Appendix

Anatomy and physiology

Shuo HuangSpecialist surgeonAssociate professorJiamusi University Hospital, China154 002 JiamusiTelephone: +86-454-862-3466Email: shuo.huang@hotmail.com

In infants, the appendix is a conical diverticulum at the apex of the cecum, but with differential growth and distention of the cecum, the appendix ultimately arises on the left and dorsally approximately 2.5 cm below the ileocecal valve.The taeniae of the colon converge at the base of the appendix, an arrangement that helps in locating this structure at operation.The appendix is fixed retrocecally in 16% of adults and is freely mobile in the remainder.

The appendix in youth is characterized by a large concentration of lymphoid follicles that appear 2 weeks after birth and number about 200 or more at age 15.Thereafter, progressive atrophy of lymphoid tissue proceeds concomitantly with fibrosis of the wall and partial or total obliteration of the lumen.

If the appendix has a physiologic function, it is probably related to the presence of lymphoid follicles.Reports of a statistical relationship between appendecotomy and subsequent carcinoma of the colon and other neoplasms in humans are not supported by controlled studies.

Acute appendicitis

Essentials of diagnosis

Abdominal painAborexia, nausea and vomitingLocalized right lower quadrant abdominal tendernessLow-graded fewerLeukocytosis

General considerations

Approximately 7% of people in Western countries have appendicitis at some time during their lives, and about 200,000 appendectomies for acute appendicitis are performed annually in the United States.The incidence has been steadily dropping over the past 25 years, however, while the incidence in developing countries which in the past has been quite low has been rising in proportion to economic gains and changes in lifestyle.

Obstruction of the proximal lumen by fibrous bands, lymphoid hyperplasia, fecaliths, calculi, or parasites has long been considered to be the major cause of acute appendicitis, though that theory is doubted by many experts.

Evidence of temporal and geographic clustering of cased has suggested a primary infectious etiology.A fecalith or calculus is found in only 10% of acutely inflamed appendicices.

As appendicitis progresses, the blood supply is impaired by bacterial infection in the wall and distention of the lumen by pus; gangrene and perforation occur at about 24 hours, though the timing is highly variable.

Gangrene implies microscopic perforation and bacterial peritonitis (which may be localized by adhesions from nearby viscera).

Clinical findings

Acute appendicitis has protean manifestations.It may simulate almost any other acute abdominal illness and in turn may be mimicked by a variety of conditions.Progression of symptoms and signs is the rule in contrast to the fluctuating course of some other disease.

A. Symptoms and Signs

Typically, the illness begins with vague mid-abdominal discomfort followed by nausea, anorexia, and indigestion.The pain is persistent and continuous but not severe, with occasional mild cramps.These may be an episode of vomiting, and within several hours the pain shifts to the right lower quadrant, becoming localized and causing discomfort on moving, walking, or coughing.The patient may feel constipated.

Examination at this point shows localized tenderness to one finger palpation and perhaps slight muscular guarding.

Rebound or percussion tenderness (the latter provides the same information more humanely) may be elicited in the same area.Peristalsis is normal or slightly reduced.Rectal and pelvic examinations are likely to be negative.The temperature is only slightly elevated (eg, 37.8° C) in the absence of perforation.

Contrary to traditional teaching, tenderness on rectal examination is not a sign of acute appendicitis.If present, it more often points to another cause of the symptoms.Another common misconception is that inflammation in a retrocecal appendix produces an atypical syndrome.This too is incorrect; the clinical findings in this situation are the same as for ordinary (antececal) appendicitis.

Rarely, the cecum may lie on the left side of the abdomen, and appendicitis may be mistaken for sigmoid diverticulitis.An inflamed appendix in the right upper quadrant may mimic acute cholecystitis or performed ulcer.Even when the cecum is normally situated, a long appendix may reach to other parts of the abdomen, and acute appendicitis in these circumstances may be very confusing indeed.

A couple of general points are worth remembering: (1) People with early (non-perforated) appendicitis often do not appear ill and may even apologize for taking your time.Finding localized tenderness over McBurney’s point is the cornerstone of diagnosis.(2) A rule that will help considerably with atypical cases is never to place appendicitis lower than second in the differential diagnosis of acute abdominal pain in a previously healthy person.

B. Laboratory Findings

The average leukocyte count is 15 ×109/L, and 90% of patients have counts over 10 ×109/L.In three-fourths of patients, the differential white count shows more than 75% neutrophils.It must be emphasized, however, that one patient in ten with acute appendicitis has a leukocyte count indistinguishable from normal, and many have normal differential cell counts.Appendicitis in patients infected whit HIV produces the same syndrome as in other people, but the white blood cell count is usually normal.

The urine is usually normal, but a few leukocytes and erythrocytes and occasionally even gross hematuria may be noted, particularly in retrocecal or pelvic appendicitis.

C. Imaging Studies

Localized hair- fluid levels, localized ileus, or increased soft tissue density in the right lower quadrant is present in 50% of patients with early acute appendicitis.Less common findings are a calculus, an altered right psoas shadow, or an abnormal right flank stripe.The finding on plain films of a calculus in the right lower quadrant coupled with pain in this area strong supports a diagnosis of appendicitis.Although perforated peptic ulcer is by far the most common cause of free intraperitoneal air, free air is also a rare manifestation of performed appendicitis.In general, however, the findings on plain films are nonspecific and rarely of help in diagnosis. A suggestion that barium enema may contribute to the diagnosis has not been supported by experience.

A spiral CT examination of the appendix may be of help in diagnosis.An enlarged appendix with peri-appendiceal fat stranding, found in 90% of cases, is the most common CT finding of acute appendicitis.Other criteria are less reliable.CT scans are of greatest value in patients with less than typical clinical and laboratory findings, where a positive study would be an indication for appendectomy.In the face of typical right lower4 quadrant pain and tenderness plus signs of inflammation (eg, fever, leukocytosis), a CT scan would be superfluous and, if negative, even misleading.Ultrasound imaging is much less reliable that CT.When appendicitis is accompanied by a right lower quadrant mass, an ultrasound or CT scan should be obtained to differentiate between a periappendiceal phlegmon and an abscess.

D. Appendicitis during pregnancy

Appendicitis is the most common non-obstetric surgical disease of the abdomen during pregnancy.Pregnant women develop appendicitis with the same frequency as do non-pregnant women of the same age, and the cases are equally distributed through the three trimesters of pregnancy.By far the most common presentation is right lower quadrant pain and tenderness- the classic syndrome- but the enlarged uterus occasionally will have pushed the appendix into the right upper quadrant, which gives rise to pain in this location.

Fever is less common than with appendicitis in the absence of pregnancy.Leukocytosis is typical, but it too may be absent.The main problem is to recognize the possibility of appendicitis and perform

appendectomy promptly.Delay in operation runs a higher than usual risk of perforation and diffuse peritonitis, because omentum is less available to wall off the infection.The mother is in greater jeopardy of serious abdominal infection, and the fetus is more vulnerable to premature labor with complications.Laparoscopic appendectomy (specifically the penumoperitoneum) is well tolerated by the mother and the fetus, but the frequency of technical complications is higher than with the open approach.Appendectomy during pregnancy is often followed by preterm labor but rarely by preterm delivery.Early appendectomy has decreased the maternal death rate to under 0.5% and the fetal death rate to fewer than 10%.

Diagnosis and differential diagnosis

The clinical diagnosis of appendicitis rests on a combination of localized pain and tenderness accompanied by signs of inflammation, such as fever, leukocytosis, and elevated C-reactive protein levels.Migration of pain from the periumbilical area to the right lower quadrant is also diagnostically significant.In the absence of signs of inflammation, the diagnosis is less certain (ie, falsely positive), and in this situation a CT scan might be of value.The best strategy in equivocal cases is to observe the patient for a period of 6 hours or more.During this time, patients with appendicitis experience increasing pain and signs of inflammation and those without appendicitis generally improve.False-positive diagnoses often involve cases where the surgeon has accorded more significance to the patient’s sign than to the presence or absence of inflammatory signs.Anorexia, nausea, and rectal of inflammatory are not indicative signs of appendicitis.During the past 15 years, the overall false- positive rate for the diagnosis of appendicitis has dropped from 15% to 10% without an accompanying rise in the number of perforations.Thus, diagnostic accuracy appears to be improving.

The diagnosis of acute appendicitis is particularly difficult in the vary young and in the elderly.These are the groups where diagnosis is most often delayed and perforation most common.Infants manifest only lethargy, irritability, and anorexia in the early stages, but vomiting, fever, and pain are apparent as the disease progresses.Classic symptoms may not be elicited in aged patients, and the diagnosis is often not considered by the examining physician.The course of appendicitis is more virulent in the elderly, and suppurative

complications occur earlier.

The highest incidence of false-positive diagnosis (20%) is in women between ages 20 and 40 and is attributable to pelvic inflammatory disease and other gynecologic conditions.Compared with appendicitis, pelvic inflammatory disease is more often associated with bilateral lower quadrant tenderness, left adnexal tenderness, onset of illness within 5 days of the last menstrual period, and a history that does not include nausea and vomiting.Cervical motion tenderness is common in both diseases.

Complications

The complications of acute appendicitis include perforation, peritonitis, abscess, and pylephlebitis.

A. Perforation

Delay in seeking medical care appears to be the principal reason for perforations; the disease has just been allowed to progress according to its natural history.Perforation is accompanied by more severe pain and higher fever (averge, 38.3 ºC) than in appendicitis.It is unusual for the acutely inflamed appendix to perforate within the first 12 hours.The appendicitis has progressed to perforation by the time of appendectomy in about 50% of patients under age 10 or over age 50.Nearly all deaths occur in the latter group.

The acute consequences of perforation vary from generalized peritonitis to formation of a tiny abscess that may not appreciably alter the symptoms and signs of appendicitis.Perforation in young women increases the subsequent risk of tubal infertility about four-fold.

B. Peritonitis

Localized peritonitis results from microscopic perforation of a gangrenous appendix, while spreading or generalized peritonitis usually implies gross perforation into the free peritoneal cavity.Increasing tenderness and rigidity, abdominal distention, and adynamic ilus are obvious in patients with peritonitis.High fever and severe toxicity mark progression of this catastrophic illness in untreated patients.

C. Appendiceal Abscess (Appendicealmass)

Localized perforation occurs when the periappendiceal infection becomes walled off by omentum and adjacent viscera.The clinical presentation consists of the usual findings in appendicitis plus a right lower quadrant mass.An ultrasound or CT scan should be performed; if an abscess in found, it is best treated by percutaneous ultrasound-guided aspiration.Opinion differs about how every small abscesses and phlegmons should be handled.Some surgeons prefer a regimen consisting of antibiotics and expectant management followed by elective appendectomy 6 weeks later.The purpose is to avoid spreading the localized infection, which usually resolves in response to the antibiotics.Other surgeons recommended immediate appendectomy, which considerably shortens the duration of the illness.The trend is in favor of the latter approach, since it is more expeditious and appears to be just as safe.

When the surgeon encounters as unsuspected abscess during appendectomy, it is usually best to proceed and remove the appendix.If the abscess is large and further dissection would be hazardous, drainage alone is appropriate.

Appendicitis recurs in only 10% of patients whose initial treatment consisted of antibiotics or antibiotics plus drainage of an abscess.Therefore, when the presence of ancillary conditions increases the risks of surgery, interval appendectomy may be postponed unless symptoms recur.

D. Phylephlebitis

Pylephlebitis is suppurative thrombophlebitis of the portal venous system.Chills, high fever, low grade janundice, and, later, hepatic abscess are the hallmarks of this grave condition.The appearance of shaking chills in a patient with acute appendicitis demands vigorous antibiotic therapy to prevent the development of pylephlebitis.

CT scanning is the best means of detecting thrombosis and gas in the portal vein.In addition to antibiotics, prompt surgery is indicated to treat appendicitis or other primary sources of infection (eg, diverticulitis).

Prevention

In the past it was common to perform an incidental appendectomy in people under age 50 during the course of an abdominal operation for another illness- as long as the exposure was adequate and there were no specific contraindications.The declining lifetime risk of appendicitis now calls this practice into question.

A related question concerns the appropriate course when a laparoscopy is performed for presumptive appendicitis and the appendix looks normal.The trend in this case is to leave the appendix intact- not to remove it prophylactically or on the assumption that the visual assessment may be inaccurate.

Treatment

With few exceptions, the treatment of appendicitis is surgical (ie, appendectomy).The operation can be done open or laparoscopically.The results of clinical trails comparing the two methods show no clear-cut advantage of one method over the other, though patients treated laparoscopically return to work a few days earlier.A laparoscopic approach is desirable when the preoperative diagnosis is uncertain because the morbidity is less if the appendix is found to be uninflamed and an appendectomy is not done.

Prophylactic antibiotics are indicated preoperatively.A single-drug regimen, usually a cephalosporin, is as effective as more aggressive multiple-drug combinations.The practice of routinely culturing abdominal fluid is of no practical value even when the appendix has perforated.The organisms obtained are the usual fecal flora.

Abdominal drains are called for only to treat established abscesses, not for diffuse inflammation or abdominal fluid.

If a patient with appendicitis cannot be taken to a modern surgical facility for care, treatment should consist of antibiotics alone.The complication-free success rate of this approach is high.

Prognosis

Although a death rate of zero is theoretically attainable in acute appendicitis, deaths still occur, some of which are avoidable.The death rate in simple acute appendicitis is approximately 0.1% and has not changed significantly since 1930.Progress in pre- and postoperative care- particularly the emphasis on fluid replacement before operation- has reduced the death rate from perforation to about 5%.Nonetheless, postoperative infections still occur in 30% of cases of gangrenous or perforated appendix.Although most of these patients survive, many near fatalities increase in tubal infertility that follows perforation in young women is also avoidable by early appendectomy.

Chronic appendicitis

Chronic abdominal pain is a common problem, and when the complaints are confined to the right lower quadrant, the question of chronic appendicitis is usually raised.Patients with genuine chronic appendicitis experience pain that lasts for 3 weeks or more.The history usually includes an acute illness at some time in the past, compatible with acute appendicitis, the appendix is chronically inflamed or fibrotic.The symptoms resolve with appendectomy.

Chronic intermittent pain in the right lower quadrant is most often caused by something other than appendicitis, such as Crohn’s disease or renal disease.Barium X-rays are sometimes helpful, particularly in children.In many patients, the diagnosis is not obvious.Appendectomy relieves symptoms occasionally, but laparotomy for chronic abdominal pain is generally unproductive in the absence of objective findings (eg, localized tenderness, palpable mass, leukocytosis).

Tumors of the appendix

Benign tumors, including carcinoids, were found in 4.6% of 71,000 human appendix specimens examined microscopically.Benign neoplasms may arise from any cellular and are usually incidental findings.Occasionally, a neoplasm obstructs the appendiceal lumen and produces acute appendicitis.No treatment other than appendectomy is indicated.

Malignant tumors

Primary malignant tumors were found in 1.4% of appendices in the same large series.Carcinoid and argentaffin tumors comprise the majority of appendiceal cancers, and the appendix is the commonest location of carcinoid tumors of the gastrointestinal tract.Carcinoid tumors of the appendix are usually benign, but the uncommon tumor that is over 2 cm in diameter may exhibit malignant behavior.Most appendiceal carcinoids are found in the tip of the organ, while a few are at the base.About half of these tumors are discovered during an appendectomy for acute appendicitis, and the remainders are incidental findings.Lesions less than 2 cm in diameter invade the appendiceal wall in 25% of cases, but only 3% metastasize to lymph nodes, and hepatic metastases and the carcinoid syndrtome are truly rare.Appendectomy alone is adequate treatment unless the lymph nodes are visibly

involved, the tumor is more than 2 cm diameter, mucinous elements are present in the tumor (adeno-carcinoid), or the mesoappendix or base of the cecum is invaded.Right hemicolectomy is recommended for these more aggressive lesions.

Adeno-carcinoma of the colonic type can arise in the appendix and spread rapidly to regional lymph nodes or implant on ovaries or other peritoneal surfaces.Ten percent of patients have widespread metastases when first seen.Adeno-carcinoma is virtually never diagnosed preoperatively; about half of cases present as acute appendicitis, and 15% have formed apepndiceal abscesses.Right hemicolectomy should be performed if disease is localized to the appendix and regional lymph nodes.The 5-year survival rate is 60% after right hemicolectomy and only 20% after appendectomy alone, but the later group includes patients with distant meatstases at the time of diagnosis.

Mucocele

Mucocele of the appendix is a cystic, dilated appendix filled with mucin.Simple mucocele is not a neoplasm and results from chronic obstruction of the proximal lumen, usually by fibrous tissue.If the appendiceal contents distally are sterile, mucous cells continue to secrete until distention of the lumen thins the wall and interferes with nutrition of the lining cells; histologically, simple mucocele is lined by flattened cuboidal epithelium or no epithelium at all.Simple mucocele is cured by appendectomy.Less commonly, mucocele is caused by a neoplasm- cystadenoma, or adenocarcinoma grade 1 in the older terminology.This lesion may arise de novo or (perhaps) in a preceding simple mucocele.In cystadenoma, the lumen is filled with mucin but the wall is lined by columnar epithelium with papillary projections.

Tumor does not infiltrate the appendiceal wall and does not metastasize, although it may recur locally after appendectomy.Cystadenoma is believed to undergo malignant change in some instances.Appendectomy is adequate treatment.