40 THORACIC ANATOMY & PATHOLOGY

# THORACIC ANATOMY & PATHOLOGY

Detailed notes

The thorax is the busiest crossroads in human anatomy. Three organ systems share a single bony cage, and the surgical questions in MRCS Part A circle the same anatomical relationships again and again — which structure lies behind the sternum at the 5th ICS, where to put a chest drain, why an oesophagectomy causes a chylothorax. Build the anatomy first; the pathology then falls into place.

Thoracic wall

The thoracic cage has 12 pairs of ribs:

➡ Ribs 1–7 ➡ True ribs — articulate directly with sternum via own costal cartilage.

➡ Ribs 8–10 ➡ False ribs — costal cartilage fuses with cartilage above (the costal margin).

➡ Ribs 11–12 ➡ Floating ribs — no anterior attachment.

Each typical rib has a costal groove on its inferior border housing the neurovascular bundle. The order from superior to inferior is VAN: Vein, Artery, Nerve. This is why all needles into the chest wall (chest drain, intercostal block, pleural aspiration) are passed along the upper border of the rib below — to avoid the bundle tucked under the rib above.

👩‍⚕️ The internal thoracic (mammary) artery runs vertically about 1 cm lateral to the sternal edge. It supplies the anterior intercostals, the sternum, and is harvested as the LITA in CABG. Once both ITAs are harvested, the sternum survives on intercostal collaterals — which is why bilateral ITA harvest plus dehiscence is a vascular disaster.

Triangle of safety (chest drain)

Boundaries:

➡ Anterior ➡ Lateral border of pectoralis major.

➡ Posterior ➡ Lateral border of latissimus dorsi.

➡ Inferior ➡ Horizontal line through the nipple (5th ICS).

➡ Apex ➡ Base of axilla.

Drain is inserted just above the rib below to avoid the neurovascular bundle. Going lower than the 5th ICS risks the diaphragm, liver and spleen.

Diaphragm — openings and innervation

Three big openings, easy to remember by vertebral level = number of letters in the structure:

Level	Opening	Contents
T8	Caval (vena cava) hiatus	IVC, right phrenic nerve
T10	Oesophageal hiatus	Oesophagus, both vagi, left gastric vessels
T12	Aortic hiatus	Aorta, thoracic duct, azygos vein

Mnemonic: I ate (T8) ten (T10) eggs at twelve (T12).

Motor and sensory supply is the phrenic nerve, C3–C5 — "C3, 4, 5 keeps the diaphragm alive." This is why diaphragmatic irritation (subdiaphragmatic blood, gas after laparoscopy, abscess) refers pain to the C4 dermatome — the shoulder tip.

The diaphragm develops from four embryological components. A defect in the pleuroperitoneal (pericardioperitoneal) membrane — most often on the left — produces a Bochdalek hernia, presenting with neonatal respiratory distress and bowel in the chest.

Mediastinum

Divided by an imaginary line at the sternal angle (T4/T5) into superior and inferior, with the inferior subdivided into anterior, middle and posterior:

Compartment	Key contents
Superior	Aortic arch + branches, brachiocephalic veins, SVC, trachea, oesophagus, thymus, thoracic duct, vagus, phrenic, recurrent laryngeal
Anterior	Thymic remnants, lymph nodes, fat
Middle	Heart in pericardium, roots of great vessels, main bronchi, phrenic nerves
Posterior	Descending aorta, oesophagus, thoracic duct, azygos/hemiazygos, sympathetic chain, splanchnic nerves

👩‍⚕️ Anterior mediastinal mass — the 4 T's: Thymoma, Teratoma, Thyroid (retrosternal), Terrible lymphoma. A mediastinal mass with myasthenia gravis = thymoma until proven otherwise.

Lung hilum — anatomical relations

The hilum is at the level of T5–T7. The course of structures around the hilum is heavily examined.

Right hilum:

➡ Anterior ➡ Phrenic nerve, pericardiophrenic vessels, SVC.

➡ Posterior ➡ Vagus nerve, oesophagus, azygos vein (arching forward over the top to drain into SVC).

Left hilum:

➡ Anterior ➡ Phrenic nerve.

➡ Superior ➡ Aortic arch.

➡ Posterior ➡ Vagus nerve, descending thoracic aorta.

Within both hila, the anteroposterior sequence is the same: pulmonary vein → pulmonary artery → bronchus ("VAB"). On the right, the eparterial bronchus (upper lobe) emerges above the pulmonary artery; on the left the artery hooks over the bronchus first ("hyparterial").

Lungs

Feature	Right lung	Left lung
Lobes	3 (upper, middle, lower)	2 (upper, lower)
Fissures	Oblique + horizontal	Oblique only
Notable feature	Eparterial bronchus	Cardiac notch, lingula
Main bronchus	Shorter, wider, more vertical	Longer, narrower, more horizontal

👩‍⚕️ The right main bronchus geometry explains why aspirated foreign bodies, gastric contents and a misplaced ET tube all preferentially enter the right lung.

The pleura has two layers — visceral (covers lung, insensate) and parietal (covers chest wall, diaphragm and mediastinum). Parietal pleura sensation:

➡ Costal + peripheral diaphragmatic pleura ➡ Intercostal nerves (sharp, well-localised, dermatomal pain).

➡ Mediastinal + central diaphragmatic pleura ➡ Phrenic nerve (C3–5) — referred to the shoulder tip.

The costodiaphragmatic recess is the deepest part of the pleural cavity and the lowest point fluid collects in an upright patient — relevant for thoracentesis.

Respiratory mechanics — high-yield

The diaphragm provides ~70% of tidal volume at rest. Pleural pressure is normally negative (~–5 cmH₂O at end-expiration) — this is what keeps the lung expanded against the chest wall. It becomes positive only during Valsalva, forced expiration, coughing, or positive-pressure ventilation.

Lung volume	Definition
Tidal volume (TV)	Volume per quiet breath (~500 mL)
Vital capacity (VC)	Max inspiration → max expiration (excludes RV)
Total lung capacity (TLC)	VC + residual volume
Residual volume (RV)	Air left after max expiration; ↑ in COPD (air trapping)
FEV₁/FVC	< 0.7 obstructive; > 0.7 (normal/high) with low FVC = restrictive

Pneumothorax

Type	Mechanism	Key features	Management
Simple primary	Spontaneous, tall thin young man, ruptured apical bleb	Stable, no haemodynamic compromise	< 2 cm + asymptomatic → observe; > 2 cm or breathless → aspiration; failed → chest drain (BTS)
Secondary	Underlying lung disease (COPD, asthma)	Often more symptomatic	Chest drain in most cases
Traumatic	Penetrating or blunt injury	Often with haemothorax	Chest drain
Tension	One-way valve traps air; mediastinal shift	Hypoxia, hypotension, tracheal deviation away, raised JVP, hyper-resonance, absent breath sounds	Immediate needle decompression, then chest drain

Needle decompression: traditionally 2nd ICS, midclavicular line; ATLS 10th edition also accepts 4th/5th ICS, anterior axillary line (adult chest wall thickness). Follow with a definitive chest drain in the triangle of safety.

👩‍⚕️ Classic SBA trap: a simple pneumothorax that becomes a tension pneumothorax after intubation — positive-pressure ventilation forces air through the pleural defect. Always re-examine after intubating a chest trauma patient.

Haemothorax

Blood in the pleural space, usually from a lacerated intercostal artery (commonest source in chest drain bleeding), internal thoracic artery, or great vessel. Manage with a large-bore (28–32 Fr) chest drain.

Massive haemothorax (a thoracotomy indication):

➡ Initial drainage > 1500 mL, or

➡ Ongoing drainage > 200 mL/h for 2–4 hours, or

➡ Persistent need for transfusion.

Rib fractures and flail chest

- Isolated single rib fracture in a young, fit patient → analgesia and discharge.

- Rib fracture in COPD/elderly → admit for monitoring; missed pneumothorax and atelectasis are killers.

- Flail chest = ≥ 2 adjacent ribs fractured in ≥ 2 places → paradoxical chest wall movement. Underlying pulmonary contusion drives the hypoxia, not the bony segment itself. Treatment is analgesia, oxygen, and positive-pressure ventilation if respiratory failure (low PaO₂ despite high FiO₂, fatigue).

- 4 rib fractures + hypoxia with normal CO₂ (type I failure) → CPAP to recruit alveoli.

Cardiac tamponade

Pericardial fluid compresses the heart and prevents diastolic filling.

Beck's triad: hypotension + raised JVP + muffled heart sounds.

Also expect pulsus paradoxus (> 10 mmHg fall in systolic BP on inspiration) and electrical alternans on ECG. Diagnosis is by echo (or FAST); treatment is subxiphoid pericardiocentesis under ultrasound guidance (needle aimed at left shoulder), or surgical pericardial window.

👩‍⚕️ Anatomy of the precordial stab: at the left 5th ICS, sternal border, the structure in immediate danger is the pericardium, then the right ventricle behind it (the RV forms most of the anterior cardiac surface). A stable stab patient with a normal CXR still needs an echo/FAST to exclude tamponade.

Pulmonary embolism

Risk factors: surgery, immobility, malignancy, OCP, pregnancy. Most commonly presents 5–7 days post-op.

➡ Clinical: pleuritic chest pain, dyspnoea, tachycardia, haemoptysis.

➡ ECG: sinus tachycardia is commonest; S1Q3T3 is classic but rare.

➡ Wells score stratifies probability.

➡ Low Wells → D-dimer. Negative excludes; positive → CTPA.

➡ High Wells → straight to CTPA (the gold standard).

➡ Massive PE with haemodynamic compromise → thrombolysis or embolectomy.

Lung cancer

Type	Frequency	Location	Smoking link	Classic features
Adenocarcinoma	Most common overall; most common in non-smokers	Peripheral	Modest	Glandular cells; ground-glass on CT
Squamous cell	~25%	Central	Strong	Cavitation, hypercalcaemia via PTHrP, keratin pearls
Large cell	~10%	Peripheral or central	Strong	Anaplastic, undifferentiated
Small cell (SCLC)	~15%	Central	Strongest	Neuroendocrine; rapid spread; paraneoplastic

SCLC paraneoplastic syndromes:

➡ SIADH ➡ Hyponatraemia.

➡ Ectopic ACTH ➡ Cushing's syndrome.

➡ Lambert-Eaton myasthenic syndrome ➡ Antibodies to voltage-gated calcium channels; proximal weakness that improves with repeated use (opposite of myasthenia gravis).

Pancoast (superior sulcus) tumour — usually SCC at the lung apex, invading nearby structures:

➡ Horner's syndrome ➡ Ptosis, miosis, anhydrosis (sympathetic chain).

➡ T1 wasting of intrinsic hand muscles ➡ Lower trunk of brachial plexus.

➡ Arm pain ➡ Brachial plexus invasion.

➡ ± Hoarseness (recurrent laryngeal), SVC obstruction.

Mesothelioma — pleural malignancy; classical link with asbestos exposure, latency 20–40 years. Histology: calretinin and WT-1 positive. Poor prognosis.

Pneumonia, empyema and lung abscess

Empyema = pus in the pleural space, usually complicating pneumonia. Diagnosed on pleural fluid analysis: pH < 7.2, glucose < 2.2, frank pus or organisms. Requires chest drain + antibiotics; loculated collections may need VATS.

Lung abscess = localised cavitary collection within parenchyma. Causes: aspiration (right lower lobe — anatomy of the right main bronchus again), post-pneumonic, septic emboli. CT shows a thick-walled cavity with an air-fluid level.

ARDS vs cardiogenic pulmonary oedema

A classic ITU SBA. Both give bilateral infiltrates and hypoxia — the discriminator is the pulmonary capillary wedge pressure (PCWP), a surrogate for left atrial pressure.

Feature	ARDS	Cardiogenic oedema
Mechanism	Alveolar–capillary membrane injury (sepsis, pancreatitis, trauma)	LV failure / fluid overload
PCWP	< 18 mmHg (non-cardiogenic)	> 18 mmHg
JVP / CVP	Usually normal	Raised
CXR	Bilateral infiltrates	Bilateral infiltrates, ± Kerley B, cardiomegaly
Compliance	Reduced (stiff lungs)	Reduced
Treatment	Lung-protective ventilation (6 mL/kg, low plateau pressure, PEEP), treat cause	Diuresis, afterload reduction, treat cause

Test yourself

[Image: MCQs banner]

A 19-year-old falls from a horse and has a fracture of the medial third of the left clavicle with profound hypovolaemia. Which vessel is most likely injured?

• ((Left subclavian artery::☑️ Runs posterior to the medial clavicle; at risk in medial-third fractures.))
• ((Brachiocephalic trunk::Right-sided only; the left subclavian arises directly from the arch.))
• ((Left axillary artery::Lies lateral to the first rib, beyond the clavicle.))
• ((Left common carotid artery::More medial in the superior mediastinum; not behind the clavicle.))
• ((Left vertebral artery::Branch of subclavian; ascends in the neck, not retroclavicular.))

👩‍⚕️ Subclavian artery branches: VIT C+D → A — Vertebral, Internal thoracic, Thyrocervical, Costocervical, Dorsal scapular, then Axillary.

After CABG with bilateral internal thoracic artery harvest, a patient develops sternal dehiscence. What now provides the main blood supply to the sternum?

• ((Intercostal arteries::☑️ Anterior intercostal collaterals supply the sternum once both ITAs are gone.))
• ((Thoracoacromial artery::Supplies pectoralis and shoulder, not sternum.))
• ((Internal thoracic artery::Already harvested.))
• ((Lateral thoracic artery::Supplies serratus anterior and lateral breast.))

Elderly man post-bilateral ITA CABG develops left arm pain on hanging clothes. Cause?

• ((Stenosis of subclavian proximal to first branch::☑️ Subclavian steal — arm exercise reverses flow through ITA/vertebral.))
• ((Stenosis of subclavian distal to first branch::Would cause arm ischaemia without retrograde steal.))
• ((Axillary aneurysm::Causes embolic phenomena, not exertional pain in this pattern.))
• ((Cervical rib::Thoracic outlet symptoms but no link to ITA CABG.))

During needle aspiration at the 2nd intercostal space, midclavicular line, which is most likely damaged?

• ((Second intercostal nerve::☑️ Bundle sits in the costal groove of the 2nd rib, above the 2nd ICS.))
• ((Third intercostal nerve::Lies under the 3rd rib, below the puncture site.))
• ((Fourth intercostal nerve::Two interspaces too low.))
• ((Internal thoracic artery::Lies 1 cm lateral to the sternum — medial to the midclavicular line.))

👩‍⚕️ Always aim just above the rib below — vein, artery, nerve run in the inferior costal groove above.

Bleeding on chest drain insertion at the 5th ICS, mid-axillary line. Most likely source?

• ((Intercostal artery::☑️ Commonest cause of bleeding during chest drain insertion.))
• ((Left pericardiophrenic artery::Runs with phrenic nerve along the pericardium — too medial.))
• ((Lingula of the lung::Lung lacerations bleed into the pleural space but rarely the entry tract.))
• ((Right ventricle::Wrong side; would also be far more catastrophic.))

Stab injury at the left 5th ICS, sternal border. First structure injured?

• ((Pericardium::☑️ Lies immediately deep to the sternum at the 5th ICS.))
• ((Oesophagus::Posterior mediastinum; not reached from anterior stab here.))
• ((Aorta::Descending aorta is posterior; arch is higher.))
• ((Pleura::Reflects medially behind sternum but pericardium is the first chamber wall encountered here.))
• ((Pulmonary trunk::Lies higher, behind upper sternum.))

Deeper stab at the left 5th ICS sternal edge. Which heart chamber is most likely penetrated?

• ((Right ventricle::☑️ Forms most of the anterior cardiac surface — first chamber hit.))
• ((Left ventricle::Forms the apex and left border, not the front.))
• ((Right atrium::Forms the right border, behind the sternum on the right.))
• ((Left atrium::Most posterior chamber — sits against the oesophagus.))

Which structure lies posterior to the hilum of the right lung?

• ((Oesophagus::☑️ Runs in the posterior mediastinum, immediately behind the right hilum.))
• ((Inferior vena cava::Lies anteromedial, traversing the diaphragm at T8.))
• ((Superior vena cava::Anterior to the right hilum.))
• ((Thoracic duct::Posterior mediastinum but more midline, behind oesophagus.))

Which nerve runs posterior to the right lung hilum?

• ((Vagus nerve::☑️ Vagus is posterior, phrenic is anterior at both hila.))
• ((Phrenic nerve::Runs anterior to hilum on both sides.))
• ((Glossopharyngeal nerve::Does not enter thorax.))
• ((Accessory nerve::Innervates SCM and trapezius — does not enter thorax.))

Which vein arches forward over the right lung hilum to drain into the SVC?

• ((Azygos vein::☑️ Ascends in the posterior mediastinum and arches at T4 over the right hilum.))
• ((Superior vena cava::Sits anterior; receives the azygos.))
• ((Aorta::Arches at T4 but on the left, and it's an artery.))
• ((Pulmonary artery::Carries blood the other way and lies within the hilum.))

👩‍⚕️ At the hilum, anterior → posterior order is VAB: pulmonary Vein, pulmonary Artery, Bronchus.

A CT-guided biopsy targets the middle lobe of the lung. Best surface landmark?

• ((6th intercostal space, mid-axillary line::☑️ Middle lobe lies anteriorly between the horizontal and oblique fissures.))
• ((4th ICS, midclavicular line::Overlies upper lobe.))
• ((8th ICS, mid-axillary line::Overlies lower lobe / costodiaphragmatic recess.))
• ((2nd ICS, midclavicular line::Apex of lung — upper lobe.))

As the phrenic nerve enters the thorax, what lies medial to it?

• ((Brachiocephalic vein::☑️ The right phrenic descends lateral to brachiocephalic vein → SVC → pericardium.))
• ((Subclavian artery::The phrenic crosses anterior to the subclavian artery at the inlet.))
• ((Vagus nerve::Vagus lies posterior to the subclavian, away from the phrenic.))
• ((Internal thoracic artery::Branches off the subclavian and runs along the chest wall, not medial to phrenic.))

Costal parietal pleura is innervated by which nerve?

• ((Intercostal nerves::☑️ Somatic supply to costal and peripheral diaphragmatic pleura.))
• ((Phrenic nerve::Supplies mediastinal and central diaphragmatic pleura — referred to shoulder.))
• ((Recurrent laryngeal nerve::Supplies larynx below cords; no pleural role.))
• ((Vagus nerve::Visceral pleura sensation is minimal; not somatic.))

Which muscle is the principal driver of quiet respiration?

• ((Diaphragm::☑️ Generates ~70% of tidal volume at rest.))
• ((Intercostals::Assist; primary in deeper breathing.))
• ((Scalenes::Accessory muscles in forced inspiration.))
• ((Abdominal wall::Active in forced expiration only.))

When does pleural pressure become positive?

• ((Valsalva manoeuvre::☑️ Forced expiration against closed glottis raises intrathoracic pressure.))
• ((Quiet inspiration::Pleural pressure becomes more negative.))
• ((Quiet expiration::Pleural pressure returns toward –5 cmH₂O, still negative.))
• ((Resting end-expiration::Most negative point; –5 cmH₂O.))

A patient with high cervical cord injury still breathes. Where is the lesion below?

• ((Cricoid cartilage (C6)::☑️ Phrenic is C3–C5; lesions below this spare the diaphragm.))
• ((Hyoid (C3)::At phrenic origin; injury here threatens breathing.))
• ((Thyroid cartilage (C4–C5)::Within phrenic territory.))
• ((Mandible::Far above phrenic; not a spinal level marker.))

Post-laparoscopic appendicectomy patient has shoulder-tip pain. Cause?

• ((Phrenic nerve irritation (C3–C5)::☑️ Residual CO₂ irritates diaphragm; referred to C4 dermatome — shoulder.))
• ((Brachial plexus stretch::Caused by arm positioning; not classic for shoulder-tip referral.))
• ((Subacromial bursitis::Local pathology unrelated to laparoscopy.))
• ((Vagal stimulation::Causes bradycardia, not referred pain.))

All the following are in the posterior mediastinum EXCEPT:

• ((Cardiac splanchnic nerves::☑️ Arise in superior/middle mediastinum to reach the cardiac plexus.))
• ((Descending aorta::Posterior mediastinum classic.))
• ((Thoracic duct::Posterior mediastinum, between aorta and azygos.))
• ((Azygos vein::Posterior mediastinum on the right.))

Also, all are in the posterior mediastinum EXCEPT:

• ((Vagus nerve::☑️ Passes through superior and middle mediastinum; not formally "posterior".))
• ((Descending aorta::Posterior mediastinum.))
• ((Thoracic duct::Posterior mediastinum.))
• ((Vertebral bodies::Form the posterior boundary.))

During oesophagectomy the thoracic duct is injured. Where in its course is it most often damaged?

• ((Between diaphragmatic hiatus and superior mediastinum::☑️ Runs single, posterior to oesophagus — vulnerable here.))
• ((Diaphragmatic hiatus to abdomen::Below diaphragm — abdominal phase rarely injures it.))
• ((Middle mediastinum::Duct is not in middle mediastinum.))
• ((Right superior mediastinum::Duct has crossed to left by T4/5.))

Where should an injured thoracic duct be ligated?

• ((Aortic hiatus on the left::☑️ Single, well-defined channel here; above this it branches.))
• ((Oesophageal hiatus::Wrong opening — oesophagus passes here, not duct.))
• ((Vena caval hiatus::T8 opening for IVC, no duct.))
• ((Anterior to carotid sheath::Distal end has multiple tributaries; unreliable.))
• ((Pleural reflection::Anatomically vague and ineffective.))

Where does chyle accumulate after thoracic duct injury?

• ((Posterior mediastinum::☑️ Duct lies here; leak collects locally then into pleural space → chylothorax.))
• ((Anterior mediastinum::Contains thymus and lymph nodes; no duct.))
• ((Middle mediastinum::Pericardium and great vessels; no duct.))
• ((Pericardium::Tamponade pattern, not chylothorax.))

A pericardioperitoneal (pleuroperitoneal) membrane defect causes:

• ((Bochdalek congenital diaphragmatic hernia::☑️ Posterolateral diaphragmatic defect, usually left-sided.))
• ((Ectopia cordis::Midline sternal/pericardial fusion failure.))
• ((Hiatus hernia::Oesophageal hiatus laxity in adults.))
• ((Eventration of diaphragm::Muscular underdevelopment with intact membrane.))
• ((Dextrocardia::Abnormal cardiac looping in embryogenesis.))

Boundaries of the safe triangle for chest drain insertion?

• ((Pectoralis major, latissimus dorsi, line through the nipple::☑️ Standard BTS triangle.))
• ((Pectoralis minor, serratus anterior, line through nipple::Wrong muscles — pec minor is deep.))
• ((Pectoralis major, serratus anterior, costal margin::Costal margin too low — diaphragm/liver risk.))
• ((Pectoralis minor, latissimus dorsi, line through nipple::Pec minor is incorrect landmark.))

Stab posterior to right axillary line; CXR shows pneumothorax with fluid level. Management?

• ((Chest drain with suction::☑️ Haemopneumothorax — needs drainage and re-expansion.))
• ((Needle decompression::Reserved for tension pneumothorax with haemodynamic compromise.))
• ((Thoracentesis::Inadequate for ongoing air and blood drainage.))
• ((Chest drain without suction::Suction aids lung re-expansion in haemopneumothorax.))

Child with respiratory distress, raised JVP, tracheal deviation, absent breath sounds one side. Management?

• ((Needle decompression 2nd ICS, midclavicular line::☑️ Tension pneumothorax — clinical diagnosis, treat before imaging.))
• ((CXR then chest drain::Delays life-saving intervention.))
• ((Intubation::Will worsen tension pneumothorax until decompressed.))
• ((Pericardiocentesis::Wrong pathology — tamponade has bilateral breath sounds and no tracheal shift.))

25-year-old hit by van, hypoxic on 100% O₂, BP 100/80, HR 110, left hyper-resonant, trachea right. Action?

• ((Immediate needle decompression 2nd ICS, MCL::☑️ Tension pneumothorax — clinical diagnosis.))
• ((Urgent CT chest::Patient too unstable.))
• ((Chest drain in 5th ICS::Correct definitive step but AFTER decompression.))
• ((Intubate and ventilate::Positive-pressure will worsen tension.))

Young man stabbed left 5th ICS, stable but tachycardic, CXR normal. Next step?

• ((Echocardiogram / FAST::☑️ Excludes pericardial effusion / early tamponade — CXR misses both.))
• ((CT scan::Acceptable if stable but echo is faster and bedside.))
• ((Thoracotomy::Reserved for haemodynamic collapse.))
• ((Insert chest drain::Not indicated with normal CXR; doesn't assess pericardium.))

Proper site for pericardiocentesis in tamponade?

• ((Between xiphoid and left sternocostal margin::☑️ Subxiphoid approach avoids lung and coronary vessels.))
• ((2nd ICS midclavicular line::Site for tension pneumothorax decompression.))
• ((5th ICS mid-axillary line::Site for chest drain.))
• ((Apex beat::Apical approach risks LV and lung; not standard.))

👩‍⚕️ Beck's triad: hypotension + raised JVP + muffled heart sounds.

Patient with rib fracture becomes hypotensive and hypoxic immediately after intubation. Diagnosis?

• ((Tension pneumothorax::☑️ Positive-pressure ventilation converts simple to tension pneumothorax.))
• ((Haemothorax::Slower onset; less classically tied to intubation.))
• ((Haemopericardium::Possible from blunt trauma but less likely with rib fracture trigger.))
• ((Pneumothorax (simple)::Wouldn't cause profound shock immediately after intubation.))

25-year-old athlete with single uncomplicated rib fracture, vitally stable. Management?

• ((Analgesia and discharge::☑️ Isolated rib fracture in fit patient — no admission needed.))
• ((Chest drain::No pneumo/haemothorax — not indicated.))
• ((Admission and observation::Reserved for elderly or comorbidities.))
• ((Bupivacaine wound infiltration::Useful for multiple fractures but not standalone discharge plan.))

59-year-old COPD patient with single rib fracture, no pneumo/haemothorax, in pain. Best management?

• ((Admission, observation and analgesia::☑️ COPD reserve is poor — atelectasis and pneumonia risk.))
• ((Chest drain::No indication on imaging.))
• ((Analgesia and discharge::Unsafe given comorbidity.))
• ((Bupivacaine infiltration alone::Adjunct, not definitive plan.))

Patient with rib fractures 5–10, cyanosed and tachycardic. Management?

• ((Intubation and positive-pressure ventilation::☑️ Likely flail chest with pulmonary contusion — needs ventilatory support.))
• ((Analgesia alone::Inadequate for respiratory failure.))
• ((Chest drain alone::Treats pneumo/haemothorax but not the underlying contusion-driven hypoxia.))
• ((Surgical fixation::Considered later for selected flail segments, not the acute step.))

4 rib fractures with low pO₂ and normal pCO₂. Most appropriate next step?

• ((CPAP::☑️ Type I failure — recruits alveoli and improves oxygenation while sparing intubation.))
• ((SIMV (invasive ventilation)::Reserved for type II failure or exhaustion.))
• ((Analgesia alone::Necessary but does not correct hypoxia.))
• ((Chest drain::No pneumothorax described.))

30-year-old RTA: BP 80/40, HR 120, ribs 5–10 left move paradoxically, confused, SpO₂ 74%. Action?

• ((Intubation and positive-pressure ventilation::☑️ Flail chest + shock + hypoxia — definitive airway and ventilation.))
• ((Bupivacaine infiltration::Will not fix hypoxia or shock.))
• ((Chest drain anteriorly::Useful if pneumo/haemothorax but airway comes first.))
• ((Observation and high-flow O₂::Inadequate; patient is decompensating.))

50-year-old with cough, dyspnoea, weight loss and polyuria. Histological type?

• ((Squamous cell carcinoma::☑️ PTHrP-driven hypercalcaemia causes polyuria and dehydration.))
• ((Small cell carcinoma::Causes SIADH (hyponatraemia), not hypercalcaemia.))
• ((Adenocarcinoma::Peripheral; rarely paraneoplastic hypercalcaemia.))
• ((Large cell carcinoma::Less commonly paraneoplastic.))
• ((Adenosquamous::Rare; behaves more like adenocarcinoma.))

Smoker with cough, haemoptysis and cavitating central lesion. Diagnosis?

• ((Squamous cell carcinoma::☑️ Central, cavitates due to keratin necrosis, smoking-related.))
• ((Adenocarcinoma::Peripheral and rarely cavitates.))
• ((Small cell::Central but does not cavitate.))
• ((Mesothelioma::Pleural, not parenchymal.))

Smoker with peripheral mass and ground-glass opacities. Diagnosis?

• ((Adenocarcinoma::☑️ Most common lung cancer; peripheral with ground-glass on CT.))
• ((Squamous cell::Central and cavitating.))
• ((Small cell::Central, fast-growing.))
• ((Hamartoma::Benign, popcorn calcification.))

Mesothelioma is:

• ((Tumour of the pleura::☑️ Arises from mesothelial cells; asbestos exposure with long latency.))
• ((Vascular tumour::No — that's angiosarcoma.))
• ((Primary tumour of lung parenchyma::Mesothelioma is pleural, not parenchymal.))
• ((Epithelial tumour of tubular cells::Misleading — can be epithelioid but originates from pleura.))

Mediastinal mass with cervical lymphadenopathy. Characteristic histology?

• ((Reed-Sternberg cells::☑️ "Owl's eye" bilobed nuclei — pathognomonic of Hodgkin lymphoma.))
• ((Mitotic cells::Non-specific, present in many malignancies.))
• ((Giant cells::Granulomatous diseases — TB, sarcoidosis.))
• ((Plasma cells::Multiple myeloma or chronic inflammation.))
• ((Small round blue cells::Paediatric tumours — Ewing, neuroblastoma.))

Bilateral hilar lymphadenopathy + FNAC shows glandular cells, pleomorphic nuclei, neuroendocrine-negative. Diagnosis?

• ((Adenocarcinoma::☑️ Glandular cells, pleomorphic nuclei, no neuroendocrine markers.))
• ((Small cell::Neuroendocrine-positive; hyperchromatic nuclei with nuclear moulding.))
• ((Squamous cell::Keratinisation and intercellular bridges.))
• ((Mesothelioma::Pleural; calretinin/WT-1 positive; not glandular.))
• ((Hamartoma::Benign — cartilage and fat; no atypia.))

Smoker, 2 cm lung mass and 1 cm liver lesion (?haemangioma), no systemic signs. Next investigation?

• ((CT chest::☑️ Characterise primary lesion first; FDG PET follows if malignancy confirmed.))
• ((MRI liver::Useful for liver characterisation but lung primary takes priority.))
• ((FDG PET CT::Used after CT confirms suspicious primary.))
• ((Ultrasound::Inadequate for staging lung disease.))

65-year-old with bilateral cervical lymphadenopathy, SCC on biopsy, endoscopy negative. Best imaging to find primary?

• ((FDG PET scan::☑️ Best for occult primary detection by metabolic activity.))
• ((CT scan::Useful initially but PET more sensitive for unknown primary.))
• ((Barium swallow::Limited to oesophagus.))
• ((MRI::Useful for head/neck soft tissue but not whole-body screening.))
• ((Water-soluble swallow::Used for suspected perforation, not cancer.))

Lifelong smoker, sputum cytology shows squamous cells. Definition of this process?

• ((Reversible change of cell type in response to localised injury::☑️ Metaplasia — adaptive response to chronic irritation.))
• ((Irreversible change in response to pathogen::Describes dysplasia/neoplasia, not metaplasia.))
• ((Programmed cell death::Apoptosis.))
• ((Uncontrolled clonal proliferation::Neoplasia.))

70-year-old with bronchial cancer, morning headaches and vomiting. Best treatment?

• ((Dexamethasone::☑️ Reduces vasogenic oedema around brain metastases for rapid relief.))
• ((Mannitol::Used for acute herniation, not first-line for mets.))
• ((Whole-brain radiotherapy::Definitive treatment but slower; steroids first.))
• ((Lumbar puncture::Contraindicated with raised ICP.))

Female with hilar lesions, hypercalcaemia, low PTH. Diagnosis?

• ((Sarcoidosis::☑️ Granuloma macrophages activate 1α-hydroxylase → ↑ calcitriol → ↑ Ca²⁺; PTH suppressed.))
• ((Primary hyperparathyroidism::PTH would be high.))
• ((Lung cancer with PTHrP::PTH suppressed but no hilar bilateral lymphadenopathy pattern.))
• ((TB::Granulomatous but does not typically cause hypercalcaemia.))

45-year-old POD5 with fever, dyspnoea, chest pain and BP 80/30. Best diagnostic test?

• ((CT pulmonary angiography::☑️ Gold standard for PE; haemodynamic compromise suggests massive PE.))
• ((D-dimer::Only useful in low-probability cases.))
• ((V/Q scan::Alternative in renal failure or contrast allergy.))
• ((Echocardiogram::Supports diagnosis (RV strain) but not gold standard.))

Post-hip surgery, dyspnoea, tachycardia, chest pain, BP 140/90, no fever. Best test?

• ((CT pulmonary angiography::☑️ High clinical probability of PE — go straight to CTPA.))
• ((D-dimer::Will be raised post-op regardless; unhelpful.))
• ((Chest X-ray::Often normal in PE.))
• ((Arterial blood gases::Supportive (hypoxia, low CO₂) but not diagnostic.))

Post-anterior resection day 10, dyspnoea and cough, normal ECG. Best test?

• ((CT pulmonary angiography::☑️ Post-op PE until proven otherwise; CTPA confirms.))
• ((D-dimer::Non-specific post-op.))
• ((V/Q scan::Acceptable alternative but CTPA preferred.))
• ((Bronchoscopy::Wrong pathway.))

Post-aortic surgery: bilateral lung opacities, low BP, raised JVP, PCWP 20. Diagnosis?

• ((Cardiogenic pulmonary oedema::☑️ PCWP > 18 indicates raised left atrial pressure.))
• ((ARDS::PCWP would be < 18 (non-cardiogenic).))
• ((Tension pneumothorax::Unilateral changes and tracheal shift.))
• ((PE::PCWP normal and opacities not bilateral diffuse.))

Post-pancreatitis ICU patient: refractory hypoxia, bilateral infiltrates, PCWP 11, BP 100/65. Diagnosis?

• ((ARDS::☑️ Non-cardiogenic oedema; PCWP < 18, severe pancreatitis is a classic trigger.))
• ((Cardiogenic oedema::PCWP would be > 18.))
• ((PE::Localised perfusion defect, not bilateral diffuse infiltrates.))
• ((Volume overload::PCWP would be raised.))

Primary pathophysiology of ARDS?

• ((Reduced alveolar-capillary diffusion::☑️ Alveolar damage, oedema and inflammation impair gas exchange.))
• ((Increased lung compliance::Compliance is reduced — stiff lungs.))
• ((Reduced airflow through trachea::That's obstruction, not ARDS.))
• ((Hypercapnia from hypoventilation::ARDS is primarily a diffusion/oxygenation failure.))

Post-RTA, BP 170/110, agitated, CVP 15, PCWP 18, anuric 6 h. Most likely cause?

• ((Blocked catheter::☑️ Retention drives autonomic surge, hypertension and rising filling pressures.))
• ((Hypovolaemia::Filling pressures would be low.))
• ((Bilateral ureteric injury::Possible but blocked catheter is more common and easily fixed.))
• ((Renal failure::Filling pressures alone don't confirm — check the catheter first.))
• ((Heart failure::Possible but anuria + agitation + high BP screams retention.))

Spirometry change typical of COPD?

• ((Increased residual volume::☑️ Air trapping and hyperinflation are hallmarks.))
• ((Increased tidal volume::Tidal volume is usually unchanged or low.))
• ((Increased inspiratory capacity::Often reduced because of hyperinflation.))
• ((Reduced FRC::FRC is increased in COPD.))

Lung volume measured from maximum inspiration to maximum expiration?

• ((Vital capacity::☑️ VC = TLC – RV.))
• ((Total lung capacity::Includes residual volume.))
• ((Functional residual capacity::Volume after normal expiration.))
• ((Tidal volume::Volume per quiet breath.))

80-year-old, FEV₁ 1.8 L, FVC 2.1 L. Diagnosis?

• ((Pulmonary fibrosis::☑️ FEV₁/FVC = 0.86 → restrictive pattern.))
• ((COPD::Obstructive — FEV₁/FVC < 0.7.))
• ((Asthma::Obstructive and bronchodilator-reversible.))
• ((Bronchiectasis::Obstructive.))

Young girl, FEV₁ 2.0 L, FVC 3.6 L, reversible with bronchodilator. Diagnosis?

• ((Asthma::☑️ FEV₁/FVC = 0.56 obstructive, reversible — diagnostic.))
• ((Fibrosis::Restrictive, FEV₁/FVC > 0.7.))
• ((Lung collapse::Restrictive picture.))
• ((Asbestosis::Restrictive and irreversible.))
• ((COPD::Obstructive but not reversible.))

Tall, fit 180 cm man undergoing lung function tests. Most likely finding?

• ((Resting respiratory rate of 10/min::☑️ Fit individuals breathe deeper and slower at rest.))
• ((VC of 2 L::Normal VC in a tall fit male is 4.5–5.5 L.))
• ((PEF of 50 mL::Normal PEF is 500–600 L/min.))
• ((Reduced TLC::Increased in tall men.))

45-year-old, FEV₁/FVC ratio 95% but tidal volume 500 mL. Most likely diagnosis?

• ((Fibrosing alveolitis::☑️ High FEV₁/FVC = restrictive pattern.))
• ((COPD::Obstructive.))
• ((Asthma::Obstructive.))
• ((Emphysema::Obstructive.))
• ((Bronchiectasis::Obstructive.))

53-year-old with myasthenia gravis, dyspnoea, haemoptysis, and a mediastinal mass on CT. Diagnosis?

• ((Thymoma::☑️ Anterior mediastinal mass with myasthenia gravis — classic.))
• ((Lymphoma::Possible but myasthenia link is specific to thymoma.))
• ((Teratoma::Anterior mediastinum but no MG link.))
• ((Retrosternal thyroid::Anterior mediastinum but no MG link.))
• ((Bronchogenic carcinoma::Wouldn't classically cause MG.))

Revision summary

- Triangle of safety: pec major (anterior), lat dorsi (posterior), nipple line (inferior), apex of axilla. Drain above the lower rib — VAN sits in the inferior costal groove.

- Diaphragm openings: T8 IVC + right phrenic; T10 oesophagus + vagi; T12 aorta + thoracic duct + azygos. Phrenic = C3–5, "keeps the diaphragm alive". Shoulder-tip pain = C4 referred from diaphragm.

- Mediastinum: superior (above sternal angle) and inferior (anterior/middle/posterior). Anterior mass — 4T's (thymoma, teratoma, thyroid, terrible lymphoma).

- Hilum order: anterior → posterior = pulmonary Vein, Artery, Bronchus. Phrenic anterior, vagus posterior, both sides.

- Right main bronchus: shorter, wider, more vertical → aspiration.

- Tension pneumothorax: clinical diagnosis — hypoxia, hypotension, raised JVP, tracheal deviation away, hyper-resonance. Needle decompression 2nd ICS MCL → then chest drain.

- Massive haemothorax: > 1500 mL initially or > 200 mL/h → thoracotomy.

- Cardiac tamponade: Beck's triad → echo → subxiphoid pericardiocentesis.

- PE: Wells → D-dimer if low; CTPA gold standard. S1Q3T3 classic but rare.

- Lung cancer paraneoplastic: SCC → PTHrP/hypercalcaemia; SCLC → SIADH, ectopic ACTH, Lambert-Eaton.

- Pancoast tumour: Horner's + T1 wasting + brachial plexus arm pain.

- ARDS vs cardiogenic oedema: PCWP < 18 vs > 18 — the only discriminator that gives the answer.

- Thoracic duct: posterior mediastinum, crosses R→L at T4/5, ligate at left aortic hiatus.

- Bochdalek hernia: pleuroperitoneal membrane defect, usually left, neonatal respiratory distress.

- Thymoma + myasthenia gravis = the single highest-yield mediastinal pair.