Methods of entering and closing the abdominal cavity during laparoscopic bariatric surgery

**Entering the abdominal cavity**

Crystal T. Schlösser, Sayeed Ikramuddin

The inherent advantage of all minimally invasive surgeries is access to body cavities safely, effectively, and cost-effectively. However, access to the abdominal cavity in obese patients is more challenging in bariatric surgery due to patient size, current equipment limitations, and the presence of comorbidities. The ideal goal of abdominal access is to achieve adequate exposure, facilitate instrument insertion and specimen retrieval, and minimize complications.

**background**

The application of pelvic endoscopy first introduced specific limitations regarding access to the peritoneum, peritoneal physiology, and three-dimensional surgery under two-dimensional imaging. Early laparoscopic methods borrowed instruments from urology, obstetrics and gynecology, and thoracic surgery, and employed early pneumoperitoneum needles designed in the 1930s for establishing diagnostic pneumoperitoneum. However, complications from these methods led to the adoption of a traditional small incision approach under direct vision to enter the abdominal cavity, with a large-bore cannula inserted for laparoscopic procedures. Subsequently, both techniques have been developed, resulting in new abdominal access devices that reduce the axial force required to enter the abdominal cavity (spiral devices).

An ideal device for establishing pneumoperitoneum should be simple, quick, and rapidly establish pneumoperitoneum with few (or even no) complications. Ideally, it should be reusable to reduce costs. Currently, there is no ideal device that meets all these requirements, but this is the goal for future research and development.

**Methods of entering the abdominal cavity**

Regardless of the device chosen for access to the abdominal cavity, adhering to basic surgical principles maximizes efficiency and minimizes complications. Careful patient preparation, including positioning the patient in a supine position without tilting, rotation, or head-down positioning, is crucial. Incorrect patient positioning can lead to misinterpretation of the patient's anatomical structure, causing confusion regarding the course of major blood vessels and changes in organ position, resulting in delayed identification and potential unforeseen injuries. During physical examination, attention should be paid to scarring and piercings around the umbilicus or other body parts, as these may be related to intra-abdominal adhesions.

A key consideration in abdominal surgery planning is determining how to maximize the intra-abdominal operating space. Options include standard carbon dioxide pneumoperitoneum, but this can lead to dryness and coldness of the viscera and parietal peritoneum. This is associated with pain (especially diaphragmatic pain), hypothermia, and peritoneal mesothelial cell morphological changes of uncertain significance. Alternative media such as helium and water expansion have been reported. Pneumoperitoneum-free techniques such as abdominal wall traction have also been reported, but none of these are currently suitable for obese surgical patients.

The steps to achieve pneumoperitoneum are: no insufflation, insufflation before insufflation, and insufflation only after an open approach has been established. Intra-abdominal pressure management must be patient-centered; sufficient pressure to achieve good exposure is necessary for surgical safety, but intra-abdominal pressure should also be low enough to avoid ventilation limitations, hypercapnia, and impaired venous return.

**Closed access method to the abdominal cavity**

The pneumoperitoneum needle is a 2mm blunt-tipped needle designed to induce pneumothorax without damaging the lungs. It has a spring-loaded tension sensor with a blunt tip that retracts upon encountering resistance in the fascia and peritoneum, then rapidly ejects after passing through these layers, thus penetrating the tissue while protecting internal organs from damage. Once inside the abdominal cavity, the needle is inflated. This method of abdominal insertion has been used for nearly 40 years in many countries, particularly in gynecology. Longer pneumoperitoneum needles can be used for patients with thick abdominal walls (such as obese patients).

The commonly used puncture site is the umbilicus. The abdominal wall is manually pulled to create negative pressure within the abdominal cavity. The pneumoperitoneum needle is kept in place to maintain pressure consistent with the cavity, thus allowing the abdominal wall to be moved away from the internal organs once the peritoneum is punctured. However, some structures fixed to the abdominal wall or retroperitoneum may be damaged because they cannot be moved. Additionally, rapid entry into the abdominal cavity or failure of the blunt tip of the pneumoperitoneum needle to retract in time can also cause tissue damage. If the needle has already entered the abdominal cavity but the operator is unaware, continuing to insert it can also lead to potential organ damage.

In obese patients, the navel may be difficult to expose, and this area often harbors excessive bacteria and fungi, limiting the extent to which the abdominal wall can be pulled up. Therefore, it is recommended to perform puncture at Palmer's point (below the left costal margin, between the midclavicular line and the anterior axillary line), where the main organ is the greater omentum. Puncture is facilitated by traction on the ribs and costal cartilages above the rectus abdominis muscle, the costal sheath, and the underlying peritoneum. The superior epigastric artery at this location is usually located centrally and is less prone to injury than at other sites. However, extreme care must be taken when applying force to avoid misaligning the needle tip towards the center. At the navel, the needle should be inserted directly towards the pelvic cavity at a 45° angle (avoiding the aortic bifurcation and iliac vessels). Skin sutures can be placed at the navel to provide traction. At Palmer's point, the pneumoperitoneum needle should be inserted perpendicularly to the skin.

The pneumoperitoneum needle should be aspirated to confirm that no blood, body fluid, or feces have been drawn out. Due to gravity or the negative pressure within the abdominal cavity caused by the elevation of the abdominal wall, a drop of normal saline should be instilled at the needle tip and aspirated into the abdominal cavity. The initial carbon dioxide pneumoperitoneum pressure should be 5–8 mmHg. If the pressure is higher (>20 mmHg), it indicates that gas has been injected extraperitoneally or subcutaneously. However, there is no way to definitively confirm that the pneumoperitoneum needle is within the abdominal cavity, and even if the pneumoperitoneum needle position is correctly tested according to the above method, vascular and visceral injury can still occur. Laparoscopic puncture with a needle is considered a safer method, but this method can only detect puncture injury earlier and cannot completely prevent it.

Schwartz et al. reported that for obese patients, the puncture needle can be swirled to avoid the greater omentum. Swirling the needle increases the airflow to 1–2 L/min, creating an elliptical path with the needle tip through short, frequent, and rapid circular motions. This method was reported to have been used in 600 consecutive morbidly obese patients without death or vascular injury; one case of transverse colonic seromuscular layer injury was repaired laparoscopically without sequelae.

Once the pressure reaches 15 mmHg, the trocar cannula can be inserted through the first puncture port. The surgeon should operate in a comfortable position to avoid excessive displacement of the trocar cannula. Methods to reduce complications include raising the operating table to waist height, using a shorter trocar cannula, and having the surgeon support the cannula with their other hand to prevent excessive insertion.

The placement of a trocar directly at the umbilicus without pneumoperitoneum is similar to the method described above for placing a pneumoperitoneum needle. Precise positioning and a puncture trajectory downwards from the midline are emphasized. Most studies, including large meta-analyses, report a complication rate similar to that using a pneumoperitoneum needle (0.3%). An alternative is a long, conical trocar with fascial dilatation properties, which can lift the rectus abdominis sheath during puncture to create negative intra-abdominal pressure (45 cadaveric studies). This is similar to another spiral device recently described for use in obese patients.

Another type of direct-viewing instrument system allows real-time visualization of the first puncture sheath's channel, regardless of whether pneumoperitoneum is present. One instrument (Visiport, US Surgical, Norwalk, CT, USA) uses a sharp cannula to puncture each layer; the other instrument (Endopath Xcel, Ethicon Endo-Surgery, Cincinnati, OH, USA) uses a transparent, cone-shaped, blunt cannula. Because both cannulas are transparent, the condition of each layer of abdominal wall tissue can be visualized during puncture. Theoretically, this instrument helps avoid injury. Early clinical observations also suggested it could reduce the incidence of complications. However, a retrospective analysis of a nationwide clinical database revealed that this instrument caused a higher complication rate. From 1994 to 2000, there were 79 cases of serious complications, 37 cases of major vascular injury, and 4 deaths. Meta-analysis revealed a trend that in routine surgery, the use of instruments for abdominal paracentesis (including the use of pneumoperitoneum needles) to enter the abdominal cavity results in more complications compared to open access to the abdominal cavity.

**Open access to the abdominal cavity**

Hasson et al. reported complications that can occur with pneumoperitoneum needles, and therefore suggested an "open" approach with a 1-1.5 cm incision at the umbilicus to expose the fascia and peritoneum under direct vision. A blunt obturator cannula is inserted directly into the abdominal cavity, followed by suturing the fascia to close the incision and fixing the cannula. Its advantages are a significantly reduced (but not eliminated) risk of aortic injury and faster establishment of pneumoperitoneum and access to the abdominal cavity; its disadvantages are the extreme difficulty in exposing obese patients, higher operative complexity, and a slightly higher risk of intestinal injury. Furthermore, maintaining a leak-free gas supply around the cannula is a challenge in severely morbidly obese patients. This study may have case selection bias, as this method is more often used for repeat surgeries and when other techniques are also expected to fail to achieve successful access to the abdominal cavity. The operative time for this method is comparable to that using pneumoperitoneum needles.

Another modified Hasson technique involves making a small, open incision through the umbilicus using a 5mm blunt trocar under direct vision. This technique does not involve sutures to fix the fascia and is recommended for patients without other abdominal complications or complexities; its applicability is limited in patients with morbid obesity. Senapati et al. described a semi-open modified Hasson technique by opening the linea alba and entering the peritoneum through a blunt conical trocar. Only one case of minor liver injury was reported among 241 patients treated with this method. Balloon-shaped blunt trocars are widely used in inguinal hernia repair and are beginning to be used in abdominal surgery, but funding factors may limit their widespread application.