Appendectomy is the most common urgently performed surgical procedure.
Lifetime risk of undergoing appendectomy is between 7% and 12%.
The maximal incidence occurs in the second and third decades of life.
The male:female ratio of approximately 2:1 gradually shifts after age 25 years toward a 1:1 ratio.
A. Appendiceal obstruction
Appendiceal obstruction is the most common initiating event of appendicitis.
Hyperplasia of the submucosal lymphoid follicles of the appendix accounts for approximately 60% of obstructions (most common in teens).
In older adults and children, the fecalith is the most common etiology (35%).
B. Intraluminal pressure
Intraluminal pressure of the obstructed appendiceal lumen increases secondary to continued mucosal secretion and bacterial overgrowth; the appendiceal wall thins, and lymphatic and venous obstruction occurs.
C. Necrosis and perforation
Necrosis and perforation develop when the arterial flow is compromised.
The diagnosis of acute appendicitis is made by clinical evaluation. Although laboratory tests and imaging procedures can be helpful, they are of secondary importance.
A. Clinical presentation
Classic presentation. Appendicitis typically begins with progressive, persistent midabdominal discomfort caused by obstruction and distention of the appendix, stimulating the visceral afferent autonomic nerves (levels T8 to T10). Anorexia and a low-grade fever (<38.5°C) follow. As distention of the appendix increases, venous congestion stimulates intestinal peristalsis, causing a cramping sensation that is soon followed by nausea and vomiting. Symptoms include anorexia (90%), nausea and vomiting (70%), and diarrhea (10%). Once the inflammation extends transmurally to the parietal peritoneum, the somatic pain fibers are stimulated and the pain localizes to the RLQ. Peritoneal irritation is associated with pain on movement, mild fever, and tachycardia. One fourth of patients present with localized pain and no visceral symptoms. The onset of symptoms to time of presentation is usually less than 24 hours for acute appendicitis and averages several hours.
When the appendix is retrocecal or behind the ileum, it may be separated from the anterior abdominal peritoneum, and abdominal localizing signs may be absent. Irritation of adjacent structures can cause diarrhea, urinary frequency, pyuria, or microscopic hematuria depending on location.
When the appendix is located in the pelvis, it may simulate acute gastroenteritis, with diffuse pain, nausea, vomiting, and diarrhea. The diagnosis may be suspected if digital rectal examination produces pain.
Appendicitis is the most common nongynecologic surgical emergency during pregnancy. The incidence of appendicitis during pregnancy is 0.15 to 2.10/1,000 pregnancies (Can Fam Physician 2004;50:355); appendicitis occurs with a slightly lower frequency in the pregnant patient (Int J Epidemiol 2001;30:1281).
Appendicitis must be suspected in any pregnant woman with abdominal pain. The gravid uterus displaces the appendix superiorly and laterally toward the RUQ (Fig. 11-2), thereby complicating diagnosis. Separation of the visceral and parietal peritoneum due to the enlarging uterus limits localization of the pain by decreasing the somatic component of the pain. In addition, nausea and vomiting can be incorrectly attributed to the morning sickness that is common in the first trimester.
Operation is indicated in a pregnant patient as soon as the diagnosis of appendicitis is suspected. A negative laparotomy carries a risk of fetal loss of up to 3%, but fetal demise rates reach 35% in the setting of perforation and diffuse peritonitis.
B. Physical examination
The examination begins by assessing the patient’s abdomen in areas other than the area of suspected tenderness. Location of the appendix is variable. However, the base is usually found at the level of the S1 vertebral body, lateral to the right midclavicular line at McBurney’s point (two thirds of the distance from the umbilicus to the anterosuperior iliac spine). Rovsing’s sign indicates peritoneal irritation. The degree of tenderness to direct right-lower-quadrant tenderness is appreciated. The degree of muscular resistance to palpation (guarding) parallels the severity of the inflammatory process. Cutaneous hyperesthesia is often present, overlying the region of maximal tenderness. Iliopsoas sign implies retrocecal appendicitis. A pelvic appendix may produce a positive obturator sign.
Rectal examination is performed to evaluate the presence of localized tenderness or an inflammatory mass in the pararectal area. It is most useful for atypical presentations suggestive of a pelvic or retrocecal appendix.
In women, a pelvic examination is performed to assess for cervical motion tenderness and adnexal pain or masses.
A palpable mass in the RLQ suggests a periappendiceal abscess or phlegmon.
C. Laboratory evaluation
The following tests should be obtained preoperatively for patients with suspected appendicitis. A serum pregnancy test must be performed in all ovulating women.
Complete blood cell count. A leukocyte count of greater than 10,000 cells/µL, with polymorphonuclear cell predominance (>75%), carries a 77% sensitivity and 63% specificity for appendicitis (Radiology 2004;230:472). The total number of WBCs and the proportion of immature forms increase if there is appendiceal perforation. In older adults, the leukocyte count and differential are normal more frequently than in younger adults. Pregnant women normally have an elevated WBC count that can reach 15,000 to 20,000 as their pregnancy progresses.
Urinalysis is abnormal in 25% to 40% of patients with appendicitis. Pyuria, albuminuria, and hematuria are common. Large quantities of bacteria suggest UTI as the cause of abdominal pain. A urinalysis showing more than 20 WBCs per high-power field or more than 30 RBCs per high-power field suggests UTI. Significant hematuria should prompt consideration of urolithiasis.
Serum electrolytes, blood urea nitrogen, and serum creatinine are obtained to identify and correct electrolyte abnormalities caused by dehydration secondary to vomiting or poor oral intake.
D. Radiologic evaluation
Diagnosis of appendicitis can usually be made without radiologic evaluation. In complex cases, however, the following can be helpful.
X-rays are rarely helpful in diagnosing appendicitis. One study demonstrated an appendicolith on only 1.14% of the x-rays performed on patients with surgically
proven appendicitis. Other suggestive radiologic findings include a distended cecum with adjacent small-bowel air-fluid levels, loss of the right psoas shadow, scoliosis to the right, and gas in the lumen of the appendix. A perforated appendix rarely causes pneumoperitoneum.
Ultrasound is most useful in women of child-bearing age and in children because other causes of abdominal complaints can be demonstrated. Findings associated with acute appendicitis include an appendiceal diameter greater than 6 mm, lack of luminal compressibility, and presence of an appendicolith. An enlarged appendix seen on US has a sensitivity of 86% and specificity of 81% (Radiology 2004;230:472). The perforated appendix is more difficult to diagnose and is characterized by loss of the echogenic submucosa and the presence of loculated periappendiceal or pelvic fluid collection. In women, ovarian pathology may be identified or excluded. The quality and accuracy of US are highly operator dependent.
CT scan, originally recommended only in cases that were clinically complex or diagnostically uncertain, has emerged as the most commonly used radiographic diagnostic test. It is superior to US in diagnosing appendicitis, with a sensitivity of 94% and specificity of 95% (Ann Intern Med 2004;141:537). CT findings of appendicitis include a distended, thick-walled appendix with inflammatory streaking of surrounding fat, a pericecal phlegmon or abscess, an appendicolith, or RLQ intra-abdominal free air that signals perforation. CT scan is particularly useful in distinguishing between periappendiceal abscesses and phlegmon.
MRI is an alternative when one needs cross-sectional imaging that avoids ionizing radiation. It is particularly useful in a pregnant patient whose appendix is not visualized on US (Radiology 2006;238:891).
E. Diagnostic laparoscopy
Diagnostic laparoscopy is most useful for evaluating ovulating women with an equivocal examination for appendicitis. In this subgroup, one third of women prove to have primary gynecologic pathology. The appendix may also be removed via the laparoscopic approach. Therefore, some surgeons advocate an initial laparoscopic approach in all ovulating women with suspected appendicitis.
F. Differential diagnosis
Gastroenteritis is characterized by nausea and emesis before the onset of abdominal pain, along with generalized malaise, high fever, diarrhea, and poorly localized abdominal pain and tenderness. Although diarrhea is one of the cardinal signs of gastroenteritis, it can occur in patients with appendicitis. In addition, WBC count is often normal in patients with gastroenteritis.
Mesenteric lymphadenitis usually occurs in patients younger than 20 years old and presents with middle, followed by RLQ, abdominal pain but without rebound tenderness or muscular rigidity. Nodal histology and cultures obtained at operation can identify etiology, most notably Yersinia and Shigella species and Mycobacterium tuberculosis. Mesenteric lymphadenitis is known to be associated with upper respiratory tract infections.
Meckel diverticulitis presents with symptoms and signs indistinguishable from those of appendicitis, but it characteristically occurs in infants.
Peptic ulcer disease, diverticulitis, and cholecystitis can present clinical pictures similar to those of appendicitis.
Typhlitis, characterized by inflammation of the wall of the cecum or terminal ileum, is managed nonoperatively. It is most commonly seen in immunosuppressed patients undergoing chemotherapy for leukemia and in HIV-positive patients. It is difficult to distinguish preoperatively between typhlitis and appendicitis.
Pyelonephritis causes high fevers, rigors, costovertebral pain, and tenderness. Diagnosis is confirmed by urinalysis with culture.
Ureteral colic. Passage of renal stones causes flank pain radiating into the groin but little localized tenderness. Hematuria suggests the diagnosis, whichis confirmed by intravenous pyelography or noncontrast CT. Abdominal plain films frequently show renal stones.
Pelvic inflammatory disease can present with symptoms and signs indistinguishable from those of acute appendicitis, but the two often can be differentiated on the basis of several factors. Cervical motion tenderness and milky vaginal discharge strengthen a diagnosis of PID. In patients with PID, the pain is usually bilateral, with intense guarding on abdominal and pelvic examinations. Transvaginal US can be used to visualize the ovaries and to identify tubo-ovarian abscesses.
Ectopic pregnancy. A pregnancy test should be performed in all female patients of child-bearing age presenting with abdominal complaints. A positive test should prompt US investigation.
Ovarian cysts are best detected by transvaginal or transabdominal US.
Ovarian torsion. The inflammation surrounding an ischemic ovary often can be palpated on bimanual pelvic examination. These patients can have a fever, leukocytosis, and RLQ pain consistent with appendicitis. A twisted viscus, however, differs in that it produces sudden, acute intense pain with simultaneous frequent and persistent emesis. Ovarian torsion may be confirmed by Doppler US.
A. Preoperative preparation
Intravenous isotonic fluid replacement should be initiated to achieve a brisk urinary output and to correct electrolyte abnormalities. Nasogastric suction is helpful, especially in patients with peritonitis. Temperature elevations are treated with acetaminophen and a cooling blanket. Anesthesia should not be induced in patients with a temperature higher than 39°C.
B. Antibiotic therapy
Antibiotic prophylaxis is generally effective in the prevention of postoperative infectious complications (wound infection, intra-abdominal abscess). Preoperative initiation is preferred, although some suggest that it can be delayed (Cochrane Database Syst Rev 2005;20:CD001439). For acute appendicitis, coverage typically consists of a second-generation cephalosporin. In patients with acute nonperforated appendicitis, a single dose of antibiotics is adequate. Antibiotic therapy in perforated or gangrenous appendicitis should be continued for 3 to 5 days.
With very few exceptions, the treatment of appendicitis is appendectomy. Patients with diffuse peritonitis or questionable diagnosis should be explored through a midline incision. The mortality after appendectomy is high in elderly patients. Equivocal diagnosis of appendicitis in this frail patient population warrants increased diagnostic efforts before emergent appendectomy (Ann Surg 2001;233:4). In most patients, a transverse incision (e.g., Rockey-Davis, Fowler-Weir) provides the best cosmetic appearance and allows easy extension medially for greater exposure. The external and internal oblique and transversus abdominis muscle layers may be split in the direction of their fibers. After entering the peritoneal cavity, obtain purulent fluid for Gram stain and culture. Once the cecum is identified, the anterior taenia can be followed to the base of the appendix. The appendix is gently delivered into the wound and any surrounding adhesions carefully disrupted. If the appendix is normal on inspection (5% to 20% of explorations), it is removed and appropriate alternative diagnoses are entertained. The cecum, sigmoid colon, and ileum are carefully inspected for changes indicative of diverticular (including Meckel diverticulum), infectious, ischemic, or inflammatory bowel disease (e.g., Crohn’s disease). Evidence of mesenteric lymphadenopathy is sought. In women, the ovaries and fallopian tubes are inspected for evidence of PID, ruptured follicular cysts, ectopic pregnancy, or other pathology. Bilious peritoneal fluid suggests peptic ulcer or gallbladder perforation.