THE ULTRASONIC APPEARANCE OF THE UMBILICAL CORD by Francois R. Morin, MD and Fred Winsberg, MD
ABSTRACT We have used a combination of linear-array real time and contact sector scanning to image the umbilical veins and arteries. The best images are made perpendicular to the cord. The arteries spiral the vein and the cord is a tortuous structure. Thus there is considerable variability of the appearance of the arteries and veins depending upon the plane of the section.
Indexing Words U1trasound
Obstetrics
F I G U R E 1. Late t h i r d trimester pregnancy. Short axis and long
Umbilical Cord
Placenta
FIGURE 2. "Mask" appearance in full-term pregnancy. N o t e t n e thick walls o f the arteries. Graticule is 1.0 c m .
axis cuts through the umbilical cord. For all figures, large arrows show veins, small arrows show arteries. Graticule is 1.5 cm.
INTRODUCTION
Improved ultrasonic techniques have directed attention toward identification of normal fetal anatomy and fetal abnormalities. One of the structures that has so far received little attention is the umbilical cord: this paper discusses the ultrasonic examination of the umbilical cord. From the Division of Ultrasound, Department of Diagnostic Radiology, The Montreal General Hospital. For reprints contact: Fred Winsberg, MD, Division of Ultrasound, Department of Diagnostic Radiology, The Montreal General Hospital, 1650 Cedar Avenue. Montreal, Quebec H 3 G 1A4.
324
METHOD AND RESULTS
The umbilical cord is readily identified in second- and third-trimester pregnancies with the use of real time instruments. By passing the scanner across the maternal abdomen, one searches the amniotic fluid for parallel linear echoes that pulsate at the fetal heart rate (I). Unfortunately, the unfocused linear array does not provide good enough visualization of the umbilical cord for short axis sections. Thus, our technique involves the combination of real time and articulated contact scanning. I C I' bol h 2Y5-3XZ ( 1 9 7 x 1 7 7 5 1 7 x OOOh-O3?4 sol O(I
IY7X
lohn Wile\ . i n d
\oil\
Inc
OOYI-
~
F I G U R E 3. Spiralling o f arteries a r o u n d vein is s h o w n because arteries can be seen on b o t h sides of t h e vein. G r a t i c u l e i s 1.5 c m .
~
F I G U R E 5. L o n g axis of u m b i l i c a l vein showing spitalling arter ies G r a t i c u l e i s 1 O c m
and the narrower structure is the artery (Figs.
2 , 5). In the full-term fetus, the veins are approximately 1cm in diameter, whereas the arteries are approximately 4 mrn in diameter (Fig. 3 ) . The arterial walls are somewhat thicker
F I G U R E 4. Fetal limbs are seen adjacent t o t h e c o r d . T h e p l a centa i s anterior. Grattcule i s 2 cm
Having identified the umbilical cord in its long axis using a multi-transducer sequenced array (ADR), we employ an articulated scanner (Searle Phosonic) to make sections at right anglcs t o the umbilical cord. It is thus possible t o identify the umbilical vein and the paired umbilical arteries adjacent to the umbilical vein (Figs. 1-5). When the complete pattern is identified, it has the appearance of a mask: the umbilical vein resembles the face and the umbilical arteries resemble eyes. Since the umbilical arteries are smaller in diameter than the umbilical vein, it is apparent that the long axis sections through the umbilical vein may show a wide and narrow channel lying adjacent to each other; the wider structure is the vein VOLUME 6 . N U M B E R 5
than the venous wall. Material that does not contain blood can also be seen in some sections (“Wharton’s jelly”). Obviously, the appearance of sections of the umbilical cord depends on the angle of the section and the curvature of the cord at the plane in which the section is made. Since the arteries spiral around the vein, the orientation of the arteries with respect t o the vein also varies (Figs. 3, 5). Although the cord can be identified regularly in the second trimester, it is only in the late second trimester that short axis sections can be obtained. Nonetheless, one may be able t o identify two umbilical arteries in some long axis sections (Fig. 5). Identification of the cord depends upon an adequate quantity of amniotic fluid. In full-term pregnancies in which there is oligohydramnios the cord may be impossible t o locate. DISCUSSION
The combination of real time and contact scanning permits cross-sectional images of the umbilical cord that demonstrate the umbilical vein and the paired umbilical arteries. This identification is of potential significance because a single umbilical artery is associated with fetal congenital anomalies, diabetes, twins, and increased neonatal mortality (2-5). A short axis section perpendicular to the umbilical cord resembles a mask in, which the umbilical vein looks like the face and the umbilical arteries look like eyes. Variants of this pattern are also 325
seen, depending upon the sectional plane. The most common appearance of the umbilical cord when viewed in long axis section is a wide and a narrow structure adjacent t o each other. There is now great interest in measuring umbilical flow using pulsed Doppler ultrasound. Identification of the cord is a prerequisite for measuring flow in the cord, but because the cord is quite mobile, such measurements will probably require real time as well as Doppler instruments. The intraabdominal umbilical vein is a more stable landmark.
326
REFERENCES 1. Hobbins, Winsberg: Ultrasonography and obstetrics and gynecology, page 85. Williams and Wilkins 1977. Baltimore. 2. Froehlich LA, Fujihura T: Follow-up of infants with single umbilical arteries. Paediatrics 52:6, 1973. 3. Bryan EM, Kohler HG: The missing umbilical artery. I. Arch Dis Child 49:844,1974. 4. Bryan EM, Kohler HG: The' missing umbilical artery. 11. Arch Dis Child 50:174,1975. 5. Pritchard JA, MacDonald DC: Williams OB 15th edition, page 473, Appleton-Century-Crofts, N Y 1976.
J O U R N A L O F CLINICAL ULTRASOUND
ABSTRACT We have used a combination of linear-array real time and contact sector scanning to image the umbilical veins and arteries. The best images are made perpendicular to the cord. The arteries spiral the vein and the cord is a tortuous structure. Thus there is considerable variability of the appearance of the arteries and veins depending upon the plane of the section.
Indexing Words U1trasound
Obstetrics
F I G U R E 1. Late t h i r d trimester pregnancy. Short axis and long
Umbilical Cord
Placenta
FIGURE 2. "Mask" appearance in full-term pregnancy. N o t e t n e thick walls o f the arteries. Graticule is 1.0 c m .
axis cuts through the umbilical cord. For all figures, large arrows show veins, small arrows show arteries. Graticule is 1.5 cm.
INTRODUCTION
Improved ultrasonic techniques have directed attention toward identification of normal fetal anatomy and fetal abnormalities. One of the structures that has so far received little attention is the umbilical cord: this paper discusses the ultrasonic examination of the umbilical cord. From the Division of Ultrasound, Department of Diagnostic Radiology, The Montreal General Hospital. For reprints contact: Fred Winsberg, MD, Division of Ultrasound, Department of Diagnostic Radiology, The Montreal General Hospital, 1650 Cedar Avenue. Montreal, Quebec H 3 G 1A4.
324
METHOD AND RESULTS
The umbilical cord is readily identified in second- and third-trimester pregnancies with the use of real time instruments. By passing the scanner across the maternal abdomen, one searches the amniotic fluid for parallel linear echoes that pulsate at the fetal heart rate (I). Unfortunately, the unfocused linear array does not provide good enough visualization of the umbilical cord for short axis sections. Thus, our technique involves the combination of real time and articulated contact scanning. I C I' bol h 2Y5-3XZ ( 1 9 7 x 1 7 7 5 1 7 x OOOh-O3?4 sol O(I
IY7X
lohn Wile\ . i n d
\oil\
Inc
OOYI-
~
F I G U R E 3. Spiralling o f arteries a r o u n d vein is s h o w n because arteries can be seen on b o t h sides of t h e vein. G r a t i c u l e i s 1.5 c m .
~
F I G U R E 5. L o n g axis of u m b i l i c a l vein showing spitalling arter ies G r a t i c u l e i s 1 O c m
and the narrower structure is the artery (Figs.
2 , 5). In the full-term fetus, the veins are approximately 1cm in diameter, whereas the arteries are approximately 4 mrn in diameter (Fig. 3 ) . The arterial walls are somewhat thicker
F I G U R E 4. Fetal limbs are seen adjacent t o t h e c o r d . T h e p l a centa i s anterior. Grattcule i s 2 cm
Having identified the umbilical cord in its long axis using a multi-transducer sequenced array (ADR), we employ an articulated scanner (Searle Phosonic) to make sections at right anglcs t o the umbilical cord. It is thus possible t o identify the umbilical vein and the paired umbilical arteries adjacent to the umbilical vein (Figs. 1-5). When the complete pattern is identified, it has the appearance of a mask: the umbilical vein resembles the face and the umbilical arteries resemble eyes. Since the umbilical arteries are smaller in diameter than the umbilical vein, it is apparent that the long axis sections through the umbilical vein may show a wide and narrow channel lying adjacent to each other; the wider structure is the vein VOLUME 6 . N U M B E R 5
than the venous wall. Material that does not contain blood can also be seen in some sections (“Wharton’s jelly”). Obviously, the appearance of sections of the umbilical cord depends on the angle of the section and the curvature of the cord at the plane in which the section is made. Since the arteries spiral around the vein, the orientation of the arteries with respect t o the vein also varies (Figs. 3, 5). Although the cord can be identified regularly in the second trimester, it is only in the late second trimester that short axis sections can be obtained. Nonetheless, one may be able t o identify two umbilical arteries in some long axis sections (Fig. 5). Identification of the cord depends upon an adequate quantity of amniotic fluid. In full-term pregnancies in which there is oligohydramnios the cord may be impossible t o locate. DISCUSSION
The combination of real time and contact scanning permits cross-sectional images of the umbilical cord that demonstrate the umbilical vein and the paired umbilical arteries. This identification is of potential significance because a single umbilical artery is associated with fetal congenital anomalies, diabetes, twins, and increased neonatal mortality (2-5). A short axis section perpendicular to the umbilical cord resembles a mask in, which the umbilical vein looks like the face and the umbilical arteries look like eyes. Variants of this pattern are also 325
seen, depending upon the sectional plane. The most common appearance of the umbilical cord when viewed in long axis section is a wide and a narrow structure adjacent t o each other. There is now great interest in measuring umbilical flow using pulsed Doppler ultrasound. Identification of the cord is a prerequisite for measuring flow in the cord, but because the cord is quite mobile, such measurements will probably require real time as well as Doppler instruments. The intraabdominal umbilical vein is a more stable landmark.
326
REFERENCES 1. Hobbins, Winsberg: Ultrasonography and obstetrics and gynecology, page 85. Williams and Wilkins 1977. Baltimore. 2. Froehlich LA, Fujihura T: Follow-up of infants with single umbilical arteries. Paediatrics 52:6, 1973. 3. Bryan EM, Kohler HG: The missing umbilical artery. I. Arch Dis Child 49:844,1974. 4. Bryan EM, Kohler HG: The' missing umbilical artery. 11. Arch Dis Child 50:174,1975. 5. Pritchard JA, MacDonald DC: Williams OB 15th edition, page 473, Appleton-Century-Crofts, N Y 1976.
J O U R N A L O F CLINICAL ULTRASOUND
