This document provides a study guide for a lesson on appendicitis for medical students. It covers the key topics about appendicitis that students should know, including the embryology and anatomy of the appendix, the historical perspective and pathophysiology of appendicitis, the bacteriology and diagnosis of appendicitis through history, physical exam, laboratory tests and imaging. It also outlines the educational aims of the lesson and provides detailed content on each section for students to learn.

1. O.O.Bogomolets National Medical University
Department of Faculty Surgery #1
“Approved”
at the Methodist Faculty Surgery
Department # 1 Council
“__”_____2008, protocol #_____
Head of
Faculty Surgery Department # 1
Professor _______ M.P.Zakharash
Study Guide for Practical Work for Teachers and Students
Topic: “Appendicitis”.
Course 4
Foreign Students’ Medical Faculty
Duration of the lesson – 45 min.
Worked out by
Assistant T.Kravchenko
Kyiv
2008

2. I. The theme actuality
About 8% of people in Western countries have appendicitis at some time during their
life, with a peak incidence between 10 and 30 years of age. Acute appendicitis is the
most common general surgical emergency, and early surgical intervention improves
outcomes. The diagnosis of appendicitis can be elusive, and a high index of suspicion
is important in preventing serious complications from this disease.
II. Student must know:
- embryology and anatomy of appendix
- historical perspective of appendicitis
- pathophysiology of appendicitis
- bacteriology of appendicitis
- diagnosis of appendicitis
- diagnostic algorithm
- treatment
III. Student must be able to:
- to interpret correctly the present manifestations of disease and investigation
results
- to differentiate appendicitis
- to diagnose and make the chart of treatment
- to apply the instrumental methods of examination
- to conduct examination of patient
- to interpret data of examinations
IV. Education aims of the study
- forming the deontology presentations, skills of conduct with the patients

3. - to develop deontology presentations, be able to carry out deontology approach
to the patient
- to develop the presentations of influence of ecological and socio-economic
factors on the state of health
- to develop sence of responsibility for a timeliness and loyalty of professional
actions
- to lay hands on ability to set psychological contact with a patient and his family
V. The contents of a theme
Embryology and anatomy
The appendix, ileum, and ascending colon are all derived from the midgut. The
appendix first appears at the 8th week of gestation as an outpouching of the cecum
and gradually rotates to a more medial location as the gut rotates and the cecum
becomes fixed in the right lower quadrant.
The appendiceal artery, a branch of the ileocolic artery, supplies the appendix.
Histologic examination of the appendix indicates that goblet cells, which produce
mucus, are scattered throughout the mucosa. The submucosa contains lymphoid
follicles, leading to speculation that the appendix might have an important, as yet
undefined, immune function early in development. The lymphatics drain into the
anterior ileocolic lymph nodes. In adults, the appendix has no known function.
The length of the appendix varies from 2 to 20 cm, and the average length is 9 cm in
adults. The base of the appendix is located at the convergence of the taeniae along the
inferior aspect of the cecum, and this anatomic relationship facilitates identification of
the appendix at operation. The tip of the appendix may lie in a variety of locations.
The most common location is retrocecal but within the peritoneal cavity. It is pelvic in

4. 30% and retroperitoneal in 7% of the population. The varying location of the tip of the
appendix likely explains the myriad of symptoms that are attributable to the inflamed
appendix.
Historical Perspective
In 1886, Reginald Fitz of Boston correctly identified the appendix as the primary
cause of right lower quadrant inflammation. He coined the term appendicitis and
recommended early surgical treatment of the disease. Richard Hall reported the first
survival of a patient after removal of a perforated appendix, which launched focused
attention on the surgical treatment of acute appendicitis. In 1889, Chester McBurney
described characteristic migratory pain as well as localization of the pain along an
oblique line from the anterior superior iliac spine to the umbilicus. McBurney
described a right lower quadrant muscle-splitting incision for removal of the appendix
in 1894. The mortality rate from appendicitis improved with the widespread use of
broad-spectrum antibiotics in the 1940s. Recent advances have included improved
preoperative diagnostic studies, interventional radiologic procedures to drain
established periappendiceal abscesses, and the use of laparoscopy to confirm the
diagnosis and exclude other causes of abdominal pain. Laparoscopic appendectomy
was first reported by the gynecologist Kurt Semm in 1982 but has only gained
widespread acceptance in recent years.
Pathophysiology
Obstruction of the lumen is believed to be the major cause of acute appendicitis. This
may be due to inspissated stool (fecalith or appendicolith), lymphoid hyperplasia,
vegetable matter or seeds, parasites, or a neoplasm. The lumen of the appendix is
small in relation to its length, and this configuration may predispose to closed-loop
obstruction. Obstruction of the appendiceal lumen contributes to bacterial overgrowth,
and continued secretion of mucus leads to intraluminal distention and increased wall

5. pressure. Luminal distention produces the visceral pain sensation experienced by the
patient as periumbilical pain. Subsequent impairment of lymphatic and venous
drainage leads to mucosal ischemia. These findings in combination promote a
localized inflammatory process that may progress to gangrene and perforation.
Inflammation of the adjacent peritoneum gives rise to localized pain in the right lower
quadrant. Although there is considerable variability, perforation typically occurs after
at least 48 hours from the onset of symptoms and is accompanied by an abscess cavity
walled-off by the small intestine and omentum. Rarely, free perforation of the
appendix into the peritoneal cavity occurs that may be accompanied by peritonitis and
septic shock and can be complicated by the subsequent formation of multiple
intraperitoneal abscesses.
Bacteriology
The flora in the normal appendix is very similar to that in the colon, with a variety of
facultative aerobic and anaerobic bacteria. The polymicrobial nature of perforated
appendicitis is well established. Escherichia coli, Streptococcus viridans, and
Bacteroides and Pseudomonas species are frequently isolated, and many other
organisms may be cultured. Among patients with acute nonperforated appendicitis,
cultures of peritoneal fluid are frequently negative and are of limited use. Among
patients with perforated appendicitis, peritoneal fluid cultures are more likely to be
positive, revealing colonic bacteria with predictable sensitivities. Because it is rare
that the findings alter the selection or duration of antibiotic use, some authors have
challenged the traditional practice of obtaining cultures.
Bacteria Commonly Isolated in Perforated Appendicitis
1. AEROBIC
Bacteroides fragilis 80%
Bacteroides thetaiotaomicron 61%

6. Bilophila wadsworthia 55%
Peptostreptococcus species 46%
AEROBIC
Escherichia coli 77%
Streptococcus viridans 43%
Group D streptococcus 27%
Pseudomonas aeruginosa 18%
Diagnosis
History
Appendicitis needs to be considered in the differential diagnosis of nearly every
patient with acute abdominal pain. Early diagnosis remains the most important clinical
goal in patients with suspected appendicitis and can be made primarily on the basis of
the history and physical exam in most cases. The typical presentation begins with
periumbilical pain (due to activation of visceral afferent neurons) followed by
anorexia and nausea. The pain then localizes to the right lower quadrant as the
inflammatory process progresses to involve the parietal peritoneum overlying the
appendix. This classic pattern of migratory pain is the most reliable symptom of acute
appendicitis. A bout of vomiting may occur, in contrast to the repeated bouts of
vomiting that typically accompany viral gastroenteritis or small bowel obstruction.
Fever ensues, followed by the development of leukocytosis. These clinical features
may vary. For example, not all patients become anorexic. Consequently, the feeling of
hunger in an adult patient with suspected appendicitis should not necessarily deter one
from surgical intervention. Occasional patients have urinary symptoms or microscopic
hematuria, perhaps owing to inflammation of periappendiceal tissues adjacent to the
ureter or bladder, and this may be misleading. Although most patients with
appendicitis develop an adynamic ileus and absent bowel movements on the day of
presentation, occasional patients may have diarrhea. Others may present with small

7. bowel obstruction related to contiguous regional inflammation. Therefore,
appendicitis needs to be considered as a possible cause of small bowel obstruction,
especially among patients without prior abdominal surgery.
Physical Examination
Patients with acute appendicitis typically look ill and are lying still in bed. Low-grade
fever is common (∼38°C). Examination of the abdomen usually reveals diminished
bowel sounds and focal tenderness with voluntary guarding. The exact location of the
tenderness is directly over the appendix, which is most commonly at McBurney's
point (located one third of the distance along a line drawn from the anterior superior
iliac spine to the umbilicus). The normal appendix is mobile, so it may become
inflamed at any point on a 360-degree circle around the base of the cecum. Thus, the
site of maximal pain and tenderness can vary. Peritoneal irritation can be elicited on
physical examination by the findings of voluntary and involuntary guarding,
percussion, or rebound tenderness. Any movement, including coughing (Dunphy's
sign), may cause increased pain. Other findings may include pain in the right lower
quadrant during palpation of the left lower quadrant (Rovsing's sign), pain on internal
rotation of the hip (obturator sign, suggesting a pelvic appendix), and pain on
extension of the right hip (iliopsoas sign, typical of a retrocecal appendix).
Rectal and pelvic examinations are most likely to be negative. However, if the
appendix is located within the pelvis, tenderness on abdominal examination may be
minimal, whereas anterior tenderness may be elicited during rectal examination as the
pelvic peritoneum is manipulated. Pelvic examination with cervical motion may also
produce tenderness in this setting.
If the appendix perforates, abdominal pain becomes intense and more diffuse, and
abdominal muscular spasm increases, producing rigidity. The heart rate rises, with an
elevation of temperature above 39°C. The patient may appear ill and require a brief
period of fluid resuscitation and antibiotics before the induction of anesthesia.

8. Occasionally, pain may improve somewhat after rupture of the appendix, although a
true pain-free interval is uncommon.
Laboratory Studies
The white blood cell count is elevated with more than 75% neutrophils in most
patients. A completely normal leukocyte count and differential is found in about 10%
of patients with acute appendicitis. A high white blood cell count (>20,000/mL)
suggests complicated appendicitis with either gangrene or perforation. A urinalysis
can also be helpful in excluding pyelonephritis or nephrolithiasis. Minimal pyuria,
frequently seen in elderly women, does not exclude appendicitis from the differential
diagnosis because the ureter may be irritated adjacent to the inflamed appendix.
Although microscopic hematuria is common in appendicitis, gross hematuria is
uncommon and may indicate the presence of a kidney stone. Other blood tests are
generally not helpful and are not indicated in the patient with suspected appendicitis.
Radiography
Although they are commonly obtained, the indiscriminate use of plain abdominal
radiographs in the evaluation of patients with acute abdominal pain is unwarranted. In
one study of 104 patients with acute onset of right lower quadrant pain, interpretation
of plain x-rays changed the management of only 6 patients (6%), and in one case
contributed to an unnecessary laparotomy. A calcified appendicolith is visible on plain
films in only 10% to 15% of patients with acute appendicitis; however, its presence
strongly supports the diagnosis in a patient with abdominal pain. Plain abdominal
films may be useful for the detection of ureteral calculi, small bowel obstruction, or
perforated ulcer, but such conditions are rarely confused with appendicitis. Failure of
the appendix to fill during a barium enema has been associated with appendicitis, but
this finding lacks both sensitivity and specificity because up to 20% of normal
appendices do not fill.

9. Among patients with abdominal pain, ultrasonography has a sensitivity of about 85%
and a specificity of more than 90% for the diagnosis of acute appendicitis.
Sonographic findings consistent with acute appendicitis include an appendix of 7 mm
or more in anteroposterior diameter, a thick-walled, noncompressible luminal
structure seen in cross section referred to as a target lesion, or the presence of an
appendicolith. In more advanced cases, periappendiceal fluid or a mass may be found.
Ultrasonography has the advantages of being a noninvasive modality requiring no
patient preparation that also avoids exposure to ionizing radiation. For these reasons,
it is commonly used in children and in pregnant patients with equivocal clinical
findings suggestive of acute appendicitis. Disadvantages of ultrasonography include
operator-dependent accuracy and difficulty interpreting the images by those other than
the operator. Because performance of the study may require hands-on participation by
the radiologist, ultrasonography may not be readily available at night or on weekends.
Pelvic ultrasound can be especially useful in excluding pelvic pathology, such as tubo-
ovarian abscess or ovarian torsion, that may mimic acute appendicitis.
Ultrasound of a normal appendix illustrating the thin wall in both coronal (left) and
longitudinal (right) planes. In appendicitis, there is distention and wall thickening and
blood flow is increased, leading to the so-called ring-of-fire appearance.
Computed tomography (CT) is commonly used in the evaluation of adult patients with
suspected acute appendicitis. Improved imaging techniques, including the use of 5-
mm sections, have resulted in increased accuracy of CT scanning, which has a
sensitivity of about 90% and a specificity of 80% to 90% for the diagnosis of acute
appendicitis among patients with abdominal pain. Controversy remains as to the
importance of intravenous, oral gastrointestinal, and rectal contrast in improving
diagnostic accuracy. In general, CT findings of appendicitis increase with the severity
of the disease. Classic findings include a distended appendix greater than 7 mm in
diameter and circumferential wall thickening, which may give the appearance of a
halo or target. As inflammation progresses, one may see periappendiceal fat stranding,

10. edema, peritoneal fluid, phlegmon, or a periappendiceal abscess. CT detects
appendicoliths in about 50% of patients with appendicitis and also in a small
percentage of people without appendicitis. Among patients with abdominal pain, the
positive predictive value of the finding of an appendicolith on CT remains high at
about 75%.
CT scan of the abdomen or pelvis in a patient with acute appendicitis may reveal an
appendicolith, CT typically shows a distended appendix with diffuse wall-thickening
and periappendiceal fluid. The appendix may be described as having mural
stratification, referring to the layers of enhancement and edema within the wall and
this may also be referred to as a target sign. cecum; terminal ileum.
Should CT be used routinely in the diagnostic evaluation of patients with suspected
appendicitis? In our opinion, no. In the setting of typical right lower quadrant pain and
tenderness with signs of inflammation in a young patient, a CT scan is unnecessary,
wastes valuable time, and exposes the patient to the risks for allergic contrast reaction,
nephropathy, aspiration pneumonitis, and ionizing radiation. The latter carries
increased risk in children in whom the rate of radiation-induced cancer has been
estimated at 0.18% following an abdominal CT scan. Moreover, a negative study may
be misleading, particularly early in the inflammatory process. CT has proved most
valuable among older patients in whom the differential diagnosis is lengthy, the
clinical findings may be confusing, and appendectomy carries increased risk. Among
patients with atypical symptoms, CT scan may reduce the negative appendectomy rate
(i.e., the fraction of pathologically normal appendices that are removed). Selective use
of CT scans seems most appropriate, and as always, the study needs to be obtained
only in settings in which it has a significant potential to alter management.
The morbidity of perforated appendicitis far exceeds that of a negative appendectomy.
Thus, the strategy has been to set a low enough threshold for removal of the appendix
so as to minimize the cases of missed appendicitis. With increased use of CT scans,
the frequency of negative explorations has declined in recent years without an

11. accompanying rise in the number of perforations. A recent analysis of more than
75,000 patients in 1999 to 2000 revealed a negative appendectomy rate of 6% in men
and 13.4% in women.
Diagnostic Laparoscopy
Although most patients with appendicitis will be accurately diagnosed based on
history, physical exam, laboratory studies, and if necessary, imaging techniques, there
are a small number in whom the diagnosis remains elusive. For these patients,
diagnostic laparoscopy can provide both a direct examination of the appendix and a
survey of the abdominal cavity for other possible causes of pain. We use this
technique primarily for women of childbearing age in whom preoperative pelvic
ultrasound or CT scan fails to provide a diagnosis. Concerns about the possible
adverse effects of a missed perforation and peritonitis on future fertility sometimes
prompt earlier intervention in this patient population.
Diagnostic Algorithm
Patients in whom the diagnosis of appendicitis is being considered should have a
surgical evaluation. Early involvement of the surgical team in the diagnostic
evaluation of these patients may improve diagnostic accuracy and help to avoid
expensive and unnecessary diagnostic studies. Experienced clinicians accurately
diagnose appendicitis based on a combination of history, physical exam, and
laboratory studies about 80% of the time. We stratify patients based on their clinical
findings starting with the extremes, which are easier to identify. Patients with a high
probability of uncomplicated appendicitis undergo surgery. Patients suspected of
having an appendiceal abscess undergo further imaging, typically ultrasonography for
children or CT for adults. The next step in the evaluation of patients in whom the
likelihood of appendicitis is believed to be low is determined by the probability and
severity of alternate diagnoses under consideration. Many of these patients will be
discharged with a planned follow-up visit or phone call the next day. Most older
patients with abdominal pain undergo CT before discharge because of the high

12. prevalence of surgical pathology in this patient population. The remaining patients are
believed to have an intermediate probability of having appendicitis. Children and
pregnant women in this category typically undergo abdominal ultrasonography.
Women in their childbearing years may undergo pelvic ultrasonography or CT scan
depending on the index of suspicion of pelvic pathology. Among patients that would
otherwise be admitted to the hospital for observation, CT may reduce hospital costs by
reducing length of stay. Following the completion of imaging studies, the patient is re-
examined to determine whether pain and tenderness have localized to the right lower
quadrant. If the diagnosis remains uncertain at this point, patients either undergo
diagnostic laparoscopy, especially in fertile women, are admitted for observation and
re-examination, or are discharged with follow-up the next day.
Treatment
Most patients with acute appendicitis are managed by prompt surgical removal of the
appendix. A brief period of resuscitation is usually sufficient to ensure the safe
induction of general anesthesia. Preoperative antibiotics cover aerobic and anaerobic
colonic flora. For patients with nonperforated appendicitis, a single preoperative dose
of antibiotics reduces postoperative wound infections and intra-abdominal abscess
formation. Postoperative oral antibiotics do not further reduce the incidence of
infectious complications in these patients. For patients with perforated or gangrenous
appendicitis, we continue postoperative intravenous antibiotics until the patient is
afebrile.
Several prospective randomized studies have compared laparoscopic and open
appendectomy, and the overall differences in outcomes remain small. The percentage
of appendectomies performed laparoscopically continues to increase. Obese patients
had less pain and shorter hospital stays after laparoscopic versus open appendectomy.
Patients with perforated appendicitis had lower rates of wound infections following

13. laparoscopic removal of the appendix. Patients treated laparoscopically had improved
quality-of-life scores 2 weeks after surgery and lower readmission rates. As compared
with open appendectomy, the laparoscopic approach involves higher operating room
costs, but these have been counterbalanced in some series by shorter lengths of stay.
For patients in whom the diagnosis remains uncertain after the preoperative
evaluation, diagnostic laparoscopy is useful because it allows the surgeon to examine
the remainder of the abdomen, including the pelvis, for abnormalities. Our practice is
to perform appendectomies laparoscopically in fertile women, obese patients, and
cases of diagnostic uncertainty; otherwise, the approach is determined by patient or
surgeon preference.
Open appendectomy is usually easily performed through a transverse right lower
quadrant incision (Davis-Rockey) or an oblique incision (McArthur-McBurney). In
cases with a large phlegmon or diagnostic uncertainty, a subumbilical midline incision
may be used. For uncomplicated cases we prefer a transverse, muscle-splitting
incision lateral to the rectus abdominis muscle over McBurney's point. Local
anesthetic, administered before the incision, reduces postoperative pain. After the
peritoneum is entered, the inflamed appendix is identified by its firm consistency and
delivered into the field. Particular attention is paid to gentle handling of the inflamed
tissues to minimize the risk for rupture during the procedure. In difficult cases,
enlarging the incision and working down the trajectory of the taeniae on the cecum
will often facilitate localization and delivery of the appendix. The meso-appendix is
divided between clamps and ties. The base of the appendix is skeletonized at its
junction with the cecum. A heavy absorbable tie is placed around the base of the
appendix, and the specimen is clamped and divided. An absorbable purse-string suture
or Z stitch is placed into the cecal wall, and the appendiceal stump is inverted into a
fold in the wall of the cecum. Simple ligation and inversion probably have equivalent
outcomes. If the base of the appendix and adjacent cecum are extensively indurated,

14. an ileocecal resection is performed. The wound is closed primarily in most cases
because the wound infection rate is less than 5%.
Laparoscopic appendectomy offers the advantage of diagnostic laparoscopy combined
with the potential for shorter recovery and incisions that are less conspicuous. If a CT
scan was obtained preoperatively, it needs to be reviewed by the surgeon for useful
information regarding the position of the appendix relative to the cecum. After
injection of local anesthetic, we place a 10-mm port into the umbilicus, followed by a
5-mm port in the suprapubic midline region and a 5-mm port midway between the
first 2 ports and to the left of the rectus abdominis muscle. The 5-mm, 30-degree
scope is moved to the central port with the surgeon and assistant both on the patient's
left. With the patient in Trendelenburg's position and rotated left-side down, we gently
sweep the terminal ileum medially and follow the taeniae of the cecum caudad to
locate the appendix, which is then elevated. The mesoappendix is divided using a 5-
mm harmonic scalpel or Liga-Sure, or between clips, depending on the thickness of
this tissue. We typically encircle the appendix with two heavy absorbable Endoloops
cinched down at the base of the appendix and then place a third Endoloop about 1 cm
distally and divide the appendix. In cases in which the base is indurated and friable,
we use a 30-mm endoscopic stapler to divide the appendix. For most cases, however,
the considerable added cost of the stapler is unwarranted. Any spillage of fluid is
promptly aspirated, and similarly any identified appendicoliths are removed to prevent
postoperative abscess formation. The appendix is placed into a specimen bag and
removed with the port through the umbilical wound. Fascia at the 10-mm trocar site is
closed, and all wounds are closed primarily.
VI. Lesson topic control questions.
Key points:
- Acute appendicitis is the most common general surgical emergency, and early
surgical intervention improves outcomes.

15. - The diagnosis of appendicitis can be elusive, and a high index of suspicion is
important in preventing serious complications from this disease.
- Appendicitis needs to be considered in the differential diagnosis of nearly every
patient with acute abdominal pain.
- Early diagnosis remains the most important clinical goal in patients with suspected
appendicitis and can be made primarily on the basis of the history and physical
exam in most cases.
- In some cases diagnosis is not easy and includes, endoscopy, ultrasound, plain
abdominal films or CT, laboratory tests and laparoscopy
- Appendectomy remains the only curative treatment for appendicitis
Cases
(1)
A 15-year-old boy is admitted and physical findings consistent with appendicitis.
Which finding is most likely to be positive?
1. Pelvic crepitus
2. Iliopsoas sign
3. Murphy sign
4. Flank echymosis
5. Periumbilical ecchymosis
The answer is 2.
The iliopsoas sign in the lower abdomen and psoas region that is elicited when thigh is
flexed against resistance. It suggests an inflammatory process, such as appendicitis.
Crepitus suggests a rapidly spreading gas-forming infection. Murphy sign is elicited
by palpating the right upper quadrant during inspiration and suggests acute
cholecystitis. Flank and periumbilical ecchymoses suggest retroperitoneal
hemorrhage.

16. (2)
A 23-years-old male presents to the emergency room (ER) at night with abdominal
pain beginning the prior afternoon. The pain is described as crampy with intermittent
episodes of sharp pain, and non radiating. It is located in the right lower quadrant
(RLQ) with an intensity of 8/10 which has progressively worsened since it started. He
also has nausea and vomiting that began soon after onset of pain. He denies fever ,
chills, or dysuria. Physical examination revealed RLQ tenderness, no palpable masses,
a soft abdomen, with normal bowel sounds. He states no change in bowel habits. Lab
studies reveal negative urine analysis (UA), WBC of 13,500, and Hgb gms/dl. The
patient is taken to the operating room (OR) without obtaining a computed tomography
(CT) scan of the abdomen and pelvis. Intra-operatively, the appendix appears normal.
On further evaluation, the distal ileum appears inflamed with fat wrapping. Your
notice the cecum is not involved. What is your management at this time?
1. Perform appendectomy
2. Leave appendix and ileum as-is and close. Colsult GI
3. Perform appendectomy and distal ileum resection
4. Perform appendectomy and stricturoplasty of the terminal ileum
5. Run the small bowel to rule out Meckel’s diverticulum
Answer is 1.
The patient presented with a classic history for appendicitis. Twenty percent of all
explorations for appendicitis turn out to be negative; therefore, other sources of pain
must be sought. On exploration, the patient had classical sighns of Crohn’s disease,
including fat wrapping, which is pathognomonic for Crohn’s disease. Differentiating
Crohn’s from appendicitis is extremely difficult, especially without preoperative CT
of abdomen/pelvis. The history of previous episodes of colicky abdominal pain with
bouts of diarrhea may lead to a suspected diagnosis of Crohn’s. Management of
disease intraoperatively is to perform appendectomy if no cecal involvement in order

17. to eliminate possibility of appendicitis versus Crohn’s in the future. If the cecum is
involved you do not perform appendectomy because of risk of fistula formation.
VII. Supporting materials required for teaching
1. Participation in clinical duties on admission
2. Working in library
VII. Literature
1. Townsend CM, Harris JW. Sabiston’s Textbook of Surgery, 16th ed. Philadelphia,
PA: W.B. Saunders Co, 2001, vol.44
2. Schwartz SI, Schires GT, Spencer FC, Daly JM, Fischer JE, Galloway AC.
Principles of Surgery, 7th ed. New York: McGraw-Hill, 1999, vol.27
3. Bruce E. Jarrell, R.Antthony Carabasi. Surgery, 3rd ed. Williams & Wilkins, 1998