Trocar assistance

TTTS. Trocar assistance

The relationship between the trocar and the endoscope varies from manufacturer to manufacturer. Most of the endoscopes available for operative fetoscopy follow the hysteroscopy design, in which the tip of the endoscope is flushed with the tip of the trocar and the back end of the endoscope locks with the trocar sheath. 

In our design, the trocar and endoscope are independent of each other, with the endoscope being purposely 4 cm longer than the trocar length. Fluid leakage is prevented not by a locking mechanism, but rather, by a rubber cap and a check-flow valve within the trocar. With our specific trocar and endoscopic design, we have developed the concept of trocar assistance. 

Essentially, the trocar sheath can be used to expose the surgical field as would be accomplished with a second port. Basically, the trocar sheath is advanced to the target vessel while the endoscope remains 1–2 cm inside the trocar sheath. Once the target vessel is identified, laser photocoagulation of the vessel from within the trocar sheath can be accomplished. 

We have found trocar assistance to be quite useful in the treatment of patients with anterior placentas, or even in those with posterior placentas in which the vessels may be tangential to the angle of entry of the trocar. The vessel is identified and compressed beneath the trocar sheath, and the operating endoscope fired within the sheath to obliterate it (Figure 9.14a,b). Trocar assistance may also be useful to expose vessels within the sac of the donor twin, whether obscured by the donor twin or by the dividing membrane.