Trocar entry

TTTS. Trocar entry

In standard laparoscopy, the trocar insertion sites have been extensively worked out to avoid injury to the superficial epigastric vessels. In contrast, the site of entry into the amniotic cavity of the recipient twin will vary from patient to patient. 

The site of entry is chosen after careful preoperative mapping (Chapter 7) to avoid injury to the dividing membrane or the placenta. Injury to the superficial epigastric vessels is avoided by placing the trocar either at the midline or 8 cm lateral from the midline.15 Power angio Doppler insonation of the myometrium under the proposed site of entry may disclose important vessels that need to be avoided (Figure 9.9). 

A minimal skin incision is made at the chosen site using a No. 11 scalpel blade. It is important not to advance the scalpel blade too deep, as injury to the myometrium could occur, particularly in very thin patients. The insertion of the trocar is done under ultrasound guidance. 

The resistance of the rectus sheath can be felt. Once the fascia is overcome, the trocar is advanced up to the level of the myometrium, without entering the amniotic cavity yet. Again, care is taken not to injure any obvious myometrial vessels that may be apparent on power angio imaging. The amniotic cavity of the recipient twin is then entered in a swift fashion, to avoid dragging of the membrane. 

If the patient has not had genetic testing, the first few milliliters of fluid are discarded and an amniotic sample of 20–30 ml is obtained for karyotypic analysis. If a genetic amniocentesis or a therapeutic amniocentesis has been previously performed, a sample of amniotic fluid is sent for microbiological analysis.