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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_605_Библиотеки_им_академика_М_И_Перельмана.pdf
Figure 2.7 (A) The colorectum: Beginning with the cecum, the next part is the
ascending colon on the right side of the body. After a sharp-angled bend (“right
flexure”) the transverse colon follows. The left (splenic) flexure is formed by the junction of the transverse colon and the descending colon. The length of the colon
varies considerably. Of particular notion is the “appendix vermiformis.” (B) Historical
illustration by Vesalius (1543): Note the detailed and realistic representation of the
appendix, etc. including the anal sphincter. The last part of the ileum is ligated
(arrow). From (A) M. Scholle, (B) Courtesy: PD Dr. S. B. Reiser, Klinikum rechts der Isar.
Figure 2.8 The Barium enema of the colorectum gives a good impression of the
anatomy. A contrast medium (Barium) is instillated into the colon via the anus.
The retrograde filling depicts the configuration of the colorectum. The last loop of the
small bowel is also visible (arrow). Courtesy: Dr. A. Fingerle, Klinikum rechts der Isar.
30
Biomedical Engineering in Gastrointestinal Surgery
Figure 2.9 Anatomy of the anorectum: (A) The upper and middle third mainly function as storage space, whereas the lower third consists of the anal sphincter complex. The anal sphincter is a multilayered cylindrical structure, consisting of the
smooth muscle internal sphincter and the external striated muscle layer. The sphincter is elevated by the funnel-shaped levator ani muscle
anorectum. From (A) M. Scholle, (B) Courtesy: Dr. A. Fingerle, Klinikum rechts der Isar.
[12]. (B) MR image of the
2.5.2 Functional Task
The main task of the colorectum is to reduce the mass of the feces and to
enable a controlled defecation. Any remaining absorbable nutrients including water are removed, as well as vitamins produced by colonic bacteria. At
the end, the feces are compacted and stored in the rectum until they can be
discharged via the rectum. The anorectum and the pelvic floor provide
continence and enable controlled evacuation of the indigestible mass.
2.5.3 Disorders and Diseases
Epidemiologically, the appendix most frequently needs surgical intervention. Appendectomy is not a great deal in surgical terms, but it has to
be performed very often and is, thus, of distinct economical importance.
Diverticulitis is an inflammation of small colonic pouches (“diverticles”)
which mainly occur in the sigmoid region. The primary treatment is
conservative (antibiotics). Recurrent diverticulitis needs surgical resection.
Inflammatory bowel disease such as Crohn’s disease or ulcerative colitis
are also the domain of medical treatment but often need surgery as well.
A problem of increasing importance is cancer of the colorectum.
Large parts of the colon can be removed without any significant influence
upon the quality of life of the patient. The closer the lesion comes to the
31Anatomy, Physiology, and Selected Pathologies of the Gastrointestinal Tract
anorectum, the more critical becomes resection since bladder function,
sexual activity, and fecal continence may be concerned.
Last but not least, fecal incontinence is a major issue either after
surgical procedure or noniatrogenic causes.
2.5.4 Biomedical Engineering Aspects
Though significant progress could be achieved in the treatment of
colorectal diseases, much has still been left to BME-based improvements.
For many reasons, it would be very attractive to develop alternative
options for the surgical treatment of appendicitis. First attempts were
made to implant stents into the appendix to relieve inflammation.
Another approach is so-called “scarless surgery” via natural orifices.
Table 2.4 enumerates some innovative BME applications.
2.6 LIVER/GALLBLADDER
2.6.1 Anatomical Description
The liver is the largest glandular organ of the body. It is situated in the
right upper abdomen and extends to the left hypochondrium.
The convex upper surface is molded to both halves of the diaphragm
(
Fig. 2.10).
Accordingly, it rises and falls during respiration. The internal anatomy
differs from that of other organs, since the blood supply comes from two
vessels: the hepatic artery provides arterial blood, and the portal vein carries
blood to the liver which has passed before through the alimentary tract
(including pancreas, spleen, and gallbladder). After circulating through the
liver the blood is returned to the inferior caval vein via the hepatic veins.
The liver produces bile which is collected by the intrahepatic bile
ducts. The main bile duct is formed by the union of these smaller
Table 2.4 Colorectum: selected diseases/disorders and BME aspects
Disease/disorder Treatment BME aspects
Appendicitis Appendectomy Endoscopic stenting
Scarless appendectomy
Cancer Surgical resection Endoscopic resection
Tailored surgery
Improved anastomotic techniques
Notes
Fecal incontinency Surgical sphincter
augmentation
Electrostimulation
32
Biomedical Engineering in Gastrointestinal Surgery
Figure 2.10 Schematic drawing of the liver. (A) Blood inflow to the liver comes from
the hepatic artery and the portal vein; (B) Explanted liver before transplantation; (C)
3D data reconstruction of the liver with color-coded segments. From (A) M. Scholle,
(B, C) MITI.
ducts. The bile flows via the common bile duct into the duodenum.
Immediately prior, the bile duct joins with the pancreatic duct. Bile and
pancreatic juice are mixed and injected into the duodenum.
Based upon the intrahepatic architecture of bile ducts, branches of the
portal vein, and the hepatic artery, the liver can be subdivided according to
the Couinaud classification. It divides the liver into eight independent
segments (IVIII), which is important for surgery and other interventions.
The gallbladder is a pear-shaped pouch attached to the inferior surface of
the right liver lobe. Via the cystic duct it is connected to the main bile duct.
2.6.2 Functional Task
The liver is called the “central laboratory” of the body. The liver synthesizes
and stores glycogen via glycogenesis and is responsible for gluconeogenesis to
provide glucose. In addition, protein metabolism with degradation and
neosynthesis are located here . Coagulation factors are produced as well as bile,
a yellowish-green liquid which is necessary to emulsify fat in the GI tract.
The bile juice is either transported directly into the duodenum or intermediately stored in the gallbladder where it is considerably concentrated.
2.6.3 Disorders and Diseases
Global destruction of the liver is caused by a variety of diseases such as
inflammation (“hepatitis”), alcohol, or metabolic diseases. In the case of
acute or chronic liver failure, the only option is liver transplantation.
Countless attempts have been made to create systems capable of taking over
the functional role of the liver—comparable to dialysis machines in the case
of kidney failure—but none of the designs is ready for clinical use yet.
33Anatomy, Physiology, and Selected Pathologies of the Gastrointestinal Tract
Severe damage to the liver leads to cirrhosis. The normal internal architecture of the parenchyma is destroyed and replaced by connective tissue and
scars. Blood perfusion is impaired and the pressure in the portal vein
increases (portal hypertension). Due to the higher resistance in the liver, the
blood flow seeks for deviations/shunts to reach its final goal—the right heart.
Portovenous shunts are opened (e.g., via the esophageal veins 8 esophageal
varices). However, these may cause life-threatening bleedings. The surgical
answer is to create dedicated portocaval shunts, but this type of surgery
is highly complicated with very high morbidity and mortality. Today,
transjugular intraparenchymatous shunts (TIPS) are the superior option.
Another severe complication of liver cirrhosis is the collection of fluid
in the abdomen (ascites). If medical treatment fails, dedicated shunt systems
may be required to provide the drainage of ascites back into the venous
vascular system (“peritoneovenous shunts”). Today, they can be placed
percutaneously
[14]. The shunts consist of the hose-system and a valve. To
prevent occlusion, the patient has to trigger an integrated pump regularly.
Recently, the first battery driven shunting pump was published
[15].
Primary (hepatocellular or cholangiocarcinoma) or secondary malignant
lesions (metastases) of the liver are the domain of hepatic surgical resection
whenever possible. Hepatic surgery is demanding and a less traumatic alternative would be desirable. In the last few years, less invasive interventions
were developed pertaining to local tumor obstruction either by freezing
(cryotherapy), electrical energy (radio ablation), or by focused ultrasound.
In addition, transv ascular tumor treatment by occluding hepatic blood flow
or the treatment with radioactive particles could become attractiv e options.
In epidemiological regards, however, diseases of the biliary system are
dominating. Surgical removal of the gallbladder (cholecystectomy) because
of symptomatic gallstones is one of the most often performed surgeries all
over the world (USA: approx. 500,000 cases/year). If stones are present in
the gallbladder only (cholecystolithiasis), a removal of the gallbladder is the
adequate treatment. If stones are also present in the bile ducts they must be
removed by additional interventions. In most instances, interventional
endoscopy is adequate today (see Chapter 8.4.4: Endoscopic Interventions
on the Bile Duct (ERCP)).
2.6.4 Biomedical Engineering Aspects
Healthy liver tissue (parenchyma) is very soft and difficult to handle. It is
covered by a thin capsule. The structure is mainly maintained by the
34
Biomedical Engineering in Gastrointestinal Surgery
Figure 2.11 The so-called hilus of the liver. Prior to resection, the left and right liver
artery and the hepatic duct have to be isolated. From MITI.
architecture of the internal canicular formations such as the arteries, the
portal veins, the hepatic veins, and the biliary tree (
Fig. 2.11). This
explains why dissection of the parenchyma is feasible with, e.g., the water
jet or ultrasound.
Producing an artificial implantable liver is still the “Holy Grail” of
biomedical engineering. Though many approaches are promising, they
are still far away from clinical maturity
[16]. Artificial livers would cer-
tainly revolutionize medicine. Beyond the treatment of liver failure, new
treatment options would become available for oncological diseases (primary or secondary liver lesions).
Today, still too many patients are lost since hepatic tumor manifestations are irresectable since the tumor mass is too extended or if too many
small tumors are diffusely infiltrating the whole organ. Transplantation
would be the only choice, but donors are by far too scarce, and liver
transplants are usually reserved for the treatment of nonmalignant disease.
If artificial organs were available “from the shelve,” a real breakthrough
in oncological surgery could be expected. Hopefully, this ambitious goal
can be reached as soon as possible.
In the meantime, BME could help to solve mid-term problems.
Table 2.5 numerates some important aspects, but the contr ibution of
BME must be even more comprehensive.
Improvement in local ablation techniques can only be fully utilized
if the destructive power is localized as precisely as possible to the target
area. This is why we need even better intraoperative inter vention
systems.
Anatomy, Physiology, and Selected Pathologies of the Gastrointestinal Tract
Table 2.5 Liver: selected diseases/disorders and BME aspects
Disease/disorder Treatment BME aspects
35
Focal lesions Surgical
resection
Portal hypertension
(bleeding, ascites)
Liver failure Transplantation “Artificial liver”
Figure 2.12 Pancreas: (A) Schematic drawing of the pancreas: (1) duodenum;
(2) head of the pancreas; (3) body; (4) tail; (B) 3D model of the pancreas. From (A)
M. Scholle, (B) MITI.
Portocaval
shunts
Local ablation
• Radiofrequency ablation
• Cryotherapy
• Highly focused ultrasound
• Electroporisation
TIPS, mechanical shunts, Alfa pump
2.7 PANCREAS
2.7.1 Anatomical Description
The pancreas is an elongate, hand axe-shaped gland which is hidden deep
in the human body in a retroperitoneal position behind the stomach and
the transverse colon. It is divided into a head, body, and tail (
The head of the pancreas is embraced by the duodenum. In the contact area between the head of the pancreas and the descending part of the
duodenum, the joint orifice of the bile duct and the pancreatic duct, the
so-called papilla, is located. The main pancreatic duct (Wirsung’s duct)
begins in the tail (which is very close to the spleen) and transverses the
whole gland.
Via branches from all sides, the pancreatic juice is collected into the
pancreatic duct. Gaining gradually in diameter the pancreatic duct opens
Fig. 2.12).
36 Biomedical Engineering in Gastrointestinal Surgery
together with the bile duct into the ampulla of Vater or papilla. The
parenchyma has a very delicate soft consistency which makes it difficult
to perform surgical manipulations.
2.7.2 Functional Task
The function of the pancreas is to produce both internal and external
secretion. The external secretion—pancreatic juice—cont ains various
enzymes like tr ypsin, amylase, and maltase. which are required for
the digestion of proteins, carbohydrates, and fat. The internal
secretion—insulin—is the product of the islands of Langerhans—a
special subgroup of cells in the pancreatic parenchyma. Insulin plays
a key role in glucose metabolism. Its production is part of a sophisticated regulatory circuit.
2.7.3 Disorders and Diseases
Diabetes mellitus is a very common metabolic disorder with increasing
incidence. It results from a relative or absolute deficit in insulin production. It has to be treated with regular insulin injections, since
insulin would be destroyed and inefficient if taken by mouth. Insulindependent diabetes has still today a severe impact on the duration and
quality of life.
Inflammation of the pancreas (“pancreatitis”) is an often lifethreatening event caused by bile or pancreatic obstruction, alcohol, or of
unknown reasons. Abscess formation and pseudocysts may arise.
Pancreatic cancer is often detected late because of the hidden
position of the gland and surgical resection is frequently impossible.
In these cases, chemotherapy and radiotherapy is used but the lo ngtermsuccessispoor.
2.7.4 Biomedical Engineering Aspects
It is little wonder, if the health care and economic impact of diabetes is
considered, that numerous attempts have been made already to develop
implantable insulin-regulating systems. Yet, not one single device is actually mature for a broader clinical use. The “insulin pump” is still a challenge for BME
The loss of the exocrine function of the pancreas is less severe,
since enzymes for digestion can easily be substituted by oral intake.
[17].
37Anatomy, Physiology, and Selected Pathologies of the Gastrointestinal Tract
The reduced acid buffering capacity is compensated by proton pump
inhibitors.
Insofar, the practical interest in developing an artificial
implantable pancreas is rather low. The regulation of insulin secretion
remains the dominant problem.
Innovative endoscopic instruments and procedures continuously
improve the treatment options in acute and chronic pancreatitis (e.g.,
stents and abscess drainage), but more has to be done to reduce morbidity
and mortality.
The most important problems, however, are malignancies of the
pancreas.
Both the diagnosis and the treatment of pancreatic cancer are still far
from being satisfying. Even the most sophisticated diagnostic modalities
are not sufficiently sensitive and specific to discriminate between inflammation and cancer. Radical surgical resection is most often impossible in
advanced cases and the 5-year survival rates after chemotherapy and radiation are disappointingly low.
Thermal ablation is not very suitable in pancreatic cancer due to
difficult navigation, the proximity to many large vessels, and the risk of
collateral damage
[18]. Innovative approaches for local tumor destruc-
tion with h igh selectivity would be requ ired. Maybe, electroporation
could be helpful. Endoluminal photodynamic therapy could be h elpful
as well (
Tab l e 2. 6 ). Most probably, the long-expected breakthrough in
the treatment can only be achieved by an alliance of improved diagnostic
methods, a more specific and effective chemotherapy, and advanced
BME tools
[19,20].
Table 2.6 Pancreas: selected diseases/disorders and BME aspects
Disease/disorder Treatment BME aspects
Internal pancreatic
insufficiency
Necrotizing pancreatitis Surgical drainage Percutaneous drainage
Cancer Surgical resection Improved diagnostic tools
Insulin injection Insulin-regulating systems
(“insulin pump”)Pancreatic
transplantation
Endoscopic debridement
Chemo/
radiotherapy
Local ablation
38 Biomedical Engineering in Gastrointestinal Surgery
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