Obesity increases the risk of postoperative peripheral neuropathy after minimally invasive colon and rectal surgery and is an independent risk factor despite adequate precautions; however, most neuropathy is temporary and self-limited, and the incidence is minimised with our approach as described above [18]. The overall incidence quoted in our paper is 2 % of all minimally invasive colorectal operations and 3.6 % in robotic operations (all were rectal operations performed in lithotomy). An analysis of our data showed that the side towards which the patient is tilted in the transverse plane suffers neurologic damage more frequently, specifically the left-sided nerve axis during right colectomy and the right-sided nerves during left colon operations. The incidence theoretically should be minimised further by differential padding favouring the side towards which the patient is tilted.

Access to the peritoneal cavity is most rapid and effective in the obese and morbidly obese subjects with the Veress needle. Extra long needles (150 mm) as against the standard 120 mm are occasionally needed in the morbidly obese patient. We insert the Veress through a 2 mm stab incision through or just above the umbilicus after tenting up the tissues with two towel clips. The Palmer’s point represents another site for Veress needle insertion in the morbidly obese as this location has less fat than the periumbilical area in these individuals. Optical trocar systems can also be used; Visiport (Covidien, Norwalk, CT) and Optiview (Ethicon Endo-surgery, Cincinnati, OH) are two FDA-approved commercially available devices which allow safe insertion under vision [19]. In patients who have prior surgeries especially midline incisions, we use the Palmer’s point in the left subcostal region or place the first trocar by the optical method far out in the lateral quadrants. Once entry is established, we use a high-flow thermosufflator (Insuflow, Lexion Medical, St. Paul, MN, USA), which delivers CO₂ gas heated to 95 °F and 95 % relative humidity to rapidly establish pneumoperitoneum to 14–15 mmHg. The use of heated and humidified gas prevents hypothermia and tissue desiccation, which translates into less abdominal and shoulder pain [20]. The optical trocar is then placed either by enlarging the initial stab or in the location of choice through a separate incision. The use of two insufflation ports is recommended by bariatric surgeons in morbidly obese patients to maintain pneumoperitoneum, but we have never needed to use this method in our practice. The open Hasson technique is frequently difficult to perform in the morbidly obese, and it is even more difficult to achieve a tight fascial seal around the trocar and is the least preferred entry method in this group in our practice.

Obesity alters the normal dimensions of the torso and alters spatial orientation of normal landmarks. Specifically, changes of torso length by 10–11 cm and torso girth by 12–13 cm are reported between underweight and obese patients [21]. Contrary to popular belief, the position of the umbilicus relative to the torso is not fixed. In normal-weight individuals, the umbilicus is located roughly halfway between the xiphoid and the pubic symphysis. With increasing BMI, the umbilicus shifts caudad (Fig. 19.2) [22]. Port positions based on the umbilical location may therefore be erroneous. A good rule of thumb is to use a 5 mm trocar to perform the abdominal survey and then place the additional robotic and assistant trocars under vision at the appropriate distance from the target anatomy rather than through defined premarked sites. When placing lateral ports for right and left colectomy, the ports should be placed at a defined distance usually 10–12 cm lateral to the optical trocar and not far lateral based on patient girth, so as to allow access to the colon on the opposite side. This is because the size of the actual muscular torso does not change much in most obese individuals, and placing the ports too far lateral leads to a tangential entry into the abdomen rather than the perpendicular entry which is desirable (Fig. 19.3a–c).

In low anterior resections, the entire trocar setup moves down closer to the pelvis to allow access to the low pelvis and the pelvic floor (Fig. 19.4a, b).

Length of the pelvis is also an important consideration and should be assessed in every patient by review of the CT scans. Tall obese males particularly may have a very long pelvis and we have encountered difficulties in reaching the pelvic floor with the robotic instruments with trocars in standard locations. In situations where the instruments don’t reach the lower extremes of the pelvis, the robot is undocked, a fresh set of ports is placed closer to the target anatomy, redocking is performed and the procedure is continued. As experience grows, the trocars should be placed lower in the abdomen, thereby moving closer to the target anatomy.

Docking the robot presents some unique challenges in the morbidly obese patient. A steep Trendelenburg position is often used in all colon and rectal operations (except during flexure mobilisation) to use gravity-aided exposure. The increase in abdominal wall fat leads to a massive increase in anteroposterior girth, and the robotic arms may not have sufficient space to clear the wall despite the table being dropped down to the lowest position (Fig. 19.5). A compromise with a slight decrease in head-down tilt with the assistant actively retracting the small bowel out of the field is often needed to physically allow the robot to reach the field. The use of bariatric tables is useful because they allow a much steeper Trendelenburg tilt than with normal tables and their lowest height setting is as low as 25 in. as against the 32 in. standard.

Gravity is the most important aid in exposure in robotic colorectal surgery especially in the obese. The use of steep Trendelenburg and right-down tilt (low anterior resection and left colectomy) or left-down tilt (right colectomy) is indispensable. To allow the small bowel to fall away from the operative area, release of all adhesions is mandatory. The ligament of Treitz is always released for left-sided resections, to allow the small bowel to be packed into the right paracolic and supracolic compartments. Release of the omentum is often needed to allow space for the bowel to be thus placed. The use of radiopaque gauze as a sling over the small bowel to which it adheres is also a useful technique to keep the bowel in place. The fat-laden mesentery is prone to tearing, and it is often prudent to handle the bowel directly or with sweeping motions to deliver it out of the pelvis into the upper abdomen. The use of endoscopic paddles is recommended by some surgeons to retract the small bowel, but we have never found it necessary to do so.

Obese patients have an increased incidence of wound infections and fascial dehiscence leading to hernias. Careful consideration should be given to specimen extraction site and site for anastomosis when performed extracorporeally. The specimen tends to be bulky due to fat-laden mesocolon, giant epiploica and abundant fatty omentum in right colon specimens.