Where is segment 7 of the liver

The division of the liver into self-contained units allows the surgical resection of individual segments and sections without damaging those segments remaining. Hence for the liver to remain viable, resections occur along the hepatic veins and portal veins in the planes that define the boundaries of these segments. Additionally, if resection is performed of a hemiliver plus an additional adjacent section, then further nomenclature is used 7 :.

This anatomic division was first described by the French Surgeon Claude Couinaud in The notion of the Couinaud liver segments being based on the arrondissements administrative districts of Paris is a radiological urban myth 4 , but sounds cool nonetheless and is a nice way to remember the numbering. In the Terminology Committee of the International Hepato-Pancreato-Biliary Association published a consensus hepatic nomenclature which has become rapidly adopted around the world 7,8.

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Case Description. The patient is a 82 year old man, with a longstanding history of hepatitis B. Another important point is the complete liberation of the hepatorenal, falciform, triangular, and right coronary ligaments in order to fully mobilize the liver and convert a segment that is posterior in the anatomical position to an anterior segment for the surgeon.

And finally, the use of intercostal trocars that allows a direct and perpendicular view of the right hepatic vein and vena cava represents the most important point. Interestingly, these specific trocars should be inserted through the pleural cavity, during a forced expiration or apnea to avoid lung injury. In this context, the trocar balloon helps the surgeon to avoid displacement or that pneumoperitoneum enters the pleural cavity. At the end of the procedure, we strongly recommend to stitch laparoscopically these diaphragmatic openings after removing the trocars in order to avoid migration of abdominal fluid or bowel incarceration into the pleural cavity during the postoperative period and also to avoid future diaphragmatic hernia.

We use this device because it saves time by sealing vessels up to 7 mm in diameter avoiding the need to use clips in the majority of intrahepatic veins and portal branches. This should not be coinfused with the trisectionectomy of the right or left side were we resect three sections and not segments.

Segments, each with a different color. An addition was added also if the word sector were to be used instead of section. So the term section or sector has to be used very cautiously on the left side to describe exactly what you mean. Segement 4, is divided into 4A and 4B. This was made because of multiple indications were segment 4A is rsected without the resection of segment 4B like in cases of gallbladder cancer. Also the resection of segment 4A is counted as the most difficult liver resection as it lies between the middle and the left hepatic vein.

This terminology has gained wide acceptance and has removed most of the confusion that use to exist in the past. The extra hepatic portal triad is consisted of the portal vein, the hepatic artery and the common hepatic duct. These structures are enclosed in a connective tissue and peritoneum up to the hepatic hilum.

The term Glissonian sheath is reserved for the part that extendeds into the intrahepatic portion of the liver beyond the hilum. This sheath surrounds the portal triad structure before they enter into each section, giving rise to the resection of each segment liver unit separately without affecting the other segments [ 22 ].

This gives rise to the aberrance of the central segments 4, 5 and 8 ramifications like a bush and fan shaped. Consequently, a single segment resection will require several Glissonian sheath at various depth and is much more difficult.

Were the priphral segments 6, 7, 2 and 3 have long branches that travels a distance reaching to these segments giving the appearance of tree like making their resection less complicated and usually requiring a single Glissonian sheath ligation [ 23 ]. On the right side the portal vein is similar to the arteriobiliary segmentation. On the left side they differ from each other. The left portal vein consists of a transverse and an umbilical portion. The transverse portion only sends small branches to segment 4 and one or two branches to segment 1.

All the larger branches arise beyond the attachment of the ligamentum venosum umbilical portion of the left portal vein. This part of the vein gives right branches to segment 4 and on the left side it gives one branch to segment 2 and more than one to segment 3. The portal vein terminates where it joins the ligamentum teres at the edge of the liver. This unique structure explains the duael function of the left portal vein during in-utero and then in-adult life.

Portal vein with its divisions. On the right side the portal vein is usually very short and gives rise to the right anterior and right posterior branches. Each of these branches gives rise to two main segmental divisions. The right anterior gives both segment 5 and 8, where the right posterior gives segment 6 and 7. Usually there are very little variations in the portal vein. The commonest one is where the right anterior branch joins the left portal vein.

This is very important to recognise especially when doing a left hepatectomy causes injury could happen to the right anterior section leading to the loss of segments 5 and 8. Another common anomaly is the absence of the main right portal vein giving rise to a trifurcation at the hilum of the portal vein to the left main, right anterior and the right posterior branches. This is important when doing a right hepatectomy to transect each branch separately not to injure the left portal vein [ 24 - 25 ].

For the clinical description of this part we will try to simulate what happens in clinical practice by dividing it to pre-operative radiology and intra-operative by intra-operative ultrasound.

To try and make this part as simple as possible for the reader we will try to identify land marks that you should look for in the ultrasound, CT or MRI. The ultrasound is the usual screening tool used to see the whole liver and identify cystic from solid lesions. Then most centres will request a Triphasic CT scan of the liver in the hope to identify the nature of the lesion and the location.

A physician should not comment on any lesion seen until full examination of all three phases arterial, venous and delayed are examined and the lesion is seen on all three phases to give the best chance of reaching the right diagnosis. As we described the anatomy of the liver by the first order division and its landmark the middle hepatic vein, it is the same here.

The middle hepatic vein can be seen on any of the above mentioned x-ray investigation. This will lead to the division of the liver to the right and left liver and identifying the lesion in which liver it lies. The next step is to identify the falciform ligament and the right hepatic vein.

This will divide the left liver to the medial and lateral sections and the right liver to the anterior and posterior sections alternatively. By this any lesion will be clearly seen in each section of the hemi-liver. The last step is to identify the main portal vein and follow it till you reach to the bifurcation of the right and left branches which corresponds to the line that divides the liver into the upper and lower segments.

This will give rise to the division of each section to its corresponded segments as described before in the anatomy part Figure. Main portal vein MPV , with a lesion seen in the right posterior lower segment segment6. If this simple technique is adopted a full idea of the lesions identity and location could be achieved with a high degree of certainty making the surgical planning much more feasible. All segments identified on CT pre-opretive. This is usually carried out by the intra-operative ultrasound [ 26 - 30 ], which we believe no liver resection should be done without mastering its use especially in malignant liver lesions.

There are six simple steps that should be followed to get the best results of the ultrasound. To identify the segments the same method that was done pre-operative on CT is adopted by the localisation of the middle hepatic vein and drawing a line on it to get the right and left livers.

Intra operative ultrasound middle hepatic vein. A longitudinal B sagetal. The falciform ligament which divides the left liver to the medial and lateral sections can be seen on the surface. The left hepatic vein that divides segment 2 and 3 can be identified. On the right side the right hepatic vein is seen and a line is made to divide the right liver to the anterior and posterior sections. Intra operative ultrasound right hepatic vein. The portal vein is then identified and followed to get all its branches and a line is made horizontally to get the upper and lower segments of the liver.

After connecting all these lines the liver segments will be seen on the surface with the exception of segment 1 which is separate as we indicated before and can be seen over the IVC as the caudate lobe [ 31 ]. B Left portal vein LPV with its segmental branches. A full pre-operative evaluation is necessary before embarking on a liver resection especially that most of the patients with HCC are also cirrhotic.

There are multiple models to evaluate these patients and the most widely used one is the Child-Pugh score. This model stratifies patients into stage A, B, and C. Therefor most recent staging systems for HCC has included three important factors to evaluate the patient before any liver resection, the tumour, the liver status and the patient factor. Although chronic liver disease is not an absolute contraindication to liver resection, the morbidity and mortality increases prohibitively with increasing hepatic dysfunction.

Childs class C or late B patients are generally excluded from major resections whereas Childs A or early B patients may be candidates [ 8 , 31 ]. As we mentioned above radiological studies are important in determining the presence of portal hypertension, ascitis, tumour localization, feasibility of the resection, tumour extension, distance from the pedicles and segments necessary to be resected as well as extra-hepatic metastasis [ 8 ].

To minimize risk of air embolism from disrupted hepatic veins[ 8 ] and to minimize blood loss from the resected raw liver surface[ 3 ]. Skin incisions for liver surgery. Preparation of the operative field includes the area from the lower abdomen up to and including the chest, extending from axillary line to axillary line [ 8 ]. The majority of liver resections are performed with either a right subcostal incision with upper midline extension inverted hockey stick or a chevron Mercedes incision [ 8 ].

Intra-operative ultrasound is done as described above and the necessary ligaments are released according to the segments of the liver that needs to bee resected. Usually the falciform ligament is released to allow free mobilization of the liver and a better access for the ultrasound. A liver surgeon should be familiar with all the techniques of liver resection because each has advantages and disadvantages making different resections more feasible. This technique is started by dissection of the portal triad and the hilar plate, where the right and left portal veins are identified.

This makes the ligation of each portal branch more feasible. Then the vascular line of demarcation is seen and with the aid of intra-operative ultrasound to identify the rest of the vascular structures and the tumour. The liver is then mobilized according to the part being resected. Parynchymal transaction is then carried out followed by ligation of the hepatic veins. This type is usually applied in patients with less liver fibrosis and a right or left liver resection is needed.

Anterior Approach. A the tape is around the main and right hepatic artery. B The yellow tape is around the left portal vein. The liver is mobilized according to the part being resected. This will give access to the right or left hepatic vein which is usually circled and controlled.

Then two ways can be done, were some surgeons transect the vein followed by Pringle and transect the liver parenchyma by the fast technique in about min.

This is usually fast and has less bleeding and can be done in patients with right, left and both left lateral and right posterior peripheral sections liver resections specially if the patient has liver fibrosis because of the time and bleeding. However, this technique requires the excellent use of ultrasound to avoid injury to the main vascular structures, and prevent a long Pringle time for the unresected part of the liver.

The other way is to start with the liver transaction. This will not require the routine use of Pringle, however it can be associated with more blood lose, and longer transection time to control the bleeding.

This is usually done in non cirrhotic patients specially in living related liver transplant. By using also the posterior approach the portal pedicle will be transacted at the end in the liver.

This will decrease the injury or the narrowing of the unresected pedicle. This approach was adopted recently and was mainly applied in the right liver donors for living related liver transplant. This technique usually relies on the principle of keeping the liver well vascularised till the last minute to keep the liver viable. The approach is done by using the avascular plane on the anterior part of the inferior vena cava and the window between the right and middle hepatic vein.

This makes the passage of a tape from the inferior part of the liver to the superior part over the inferior vena cava.