It's a delicate balance: A missed diagnosis can lead to rupture and peritonitis, but 12%-18% of appendectomies are unnecessary.
John, aged 47, had sudden onset of midabdominal pain and nausea. Examination at a local emergency department (ED) revealed a diffusely tender abdomen without rebound or guarding. The ED physician sent John home with an anti-emetic and an H2 blocker. After a day, John's pain decreased, but he developed a low-grade fever. On re-evaluation, an abdominal CT scan showed a retrocecal appendix with a small abscess, indicating appendicitis with perforation.
Appendicitis results from obstruction and subsequent inflammation of the vermiform appendix. Accumulating secretions within the obstructed appendix lead to inflammation and ischemia, which can progress to necrosis and perforation. While appendicitis can occur at any age, it is most common in children (though rare in those younger than 2 years) and in people in their 20s and 30s.
When appendicitis presents with classic symptoms, diagnosis is not difficult. However, a significant number of patients, like John, present with atypical symptoms. Prompt recognition of these presentations is important for early diagnosis and treatment.1
Appendicitis as usual
The most common presentation of appendicitis is diffuse periumbilical or epigastric pain that subsequently localizes to the right lower quadrant. Focal, reproducible, and constant, the pain affects 95% of patients and increases in severity. The initial symptoms may be nonspecific, e.g., anorexia, nausea, indigestion, distension, bloating, and low-grade fever (see upper table). Pain usually precedes any nausea and vomiting. If vomiting is the presenting symptom, other diagnoses should be seriously considered.
In 80% of cases, physical examination will reveal right lower-quadrant tenderness with guarding and rebound. Pain is localized at McBurney point, or 1.5-2 inches from the anterior superior iliac spine on a line from the spine to the umbilicus. Other important findings are positive psoas, obturator, and Rovsing signs, present in up to 80%-90% of cases.
A psoas or obturator sign is considered positive when contact between the psoas or the obturator muscle and the inflamed appendix elicits pain. Rovsing sign is positive when pain is felt with pressure at a point on the left side of the abdomen corresponding to McBurney point on the right.
Rectal examination will detect tenderness in the right lower quadrant in more than half of patients. When the appendix is retrocecal, the local signs of peritonitis are less common because the bowel may lie over the appendix.
Typical laboratory findings include a leukocytosis. A WBC count >15,000/µL and/or a fever >101°F may signal a ruptured appendix. The urine may contain WBCs, RBCs, or both. All women of childbearing age suspected of having appendicitis should have a serum pregnancy test because pregnancy can affect both presenting signs and treatment.
Radiography has long been a mainstay in confirming or excluding appendicitis. Barium enema has been replaced by ultrasound and the more accurate CT scan. CT findings include peri-appendiceal fat stranding or abscess if perforation has occurred.2 Air in the appendix excludes appendicitis, but nonvisualization does not confirm appendicitis.
A scoring system of five criteria has been published to improve diagnostic accuracy. Immediate laparotomy is recommended for anyone who presents with four of the following: abdominal pain, vomiting, low-grade fever, WBC count >10,000 /µL, or polymorphonuclear cells >75%.
Confounding factors
Combining history, physical examination, blood studies, and radiologic tests will give an accurate diagnosis in 70%-80% of cases. Unfortunately, atypical presentations of appendicitis, like the one in our opener, can lead to a delay in diagnosis and increased morbidity and mortality. The sudden onset of pain experienced by John should have been concerning and might have prompted earlier abdominal imaging. Typical right lower-quadrant pain is not present in all cases. Rather than being a sign of improvement, the decrease in John's pain may have coincided with perforation, with fever related to subsequent abscess formation.
Missed diagnosis is more common in children (likely due to communication difficulties in those younger than 3 years) and in those older than 60, who may delay seeking care. In the elderly and immunosuppressed, symptoms may be atypical or absent. In women, diagnosis may be made difficult by confounding gynecologic pathology and pregnancy.
A pregnant pause
Diagnosis of appendicitis in pregnancy is difficult for several reasons. An enlarging uterus can alter the position of the appendix, which may even show up in the right upper quadrant. And loss of abdominal-wall elasticity can change presenting signs. In addition, a perforated appendix is less likely to be contained by omentum and more likely to result in generalized peritonitis.
Appendicitis is the most common cause of acute abdomen in pregnant patients and thus the most common nongynecologic surgery performed in any trimester. Ultrasound and CT are especially useful in detecting or excluding appendicitis in pregnant women. A recent study showed negative appendectomy rates with clinical evaluation alone to be 54% (7/13), with ultrasound 36% (20/55), and with ultrasound followed by CT scan 8% (1/13). The authors recommend ultrasound, followed by CT scan in patients with normal or inconclusive ultrasounds.3
Differential diagnoses
The most common alternate diagnoses for appendicitis (see lower table, above) originate in adjacent organs, e.g., ileocolitis due to acute infection or inflammatory bowel disease. Bacterial enteric infections that commonly mimic appendicitis are those due to salmonella, Campylobacter, Shiga toxin-producing Escherichia coli (E. coli O157:H7), and Yersinia enterocolitica. These infections involve the ileocolonic areas in the right lower quadrant. Yersinia also causes a mesenteric adenitis that produces right lower-quadrant pain. Yersinia pseudotuberculosis can cause both appendicitis and a pseudo-appendicitis picture. Other pathogens with a predilection for the ileocecal area are Mycobacterium tuberculosis and Entamoeba histolytica. Tuberculosis usually presents with chronic pain.
Viruses—measles, adenovirus, and cytomegalovirus—have rarely been associated with appendicitis. Fungi are also uncommon, but Histoplasma capsulatum, aspergillus, and actinomyces may account for a very small number of cases. Parasite worms or eggs can cause appendicitis by occluding the lumen—Enterobius vermicularis (pinworm) and Ascaris lumbricoides have been reported but are usually an incidental finding.
In women, symptoms similar to those of appendicitis can be due to pathology of the ovary, fallopian tubes, and uterus, including ruptured ovarian cysts, ectopic pregnancy, and pelvic inflammatory disease. These possibilities contribute to a negative appendectomy rate as high as 20% in women. (The rate in men can be as low as 10%.)
Colonic adenocarcinoma or, less likely, lymphoma in the cecum can present with right lower-quadrant pain, as can right-sided diverticulitis and Crohn's ileocolitis.
Urinary disease, including kidney stones and pyleonephritis, should also be excluded. Uncommon differentials are osteomyelitis of the iliac bones and abscess of the psoas or gluteal muscles.
Therapy—and the role of antibiotics Appropriate management requires accurate early diagnosis and surgical intervention. Because the consequences of missed appendicitis are perforation, abscess, and possible death, an aggressive surgical approach is usual. Overall mortality is low—1%.
Postsurgical antibiotics are given for prophylaxis of wound infection only if the appendix is not perforated. Patients with perforation and abscess whose symptoms have lasted five days or longer at presentation may have their surgery delayed for a few days to allow broad-spectrum antibiotics, IV fluids, and bowel rest. This delay is intended to decrease morbidity due to local inflammation.
A recent study questioned the need for surgery in 252 men aged 18-50 years who had acute appendicitis and were planning to undergo appendectomy. Study participants were randomized to surgery or antibiotics. Outcomes were similar for hospital stay, but evidence from this trial is not strong enough to change clinical practice.4 An excellent editorial by Søreide analyzing the article found a statistical error.5 Søreide concludes that surgery remains the gold standard of care for patients with acute appendicitis.6
For the primary-care or emergency physician, careful evaluation as well as early surgical consultation is important, especially to help distinguish surgical from nonsurgical cases. A gastroenterologist should be consulted if Crohn's disease is in the differential, but endoscopic procedures should be avoided if there is a possibility of acute appendicitis, as air from colonoscopy could perforate the appendix. There does appear to be an entity that could be described as “chronic appendicitis.” Not much is known about this condition, which is characterized by recurrent acute right lower-quadrant pain. In patients who have undergone appendectomy, histologic findings included chronic inflammation of the appendiceal wall or fibrosis of the appendix.7
Dr. Surawicz is professor of medicine at the University of Washington School of Medicine and chief of gastroenterology at Harborview Medical Center, both in Seattle.
References
1. Silen W, Cope Z. Cope's Early Diagnosis of the Acute Abdomen. 21st ed., New York, N.Y.: Oxford University Press; 2005.
2. Strömberg C, Johansson G, Adolfsson A. Acute abdominal pain: diagnostic impact of immediate CT scanning. World J Surg. 2007;31:2347-2354.
3. Wallace CA, Petrov MS, Soybel DI, et al. Influence of imaging on the negative appendectomy rate in pregnancy. J Gastrointest Surg. 2008;12:46-50.
4. Styrud J, Eriksson S, Nilsson I, et al. Appendectomy versus antibiotic treatment in acute appendicitis, a prospective multicenter randomized controlled trial. World J Surg. 2006;30:1033-1037.
5. Søreide K, Korner H, Søreide J. Type II error in a randomized controlled trial of appendectomy vs. antibiotic treatment of acute appendicitis. World J Surg. 2007;31:871-872.
6. Søreide K. Should antibiotic treatment replace appendectomy for acute appendicitis? Nat Clin Pract Gastroenterol Hepatol. 2007;4:584-585.
7. Incesu L, Taylor CR. Appendicitis. Available at: www.emedicine.com/radio. Accessed February 6, 2008.