Chapter 3-10: Appendicitis

TEXTBOOK PRESENTATION

The classic presentation of appendicitis is abdominal pain that is initially diffuse and then intensifies and migrates toward the right lower quadrant (RLQ) to McBurney point (1.5–2 inches from the anterior superior iliac crest toward umbilicus). Patients often complain of bloating and anorexia.

DISEASE HIGHLIGHTS

1. Appendicitis is one of the most common causes of an acute abdomen, with a 7% lifetime occurrence rate.

2. It develops secondary to obstruction of the appendiceal orifice with secondary mucus accumulation, swelling, ischemia, necrosis, and perforation.

3. Initially, the pain is poorly localized. However, progressive inflammation eventually involves the parietal peritoneum, resulting in pain localized to the RLQ.

4. The risk of perforation increases steadily with age.

   1. Ages 10–40, 10%

   2. Age 60, 30%

   3. Age > 75, 50%

EVIDENCE-BASED DIAGNOSIS

1. The classic presentation of nausea and vomiting with pain migration from the periumbilical area to the RLQ is present in only 50–65% of patients.

2. RLQ pain is the most useful clinical finding; LR+, 7.3–8.5; LR–, 0.0–0.3

3. Most of the clinical findings have low sensitivity for appendicitis making it difficult to rule out the diagnosis.

   1. In one study, guarding was completely absent in 22% of patients, and rebound was completely absent in 16% of patients with appendicitis.

   2. Fever was present in only 40% of patients with perforated appendices.

Fever, severe tenderness, guarding, and rebound may be absent in patients with appendicitis.

4. Nonetheless, certain findings increase the likelihood of appendicitis when present (ie, rebound, guarding) (Table 3-6).

5. Symptoms are different in octogenarians than in patients aged 60–79 years.

   1. Symptom duration is longer (48 vs 24 hours).

   2. They are less likely to report that pain migrated to the RLQ (29% vs 49%).

6. History is particularly important in women to differentiate other causes of RLQ pain (eg, PID, ruptured ectopic pregnancy, ovarian torsion, and ruptured ovarian cyst). The most useful clinical clues that suggest PID include the following:

   1. History of PID

   2. Vaginal discharge

   3. Cervical motion tenderness on pelvic exam

Rule out ectopic pregnancy in premenopausal women who complain of abdominal pain by testing urine for beta-HCG.

7. White blood cell (WBC) count and C-reactive protein (CRP)

   1. The WBC and CRP neither identify nor rule out acute appendicitis.

   2. WBC > 10/mcL

      1. The sensitivity is only 82% with an LR– of only 0.4

      2. In patients presenting in the first 24 hours

         1. Sensitivity is only 23%; specificity is 41%

         2. LR+, 1.4

   3. CRP > 10 mg/L

      1. Sensitivity, 77%; specificity, 37%

      2. LR+, 1.2; LR–, 0.6

The WBC and CRP cannot reliably rule in nor rule out acute appendicitis.

8. Urinalysis may be misleading and reveal pyuria and hematuria due to bladder inflammation from an adjacent appendicitis.

9. Clinical decision rules:

   1. There are 2 clinical decision rules.

      1. The Alvarado score

         1. Most commonly validated rule

         2. However, has a wide sensitivity (68–96%) and specificity (58–89%)

      2. The Appendicitis Inflammatory Response score

         1. Less commonly used (Table 3-7)

         2. Its specificity is similar 62–85% (LR+, 2.4–6.2), but it has a ...