Emergency Ultrasound (POCUS) Atlas
Diagnostic bedside ultrasound curriculum across 13 core clinical domains. High-resolution authentic sonograms with kinetic cine loop scrubbing, probe positioning guides, anatomical label overlays, and Board Pearls.
Resuscitation & Trauma: The E-FAST Exam
The extended Focused Assessment with Sonography for Trauma (E-FAST) evaluates 5 acoustic windows to identify hemoperitoneum, hemopericardium, pneumothorax, and hemothorax in unstable trauma patients within 60 seconds.
In the RUQ, fluid layers in the inferior pole of the kidney (most dependent) before Morison's pouch. In the LUQ, fluid collects above the spleen under the diaphragm first due to the phrenicocolic ligament.
Sliding cephalad above the diaphragm evaluates the hemithoraces. Anechoic fluid above the diaphragm with continued visualization of thoracic vertebrae confirms positive Spine Sign (hemothorax).
Normal lung shows shimmering "ants on a log" sliding and Seashore sign on M-mode. Absent sliding + Barcode / Stratosphere sign suggests pneumothorax; visualizing the Lung Point is 100% pathognomonic.
1. Hepatorenal Space (Morison's Pouch / RUQ)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Coronal view at 8th–11th intercostal space, mid-to-posterior axillary line. Probe marker pointed toward patient's head. Sweep through superior liver, subhepatic space, and inferior pole of right kidney, then slide cephalad above the diaphragm.
Bright hyperechoic line of Glisson's capsule separating liver and kidney with NO dark intervening fluid. Diaphragm visible cephalad with normal mirror-image artifact of liver parenchyma above it.
Anechoic (jet black) stripe of free fluid in the subhepatic space, hepatorenal interface, or the inferior pole of the right kidney (most dependent part in a supine patient). Fluid above the diaphragm with a positive Spine Sign confirms hemothorax.
2. Splenorenal Recess (LUQ)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Posterior axillary line at 6th–9th intercostal space ('knuckles against the bed'). Probe marker to head. Angle through subdiaphragmatic splenic space, splenorenal interface, and slide cephalad into the left hemithorax.
Spleen and left kidney closely apposed; smooth left hemidiaphragm visible superiorly with aerated lung mirroring above it.
Anechoic fluid in the subdiaphragmatic space (fluid collects ABOVE the spleen before entering the splenorenal recess due to the phrenicocolic ligament). Fluid above the left diaphragm denotes left hemothorax.
3. Pelvic / Suprapubic Window
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Just superior to pubic symphysis. Obtain both transverse (marker to patient's right) and sagittal (marker to head) planes through a full bladder acoustic window.
Anechoic urine-filled bladder with smooth, sharply demarcated walls.
Anechoic fluid posterior to bladder in rectovesical pouch (males) or rectouterine pouch / Pouch of Douglas (females) in both sagittal and transverse planes. In a collapsed bladder, free fluid layers circumferentially around the dome.
4. Subxiphoid / Pericardial Space
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Flat against epigastrium angled shallowly toward left shoulder (30-degree angle to skin). Use patient's left hepatic lobe as an acoustic window to image four cardiac chambers.
Liver at top of screen; right ventricle resting against left lobe of liver; thin fibrous pericardium with no intervening anechoic space.
Anechoic fluid surrounding heart. Diastolic right ventricular (RV) collapse and late diastolic right atrial (RA) collapse confirm cardiac tamponade physiology.
5. Anterior Thoracic Windows (Extended / Pneumothorax & Hemothorax)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
High-frequency linear probe placed longitudinally at 2nd–4th intercostal spaces, midclavicular line (air rises anteriorly in a supine patient). Sweep inferiorly and posterolaterally for hemothorax.
B-mode: shimmering 'ants on a log' lung sliding at the hyperechoic pleural line between rib shadows ('bat sign'). M-mode: 'Seashore sign' (horizontal ocean waves in chest wall; granular sandy beach in aerated lung).
ABSENT lung sliding. M-mode: 'Barcode sign' or 'Stratosphere sign' (monotonous horizontal parallel lines with loss of granular beach pattern). Pathognomonic 'LUNG POINT' confirms pneumothorax transition zone. Hemothorax presents as fluid above the diaphragm with a positive Spine Sign.
Thoracic & Lung Ultrasound (BLUE Protocol)
The Bedside Lung Ultrasound in Emergency (BLUE) protocol evaluates anterior and posterolateral thoracic zones to rapidly diagnose acute pulmonary edema, COPD/asthma, pneumothorax, pneumonia, and pleural effusions within 3 minutes.
The acoustic landmark of the thorax: two adjacent rib shadows with posterior acoustic shadowing flanking the bright horizontal pleural line between them.
Horizontal, equidistant hyperechoic reverberation lines parallel to the pleural line, denoting physiological dry aeration. Prominent in normal lung, asthma, COPD, and PE.
Alveolar consolidation appears as lung hepatization (tissue-like echogenicity). Dynamic air bronchograms (moving with respiration) rule in pneumonia; Shred sign marks the irregular subpleural fractal border.
Anechoic fluid bounded by chest wall, ribs, and diaphragm forms the Quad sign. The atelectatic lower lobe undulating within the effusion creates the classic Jellyfish sign.
1. Pulmonary Edema & Interstitial Syndrome (B-Lines / 'Lung Rockets')
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Transverse and longitudinal scans across anterior and lateral chest zones (bilateral upper and lower intercostal spaces 2–5).
Predominance of horizontal, hyperechoic, equally spaced A-lines parallel to the pleural line, signifying normal physiological aeration.
Multiple (>= 3 per intercostal window bilaterally) discrete, vertical, hyperechoic laser-like comet-tail artifacts originating from the pleural line that extend to the bottom of the screen without fading and erase A-lines ('lung rockets'). Confluent B-lines produce a 'white lung' appearance.
2. Pleural Effusion & The Spine Sign
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Longitudinal scan in posterior axillary line at 8th–10th intercostal space, aiming cephalad above the diaphragm using the liver (right) or spleen (left) as an acoustic window.
Costophrenic angle is an acute sharp crevice; aerated lung obscures posterior thoracic vertebrae above the diaphragm (spine disappears cephalad to diaphragm due to air reflection).
Dependent anechoic fluid collection above the diaphragm; visualization of thoracic vertebral bodies extending cephalad past the diaphragm (The Spine Sign, pathognomonic for pleural fluid); floating, compressed atelectatic lung within fluid (Jellyfish sign) with Quad sign boundaries.
Focused Cardiac Ultrasound (FoCUS)
Standard FoCUS interrogation across 4 standard acoustic windows: Parasternal Long Axis (PLAX), Parasternal Short Axis (PSAX at aortic, mitral, and papillary levels), Apical 4-Chamber (A4C), and Subxiphoid 4-Chamber.
- PLAX (3rd/4th ICS LSB, marker right shoulder): LV, RVOT, LA, aortic valve, mitral valve, descending aorta.
- PSAX (Rotate 90° clockwise, marker left shoulder): Papillary muscle level shows "doughnut" circular LV; assesses regional wall motion & D-sign.
- A4C (Apex / 5th ICS anterior axillary, marker left): 4 chambers; LV vs RV sizing (normal RV ~2/3 LV).
- Subxiphoid 4C (Epigastrium angled to left shoulder): Liver window; best view for tamponade and pericardial effusion.
- Diastolic RV Collapse: Free wall indenting during ventricular filling (high specificity).
- Late Diastolic RA Collapse: RA inversion lasting >1/3 of cardiac cycle (earliest/most sensitive).
- Plethoric IVC: >2.1 cm with <50% inspiratory collapse.
- Effusion vs Fat Pad: Pericardial fluid is posterior to descending aorta; epicardial fat pad is anterior only and moves synchronously with myocardium.
- Hyperdynamic (EF >70%): Distributive / hypovolemic shock; walls touching in systole ("kissing papillary muscles").
- Normal (EF 55–70%): Brisk concentric contraction and anterior mitral leaflet opening.
- Severely Depressed (EF <30%): Cardiogenic shock; hypokinetic walls, dilated chamber.
- EPSS (E-Point Septal Separation): Distance from anterior mitral leaflet to septum in diastole. EPSS > 7 mm confirms reduced LVEF (<50%).
- RV:LV Ratio > 1:1: On A4C, RV expands larger than LV (normal is 2/3 size).
- McConnell's Sign: Akinesis of RV mid-free wall with preserved hyperdynamic apical sparing (94% specificity for acute massive PE).
- "D-Sign": Interventricular septal flattening compressing LV in PSAX (diastolic flattening = RV volume overload; systolic flattening = RV pressure overload).
- TAPSE < 16 mm: Reduced tricuspid annular plane systolic excursion indicates acute RV systolic failure.
Complete absence of cardiac wall motion and valve movement during 10-second pause. Highly predictive of non-survival in PEA/asystole.
Subtle, chaotic, disorganized myocardial quivering masquerading as asystole on ECG. Requires immediate defibrillation!
Organized cardiac contractility present on ultrasound despite no palpable peripheral pulse (profound hypotension/vasoplegia). Responsive to aggressive vasopressors and fluids.
1. Parasternal Long Axis (PLAX) & Pericardial Effusion
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Parasternal Long Axis (PLAX) at 3rd–4th intercostal space immediately left of sternum with indicator to patient's right shoulder.
Normal LVEF (> 55%); mitral valve anterior leaflet touches ventricular septum in diastole (EPSS < 7 mm); RV is approximately 2/3 the size of LV.
Cardiogenic Shock: Severely depressed global LV contractility with EPSS > 7 mm. Distributive/Hypovolemic: Hyperdynamic LV with kissing papillary walls. Pericardial Tamponade: Anechoic fluid tracking anterior to descending thoracic aorta with diastolic RV free wall collapse.
2. Apical 4-Chamber (A4C), RV Strain & McConnell's Sign
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Apical 4-Chamber (A4C) at cardiac apex (5th intercostal space, left anterior axillary line) directed toward patient's right shoulder with indicator to patient's left.
Conical LV forming apex; triangular RV approximately 2/3 the size of LV (RV:LV basal diameter ratio < 0.6); tricuspid valve inserts slightly more apical than mitral valve.
Acute RV dilatation with RV:LV basal ratio > 1:1; severe akinesis of the RV mid-free wall with preserved hyperdynamic apical contractility ('McConnell's sign'); interventricular septal flattening compressing LV ('D-sign' in PSAX).
Vascular: Aorta & IVC Hemodynamics
Rapid bedside assessment of abdominal aortic aneurysm (AAA), dissection flaps, and respiratory collapsibility of the inferior vena cava (IVC) to assess volume status and central venous pressure (CVP).
- Zone 1 (Celiac Axis): Proximal aorta immediately below diaphragm; normal diameter <2.5 cm.
- Zone 2 (SMA & Renal): Mid aorta at origin of superior mesenteric artery; normal <2.0 cm.
- Zone 3 (Infrarenal): Most common site for AAA (>90% occur infrarenal); normal <2.0 cm.
- Zone 4 (Iliac Bifurcation): Level of umbilicus; common iliacs normal <1.5 cm.
- Diagnostic Invariant: Diameter ≥ 3.0 cm (or >1.5× adjacent segment) confirms AAA. Always measure outer-wall to outer-wall!
- Mural Thrombus: Crescentic hypoechoic thrombus lining vessel wall; lumen-only measurement severely underestimates true aneurysm diameter!
- Intimal Dissection Flap: Linear, fluttering hyperechoic membrane dividing true and false lumens with color Doppler flow discrepancies.
- Retroperitoneal Hematoma: Ill-defined hypoechoic fluid collection tracking in retroperitoneum adjacent to aorta, denoting rupture.
Bedside IVC Collapsibility & Distensibility Calculator
Measured 2–3 cm caudal to cavoatrial junction1. Abdominal Aorta: Aneurysm (AAA) & Dissection Flap
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Curvilinear probe transversely in epigastrium; sweep sequentially through proximal, mid, and distal aorta down to the iliac bifurcation at the umbilicus. Measure in sagittal and transverse axes.
Smooth, pulsatile, non-dilated vessel anterior to spine and left of IVC. Normal diameter < 2.0 cm throughout (outer wall to outer wall).
Diameter >= 3.0 cm confirms abdominal aortic aneurysm (AAA). Intraluminal hypoechoic mural thrombus; mobile echogenic intimal flap in aortic dissection; periaortic hypoechoic hematoma indicates rupture.
2. Inferior Vena Cava (IVC) Collapsibility Index
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Subxiphoid longitudinal view of IVC entering the right atrium; measure diameter and respiratory variation 2–3 cm caudal to the cavoatrial junction.
IVC diameter 1.5–2.1 cm with > 50% collapsibility on quiet inspiration, correlating with normal central venous pressure (CVP 5–10 mmHg).
Hypovolemic/Distributive: Flat, slit-like IVC (< 2.1 cm) with > 50% inspiratory collapse correlates with low CVP (0–5 mmHg) and volume responsiveness. Obstructive/Cardiogenic: Plethoric, dilated IVC (> 2.1 cm) with < 50% collapse correlates with high CVP (10–20 mmHg).
Hepatobiliary & Right Upper Quadrant
Bedside RUQ ultrasound evaluates gallbladder anatomy (fundus, body, neck, main lobar fissure), portal triad ('Mickey Mouse' sign), cholelithiasis, acute calculous cholecystitis, and common bile duct (CBD) dilatation.
- Cholelithiasis: Mobile or impacted hyperechoic stone with clean posterior acoustic shadow.
- Wall Thickening: Anterior gallbladder wall > 3 mm measured in transverse axis.
- Sonographic Murphy's: Focal maximum tenderness directly over the fundus (highest PPV, >90%).
- Pericholecystic Fluid: Anechoic halo or double-rim wall edema.
- "Mickey Mouse" Sign: Short axis porta hepatis: Portal Vein (face), CBD (right ear/anterolateral), Hepatic Artery (left ear/anteromedial).
- Normal CBD: ≤ 4 mm. Add 1 mm per decade over age 40 (e.g., 70-yo normal up to 7 mm); up to 8–10 mm post-cholecystectomy.
- Obstruction Cutoff: CBD > 6 mm denotes choledocholithiasis or distal mass.
- Wall: Thin curvilinear hyperechoic anterior gallbladder wall.
- Echo: Thin anechoic fluid stripe of residual bile.
- Shadow: Dense hyperechoic surface of packed gallstones with prominent broad acoustic shadow behind it.
- Differential: Distinguish from porcelain gallbladder (calcified wall with shadow) and duodenal air (dirty shadowing).
1. Cholelithiasis with Posterior Acoustic Shadowing & WES Sign
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Subcostal sweep in sagittal and transverse planes; ask patient to take and hold a deep breath (left lateral decubitus positioning displaces bowel gas and shifts mobile calculi).
Anechoic, thin-walled (< 3 mm) pear-shaped lumen filled with homogenous bile without intraluminal echogenic foci or dependent debris.
Hyperechoic focus within gallbladder lumen demonstrating clean posterior acoustic shadowing. In a gallbladder completely filled with stones, the Wall-Echo-Shadow (WES) sign appears: curvilinear hyperechoic wall, thin anechoic bile stripe, hyperechoic stone surface, and broad acoustic shadow.
2. Acute Cholecystitis (Wall Thickening, Murphy's Sign & Pericholecystic Fluid)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Right subcostal sweep directly over gallbladder fundus and neck; measure anterior gallbladder wall in transverse plane perpendicular to ultrasound beam.
Gallbladder wall thickness <= 3.0 mm; smooth serosal margin; absence of pericholecystic fluid or focal probe tenderness.
Gallbladder anterior wall thickening > 3 mm, striated wall edema ('double rim' sign), pericholecystic fluid stripe, impacted neck stone, and positive sonographic Murphy's sign (focal maximum tenderness precisely when transducer compresses the visualized fundus).
Renal & Urinary Tract
Bedside renal ultrasound evaluates acute flank pain, nephrolithiasis, obstructive hydronephrosis grading (mild, moderate, severe), color Doppler ureteral jets, and acute urinary retention bladder volume calculations.
- Mild: Dilatation of the renal pelvis and calyces without parenchymal blunting ('bear claw' pattern).
- Moderate: Progressive pelvicalyceal blunting with preserved cortical thickness.
- Severe: Ballooning of calyces with marked cortical thinning and medullary compression.
- Nephrolithiasis: Hyperechoic stone with clean posterior acoustic shadow.
- Twinkle Artifact: Rapidly alternating red/blue mosaic color Doppler signal behind calculus; confirms stone when acoustic shadow is faint.
- Technique: Color Doppler over bladder trigone at ureterovesical junctions (UVJ).
- Normal: Periodic robust bursts every 10–30s.
- Obstruction: Absent jet on symptomatic side (or >3:1 asymmetry) confirms high-grade complete obstruction.
Bedside Bladder Volume & Retention Calculator
Formula: Length × Width × Height × 0.521. Normal Renal Corticomedullary Anatomy
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Coronal/longitudinal sweep along mid-to-posterior axillary line (right kidney: 8th–11th interspace using liver window; left kidney: 6th–9th interspace posterior axillary line).
Smooth reniform contour; homogenous hypoechoic renal cortex slightly less echogenic than adjacent liver/spleen; distinct triangular medullary pyramids; bright central echogenic renal sinus with compressed collecting system.
Loss of corticomedullary differentiation, cortical thinning (< 1 cm), or hyperechoic renal cortex indicating medical renal disease.
2. Obstructive Hydronephrosis (Pelvicalyceal Dilatation)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Longitudinal and transverse views of the kidney through renal pelvis; follow ureteropelvic junction (UPJ) and evaluate contralateral kidney for baseline comparison.
Central renal sinus is a compact, uniform hyperechoic oval without internal branching anechoic fluid pockets.
Interconnected, branching anechoic fluid collections expanding the renal pelvis and calyces ('bear claw' appearance). In severe obstruction, marked caliceal ballooning causes cortical blunting and medullary compression.
3. Transverse Urinary Bladder & Ureteral Jets (Color Doppler)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Low-frequency curvilinear probe placed transversely immediately cephalad to pubic symphysis, angled caudally into the true pelvis through a distended bladder. Activate Color Doppler over the trigone/ureterovesical junctions (UVJ).
Anechoic urine-filled bladder with thin (< 3 mm), smooth detrusor wall. Periodic, robust bursts of color flow (ureteral jets) entering obliquely from each ureterovesical junction (every 10–30 seconds) into the bladder lumen.
Complete absence of ureteral jets on the symptomatic side (or weak, continuous trickle) confirms high-grade ureteral obstruction. Direct visualization of hyperechoic calculus at the UVJ with acoustic shadowing and twinkle artifact on Color Doppler.
4. Urinary Retention & Bladder Wall Trabeculation
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Suprapubic placement obtaining maximum dimensions in transverse (width) and sagittal (depth and height) planes. Calculate bladder volume using the prolate ellipsoid formula: Width x Depth x Height x 0.52.
Smooth, uniform, thin bladder wall (< 3 mm distended, < 5 mm empty) without muscular hypertrophy, mucosal outpouchings, or post-void retention (PVR < 50 mL).
Markedly distended urinary bladder (> 300–500 mL in acute urinary retention) with thickened detrusor wall (> 5 mm) and irregular, corrugated intraluminal ridges (trabeculations) or bladder diverticula from chronic bladder outlet obstruction (BPH/stricture).
Obstetric & Gynecologic (1st Trimester Pelvic)
Bedside pelvic ultrasound evaluates first-trimester vaginal bleeding, suspected ectopic pregnancy, and acute pelvic pain to definitively confirm intrauterine pregnancy (IUP) or identify surgical emergencies.
- Gestational Sac (4.5–5 wks): Anechoic sac + double decidual sign; TVUS discriminative β-hCG is 1,500–2,000 mIU/mL.
- Yolk Sac (5.5 wks): Circular ring within sac; definitive proof of IUP (rules out ectopic pseudosac).
- Fetal Pole (≥6 wks): Embryo with cardiac activity. CRL ≥ 7 mm without cardiac flicker confirms non-viability.
- Empty Uterus: With positive β-hCG above discriminatory zone.
- Tubal Ring ("Bagel Sign"): Extrauterine echogenic ring in adnexa with Doppler "Ring of Fire".
- Free Fluid: Echogenic fluid in Pouch of Douglas or Morison's pouch (RUQ fluid confirms rupture).
- Enlarged Ovary (>4 cm): With heterogeneous central stromal edema.
- "String of Pearls": Multiple small peripheralized cortical follicles.
- Whirlpool Sign: Twisted vascular pedicle on grayscale/Doppler. Doppler flow can persist (dual blood supply).
1. Normal Early Intrauterine Pregnancy (IUP)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Transabdominal sagittal and transverse sweeps through full bladder acoustic window, followed by transvaginal interrogation of the endometrial stripe.
Thick hyperechoic decidualized endometrium containing a well-defined anechoic gestational sac with double decidual sign, a discrete round yolk sac (3–5 mm), and embryonic pole with cardiac flutter (> 100 bpm).
Empty uterine cavity with beta-hCG above discriminatory zone (1,500–2,000 mIU/mL transvaginal); intrauterine 'pseudosac' (thin-walled, central fluid collection lacking double decidual sign or yolk sac).
2. Tubal Ectopic Pregnancy & Adnexal Mass
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Sweeps lateral to uterine cornu to visualize fallopian tubes, adnexa, and pouch of Douglas (rectouterine recess).
Bilateral adnexa free of discrete masses, normal ovarian architecture with physiologic follicles, and absence of fluid in rectouterine pouch.
Empty uterine cavity despite positive pregnancy test; extrauterine adnexal mass with thick hyperechoic tubal ring ('tubal ring / bagel sign'); circumferential vascularity on Color Doppler ('ring of fire'); echogenic or anechoic free fluid in the rectouterine space or Morison's pouch.
3. Ovarian Torsion & Stromal Edema
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Endovaginal or transabdominal scan of bilateral adnexa with side-by-side ovarian dimension measurements; place Color/Spectral Doppler over ovarian stroma.
Normal ovarian volume (< 10 cm^3; length ~3–4 cm); homogenous central stroma with developing follicles; brisk arterial and low-resistance venous waveforms on spectral Doppler.
Unilaterally enlarged ovary (> 4 cm diameter or volume > 3x contralateral ovary) with heterogeneous stromal edema; multiple small peripheralized follicles ('string of pearls' sign); diminished or absent venous Doppler flow; whirlpool sign of twisted vascular pedicle.
Deep Vein Thrombosis (DVT)
The evidence-based 2-point and 3-point compression protocols evaluate the common femoral vein (CFV) at the saphenofemoral junction (SFJ), the femoral vein bifurcation, and the popliteal vein (PV) down to the trifurcation with > 98% sensitivity for proximal DVT.
- Complete Coaptation: Vein collapses 100% under gentle downward pressure (anterior and posterior walls touch).
- Key Stations: Common femoral vein at SFJ, deep femoral / femoral vein bifurcation, and popliteal fossa down to trifurcation.
- Transverse Axis Only: Compressing in longitudinal axis risks rolling off the vessel and falsely diagnosing patency!
- Acute DVT: Incompressible vein, direct hypoechoic intraluminal thrombus, dilated vein lumen, absent Doppler flow.
- Ruptured Baker's Cyst: Dissects into medial gastrocnemius mimicking DVT ('pseudothrombophlebitis'). POCUS identifies patent popliteal vein and cystic inter-tendinous fluid collection.
1. Common Femoral Vein & Saphenofemoral Junction (SFJ)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Transverse orientation at inguinal crease. Locate femoral artery (lateral, pulsatile) and common femoral vein (medial). Follow to saphenous confluence and femoral vein / deep femoral bifurcation.
Complete coaptation of anterior and posterior venous walls under gentle probe compression (vein winks out of sight while artery remains patent).
Failure of vein walls to touch (non-compressibility), with or without direct visualization of hyperechoic intraluminal thrombus or absent color Doppler flow.
2. Popliteal Vein Confluence
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Transverse view in popliteal fossa with patient's knee slightly flexed and hip externally rotated ('frog-leg').
Popliteal vein sits superficial to popliteal artery ('vein on top') and collapses 100% under downward pressure.
Non-compressible popliteal vein indicating proximal deep venous thrombosis requiring immediate therapeutic anticoagulation.
Soft Tissue, Abscess, & MSK
High-resolution superficial soft tissue ultrasound differentiates non-drainable cellulitis from drainable fluid collections (abscesses, popliteal cysts, hematomas), identifies foreign bodies, evaluates tendon integrity, and guides bedside aspiration and pediatric surgical abdomen workups.
- Cellulitis: Thickened subcutaneous tissue with reticular fluid stranding surrounding hyperechoic fat ("Cobblestoning"). Medical management.
- Abscess: Discrete anechoic/hypoechoic cavity with posterior acoustic enhancement and dynamic "Squish Sign" (swirling purulent debris on compression). I&D indicated.
- Acoustic Shadowing: Wood, plastic, glass, and metal appear as hyperechoic surfaces with clean acoustic shadow or comet-tail reverberation.
- Inflammatory Halo: Hypoechoic rim of edema/granulation tissue surrounding object after >24h.
- Rupture: Disruption of normal hyperechoic parallel fibrillar tendon architecture with fiber retraction and hypoechoic hematoma gap.
- Dynamic Test: Lack of tendon movement across gap on passive ankle dorsiflexion/plantarflexion confirms complete tear.
1. Cellulitis & Subcutaneous Edema (Cobblestoning)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Place linear transducer gently over area of erythema and induration using ample gel; compare with contralateral unaffected extremity for tissue symmetry.
Organized, hyperechoic dermis overlying thin, distinct hypoechoic subcutaneous fat lobules and bright fibrillar muscular fascia.
Echogenic, thickened subcutaneous tissue infiltrated by interconnected, reticular anechoic fluid channels surrounding hyperechoic fat lobules ('cobblestoning' or 'cracked pavement' appearance) with no discrete drainable fluid pocket.
2. Popliteal (Baker's) Synovial Cyst
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Transverse and longitudinal views of the medial popliteal fossa. Identify the medial head of the gastrocnemius muscle and semimembranosus tendon.
Tightly apposed muscular borders of semimembranosus and medial gastrocnemius with no cystic fluid collection or inter-tendinous distension.
Well-circumscribed, anechoic or hypoechoic cystic structure with a distinct 'neck' or 'beak' extending directly between the semimembranosus tendon and medial gastrocnemius head. Fluid may contain internal debris, septations, or synovitis.
3. Acute Appendicitis (Non-Compressible Blind-Ending Tube)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Graded compression technique over point of maximal RLQ tenderness (McBurney's point), sweeping slowly to displace overlying bowel gas down to psoas muscle and iliac vessels.
Compressible bowel loops with visible active peristalsis; normal appendix is rarely visualized, compressible, and measures <= 6 mm in outer diameter.
Blind-ending, non-compressible, aperistaltic tubular structure in longitudinal axis (> 6 mm outer diameter); 'target' or 'bullseye' sign in transverse axis; hyperechoic appendicolith with acoustic shadow; hyperemic rim on color Doppler ('ring of fire').
4. Pediatric Intussusception (Target / Doughnut Sign)
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Systematic 'lawnmower' sweep of abdomen starting at RLQ along ascending, transverse, and descending colon; inspect right hypochondrium / subhepatic space.
Pliable, thin-walled bowel loops with active peristalsis and no invaginated concentric ring architecture.
Transverse axis: 'Target sign' or 'Doughnut sign' consisting of concentric alternating hyperechoic and hypoechoic rings formed by the intussuscipiens (outer bowel) enclosing the intussusceptum (inner bowel) and mesenteric fat. Longitudinal axis: 'Pseudokidney' or 'sandwich' sign.
Ocular Ultrasound
Rapid bedside identification of retinal detachment, vitreous hemorrhage, and non-invasive measurement of elevated intracranial pressure via optic nerve sheath diameter (ONSD).
Apply a generous mountain of sterile acoustic gel over a closed eyelid. Float the probe on the gel standoff with ZERO direct pressure on the globe to prevent worsening ruptured globe injuries.
- Retinal Detachment: Thick, hyperechoic membrane anchored to the optic disc and ora serrata; does not freely undulate with kinetic eye movements.
- Vitreous Hemorrhage / PVD: Fine, hazy echoes swirling freely like clothes in a "washing machine", completely unanchored to the optic nerve head.
Bedside Optic Nerve Sheath Diameter (ONSD) ICP Risk Estimator
Measured exactly 3.0 mm posterior to the retina1. Retinal Detachment vs. Vitreous Hemorrhage / PVD
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Copious sterile acoustic gel over closed upper eyelid. Gentle touch without pressure in transverse and sagittal sweeps across the vitreous chamber.
Posterior vitreous chamber is completely anechoic; smooth retina firmly applied to choroid and sclera.
Retinal Detachment: Thick, bright, hyperechoic membrane floating in vitreous space that is FIXED and ANCHORED to the optic disc and ora serrata; does not undulate freely with kinetic eye movements. Vitreous Detachment (PVD): Thin, wispy, undulating membrane unanchored to optic disc. Vitreous Hemorrhage: Swirling hazy debris ('washing machine sign').
2. Optic Nerve Sheath Diameter (ONSD) for Elevated ICP
Self-Assessment Active
Sonogram is visible. Determine whether findings represent normal baseline anatomy or pathological emergency findings before revealing the clinical diagnosis.
Probe Setup & Acoustic Window
Transverse plane through center of globe aligning optic nerve perpendicular to ultrasound beam. Measure sheath diameter exactly 3 mm posterior to the retina.
Optic nerve sheath diameter < 5.0 mm measured exactly 3 mm posterior to the globe retrobulbar surface.
ONSD > 5.0 mm (or > 5.8 mm in severe intracranial hypertension) indicates increased intracranial pressure (ICP > 20 mmHg) with > 95% sensitivity.
Procedural Ultrasound Guidance
Comprehensive bedside ultrasound guidance for vascular access (IJ central lines, radial arterial lines, deep peripheral IVs), fluid drainage (paracentesis, thoracentesis, lumbar puncture), and emergency regional nerve blocks.
1. Vascular Access Guidance
- Compressibility: IJ collapses 100% under gentle transducer pressure; carotid is rigid, non-compressible, and pulsatile.
- Anatomy: IJ is typically anterolateral to the carotid artery.
- Respiratory Variation: IJ changes caliber with respiration / Valsalva; carotid maintains constant diameter.
- Transverse (Out-of-Plane): Dynamic needle-tip tracking; advance needle until vessel wall indents, then advance probe 1 mm, advance needle until bright hyperechoic flash enters lumen.
- Longitudinal (In-Plane): Entire needle shaft and tip visualized continuously entering anterior arterial wall.
- Target deep brachial or basilic veins at 1.0–1.5 cm depth.
- Select catheter length so that ≥ 65% of catheter remains inside vein lumen to prevent dislodgement and extravasation.
2. Fluid Drainage: Paracentesis, Thoracentesis & LP
1. Use curvilinear probe in LLQ (preferred due to thinner abdominal wall and deeper peritoneal pocket).
2. Locate largest pocket of anechoic fluid (>3 cm depth) free of adherent bowel loops.
3. Vascular Landmark: Activate Color Doppler to map and avoid the inferior epigastric artery (running ~4–5 cm lateral to midline).
1. Patient seated upright leaning forward.
2. Identify fluid pocket depth, diaphragm excursion during respiration, and atelectatic lung.
3. Insert needle 1 intercostal space below the fluid fluid level, strictly walking the needle over the superior rib margin to avoid the neurovascular bundle under the inferior costal groove.
1. Patient in seated flexion or lateral decubitus.
2. Transverse sweep identifies spinous processes (hyperechoic crescents with posterior shadow) and interspinous space.
3. Longitudinal paramedian view visualizes ligamentum flavum, thecal sac, and anterior dura to measure exact depth to subarachnoid space in obese patients.
3. Emergency Regional Nerve Blocks
Indication: Hip fractures, femoral shaft fractures.
Anatomy: Identify femoral artery, vein, and nerve under fascia lata and fascia iliaca ('NAVEL' lateral to medial).
Technique: High-volume injection (30–40 mL dilute local anesthetic) deep to fascia iliaca to bathe the femoral, lateral femoral cutaneous, and obturator nerves without contacting nerve bundle.
Indication: Multiple rib fractures, chest tube analgesia.
Anatomy: 4th–5th rib midaxillary line. Identify latissimus dorsi (superficial) and serratus anterior (overlying ribs).
Technique: Hydrodissect fascial plane either superficial or deep to serratus anterior muscle with 20–30 mL local anesthetic.
Indication: Distal radius fracture (Colles / Smith) reduction.
Technique: Linear probe visualizes cortical disruption and fracture hematoma. Under direct in-plane guidance, needle tip is placed directly into the hypoechoic fracture hematoma cavity to inject 10–15 mL of 1% lidocaine.
Integrated Resuscitation Protocols (RUSH & BLUE)
Systematic resuscitation algorithms: The RUSH protocol (The Pump, The Tank, The Pipes) for undifferentiated shock and the BLUE protocol decision tree for acute dyspnea.
Interactive RUSH Decision Tree
Hyperdynamic LV with kissing papillary walls; reduced chamber size; no pericardial effusion.
Completely flat, slit-like IVC (<2.1 cm) with 100% inspiratory collapse; E-FAST may show occult free peritoneal/pleural fluid; dry lungs (A-lines).
Evaluate abdominal aorta for ruptured AAA (diameter ≥ 3.0 cm with retroperitoneal hematoma); veins compressible without DVT.
The BLUE Protocol Diagnostic Algorithm
| Lung Profile | Sonographic Findings | Secondary Assessment | Definitive Diagnosis |
|---|---|---|---|
| A-Profile with DVT | Predominant A-lines with preserved lung sliding bilaterally | Positive lower extremity DVT on 2-point compression | Pulmonary Embolism (PE) |
| B-Profile | Diffuse bilateral vertical B-lines (>= 3 per intercostal space) | Plethoric IVC + depressed LV systolic function | Cardiogenic Pulmonary Edema |
| A/B or C-Profile | Asymmetric focal B-lines OR lung consolidation (hepatization, shred sign) | Dynamic air bronchograms | Pneumonia |
| A-Profile + Absent Sliding | A-lines with complete absence of lung sliding on B-mode / Barcode on M-mode | Presence of pathognomonic Lung Point | Pneumothorax |
| A-Profile without DVT | Bilateral A-lines with normal sliding, NO DVT, NO B-lines | Normal cardiac and thoracic windows | COPD / Severe Asthma Exacerbation |
Ultrasound Physics, Transducers, & Artifacts
Fundamental principles of diagnostic medical ultrasound: transducer classes, piezoelectric crystals, frequency vs. resolution trade-offs, and high-yield board artifacts.
1. Transducer Classes & Frequency Trade-Offs
Acoustic Footprint: Flat rectangular beam with high spatial resolution.
Depth: Superficial (typically 1–5 cm depth).
Clinical Applications: Vascular access, DVT compression, ocular ultrasound, anterior pleural sliding, soft tissue / musculoskeletal, and nerve blocks.
Acoustic Footprint: Curved fan-shaped beam with wide field of view.
Depth: Deep penetration (up to 20–30 cm).
Clinical Applications: Abdominal exams, E-FAST trauma views (RUQ, LUQ, pelvis), hepatobiliary, renal/bladder, abdominal aorta, and OB/GYN transabdominal scans.
Acoustic Footprint: Tiny acoustic footprint that electronically steers beams from a point source.
Depth: Deep penetration between ribs.
Clinical Applications: Echocardiography (FoCUS), thoracic windows, subxiphoid view, and RUSH pump assessment through narrow intercostal spaces.
2. Core Ultrasound Artifacts Tested on Boards
Mechanism: Ultrasound travels through low-attenuation fluid (cysts, gallbladder, urinary bladder) with minimal acoustic energy loss. When sound waves hit tissue directly posterior to fluid, they have higher amplitude than surrounding waves, producing a bright, hyperechoic band.
Diagnostic Value: Confirms fluid nature of abscess, cyst, or bladder.
Mechanism: High-attenuation structures (gallstones, renal calculi, cortical bone, foreign bodies) absorb or reflect nearly 100% of the ultrasound beam, creating an anechoic dark drop-out shadow deep to the object.
Diagnostic Value: Pathognomonic for gallstones and renal calculi.
Mechanism: Sound waves repeatedly bounce between two parallel reflective surfaces before returning to the probe, creating multiple equidistant parallel lines.
Examples: Physiological A-lines in aerated lung; metallic foreign bodies and needle shafts.
Mechanism: Sound reflects off a curved specular reflector (diaphragm) toward adjacent tissue before returning to probe, projecting a false duplicate structure deep to the reflector.
Clinical Landmark: Normal aerated lung displays mirror-image liver above diaphragm. Fluid disrupts this mirror, revealing the Spine Sign.
Mechanism: Form of reverberation caused by closely spaced reflective surfaces (cholesterol crystals in adenomyomatosis, surgical clips, or resonance of small air bubbles in bowel/biliary air). Produces a tapered triangular hyperechoic laser-like stripe.