Daily Archives: 22/12/2021

Fracture In Utero

The detection of rib or long bone fractures in association with severe micromelia suggests a diagnosis of osteogenesis imperfecta. Fractures may be subtle or may lead to angulation.

Fig 1, Fig2, Fig 3

The major differential diagnoses for fractures in utero are as follows:

• Osteogenesis imperfecta type II (most common)
• Hypophosphatasia (rare)
• Campomelic dysplasia (not a true fracture but bowing).

Fig 1:  Fracture in utero  Longitudinal scan of upper extremity: poorly ossified and fracture in osteogenesis imperfecta type IIA

Fig 2:  Callus formation of long bone  Longitudinal scan of humerus and femur: irregularity due to callus (arrowhead) in osteogenesis imperfecta type IIA

Fig 3:  Rib fractures  Multiple rib fractures with poor ossification in the fetus with osteogenesis imperfecta type IIA

Sonolucent Bones

Diffuse demineralization of the skull and long bones almost always occurs with fetal skeletal dysplasia syndromes. In the case of severe demineralization of the bony calvarium, the cranium is thin without an acoustic shadow and so poorly ossified that the intracranial structure can easily be seen. This increased visualization of the intracranial structures may be confused with such abnormalities as exencephaly due to acrania or acalvaria. Unlike exencephaly, however, there is an intact but poorly ossified skull. Careful scanning reveals concomitant limb anomalies.

Fig 1, Fig 2, Fig 3, Fig 4

The main differential diagnoses of the sonolucent skull are as follows:

• Osteogenesis imperfecta (most common)
• Hypophosphatasia (rare)
• Achondrogenesis type I (rare).

Fig 1:  Hypophosphatasia  Longitudinal scan of long bones: shortened and poorly ossified bones

Fig 2:  Poorly ossified and compressible skull   Cross-sectional scan of skull: deformable skull with sonolucency in osteogenesis imperfecta type IIA

Fig 3:  Micromelia in Thanatophoric dysplasia   Severe shortenings of long bones (arrow) but normal ossification

Fig 4:  Sonolucent and shortened arm   Longitudinal scan of the arm: Sonolucent and shortened humerus (*) in case of achondrogenesis

Bone Shortening

All long bones should be measured in each extremity, although subjective evaluation may be sufficient in most cases. The severity of bone shortening varies from extreme to mild.

Fig 1, Fig 2, Fig 3

The major differential diagnoses of bone shortenings are as follows:

Severe shortening

• thanatophoric dysplasia (micromelia) (common)
• osteogenesis imperfecta type II (micromelia) (common)
• achondrogenesis (micromelia) (common)
• short-rib polydactyly syndrome (uncommon)
• diastrophic dysplasia (uncommon)
• homozygous achondroplasia (uncommon)
• mesomelic dysplasia (uncommon)
• chondrodysplasia punctata, rhizomelic type

Mild-to-moderate shortening

• osteogenesis imperfecta type II (common)
• heterozygous achondroplasia (common)
• asphyxiating thoracic dysplasia (common)
• campomelic dysplasia (uncommon)
• hypophosphatasia (uncommon)
• chondroectodermal dysplasia (uncommon).

Fig 1:  Long bone shortening   Longitudinal scan of the thigh and leg: shortening of thigh and leg, compared with foot (achondrogenesis)

Fig 2:  Short humerus  Longitudinal scan of long bones: shortened but well ossified humerus of the fetus with Juene syndrome

Fig 3:  Micromelia in Thanatophoric dysplasia   Severe shortenings of long bones (arrow) but normal ossification

Normal Examination

Normal Spine

Fig 1, Fig 2, Fig 3, Fig 4, Fig 5, Fig 6

–     Mineralization of the spine begins at 8 weeks of gestation. The three ossification centers of individual vertebrae include a single ventral center for the vertebral body (centrum) and two paired dorsal centers that will become the lateral masses and the posterior arch. They are well visualized from 15 to 16 weeks onwards. However, spina bifida can be detected much earlier. The posterior ossification centers begin at the base of the transverse processes. As ossification progresses, the laminae become visible, usually after 19 weeks. The inward angulation of the normal laminae is the opposite of the outward splaying of the laminae seen in spina bifida, an optimal situation for detecting this anomaly. The arch of the upper sacral region is not consistently recognizable until after 25 weeks.

• Technique of examination: The spine can be systematically examined during the second and third trimesters as follows:
  • Adjust the transducer on the maternal abdomen to achieve a cross-section image of the fetal abdomen or thorax.
  • Identify the location of the fetal spine, noting the acoustic shadow behind the spine, and carefully adjust the transducer to demonstrate all three ossification centers.
  • To obtain the sagittal view, from the previous image, make an attempt to bring both posterior centers to the middle of the image, lying horizontally or perpendicular to the ultrasound beam, and then rotate the transducer 90 degrees and meticulously adjust it to obtain the best image of the coronal view.
  • To obtain the coronal view, from the cross-section image, make an attempt to bring both posterior centers to the middle of the image, lying vertically or parallel to the ultrasound beam, and then rotate the transducer 90 degrees and meticulously adjust it to obtain the best image of the coronal view.
• Evaluation of the three views of the spine:
  • On the transverse (axial) view, the anterior ossification center (vertebral body) and posterior ossification centers (pedicles, transverse processes, laminae, and spinous processes) may all be identified as echogenic structures. This view may be superior to longitudinal views in demonstrating small spinal defects, since all three ossification centers can be imaged simultaneously.
  • On the sagittal view, many vertebrae can be visualized on a single image. The curvature can be best evaluated<?is this sentence complete enough?>. The normal spine appears as two parallel lines formed by the vertebral bodies anteriorly and the ossification centers of the lateral processes converging in the sacrum. The lines correspond to the posterior elements of the vertebrae and the vertebral body. This view can optimally demonstrate interruption of the overlying integument when myelomeningocele is present.
  • On the coronal view, many vertebrae can be visualized on a single image. Hence, scoliosis, hemivertebrae, and disorganized vertebrae are optimally visualized on this view. <?can you check the following sentence>The images oriented through the dorsal ossification centers can demonstrate the two parallel rows of echogenicity in these centers and also the extent of a dysraphic defect compared to adjacent vertebrae in the case of spina bifida.

Fig 1:  Normal spine   Cross-sectional scan of the abdomen: posterior ossification centers of spine align vertically

Fig 2:  Normal thoracic spine  Coronal scan of the thoracic spine: normal echodensity and alignment

Fig 3:  Normal spine :   Cross-sectional scan of the abdomen posterior ossification centers of spine align horizontally (arrow = anterior ossification center)

Fig 4:  Normal spinal curvature  Sagittal view of the spine: normal curvature (arrow) with complete overlying skin

Fig 5:  Normal lumbar spine  Coronal scan of the lumbar spine (arrowhead) (arrow = iliac bone)

Potential pitfalls:

• • Incomplete ossification: Scanning in early pregnancy reveals incomplete ossification of the lateral centers. Hence, on the transverse view, the posterior centers may appear to be parallel to one another rather than converging to the midline. This may be misinterpreted as spinal dysraphism.
  • Pseudodyspharism: On the coronal plane of the cervical and lumbar spine, the two parallel lines of posterior centers normally diverge. This divergence should not be mistaken for a spinal dysraphism.
  • Pseudodyspharism: <?please check the following sentence>On the transverse scan of the lumbosacral spine, if the ultrasound beam angled obliquely across the vertebral body of one vertebra but missed the posterior element or the posterior centers of another, this could simulate dyspharism. A normal appearance is restored when the ultrasound beam is reoriented perpendicular to the spinal axis.
• High-quality sonograms can also show the spinal cord within the spinal canal. The central canal is readily detectable within the cord. The more echogenic cauda equina (nerve roots) can be seen distal to the conus medullaris (distal spinal cord). With growth of the spine, the position of the conus medullaris ascends with gestational age.
• The spinal cord neural tissue, like that of most brain tissue, is echopenic. The conus medullaris and the craniocervical junction can be seen, albeit inconsistently, in nearly all fetuses by 18-20 weeks. The tissues surrounding the cord (leptomeninges) are brightly echogenic, as are those that surround the brain, and the dura is usually also seen discretely as a linear bright reflector. In fetuses with myelomeningoceles, determination of the most cephalic spinal level lesion is an important factor in prognosis. This level can be determined by counting up from the last ossified vertebral segment.

Normal Examination

Normal limbs

      Fig 1, Fig 2, Fig 3, Fig 4, Fig 5, Fig 6, Fig 7, Fig 8

1. Development: During the 8th week from the last menstrual period (LMP), a hyaline cartilage outline of the future appendicular skeleton begins to appear. The primary ossification centers of a long bone are located in the center of the shaft (diaphysis) and appear between weeks 7 and 12. Transabdominal and transvaginal sonography can clearly define the fetal skeleton even in the first trimester. The secondary ossification centers located in the epiphyses are at the distal ends of the long bone. During bone growth, the epiphyseal plate intervenes between the epiphysis and the end of the diaphysis (i.e. metaphysis). When the epiphyseal plate is replaced by bone, growth of the bone ceases. By 15-16 gestational weeks both the appendicular and axial skeleton can be consistently well imaged by sonography, although phalanges may be difficult to perceive in some instances. In the second trimester, the scapula, clavicle, humerus, radius, ulna metacarpals, femur, tibia, fibula, metatarsals and phalanges can be appreciated well sonographically in most cases.
2. Systematic approach: All long bones should be visualized with a systematic and routine sonographic approach to minimize errors in detecting limb defects. For example, in a survey of the upper limbs, the scapula should first be located and then the probe is laterally moved to identify the humerus, which at first may be in the cross-section or longitudinal view of the long bones. After completion of the upper arm assessment, the transducer is moved to visualize the distal end of the humerus or the elbow joint and then the probe is meticulously adjusted to locate the proximal end of the radius and ulna. Similarly, after thorough examination of the forearm the wrist joints and hands will be demonstrated respectively. The lower survey must be approached in the same way from the iliac wing through the foot.
3. Identification of long bones: The simple technique to identify the types of long bones is to obtain planes of sections that traverse the short axis of the limb. Such a plane through the forearm and calf will demonstrate two bones. In the lower leg, the more lateral bone is the fibula, and the medial bone is the tibia. The tibia and fibula and radius and ulna end at the same level distally, however, proximally the ulna is longer than the radius. This allows ready differentiation of these two bony sets and of the radius from the ulna in the upper extremity set.
4. Femur length measurement: Femur length measurement is usually used as a means of predicting gestational age. The measurement is technically the easiest of the most common biometric measurements. The transducer need only be aligned to the long axis of the bone to obtain a proper plane of the section. Only the ossified portions of the diaphysis and metaphysis are measured. The cartilaginous ends of the femur are excluded.
5. Identification of hands: With patience one can usually visualize all four fingers and the thumb. The hand is frequently clenched in a fist-like fashion, which can complicate the counting of fingers. The toes, although smaller than the fingers, can be seen relatively well. If difficulty arises, it is usually the functionally less important fourth and fifth toes that are not seen.
6. If a skeletal dysplasia is suspected early in the second trimester, a follow-up study to assess the interval long bone growth should be performed. The growth rate of the long bones decreases before the absolute length falls below the cut-off point.
7. Fetal parts ratios: The proportions between specific fetal body parts may be helpful in the diagnosis of a skeletal dysplasia. For example, foot length is not affected by most skeletal dysplasias whereas most other long bones are affected. In a normal fetus, the femur length/foot ratio (age-independent) is approximately equal to 1, and can effectively distinguish skeletal dysplasias from fetal growth restriction. Furthermore, the femur/head circumference and abdominal circumference/thoracic circumference ratios are also reliable for the detection of severe skeletal dysplasia.
8. Degree of skeletal ossification: This should be routinely assessed, although it is usually evaluated by subjective impression. Examination of the acoustic shadow and the echogenicity of the bone itself are often helpful. However, the degree of skeletal ossification cannot be well judged. Only in the most extremely osteopenic bone can one appreciate diminished ossification on sonograms.

Fig 1:  Normal scapula  Coronal plane of the scapula: triangular shape

Fig 2:  Normal upper limb

Fig 3:  Normal radius and ulna   Note: proximal end not in the same level (arrow)

Fig 4:  Normal hand

Fig 5:  Normal hand in late first trimester

Fig 6:  Normal femur   Longitudinal scan of femur: standard plane for femur measurement

Fig 7:  Normal tibia and fibula  Note: proximal and distal end of the both bones are in the same level

Fig 8:  Normal toes

Pitfalls

1. Fetal position: The fetal position is very important for a complete examination. All limbs are best visualized when floating freely in the amniotic fluid and imaging is difficult when they are tucked under the fetal body. Usually the limbs are readily imaged when the fetus is in the supine position whereas the posterior elements of the spine may be easily imaged in prone or decubitus positions.
2. FL measurement error: A non-osseous tissue at the end of the femur can give equal brightness. Reflection is returned from tissues distal to the epiphyseal plate but in immediate contiguity with the distal femoral metaphysis.
3. Short long bones: A fetal long bone length greater than 2 standard deviations below the mean for the gestational age does not necessarily indicate the presence of a skeletal dysplasia. Other possibilities for short fetal long bone include a normal physiologic variation in bone length, intrauterine growth restriction and chromosome abnormalities and other syndromes that may have a skeletal abnormality as part of their presentation.

Bladder and Cloacal Exstrophy

This is a rare congenital anomaly characterized by the exteriorization of the viscera on the abdominal surface, low insertion of the umbilical cord, divergent pubic rami and abnormal exterior genitalia. Bladder and cloacal exstrophy share a common embryologic origin in abnormal cloacal development, but are different in terms of severity and extent of involvement. Bladder exstrophy is a lower abdominal wall defect with herniation of the bladder whereas cloacal exstrophy is much more complex, including omphalocele, bladder exstrophy, imperforate anus, spine malformation (also known as OEIS complex), spina bifida and intersex.

Incidence: Sporadic occurrence with a prevalence of 1 in 30,000 births with a male to female ratio of 2:1 for bladder exstrophy, 1 in 50,000 births with a higher frequency in twins for cloacal exstrophy, and 1 in 200,000-300,000 for OEIS complex.

Sonographic findings:

• Soft tissue mass at the lower abdominal wall
  Fig 1, Fig 2, Fig 3, Fig 4
• Persistently absent fetal bladder with a large midline infraumbilical cystic or solid mass.
• A large cystic mass in the pelvis representing a persistent cloaca can be seen in some cases.
• Omphalocele is usually seen.
• Lumbosacral abnormalities.
• Associated anomalies such as renal agenesis, myelomeningocele, horseshoe kidney, and clubfeet.
• Umbilical arteries running alongside the mass suggestive of bladder exstrophy.

Fig 1:  Bladder extrosphy  Sagittal view of the fetal abdomen: complex extra-abdominal mass (*) below the umbilicus, finally proven to be bladder extrosphy

Fig 2:  Cloacal extrosphy  Free floating complex mass (*) connecting with fetal perineum

Fig 3:  Cloacal extrosphy  Free floating complex mass (*) connecting with fetal perineum

Fig 4:  Cloacal extrosphy  Free floating complex mass (solid circle) connecting with fetal perineum, abnormal fetal limb (arrow) (* = femur)

Associations: Genital defects in both conditions; renal, skeletal, neural tube, intestinal, cardiovascular and omphaloceles defects in cloacal exstrophy.

Management: Termination of pregnancy can be offered when diagnosed before viability. Isolated bladder exstrophy requires postnatal surgery, either with initial repair using the staged approach or a complete primary repair technique with continent diversion. Neonatal assignment of genetic males to the female sex is often necessary in cloacal exstrophy because of severe phallic inadequacy resulting in unpredictable sexual identification.

Prognosis: Recently good in isolated bladder exstrophy, but poor in cloacal exstrophy, with a high rate of urinary tract infection in adult women with sexual problems in several cases.

Recurrence risk: Sporadic (rare recurrence) but there is a significant genetic predisposition in some familial cases.

Limb-Body Wall Complex (LBWC)

LBWC or body-stalk anomaly or cyllosomas is a complex set of disruptive abnormalities consisting of failure of the anterior abdominal wall to close, short umbilical cord, disruption of the lateral body wall, distinctive scoliosis of the spine, limb defects, non-fusion of the amnion and chorion. Therefore, the amnion does not cover the cord but extends as a sheet from the margin of the cord to be continuous with the body wall and placenta.

Incidence: Sporadic, 1 in 15,000 (1:3000-42,000) births; a higher incidence was observed among mothers with a history of cigarette, alcohol and marijuana use.

Sonographic findings:

• Large body wall defect allowing abdominal contents to herniate. Fig1, Fig2
• The umbilical cord is absent or is a very short segment with a single umbilical artery. Fig3, Fig4
• The fetal abdomen is connected directly to the placenta.
• Scoliosis is evident in most cases. Fig5, Fig6
• Limb anomalies in most cases, including clubfeet, oligodactyly, arthrogryposis, absence of limbs, single forearms, split hand and feet.
• Craniofacial defects frequently seen.
• An extremely elevated level of maternal serum-alpha-fetoprotein (MSAFP) is also indicative of LBWC.
• Other associated anomalies.
• Three-dimensional ultrasound may be helpful.
• For first trimester diagnosis, the upper part of the fetal body is in the amniotic cavity, whereas the lower part is in the coelomic cavity.
• Differential diagnoses include other types of abdominal wall defects and amniotic band syndrome which may have very similar features.
• Pitfalls: Some cases have been initially misdiagnosed as omphalocele or gastroschisis, for which the prognosis is much better.

Fig 1:  Limb-body wall complex  Free floating complex mass containing abnormal shaped liver (solid circle) and bowel (*)

Fig 2:  Limb-body wall complex  Free floating complex bowel (arrow) and liver (solid circle) in the amniotic fluid

Fig 3:  Limb-body wall complex  Free floating complex mass containing liver (*) with covering membrane (arrowhead), short umbilical cord (arrow) originating from the placenta to the mass

Fig 4:  Limb-body wall complex  Free floating complex mass containing liver (*) with short umbilical cord (arrow) originating from the placenta to the mass

Fig 5:  Kyphoscoliosis   Sagittal scan of the fetal trunk: disorganized spine in association with limb-body wall complex

Fig 6:  Disorganized spine  Coronal scan of the fetal spine: disorganized spine (arrow) in association with limb-body wall complex

Associations: Other than typical defects, other anomalies are also often seen, especially craniofacial or neural tube defects.

Management: Termination of pregnancy can be offered.

Prognosis: Uniformly fatal.

Recurrence risk: Sporadic (rare recurrence).

Gastroschisis

Gastroschisis is a paraumbilical defect involving all the layers of the abdominal wall. It is usually right-sided with the small bowel herniated through the defect. The stomach or other organs may occasionally be involved in herniation.

Fig 1

Incidence: 1 in 2000-5000 live births with a high prevalence among the maternal age of 11-19 years. It has been associated with various medications including recreational drugs, NSAIDs (aspirin, salicylate, ibuprofen), and decongestants (pseudoephedrine and phenylpropanolamine) . There has been a sustained increase in the incidence over the past decade, particularly in teenage women.

Sonographic findings:

• Abdominal organs herniate through an anterior abdominal wall defect; typically, there are multiple loops of bowel outside the abdomen. Fig2, Fig3, Fig4
• No covering membrane.
• Umbilical cord inserting on the abdominal wall (normal insertion site). Fig5, Fig6
• Varying degrees of bowel dilatation and wall thickening or increasing intraluminal meconium. Fig7, Fig8, Fig9
• The liver is very rarely involved. Fig10
• The amniotic fluid volume is usually normal, however, oligohydramnios may be observed in 36% of cases. Polyhydramnios may be seen in the case of bowel obstruction.
• An increase in serum alpha-fetoprotein levels, higher than those associated with omphalocele.
• Doppler velocity of the superior mesenteric artery found to be predictive of outcome in fetuses with gastroschisis.
• Usually first diagnosable in the early second trimester; the diagnosis prior to 13 weeks may be confused with physiologic herniation.
• Pitfalls: The cases with oligohydramnios, particularly in late pregnancy, can easily be missed. Additionally, extra-abdominal bowel can be overlooked and thought to be a coiled umbilical cord.
• Differential diagnoses include other types of abdominal wall defects (see omphalocele), especially ruptured omphalocele, though rare, limb-body wall complex, and tangled cord adjacent to the fetal abdomen, in which color flow will show vascular flow.
• Most standard ultrasound parameters are not significantly associated with an adverse neonatal outcome, except for polyhydramnios, which was strongly predictive of severe bowel complications in the neonatal period.

Fig 1:  Schematic drawing of gastroschisis; note normal location of the cord insertion

Fig 2:  Gastroschisis   Scan of the free-floating bowel loops in the amniotic fluid

Fig 3:  Gastroschisis  Cross-sectional scan of the abdomen: Free floating dilated bowel loops (arrow) in the amniotic fluid (arrowhead = spine, * = intra-abdominal stomach)

Fig 4:  Gastroschisis  Cross-sectional scan of the abdomen: bowel (arrowhead) protruding through the abdominal wall defect on the right-side of the umbilicus (arrow = umbilical vein)

Fig 5:  Gastroschisis  Cross-sectional scan of the abdomen: free floating bowel in the amniotic fluid on the right side of the umbilical vessels (*) protruding through the abdominal wall defect

Fig 6:  Gastroschisis   Cross-sectional scan of the abdomen: Free floating bowel loops (arrow) in the amniotic fluid, protruding through the abdominal wall defect on the right-side of the umbilical vein (*)  (solid circle = intra-abdominal stomach)

Fig 7:  Gastroschisis  Free floating dilated bowel loops in the amniotic fluid

Fig 8:  Gastroschisis   Free floating dilated bowel loops (*) in the amniotic fluid

Fig 9:  Gastroschisis  Free floating bowel loops (*), thickened wall caramelized by the turbid amniotic fluid

Fig 10:  Gastroschisis   Cross-sectional scan of the abdomen: liver mass (arrow) and bowel (arrowhead) without covering membrane protruding through large defect, note normal cord insertion (*) (solid circle = spine)

Associations: Related to other anomalies in 7-10% of cases, mostly GI anomalies, not associated with chromosomal abnormalities.

Management: Serial sonographic monitoring is necessary to evaluate the degree of dilation and wall thickness. Early delivery may be beneficial in cases of marked dilatation or thickened bowel wall, however, term delivery gives the best outcomes in most cases. Delivery should be performed in a tertiary center with appropriate facilities for surgical management of the newborn. The fetuses may carry a higher rate of fetal distress and intrauterine death and fetal surveillance is recommended, however, labor and ruptured membranes do not appear to be associated with increased neonatal morbidity or mortality rates in neonates with gastroschisis. Cesarean section probably does not improve the outcomes.

Prognosis: Good but complications are very common, especially those related to the gastrointestinal tract problems and prematurity, increased morbidity in cases of bowel obstruction, bowel wall thickening, or increased amniotic concentration of digestive compounds.

Recurrence risk: Sporadic except for rare familial cases.