The overall goal of the following experiment is to study the angio architecture of Monochorionic placenta using color dye injection of the vascular anastomosis. After acquisition, the placenta is first washed and trimmed. Then catheters are inserted into the umbilical vessels.
Next color dye is injected through the catheters in order to demonstrate the number type and size of the vascular anastomosis. Finally, the various patterns of vascular anastomosis present in the monochorionic placentas can be identified in the DY vessels. Though this method can provide insight into twin to twin transfusion syndrome or TTTS.
It can also provide important information about other monoclonic twin placentas such as twin anemia, polycythemia sequence, or taps, or selective intrauterine growth restriction. Generally, individuals new to this method will struggle because catheterization of the umbilical vessels may require some expertise and a certain learning curve. I will demonstrate this procedure together with a colleague from our fetal therapy center.
Fem Inspect the maternal and fetal surface of the placenta for completeness or disruption. A section of the dividing membranes can be sent to pathology To confirm the type of choic, the placenta can be placed in a plastic bowl and refrigerated up to one week until the final examination and color dye injection wash the placenta with warm water. Next, trim the peripheral membranes.
Remove the intertwine dividing membrane and peel off the amnon. Now transect each umbilical cord at approximately five centimeters. Distance from the cord insertion.
Gently squeeze out the blood clots from the umbilical and placental vessels, and then identify the umbilical vein. Performing a cannulation and subsequent D injection are the most difficult of this procedure. Accurate injection requires care and patience.
Rough handling, particularly during the catheterization, can result in leakage of dye outside the vessels. To facilitate why the dissemination of the dye, we recommend that one person injects while another gently massages the dye into the vessels, Cannulate the umbilical vein with an appropriately sized catheter, avoiding false passages using tweezers. Widen the lumen of the artery.
Again, avoid false passages. Then cannulate one umbilical artery with a smaller catheter. Repeat both cannulation steps for the other umbilical cord.
Facilitate the placement of the catheters by gentle back and forth massage of the umbilical vessels. Then tie a piece of tape around both cords to avoid backflow of the colored dye during dye injection. Before beginning, feel two 20 milliliter syringes with contrasting colored dyes.
Next, attach one syringe to the umbilical vein catheter and one to the umbilical artery catheter of one of the umbilical cords. Then using low pressure, gently inject the dye into the umbilical vein, while an assistant gently pushes the dye in the vein. To allow the dye to fill all the placental vessels, pay particular attention to the small vessels near the vascular equator where the anastomosis from either twin connect with each other.
Now fill the umbilical artery with the second dye, again, using low pressure and assistance to transfer all of the dye into all of the arterial spaces. Then fill two more 20 milliliter syringes with contrasting colored dyes and attach and inject the contents of each syringe into the umbilical vein and umbilical artery, using the same techniques as before. For the second umbilical cord, carefully examine the vascular equator and record the number and types of anastomosis.
Place a measuring tape on the placenta for measuring of the diameters and placental shares in the digital pictures. Then using a high resolution digital camera photograph the injected placenta. The placental angio architecture in twins varies according to the type of monochorionic twin pregnancy, as shown here in a monochorionic placenta from a normal uncomplicated monochorionic twin pregnancy, several arterial venous or AV anastomosis seen here from the green arteries and pink veins, and indicated by the white stars several eno arterial or VA anastomosis here represented by blue arteries and yellow veins, and further indicated by the green stars and one large arterial arterial or AA anastomosis identified by the mixing of the blue and green dye and denoted by the blue star are present here.
A monochorionic placenta from a twin to twin transfusion syndrome or TTTS pregnancy treated with serial amnio reduction shows the presence of only AV indicated by white stars and VA indicated by the green stars anastomosis without an AA anastomosis shown here is A-T-T-T-S placenta after scopic, laser coagulation of the vascular anastomosis using the selective laser technique in which a small residual anastomosis denoted with a white star was inadvertently left patent. With the selective laser technique, the vascular anastomosis are first identified and then subsequently coagulated one by one. This figure shows another TTTS placenta after scopic laser coagulation using the Solomon technique in which after identification and coagulation of each individual anastomosis, the complete vascular equator was coagulated from one placental margin to the other twin anemia polycythemia sequence or taps.
Placenta are characterized by the presence of only a few minuscule AV anastomosis. An example of which is shown here in which only minuscule anastomosis indicated by the white stars are visible. The placenta share of the taps recipient is often plethoric as seen here on the left side of the placenta, whereas the placenta share of the donor as seen here on the right is pale.
Shown here is a monochorionic placenta from a twin pregnancy with selective intrauterine growth restriction of one twin. The growth restricted fetus had ave cord insertion and a much smaller placental share. A large AA anastomosis is clearly visible denoted by the white star and a large AV anastomosis indicated by the green star AA anastomosis are often present in monochorionic placenta from twins with birth weight discordance, monochorionic mono amniotic placenta have a characteristic angio architecture with a short distance between both cord insertions as seen in this figure.
Note, the several AV VA and two AA anastomosis as indicated by the green, blue and white stars respectively, and the short distance between both cord insertions. While attempting this procedure, it's important to remember that AV anastomosis can be extremely small and difficult to visualize. The injection procedure must be performed meticulously to evaluate the presence of small residual AV anastomosis after laser surgery for TTTS after its development.
This technique paved the way for researchers in the field of fetal surgery to explore and improve laser coagulation techniques for monoclonic twin gestations with TTTS.
