Mobilization of the Hepatic Flexure

Fig. 8.1

Intraoperative view of the hepatic flexure

Ligamentous Anatomy

The hepatic flexure is surrounded by supporting ligaments and tissues. Laterally, its peritoneal lining joins the right abdominal wall, creating the white line of Toldt that extends alongside the right colon. Its mesentery is continuous with the transverse mesocolon, which becomes the floor of the lesser sac. The hepatoduodenal ligament may extend laterally to become the hepatocolic ligament, a suspensory ligament of the hepatic flexure. The omentum on the right is often adherent to the retroperitoneum and can be challenging to dissect free laparoscopically.

Rarely, the hepatic flexure and transverse colon can be interposed between the liver and diaphragm creating an asymptomatic Chilaiditi’s sign, the appearance of pneumoperitoneum, usually found incidentally on plain radiographs. First described in 1910, this occurs in only 0.028–0.25% of the general population [1–4]. Chilaiditi’s interposition occurs due to laxity or absence of the suspensory ligaments of the transverse colon. This may also be associated with a concurrent laxity of the falciform ligament. Chilaiditi’s syndrome occurs more commonly with a redundant or dilated colon (i.e., chronic constipation, aerophagia), liver atrophy, paresis of the hemidiaphragm, or increased intra-abdominal domain (i.e., ascites, multiple pregnancies, obesity) [5, 6]. It is also found in increased rate in those with a mental disability or schizophrenia [7]. While usually asymptomatic, Chilaiditi’s interposition may make mobilization of the hepatic flexure more difficult, such as with a high splenic flexure.

Vascular Anatomy

Understanding the vascular anatomy and variations is important for safe dissection of the hepatic flexure, especially when performing an oncologic resection where high ligation of the supplying arteries is necessary. Vascular anatomy of the right and transverse colon is traditionally divided into branches of the superior mesenteric artery (SMA): ileocolic , right colic, and middle colic arteries. The primary vascular supply to the hepatic flexure is via the right colic artery and the right branch of the middle colic artery; however these are both highly variable in location and course. A true right colic artery branching from the SMA occurs only 10.7–38% of the time [8–11]. Most commonly, the dominant right colic vessel arises as a branch of the ileocolic artery and next most commonly as a branch of the middle colic artery.

The middle colic artery is more constant, occurring in >95% of individuals [8]. However, its division into right and left branches is highly variable and ranges from 3 mm to 70 mm from the origin of the middle colic at the SMA [8]. In up to 40% of individuals, it does not branch at all and arises as a branch of the inferior mesenteric artery or a dorsal pancreatic artery [12].

Technical Considerations

Port Placement

In general, we recommend periumbilical midline placement of the single-incision port for operations involving the hepatic flexure. This provides the most amenable angles for mobilization. If a stoma is being created as a part of the operation, we will typically use this as our access site. Right lower quadrant placement of the port, commonly used when an ileostomy will be created, yields the most difficult dissection angles. However, the operation can still be successfully performed safely from this location. A left-sided abdominal port may also be used, such as with a colostomy reversal, in which the hepatic flexure must be mobilized for a tension-free anastomosis or if a completion colectomy is being performed.

Skin incisions can be kept very small and are limited only by specimen size or space needed to perform an extracorporeal anastomosis. Dissection may be performed through fascial incisions of approximately 2–3 cm which easily allows introduction of a small single-incision port and instruments. Incisions that are too large may cause difficulty in seating of the port, leaking of insufflation, and are typically unnecessary when larger than the specimen. If the incision is found to be too small, the fascial defect can be enlarged while keeping the skin incision small as it will usually stretch much more than the fascia.

Optimize External Working Space

Several techniques can be employed to optimize external working space and minimize instrument collisions. The use of a 90 ° light cord adapter, differing length instruments (i.e., bariatric instruments), and instruments with reticulating handles will allow the surgeons hands to be offset from each other and from the camera operator. It is also important to understand that the angles required to optimize exposure of the hepatic flexure from a single entry site will differ significantly from the traditional laparoscopic approach and may be counterintuitive in some instances. Internal crossing of instruments is essential at times and should be embraced, to provide external freedom of movement for the operator, especially when significant retraction is required. However, both the surgeon and assistant should understand that there will inevitably be collisions that will require some problem solving to overcome.

Optimize Internal Working Space

Internal working space can be limited by the inline nature of instruments and camera or due to patient factors. The use of both an angled laparoscope (either fixed 30° or flexible tip) and internal crossing of instruments helps to overcome the limitations of the single-incision technique. Dissections which are difficult due to close proximity of the target anatomy to the incision, either due to limited abdominal domain or port location, as is often encountered when opening the lesser sac from a midline site, can be overcome by upward traction on the port. This creates several centimeters of additional working space by lifting away the abdominal wall.

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