Chapter 43. Acute Appendicitis

Appendicitis is one of the most common surgical emergencies. Despite advances in laboratory testing and imaging, accurate diagnosis of appendicitis remains a challenge. Complications from misdiagnosis of appendicitis include intraabdominal abscess, wound infection, adhesion formation, bowel obstruction, and infertility.

The most reliable symptom in appendicitis is abdominal pain. The early signs of appendicitis are quite nonspecific and progress with time. The location of the pain depends on the location of the appendix. Pain commonly begins in the periumbilical or epigastric region. As peritoneal irritation occurs, the pain will often localize to the right lower quadrant. Other symptoms associated with appendicitis include anorexia, nausea, and vomiting but these symptoms are neither sensitive nor specific. As the pain increases, irritation of the bladder and/or colon may cause dysuria, tenesmus, or other symptoms. Many patients have the “bump” sign, where the patient notes an increase in the abdominal pain associated with bumps in the ride to the hospital. If the pain suddenly decreases the examiner should consider appendiceal perforation.

The classic point of maximal tenderness is in the right lower quadrant just below the middle of a line connecting the umbilicus and the right anterior superior iliac spine. (McBurney's point). Patients may also have pain referred to the right lower quadrant when palpating the left lower quadrant (Rovsing sign), pain elicited by extending the right leg to the hip while lying in the left lateral decubitus position (psoas sign), or pain elicited by passively flexing the right hip and knee and internally rotating the hip (obturator sign). Patients with a pelvic appendix may be quite tender on rectal examination, and patients with a retrocecal appendix may have more prominent flank pain than abdominal pain. No individual physical finding is sensitive or specific enough to rule in or rule out the diagnosis.

Fever is a relatively late finding in appendicitis and rarely exceeds 39°C (102.2°F), unless rupture or other complications occur.

The diagnosis of acute appendicitis is primarily clinical. Symptoms with high sensitivity for appendicitis include right lower quadrant pain, pain that occurs before vomiting, and absence of prior similar pain. Migration of the pain is thought to be highly specific for appendicitis. Physical signs with high specificity include right lower abdominal rigidity and positive psoas sign. Additional studies, such as complete blood count, C-reactive protein, urinalysis, and imaging studies, may be performed if the diagnosis is unclear. A pregnancy test must be performed in all females of reproductive age. A normal WBC does not rule out appendicitis. Urinalysis is useful to help rule out other diagnoses but pyuria and hematuria can occur when an inflamed appendix irritates the ureter.

The differential diagnosis of right lower quadrant pain is wide and includes other gastrointestinal processes (eg, inflammatory bowel disease, hernia, abscess, volvulus, diverticulitis), gynecologic or urological processes (eg, ectopic pregnancy, ovarian torsion, renal colic, genitourinary (GU) infection or abscess), or musculoskeletal processes (eg, muscular hematoma or abscess).

Plain radiographs of the abdomen are not helpful.

Computed tomography (CT) is the imaging study of choice with an overall sensitivity of 96% and PPV of 96%. CT findings suggesting acute appendicitis include pericecal inflammation, abscess, and periappendiceal phlegmon or fluid collections (Fig. 43-1). CT has been shown to change management in women, decreasing unnecessary tests. CT findings of appendicitis may be lacking in the thin patient. CT may be conducted with or without contrast administered orally, intravenously, or rectally, depending on institutional experience and preference. Unenhanced CT scanning has 92% sensitivity and 96% specificity. Increased concerns about accumulated radiation exposure for children, potentially childbearing females, and pregnant patients have led to interest in alternatives to the CT scan.

Ultrasonography has a high sensitivity but is limited both by operator skill and in evaluating a ruptured appendix or an abnormally located (eg, retrocecal) appendix. Graded compression ultrasonography is the initial modality of choice in both children and the pregnant patient to decrease radiation exposure. Overall sensitivity of ultrasound is 86% with PPV of 95%.

Magnetic resonance imaging for the diagnosis of appendicitis is evolving as a reliable technology that avoids completely the ionizing radiation risks. IV contrast with MRI should be avoided in the pregnant patient as it crosses the placenta.

Very young children, the elderly, pregnant women, and patients with AIDS have higher rates of misdiagnosis of appendicitis, with increased morbidity and mortality rates. Patients younger than 6 years have a high misdiagnosis rate due to poor communication skills and the association of many nonspecific symptoms. Elderly patients may have decreased perceptions of symptoms. Pregnant patients are at risk for misdiagnosis even though appendicitis is the most common extrauterine surgical emergency in pregnancy. Patients with acquired immunodeficiency syndrome are susceptible to complications from appendicitis because of delays in diagnosis due to their frequently preexisting gastrointestinal symptoms and their immunocompromised state.

1. Surgical consultation should be obtained before imaging when the diagnosis is thought to be clear. Patient should have nothing by mouth and should have intravenous (IV) access and fluids. The treatment for acute appendicitis is appendectomy.

2. Control pain with opioid analgesics, such as fentanyl 1 to 2 micrograms/ kilogram IV q1 to q4h or morphine, 0.1 milligram/kilogram.

3. Antibiotics given before surgery decrease the incidence of postoperative wound infection or, in cases of perforation, postoperative abscess formation. Several antibiotic regimens to cover anaerobes, enterococci, and gram-negative intestinal flora have been recommended, including piperacillin/tazobactam 3.375 grams IV or ampicillin/sulbactam 3 grams IV. Consult with the surgeon regarding the antibiotic regimen and timing.

4. In patients for whom the diagnosis is not clear, admit for observation, serial examinations, and surgical consultation. This is a safe option for high-risk patients (pediatric, geriatric, pregnant, or immunocompromised).

5. Stable, nontoxic-appearing patients with adequate pain control who can tolerate oral hydration, have no significant comorbidities, and are able to return for reevaluation in 12 hours may be considered for discharge and 12-hour follow-up. These patients should be instructed to avoid strong analgesics, and should return if they develop increased pain, localization of the pain, fever, nausea, or other signs or symptoms of illness that are worsening or not resolving.