The falciform ligament and the origin of the round ligament of liver on the phrenic aspect and the sagittal fissure on the visceral aspect macroscopically divide the liver into a larger right lobe and a smaller left lobe. However, this does not correspond with the functional anatomy of the liver (1). The functional structure of the liver rests on the portal vein ramifying into individual, completely independent subunits, the liver segments. Couinaud structures the liver into eight segments. They are numbered in clockwise direction and start with the caudate lobe as segment I (2).
In general, the liver accounts for 20% to 30% of the cardiac output. Blood is transported into the three-dimensional vasculature of the liver via arterial (10% – 20% of the blood supply) and portal venous vessels (80% – 90% of the blood supply). The blood drains from the liver through the hepatic veins (1). Other structures leaving the liver include the bile ducts (3).
In 1992 Ganger at al. were the first to describe laparoscopic liver resection (4) in 16 patients with isolated benign or malignant tumors of the liver, e.g., symptomatic hemangioma, focal nodular hyperplasia, as well as hepatocellular adenoma, colorectal hepatic metastases and hepatocellular carcinoma. To date, far more than 3,000 laparoscopic liver resections have been published (5).
In the beginning, mostly peripheral resections and so-called wedge or atypical liver resections were performed. The continued development of surgical techniques and instruments now allows larger laparoscopic resections, such as right/left hemihepatectomy and extended hemihepatectomy (6). In 2009 Yoon et al. were the first to demonstrate the feasibility of laparoscopic central liver resections (7).
In recent years, the ongoing refinement of surgical instruments coupled with the continued development of surgical techniques has made laparoscopic liver surgery ever safer. Bleeding can be controlled more effectively and quickly (8). Thus, at present only about 20% of patients undergoing extensive laparoscopic liver resection will require blood transfusions during or after the procedure (9). By now, the techniques of open liver surgery may also be employed in laparoscopic procedures. This includes diagnostic intraoperative modalities such as ultrasonography for exact positioning and resection planning of deep-seated or invisible lesions (10), as well as hand resection techniques such as laparoscopic liver resection with the water jet or Ultracision (3).
Due to the deep-seated location of segment I (caudate lobe) and its immediate vicinity to the inferior vena cava, its laparoscopic resection is challenging (11). Today, laparoscopic resection of segments II and III is regarded routine (12). Since the anatomical situation of these segments is rather clear, this facilitates their resection (9). Differentiation is needed in laparoscopic resection of segment IV the anterior location of segment IVb does not present any problems in resection, while the posterior deep-seated segment IVa poses significant challenges in minimally invasive surgery (13). Due to their anterior location segments V and VI are rather easy to resect laparoscopically (14-16). Laparoscopic resection of segments VII and VIII, however, is quite challenging. Minimally invasive procedure on these segments is as demanding as right hemihepatectomy. For deep-seated tumors in segment VII resection of the right posterior part is preferred over hemihepatectomy. In contrast, the literature recommends right hemihepatectomy for tumors in segment VIII (12, 17).
The most common reasons for converting from laparoscopic to open surgery are uncontrollable bleeding (13) and technical problems (13). At present the literature lists the conversion rate at 3.4% (13).
Benefits of laparoscopic liver resection:
- Reduced access trauma (18)
- Significant reduction in intraoperative blood loss with identical duration of surgery and identical need for a blood transfusion (19, 20).
- Lower morbidity (19, 21) – currently 5% to 15% (8, 13)
- Significant reduction in duration and intensity of postoperative pain (5, 22. 23)
- Improved early ambulation together with better pulmonary and intestinal function (24-26)
- Minimized intra-abdominal surgical adhesions (14, 16)
- Significantly reduced immunosuppression (27-29)
- Shorter hospital stays (16, 22, 30)
- Faster convalescence and earlier return to work (13)
- Less risk of postoperative hernia (21, 31)
Drawbacks of laparoscopic liver resection:
- Rather new surgical technique (17, 32)
- Sparse data on efficiency, especially regarding extended operations (17, 32)
- Technically rather demanding for surgeon and equipment (33)
- Higher costs (18, 34, 35)
- Longer learning curve and significantly longer operating time, particularly in the beginning (13)
- Reserved for experienced centers – this type of surgery is not for everyone (9, 33)
Conclusion
At present, the standard approach in extensive oncological liver resection is open surgery (36). However, the development of appropriate instruments for efficient and safe liver surgery has resulted in decisive advances in laparoscopic hepatic procedures (37). Current literature notes a low rate of postoperative complications both in laparoscopic as well as open liver resections (36, 38-40). Appropriately selected cases (benign hepatic lesion, small peripheral cancer) should primarily undergo laparoscopic liver resection because it will result in a shorter hospital stay and lower rate of minor complications, with identical rate of major complications (36, 38, 39, 41). A critique of these results must note that extended liver resections are often still performed in open technique today, and for these procedures a higher morbidity and longer hospital stay should be expected. No large prospective randomized trials comparing the oncological significance of laparoscopic and open surgery in extended liver resections have been published to date. These trials should also compare mortality, morbidity and hospitalization. Smaller trials were able to demonstrate the safety of laparoscopic hemihepatectomy (36, 39, 42). At present, extended laparoscopic and laparoscopically assisted liver resections still are very much under discussion (38, 39, 42). Laparoscopic liver resection, especially in extensive central findings, still demonstrate drawbacks in the precise three-dimensional orientation of the surgeon, e.g. when dissecting the large vessels. Bleeding complications are the most common reason for converting to open liver resection (39, 42, 43). Other drawbacks of laparoscopic procedures include the often longer duration of surgery, higher costs and the greater dependency on the surgeon performing the procedure (41). Nevertheless, in the future laparoscopic liver resections by experienced surgeons will become the gold standard in liver surgery (38, 39, 42, 43).