Confusable diagnoses · PANCE / PANRE

Acute Appendicitis vs Acute Cholecystitis

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Acute Appendicitis and Acute Cholecystitis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Acute Appendicitis vs Acute Cholecystitis at a glance

  • Acute Appendicitis: Obstruction-driven inflammation of the appendix; classic periumbilical-to-RLQ pain with peritoneal signs.
  • Acute Cholecystitis: Inflammation of the gallbladder, most often from a stone obstructing the cystic duct.

Try two board-style questions on Acute Appendicitis vs Acute Cholecystitis

Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.

Question 1GastrointestinalMedium
A 19-year-old man has periumbilical pain that migrates to the right lower quadrant with anorexia and low-grade fever. Which of the following best explains the initial event?
  • AObstruction of the appendiceal lumen
  • BTerminal ileitis from Crohn disease
  • CInflammation of a Meckel diverticulum
  • DMesenteric lymphadenitis from a virus
Reveal answer & full explanation
Correct answer: A — Obstruction of the appendiceal lumen
  • AObstruction of the appendiceal lumen✓
  • BTerminal ileitis from Crohn disease
  • CInflammation of a Meckel diverticulum
  • DMesenteric lymphadenitis from a virus

Why Obstruction of the appendiceal lumen is correct

  • Acute appendicitis begins with luminal obstruction by lymphoid hyperplasia or a fecalith.
  • Obstruction causes distention, bacterial overgrowth, venous congestion, and ischemia.
  • The visceral periumbilical pain migrates to the RLQ once the inflamed serosa irritates the parietal peritoneum, exactly as described.

Why the others are wrong

  • Mesenteric lymphadenitis from a virus — This RLQ mimic causes pain without the orderly periumbilical-to-RLQ migration and is preceded by a viral prodrome; this is the appendicitis-mimic trap.
  • Inflammation of a Meckel diverticulum — Meckel diverticulitis can imitate appendicitis but is far less common and is not the textbook cause of this migrating-pain syndrome; this is the zebra trap.
  • Terminal ileitis from Crohn disease — Crohn ileitis produces weeks to months of RLQ pain with diarrhea and weight loss rather than an acute periumbilical-to-RLQ migration over hours, so it does not explain the initiating event here.
Question 2GastrointestinalMedium
A 44-year-old woman has fever, right upper quadrant pain, and a positive Murphy sign. Ultrasound shows gallbladder wall thickening and pericholecystic fluid. Which of the following best explains the mechanism?
  • AAcalculous gallbladder wall ischemia
  • BCommon bile duct stone with cholangitis
  • CCystic duct obstruction by gallstone
  • DSphincter of Oddi dysfunction with reflux
Reveal answer & full explanation
Correct answer: C — Cystic duct obstruction by gallstone
  • AAcalculous gallbladder wall ischemia
  • BCommon bile duct stone with cholangitis
  • CCystic duct obstruction by gallstone✓
  • DSphincter of Oddi dysfunction with reflux

Why Cystic duct obstruction by gallstone is correct

  • Acute calculous cholecystitis results from a stone impacted in the cystic duct.
  • Obstructed bile distends the gallbladder, causing wall inflammation, edema, and the pericholecystic fluid seen on ultrasound.
  • A positive sonographic Murphy sign localizes the inflammation to the gallbladder.

Why the others are wrong

  • Common bile duct stone with cholangitis — A CBD stone causes cholangitis with jaundice and a dilated duct, not isolated gallbladder wall thickening with a Murphy sign; this is the biliary-level confusion trap.
  • Acalculous gallbladder wall ischemia — Acalculous cholecystitis occurs in critically ill or fasting patients, not a well outpatient with a stone-prone profile; this is the right-organ-wrong-mechanism trap.
  • Sphincter of Oddi dysfunction with reflux — Sphincter dysfunction causes biliary-type pain and abnormal liver tests, not gallbladder wall inflammation with pericholecystic fluid; this is the functional-disorder trap.
🔒 Free preview limit reached

Keep comparing — start your free trial

You've used your 2 free previews. Create your free account to see the full Acute Appendicitis vs Acute Cholecystitis comparison — plus all 514 diagnosis outlines, 7,200+ board-style questions, and an AI tutor. Your 7-day free trial includes everything, no credit card required.

Start your 7-day free trial → Sign in
Free to start · No credit card · Cancel anytime

Side-by-side comparison

FeatureAcute AppendicitisAcute Cholecystitis
At a glanceObstruction-driven inflammation of the appendix; classic periumbilical-to-RLQ pain with peritoneal signs.Inflammation of the gallbladder, most often from a stone obstructing the cystic duct.
Classic presentationPeriumbilical pain → migration to RLQ + anorexia + nausea + low-grade fever + RLQ tenderness with peritoneal signs.; Periumbilical pain migrating to RLQ over 12-24 h (visceral → somatic); Anorexia (highly sensitive); Nausea and vomiting (after onset of pain — unlike gastroenteritis where vomiting precedes pain); Low-grade fever;…Postprandial RUQ pain lasting >6 h with fever, leukocytosis, and positive Murphy sign.; Constant, severe RUQ or epigastric pain lasting >6 h (vs <6 h in biliary colic); Radiation to right shoulder or interscapular area; Nausea and vomiting; Fever and chills; Anorexia; RUQ tenderness with positive Murphy sign (inspiratory arrest on…
Workup / key labsClinical diagnosis supported by imaging. Histopathology confirms post-operatively.; CBC — mild to moderate leukocytosis (10-18,000) with left shift; very high WBC suggests perforation; BMP, CRP; Urinalysis — exclude UTI; mild pyuria/hematuria possible from inflamed appendix adjacent to ureter; Pregnancy test in women of childbearing age…Tokyo Guidelines (TG18): (A) local signs — Murphy sign, RUQ mass/pain/tenderness; (B) systemic signs — fever, leukocytosis, elevated CRP; (C) imaging characteristic of cholecystitis. Definite diagnosis requires 1 from A + 1 from B + imaging.; CBC — leukocytosis with left shift; BMP; LFTs — mildly elevated AST/ALT and alk phos (~30%);…
ImagingCT abdomen/pelvis with contrast — modality of choice in adults; sensitivity and specificity >95%; findings: dilated appendix >6 mm, wall thickening, periappendiceal fat stranding, fluid, abscess, fecalith; Ultrasound — first-line in children and pregnant women to avoid radiation; operator-dependent; MRI — alternative in pregnancy if…RUQ ultrasound — first-line; findings: gallstones, gallbladder wall thickening >3 mm, pericholecystic fluid, sonographic Murphy sign, distended gallbladder; Hepatobiliary iminodiacetic acid (HIDA) scan — most sensitive/specific; non-visualization of gallbladder after 1-4 h confirms cystic duct obstruction; used when ultrasound…
First-line treatmentNPO, IV fluids, analgesia, antiemetics; IV antibiotics covering Gram-negative and anaerobic flora — piperacillin-tazobactam, ceftriaxone + metronidazole, or ertapenem; administer pre-operatively; Laparoscopic appendectomy — standard of care; lower wound infection rate and faster recovery vs open; Open appendectomy — alternative when…NPO, IV fluids, analgesia (NSAIDs and opioids; morphine traditionally avoided over sphincter of Oddi concerns but clinically used); IV antibiotics — piperacillin-tazobactam, ceftriaxone + metronidazole, or ertapenem (broaden for severity); Early laparoscopic cholecystectomy — within 72 h preferred; lower morbidity (11.8% vs 34.4%),…

Drill Acute Appendicitis vs Acute Cholecystitis questions on FirstPassPA

Turn this comparison into retention. 7,200+ board-style questions with an AI tutor that explains every answer — free to start, no card required.

Answer the 2 free questions above → Get today's free question →

Full outlines

Acute Appendicitis Acute Cholecystitis All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.