Appendicitis & Peritonitis

The appendix is a small, tube-like organ attached to the first part of the large intestine in the lower right abdomen, with no known function. Because it is a blind pouch, anything that blocks its opening — a hardened appendicolith (fecalith), hypertrophied lymphoid tissue (especially in children), a tumor, or parasites — traps its secretions inside. Often no cause is ever identified.

Once obstructed, the appendix keeps secreting mucus into a closed space, so it distends and intraluminal pressure climbs. Rising pressure occludes the small vessels in the wall — thrombosis, lymphatic stasis — and the wall becomes ischemic, then necrotic. Bacteria overgrow in the stagnant lumen (initially aerobic, later mixed aerobic and anaerobic: E. coli, Peptostreptococcus, Bacteroides, Pseudomonas). The necrotic wall finally gives way: perforation, abscess formation, peritonitis.

This cascade runs on a sourced clock: symptoms may progress over 12 to 24 hours, the risk of rupture is roughly 2% at 36 hours from symptom onset, and it climbs about 5% for every additional 12 hours. That clock is why appendicitis is a surgical emergency and why every delay in recognition costs the patient wall integrity.

Early appendicitis hurts in the wrong place: a diffuse, hard-to-localize ache around the umbilicus, minor at first. Over 12 to 24 hours it sharpens and migrates to the right lower quadrant — to McBurney’s point, roughly 1.5 to 2 inches from the anterior superior iliac spine on a straight line to the umbilicus. Rebound tenderness and localized guarding settle there, and the pain now worsens with anything that jostles the peritoneum: moving, deep breaths, coughing, sneezing (increased pain with coughing is the Dunphy sign). Appetite disappears (anorexia), often with nausea, low-grade fever, and altered bowel habits.

The neighboring muscles betray the appendix’s position. The Rovsing sign is RLQ pain elicited by pressing the left lower quadrant. The psoas sign — RLQ pain on right hip extension or resisted right thigh flexion — points to a retrocecal appendix irritating the psoas muscle; the obturator sign — RLQ pain on internal rotation of the flexed right hip — points to a pelvic appendix.

Then comes the trap. When the appendix perforates, the trapped intraluminal pressure vents — and the pain can transiently ease. The patient smiles, asks for food, looks better. It is often followed by worsening clinical status as peritonitis sets in. Sudden relief of abdominal pain in suspected appendicitis is reported to the provider immediately — alongside sudden vital-sign changes such as rising heart rate or fever — never reassured away.

The peritoneum is the thin tissue lining the inner wall of the abdomen and covering most of the abdominal organs. When the appendix ruptures, luminal contents spill into that cavity: bacterial proliferation, toxin release, and widespread peritoneal inflammation follow, driving a systemic inflammatory response (SIRS) that can progress to sepsis. The organisms are gram-negative and anaerobic enterics — E. coli, Klebsiella pneumoniae.

The exam picture is unmistakable once you know it: involuntary guarding, board-like rigidity, rebound tenderness, and diminished or absent bowel sounds. The patient holds perfectly still — often avoiding even deep breaths — because any movement hurts; a patient who is completely immobilized and cries out when the bed is bumped is showing you peritonitis. Systemically: fever, chills, tachycardia, tachypnea, hypotension progressing toward septic shock, abdominal distention, inability to pass gas, reduced urination.

Management is a resuscitation problem plus a plumbing problem: NPO, large-bore IV access, aggressive IV crystalloid resuscitation, immediate broad-spectrum antibiotics targeting gram-negative and anaerobic enteric organisms, and urgent surgical consultation for source control — surgery, or image-guided drainage of an abscess where appropriate — with MAP and lactate monitored as end-organ-perfusion parameters.

The classic story belongs to the classic patient — most common between ages 5 and 45, mean age 28. The dangerous presentations are the atypical ones. Children under 5 often lack typical symptoms — diffuse pain, vomiting, low-grade fever, or just irritability — because young children cannot localize pain or describe it. The price of that ambiguity is perforation: roughly 10–30% of pediatric cases overall, as high as 90% in children under 2.

Pregnancy moves the target: the gravid uterus displaces the appendix cephalad, so pain may sit in the right flank or right upper quadrant in advanced pregnancy. Symptoms are milder and subtler, classic signs are unreliable, fever appears in only about 40% — and the physiologic leukocytosis of pregnancy (up to 16,900 cells/mm³, higher in labor) makes the WBC nearly useless. Older adults also present atypically, which delays diagnosis and raises complication rates. Anatomy adds its own variants: a retrocecal appendix can present as flank pain, a pelvic appendix as suprapubic pain.