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Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e

Chapter 81: Acute Appendicitis E. Paul DeKoning

INTRODUCTION AND EPIDEMIOLOGY

Between 250,000 and 300,000 appendectomies for acute appendicitis are performed each year in the United

States,1 with an additional 700,000 patients a�ected in the European community.2 The lifetime risk of acute

appendicitis in the United States is an estimated 12% for males and 25% for females.3 Yet, the epidemiologyof this common ED diagnosis continues to change. Data suggest a reversal of a previous decline in incidence,

with the annual rate increasing from 7.62 to 9.38 per 10,000 between 1993 and 2008,4 whereas the rate of

negative appendectomy has declined.5 Similarly, between 2001 and 2008 the rate of perforation decreased,

but this declining trend has not been consistent.4,6 Acute appendicitis is most common in patients aged 10 to

19 years,4 remains the most frequent cause of atraumatic abdominal pain in children >1 year old,7 and is the

most common nonobstetric surgical emergency in pregnancy, complicating up to 1 in 1500 pregnancies.8,9

Despite advances in lab testing and imaging, accurate diagnosis is a challenge. Both "missed appendicitis"and unnecessary surgery for a false diagnosis are not without consequence. Thus, consider appendicitis inany patient with acute atraumatic abdominal pain without prior appendectomy.

PATHOPHYSIOLOGY

Appendicitis is caused by luminal obstruction of the vermiform appendix, typically by a fecalith. Other lessfrequent causes include obstruction by lymphatic tissue, gallstone, tumor, or parasites. Continued secretionfrom the luminal mucosa results in increased intraluminal pressure and appendiceal vascular insu�iciency,leading ultimately to bacterial proliferation and inflammation. Le� unchecked, perforation may occur.

Visceral innervation produces the vague, hard to localize periumbilical or central abdominal discomfortfrequently observed early in the clinical course. Progressive inflammation and subsequent irritation of thesomatically innervated parietal peritoneum produces the classic migration of pain to the right lowerquadrant, to McBurney's point, located one third of the distance from the anterior superior iliac spine to the

umbilicus. Up to 50% of patients may have an atypical presentation10 due in part to anatomic variation. Forexample, a retrocecal appendix produces right flank or pelvic pain, whereas malrotation of the colon resultsin transposition of the appendix and, subsequently, pain to the le� upper quadrant. Abdominal organdisplacement from a gravid uterus may lead to right upper quadrant tenderness in pregnancy. Even so, a

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right lower quadrant location of pain remains the most common location of pain in pregnant women with

appendicitis.9

CLINICAL FEATURES

The signs and symptoms of acute appendicitis lie along a spectrum that correlates with pathophysiology.Early on, patients classically complain of nonspecific symptoms of general malaise, indigestion, or bowelirregularity. Anorexia is common but not universally present. Alterations in bowel function are highly variable

and can include constipation, diarrhea, and even obstruction as a late complication.11 Periumbilical orcentral abdominal pain generally develop a�er nonspecific symptoms. If nausea develops, it typically follows

the onset of pain.12 Vomiting may or may not be present. Subjective or objective fever is frequent.

As the clinical course progresses, discomfort migrates to the right lower quadrant. Flank pain, dysuria, or

hematuria can occur, given the typical proximity of the appendix to the urinary tract.11

Aggravating and alleviating features can help establish the diagnosis: worsening pain with deep inspirationmay be present if there is peritoneal irritation, and individuals may state that the trip to the hospital waspainful, particularly when encountering bumps in the road. Such features suggest a peritoneal process isunder way. The release of intraluminal obstruction with perforation o�en results in sudden remittance of

pain; consider appendiceal perforation if the patient's pain has suddenly improved.11

As the natural course progresses, examination findings likewise evolve. Progressive inflammation andperitoneal irritation yield reproducible tenderness to palpation in the right lower quadrant. The exception toright lower quadrant pain is a retrocecal appendix, which does not contact the anterior parietal

peritoneum.13 Rebound tenderness and involuntary guarding suggest peritonitis. Patients may havecostovertebral tenderness, and percussion of the right heel or shaking of the hospital stretcher may elicitabdominal pain. There is no evidence that the digital rectal exam aids significantly in the diagnosis of acute

appendicitis.10 Rovsing's sign reproduces pain over McBurney's point as the clinician palpates thedescending colon in the le� lower quadrant. A positive psoas sign or obturator test suggests an inflammatoryperitoneal process. The psoas sign is elicited if abdominal pain is produced with extension of the right leg atthe hip while the patient lies on the le� side. The obturator test elicits pain with internal and external rotationof the flexed right thigh at the hip. The presence of abdominal rigidity, a positive psoas sign, fever, orrebound tenderness increases the likelihood of acute appendicitis. Prior episodes of similar pain, theabsence of right lower quadrant pain, and the absence of classic pain migration make appendicitis less likely.The presence or absence of any exam finding in isolation is neither su�iciently sensitive nor specific to ruleout or rule in the diagnosis.

In a systematic review of 42 studies investigating appendicitis in patients aged 18 years or younger, fever wasthe single most useful sign with an LR(+) of 3.4 (95% confidence interval, 2.4 to 4.8), whereas its absencedecreased the likelihood of appendicitis (LR(-), 0.32; 95% CI, 0.16 to 0.64). Rebound tenderness and pain

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migration to the right lower quadrant were also strong predictors.14 In comparison, a classic study of examfindings in adult patients showed right lower quadrant pain as the single most useful sign (sensitivity, 0.81;specificity, 0.53; LR(+) 7.31-8.46; LR (-) 0-.28) followed by rigidity and migration of pain. Fever in adults had an

LR(+) of 1.94 (95% CI, 0=0.28) of 1.94 (95% CI, 1.63 to 2.32) and a LR(-) of 0.58 (95% CI, 0.51 to 0.67).15 In bothchildren and adults, however, no historical or physical examination finding is su�icient to rule in or rule out

appendicitis.14,15

DIAGNOSIS

Despite the advent of cross-sectional radiographic imaging and high-definition ultrasonography and a morethan doubling of their use in recent years, detection rates for appendicitis have essentially remained the

same.16 There are numerous appendicitis mimics, and the di�erential diagnosis is broad (Table 81-1).Perform a complete physical examination, including a pelvic examination in women of childbearing age.Acute appendicitis is largely a clinical diagnosis, and no one adjunctive test is universally indicated.

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TABLE 81-1

Di�erential Diagnosis of Right Lower Quadrant Pain

GI

Cecal/Meckel's diverticulitis

Cecal volvulus

Colitis/terminal ileitis

Constipation/ileus/bowel obstruction

Crohn's/ulcerative colitis flair

Epiploic appendagitis

Functional abdominal pain

Incarcerated inguinal hernia

Intra-abdominal abscess

Intussusception

Malrotation

Mesenteric lymphadenitis

GU

Ectopic/heterotopic pregnancy

Ovarian torsion

Ovarian vein thrombosis

Pyelonephritis

Referred testicular pain

Renal colic

Tubo-ovarian abscess/salpingitis

MUSCULOSKELETAL

Abdominal wall/rectus sheath hematoma

Psoas abscess

Consider appendicitis in any patient with atraumatic right-sided abdominal, periumbilical, or flank pain whohas not previously undergone appendectomy. Available diagnostic adjuncts include peripheral WBC andother acute inflammatory markers (e.g., C-reactive protein or erythrocyte sedimentation rate), urinalysis, anda pregnancy test. Diagnostic imaging should be considered in atypical presentations or if significantdiagnostic uncertainty exists a�er thorough history and examination.

SCORING SYSTEMS

Scoring systems, such as the Alvarado and Samuel scores, have been developed to aid in diagnosis. Themodified Alvarado score for acute appendicitis ranks symptoms (migration, 1 point; anorexia or urinaryacetone, 1 point; nausea or vomiting, 1 point), signs (right lower quadrant tenderness, 2 points; rebound, 1

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point; fever, 1 point), and WBC count (>10,000/mm3, 2 points) into low-risk appendicitis (score, 1 to 4) andpossible or probable appendicitis (score, 5 to 9). However, the low-risk score (score, 1 to 4) was demonstratedas only 72% sensitive compared to 93% for clinical judgment when appendicitis was either the most likely or

second most likely diagnosis.17 Despite continued technologic advances and development of decision rules,di�erent scoring systems o�en yield conflicting results and should not replace clinical judgment; the clinical

impression of the experienced physician has the highest impact on patient outcome.18,19,20,21

LABORATORY TESTING

An increase in peripheral WBC may be the earliest marker of inflammation.22 A study of 722 childrenidentified both prospectively and retrospectively found acute appendicitis to be the most common diagnosis

in children >4 years old with nontraumatic abdominal pain and leukocytosis.23 However, a normal WBC is not

uncommon, and leukopenic presentations have been documented.24 While numerous studies have

evaluated the use of the WBC, there is no clear consensus on its utility.22,23,25,26,27 The WBC does not

distinguish between simple and perforated appendicitis.25 C-reactive protein and the erythrocytesedimentation rate used alone lack the sensitivity and specificity to rule in or rule out the diagnosis. If theonly diagnostic consideration is acute appendicitis (yes or no), the greatest utility of laboratory tests may bein combination: an elevated WBC and/or C-reactive protein may have a combined sensitivity as high as 98%.Normal values of both in patients with a low pretest probability of acute appendicitis make pathologically

confirmed appendicitis very unlikely.27,28,29,30,31 However, WBC and C-reactive protein levels are elevated ina number of other appendicitis mimics, so these markers are not useful if the di�erential diagnosis of pain is

broad.32,33

Obtain a urinalysis because isolated microscopic hematuria may support a diagnosis of renal colic, andpyuria may suggest pyelonephritis. However, hematuria or sterile pyuria can be present in acute

appendicitis.11 Document a negative pregnancy test in females of reproductive age to rule out ectopic orheterotopic pregnancy. Other laboratory tests are not routinely indicated but may be beneficial whenconsidering other diagnoses.

IMAGING

Obtain early surgical consultation before imaging in straightforward cases of suspected appendicitis in

adults. Imaging is not universally necessary but may be of benefit in certain populations.34,35,36 In children,some centers prefer pediatric surgery consultation prior to imaging with ionizing radiation.

When adjunctive imaging is indicated, early surgical consultation may aid guidance in imaging selection. Thegoal of imaging is to establish the diagnosis of appendicitis, avoid a negative appendectomy, identifyperforation, and exclude other causes of abdominal pain with minimal radiation, cost, and time.

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Plain radiography is not helpful. Findings are typically nonspecific but may demonstrate a nonspecific bowelgas pattern or adynamic ileus. An appendicolith may be visualized in up to 50% of children with

appendicitis.35

US

Graded compression US should be the initial imaging modality of choice in both pregnant females37 andchildren. It can likewise be considered in young, nonobese adults. Reports of the e�ectiveness of US

diagnosis of appendicitis in pregnancy are conflicting, with some reporting US as useful38 and others

reporting it as ine�ective for diagnosis.39 Regardless, US is safe, fast, well tolerated, and cost-e�ective.

The appendix is oval in the axial plane, ends blindly in the longitudinal plane, and should be compressible

with a maximal diameter not exceeding 6 mm.40 The normal appendix is typically di�erentiated from smallbowel on US by the absence of peristalsis and the lack of change in configuration over time; its small sizedistinguishes it from large bowel. Typical findings in appendicitis are a thickened, noncompressible appendix

>6 mm in diameter (Figure 81-1). Doppler US may illustrate hyperemia.35 It is important to image the entire

length of the appendix, because inflammation may be more pronounced at or localized to the distal end.40

Given the highly operator-dependent nature of US, centers treating larger volumes of children may havegreater reproducibility of high-quality studies. The diagnostic accuracy of abdominal US in children is better

at ruling in acute appendicitis than excluding it.41 Besides operator skill, other limitations to accuracyinclude cases of retrocecal appendicitis or perforation, excessive abdominal guarding or bowel gas, a graviduterus or obese habitus, a decompressed bladder, and lack of patient cooperation. Perforation may lead todisappearance of specific imaging hallmarks and di�icult visualization of the appendix on US. Pelvic US may

be useful in cases of suspected appendicitis and a nondiagnostic abdominal US or CT,42 or in the

di�erentiation of appendicitis from pelvic inflammatory disease43 (see chapter 97, "Abdominal and PelvicPain in the Nonpregnant Female").

FIGURE 81-1.

Ultrasonographic demonstration of acute appendicitis. A noncompressible, inflamed appendix (red circles) isshown in a cross-sectional view (A; 7.5 MHz) and a longitudinal section (B; 7.5 MHz). Mural lamination of theswollen appendix is maintained in the early stages of acute appendicitis. C. An appendicolith (arrow) withacoustic shadowing is demonstrated (5 MHz). [Reprinted with permission from Ma OJ, Mateer JR, Reardon RF,Blaivas M. Emergency Ultrasound. 3rd ed. Copyright © The McGraw-Hill Companies, 2014, All rights reserved.Chapter 11, General Surgery Applications, Figures 11-31A&B & 11-33.]

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Abdominopelvic CT

In most adult males and nonpregnant females for whom the diagnosis of appendicitis is not su�iciently clear,consider abdominal CT that includes the abdomen and pelvis. Typical CT findings include a dilated appendix>6 mm with a thickened wall, periappendiceal inflammation, and potential visualization of an appendicolith

or abscess.44 Luminal obstruction and dilation may be relieved in cases of perforation, leading to

disappearance of specific imaging hallmarks and di�icult visualization of the appendix on CT.11

The accepted sensitivity of CT (composite studies using oral or IV contrast or no contrast) for the diagnosis of

acute appendicitis is typically >94%, with a positive predictive value >95% (Figure 81-2).34,36 In a comparisonof CT versus US, the overall sensitivity of CT in patients >2 years old was 96%, with a 96% positive predictive

value; graded compression US had an overall sensitivity of 86%, with a 95% positive predictive value.36 In

this same study,36 women who had preoperative imaging had a statistically significant lower negativeappendectomy rate than women who had no imaging, suggesting that women with suspected acuteappendicitis derive the greatest benefit from preoperative imaging. Appendiceal CT, a less frequently usedprotocol, uses rectally administered contrast only with acquisition of thin cuts through the right iliac fossa.This avoids the di�iculties of oral contrast administration in patients with active emesis and preventspotential adverse reactions of IV contrast. Time to acquisition of images is much shorter, typically around 15

minutes a�er administration of rectal contrast, but may produce significant patient discomfort.45,46

FIGURE 81-2.

Acute appendicitis on contrast CT scan as evidenced by dilated and inflamed appendix (red circle).

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Oral and IV Contrast versus Nonenhanced CT Oral contrast medium has historically been recommended forCT of the abdomen and pelvis when investigating a broad di�erential of GI or pelvic diagnoses, and manycenters continue to recommend CT imaging with both IV and oral contrast. Yet, a growing body of literaturecalls this practice into question. Multiple studies indicate that nonenhanced CT has excellent performance in

the diagnosis of acute appendicitis.47,48,49,50,51,52,53 The imaging evaluation of abdominal pain is timeintensive and impacts ED overcrowding. Unenhanced studies can significantly decrease the time to diagnosisand eliminate patient discomfort from oral (especially in vomiting patients) or rectal contrast, and avoidsaltogether the risk of renal injury from IV contrast. More than 52% of 462 patients who underwent CT imagingin at least one study had no oral, IV, or rectal contrast administered, with a combined sensitivity of 93% and apositive predictive value greater than 92%, supporting the suitability of nonenhanced CT imaging for making

the diagnosis.36 A comparison of nonenhanced CT with findings on laparoscopy reported 95% sensitivity

with 100% specificity of nonenhanced CT in suspected appendicitis,2 whereas another systematic reviewreported a pooled sensitivity of 92.7% (95% CI, 89.5% to 95.0%) and specificity of 96.1% (95% CI, 94.2% to

97.5%).47 Another systematic review of 23 studies showed equivalent or improved diagnostic performance of

nonenhanced CT when compared to oral contrast.36 Oral contrast frequently does not reach the terminalileum at the time of imaging, yet in this group of patients, at least one author has shown no diagnostic

compromise in the performance of imaging.52 Several studies attribute disagreement between nonenhanced

CT and contrasted studies more to interobserver variability than contrast medium.51,53 Noncontrast CTshould be considered an accepTable imaging modality in the workup of acute appendicitis. In patients with

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renal insu�iciency or dye allergy, administration of IV contrast is contraindicated. Body habitus may limitreproduction of noncontrast CT test characteristics; intraperitoneal fat serves as an intrinsic contrast medium

in unenhanced CT, and its paucity in very thin patients can a�ect imaging interpretation.44,45,54

MRI

Consider MRI as another reliable imaging technology in the evaluation of acute appendicitis, particularly inpregnant women. MRI avoids ionizing radiation and visualizes the entire abdomen in multiple planes. In asurvey of U.S. academic medical centers with radiology residency programs, MRI was preferred over CT (39%vs. 32%) for evaluation of appendicitis in the first trimester of pregnancy. This preference reversed in the

second and third trimesters.37 IV gadolinium crosses the placenta and is not used in pregnancy given the

teratogenic e�ects seen in animal studies.55 Gadolinium is not given to patients with renal insu�iciencybecause it may cause nephrogenic fibrosing dermopathy. Avoid MRI in the evaluation of the unsTable patientgiven the time necessary for study acquisition. Sedation may be required for small children, rendering itimpractical in many pediatric cases.

TREATMENT

Patients with acute appendicitis typically require appendectomy, so immediate surgical consultation isneeded. Patients should be maintained as "nothing by mouth" to avoid operative delay. Provideresuscitation and maintenance IV fluids with appropriate antiemetics and analgesia. Initiate perioperativeantibiotics upon diagnosis or if the patient exhibits signs of peritonitis. Appropriate choices should broadlycover aerobic and anaerobic gram-negative organisms. AccepTable regimens include ampicillin/sulbactam 3grams IV (pediatric dose, 75 milligrams/kg IV); piperacillin/tazobactam 4.5 grams IV (100 milligrams/kg IV);cefoxitin 2 grams IV (40 milligrams/kg); or metronidazole 500 milligrams IV plus ciprofloxacin 400 milligrams

IV.56 Given the nonoperative management of uncomplicated diverticulitis, salpingitis, and neonatalenterocolitis with antibiotics, some suggest a similar nonoperative approach to uncomplicated acute

appendicitis.1 However, this is not yet considered the accepted standard of care.

DISPOSITION AND FOLLOW-UP

Surgery is the accepted standard of care for acute appendicitis. If the local surgical services are inadequate orunavailable, transfer the patient to an appropriate institution. For the patient in whom the diagnosis remainselusive despite a rigorous diagnostic evaluation, consider extended observation in the ED or hospital withserial examinations, allowing for evolution of the patient's condition. Alternatively, the stable, reliablepatient without significant comorbidities may be a candidate for discharge provided they have a scheduledreturn visit to the ED or their primary physician (typically within 12 hours) for repeat examination. Patientsmust have adequate pain control and be able to tolerate oral hydration. Provide clear abdominal paindischarge instructions, including a list of concerning signs or symptoms that should prompt earlier return tothe ED.

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1. 

2. 

3. 

4. 

SPECIAL POPULATIONS

Uninsured/underinsured patients, individuals from low-income communities, and some ethnic minoritiesmay be more likely to develop appendiceal perforation, but previously observed trends have been

inconsistent in recent years.6,57 The elderly are likely to have preexisting comorbidities that alterpresentation, management, and outcomes. Institutionalized patients, those with communication di�iculties,those with poor access to medical care, and the elderly may have more vague complaints, including di�usepain, fever, or alteration in mental status. Such individuals commonly present later in the course of the

disease and are more likely to have worse outcomes.58 In such patients, an "atypical" presentation should beconsidered the norm. A low threshold for prolonged observation or admission can avoid unnecessarymorbidity and mortality.

Pregnant women warrant special attention. Acute appendicitis is the most common surgical emergency inpregnancy, and delay in diagnosis is the greatest cause of increased morbidity in the pregnant woman with

an acute abdomen.8,9,59 Ovarian torsion and ectopic or heterotopic pregnancy are additional considerations.If abdominal US is nondiagnostic, consider pelvic US, CT, or MRI. Consult with the radiologist to select themost appropriate imaging study. Many radiologists avoid CT in the first trimester given teratogenic concerns

of ionizing radiation.37 In addition, although iodinated contrast material is safe in pregnancy, avoid IV

gadolinium.55

Children are a diagnostic challenge, particularly if they cannot adequately verbalize their complaints. In suchcases, physical examination, parallel history from the parent or guardian, and a high index of suspicion arethe keys to accurate diagnosis. Pediatric imaging should begin with US, but many centers advise earlysurgical consultation before any imaging if appendicitis is a consideration.

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USEFUL WEB RESOURCE

ACEP Clinical Policy: Critical Issues in the Evaluation and Management of Emergency Department Patientswith Suspected Appendicitis—http://www.acep.org

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