General Surgery

Acute Appendicitis

Acute inflammation of the appendix usually causes migrating abdominal pain and right iliac fossa peritonism, but atypical presentations and complications require early senior assessment, targeted imaging and timely source control.

In a nutshell

Appendicitis usually presents with migrating abdominal pain and right iliac fossa peritonism, but there is no single rule-in or rule-out feature. Assess physiology and pregnancy status, use age- and context-appropriate imaging, treat sepsis promptly and obtain timely surgical or procedural source control for complicated disease.

Classic presentation

Pain starts centrally and migrates to the right iliac fossa, followed by anorexia, nausea or vomiting, low-grade fever and localised tenderness or guarding.

Key points

Pain often starts centrally and migrates to the right iliac fossa as inflammation reaches the parietal peritoneum, but atypical position and patient factors are common.
A normal early FBC or CRP does not exclude appendicitis; serial assessment matters.
Pregnancy testing belongs in the assessment of anyone who could be pregnant, and ectopic pregnancy must remain in the differential.
Use ultrasound particularly in children and pregnancy; use CT selectively in stable adults with uncertainty or concern for complications, following the local pathway.
Alvarado or another score may support communication, but should not replace examination, imaging or senior review.
Laparoscopic appendicectomy is the usual definitive treatment for uncomplicated disease where feasible; antibiotics-only treatment is for selected patients after specialist discussion.
Perforation, generalised peritonitis, sepsis or an abscess require a complication pathway with antibiotics and source-control planning.
Do not treat an appendix mass as routine uncomplicated appendicitis; initial antibiotics with or without drainage may be appropriate.
Persistent symptoms, anaemia, bowel change or concerning histology in an older patient need colorectal follow-up rather than automatic reassurance.

First-line investigation

Clinical assessment with serial observations and examination, FBC/CRP/U&E, urinalysis and pregnancy testing where relevant, followed by ultrasound or CT selected by age, pregnancy and diagnostic uncertainty.

Management

Stabilise and recognise the high-risk presentation

Use ABCDE, monitoring, IV access, appropriate fluids, analgesia and antiemetics; keep a likely procedural patient nil by mouth and repeat observations and examination.^3,5
Call senior surgery early for peritonism, deterioration, shock, suspected perforation, an abscess or a high-risk atypical presentation.^3,2

Confirm the clinical risk and exclude mimics

Send FBC, CRP and U&E with targeted lactate, glucose/ketones, cultures, amylase/lipase or group-and-save; perform urinalysis and a pregnancy test when relevant.^1,3,8
Use a local score only as an adjunct; consider ectopic pregnancy, urinary and gynaecological disease, gastroenteritis, bowel obstruction, inflammatory bowel disease and medical mimics.^1,8,3

Choose imaging and treat infection

Use ultrasound particularly in children and pregnancy; in a stable adult with unresolved uncertainty or suspected complication, discuss CT with senior surgery and radiology.^2,4
For suspected intra-abdominal sepsis, follow NICE NG253 and local antimicrobial policy; high-risk adults need broad-spectrum IV antibiotics within 1 hour and IV fluid treatment without delay unless contraindicated.^5,6,7

Obtain source control for complicated disease

Offer laparoscopic appendicectomy for usual uncomplicated disease where feasible; selected patients may follow a specialist antibiotics-first pathway after risks and recurrence are discussed.^2,4
Generalised peritonitis, shock, worsening sepsis or suspected perforation require urgent operative or procedural source-control planning with anaesthetic and critical-care support.^3,5
An appendix mass or abscess may need antibiotics with or without image-guided drainage; later surgery is individualised rather than automatic.^2,3

Monitor complications and make disposition safe

After surgery or non-operative treatment, worsening pain, fever, sepsis, ileus or failure to improve should prompt senior review and consideration of CT for a residual or postoperative collection.^2,1
Before discharge, confirm symptom control, oral intake, stable observations, a documented follow-up plan and return precautions; persistent bowel symptoms, anaemia or concerning findings in an older patient need colorectal assessment.^2,9

Exam traps

Do not exclude appendicitis because the pain is not in the right iliac fossa, especially in pregnancy, children, older adults or a retrocaecal or pelvic appendix.
Do not use a normal early inflammatory marker or an intermediate score as a rule-out test.
A positive pregnancy test with abdominal pain changes the pathway: ectopic pregnancy requires urgent early-pregnancy or gynaecology assessment.
Sudden improvement followed by worsening diffuse pain can signal perforation.
Antibiotics-only treatment is selective; it is not adequate source control for generalised peritonitis or deterioration.
An appendix abscess or mass is a complicated presentation and may need antibiotics, drainage and individualised surgical planning.
Persistent fever, pain or ileus after appendicectomy should prompt review for a collection or other complication.
In older adults or with persistent bowel symptoms, consider colorectal pathology rather than assuming every presentation is isolated appendicitis.

Illustrations

Mechanism of migratory pain in appendicitisDiagram showing appendiceal inflammation, early visceral peri-umbilical pain and later parietal peritoneal irritation localising pain to the right iliac fossa. Include a note that appendix position and patient factors can make the pattern atypical.PassFinals · original

CT appearance of acute appendicitisAxial contrast CT image showing a dilated, thick-walled appendix with surrounding fat stranding and a possible appendicolith; image is for recognition and does not replace clinical assessment.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Gross pathology of acute appendicitisResected inflamed appendix with an exudate-covered serosal surface, illustrating the macroscopic correlate of transmural inflammation.Ed Uthman from Houston, TX, USA, Wikimedia Commons · CC-BY-2.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.