Am J Epidemiol. 1990 Nov;132(5):910-25.
The epidemiology of appendicitis and appendectomy in the United States.
Source
Division of Bacterial Diseases, Center for Infectious Diseases, Centers for Disease Control, Atlanta, GA 30333.Abstract
To describe the epidemiology of appendicitis and appendectomy in the United States, the authors analyzed National Hospital Discharge Survey data for the years 1979-1984. Approximately 250,000 cases of appendicitis occurred annually in the United States during this period, accounting for an estimated 1 million hospital days per year. The highest incidence of primary positive appendectomy (appendicitis) was found in persons aged 10-19 years (23.3 per 10,000 population per year); males had higher rates of appendicitis than females for all age groups (overall rate ratio, 1.4:1). Racial, geographic, and seasonal differences were also noted. Appendicitis rates were 1.5 times higher for whites than for nonwhites, highest (15.4 per 10,000 population per year) in the west north central region, and 11.3% higher in the summer than in the winter months. The highest rate of incidental appendectomy was found in women aged 35-44 years (43.8 per 10,000 population per year), 12.1 times higher than the rate for men of the same age. Between 1970 and 1984, the incidence of appendicitis decreased by 14.6%; reasons for this decline are unknown. A life table model suggests that the lifetime risk of appendicitis is 8.6% for males and 6.7% for females; the lifetime risk of appendectomy is 12.0% for males and 23.1% for females. Overall, an estimated 36 incidental procedures are performed to prevent one case of appendicitis; for the elderly, the preventive value of an incidental procedure is considerably lower.Epidemiology
Addiss and associates estimated the incidence of acute appendicitis in the United States population to be 11 cases per 10,000 population annually. The disease is slightly more common in males, with a male:female ratio of 1.4:1. In a lifetime, 8.6% of males and 6.7% of females can be expected to develop acute appendicitis. Young age is a risk factor, as nearly 70% of patients with acute appendicitis are less than 30 years of age. The highest incidence of appendicitis in males is in the 10- to 14-year-old age group (27.6 cases per 10,000 population), while the highest female incidence is in the 15- to 19-year-old age group (20.5 cases per 10,000 population). Patients at extremes of age are more likely to develop perforated appendicitis. Overall, perforation was present in 19.2% of cases of acute appendicitis. This number was significantly higher, however, in patients under 5 and over 65 years of age. Although less common in people over 65 years old, acute appendicitis in the elderly progresses to perforation more than 50% of the time.
Etiology and Pathophysiology
Appendicitis, diverticular disease, and colorectal carcinoma have been shown to be diseases of developed civilizations. Burkitt found an increased incidence of appendicitis in Western countries compared to Africa, as well as in wealthy, urban communities compared to rural areas. He attributed this to the Western diet, which is low in dietary fiber and high in refined sugars and fat, and postulated that low-fiber diets lead to less bulky bowel contents, prolonged intestinal transit time, and increased intraluminal pressure. Burkitt theorized that the combination of firm stool leading to appendiceal obstruction and increased intraluminal pressure causing bacterial translocation across the bowel wall resulted in appendicitis. In examining appendixes removed for reasons other than appendicitis, he found fecaliths to be more prevalent in Canadian (32%) than in South African (4%) adults. In a group of patients with appendicitis, fecaliths were more common in Canadians (52%) than in South Africans (23%).He felt this was confirmation that appendiceal obstruction resulted in appendicitis. Of note, however, the majority of patients with appendicitis in his study did not have evidence of a fecalith.
Wangensteen extensively studied the structure and function of the appendix and the role of obstruction in appendicitis.Based on anatomic studies, he postulated that mucosal folds and a sphincterlike orientation of muscle fibers at the appendiceal orifice make the appendix susceptible to obstruction. He proposed the following sequence of events to explain appendicitis:
(1) closed loop obstruction is caused by a fecalith and swelling of the mucosal and submucosal lymphoid tissue at the base of the appendix;
(2) intraluminal pressure rises as the appendiceal mucosa secretes fluid against the fixed obstruction;
(3) increased pressure in the appendiceal wall exceeds capillary pressure and causes mucosal ischemia; and
(4) luminal bacterial overgrowth and translocation of bacteria across the appendiceal wall result in inflammation, edema, and ultimately necrosis. If the appendix is not removed, perforation can ensue.
Although appendiceal obstruction is widely accepted as the primary cause of appendicitis, evidence suggests that this may be only one of many possible etiologies. First, some patients with a fecalith have a histologically normal appendix.Moreover, the majority of patients with appendicitis show no evidence for a fecalith.Arnbjornsson and Bengmark studied at laparotomy the appendixes of patients with suspected appendicitis. They found the intraluminal pressure of the appendix prior to removal to be elevated in only 8 of 27 patients with nonperforated appendicitis. They found no signs of obstruction in the remaining patients with nonperforated appendicitis, as well as all patients with a normal appendix. Taken together, these studies imply that obstruction is but one of the possible etiologies of acute appendicitis.
If open appendectomy is chosen for treat appendicitis, the surgeon must then decide on the location and type of incision. Prior to incision, a single dose of antibiotics should be administered, typically a second-generation cephalosporin.The appendicitis patient should be re-examined after the induction of general anesthesia, which enables deep palpation of the abdomen. If a mass representing the inflamed appendix can be palpated, the incision can be centered at that location. If no appendiceal mass is detected, the incision should be centered over McBurney’s point, one-third of the distance from the anterior superior iliac spine to the umbilicus. A curvilinear incision, now known as a McBurney’s incision, is made in a natural skin fold. It is important not to make the incision too medial or too lateral. An incision placed too medial opens onto the anterior rectus sheath, rather than the desired oblique muscles, while an incision placed too lateral may be lateral to the abdominal cavity.
The operation proceeds much as McBurney first described it in 1894 in treatment of appendicitis. The incision is carried down through the subcutaneous tissue, exposing the aponeurosis of the external oblique muscle, which is divided, either sharply or with electrocautery, in the direction of its fibers . A muscle-splitting technique is typically used, in which the external oblique, internal oblique, and transversus abdominis muscles are separated along the orientation of their muscle fibers. The peritoneum is thus exposed, grasped with forceps, and opened sharply along the orientation of the incision, taking care not to injure the underlying abdominal contents. Hemostats can be placed on the peritoneum to facilitate its identification at the time of wound closure. Cloudy fluid may be encountered on entering the peritoneum. Although some advocate bacterial culture of the peritoneal fluid, studies show that this neither helps direct the antibiotic regimen nor reduces infectious complications.
With a correctly placed incision, the cecum will be visible at the base of the wound. The incision should be explored with a finger in an attempt to locate the appendix. If the appendix is palpable and free from surrounding structures, it can be delivered into the incision. Frequently, the appendix is palpable but it adheres to surrounding structures. Filmy adhesions can be divided using blunt dissection, but thicker adhesions should be divided under direct vision. To facilitate this, the cecum can be partially delivered into the incision to provide better exposure of the appendix. If necessary to improve exposure, the incision can be extended medially by partially dividing the rectus muscle, or laterally by further dividing the oblique and transversus abdominis muscles. If the appendix cannot be visualized, it can be located by following the teniae coli of the cecum to the cecal base, from which the appendix invariably originates. Once located, the appendix is delivered through the incision. Grasping the mesentery with a Babcock clamp can sometimes facilitate this maneuver. Care should be taken to avoid perforation of the appendix, with spillage of pus or enteric contents into the abdomen.
The arterial supply to the appendix, which runs in the mesoappendix, is now divided between clamps and tied with 3-0 polyglactin suture. This is usually performed in an antegrade fashion, from the appendiceal tip toward the base. Division of the artery to the appendiceal base is necessary to ensure that the entire appendix can be removed without leaving an excessively long appendiceal stump.
In excising the appendix, the surgeon must decide whether or not to invert the appendiceal stump. Traditionally, the appendix was ligated and divided, and its stump was inverted with a purse-string suture for the theoretical purpose of avoiding bacterial contamination of the peritoneum and subsequent adhesion formation. However, recent prospective studies show no advantages to appendiceal stump inversion. In one such study, appendectomy patients were randomly assigned to ligation plus inversion or simple ligation of the appendiceal stump. There was no difference between the two groups in the incidence of wound infection or adhesion formation, and operating time was shorter in the simple ligation group. Inversion may also have the deleterious effect of deforming the cecal wall, which could be misinterpreted as a cecal mass on future contrast radiographs. Furthermore, the long-standing notion that stump inversion reduces postoperative adhesions was discredited by Street and colleagues.In their analysis, postoperative adhesions requiring operation were significantly increased in the inversion group.
To divide the appendix, the surgeon can use either suture ligation or a gastrointestinal stapler. For ligation, two hemostat clamps are placed at the base of the appendix. The clamp closest to the cecum is removed, having crushed the appendix at that site. Two heavy, absorbable sutures such as 0 chromic gut is used to doubly ligate the appendix, and the appendix is subsequently divided proximal to the second clamp. The exposed mucosa of the appendiceal stump can be cauterized to minimize the theoretical risk of postoperative mucocele, although no data exist to support this. If appendiceal stump inversion is chosen, a seromuscular purse-string 3-0 silk suture is placed in the cecum around the appendiceal base after ligation but prior to division of the appendix. The purse-string suture should be placed approximately 1 cm from the base of the appendix, as placing it too close to the appendix makes stump inversion difficult. After the appendix is divided, the purse-string suture is tightened and tied while the assistant uses forceps to invaginate the appendiceal stump. Alternatively, the appendix can be divided at its base using a TA-30 stapler. Again, the stump need not be inverted, but can be if desired, using interrupted Lembert sutures with 3-0 silk suture. No matter how the appendix is divided, the residual appendiceal stump should be no longer than 3 mm to minimize the possibility of stump appendicitis in the future.
Occasionally, inflammation at the tip of the appendix makes antegrade removal of the appendix difficult. In such cases, the appendix can be removed in a retrograde fashion. In so doing, the appendix is divided at its base using one of the methods described previously. The mesoappendix is then divided between clamps, starting at the appendiceal base and progressing toward the tip
In certain cases, the appendiceal inflammation extends to the base of the appendix or beyond to the cecum. Division of the appendix through inflamed, infected tissue leaves the potential for leakage of cecal contents with a resultant abscess or fistula. Ensuring that the resection margin is grossly free of active inflammation can minimize this risk. If the base of the cecum is also inflamed but there is sufficient uninflamed cecum between the appendix and the ileocecal valve, an appendectomy with partial cecectomy can be performed using a stapling device.Care should be taken to avoid narrowing the cecum at the ileocecal valve. If the inflammation extends to the ileocecal junction, an ileocectomy with primary anastomosis may be necessary.
After the appendix is removed, hemostasis is achieved and the right lower quadrant and pelvis are irrigated with warm saline. The peritoneum is closed with a continuous 0 absorbable suture; this layer provides no strength but helps to contain the abdominal contents during abdominal wall closure. The internal and external oblique muscles are then closed in succession using continuous 0 absorbable suture. To decrease postoperative narcotic requirements, the external oblique fascia can be infused with local anesthetic. Interrupted absorbable sutures are typically placed in Scarpa’s fascia, and the skin can be closed with a subcuticular absorbable suture. With a preoperative dose of intravenous antibiotics and primary closure of the skin, fewer than 5% of patients with nonperforated appendicitis can be expected to develop a wound infection.
Addiss and associates estimated the incidence of acute appendicitis in the United States population to be 11 cases per 10,000 population annually. The disease is slightly more common in males, with a male:female ratio of 1.4:1. In a lifetime, 8.6% of males and 6.7% of females can be expected to develop acute appendicitis. Young age is a risk factor, as nearly 70% of patients with acute appendicitis are less than 30 years of age. The highest incidence of appendicitis in males is in the 10- to 14-year-old age group (27.6 cases per 10,000 population), while the highest female incidence is in the 15- to 19-year-old age group (20.5 cases per 10,000 population). Patients at extremes of age are more likely to develop perforated appendicitis. Overall, perforation was present in 19.2% of cases of acute appendicitis. This number was significantly higher, however, in patients under 5 and over 65 years of age. Although less common in people over 65 years old, acute appendicitis in the elderly progresses to perforation more than 50% of the time.Etiology and Pathophysiology
Appendicitis, diverticular disease, and colorectal carcinoma have been shown to be diseases of developed civilizations. Burkitt found an increased incidence of appendicitis in Western countries compared to Africa, as well as in wealthy, urban communities compared to rural areas. He attributed this to the Western diet, which is low in dietary fiber and high in refined sugars and fat, and postulated that low-fiber diets lead to less bulky bowel contents, prolonged intestinal transit time, and increased intraluminal pressure. Burkitt theorized that the combination of firm stool leading to appendiceal obstruction and increased intraluminal pressure causing bacterial translocation across the bowel wall resulted in appendicitis. In examining appendixes removed for reasons other than appendicitis, he found fecaliths to be more prevalent in Canadian (32%) than in South African (4%) adults. In a group of patients with appendicitis, fecaliths were more common in Canadians (52%) than in South Africans (23%).He felt this was confirmation that appendiceal obstruction resulted in appendicitis. Of note, however, the majority of patients with appendicitis in his study did not have evidence of a fecalith.
Wangensteen extensively studied the structure and function of the appendix and the role of obstruction in appendicitis.Based on anatomic studies, he postulated that mucosal folds and a sphincterlike orientation of muscle fibers at the appendiceal orifice make the appendix susceptible to obstruction. He proposed the following sequence of events to explain appendicitis:
(1) closed loop obstruction is caused by a fecalith and swelling of the mucosal and submucosal lymphoid tissue at the base of the appendix;
(2) intraluminal pressure rises as the appendiceal mucosa secretes fluid against the fixed obstruction;
(3) increased pressure in the appendiceal wall exceeds capillary pressure and causes mucosal ischemia; and
(4) luminal bacterial overgrowth and translocation of bacteria across the appendiceal wall result in inflammation, edema, and ultimately necrosis. If the appendix is not removed, perforation can ensue.
Although appendiceal obstruction is widely accepted as the primary cause of appendicitis, evidence suggests that this may be only one of many possible etiologies. First, some patients with a fecalith have a histologically normal appendix.Moreover, the majority of patients with appendicitis show no evidence for a fecalith.Arnbjornsson and Bengmark studied at laparotomy the appendixes of patients with suspected appendicitis. They found the intraluminal pressure of the appendix prior to removal to be elevated in only 8 of 27 patients with nonperforated appendicitis. They found no signs of obstruction in the remaining patients with nonperforated appendicitis, as well as all patients with a normal appendix. Taken together, these studies imply that obstruction is but one of the possible etiologies of acute appendicitis.
Open Appendectomy for Appendicitis
If open appendectomy is chosen for treat appendicitis, the surgeon must then decide on the location and type of incision. Prior to incision, a single dose of antibiotics should be administered, typically a second-generation cephalosporin.The appendicitis patient should be re-examined after the induction of general anesthesia, which enables deep palpation of the abdomen. If a mass representing the inflamed appendix can be palpated, the incision can be centered at that location. If no appendiceal mass is detected, the incision should be centered over McBurney’s point, one-third of the distance from the anterior superior iliac spine to the umbilicus. A curvilinear incision, now known as a McBurney’s incision, is made in a natural skin fold. It is important not to make the incision too medial or too lateral. An incision placed too medial opens onto the anterior rectus sheath, rather than the desired oblique muscles, while an incision placed too lateral may be lateral to the abdominal cavity.The operation proceeds much as McBurney first described it in 1894 in treatment of appendicitis. The incision is carried down through the subcutaneous tissue, exposing the aponeurosis of the external oblique muscle, which is divided, either sharply or with electrocautery, in the direction of its fibers . A muscle-splitting technique is typically used, in which the external oblique, internal oblique, and transversus abdominis muscles are separated along the orientation of their muscle fibers. The peritoneum is thus exposed, grasped with forceps, and opened sharply along the orientation of the incision, taking care not to injure the underlying abdominal contents. Hemostats can be placed on the peritoneum to facilitate its identification at the time of wound closure. Cloudy fluid may be encountered on entering the peritoneum. Although some advocate bacterial culture of the peritoneal fluid, studies show that this neither helps direct the antibiotic regimen nor reduces infectious complications.
With a correctly placed incision, the cecum will be visible at the base of the wound. The incision should be explored with a finger in an attempt to locate the appendix. If the appendix is palpable and free from surrounding structures, it can be delivered into the incision. Frequently, the appendix is palpable but it adheres to surrounding structures. Filmy adhesions can be divided using blunt dissection, but thicker adhesions should be divided under direct vision. To facilitate this, the cecum can be partially delivered into the incision to provide better exposure of the appendix. If necessary to improve exposure, the incision can be extended medially by partially dividing the rectus muscle, or laterally by further dividing the oblique and transversus abdominis muscles. If the appendix cannot be visualized, it can be located by following the teniae coli of the cecum to the cecal base, from which the appendix invariably originates. Once located, the appendix is delivered through the incision. Grasping the mesentery with a Babcock clamp can sometimes facilitate this maneuver. Care should be taken to avoid perforation of the appendix, with spillage of pus or enteric contents into the abdomen.
The arterial supply to the appendix, which runs in the mesoappendix, is now divided between clamps and tied with 3-0 polyglactin suture. This is usually performed in an antegrade fashion, from the appendiceal tip toward the base. Division of the artery to the appendiceal base is necessary to ensure that the entire appendix can be removed without leaving an excessively long appendiceal stump.
In excising the appendix, the surgeon must decide whether or not to invert the appendiceal stump. Traditionally, the appendix was ligated and divided, and its stump was inverted with a purse-string suture for the theoretical purpose of avoiding bacterial contamination of the peritoneum and subsequent adhesion formation. However, recent prospective studies show no advantages to appendiceal stump inversion. In one such study, appendectomy patients were randomly assigned to ligation plus inversion or simple ligation of the appendiceal stump. There was no difference between the two groups in the incidence of wound infection or adhesion formation, and operating time was shorter in the simple ligation group. Inversion may also have the deleterious effect of deforming the cecal wall, which could be misinterpreted as a cecal mass on future contrast radiographs. Furthermore, the long-standing notion that stump inversion reduces postoperative adhesions was discredited by Street and colleagues.In their analysis, postoperative adhesions requiring operation were significantly increased in the inversion group.
To divide the appendix, the surgeon can use either suture ligation or a gastrointestinal stapler. For ligation, two hemostat clamps are placed at the base of the appendix. The clamp closest to the cecum is removed, having crushed the appendix at that site. Two heavy, absorbable sutures such as 0 chromic gut is used to doubly ligate the appendix, and the appendix is subsequently divided proximal to the second clamp. The exposed mucosa of the appendiceal stump can be cauterized to minimize the theoretical risk of postoperative mucocele, although no data exist to support this. If appendiceal stump inversion is chosen, a seromuscular purse-string 3-0 silk suture is placed in the cecum around the appendiceal base after ligation but prior to division of the appendix. The purse-string suture should be placed approximately 1 cm from the base of the appendix, as placing it too close to the appendix makes stump inversion difficult. After the appendix is divided, the purse-string suture is tightened and tied while the assistant uses forceps to invaginate the appendiceal stump. Alternatively, the appendix can be divided at its base using a TA-30 stapler. Again, the stump need not be inverted, but can be if desired, using interrupted Lembert sutures with 3-0 silk suture. No matter how the appendix is divided, the residual appendiceal stump should be no longer than 3 mm to minimize the possibility of stump appendicitis in the future.
Occasionally, inflammation at the tip of the appendix makes antegrade removal of the appendix difficult. In such cases, the appendix can be removed in a retrograde fashion. In so doing, the appendix is divided at its base using one of the methods described previously. The mesoappendix is then divided between clamps, starting at the appendiceal base and progressing toward the tip
In certain cases, the appendiceal inflammation extends to the base of the appendix or beyond to the cecum. Division of the appendix through inflamed, infected tissue leaves the potential for leakage of cecal contents with a resultant abscess or fistula. Ensuring that the resection margin is grossly free of active inflammation can minimize this risk. If the base of the cecum is also inflamed but there is sufficient uninflamed cecum between the appendix and the ileocecal valve, an appendectomy with partial cecectomy can be performed using a stapling device.Care should be taken to avoid narrowing the cecum at the ileocecal valve. If the inflammation extends to the ileocecal junction, an ileocectomy with primary anastomosis may be necessary.
After the appendix is removed, hemostasis is achieved and the right lower quadrant and pelvis are irrigated with warm saline. The peritoneum is closed with a continuous 0 absorbable suture; this layer provides no strength but helps to contain the abdominal contents during abdominal wall closure. The internal and external oblique muscles are then closed in succession using continuous 0 absorbable suture. To decrease postoperative narcotic requirements, the external oblique fascia can be infused with local anesthetic. Interrupted absorbable sutures are typically placed in Scarpa’s fascia, and the skin can be closed with a subcuticular absorbable suture. With a preoperative dose of intravenous antibiotics and primary closure of the skin, fewer than 5% of patients with nonperforated appendicitis can be expected to develop a wound infection.
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