The appendix, a small, narrow, blind tube extending from the inferior part of the cecum, is widely regarded as a vestigial organ, having lost much of its original function through evolution. Despite its diminished role, the appendix can become inflamed, a condition known as appendicitis.

Etiology: Appendicitis can arise from various causes, primarily rooted in the obstruction of the appendix lumen. Factors contributing to this obstruction include fecal accumulation, lymphoid hyperplasia and, in rare instances, foreign bodies like fruit seeds and tumors.

In children, lymphoid hyperplasia is a more common cause due to the active immune response, whereas in adults, fecaliths are more common.

Pathophysiology: Appendicitis starts with an obstruction, leading to content stagnation within the appendix lumen. It results in distention and obstruction of the lumen, increasing intraluminal pressure and leading to venous congestion and lymphatic obstruction. Eventually, ischemia, bacterial overgrowth, and immune response trigger inflammation, potentially leading to perforation. The aggregation of these processes causes an inflammatory response, which generates the signs and symptoms of appendicitis. The pathophysiological progression goes from obstruction to inflammation to possible ischemia and perforation.

Clinical Manifestations

The onset of appendicitis is marked by a series of evolving symptoms that can complicate an early diagnosis. Initially, patients may experience a dull, aching pain around the umbilicus, which intensifies and shifts to the right lower quadrant of the abdomen over time. This progression of pain, mainly when it localizes at McBurney's point (halfway between the umbilicus and the right iliac crest) is a significant indicator of appendicitis.

Accompanying this pain, symptoms such as anorexia, nausea, and vomiting are common, yet these symptoms also overlap with other abdominal conditions, adding to the diagnostic challenge. A low-grade fever may develop as the condition progresses, signaling the body's response to the infection. The initial pain is often due to visceral pain, while the later localized pain is due to parietal peritoneum irritation. It's important to note that the classic symptom progression is not present in all patients, particularly in the very young, elderly, or pregnant women, where the presentation can be atypical.

A physical examination can further aid diagnosis through the identification of several indicative signs:

1. Abdominal rigidity, rebound tenderness, and muscle guarding: These signs reflect peritoneum irritation and are vital indicators of appendicitis.
2. Psoas sign: Pain elicited by extending the right thigh, indicating irritation of the psoas muscle.
3. Obturator sign: Discomfort during passive internal rotation of a flexed thigh, suggesting irritation in the obturator muscle area.
4. Rovsing's sign: Increased pain in the right lower quadrant when palpating the left lower quadrant indicates peritoneal irritation.

Although not present in every case, these physical findings are crucial for clinicians to consider when diagnosing appendicitis. External factors like coughing or sneezing can aggravate the abdominal pain, further hinting at the inflammation of the appendix and surrounding structures. Patients often seek comfort by lying still and flexing the right leg to reduce abdominal tension.