bicorporeal uteri, the sensitivity was Among women who underwent a second trimester scan, a small percentage were incomplete due to unfavorable fetal position.
Only one view was needed in a subsequent scan in 2. The most difficult organs to visualize during the initial scan were: corpus callosum 1. Microcephaly can be present at birth or it may develop in the first few years of life [6]. Prenatally, Chervenak et al. The Society for Maternal-Fetal Medicine SMFM recommends that a detailed neurosonographic examination be done on fetuses with an HC greater than 2 standard deviations below the mean to look for findings such as intracranial calcifications, cerebellar hypoplasia and other abnormalities.
The finding of a sloping forehead should increase the index of suspicion for pathological microcephaly. The SMFM also advises the diagnosis of pathologic microcephaly is considered certain when the fetal HC is equal to or greater than 5 SD below the mean for the gestational age [4].
A follow up ultrasound in 3 to 4 weeks is recommended for fetuses with an HC more than 2 SD below the mean.
Pathological microcephaly is usually associated with abnormal neurological findings , mental retardation, and sometimes seizures. Causes of microcephaly include , but are not limited to, a chromosomal abnormality trisomy or deletion , a gene defect such as Smith-Lemli-Opitz, an infection such as rubella, cytomegalovirus CMV , toxoplasmosis, or possibly Zika virus, intrauterine fetal stroke, exposure to high doses of radiation, exposure to drugs such as alcohol, aminopterin ,or hydantoin, or a maternal condition such as phenylketonuria PKU.
Microcephaly Microcephaly refers to an abnormally small head defined as a head circumference HC of 3 standard deviations SD or more below the mean for the gestational age []. See also macrocephaly microcephaly.
Callen PW. Ultrasonography in Obstetrics and Gynecology. Elsevier Health Sciences. Read it at Google Books - Find it at Amazon. Related articles: Pathology: Genitourinary. Promoted articles advertising.
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