acute appendicitis:

acute appendicitis:

Appendicitis is defined as an inflammation of the inner lining of the vermiform appendix that spreads to its other parts. Despite diagnostic and therapeutic advancement in medicine, appendicitis remains a clinical emergency and is one of the more common causes of acute abdominal pain. See the image below.

Transverse graded compression transabdominal sonogram of an acutely inflamed appendix. Note the targetlike appearance due to thickened wall and surrounding loculated fluid collection.

See Appendicitis: Avoiding Pitfalls in Diagnosis, a Critical Images slideshow, to help make an accurate diagnosis.

Also, see the Can't-Miss Gastrointestinal Diagnoses slideshow to help diagnose the potentially life-threatening conditions that present with gastrointestinal symptoms.

Essential update: New screening algorithm for pediatric appendicitis may reduce CT use

A new algorithm for screening pediatric patients (≤18 y) with suspected appendicitis appears to reduce the use of computed tomography (CT) scanning without affecting diagnostic accuracy.^{[1, 2]} This tool also has implications for reducing the levels of radiation exposure and the cost of using this imaging modality. The algorithm includes pediatric surgery consultation without imaging studies in patients with an unequivocal history; for those with an equivocal history, physical examination, and ultrasonographic findings, the algorithm includes consultation and physical examination before obtaining CT studies.^[2]

Investigators analyzed data from 331 pediatric patients with suspected appendicitis 2 years before (41%; n = 136) and 3 years after (59%; n = 195) implementation of the new algorithm and found a significant decrease in the use of CT scanning from 39% to 18%, respectively.^{[1, 2]} Moreover, although the negative appendectomy rate rose from 9% pre-implementation of the algorithm to 11% post-implementation, this increase was not significant and there was no association between negative appendectomy and CT scan utilization.^{[1, 2]}

Signs and symptoms

The clinical presentation of appendicitis is notoriously inconsistent. The classic history of anorexia and periumbilical pain followed by nausea, right lower quadrant (RLQ) pain, and vomiting occurs in only 50% of cases. Features include the following:

• Abdominal pain: Most common symptom
• Nausea: 61-92% of patients
• Anorexia: 74-78% of patients
• Vomiting: Nearly always follows the onset of pain; vomiting that precedes pain suggests intestinal obstruction
• Diarrhea or constipation: As many as 18% of patients

Features of the abdominal pain are as follows:

• Typically begins as periumbilical or epigastric pain, then migrates to the RLQ^[3]
• Patients usually lie down, flex their hips, and draw their knees up to reduce movements and to avoid worsening their pain
• The duration of symptoms is less than 48 hours in approximately 80% of adults but tends to be longer in elderly persons and in those with perforation.

Physical examination findings include the following:

• Rebound tenderness, pain on percussion, rigidity, and guarding: Most specific finding
• RLQ tenderness: Present in 96% of patients, but nonspecific
• Left lower quadrant (LLQ) tenderness: May be the major manifestation in patients with situs inversus or in patients with a lengthy appendix that extends into the LLQ
• Male infants and children occasionally present with an inflamed hemiscrotum
• In pregnant women, RLQ pain and tenderness dominate in the first trimester, but in the latter half of pregnancy, right upper quadrant (RUQ) or right flank pain may occur

The following accessory signs may be present in a minority of patients:

• Rovsing sign (RLQ pain with palpation of the LLQ): Suggests peritoneal irritation
• Obturator sign (RLQ pain with internal and external rotation of the flexed right hip): Suggests the inflamed appendix is located deep in the right hemipelvis
• Psoas sign (RLQ pain with extension of the right hip or with flexion of the right hip against resistance): Suggests that an inflamed appendix is located along the course of the right psoas muscle
• Dunphy sign (sharp pain in the RLQ elicited by a voluntary cough): Suggests localized peritonitis
• RLQ pain in response to percussion of a remote quadrant of the abdomen or to firm percussion of the patient's heel: Suggests peritoneal inflammation
• Markle sign (pain elicited in a certain area of the abdomen when the standing patient drops from standing on toes to the heels with a jarring landing): Has a sensitivity of 74% ^[4]

See Clinical Presentation for more detail.

Diagnosis

The following laboratory tests do not have findings specific for appendicitis, but they may be helpful to confirm diagnosis in patients with an atypical presentation:

• CBC
• C-reactive protein (CRP)
• Liver and pancreatic function tests
• Urinalysis (for differentiating appendicitis from urinary tract conditions)
• Urinary beta-hCG (for differentiating appendicitis from early ectopic pregnancy in women of childbearing age)
• Urinary 5-hydroxyindoleacetic acid (5-HIAA)

CBC

• WBC >10,500 cells/µL: 80-85% of adults with appendicitis
• Neutrophilia >75-78% of patients
• Less than 4% of patients with appendicitis have a WBC count less than 10,500 cells/µL and neutrophilia less than 75%

In infants and elderly patients, a WBC count is especially unreliable because these patients may not mount a normal response to infection. In pregnant women, the physiologic leukocytosis renders the CBC count useless for the diagnosis of appendicitis.

C-reactive protein

• CRP levels >1 mg/dL are common in patients with appendicitis
• Very high levels of CRP in patients with appendicitis indicate gangrenous evolution of the disease, especially if it is associated with leukocytosis and neutrophilia
• In adults who have had symptoms for longer than 24 hours, a normal CRP level has a negative predictive value of 97-100% for appendicitis ^{[5, 6, 7]}

Urinary 5-HIAA

HIAA levels increase significantly in acute appendicitis and decrease when the inflammation shifts to necrosis of the appendix.^[8] Therefore, such decrease could be an early warning sign of perforation of the appendix.

CT scanning

• CT scanning with oral contrast medium or rectal Gastrografin enema has become the most important imaging study in the evaluation of patients with atypical presentations of appendicitis
• Low-dose abdominal CT may be preferable for diagnosing children and young adults in whom exposure to CT radiation is of particular concern ^[9]

Ultrasonography

• Ultrasonography may offer a safer alternative as a primary diagnostic tool for appendicitis, with CT scanning used in those cases in which ultrasonograms are negative or inconclusive
• In pediatric patients, American College of Emergency Physicians (ACEP) clinical policy recommends ultrasonography for confirmation, but not exclusion, of acute appendicitis; to definitively exclude acute appendicitis, the ACEP recommends CT ^{[10, 11]}
• A healthy appendix usually cannot be viewed with ultrasonography; when appendicitis occurs, the ultrasonogram typically demonstrates a noncompressible tubular structure of 7-9 mm in diameter
• Vaginal ultrasonography alone or in combination with transabdominal scan may be useful to determine the diagnosis in women of childbearing age ^[12]

Other imaging studies

• Kidneys-ureters-bladder radiographs: Insensitive, nonspecific, and not cost-effective
• Barium enema study: Has essentially no role in the diagnosis of acute appendicitis
• Radionuclide scanning: Localized uptake of tracer in the RLQ suggests appendiceal inflammation
• MRI: Useful in pregnant patients if graded compression ultrasonography is nondiagnostic

See Workup for more detail.

Management

Emergency department care is as follows:

• Establish IV access and administer aggressive crystalloid therapy to patients with clinical signs of dehydration or septicemia
• Keep patients with suspected appendicitis NPO
• Administer parenteral analgesic and antiemetic as needed for patient comfort; no study has shown that analgesics adversely affect the accuracy of physical examination ^[13]

Appendectomy remains the only curative treatment of appendicitis, but management of patients with an appendiceal mass can usually be divided into the following 3 treatment categories:

• Phlegmon or a small abscess: After IV antibiotic therapy, an interval appendectomy can be performed 4-6 weeks later
• Larger well-defined abscess: After percutaneous drainage with IV antibiotics is performed, the patient can be discharged with the catheter in place; interval appendectomy can be performed after the fistula is closed
• Multicompartmental abscess: These patients require early surgical drainage

Antibiotics

• Antibiotic prophylaxis should be administered before every appendectomy
• Preoperative antibiotics should be administered in conjunction with the surgical consultant
• Broad-spectrum gram-negative and anaerobic coverage is indicated
• Cefotetan and cefoxitin seem to be the best choices of antibiotics
• In penicillin-allergic patients, carbapenems are a good option
• Pregnant patients should receive pregnancy category A or B antibiotics
• Antibiotic treatment may be stopped when the patient becomes afebrile and the WBC count normalizes