POCUS Protocols — Step by Step
Point-of-care ultrasound the way it is actually used at the bedside: protocol-driven, question-first, one binary answer at a time. Each protocol below lists the probe to grab, the windows and the order to scan them, exactly what you are looking for, the positive findings that change management, and the pitfalls that catch people out. Pick a protocol on the left.
POCUS is focused, not comprehensive — correlate clinically. These protocols answer specific, binary clinical questions (“Is there free fluid? A pericardial effusion? Lung sliding?”). They do not replace a formal, comprehensive ultrasound or echocardiogram, and a negative scan never excludes disease. Findings must be interpreted with the whole clinical picture, by an operator working within their trained scope of practice and credentialing. Values and thresholds here are teaching defaults for an average adult — follow local protocols and your institution’s governance. Ultrasound is profoundly operator-dependent; nothing here substitutes for supervised, hands-on training.
eFAST Free
Extended Focused Assessment with Sonography in Trauma. A rapid bedside scan in the hypotensive or injured patient asking four binary questions: is there free fluid in the peritoneum (haemoperitoneum), in the pericardium (effusion/tamponade), or in the chest (haemothorax), and is there a pneumothorax? The classic FAST is four views — RUQ (Morison’s), LUQ (perisplenic), subxiphoid (pericardial) and suprapubic (pelvic) — “extended” adds bilateral anterior lung views for pneumothorax and the costophrenic angles for haemothorax. Probe: curvilinear or phased-array 2–5 MHz for the abdominal/cardiac windows; add a linear high-frequency probe for the pleura. Preset: abdomen/FAST; depth 16–20 cm for the abdominal views. Free intraperitoneal fluid is anechoic (black) and collects in the most dependent recesses; in the supine patient the hepatorenal (Morison’s) pouch is the most sensitive single location. A negative eFAST does not exclude injury — repeat/serial scans or CT as indicated.
View 1 — RUQ / Morison’s pouch (hepatorenal) FAST view
Curvilinear or phased-array 2–5 MHz, abdomen preset, depth 16–20 cm.
Supine (Trendelenburg increases sensitivity by pooling fluid in the upper abdomen). Marker to the patient’s head.
Right mid-to-posterior axillary line, ~10th–11th intercostal space (more posterior and cephalad than people expect). Coronal plane; align the probe with the rib interspaces and rock/fan through the whole interface.
Three interfaces, all of which must be cleared: the hepatorenal recess (Morison’s pouch) between liver and right kidney; the subphrenic space at the liver tip/diaphragm; and the right costophrenic angle above the diaphragm (for haemothorax) — mirror artefact above a normal diaphragm should be present.
- Anechoic stripe in Morison’s pouch — the most sensitive single FAST location for haemoperitoneum in the supine patient.
- Anechoic fluid at the caudal liver edge / paracolic gutter.
- Loss of the normal mirror artefact and anechoic fluid above the diaphragm = haemothorax; the spine becomes visible above the diaphragm (positive “spine sign”).
- Probe placed too anteriorly/low — Morison’s pouch is posterior and high; you will miss a small collection.
- Perinephric fat and the anechoic gallbladder or IVC mistaken for fluid; fluid is sharply marginated and tracks into dependent angles.
- A clotted haematoma can be echogenic (not black) — do not read only for anechoic fluid.
View 2 — LUQ / perisplenic (splenorenal) FAST view
Curvilinear or phased-array 2–5 MHz, abdomen preset.
Supine; marker to the head. Knuckles to the bed — the spleen sits high and posterior.
Left posterior axillary line, ~8th–10th intercostal space — deliberately more posterior and one interspace higher than the RUQ. Coronal plane.
Free fluid on the LUQ side collects subphrenic (above the spleen) first — before the splenorenal recess — the reverse of the RUQ. Check the subphrenic space, the splenorenal interface, the spleen tip, and the left costophrenic angle for haemothorax.
- Anechoic rim above the spleen (subphrenic) — the earliest LUQ sign; easily missed if you only look between spleen and kidney.
- Fluid in the splenorenal recess or at the spleen tip.
- Left haemothorax with loss of mirror artefact / positive spine sign above the diaphragm.
- Scanning too anterior/low — the LUQ window is the “knuckles to the bed” view; posterior and high.
- Stomach gas obscures the view — slide posterior and use the spleen as your window.
- Focusing on the splenorenal recess and missing the subphrenic collection that fills first.
View 3 — Subxiphoid / pericardial (cardiac) Life-threat
Phased-array 2–5 MHz (fits under the costal margin), cardiac or abdomen preset.
Supine; flex the knees to relax the abdominal wall. Marker to the patient’s right (abdomen convention) — the liver is the acoustic window.
Subxiphoid, probe flattened almost parallel to the skin, tip pushed under the xiphoid and aimed up toward the left shoulder. Use the left lobe of the liver as the window to a four-chamber view.
An anechoic pericardial collection surrounding the heart, and — critically — signs of physiological compromise: diastolic right ventricular collapse and systolic right atrial collapse (tamponade). If subxiphoid fails (obesity, gas, pain), substitute a parasternal long-axis view.
- Circumferential anechoic stripe within the bright pericardium = effusion; a large or rapidly-accumulating one with chamber collapse = tamponade — a reversible cause of traumatic/PEA arrest.
- Fat pad tip: an epicardial fat pad is usually anterior only and echogenic/moves with the heart — a true effusion is circumferential and anechoic.
- Anterior epicardial fat pad mistaken for effusion — fat is echogenic, anterior-only and moves synchronously; effusion is anechoic and dependent/circumferential.
- A left pleural effusion tracks posterior to the descending aorta on PLAX; a pericardial effusion tracks anterior to it.
- Reading effusion size alone — it is the physiology (chamber collapse), not the volume, that defines tamponade.
View 4 — Suprapubic / pelvic FAST view
Curvilinear 2–5 MHz, abdomen preset.
Supine. A full bladder is the acoustic window — image before catheterising where possible.
Midline just above the pubic symphysis, angled caudally into the pelvis. Scan in both the transverse (marker to patient’s right) and sagittal (marker to head) planes — the pelvis is the most dependent recess in the supine patient.
Anechoic free fluid in the rectovesical pouch (male) or rectouterine pouch of Douglas (female) — behind/around the bladder, posterior to the uterus.
- Anechoic collection posterior to the bladder or in the pouch of Douglas; free fluid in the pelvis often shows sharp angulated margins as it fills between loops of bowel.
- In females of reproductive age, correlate with pregnancy status — free fluid may represent a ruptured ectopic, not trauma.
- Empty bladder = no window and reduced sensitivity — scan before draining.
- Post-void/seminal-vesicle or ovarian physiological fluid over-called; a small amount of anechoic pelvic fluid can be normal in women.
- Not scanning in two planes — a shallow collection is easily missed on a single sweep.
Extended views — anterior lung for pneumothorax Life-threat
Linear high-frequency 5–10 MHz for the pleural line (a curvilinear/phased probe works but resolves the pleura less well). Lung/MSK preset; turn harmonics/persistence down so real-time motion is not smoothed away.
Supine — air rises, so the anterior (least dependent) chest at the 2nd–4th intercostal space, mid-clavicular line, is scanned first. Marker to the head, perpendicular to the ribs.
Probe across two ribs to obtain the “bat sign” (two rib shadows with the bright pleural line slung between them). Assess each side; move down laterally to the costophrenic angle for haemothorax.
Lung sliding — the shimmering to-and-fro of the visceral against parietal pleura at the pleural line. Present = no pneumothorax at that spot. Absent sliding raises the possibility of pneumothorax (also seen in intubation-related, adhesions, apnoea, ARDS). Confirm with M-mode: sliding gives the “seashore sign” (grainy sand below a still sky); absent sliding gives the “barcode / stratosphere sign” (all straight lines).
- Absent lung sliding + absent B-lines + A-lines only + no lung pulse — supportive but not specific.
- Lung point — the exact spot where absent sliding meets normal sliding (partial PTX in contact with the chest wall) — is ~100% specific (pathognomonic) for pneumothorax and its lateral extent estimates size. Its absence does not exclude a large PTX.
- Any B-line or preserved lung pulse at a location rules OUT pneumothorax there (visceral pleura is apposed).
- Absent sliding is sensitive but not specific — a mainstem intubation, bleb, prior pleurodesis, ARDS or breath-holding all abolish it. Do not diagnose PTX on absent sliding alone.
- Subcutaneous emphysema blocks the pleura entirely and mimics/obscures — recognise the “E-lines” and comet noise from soft tissue.
- Scanning too laterally in a supine patient — a small anterior PTX is missed if you don’t start at the least-dependent point.
Sequence memory aid: RUQ → LUQ → subxiphoid → suprapubic → both lungs. In arrest/peri-arrest, do the cardiac (subxiphoid or PLAX) window first — it changes management fastest.
RUSH — Rapid Ultrasound for Shock & Hypotension Free
A structured whole-body scan for the patient with undifferentiated hypotension, designed to sort shock into hypovolaemic, cardiogenic, obstructive or distributive within minutes (Perera et al.). The plumbing metaphor organises it: the pump (heart), the tank (effective circulating volume & its containers), and the pipes (arteries and veins). Probe: phased-array 2–5 MHz for pump/tank; add linear 5–10 MHz for lung and vascular. Work through pump → tank → pipes; each answers “which category of shock?”.
The Pump — cardiac contractility, effusion, RV Step 1
Phased-array 2–5 MHz, cardiac preset. Windows: parasternal long & short axis, apical 4-chamber, subcostal.
Is the pump strong or weak? Is there a pericardial effusion causing obstruction (tamponade)? Is the RV strained (acute PE)?
Global LV contractility (“eyeball” EF — do the walls thicken and the endocardium approach the midline in systole, does the anterior mitral leaflet nearly touch the septum). A pericardial effusion with diastolic RV collapse. RV size relative to LV (normal RV:LV <0.6 :1 apical).
- Hyperdynamic, small chambers → hypovolaemic or distributive (early sepsis) shock.
- Poorly contractile / dilated LV → cardiogenic shock.
- Pericardial effusion + RV diastolic collapse → obstructive shock (tamponade).
- Dilated RV, septal flattening (D-sign), McConnell’s → obstructive shock from acute PE / RV strain.
- Eyeball EF is coarse and operator-dependent — categorise (hyper/normal/hypo), don’t report a number.
- A chronically dilated RV (cor pulmonale) mimics acute strain — look for a thin, acutely dilated RV and preserved apical contraction (McConnell’s) for acute PE.
- Foreshortened apical views underestimate RV size — obtain the largest RV plane.
The Tank — IVC, lung, peritoneal/pelvic Step 2
Phased-array for IVC/subcostal; linear 5–10 MHz for lung/pleura; curvilinear for the FAST windows.
Is the tank full, empty, overloaded, or leaking?
Tank volume — IVC calibre and respiratory collapse (subcostal long axis, see IVC tab). Tank overload — bilateral lung B-lines (pulmonary oedema) and pleural effusions. Tank leak / compromise — free fluid on the abdominal/pelvic FAST (haemorrhage) or a pneumothorax reducing preload.
- Small, collapsing IVC + dry lungs → under-filled tank (hypovolaemia/distributive) — fluid-responsive.
- Plethoric IVC + diffuse B-lines → overloaded tank (cardiogenic / fluid overload) — stop fluids.
- Free peritoneal/pelvic fluid → tank leak (haemorrhage) — source control.
- Absent lung sliding + lung point → tension pneumothorax compressing the tank (obstructive).
- The IVC is a rough, dynamic gauge — never a single number for volume status (see IVC caveats tab).
- A few B-lines at the bases can be normal; interstitial syndrome requires ≥3 per field bilaterally.
- Mechanical ventilation reverses IVC respiratory dynamics — interpret accordingly.
The Pipes — aorta & DVT Step 3
Curvilinear 2–5 MHz for the aorta; linear 5–10 MHz for femoral/popliteal veins.
Are the pipes ruptured (AAA/dissection) or clotted (DVT → PE)?
Abdominal aorta in transverse from the epigastrium to the bifurcation — measure the outer-wall-to-outer-wall diameter; >3 cm = aneurysm, >5 cm or symptomatic = rupture risk. Look for an intimal flap (dissection). Veins — 2-point compression of the common femoral and popliteal veins.
- AAA >3 cm (esp. >5 cm) in a hypotensive patient → assume rupture (“pipe rupture”) — retroperitoneal bleed may not show on FAST.
- Non-compressible femoral/popliteal vein → DVT; in a strained RV this supports massive PE (“pipe clot” → obstructive shock).
- Intimal flap in the aorta → dissection.
- Ruptured AAA bleeds retroperitoneally — FAST is often negative; a normal FAST does not reassure.
- Measure outer-to-outer; mural thrombus is part of the aorta and is easy to exclude wrongly (under-measuring).
- Bowel gas obscures the aorta — apply graded compression, scan through the sagittal window, or reposition.
RUSH is a categorisation tool, not a diagnosis. It narrows undifferentiated hypotension to a mechanism so resuscitation is targeted — always integrated with history, exam and the rest of the workup.
Lung Ultrasound & the BLUE Protocol Free
Lung ultrasound reads the artefacts at the pleural line rather than the lung itself: normal aerated lung reflects sound to make horizontal A-lines; fluid/interstitial thickening creates vertical B-lines. The BLUE protocol (Lichtenstein & Mezière) applies this to acute respiratory failure with >90% accuracy by combining lung sliding, A/B-line profiles at standardised points, and venous analysis into a decision tree. Probe: linear 5–10 MHz for the pleura and pneumothorax; curvilinear/phased 2–5 MHz for deeper consolidation/effusion and the PLAPS point. Scan the bat sign, watch the pleural line, then count vertical artefacts per field.
Normal lung & A-lines — the anchor view Baseline
Linear 5–10 MHz (or curvilinear), lung preset; single focus at the pleural line; harmonics/persistence low to preserve motion.
Longitudinal across two ribs → bat sign (rib–pleura–rib). Anterior chest, mid-clavicular, 2nd–4th space to start; systematically cover anterior, lateral and PLAPS points.
Lung sliding at the pleural line + horizontal A-lines = normal, dry, aerated lung (“A-profile”). M-mode over sliding lung = seashore sign.
- A-profile (A-lines + sliding) across the anterior chest = normal aeration → in acute dyspnoea, points away from cardiogenic oedema and toward COPD/asthma or PE (check veins).
- Excess persistence/harmonics smooths out sliding and B-line dynamics — turn them down.
- Deep focus degrades the pleural line — put the single focus at the pleura.
B-lines & interstitial syndrome Core
Vertical, discrete, laser-like lines arising from the pleural line, reaching the bottom of the screen, erasing A-lines and swinging with lung sliding. ≥3 B-lines between two ribs in one field = a positive (B) field.
Bilateral, diffuse, symmetric B-lines (“lung rockets”, B-profile) → cardiogenic pulmonary oedema / interstitial syndrome. Focal/asymmetric B-lines → pneumonia, contusion, ARDS (patchy).
- Diffuse bilateral B-lines + lung sliding (B-profile) → pulmonary oedema (in the BLUE tree, points to cardiogenic cause).
- Coalescent “white lung” → severe alveolar-interstitial fluid (oedema/ARDS).
- Focal B-lines with an irregular pleura → early pneumonia or contusion.
- 1–2 B-lines at the bases/last interspace can be normal (especially dependent zones) — require ≥3 per field and a bilateral pattern for interstitial syndrome.
- Z-lines (short, don’t reach the bottom, don’t erase A-lines, don’t move) are artefacts — do not count them as B-lines.
- Chronic fibrosis also produces B-lines with an irregular pleura — correlate clinically.
Consolidation, shred sign & pleural effusion PLAPS point
Curvilinear/phased 2–5 MHz for depth; the PLAPS point (postero-lateral alveolar/pleural syndrome) is scanned as posteriorly as possible in the supine patient.
Consolidation = tissue-like (“hepatised”) lung with air/fluid bronchograms; its deep border is irregular where aerated lung begins — the shred / fractal sign. Pleural effusion = anechoic space above the diaphragm with the quad sign (static) and sinusoid sign (respiratory movement of the lung line on M-mode).
- Hepatised lung + dynamic air bronchograms → pneumonia (dynamic bronchograms argue against obstructive atelectasis).
- Shred/fractal sign at the deep border → subpleural consolidation.
- Anechoic collection + quad + sinusoid sign → pleural effusion; the “spine sign” (spine visible above the diaphragm) confirms fluid.
- Mirror-image artefact of the liver/spleen across the diaphragm mistaken for consolidation — a real subphrenic organ won’t move paradoxically with respiration.
- Complex/septated or haemorrhagic effusions are echogenic, not anechoic — don’t require a black collection.
Pneumothorax on lung ultrasound Life-threat
Least-dependent (anterior) point in the supine patient. Linear probe, real-time then M-mode.
The stepwise rule-in: (1) absent lung sliding, (2) absent B-lines and absent lung pulse, (3) A-lines only, then (4) the lung point.
- Lung point = pathognomonic (~100% specific) for pneumothorax; also localises its lateral extent/size.
- M-mode barcode/stratosphere sign (all horizontal lines, no seashore) supports absent sliding.
- Any B-line or a lung pulse at a point excludes pneumothorax there (pleurae apposed).
- Absent sliding is sensitive but not specific (mainstem intubation, pleurodesis, ARDS, apnoea, bullae) — never diagnose PTX on absent sliding alone; hunt for the lung point.
- A very large/complete PTX may have no lung point (the lung is fully collapsed away from the wall) — absence of a lung point does not exclude PTX.
- Subcutaneous emphysema obscures the pleura entirely — recognise it and don’t over-interpret.
Diaphragm & the BLUE decision tree Integrate
Curvilinear/phased probe, subcostal or low intercostal (mid-axillary). Assess excursion (M-mode caudal movement with inspiration, normal ~1.5–7 cm) and thickening fraction — for diaphragm dysfunction, weaning failure, phrenic palsy.
A-profile + DVT → PE. A-profile, no DVT + PLAPS → pneumonia. A-profile, no DVT, no PLAPS → COPD/asthma. B-profile → pulmonary oedema. A/B or C-profile → pneumonia.
- Combining sliding, A/B-line profile at three standardised points, and venous compression yields a >90% accurate diagnosis of the cause of acute respiratory failure at the bedside.
- Profiles were validated in acute respiratory failure — applying them to chronic or mixed disease reduces accuracy.
- The tree is a starting point, not a substitute for CXR/CT and clinical judgement.
Focused Cardiac Ultrasound (FoCUS) Free
A goal-directed cardiac scan answering a handful of binary questions — is there a pericardial effusion? Is the LV grossly good or poor? Is the RV enlarged? Is there gross valvular disease? — and, with the IVC, a volume estimate. It is not a comprehensive echocardiogram: no quantitative Doppler, no valve gradients, no wall-motion scoring. Probe: phased-array 2–5 MHz, cardiac preset (marker convention differs from abdomen — see each view). Four core windows: PLAX, PSAX, apical 4-chamber, subcostal.
Parasternal long axis (PLAX) Window 1
Left parasternal, 3rd–4th intercostal space; probe marker to the patient’s right shoulder (cardiac convention). Left lateral decubitus improves the window.
RV (anterior), LV, mitral and aortic valves, LA, LVOT, and the descending thoracic aorta in cross-section posteriorly.
Global LV function (“eyeball” EF — endocardial excursion and wall thickening; EPSS: the anterior mitral leaflet nearly touching the septum implies good EF, a wide gap implies poor). Pericardial effusion — track its relationship to the descending aorta. Gross aortic/mitral disease.
- Good vs poor LV by eyeball (categorise; don’t quantify).
- Pericardial effusion anterior to the descending aorta (a pleural effusion tracks posterior to it) — key discriminator.
- Heavily calcified/immobile valve leaflets, obvious regurgitant jets on colour.
- Pericardial vs pleural effusion confused — use the descending aorta landmark.
- Off-axis PLAX foreshortens the LV and misleads EF — optimise so the aortic and mitral valves and the LV apex line up.
Parasternal short axis (PSAX) Window 2
Rotate ~90° clockwise from PLAX (marker to the patient’s left shoulder). Fan from base (aortic valve “Mercedes”) to mid-papillary level.
At the mid-papillary level, assess concentric LV wall thickening and the septal shape. A round LV = normal; a D-shaped septum (flattening) indicates RV pressure/volume overload. Regional wall-motion at a glance.
- D-sign (septal flattening) → RV strain (acute PE, pulmonary hypertension).
- Uniformly poor thickening → global dysfunction; a discrete akinetic segment → regional ischaemia.
- Oblique cuts distort the circular LV — get a true short axis at the papillary muscles before judging the septum.
Apical 4-chamber (A4C) Window 3
Point of maximal impulse (5th space, mid-clavicular); marker to the patient’s left. Left lateral decubitus and a shallow angle help. All four chambers with both AV valves.
Direct RV : LV size comparison (normal RV <⅔ of LV; RV ≥ LV = enlargement). Chamber sizes, gross valve motion, and RA/RV collapse in effusion. McConnell’s sign — RV free-wall akinesis with a preserved apex — supports acute PE.
- RV ≥ LV, McConnell’s sign → acute RV strain / PE.
- Systolic RA collapse — the earliest tamponade sign — best seen here and subcostal.
- Foreshortening (apex not at the top) enlarges/rounds the apex and can under- or over-call RV size — obtain the largest true 4-chamber plane.
- Off-axis views distort the RV:LV ratio.
Subcostal (subxiphoid) 4-chamber + IVC Window 4
Subxiphoid, probe flattened, aimed at the left shoulder, liver as the window (same as eFAST cardiac). Best window in arrest/CPR and often the only one in a ventilated/large patient.
Pericardial effusion & tamponade physiology (the most reliable window for this), gross biventricular function, and — sweeping to the IVC — volume status (see IVC tab).
- Circumferential effusion + chamber collapse → tamponade.
- Cardiac standstill in arrest (no organised wall motion) — powerful prognostic information.
- Bowel gas/obesity/pain limit the window — press the probe flat and use liver; try PLAX if it fails.
- Never delay/interrupt compressions for imaging — capture the subcostal clip during a pulse check.
FoCUS gives a gross, qualitative answer. Any abnormality — reduced function, unexplained effusion, valve disease, RV enlargement — should prompt a comprehensive echocardiogram.
IVC & Volume Assessment Free
The inferior vena cava is a quick, non-invasive gauge of central venous filling and its respiratory variation — useful, but only ever one dynamic data point among many. It estimates right atrial pressure and hints at fluid-responsiveness; it does not, by itself, decide volume status. Probe: phased-array 2–5 MHz, cardiac/abdomen preset.
Subcostal long-axis IVC Core view
Subxiphoid; find the IVC in its long axis entering the right atrium, just to the patient’s right of the aorta. Confirm it is the IVC (hepatic vein draining in, connects to RA, thin-walled, respiratory-variable) — not the aorta.
Measure the maximum diameter ~2 cm caudal to the IVC–RA junction or just distal to the hepatic-vein inflow, perpendicular to the vessel. M-mode captures the respiratory swing.
Maximum and minimum diameter across the respiratory cycle → collapsibility index (spontaneously breathing) or distensibility index (mechanically ventilated). Combine calibre + variation.
- Small IVC (<2.1 cm) collapsing >50% → low RA pressure (~0–5 mmHg); suggests under-filling / likely fluid-responsive in the right context.
- Plethoric IVC (>2.1 cm) with <50% (or <20%) collapse → high RA pressure (~15 mmHg); argues against giving fluid.
- In ventilated patients a distensibility >~18% has been associated with fluid-responsiveness (validated only in specific, fully passive conditions).
- Cylinder-tangent error: an off-axis long-axis cut clips the edge of the vessel and under-measures diameter — confirm you are through the centre (or use short axis).
- The IVC is confounded by anything that raises right-sided pressure independent of volume: RV failure, severe TR, pulmonary hypertension, tamponade, tension PTX, raised intra-abdominal pressure, and PEEP/positive-pressure ventilation (which reverses the normal collapse pattern).
- Forced/obstructed breathing exaggerates collapse; a sniff test is not equivalent to tidal breathing.
- IVC values assess preload/fluid tolerance, not fluid-responsiveness per se; use it as a trend and alongside passive-leg-raise, lung B-lines and cardiac function — never as a stand-alone number.
Procedural & Other Focused Scans
POCUS beyond the resuscitation-room protocols: real-time procedural guidance and single-organ focused scans that answer a specific question. Pick a topic. Free topics are open; deeper procedural technique and image libraries are Pro.
Ultrasound-guided vascular access & central lines Procedural Free
Linear 5–10+ MHz, vascular/small-parts preset; sterile probe cover and gel for the procedure.
Identify the target vein (compressible, thin-walled, non-pulsatile) vs the neighbouring artery (round, pulsatile, non-compressible) in short axis; distinguish with compression and colour Doppler. Use dynamic real-time guidance: keep the needle tip in view, walking the beam down the shaft (“scan the tip, not the shaft”). Confirm the tip inside the lumen before dilating.
- Vein fully compresses; artery does not — never cannulate a non-compressible, pulsatile vessel.
- Needle tip (a bright dot) confirmed within the vein lumen, not tenting the wall or through the back wall.
- Post-procedure: confirm wire in the vein and rule out pneumothorax (absent sliding) after IJ/subclavian lines.
- Following the needle shaft and mistaking it for the tip → posterior-wall puncture / arterial injury.
- Out-of-plane vs in-plane confusion — commit to one technique and keep the tip localised.
- Under-recognised pneumothorax after the procedure — always re-scan the pleura.
Thoracentesis / paracentesis — site marking Procedural Free
Curvilinear 2–5 MHz for depth; linear to confirm superficial vessels/wall.
Position the patient as for the procedure (upright/leaning for pleura; supine/lateral decubitus for ascites), scan to find the largest anechoic pocket free of bowel/lung/solid organ, measure its depth, and mark the skin. For thoracentesis stay above the rib (avoid the sub-costal neurovascular bundle) and confirm the diaphragm and lung position through the respiratory cycle.
- Adequate fluid depth (commonly ≥~1.5 cm) with no interposed lung, liver/spleen or bowel loop.
- Diaphragm excursion mapped so you don’t cross it at the wrong phase (pleural taps).
- Ideally real-time or immediate mark-and-puncture in the same position — fluid shifts if the patient moves.
- Marking the skin then repositioning the patient — the pocket moves; mark and drain in the same position.
- Mistaking a mirror-image or hepatised lung for fluid at the lung base.
- Not screening for the neurovascular bundle / superficial collaterals before pleural puncture.
Soft tissue — abscess vs cellulitis Focused Free
Linear 5–10+ MHz, small-parts/superficial preset; a standoff (gel/water bath) helps very superficial lesions.
Cellulitis = thickened, oedematous subcutaneous tissue with anechoic fluid tracking between fat lobules → the “cobblestone” appearance, without a drainable collection. Abscess = a discrete hypo/anechoic (often complex, debris-filled) fluid collection, frequently with posterior acoustic enhancement and “swirl” of contents on probe compression.
- Drainable collection with swirl sign → incision & drainage (POCUS changes management by finding occult pus).
- Colour Doppler: peripheral hyperaemia around an abscess; no internal flow within pus.
- Screen for a deep tracking sinus or foreign body.
- Do not mistake a normal lymph node, vessel, or ganglion cyst for an abscess — check with Doppler and two planes.
- Gas within tissue (crepitus, “dirty shadowing”) may indicate necrotising infection — a surgical emergency, not an I&D.
- Compressing a vessel/aneurysm believing it is pus.
Lower-limb DVT — 2-point & 3-point compression Focused Free
Linear 5–10 MHz, vascular preset; patient supine, hip externally rotated, knee slightly flexed (reverse-Trendelenburg distends the veins).
In transverse, apply firm compression every ~1 cm. A normal vein fully collapses (walls touch); a vein that does not fully compress harbours thrombus. 2-point: common femoral vein (including the saphenofemoral junction) and popliteal vein (to the trifurcation). 3-point/extended: adds the femoral vein along the thigh.
- Non-compressible venous segment = DVT; echogenic intraluminal thrombus and loss of colour filling support it.
- Scan through the SFJ and popliteal trifurcation — common sites for isolated clot.
- Partial compressibility is NOT a normal study — the walls must fully appose.
- 2-/3-point protocols scan proximal veins only — they miss isolated iliac (e.g. pregnancy) and calf vein DVT; a negative POCUS study does not exclude DVT and may need whole-leg or repeat scanning.
- Enlarged lymph nodes, Baker’s cysts or a duplicated system mistaken for vein/clot — confirm anatomy in two planes.
Ocular ultrasound Focused Pro
Linear 7.5–15 MHz, ocular/low-MI preset (use the dedicated eye preset — minimise mechanical/thermal output). Copious gel over a closed lid with a transparent dressing; the eye is never directly touched or compressed.
Retinal detachment (mobile bright membrane, tethered at the disc), vitreous haemorrhage, lens dislocation, and optic nerve sheath diameter (ONSD) measured 3 mm behind the globe as a surrogate for raised intracranial pressure.
- Full ONSD measurement technique and thresholds, detachment vs posterior vitreous detachment discrimination, and a labelled normal/abnormal image set.
- Never apply pressure or scan with a suspected globe rupture — imaging is contraindicated.
- Keep output low (ALARA) over the lens.
Focused gallbladder, renal & aorta Focused Pro
Curvilinear 2–5 MHz. Question: stones, wall >3 mm, pericholecystic fluid, sonographic Murphy sign for cholecystitis. Roll the patient to prove stone mobility.
Question: hydronephrosis (anechoic dilated calyces/pelvis) in the flank pain/AKI patient — graded mild→severe; check the bladder and ureteric jets.
Transverse epigastrium to bifurcation; outer-wall-to-outer-wall AAA screen (>3 cm aneurysm). Overlaps the RUSH “pipes” step — a life-threat to exclude in abdominal/back pain and hypotension.
- Graded hydronephrosis image library, CBD measurement technique, full AAA measurement pitfalls, and the acute-abdomen focused-scan pathway.
- Prominent extrarenal pelvis or full-bladder back-pressure mimicking hydronephrosis.
- Bowel gas hiding the aorta — a negative-appearing scan is non-diagnostic, not reassuring.
First-trimester / intrauterine pregnancy (IUP) Focused Pro
Curvilinear 2–5 MHz transabdominal (full bladder window); endovaginal high-frequency where trained and available for the definitive answer.
A definitive IUP = a gestational sac containing a yolk sac and/or fetal pole within the uterus, surrounded by myometrium on all sides. The clinical purpose is to reduce the likelihood of ectopic in the pregnant patient with pain/bleeding.
- Discriminatory-zone reasoning, pseudogestational-sac vs true sac, adnexal/free-fluid evaluation for ectopic, and the RUSH cross-link for the unstable pregnant patient.
- A pseudogestational sac (central, no yolk sac) in ectopic mistaken for an IUP — require a yolk sac/fetal pole and eccentric implantation.
- Never fully exclude ectopic on a transabdominal scan alone; correlate with β-hCG and formal imaging.
- Heterotopic pregnancy (rare, higher risk with ART) — an IUP does not fully exclude a co-existing ectopic.
Go deeper with High Yield Ultrasound Pro
The protocols above are free. Pro unlocks the full POCUS training layer built on the same evidence base:
- Annotated normal-vs-abnormal image and clip libraries for every view (lung point, McConnell’s, D-sign, cobblestone/swirl, hydronephrosis grades, ONSD).
- Full ocular, focused biliary/renal/aorta and first-trimester scanning technique with thresholds.
- Integrated decision trees (BLUE, RUSH categorisation), a self-test question bank, and printable protocol cards for the resus trolley.
References & further reading
- American College of Emergency Physicians (ACEP). Ultrasound Guidelines: Emergency, Point-of-care and Clinical Ultrasound Guidelines in Medicine. Policy statement, latest revision.
- ACEP SonoGuide. Rapid Ultrasound for Shock and Hypotension (RUSH). acep.org/sonoguide/advanced/rush
- Perera P, Mailhot T, Riley D, Mandavia D. The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically ill. Emerg Med Clin North Am. 2010;28(1):29–56.
- Seif D, Perera P, Mailhot T, et al. Bedside ultrasound in resuscitation and the Rapid Ultrasound in Shock protocol. Crit Care Res Pract. 2012;2012:503254.
- Lichtenstein DA, Mezière GA. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest. 2008;134(1):117–125.
- Lichtenstein DA. BLUE-protocol and FALLS-protocol: two applications of lung ultrasound in the critically ill. Chest. 2015;147(6):1659–1670.
- Lichtenstein D, Mezière G, Biderman P, et al. The lung point: an ultrasound sign specific to pneumothorax. Intensive Care Med. 2000;26(10):1434–1440.
- Volpicelli G, Elbarbary M, Blaivas M, et al. International evidence-based recommendations for point-of-care lung ultrasound. Intensive Care Med. 2012;38(4):577–591.
- Lichtenstein DA. Lung ultrasound in the critically ill. Ann Intensive Care. 2014;4(1):1.
- Kirkpatrick AW, Sirois M, Laupland KB, et al. Hand-held thoracic sonography for detecting post-traumatic pneumothoraces: the Extended FAST (EFAST). J Trauma. 2004;57(2):288–295.
- Rozycki GS, Ballard RB, Feliciano DV, et al. Surgeon-performed ultrasound for the assessment of truncal injuries. Ann Surg. 1998;228(4):557–567.
- Bloom BA, Gibbons RC. Focused Assessment with Sonography for Trauma (FAST). StatPearls. NCBI Bookshelf, updated 2023.
- Merck Manual Professional. How To Do E-FAST Examination. Critical Care Medicine.
- POCUS.org. eFAST Examination — A Brief Overview.
- Via G, Hussain A, Wells M, et al. International evidence-based recommendations for focused cardiac ultrasound (WINFOCUS/FoCUS). J Am Soc Echocardiogr. 2014;27(7):683.e1–683.e33.
- Labovitz AJ, Noble VE, Bierig M, et al. Focused cardiac ultrasound in the emergent setting: ASE/ACEP consensus statement. J Am Soc Echocardiogr. 2010;23(12):1225–1230.
- McConnell MV, Solomon SD, Rayan ME, et al. Regional right ventricular dysfunction detected by echocardiography in acute pulmonary embolism. Am J Cardiol. 1996;78(4):469–473.
- Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the echocardiographic assessment of the right heart in adults (ASE). J Am Soc Echocardiogr. 2010;23(7):685–713.
- Kircher BJ, Himelman RB, Schiller NB. Non-invasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava. Am J Cardiol. 1990;66(4):493–496.
- Rudski LG et al.; POCUS.org. IVC Assessment for Volume Status in POCUS. pocus.org (accessed 2026).
- Via G, Tavazzi G, Price S. Ten situations where inferior vena cava ultrasound may fail to reflect central venous pressure. Intensive Care Med. 2016;42(7):1164–1167.
- Bernardi E, Camporese G, Büller HR, et al. Serial 2-point ultrasonography plus D-dimer vs whole-leg colour-Doppler ultrasound for suspected DVT. JAMA. 2008;300(14):1653–1659.
- Pomero F, Dentali F, Borretta V, et al. Accuracy of emergency physician–performed ultrasonography for DVT: meta-analysis. Thromb Haemost. 2013;109(1):137–145.
- POCUS.org. POCUS Compression Test for Deep Vein Thrombosis Assessment.
- Adhikari S, Blaivas M, Lyon M. Diagnosis and management of ocular POCUS in the emergency department. J Emerg Med. (ocular POCUS review).
- Radiopaedia.org. eFAST, RUSH protocol, lung ultrasound, BLUE protocol, IVC assessment (reference articles, accessed 2026).
Educational summary for trained clinicians. Protocol specifics, thresholds and scope of practice vary by jurisdiction, specialty and institution — always follow your local credentialing and governance. POCUS findings are adjuncts to, not replacements for, comprehensive imaging and clinical assessment.