Abdominal Surgery: Appendicitis & Cholecystitis for USMLE
This module focuses on two common surgical emergencies: appendicitis and cholecystitis. Understanding their pathophysiology, clinical presentation, diagnostic approaches, and management is crucial for success on the USMLE.
Appendicitis: The Inflamed Appendix
Appendicitis is the inflammation of the appendix, a small, finger-like pouch attached to the large intestine. It is the most common surgical emergency worldwide, particularly in young adults.
Adults: Fecaliths. Children/Adolescents: Lymphoid hyperplasia.
Clinical Presentation of Appendicitis
The classic presentation of appendicitis involves a migratory pain pattern, anorexia, nausea, and vomiting.
The hallmark symptom of appendicitis is abdominal pain. It typically begins as periumbilical or epigastric pain that is poorly localized. Within 12-24 hours, the pain migrates to the right lower quadrant (RLQ), becoming sharper and more localized as the inflammation irritates the parietal peritoneum. Associated symptoms often include anorexia (loss of appetite), nausea, and vomiting. Fever is usually low-grade initially but can increase with complications. Physical examination may reveal tenderness at McBurney's point, rebound tenderness, and guarding in the RLQ. Specific signs like Rovsing's sign (palpation of the left lower quadrant causes pain in the right lower quadrant), psoas sign (pain on passive extension of the right hip), and obturator sign (pain on passive internal rotation of the flexed right hip) can aid in diagnosis.
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Starts periumbilical/epigastric, then migrates to the right lower quadrant.
Diagnosis and Management of Appendicitis
Diagnosis relies on a combination of clinical findings, laboratory tests, and imaging. The definitive treatment is appendectomy.
| Diagnostic Modality | Role in Appendicitis Diagnosis |
|---|---|
| History & Physical Exam | Essential for initial suspicion; migratory pain, anorexia, RLQ tenderness are key. |
| Laboratory Tests | Elevated WBC count (leukocytosis) with a left shift is common, but not always present. Urinalysis to rule out UTI. |
| Imaging (Ultrasound) | Useful in children and pregnant women; can visualize thickened appendix, fluid, or appendicolith. |
| Imaging (CT Scan) | Gold standard in adults; highly sensitive and specific for appendicitis, can detect complications like abscess or perforation. |
Appendectomy is the definitive treatment. It can be performed laparoscopically or via an open incision. Prompt surgical intervention is crucial to prevent complications.
Cholecystitis: Inflammation of the Gallbladder
Cholecystitis is inflammation of the gallbladder, most commonly caused by gallstones obstructing the cystic duct.
Gallstones obstructing the cystic duct.
Clinical Presentation of Cholecystitis
The classic presentation includes right upper quadrant (RUQ) pain, fever, and leukocytosis.
Pain is typically severe, constant, and located in the right upper quadrant (RUQ) or epigastrium. It may radiate to the right shoulder or scapula. The pain often begins after a fatty meal and can last for several hours. Associated symptoms include nausea, vomiting, and fever. On physical examination, patients may have RUQ tenderness, a positive Murphy's sign (inspiratory arrest upon palpation of the RUQ), and guarding. Jaundice is usually absent unless there is associated choledocholithiasis (stones in the common bile duct).
Inspiratory arrest upon palpation of the right upper quadrant, indicating gallbladder inflammation.
Diagnosis and Management of Cholecystitis
Diagnosis is confirmed with imaging, and the primary treatment is cholecystectomy.
| Diagnostic Modality | Role in Cholecystitis Diagnosis |
|---|---|
| History & Physical Exam | RUQ pain, fever, positive Murphy's sign are highly suggestive. |
| Laboratory Tests | Elevated WBC count, elevated liver enzymes (AST, ALT, ALP, GGT) and bilirubin may be present, especially if common bile duct is involved. |
| Imaging (Ultrasound) | The imaging modality of choice. Can visualize gallstones, thickened gallbladder wall, pericholecystic fluid, and cystic duct obstruction. |
| HIDA Scan (Cholescintigraphy) | Used when ultrasound is equivocal; can confirm cystic duct obstruction if the gallbladder is not visualized. |
The definitive treatment for acute cholecystitis is cholecystectomy. Laparoscopic cholecystectomy is the preferred approach due to faster recovery and fewer complications. Early surgical intervention is recommended.
Key Differences and Overlap
While both are common abdominal surgical emergencies, appendicitis and cholecystitis have distinct presentations and locations of pathology.
| Feature | Appendicitis | Cholecystitis |
|---|---|---|
| Primary Organ | Appendix | Gallbladder |
| Typical Pain Location | Right Lower Quadrant (migratory) | Right Upper Quadrant (radiates to shoulder) |
| Key Physical Sign | McBurney's point tenderness | Murphy's sign |
| Common Cause | Lumen obstruction (fecalith, lymphoid hyperplasia) | Cystic duct obstruction by gallstones |
| Diagnostic Imaging | CT Scan (adults), Ultrasound (children/pregnant) | Ultrasound |
USMLE Integration Points
For the USMLE, focus on differentiating these conditions based on patient history, physical exam findings, and imaging. Understand the complications of each and the indications for surgical intervention.
Perforation leading to peritonitis.
Cholangitis (infection of the bile ducts) or jaundice.
Learning Resources
Provides a comprehensive overview of appendicitis, including symptoms, causes, risk factors, diagnosis, and treatment from a reputable medical institution.
Offers detailed information on cholecystitis, covering its causes, symptoms, diagnosis, and management strategies.
A clinical decision support resource providing in-depth, evidence-based information on appendicitis, ideal for understanding nuances and management guidelines.
An authoritative resource for detailed understanding of acute cholecystitis, including pathophysiology, diagnosis, and treatment options.
A video lecture specifically designed for USMLE preparation, covering appendicitis with a focus on high-yield concepts.
A targeted video review of cholecystitis, tailored for USMLE Step 1 exam preparation, highlighting key clinical features and management.
Explains the surgical anatomy of the appendix, which is crucial for understanding surgical approaches and potential complications.
Details the surgical anatomy of the gallbladder, essential for comprehending cholecystectomy and related procedures.
Provides patient-focused information on appendicitis diagnosis and management from a leading surgical organization.
An overview of gallbladder diseases, including cholecystitis, from the perspective of the American College of Surgeons.