Appendicitis – The Differential Diagnosis

Because many of its signs and symptoms are nonspecific, the differential diagnosis of acute appendicitis is extensive and includes virtually all possible abdominal sources of pain, as well as some nonabdominal sources (see table below). However, some diagnoses are more likely than others in certain patient groups. For instance, in young males with a suggestive history and physical examination, acute appendicitis is the most likely cause of right lower quadrant pain. Meckel’s diverticulitis causes similar symptoms, but is relatively uncommon. Gastroenteritis is considerably more common and should be expected when nausea and vomiting precede the abdominal pain, or when diarrhea is a prominent symptom. Crohn’s disease affecting the terminal ileum may resemble appendicitis in its initial presentation, but on further questioning, the patient typically describes a subacute course including fever, weight loss, and pain.

In middle-aged and older adults, other inflammatory conditions should be considered, including peptic or duodenal ulcer (with fluid tracking into the right paracolic gutter), cholecystitis, and pancreatitis. In addition, cecal or sigmoid diverticulitis can be confused with acute appendicitis. Cecal diverticulitis is quite similar in pathogenesis and presentation to appendicitis, due to the fact that cecal diverticuli, like the appendix, are true diverticuli containing all layers of the intestinal wall. Because a redundant, floppy sigmoid colon can extend to the right side of the abdomen, patients with sigmoid diverticulitis can sometimes present with right lower quadrant pain. Those patients typically describe a quicker progression to localized tenderness, as well as a prodrome of an alteration in bowel habits. Malignancies can present with acute right lower quadrant pain due to perforation of a cecal carcinoma or appendicitis caused by a mass obstructing the appendiceal orifice.39 These patients will also typically have guaiac-positive stools, anemia, and a history of weight loss.

In women of childbearing years, the diagnosis of right lower quadrant pain can be even more difficult. In addition to the causes of right lower quadrant pain mentioned for young men, young women can also have pain from obstetric and gynecological causes such as ruptured ovarian cyst or follicle, ovarian torsion, ectopic pregnancy, acute salpingitis, and tubo-ovarian abscess. A complete history including recent menstrual history, as well as pelvic examination, can be helpful in differentiating these causes of pain from acute appendicitis. Nonetheless, appendicitis can be difficult to diagnose in this patient population, and higher rates of misdiagnosis have been described in women of childbearing age.