United States Medical Licensing Examination (USMLE) Surgery, Emergency, and Acute Care Syllabus

What is Beck's triad and what condition does it indicate?

Hypotension, muffled heart sounds, and jugular venous distention — indicating cardiac tamponade. Pulsus paradoxus may also be present.

Which causes of acute abdomen classically produce pain out of proportion to physical exam findings?

Acute mesenteric ischemia and early bowel strangulation/volvulus. Severe pain with a relatively benign abdomen should prompt suspicion of ischemia.

What distinguishes visceral from parietal (somatic) abdominal pain?

Visceral pain is dull, poorly localized, and midline (referred to the embryologic origin). Parietal pain is sharp, well-localized, and worsened by movement due to peritoneal irritation.

What pattern of referred pain suggests diaphragmatic irritation (e.g., from blood or air)?

Ipsilateral shoulder pain (Kehr sign with splenic injury/subdiaphragmatic blood), via the phrenic nerve (C3-C5).

What is the classic sequence of symptoms in acute appendicitis?

Periumbilical pain (visceral) followed by anorexia and nausea, then migration to RLQ/McBurney point (parietal) with fever and localized rebound tenderness.

Name three eponymous physical signs of appendicitis and what they test.

Rovsing sign (RLQ pain with LLQ palpation), psoas sign (pain on right hip extension, retrocecal appendix), and obturator sign (pain on internal rotation of flexed right hip, pelvic appendix).

What are the classic plain-film findings of bowel perforation versus large bowel obstruction?

Perforation: free air under the diaphragm (pneumoperitoneum). Large bowel obstruction: dilated colon; sigmoid volvulus shows a 'coffee bean'/inverted-U loop pointing to the RUQ.

What is Charcot triad and Reynolds pentad in cholangitis?

Charcot triad: RUQ pain, fever, and jaundice (ascending cholangitis). Reynolds pentad adds hypotension and altered mental status, indicating suppurative cholangitis.

What are Cullen and Grey Turner signs, and what condition do they suggest?

Cullen sign (periumbilical ecchymosis) and Grey Turner sign (flank ecchymosis) suggest retroperitoneal hemorrhage, classically severe necrotizing pancreatitis.

What is Courvoisier sign and what does it imply?

A palpable, nontender, distended gallbladder with painless jaundice — implies malignant distal biliary obstruction (e.g., pancreatic head carcinoma) rather than gallstones.

What is the most common location of colorectal cancer presenting with obstruction, and how do right- vs left-sided cancers differ in presentation?

Obstruction is more common with left-sided/sigmoid cancers (narrower lumen, solid stool), presenting with change in caliber/obstruction. Right-sided cancers present with occult bleeding and iron-deficiency anemia.

Differentiate the anatomy of direct, indirect, and femoral hernias.

Indirect: through the deep inguinal ring, lateral to inferior epigastric vessels (congenital, common). Direct: through Hesselbach triangle, medial to the vessels. Femoral: below the inguinal ligament, highest incarceration risk, more common in women.

Which hernia type is most likely to incarcerate/strangulate and warrants prompt repair?

Femoral hernias (narrow, rigid neck), and more broadly any hernia with small/tight defect. Femoral hernias should be repaired electively even if asymptomatic due to high strangulation risk.

What ankle-brachial index (ABI) value indicates peripheral arterial disease, and which value suggests critical limb ischemia?

ABI <0.9 is diagnostic of PAD; 0.4-0.9 with claudication; <0.4 indicates critical limb ischemia/rest pain. ABI >1.3 suggests noncompressible calcified vessels (e.g., diabetes).

What are the '6 Ps' of acute arterial limb ischemia?

Pain, Pallor, Pulselessness, Paresthesia, Poikilothermia (cold), and Paralysis. Paralysis and paresthesia are late, ominous signs requiring emergent revascularization.

What is the abdominal aortic aneurysm (AAA) diameter threshold for elective repair, and the classic ruptured-AAA triad?

Repair at ≥5.5 cm (or rapid growth >0.5 cm/6 months, or symptomatic). Ruptured AAA triad: hypotension, pulsatile abdominal mass, and back/flank pain.

What is the most common cause of primary hyperparathyroidism and its classic biochemical profile?

A solitary parathyroid adenoma. Profile: hypercalcemia with elevated (or inappropriately normal) PTH and low phosphate. Symptoms: 'stones, bones, groans, psychiatric moans.'

What is the triad of management priorities before resecting a pheochromocytoma?

Alpha-blockade first (e.g., phenoxybenzamine) for 7-14 days, then beta-blockade if needed, with volume expansion. Beta-blockade before alpha-blockade risks unopposed alpha vasoconstriction and hypertensive crisis.

What are the most common causes of a benign breast mass in a young woman versus a malignant mass in an older woman?

Young woman: fibroadenoma (firm, mobile, well-circumscribed). Older woman: invasive ductal carcinoma (hard, fixed, irregular). Any new dominant mass >30 yr needs triple assessment.

What is the triple assessment for a breast lump?

Clinical examination, imaging (mammography and/or ultrasound), and pathology (core needle biopsy/FNA). Concordance of all three guides management.

What organisms most commonly cause necrotizing soft tissue infection, and what is the definitive treatment?

Polymicrobial (type I) or Group A Streptococcus/Clostridium (type II). Hallmarks: pain out of proportion, crepitus, skin necrosis, systemic toxicity. Treatment is emergent surgical debridement plus broad-spectrum antibiotics.

What are the shockable versus non-shockable rhythms in cardiac arrest?

Shockable: ventricular fibrillation and pulseless ventricular tachycardia (treat with defibrillation). Non-shockable: asystole and pulseless electrical activity (PEA) — treat with CPR/epinephrine, not shock.

What are the reversible causes of cardiac arrest (Hs and Ts)?

Hs: Hypoxia, Hypovolemia, Hydrogen ion (acidosis), Hypo/Hyperkalemia, Hypothermia. Ts: Tension pneumothorax, Tamponade, Toxins, Thrombosis (pulmonary), Thrombosis (coronary).

What are the high-quality CPR targets for rate, depth, and compression-ventilation ratio in adults?

Rate 100-120/min, depth 2-2.4 inches (5-6 cm), full recoil, minimal interruptions; 30:2 compressions-to-ventilations without an advanced airway.

What is the antidote for acetaminophen overdose and how is treatment timing guided?

N-acetylcysteine (NAC); most effective within 8 hours of ingestion. Treatment is guided by plotting the 4-hour (or later) serum level on the Rumack-Matthew nomogram.

Match the antidotes: opioids, benzodiazepines, organophosphates, and beta-blockers.

Opioids → naloxone; benzodiazepines → flumazenil (use cautiously); organophosphates → atropine plus pralidoxime; beta-blockers → glucagon (and calcium/high-dose insulin for calcium-channel blockers).

What is the anion gap formula and a mnemonic for high-anion-gap metabolic acidosis?

Anion gap = Na − (Cl + HCO3); normal 8-12. MUDPILES: Methanol, Uremia, DKA, Propylene glycol, Iron/Isoniazid, Lactic acidosis, Ethylene glycol, Salicylates.

How is total body surface area (TBSA) burned estimated in adults, and what is the Parkland formula?

Rule of Nines (head 9%, each arm 9%, each leg 18%, anterior/posterior trunk 18% each, perineum 1%). Parkland: 4 mL × weight(kg) × %TBSA lactated Ringer's over 24 hr, half in first 8 hr from time of injury.

What are the signs of carbon monoxide poisoning and inhalation injury, and the treatment for CO?

Cherry-red skin, headache, normal PaO2 but falsely normal pulse oximetry; carbonaceous sputum/facial burns suggest inhalation injury. Treat CO with 100% oxygen (hyperbaric for severe/pregnancy).

How do you distinguish heat exhaustion from heat stroke?

Heat exhaustion: core temp <40°C with intact mental status, sweating. Heat stroke: core temp >40°C (104°F) with CNS dysfunction (confusion, seizures) — a medical emergency requiring rapid cooling.

What Glasgow Coma Scale score defines severe traumatic brain injury and warrants intubation?

GCS ≤8 ('8 = intubate'). GCS components: Eye (4), Verbal (5), Motor (6), total 3-15; 9-12 moderate, 13-15 mild TBI.

What is Cushing's triad and what does it signify?

Hypertension (widened pulse pressure), bradycardia, and irregular respirations — signifying raised intracranial pressure and impending brain herniation. Requires emergent measures to lower ICP.

What CT and clinical features distinguish epidural from subdural hematoma?

Epidural: biconvex/lens-shaped, does not cross sutures, middle meningeal artery, classic lucid interval. Subdural: crescent-shaped, crosses sutures, bridging veins, common in elderly/alcoholics.

What are the START triage categories and the color codes used in mass-casualty incidents?

Red (immediate, life-threatening but salvageable), Yellow (delayed), Green (minor/walking wounded), and Black (expectant/deceased). START uses respirations, perfusion, and mental status to sort.

What is the core principle that differentiates disaster/mass-casualty triage from everyday emergency care?

It shifts from doing the most for each individual to doing the greatest good for the greatest number — prioritizing salvageable patients and rationing limited resources, sometimes designating severely injured as expectant.