Page 123 - Clinical Manual of Small Animal Endosurgery

Diagnostic Laparoscopy 111

Fig. 4.4 Insufflating the abdomen by a Veress needle placed in the
midline slightly cranial to the umbilicus.

occlusion of the needle tip (due to placement against a viscus, within the
omentum or in a subcutaneous position). In this instance, the needle
should be gently manipulated in and out of the abdomen to dislodge
the occlusion, avoiding lateral movements in order to prevent injury to
nearby structures. If the pressure remains elevated, re-placement of
the needle is required. The abdomen at this point can be slowly insuf-
flated up to a pressure of 13–15 mmHg (12–13 mmHg in cats); this
can be reduced to 8–10 mmHg after port placement. When sufficiently
distended, the abdomen becomes tympanic upon palpation, and the
experienced operator can assess adequate separation between organs and
abdominal wall by ballottement. Overdistension is best avoided, as it
leads to decreased venous return and impairment in ventilation.
The trocar-cannula unit for the laparoscope can now be placed. The
entry site is chosen, and a skin and subcutaneous tissue incision adequate
for the size of the trocar is performed. Using an imprint of the cannula
tip on the skin as a template helps in ensuring the correct diameter of
the incision. This is very important, as an exceedingly large incision will
cause gas leakage around the cannula, and may also lead to cannula
dislodgement during instrument insertion or withdrawal. On the other
hand, with a skin incision too small the force required to penetrate the
abdominal wall will be increased, thus causing the trocar tip to get very
close to viscera. A haemostat can be used to bluntly separate the muscle
layers, to check incision size and minimise trauma to the abdominal wall.
If a threaded cannula is used, the skin incision should be slightly
larger than the diameter of the cannula, which could otherwise get
caught in the thread during cannula insertion. The fascial layer of the
abdominal wall need also to be incised when using a cannula without
trocar, which is introduced in the abdomen using a clockwise screw