The liver is macroscopically divided by the falciform ligament and the attachment of the round ligament of the liver on the diaphragmatic surface, as well as the sagittal fissure on the visceral surface, into a larger right lobe and a smaller left lobe. However, this does not correspond to the functional structure of the liver (1). The functional structure is based on the portal branching into individual, independent subunits, the liver segments. According to Couinaud, eight liver segments are distinguished. These are numbered clockwise and begin with the caudate lobe as segment I (2).
The liver accounts for a total of 20 – 30% of the cardiac output. The blood is transported into the liver via arterial (10 – 20% of the blood supply) and portal venous vessels (80 – 90% of the blood supply) in a three-dimensional network. From the liver, the blood is drained via the hepatic veins (1). Other vessels draining from the liver are the bile ducts (3).
Gagner et al. described laparoscopic liver resection for the first time in 1992 (4) in 16 patients with isolated benign and malignant liver tumors, such as symptomatic hemangiomas, focal nodular hyperplasias, hepatocellular adenomas, or also colorectal liver metastases, hepatocellular carcinomas. Since then, far more than 3000 cases of laparoscopic liver resection have been published (5).
Initially, mainly peripheral resections or so-called wedge or atypical liver resections were performed. Through continuous further development of surgical techniques and instruments, larger resections, such as right- and left-sided hemihepatectomies as well as extended hemihepatectomies, can now also be performed using laparoscopic techniques (6). Yoon et al. were able to demonstrate the feasibility of a laparoscopic central liver resection for the first time in 2009 (7).
Through the continuous further development of operative techniques on the one hand and surgical instruments on the other, laparoscopic liver surgery has become steadily safer in recent years. Bleedings can be stopped more effectively and quickly (8). As a result, currently only about 20% of patients require intra- or postoperative blood transfusions in extensive laparoscopic liver resections (9). Techniques from open liver surgery can now also be applied in laparoscopic procedures. On the one hand, diagnostic intraoperative aids such as ultrasound for precise localization and resection planning of deep-seated or non-visible lesions (10) are worth mentioning, on the other hand also resection methods such as laparoscopic liver resection with the help of the water jet or Ultracision (3).
The laparoscopic resection of segment 1 (caudate lobe) is considered demanding due to the direct proximity to the inferior vena cava and the deep location (11). The laparoscopic resection of segments 2 and 3 is now considered a routine procedure (12). In the resection of these segments, a comparatively clear anatomical situation is found, which can be utilized (9). In laparoscopic resection of segment 4, a distinction must be made. Thus, the ventrally located segment 4b is unproblematic, but the dorsal, deep-seated segment 4a is only very problematic to remove minimally invasively (13). Segments 5 and 6 are relatively unproblematic to operate laparoscopically due to their anterior location (14-16). Segments 7 and 8, on the other hand, are only very problematic to resect laparoscopically due to their anatomical location. A laparoscopic resection of these segments is considered as demanding as a right hemihepatectomy. For deep-seated tumors in segment 7, a resection of the right posterior section of the hemihepatectomy is preferred. In contrast, for tumors in segment 8, a right hemihepatectomy is recommended in the literature (12, 17).
The most common reason for conversion to an open surgical approach is primarily uncontrollable bleedings (13) or also technical problems (13). Currently, the conversion rate in the literature is 3.4% (13).
Advantages of laparoscopic liver resection:
- Reduction of access trauma (18)
- significant reduction of intraoperative blood loss with identical operating time and identical blood transfusion requirement (19, 20)
- lower morbidity (19, 21) – currently 5-15% (8, 13)
- significantly reduced postoperative pain intensity and duration (5, 22, 23)
- better early mobilization with consecutively improved lung and bowel function (24-26)
- Minimization of operative abdominal adhesions (14, 16)
- significant reduction of immunosuppression (27-29)
- Shortening of hospitalization (16, 22, 30)
- faster convalescence and earlier ability to work (13)
- lower postoperative hernia risk (21, 31)
Disadvantages of laparoscopic liver resection:
- relatively new surgical method (17, 32)
- poor data on efficiency especially in extensive operations (17, 32)
- high technical requirements for surgeon and equipment (33)
- higher costs (18, 34, 35)
- longer learning curve and especially initially significantly longer operating time (13)
- reserved for centers of competence – not surgery for everyone (9, 33)
Conclusion
Currently, especially in extensive oncological liver resections, the open surgical approach is the method of choice (36). However, the development of suitable instruments for efficient and safe liver surgery has led to a decisive advance in laparoscopic liver surgery (37). In the current literature, low postoperative complication rates are shown for both laparoscopic and open liver resections (36, 38-40). With appropriate selection (benign liver lesions, smaller peripherally located carcinomas), a laparoscopic liver resection should primarily be performed, as it results in shorter hospitalization and lower minor complication rate, with identical major complication rate (36, 38, 39, 41). These results are to be noted critically, as extended liver resections are currently still more frequently performed in open technique and for these interventions both higher morbidity and longer hospitalization are to be expected. The literature lacks larger, prospective, randomized studies on the oncological value of extensive liver resections in laparoscopic and open technique. These studies should also include a comparison regarding mortality, morbidity, and hospitalization. In smaller studies, it has already been shown that hemihepatectomies can also be performed safely laparoscopically (36, 39, 42). Currently, the performance of extensive laparoscopic and laparoscopically assisted liver resections is still critically discussed in the literature (38, 39, 42). In laparoscopic liver resections, disadvantages are shown especially in extensive, central findings in the exact three-dimensional orientation of the operator, for example in preparation at the large vessels. Bleeding complications are the most common reason for conversion to open liver resection (39, 42, 43). Other disadvantages of laparoscopic interventions are the often higher time expenditure, the higher costs, and the greater dependence on the respective operator (41). Nevertheless, laparoscopic liver resections will increasingly become the gold standard in liver surgery by experienced surgeons in the future (38, 39, 42, 43).