ACUTE APPENDICITIS

✓ Medically ReviewedDISEASEID: MDBT0111🚨 TRIAGE: EMERGENCYICD-10: K35

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Definition

CLINICAL DEFINITION

Acute appendicitis is acute bacterial inflammation (sudden germ swelling) of the vermiform appendix (finger-like pouch off caecum). It follows luminal obstruction (inner channel block) with bacterial overgrowth and rising wall pressure. Ischaemia (poor blood flow) with necrosis (tissue death) follows without timely care. It causes migratory belly pain with fever and vomiting. Perforation (burst wall) with peritonitis (lining infection) may develop.

IN PLAIN ENGLISH

The appendix is a small pouch off the large bowel. It gets blocked and infected. This causes swelling and severe belly pain. Pain often moves to the lower right side. You need urgent hospital care to stop bursting.

COMMON MISCONCEPTION / WHAT IT DOES NOT MEAN

Acute appendicitis is not chronic belly ache without inflammation. It is not mesenteric adenitis (gland inflammation) alone though signs overlap. It is not ectopic pregnancy (womb-outside pregnancy) or ovarian twist alone though both cause right lower pain. It is not Crohn disease (bowel wall inflammation) or kidney stone pain alone. Confirm with migration pattern plus guarding with imaging.

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Word Breakdown

appendic-

=appendix

-itis

=inflammation

Literal Meaning: acute inflammation of the appendix

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Abbreviations

RIF=Right iliac fossa - lower right belly over appendix site

RLQ=Right lower quadrant - lower right belly zone in reports

McB=McBurney point - tender spot in right lower belly

WCC=White cell count - infection blood marker

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Synonyms & Variants

Acute suppurative appendicitis›Gangrenous appendicitis›Phlegmonous appendicitis›

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Category-Specific Context

Acute appendicitis is a Disease because it is acute infection with tissue injury and course. It has defined blockage causes with predictable perforation risk. It shows signs (exam findings) needing disease-level treatment. It is not a Symptom (felt complaint) or test alone. Care targets source control with surgery, not pain relief alone.

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Clinical Context & Usage

CLINICAL SETTINGS

Emergency DepartmentAcute Surgical Assessment UnitGeneral Surgery WardPaediatric Emergency DepartmentMaternity Assessment Unit for Pregnant Patients

USAGE & DOCUMENTATION NOTES

Use acute appendicitis for migratory pain with right lower tenderness and systemic upset. The label triggers surgical review with scoring (risk tools) and imaging. Document onset with migration plus appetite loss, nausea and fever. Reassess often because early signs are subtle. Flag atypical cases in children, elderly and pregnancy.

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Primary Causes & Pathophysiology

PATHOPHYSIOLOGY

Luminal obstruction (inner channel block) traps mucus (lining fluid) with bacteria inside appendix. Overgrowth raises inner pressure and impairs venous outflow (blood leaving tissue). Wall ischaemia (poor supply) with ulceration (lining sores) allows bacterial invasion. Full-thickness death weakens wall toward perforation (burst hole). Local leak forms phlegmon (inflamed mass) or abscess (pus pocket). Free rupture causes peritonitis (lining infection) with sepsis (body-wide infection response).

PRIMARY CAUSES

Faecolith with inspissated stool blocking lumen

Hard stool stone traps mucus with bacteria inside channel. Rising pressure impairs blood flow and invites invasion

Lymphoid hyperplasia in children and young adults

Swollen immune tissue narrows channel after viral illness. Trapped flow allows overgrowth with wall ischaemia

Parasitic obstruction including Enterobius

Worms or eggs block narrow lumen and irritate lining. Obstruction with surface injury promotes infection

Appendiceal tumour including carcinoid and adenocarcinoma

Growth narrows or blocks lumen slowly in older adults. Chronic block leads to infection with higher burst risk

Crohn disease with caecal inflammation

Bowel wall swelling compresses appendix base and blocks drainage. Poor drainage with ulceration allows bacterial entry

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Epidemiology

Prevalence:Acute appendicitis is common in emergency surgical practice worldwide. It leads acute belly emergencies needing operation. Peak burden falls in teens and young adults. Delays raise burst and abscess rates.

Age Group:All ages can develop appendicitis from childhood to old age. Peak occurs in teens and twenties with immune-tissue blockage. Children show rapid course with vague signs and higher burst risk. Elderly and pregnant patients show atypical signs with delayed diagnosis.

Geographic Distribution:Acute appendicitis occurs worldwide in all health systems. No climate or region prevents disease. Patterns follow surgery and imaging access rather than biology alone. Detection tracks clinical review with scan availability.

Red Flags & Triage ★

TRIAGE LEVEL

🚨 EMERGENCY

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

Perforation with generalised peritonitis and sepsis
Ectopic pregnancy with rupture and shock
Ovarian torsion with ischaemic ovary
Appendiceal abscess needing drainage rather than immediate surgery
Crohn disease with fistula mimicking appendicitis
Appendiceal tumour in older adults

URGENT EVALUATION TRIGGERS

Rigid belly with guarding and rebound suggesting perforation
Low pressure with fast pulse and confusion suggesting sepsis
High fever with worsening pain beyond 24 hours
Vomiting with inability to keep fluids down
Pregnancy with right-sided pain and fever

Contraindications & Precautions

SPECIAL PRECAUTIONS

Avoid laxatives that may raise pressure and burst risk
Use pregnancy-adapted imaging with ultrasound first then MRI to limit radiation
Watch children and elderly closely for rapid decline with atypical signs
Review bleeding and infection risk before urgent anaesthesia and surgery

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Perforation with generalised peritonitis
Appendiceal abscess with walled pus
Appendiceal phlegmon with inflamed mass
Sepsis with shock
Adhesive bowel obstruction after healing or surgery
Wound infection with intra-abdominal collection after removal

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Confused With (LASA & DDx) ★

LEXICAL (LASA) — SIMILAR NAMES

Epiploic appendagitis

Shares appendix root with right lower pain but is fat-tag twist, not appendix infection

Mesenteric adenitis

Mimics with fever and right lower pain but is node inflammation with gland swelling, not appendix infection

Perityphlitis

Old term for caecal inflammation overlapping appendix area, but not acute appendix infection itself

CLINICAL DIFFERENTIAL DIAGNOSES (DDx)

Mesenteric adenitis

Key Distinguishing Feature: Recent sore throat with generalised nodes and less localised guarding favours gland disease

Ectopic pregnancy

Key Distinguishing Feature: Positive pregnancy test with bleeding and cervical motion pain favours ruptured ectopic

Pelvic inflammatory disease

Key Distinguishing Feature: Bilateral lower pain with discharge and cervical tenderness favours pelvic infection

Ovarian torsion

Key Distinguishing Feature: Sudden severe one-sided pain with vomiting and tender ovary lump favours twist

Meckel diverticulitis

Key Distinguishing Feature: Similar midgut pain but painless bleeding history favours Meckel pouch

Crohn disease

Key Distinguishing Feature: Chronic diarrhoea with weight loss and perianal disease favours bowel inflammation

Urinary infection with pyelonephritis

Key Distinguishing Feature: Burning urine with loin pain and urine white cells favours kidney infection

Renal colic

Key Distinguishing Feature: Colicky loin-to-groin pain with blood in urine and restlessness favours stone

Acute cholecystitis

Key Distinguishing Feature: Right upper pain with Murphy arrest and gallstone on scan favours gallbladder

Perforated peptic ulcer

Key Distinguishing Feature: Sudden upper pain with rigid board-like belly and free air favours perforated ulcer

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Clinical Pearls

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Check McBurney tenderness with Rovsing, psoas and obturator signs together. Single signs miss retrocaecal disease behind caecum and pelvic positions.

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Use Alvarado and AIR scores to guide imaging, not replace it. Watch low scores closely while pushing high scores to scan and surgery.

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Scan atypical cases early with ultrasound first in children and pregnancy. Use CT in unclear adults and MRI in pregnancy to limit radiation.

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Give fluids, antibiotics and analgesia promptly while arranging surgery. Analgesia does not hide signs and eases accurate examination.

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Suspect perforation with fever beyond 48 hours plus rigid belly or mass. Arrange urgent surgical review for abscess, phlegmon or free leak.

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Example Usage & SOAP

CLINICAL SENTENCE

""22-year-old with pain moving from navel to right lower belly has acute appendicitis.""

IN A SOAP NOTE

S: 22-year-old with belly ache shifting to right lower quadrant, appetite loss and nausea, no bleeding. O: Temp 38.1C, BP 118/72, HR 108, RR 20, SpO2 98 percent on air, RIF tenderness with guarding and rebound, Rovsing positive. A: Acute appendicitis likely uncomplicated. P: Nil by mouth, fluids with antibiotics and analgesia per protocol, surgical review with ultrasound then CT when unclear, pregnancy test done.

DIFFERENTIAL DIAGNOSIS CONTEXT

Migratory navel-to-right-lower pain with guarding favours appendicitis over gland disease. Sore throat with generalised nodes favours mesenteric adenitis. Bleeding with positive pregnancy test favours ectopic pregnancy. Burning urine with loin pain favours kidney infection. Check migration with guarding, fever and pregnancy status.

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Classifications & Scoring

SCORING TOOL

Alvarado Score

Uses migration with appetite loss, nausea, tenderness, fever and white cells to stratify risk and guide imaging

SCORING TOOL

Appendicitis Inflammatory Response Score

Combines pain, tenderness, white cells, CRP and neutrophils to grade risk for observation versus imaging versus surgery

SCORING TOOL

RIPASA Score

Adds age, sex, duration, guarding and labs to improve sensitivity in varied populations

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Prognosis

SHORT-TERM OUTCOME

Short term outlook is excellent with prompt surgery and antibiotics. Uncomplicated cases recover quickly with low risk. Perforation with peritonitis prolongs stay and needs drainage. Delay with sepsis raises early risk.

LONG-TERM PROGNOSIS

Long term outlook is excellent after full recovery. Most resume normal bowel function without lasting effects. Adhesions (internal scar bands) rarely cause later blockage. Stump inflammation after complete removal is rare.

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References & Coding

ICD-10 DIAGNOSTIC CODE

K35

LITERATURE CITATIONS & GUIDELINES

[1]WHO ICD-10 K35 Acute appendicitis

[2]World Society of Emergency Surgery appendicitis guidance

[3]Harrison's Principles of Internal Medicine acute abdomen chapter

[4]NICE appendicitis clinical knowledge summary where applicable

MEDICAL DISCLAIMER — This content is intended for educational purposes and qualified healthcare professionals only. Always refer to current clinical diagnostic criteria, institutional protocols, and official guidelines. Medobo is not responsible for clinical decisions made based on this content.

ACUTE APPENDICITIS

Definition

Word Breakdown

Abbreviations

Synonyms & Variants

Category-Specific Context

Clinical Context & Usage

Primary Causes & Pathophysiology

Epidemiology

Red Flags & Triage ★

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

URGENT EVALUATION TRIGGERS

Contraindications & Precautions

SPECIAL PRECAUTIONS

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Confused With (LASA & DDx) ★

Clinical Pearls

Example Usage & SOAP

Classifications & Scoring

Alvarado Score

Appendicitis Inflammatory Response Score

RIPASA Score

Prognosis

SHORT-TERM OUTCOME

LONG-TERM PROGNOSIS

Related Terms

References & Coding