Ancillary cannulas are necessary to perform most diagnostic and operative laparoscopic procedures. Most currently available disposable ancillary cannulas are identical to those designed for insertion of the primary cannula; however, simple cannulas without the so-called safety mechanisms and insufﬂation ports are generally sufficient (Figs. 23.7D and 23.8D). Some investigators are evaluating the value of systems that allow the insertion of multiple cannulas through a single port, an approach that has the potential to improve surgical cosmesis by reducing the number of incisions created (90–92).
Proper positioning of these ancillary cannulas depends on a sound knowledge of the abdominal wall vascular anatomy. For the secondary puncture, the patient may be tipped head down (Trendelenburg), allowing the abdominal contents to shift from beneath the incision sites, and thus making it unnecessary to lift the abdominal wall during secondary cannula insertion. Alternatively, the intraperitoneal pressure may be maintained at 25 to 30 mm Hg to allow insertion of the secondary cannulas prior to placing the patient in the Trendelenburg position.
Ancillary cannulas should always be inserted under direct vision because injury to bowel or major vessels can occur. Before insertion, the bladder should be drained with a urethral catheter. The insertion sites depend on the procedure, the disease, the patient’s body habitus, and the surgeon’s preference. For diagnostic laparoscopy, the most useful and cosmetically acceptable site for insertion of an ancillary cannula is in the midline of the lower abdomen, about 2 to 4 cm above the symphysis. The ancillary cannula should not be inserted too close to the symphysis because it limits the mobility of the ancillary instruments and access to the cul-de-sac. Laparoscopic cannulas can become dislodged and slip out of the incision during a procedure. There are a variety of cannula designs designed to reduce slippage, which include those with threaded exteriors and anchoring systems with balloon tips.
Lateral placement of lower-quadrant cannulas is useful for operative laparoscopy, but the superficial and inferior epigastric vessels must be located to avoid injury (Fig. 23.3). Transillumination of the abdominal wall from within permits the identification of the superficial inferior epigastric vessels in most thin women. The deep inferior epigastric vessels cannot be identified by this mechanism because of their location deep to the rectus sheath. The most consistent landmarks are the medial umbilical ligaments (obliterated umbilical arteries) and the exit point of the round ligament into the inguinal canal. At the pubic crest, the deep inferior epigastric vessels can often be visualized between the medially located umbilical ligament and the laterally positioned exit point of the round ligament. The cannula should be inserted medial or lateral to the vessels if they are visualized. If the vessels cannot be seen and it is necessary to position the cannula laterally, the device should be placed 3 to 4 cm lateral to the medial umbilical ligament or lateral to the lateral margin of the rectus abdominis muscle. If the incision is placed too far laterally, it will endanger the deep circumﬂex epigastric artery. The risk of injury can be minimized by placing a 22-gauge spinal needle through the skin at the desired location, in order to directly observe the entry through the laparoscope. This provides reassurance that a safe location is identified and allows visualization of the peritoneal needle hole, which provides a precise target for inserting the cannula.
Even after a properly positioned incision, the abdominal wall vessels can be injured if a trocar slides medially during placement. Large-diameter devices are more likely to cause injury; therefore, the smallest cannulas necessary to perform the procedure should be used. Ancillary cannulas should not be placed too close together because this results in hindrance of the hand instruments, which compromises access and maneuverability.