Appendicitis — Adult

Key Points

• Appendicitis can be atypical in older adults, pregnancy, pelvic or retrocecal anatomy, and immunocompromised patients.
• Clinical scores help stratify risk but do not replace imaging or surgical judgment when the diagnosis is uncertain.
• CT is highly accurate in many nonpregnant adults; ultrasound and MRI reduce radiation when appropriate.
• Differentiate uncomplicated disease from perforation, abscess, phlegmon, and generalized peritonitis.
• Laparoscopic appendectomy remains standard definitive therapy for most patients.
• Antibiotics-first treatment is an option for carefully selected uncomplicated cases after shared decision making.
• An appendicolith increases the chance of failure or recurrence with nonoperative treatment.
• Complicated disease requires source control and a tailored antibiotic strategy.

Algorithm

1. Assess pain pattern, peritoneal signs, hemodynamics, pregnancy possibility, and alternative diagnoses.
2. Obtain CBC, metabolic panel, urinalysis, pregnancy testing when relevant, and inflammatory markers as appropriate.
3. Use CT, ultrasound, or MRI according to age, pregnancy status, body habitus, and local expertise.
4. Classify disease as uncomplicated, perforated, abscess-forming, phlegmonous, or diffuse peritonitis.
5. Consult surgery early when imaging or examination strongly supports appendicitis.
6. Give analgesia, fluids as needed, NPO status, and enteric gram-negative plus anaerobic antibiotic coverage before surgery or during nonoperative treatment.
7. Proceed to appendectomy for most patients and urgently for sepsis, free perforation, or generalized peritonitis; consider antibiotics-first only in selected uncomplicated disease.
8. Arrange pathology review, complication follow-up, and age-appropriate evaluation for occult neoplasm when indicated.

Clinical Synopsis & Reasoning

Classic appendicitis begins with vague periumbilical pain that migrates to the right lower quadrant, accompanied by anorexia, nausea, and fever, but many adults have atypical symptoms. Retrocecal, pelvic, pregnancy-associated, older-age, and immunocompromised presentations may lack focal guarding or migration. Examine for localized tenderness, percussion or movement pain, guarding, rebound, and signs of generalized peritonitis. The Alvarado score can support risk assessment but is not accurate enough to serve as a stand-alone diagnostic test or to decide surgery by itself. Leukocytosis and elevated CRP support inflammation but are nonspecific. Contrast-enhanced CT of the abdomen and pelvis is highly accurate in most nonpregnant adults and also identifies perforation, abscess, appendicolith, or an alternative diagnosis. Ultrasound is useful when radiation avoidance is important, and MRI is preferred after nondiagnostic ultrasound in pregnancy when available. Differential diagnoses include gastroenteritis, Crohn disease, diverticulitis, ureteral stone, pyelonephritis, mesenteric adenitis, ovarian torsion, ectopic pregnancy, PID, and other surgical pathology. Distinguish uncomplicated appendicitis from perforation, diffuse peritonitis, abscess, or phlegmon because management pathways differ. An appendicolith may increase failure and recurrence risk with nonoperative antibiotic treatment.

Treatment Strategy & Disposition

Provide analgesia, antiemetic therapy, IV fluids when needed, and keep the patient NPO once surgery is likely. Give preoperative antibiotics covering enteric gram-negative organisms and anaerobes. Laparoscopic appendectomy is standard definitive treatment for most operable adults and is urgent when there is diffuse peritonitis, sepsis, free perforation, or clinical deterioration. Selected adults with imaging-confirmed uncomplicated appendicitis can choose an antibiotics-first strategy after informed discussion. Nonoperative treatment avoids immediate surgery for many patients but carries a meaningful risk of treatment failure, recurrence, and later appendectomy, particularly when an appendicolith is present. Local protocols vary regarding observation and oral transition. Complicated appendicitis with a well-contained abscess or phlegmon may be managed with antibiotics plus selective percutaneous drainage, followed by individualized decisions about interval appendectomy. Routine interval appendectomy is not required for every successfully treated patient, but adults at increased risk of appendiceal neoplasm, particularly older patients with complicated disease, may need colon evaluation or interval surgical assessment. Avoid delaying source control in a septic or perforated patient solely to complete a scoring system. After surgery, uncomplicated appendicitis usually needs no prolonged postoperative antibiotics, while complicated disease requires a shorter, source-control-based course according to operative findings and clinical response.

Epidemiology / Risk Factors

• Appendicitis is one of the most common causes of emergency abdominal surgery.
• Incidence peaks in adolescents and young adults but appendicitis occurs at any age.
• Delayed presentation increases the probability of perforation and abscess.
• Older adults have a higher rate of atypical presentation, perforation, and underlying appendiceal or colonic neoplasm.
• Antibiotics-first strategies have expanded treatment choices for uncomplicated disease but have not eliminated recurrence risk.

Investigations

Alvarado Score (Abbrev.)

Pharmacology

Prognosis / Complications

• Uncomplicated appendectomy generally has excellent outcomes and rapid recovery.
• Perforation increases risk of abscess, ileus, wound infection, and longer hospitalization.
• Many selected uncomplicated cases initially treated with antibiotics avoid surgery in the short term, but recurrence or later appendectomy remains common over longer follow-up.
• Adequate source control and short evidence-based antibiotic courses reduce complications without unnecessary prolonged therapy.
• Missed appendiceal neoplasm is an important consideration after complicated appendicitis in older adults.

Patient Education / Counseling

• Explain the tradeoff between definitive surgery and antibiotics-first treatment when both are reasonable options.
• After discharge, seek urgent care for worsening abdominal pain, fever, repeated vomiting, syncope, or inability to tolerate fluids.
• Follow wound and activity instructions after appendectomy and report increasing redness, drainage, or fever.
• If treated without surgery, explain recurrence risk and provide a clear plan for recurrent right-lower-quadrant symptoms.
• Complete recommended colon or surgical follow-up when complicated appendicitis or age raises concern for underlying neoplasm.

Notes

The main modern decision is not whether appendicitis needs attention, but which patients require immediate source control and which truly have uncomplicated disease suitable for a nonoperative option. Imaging is central to that distinction. Antibiotics-first treatment should be presented as an alternative with a different risk profile, not as a guaranteed cure. Patients need to understand the chance of recurrence and later appendectomy. In perforation, sepsis, or generalized peritonitis, source control takes priority and delay increases harm.

References

1. WSES Jerusalem Guidelines 2020 Update: Diagnosis and Treatment of Acute Appendicitis — Link