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The lifetime risk of developing appendicitis is 8.6% for males and 6.7% for females, with the highest incidence in the second and third decades.21 The rate of appendectomy for appendicitis has been decreasing since the 1950s in most countries. In the United States, it reached its lowest incidence rate of about 15 per 10,000 inhabitants in the 1990s.22 Since then, there has been an increase in the incidence rate of nonperforated appendicitis. The reason for this is not clear, but it has been proposed that the increased use of diagnostic imaging has led to a higher detection rate of mild appendicitis that would otherwise resolve undetected.
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Etiology and Pathogenesis
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The etiology and pathogenesis of appendicitis are not completely understood. Obstruction of the lumen due to fecaliths or hypertrophy of lymphoid tissue is proposed as the main etiologic factor in acute appendicitis. The frequency of obstruction rises with the severity of the inflammatory process. Fecaliths and calculi are found in 40% of cases of simple acute appendicitis,23 in 65% of cases of gangrenous appendicitis without rupture, and in nearly 90% of cases of gangrenous appendicitis with rupture.24
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Traditionally, the belief has been that there is a predictable sequence of events leading to eventual appendiceal rupture. The proximal obstruction of the appendiceal lumen produces a closed-loop obstruction, and continuing normal secretion by the appendiceal mucosa rapidly produces distension. Distension of the appendix stimulates the nerve endings of visceral afferent stretch fibers, producing vague, dull, diffuse pain in the mid-abdomen or lower epigastrium. Distension increases from continued mucosal secretion and from rapid multiplication of the resident bacteria of the appendix. This causes reflex nausea and vomiting, and the visceral pain increases. As pressure in the organ increases, venous pressure is exceeded. Capillaries and venules are occluded but arterial inflow continues, resulting in engorgement and vascular congestion. The inflammatory process soon involves the serosa of the appendix and in turn the parietal peritoneum. This produces the characteristic shift in pain to the right lower quadrant.
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The mucosa of the appendix is susceptible to impairment of blood supply; thus, its integrity is compromised early in the process, which allows bacterial invasion. The area with the poorest blood supply suffers the most: ellipsoidal infarcts develop in the antimesenteric border. As distension, bacterial invasion, compromise of the vascular supply, and infarction progress, perforation occurs, usually on the antimesenteric border just beyond the point of obstruction. This sequence is not inevitable, however, and some episodes of acute appendicitis may resolve spontaneously.
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Appendicitis may occur in clusters, suggesting an infectious genesis. However, an association with various contagious bacteria and viruses has only been found in a small proportion of appendicitis patients.25 The flora of the inflamed appendix differs from that of the normal appendix. About 60% of aspirates of inflamed appendices have anaerobes compared to 25% of aspirates from normal appendices.26 Tissue specimens from the inflamed appendix wall (not luminal aspirates) virtually all grow Escherichia coli and Bacteroides species on culture.27,28 Fusobacterium nucleatum/necrophorum, which is not present in the normal cecal flora, has been identified in 62% of inflamed appendices.29 In addition to the other usual species (Peptostreptococcus, Pseudomonas, Bacteroides splanchnicus, Bacteroides intermedius, Lactobacillus), previously unreported fastidious gram-negative anaerobic bacilli have been encountered. Patients with gangrene or perforated appendicitis appear to have more tissue invasion by Bacteroides.
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Because of the current predilection for surgical treatment, the natural history of appendicitis has not been well described. An increasing amount of circumstantial evidence suggests that not all patients with appendicitis will progress to perforation and that resolution may be a common event.30 Among the strongest evidence are two randomized trials comparing early laparoscopy with conservative management of patients with acute abdominal pain. These studies found three to five times more patients with appendicitis in the group of patients who were randomized to laparoscopy.31,32 Based on epidemiologic differences, it has been proposed that nonperforated and perforated appendicitis may, in fact, be different diseases.22
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Clinical Presentation
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The inflammatory process in the appendix presents as pain, which initially is of a diffuse visceral type and later becomes more localized as the peritoneal lining gets irritated (Table 30-1).33
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Appendicitis usually starts with periumbilical and diffuse pain that eventually localizes to the right lower quadrant (sensitivity, 81%; specificity, 53%).34 Although right lower quadrant pain is one of the most sensitive signs of appendicitis, pain in an atypical location or minimal pain will often be the initial presentation. Variations in the anatomic location of the appendix may account for the differing presentations of the somatic phase of pain.
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Appendicitis is also associated with gastrointestinal symptoms like nausea (sensitivity, 58%; specificity, 36%), vomiting (sensitivity, 51%; specificity, 45%), and anorexia (sensitivity, 68%; specificity, 36%). Gastrointestinal symptoms that develop before the onset of pain suggest a different etiology such as gastroenteritis.34 Many patients complain of a sensation of obstipation prior to the onset of pain and feel that defecation will relieve their abdominal pain. Diarrhea may occur in association with perforation, especially in children.
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Early in presentation, vital signs may be minimally altered. The body temperature and pulse rate may be normal or slightly elevated. Changes of greater magnitude may indicate that a complication has occurred or that another diagnosis should be considered.35
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Physical findings are determined by the presence of peritoneal irritation and are influenced by whether the organ has already ruptured when the patient is first examined. Patients with appendicitis usually move slowly and prefer to lie supine due to the peritoneal irritation. On abdominal palpation, there is tenderness with a maximum at or near McBurney’s point (Fig. 30-1).5 On deep palpation, one can often feel a muscular resistance (guarding) in the right iliac fossa, which may be more evident when compared to the left side. When the pressure of the examining hand is quickly relieved, the patient feels a sudden pain, the so-called rebound tenderness. Indirect tenderness (Rovsing’s sign) and indirect rebound tenderness (i.e., pain in the right lower quadrant when the left lower quadrant is palpated) are strong indicators of peritoneal irritation. Rebound tenderness can be very sharp and uncomfortable for the patient. It is therefore recommended to start with testing for indirect rebound tenderness and direct percussion tenderness.
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Anatomic variations in the position of the inflamed appendix lead to deviations in the usual physical findings. With a retrocecal appendix, the abdominal findings are less striking, and tenderness may be most marked in the flank. When the appendix hangs into the pelvis, abdominal findings may be entirely absent, and the diagnosis may be missed. Right-sided rectal tenderness is said to help in this situation, but the diagnostic value is low. Pain with extension of the right leg (psoas sign) indicates a focus of irritation in the proximity of the right psoas muscle. Similarly, stretching of the obturator internus through internal rotation of a flexed thigh (obturator sign) suggests inflammation near the muscle.
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Appendicitis is associated with an inflammatory response that is strongly related to the severity of the disease. Laboratory examinations are therefore an important part of the diagnosis. Mild leukocytosis is often present in patients with acute, uncomplicated appendicitis and is usually accompanied by a polymorphonuclear prominence. It is unusual for the white blood cell count to be >18,000 cells/mm3 in uncomplicated appendicitis. Counts above this level raise the possibility of a perforated appendix with or without an abscess. An increased C-reactive protein (CRP) concentration is a strong indicator of appendicitis, especially for complicated appendicitis.36
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White blood cell counts can be low due to lymphopenia or septic reaction, but in this situation, the proportion of neutrophils is usually very high. Therefore, all inflammatory variables should be viewed together. Appendicitis is very unlikely if the white blood cell count, proportion of neutrophils, and CRP are all normal. The inflammatory response in acute appendicitis is a dynamic process. Early in the process, the inflammatory response can be weak. CRP elevation, in particular, can have up to a 12-hour delay. A decreasing inflammatory response may indicate spontaneous resolution.
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Urinalysis can be useful to rule out the urinary tract as the source of infection; however, several white or red blood cells can be present from irritation of the ureter or bladder. Bacteriuria is generally not seen.
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Clinical Scoring Systems
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The clinical diagnosis of appendicitis is a subjective estimate of the probability of appendicitis based on multiple variables that individually are weak discriminators; however, used in conjunction, they possess a high predictive value. This process can be made more objective by the use of clinical scoring systems, which are based on variables with proven discriminating power and assigned a proper weight. The Alvarado score is the most widespread scoring system. It is especially useful for ruling out appendicitis and selecting patients for further diagnostic workup.37 The Appendicitis Inflammatory Response Score resembles the Alvarado score but uses more graded variables and includes CRP (Table 30-2).38,39 Studies have shown it to perform better than the Alvarado score in accurately predicting appendicitis.38,39 However, clinical scoring systems have not gained widespread acceptance in making the diagnosis of appendicitis.
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Plain films of the abdomen can show the presence of a fecalith and fecal loading in the cecum associated with appendicitis but are rarely helpful in diagnosing acute appendicitis40; however, they may be of benefit in ruling out other pathology. A chest radiograph is helpful to rule out referred pain from a right lower lobe pneumonic process. If the appendix fills on barium enema, appendicitis is unlikely41; however, this test is not indicated in the acute setting. Technetium-99m–labeled leukocyte scan has been reported for use in diagnosing appendicitis with good results but has not gained widespread use due to its relative unavailability and impracticality in daily use.42
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Ultrasonography and computed tomography (CT) scan are the most commonly used imaging tests in patients with abdominal pain, particularly in evaluation of possible appendicitis. Multiple meta-analyses have been performed comparing the two imaging modalities (Table 30-3).43,44,45,46,47 Overall, CT scan is more sensitive and specific than ultrasonography in diagnosing appendicitis.
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Graded compression ultrasonography is inexpensive, can be performed rapidly, does not require a contrast medium, and can be used in pregnant patients. Sonographically, the appendix is identified as a blind-ending, nonperistaltic bowel loop originating from the cecum. With maximal compression, the diameter of the appendix is measured in the anterior-posterior direction. Thickening of the appendiceal wall and the presence of periappendiceal fluid are highly suggestive of appendicitis. Demonstration of an easily compressible appendix measuring <5 mm in diameter excludes the diagnosis of appendicitis. The sonographic diagnosis of acute appendicitis has a reported sensitivity of 55% to 96% and a specificity of 85% to 98%. Ultrasonography is similarly effective in children and pregnant women, although its application is limited in late pregnancy. Ultrasonography has its limitations, particularly the operator-dependent nature of results. In the adult population, ultrasonography remains limited in its use.
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With high-resolution helical CT, the inflamed appendix appears dilated (>5 mm), and the wall is thickened. There is often evidence of inflammation, which can include periappendiceal fat stranding, thickened mesoappendix, periappendiceal phlegmon, and free fluid. Fecaliths can be often visualized; however, their presence is not pathognomonic of appendicitis. CT scanning is also an excellent technique for identifying other inflammatory processes masquerading as appendicitis. Several CT techniques have been used, including focused and nonfocused CT scans and contrast and noncontrast scans. Surprisingly, all of these techniques have yielded essentially identical rates of diagnostic accuracy: 92% to 97% sensitivity, 85% to 94% specificity, 90% to 98% accuracy, 75% to 95% positive predictive value, and 95% to 99% negative predictive value. The additional use of rectal contrast does not improve the results of CT scanning.
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A number of studies have documented improvement in diagnostic accuracy with the liberal use of CT scanning in the workup of suspected appendicitis. CT lowered the rate of negative appendectomies from 19% to 12% in one study48 and the incidence of negative appendectomies in women from 24% to 5% in another study.49 Use of CT altered the care of 24% of patients studied and provided an alternative diagnosis in half of the patients with normal appendices on CT scan.
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Despite the potential usefulness of CT, there are significant disadvantages. CT scanning is expensive, exposes the patient to significant radiation, and has limited use during pregnancy. Allergy to iodine or contrast limits the administration of contrast agents in some patients, and others cannot tolerate the oral ingestion of luminal dye.
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The role of CT scanning in patients who present with right lower quadrant pain is unclear. One rationale is universal CT scanning. There is, however, an argument that indiscriminate diagnostic imaging can increase the detection of clinically nonsignificant appendicitis that would resolve without treatment. Alternatively, selective CT scanning based on the likelihood of appendicitis takes advantage of the clinical skills of the surgeon and, when indicated, adds the expertise of the radiologist.
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Despite the increased use of ultrasonography and CT, the rate of misdiagnosis of appendicitis has remained constant (15%). The percentage of misdiagnosed cases of appendicitis is significantly higher among women than men (22% vs. 9.3%).50,51 The negative appendectomy rate is highest in women of reproductive age.
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Differential Diagnosis
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The differential diagnosis of acute appendicitis is essentially the diagnosis of acute abdomen. An identical clinical picture can result from a wide variety of acute processes within the peritoneal cavity that produce the same physiologic alterations as acute appendicitis.
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The accuracy of preoperative diagnosis should be higher than 85%. If it is consistently less, it is likely that unnecessary operations are being performed and a more rigorous preoperative differential diagnosis is needed.
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The most common findings in the case of an erroneous preoperative diagnosis of appendicitis—together accounting for more than 75% of cases—are, in descending order of frequency, acute mesenteric adenitis, no organic pathologic condition, acute pelvic inflammatory disease, twisted ovarian cyst or ruptured graafian follicle, and acute gastroenteritis.
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The differential diagnosis of acute appendicitis depends on four major factors: the anatomic location of the inflamed appendix; the stage of the process (uncomplicated or complicated); the patient’s age; and the patient’s gender.52,53,54,55,56
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Acute mesenteric adenitis is the disease most often confused with acute appendicitis in children. Almost invariably, an upper respiratory tract infection is present or has recently subsided. The pain usually is diffuse, and tenderness is not as sharply localized as in appendicitis. Voluntary guarding is sometimes present, but true rigidity is rare. Generalized lymphadenopathy may be noted. Laboratory procedures are of little help in arriving at the correct diagnosis, although a relative lymphocytosis, when present, suggests mesenteric adenitis. Observation for several hours is appropriate if the diagnosis of mesenteric adenitis is suspected, as it is a self-limited disease.
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Diverticulitis or perforating carcinoma of the cecum or of a portion of the sigmoid that overlies the right lower abdomen may be impossible to distinguish from appendicitis. These entities should be considered, particularly in older patients. CT scanning is often helpful in making a diagnosis in older patients with right lower quadrant pain and atypical clinical presentations. In patients successfully managed conservatively, interval surveillance of the colon (colonoscopy or barium enema) may be warranted.
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Diseases of the female internal reproductive organs that may erroneously be diagnosed as appendicitis are, in approximate descending order of frequency, pelvic inflammatory disease, ruptured graafian follicle, twisted ovarian cyst or tumor, endometriosis, and ruptured ectopic pregnancy. As a result, the rate of misdiagnosis remains higher among female patients.
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In pelvic inflammatory disease, the infection is usually bilateral but, if confined to the right tube, may mimic acute appendicitis. Nausea and vomiting are present in patients with appendicitis but in only approximately 50% of those with pelvic inflammatory disease. Pain and tenderness are usually lower, and motion of the cervix is exquisitely painful. Intracellular diplococci may be demonstrable on smear of the purulent vaginal discharge. The ratio of cases of appendicitis to cases of pelvic inflammatory disease is low in females in the early phase of the menstrual cycle and high during the luteal phase. The careful clinical use of these features has reduced the incidence of negative findings on laparoscopy in young women to 15%.
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Ovulation commonly results in the spillage of sufficient amounts of blood and follicular fluid to produce brief, mild lower abdominal pain. If the amount of fluid is unusually copious and is from the right ovary, appendicitis may be simulated. Pain and tenderness may be rather diffuse, and leukocytosis and fever minimal or absent. Because this pain occurs at the midpoint of the menstrual cycle, it is often called mittelschmerz.
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Serous cysts of the ovary are common and generally remain asymptomatic. When right-sided cysts rupture or undergo torsion, the manifestations are similar to those of appendicitis. Patients develop right lower quadrant pain, tenderness, rebound, fever, and leukocytosis. Both transvaginal ultrasonography and CT scanning can be diagnostic.
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Torsion requires emergent operative treatment. If the torsion is complete or longstanding, the pedicle undergoes thrombosis, and the ovary and tube become gangrenous and require resection. However, simple detorsion, fenestration of the cyst, and fixation of the ovary as a primary intervention, followed by a laparoscopy a few days later, can be recommended because it is often difficult to preoperatively determine the viability of the ovary.
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Blastocysts may implant in the fallopian tube (usually the ampullary portion) and in the ovary. Rupture of right tubal or ovarian pregnancies can mimic appendicitis. Patients may give a history of abnormal menses, either missing one or two periods or noting only slight vaginal bleeding. Unfortunately, patients do not always realize they are pregnant. The development of right lower quadrant or pelvic pain may be the first symptom. The diagnosis of ruptured ectopic pregnancy should be relatively easy. The presence of a pelvic mass and elevated levels of human chorionic gonadotropin are characteristic. Although the leukocyte count rises slightly, the hematocrit level falls as a consequence of the intra-abdominal hemorrhage. Vaginal examination reveals cervical motion and adnexal tenderness, and a more definitive diagnosis can be established by culdocentesis. The presence of blood and particularly decidual tissue is pathognomonic. The treatment of ruptured ectopic pregnancy is emergency surgery.
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Immunosuppressed Patient
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The incidence of acute appendicitis in patients infected with human immunodeficiency virus (HIV) is reported to be 0.5%. This is higher than the 0.1% to 0.2% incidence reported for the general population.57 The presentation of acute appendicitis in HIV-infected patients is similar to that in noninfected patients. The majority of HIV-infected patients with appendicitis have fever, periumbilical pain radiating to the right lower quadrant (91%), right lower quadrant tenderness (91%), and rebound tenderness (74%). HIV-infected patients do not manifest an absolute leukocytosis; however, if a baseline leukocyte count is available, nearly all HIV-infected patients with appendicitis demonstrate a relative leukocytosis.57
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The risk of appendiceal rupture appears to be increased in HIV-infected patients. In one large series of HIV-infected patients who underwent appendectomy for presumed appendicitis, 43% of patients were found to have perforated appendicitis at laparotomy.58 The increased risk of appendiceal rupture may be related to the delay in presentation seen in this patient population.57,58 A low CD4 count is also associated with an increased incidence of appendiceal rupture.57
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The differential diagnosis of right lower quadrant pain is expanded in HIV-infected patients compared with the general population. In addition to the conditions discussed elsewhere in this chapter, opportunistic infections should be considered as a possible cause of right lower quadrant pain.57,58 Neutropenic enterocolitis (typhlitis) should also be considered in the differential diagnosis of right lower quadrant pain in HIV-infected patients.57,58
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Uncomplicated Appendicitis
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Operative versus Nonoperative Management of Uncomplicated Appendicitis
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In patients with uncomplicated appendicitis, surgical treatment has been the standard of treatment since McBurney reported his experiences. The concept of nonoperative treatment for uncomplicated appendicitis developed from two lines of observations. First, for patients in an environment where surgical treatment is not available (e.g., submarines, expeditions in remote areas), treatment with antibiotics alone was noted to be effective. Second, many patients with signs and symptoms consistent with appendicitis who did not pursue medical treatment would occasionally have spontaneous resolution of their illness.
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A handful of observational studies and controlled trials have reported the outcomes of nonoperative versus operative treatment of presumed uncomplicated appendicitis (Table 30-4).59,60,61,62,63,64 Overall, there is a reported 9% short-term (<30 days) failure rate with nonoperative management of appendicitis (13% if evaluated per protocol). In patients in whom nonoperative treatment fails, nearly half of patients have complicated (perforated or gangrenous) appendicitis. After 1 month, about 1% of patients in the trials underwent an interval appendectomy, and 13% of patients who initially were successfully treated with nonoperative measures developed recurrent appendicitis, with an 18% rate of complicated appendicitis. Follow-up was not longer than 1 year in any study. In addition, one-third of patients declined or dropped out from nonoperative management of appendicitis.
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In comparison, operative appendectomy demonstrated a relatively low dropout rate (2%), lower proportion of complicated appendicitis (25%), small proportion of a normal appendix (5%), and low rates of superficial surgical site infection (3.7%) and intra-abdominal abscess (1.3%).
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The results in these studies must viewed with caution due to unclear selection of patients, incomplete diagnostic workup in the nonoperated patients, unclear gold standard for the operated patients, and high rates of crossover between the treatment arms. The consequences in terms of use of hospital beds, length of hospital stay, morbidity of delayed surgical treatment after failed nonsurgical treatment, delayed diagnosis for patients with an underlying cancer in the appendix or cecum, and risk of increased antibiotic resistance need to be further investigated. Thus, operative treatment of presumed uncomplicated appendicitis still remains the standard of care. Certain subgroups with uncomplicated appendicitis may do well with nonoperative therapy. Patients pursuing nonoperative management should be carefully counseled regarding the risks of treatment failure and recurrent appendicitis.
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Urgent versus Emergent Appendectomy for Uncomplicated Appendicitis
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Traditionally, appendicitis has been considered a surgical emergency. Once diagnosed, a patient was emergently taken to the operating room for surgical treatment. However, delays in diagnosis, lack of access to available operating suites, and nonoperative management of appendicitis have challenged the notion that uncomplicated appendicitis is a surgical emergency.
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Three retrospective studies have evaluated the role of emergent or urgent surgery for uncomplicated appendicitis; the emergent group had a time from presentation to the operating room of <12 hours, whereas the urgent group had a time from presentation to the operating room of 12 to 24 hours (Table 30-5).65,66,67 There was no statistically significant increase in the number of complicated appendicitis cases in the urgent group when compared to the emergent group. Similarly, rates of surgical site infection, intra-abdominal abscesses, conversion to an open procedure, or operative time showed no difference between the two groups. While length of stay was longer for the urgent group, it was not statistically or clinically different from the emergent group. Important caveats in consideration of urgent as opposed to emergent surgical care include the patient’s clinical examination, time of presentation from onset of symptoms, and duration of “delay” in surgery. Patients with clinical signs of perforation, patients with delayed presentation of greater than 48 hours from onset of symptoms, and patients whose definitive therapy may be delayed for more than 12 hours were beyond the scope of these studies.
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Emergent versus urgent operation for uncomplicated appendicitis is dependent on each institution and surgeon. Institutions without readily available operating rooms and staff may consider performing appendectomy in an urgent fashion as opposed to emergently.
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Complicated Appendicitis
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Complicated appendicitis typically refers to perforated appendicitis commonly associated with an abscess or phlegmon. The yearly incidence rate of perforated appendicitis is about 2 per 10,000 persons and has remarkable little variance over time, geographic region, and age.51,68,69 The proportion of perforated appendicitis, commonly around 25%, is often used as an indicator of quality of care. Differences in this proportion are almost entirely related to differences in the incidence of nonperforated appendicitis. A low proportion of perforations may therefore be the consequence of a higher rate of detection and treatment of early or resolving appendicitis.
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Children less than 5 years of age and patients more than 65 years of age have the highest rates of perforation (45% and 51%, respectively). The proportion of perforation increases with increasing duration of symptoms. There is, however, no association of in-hospital delay with perforation. This suggests that most perforations occur early, before the patient arrives to hospital. It has also been proposed that the increasing proportion of perforations with time is explained by selection due to spontaneous resolution of noncomplicated appendicitis.
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Perforated appendicitis has been suggested to increase the risk of female infertility due to impaired tubal function, but this has not been shown in epidemiologic studies.70
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Rupture should be suspected in the presence of generalized peritonitis and a strong inflammatory response. In many cases, rupture is contained and patients display localized peritonitis. In 2% to 6% of cases, a palpable mass is detected on physical examination. This could represent a phlegmon, which consists of matted loops of bowel adherent to the adjacent inflamed appendix or a periappendiceal abscess. Patients who present with a mass have experienced symptoms for a longer duration, usually 5 to 7 days. Distinguishing acute, uncomplicated appendicitis from acute appendicitis with perforation based on clinical findings is often difficult, but it is important to make the distinction because the treatments may differ. CT scan may be beneficial in establishing a diagnosis and guiding therapy.
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Operative versus Nonoperative Management of Complicated Appendicitis
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Patients who present with signs of sepsis and generalized peritonitis should be taken to the operating room immediately with concurrent resuscitation. The surgical approach is based on the surgeon’s level of comfort; however, open appendectomy through a lower midline incision may be necessary to treat these complicated cases.
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In patients with complicated appendicits and a contained abscess or phlegmon but limited peritonitis (focal right lower quadrant pain), the treatment options become more complicated. Often, these patients will require a challenging procedure with a high risk for development of a postoperative intra-abdominal abscess. Options include operative management versus conservative management (antibiotics, bowel rest, fluids, and possible percutaneous drainage).
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There have been no prospective randomized controlled studies comparing operative versus conservative management of complicated appendicitis in adults; all studies have been retrospective cohort studies. Two meta-analyses have been performed. In Andersson and Petzold’s 2007 analysis of 61 studies evaluating this issue, they noted that initial nonoperative management had superior outcomes.70 Nonoperative management included intravenous fluids, minimizing gastrointestinal stimulation, parenteral antibiotics, and percutaneous drainage where deemed appropriate. The morbidity of immediate operative treatment was 36.5%, whereas the morbidity of conservative management was 11%. Of patients undergoing conservative treatment, 7.6% failed conservative treatment and underwent operative management. This subgroup had an overall complication rate of 13.5%. The recurrence rate was 7.4%, which does not necessitate interval appendectomy. The authors concluded that conservative treatment was favored over early operation in complicated appendicitis.30
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Simillis and colleagues performed a meta-analysis of 17 studies.71 They noted that conservative treatment was associated with fewer overall complications (odds ratio, 0.24; 95% confidence interval [CI], 0.13 to 0.44), intra-abdominal abscesses (odds ratio, 0.19; 95% CI, 0.07 to 0.58), bowel obstructions (odds ratio, 0.35; 95% CI, 0.17 to 0.71), and reoperations (odds ratio, 0.17; 95% CI, 0.04 to 0.75).71 The authors concluded that conservative treatment was favored over early operation in complicated appendicitis.
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In the pediatric literature, there have been two prospective randomized controlled trials72,73 demonstrating that early operative intervention had equivalent or superior outcomes to conservative management, but these studies included interval appendectomy for all patients in their calculations. St. Peter and colleagues72 demonstrated that 20% of patients failed conservative treatment. Early surgical intervention had equivalent results to interval appendectomy. Alternatively, Blakely and colleagues73 noted that interval appendectomy, versus early appendectomy, had a higher incidence of adverse events (50% vs. 30%, P = .003), intra-abdominal abscesses (37% vs. 19%, P = .02), small bowel obstruction (10.4% vs. 0%, P = .01), and readmissions (31% vs. 8%, P = .06). In addition, Blakely and colleagues noted that 9% of the group treated conservatively developed recurrent appendicitis. The authors concluded that immediate surgical treatment was superior to conservative treatment with interval appendectomy.
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Interval Appendectomy Following Nonoperative Management of Complicated Appendicitis
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Interval appendectomy is defined as performing an appendectomy following initial successful nonoperative management in patients with no further symptoms. The major argument against interval appendectomy is that many patients treated conservatively never develop manifestations of appendicitis, and those who do generally can be treated without additional morbidity. The major argument for interval appendectomy is to prevent future attacks of appendicitis or to identify other disease, such as appendiceal malignancy.
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There has only been one small prospective randomized controlled trial (n = 40) investigating this subject. The literature is largely populated with small case series and retrospective cohort studies; there is no meta-analysis evaluating the subject (Table 30-6).74,75,76,77,78,79,80,81 Of the 1434 patients who had presumed complicated appendicitis and were successfully treated conservatively, 8.8% developed recurrent appendicitis with a median follow-up of 35 months. The incidence of complicated appendicitis following recurrence was low (2.4%). Malignancy was noted in 1.3% of cases where pathology was reported. Many of the patients were excluded from these studies due to persistent symptoms, persistent infections, or note of malignancy on screening colonoscopy.
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Alternatively, of the 344 patients who had presumed complicated appendicitis, were successfully treated conservatively, and subsequently underwent interval appendectomy, surgical complications occurred in 9.4% of the patients. Most patients underwent interval appendectomy 2 to 4 months after their acute presentation. Although operative and pathologic details were not uniformly reported in these patients, many continued to have evidence of appendicitis or abscess at the time of interval appendectomy; 3.6% of patients had malignancy in cases where pathology was reported.
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The role of interval appendectomy following successful management of conservative treatment of complicated appendicitis is unclear. Close clinical follow-up, a complete history searching for persistent symptoms, and screening colonoscopy (when age appropriate) should all be used to help guide the discussion with the patient on the role of interval appendectomy following conservative management of complicated appendicitis.