Acute appendicitis is inflammation of the appendix, most often from luminal obstruction, and it is the most common abdominal surgical emergency in the world. NICE Clinical Knowledge Summaries, last revised in July 2025, report around 50,000 acute appendicectomies performed annually in the United Kingdom. According to the 2020 update of the WSES Jerusalem guidelines, the modern answer is risk stratification with a validated score, ultrasound as the first imaging step, and laparoscopic appendicectomy within 24 hours when surgery is needed.

Key takeaways

  • NICE Clinical Knowledge Summaries describe pain that worsens and migrates from the periumbilical or epigastric region to the right lower quadrant over 24 to 48 hours, aggravated by movement
  • The WSES 2020 update recommends the AIR score and the AAS score as clinical predictors of acute appendicitis, and suggests against using the Alvarado score to positively confirm the diagnosis in adults
  • WSES recommends point-of-care ultrasound as the most appropriate first-line diagnostic imaging in adults and children when imaging is indicated
  • WSES recommends planning laparoscopic appendicectomy for the next available operating list within 24 hours in uncomplicated acute appendicitis, and recommends against delaying beyond 24 hours from admission
  • WSES recommends a single preoperative dose of broad-spectrum antibiotics and recommends against postoperative antibiotics in uncomplicated appendicitis
  • Non-operative management with antibiotics is a discussed alternative in selected uncomplicated cases without an appendicolith, and patients must be told of a recurrence risk of up to 39% at five years

How do I recognise acute appendicitis?

Recognise acute appendicitis from migrating pain: NICE Clinical Knowledge Summaries describe periumbilical or epigastric pain that worsens and migrates to the right lower quadrant over 24 to 48 hours and is typically aggravated by movement.

The associated features NICE lists are low-grade fever, general malaise and anorexia, with nausea, vomiting and sometimes constipation or diarrhoea. Right lower quadrant tenderness is the cardinal sign, worse on coughing or hopping in children.

NICE also warns that acute appendicitis presents atypically in the very young, the elderly and in pregnancy, and that the anatomical position of the appendix varies, which changes where the tenderness is found.

Signs of peritonitis in acute appendicitis are distension, guarding, rebound or percussion tenderness and absent bowel sounds, while a palpable mass suggests an appendix mass or abscess.

Which scoring system should I use in acute appendicitis?

Use a validated score in acute appendicitis to stratify risk, not to make the diagnosis. The WSES 2020 update recommends the use of clinical scores to exclude acute appendicitis and to identify intermediate-risk patients who need imaging.

WSES recommends the AIR score and the Adult Appendicitis Score as the clinical predictors of choice. It suggests against using the Alvarado score to positively confirm the clinical suspicion of acute appendicitis in adults.

The evidence WSES cites has the AIR score as the overall best performer, with a sensitivity of 92% and a specificity of 63%. Scores are strongest at ruling appendicitis out in low-risk patients.

WSES also suggests that in high-risk patients under 40 years old, with an AIR score of 9 to 12, an Alvarado score of 9 to 10 or an AAS of 16 or more, cross-sectional imaging may be avoided before diagnostic or therapeutic laparoscopy.

What is my immediate A to E management of suspected appendicitis?

The immediate management of suspected acute appendicitis is A to E assessment with analgesia, intravenous fluid, bloods and a decision about how sick the patient is, before any argument about imaging.

Most patients with acute appendicitis are not physiologically unwell, and the assessment is quick. The ones who are unwell have perforated, and they need sepsis management, fluid resuscitation and an early call to the registrar.

Give analgesia early. It does not mask the signs in acute appendicitis in the way older teaching suggested, and withholding it has no diagnostic value while making the examination harder.

Which investigations do I order in acute appendicitis?

In acute appendicitis, send a full blood count, C-reactive protein, urea and electrolytes, a venous gas with lactate if unwell, a urine dipstick and a pregnancy test in any woman of childbearing age.

For imaging, WSES recommends point-of-care ultrasound as the most appropriate first-line diagnostic tool in both adults and children when imaging is indicated after clinical assessment and risk stratification.

WSES recommends contrast-enhanced low-dose CT over standard-dose CT in adolescents and young adults with suspected acute appendicitis and negative ultrasound findings, and recommends combining clinical parameters with ultrasound to reduce CT use.

In pregnancy, WSES suggests graded compression transabdominal ultrasound as the preferred initial imaging for suspected appendicitis, with MRI after an inconclusive ultrasound where the resource is available.

How quickly does acute appendicitis need an operation?

Acute appendicitis needing surgery should be planned for the next available operating list within 24 hours, and the WSES 2020 update recommends against delaying appendicectomy beyond 24 hours from admission.

WSES words it as minimising the delay wherever possible, which is the phrase to use. It is a recommendation about not letting a patient drift across lists, not a licence to operate overnight for its own sake.

In children, WSES suggests against delaying appendicectomy beyond 24 hours from admission in uncomplicated appendicitis, and asks for early appendicectomy within 8 hours in complicated appendicitis.

What is the definitive management of acute appendicitis?

The definitive management of acute appendicitis is laparoscopic appendicectomy, which WSES recommends as the preferred approach over open appendicectomy for both uncomplicated and complicated disease where equipment and expertise are available.

WSES recommends conventional three-port laparoscopic appendicectomy over single-incision laparoscopy, endoloops, suture ligation or polymeric clips for stump closure, and simple ligation over stump inversion.

On drains, WSES recommends against their use after appendicectomy for complicated appendicitis in adults, and recommends suction alone rather than lavage in complicated appendicitis with intra-abdominal collections.

WSES also recommends routine histopathology after appendicectomy, and suggests removing the appendix if it appears normal at surgery in a symptomatic patient when no other disease is found.

What antibiotics does acute appendicitis need?

Acute appendicitis needs a single preoperative dose of broad-spectrum antibiotics, and WSES recommends against postoperative antibiotics for patients with uncomplicated appendicitis.

For complicated appendicitis with adequate source control, WSES recommends against prolonging antibiotics beyond 3 to 5 days postoperatively. In children with complicated appendicitis it recommends an early switch to oral after 48 hours, with a total course shorter than 7 days.

If non-operative management is used for acute appendicitis, WSES recommends starting with intravenous antibiotics and switching to oral based on the patient's clinical condition.

Can acute appendicitis be treated without an operation?

Acute appendicitis can be treated without an operation in selected cases. WSES recommends discussing non-operative management with antibiotics as a safe alternative in selected patients with uncomplicated appendicitis and no appendicolith.

The consent conversation is the point. WSES says patients who wish to avoid surgery must be aware of a risk of recurrence of up to 39% after five years, and of the possibility of failure and of misdiagnosing complicated appendicitis.

An appendicolith changes the answer. WSES identifies it as an independent risk factor for failure of non-operative management, and in children recommends surgery when one is present.

For a phlegmon or an abscess, WSES suggests non-operative management with antibiotics and percutaneous drainage where laparoscopic expertise is not available, and recommends against routine interval appendicectomy in patients under 40 and in children.

Who do I escalate acute appendicitis to, and when?

Escalate every case of suspected acute appendicitis to the surgical registrar on admission, because the decision to operate, to image or to observe belongs to the on-call team rather than to the clerking doctor.

Escalate urgently for peritonitis, sepsis, a patient who is physiologically unwell, or a palpable mass, and involve the consultant early in pregnancy, in children and at the extremes of age.

Escalate again for the diagnosis that is not appendicitis. WSES recommends cross-sectional imaging before surgery for non-resolving right iliac fossa pain with normal investigations, and explorative laparoscopy if the pain is progressive or persistent after negative imaging.

In a patient of 40 or over treated non-operatively, WSES suggests both colonoscopy and an interval full-dose contrast-enhanced CT, because a caecal tumour can present as appendicitis.

What is the interviewer listening for in an appendicitis scenario?

The interviewer in an acute appendicitis scenario is listening for a named score, ultrasound before CT, the 24-hour rule, and a candidate who has thought about the differential rather than assuming the diagnosis.

  • A pregnancy test named explicitly in any woman of childbearing age
  • The AIR or AAS score named, with the Alvarado caveat understood
  • Ultrasound first, with low-dose CT reserved for negative ultrasound in young adults
  • Laparoscopic appendicectomy on the next available list within 24 hours, with a single preoperative antibiotic dose
  • The antibiotics-first option discussed with its 39% five-year recurrence figure and the appendicolith exception

What are the common mistakes in an appendicitis answer?

The commonest mistake in an acute appendicitis answer is going straight to CT for a young patient, when WSES puts ultrasound first and low-dose CT second in adolescents and young adults.

The second is quoting the Alvarado score as though it confirms the diagnosis, when WSES suggests against using it for that purpose in adults and prefers the AIR and AAS scores.

The third is a thin differential. Right iliac fossa pain in a young woman is gynaecological until proven otherwise, and in an older patient it can be a caecal tumour, diverticulitis or a perforated ulcer tracking down the right paracolic gutter.

How this comes up at the CST interview

Acute appendicitis usually arrives as a straightforward emergency department referral, and the panel uses it to test structure rather than obscurity: assess, score, image, consent, operate, consent again for the complications.

The panel then pushes on one axis, typically the pregnant patient, the normal-looking appendix at laparoscopy, the patient who wants antibiotics instead, or the elderly patient with a mass.

The coresurgeryinterview question bank has scored appendicitis scenarios among its 299 questions, with AI-marked spoken practice for the consent and management structure: /Question-Bank/Sample-Questions.