Файл: NMS Surgery_booksmedicos.org.pdf

XIII Perianal and Anal Canal Neoplasms

A

Anal margin (below the dentate line) neoplasms include the following (Table 13-5):

1.Squamous cell carcinoma

2.Basal cell carcinoma

3.Bowen's disease

4.Perianal Paget's disease

B

Anal canal (above the dentate line) neoplasms include:

1.Epidermoid carcinoma includes squamous cell, basaloid, cloacogenic, and mucoepidermoid carcinoma.

a.Clinical presentation may be bleeding, pain, or anal mass.

b.Diagnosis and evaluation

1.Physical examination

a.Assess tumor size, depth of invasion, and ulceration.

b.Examine for retrorectal and inguinal lymph nodes.

2.Anoscopy, proctoscopy, and biopsy

3.Endorectal ultrasound

4.CT scan of the pelvis and liver

5.Chest radiograph

c.Treatment

1.Combined modality therapy consists of 5-FU, mitomycin C, and external beam radiation.

2.Abdominal perineal resection is performed for treatment failures.

d.Prognosis

1.The effectiveness of combined modality therapy depends on the size of the primary lesion. Tumors larger than 6 cm seldom respond completely.

P.247

TABLE 13-5 Anal Margin Neoplasms

2.Overall, combined treatment has a response rate of 90% and a 5-year survival rate higher than 80%.

2.Adenocarcinoma is most commonly an extension from cancer in the distal rectum.

a.Cancer arises from anal glands and ducts. It may arise from outside the lumen of the anal canal and may present as an anal fistula that does not respond to fistulotomy.

b.Treatment is, generally, similar to that for rectal cancer, using preoperative radiation therapy followed by abdominal resection.

3.Melanoma

a.Characteristics. The anal canal is the third most common site (after skin and eyes). Not all anal melanomas are darkly pigmented (i.e., some are amelanotic).

b.Symptoms and presentation. Anal mass, pain, and bleeding are the most common symptoms. Regional lymphatic and distant metastases are common at the time of diagnosis.

c.Treatment. Abdominal perineal resection is recommended if no metastases are detected. Abdominal perineal resection is no more effective than wide local excision for local control. The 5-year survival rate is less than 15%.

Chapter 14

Liver, Portal Hypertension, and Biliary Tract

Benjamin Philosophe

David D. Neal

Michael J. Moritz

Bruce E. Jarrell

I Liver

A Anatomy

The liver is the largest, heaviest intra-abdominal organ, weighing about 2% of total body weight.

1.Segmentation. The liver is composed of two lobes (left and right), and each lobe has two segments (Fig. 14-1).

a.These lobes are divided by the interlobar fissure, an invisible line between the gallbladder fossa anteriorly and the inferior vena cava posteriorly.

b.The falciform ligament, the only externally visible boundary, marks the segmental fissure between the median and lateral segments of the left lobe.

c.The right lobe segmental fissure has no external landmarks.

2.Vascular supply (hepatic arterial and portal venous). The segmental anatomy of the liver is determined by the vascular supply and biliary tree.

a.Arterial supply is from the common hepatic artery, a branch of the celiac axis.

1.The hepatic artery carries fully oxygenated blood and comprises 25% of the liver blood flow.

2.The common hepatic artery enters the porta hepatis medially to the common bile duct, gives off the gastroduodenal artery to become the proper hepatic artery, and bifurcates into right and left hepatic arteries.

3.The cystic artery usually arises from the right hepatic artery.

4.In 20% of the population, the left hepatic artery arises from the left gastric artery. In approximately 20%, the right hepatic artery arises as a branch of the superior mesenteric artery.

b.Venous supply and return

1.The portal vein carries partially oxygenated blood as it drains the entire splanchnic circulation (all structures that receive blood from the celiac, superior mesenteric, and inferior mesenteric arteries) and comprises 75% of the liver blood flow.

a.It is formed by the confluence of the superior mesenteric, splenic, inferior mesenteric, and coronary veins (Fig. 14-2).

b.It enters the liver hilum, where it divides to form right and left branches, which supply the right and left hepatic lobes.

c.It lies posteriorly in the porta hepatis.

2.Blood leaves the liver via the hepatic veins.

a.The hepatic veins course between segments (rather than into segments like the segmental vascular supply). For example, the middle hepatic vein lies between the right and left hepatic lobes and is exposed when opening the interlobar fissure (Fig. 14-3).

b.The hepatic veins drain directly into the inferior vena cava just inferior to the diaphragm.

3.The biliary tree follows the segmental divisions of the hepatic artery and portal vein intrahepatically. The bile ducts lie anterolaterally in the porta hepatis.

P.249

FIGURE 14-1 Surgical anatomy of the liver: left and right lobes.

4.Hepatic resections are based on the segmental anatomy. The surgeon divides the vascular-biliary supply to the portion to be removed and preserves the vascular-biliary structures to the portion to be retained.

a.Right hepatic lobectomy transects the liver through the interlobar fissure between the gallbladder fossa and the inferior vena cava (Fig. 14-3).

b.Left hepatic lobectomy uses the same guidelines.

c.Trisegmentectomy removes the entire right lobe and the median segment of the left lobe across the anatomic division of the falciform ligament (leaving only the left lateral segment).

d.Left lateral segmentectomy removes the segment of liver to the left of the falciform ligament.

e.Wedge resections are performed for small lesions near the liver surface that do not require a full lobectomy. These resections do not adhere to anatomic boundaries but are safe because a limited amount of tissue is transected.

FIGURE 14-2 Portal circulation.

P.250

FIGURE 14-3 Plane of resection for right and left hepatic lobectomy.

B Studies of the liver

1.Liver function tests are blood tests of a few of the myriad functions that the liver performs. a. Synthetic function of hepatocytes is reflected by:

1.Serum proteins, such as albumin or fibrinogen

2.Clotting factors, as measured by coagulation tests (see Chapter 1, III)

3.Cholesterol

4.Blood glucose

b.Clearance function of hepatocytes is estimated by:

1.Ammonia

2.Indirect bilirubin, which is taken up from the blood by hepatocytes

c.Excretory function of hepatocytes and patency of the biliary tree is reflected by:

1.Direct bilirubin

2.Enzyme levels, such as alkaline phosphatase and gamma glutamyl transferase

d.Extent of injury to the hepatocytes is reflected by the serum levels of the enzymes, aspartate transaminase, also called glutamic-oxaloacetic transaminase, and alanine transaminase, also called glutamic-pyruvic transaminase.

2.Imaging of the liver is used to define parenchymal lesions and plan liver resections when appropriate.

a.The sulfur-colloid liver-spleen scan, which visualizes the reticuloendothelial system, is rarely used because more accurate studies are now available. However, it still remains useful in delineating an adenoma from focal nodular hyperplasia.

b.Ultrasound is excellent for detecting the texture of the parenchyma and any lesions within the parenchyma. It is especially useful in assessing hepatic vascular flow and characterizing cystic lesions.

c.Computed tomography (CT) and magnetic resonance imaging (MRI) visualize the parenchyma and adjacent tissues with great clarity. The availability of higher resolution technology and three-dimensional (3D) reconstruction with the use of intravenous contrast have made CT and MRI the procedures of choice to distinguish parenchymal or biliary pathology.

d.Arteriography is used to determine the arterial supply and can detect large parenchymal lesions.

e.Angioportography combines CT scanning with contrast infusion through a catheter placed in the superior mesenteric artery. It is especially useful in assessing the portal vein.

P.251

f.Hepatobiliary scanning is a nuclear medicine scan used to visualize the liver and biliary tree (see III B 4).

3.Needle biopsy (either percutaneous or at surgery) provides liver tissue for histologic study.

C Benign tumors of the liver

In women, oral contraceptive use has increased the incidence of benign primary liver tumors.

1.Hemangioma, the most common benign hepatic tumor, is usually asymptomatic. Usually, it is discovered as an incidental finding (i.e., calcification on abdominal radiograph or a characteristic mass on ultrasound) and is managed by observation.

a.Clinical presentation. Hemangiomas can produce symptoms by compressing adjacent structures or by stretching the liver capsule.

b.Pathology. Grossly, there may be single or multiple masses, and microscopically, there are vascular lacunae lined with normal endothelial cells.

c.Treatment. Only symptomatic hemangiomas should be resected.

2.Hepatocellular adenoma is an uncommon benign tumor usually seen in women that is strongly associated with oral contraceptive use. It is also found in men and women who take anabolic (androgenic) steroids.