Physical Examination · The Inheritance Principle

Reminder

You do not learn a new examination for every system.
You extend the one you already know.

The principle Every physical examination — regardless of system — follows the same four-step sequence: inspect, palpate, percuss, auscultate. This is the foundation. It never changes. What changes is what you look for within each step, and which findings matter most.

The analogy This principle has a precise equivalent in computer programming — called Object-Oriented Programming, or OOP. You do not need to know programming to understand the idea. The concept is simple, and it maps directly onto how medicine is organised.

The benefit A student who understands the inheritance structure of examination never walks into a new system feeling lost. They already have the base. They only need to learn what is added — and what is emphasised differently.

Object Oriented Programming · The Core Idea

"You do not rebuild the human every time you train a new doctor.
You do not rebuild the doctor every time you train a new pediatrician.
You extend what is already there."

A doctor is a human first. A paediatrician is a doctor first.
Each layer adds new skills — but never discards what came before. Physical examination works the same way. The base examination is always present. Each system extends it.

What is OOP?

Three concepts — explained without a single line of code

Object-Oriented Programming — the idea, not the language

A way of building things in layers, where each layer inherits from the one above

Concept 1 · Class

The Blueprint

A class is not the thing itself — it is the description of what the thing is and what it can do. It defines the properties and abilities shared by everything of that type.

You never treat a class directly. You create something from it — and that thing has everything the class described.

"Doctor" is a class. It describes what every doctor has: a medical degree, the ability to examine patients, the ability to prescribe. It is the blueprint — not the person.

Concept 2 · Inheritance

Building on What Exists

A child class inherits everything from its parent class automatically — without rewriting it. Then it adds whatever is new and specific to itself.

Nothing from the parent is lost. Everything is carried forward. New things are simply added on top.

"Paediatrician" inherits everything from "Doctor" — examination skills, prescription rights, clinical reasoning — and then adds: knowledge of childhood development, paediatric drug dosing, age-specific normal values, family-centred communication.

Concept 3 · Override

Same Method — Different Behaviour

Sometimes the child class takes a method from the parent and changes how it works — without removing it. The name is the same. The action is modified for the new context.

This is called overriding. The method still exists. It simply behaves differently here.

"Examine patient" exists in every doctor. But the paediatrician overrides the sequence — least distressing steps last, observe before touching, parent present throughout. Same method. Modified behaviour.

That is all OOP is — building in layers, carrying everything forward, and modifying only what needs to change. No programming knowledge required. The concept is the point.

The Doctor Hierarchy

Human → Doctor → Specialist — inheritance at every level

The class hierarchy — medicine edition

Each level inherits everything above — and adds what is specific to itself

👤

Base Class

Human

The starting point — everything else builds on this

language reasoning empathy communication manual dexterity

🩺

Child Class — inherits: Human

Doctor

Everything a human has — plus medical training

clinical examination differential diagnosis investigation interpretation prescribing clinical reasoning

Child Class — inherits: Doctor

👶 Paediatrician

Everything a doctor has — plus:

paediatric examination sequence age-specific normal values child development assessment paediatric drug dosing family-centred communication growth monitoring

Child Class — inherits: Doctor

🔪 Surgeon

Everything a doctor has — plus:

operative technique surgical anatomy pre/post-operative care wound management haemostasis anaesthesia liaison

Neither the paediatrician nor the surgeon re-learns how to examine a patient. They inherited that from "Doctor." They only learned what was new. This is the efficiency of inheritance — and it is exactly how physical examination is structured.

The Examination Hierarchy

Base examination → System examination — same structure, different emphasis

The Principle Applied to Clinical Skills

Every system examination inherits the base — and overrides what needs emphasis

The four steps of examination — inspect, palpate, percuss, auscultate — are present in every system. They are never discarded. What changes is what you look for within each step, and which findings carry the most weight in this particular system. Some findings present in the base are barely relevant here. Others become the centrepiece of the whole examination.

Base Class · All Systems

General Physical Examination

👁️

Inspect

Look before you touch. General appearance, colour, shape, movement, symmetry, scars, swelling

🤲

Palpate

Tenderness, temperature, texture, masses, organ size, lymph nodes, fremitus

🥁

Percuss

Resonance vs dullness — maps air, fluid, and solid tissue boundaries

🔊

Auscultate

Breath sounds, heart sounds, bowel sounds — movement of air and fluid through structures

Always included in every examination: general appearance hands & nails face & eyes vital signs lymph nodes peripheral perfusion

Child Class · inherits: General Examination Extends and emphasises respiratory-specific findings

Respiratory System Examination

Inherited — Inspection

General appearance, colour, distress

Chest shape — barrel chest, pectus, Harrison's sulcus emphasised

Chest wall movement — symmetry, recession, paradoxical emphasised

Respiratory rate and pattern — count for a full minute emphasised

Use of accessory muscles — sternomastoid, intercostal, subcostal emphasised

Tracheal position — central vs deviated emphasised

Inherited — Palpation

Lymph nodes, tenderness

Chest expansion — quantified, compared side to side emphasised

Vocal fremitus — transmitted vibration; increased in consolidation emphasised

Trachea — already noted in inspection

Emphasised — Percussion

Resonance mapping — all zones, front and back central step

Dull — consolidation, pleural effusion, collapse key finding

Hyper-resonant — pneumothorax, emphysema key finding

↺ Purpose here: mapping air vs fluid vs solid tissue in lung fields

Emphasised — Auscultation

Breath sounds — vesicular vs bronchial; absent central step

Added sounds — crackles (fine/coarse), wheeze, stridor, pleural rub key findings

Vocal resonance — aegophony, whispering pectoriloquy emphasised

↺ Purpose here: detecting airflow obstruction, fluid, consolidation

· Inherited from base

★ Emphasised in this system

↺ Purpose overridden here

Child Class · inherits: General Examination Extends and emphasises abdominal-specific findings

Abdominal Examination

Inherited — Inspection

General appearance, colour, distress

Abdominal contour — distension, scaphoid, visible mass emphasised

Visible peristalsis — obstruction, pyloric stenosis in infants emphasised

Scars — previous surgery, drain sites emphasised

Umbilicus — hernias, everted in ascites emphasised

Skin — jaundice, caput medusae, striae emphasised

Emphasised — Palpation

Superficial then deep — watch the face first central step

Liver — size, edge character, tenderness key finding

Spleen — start at RIF, move diagonally key finding

Kidneys — ballottement, bimanual emphasised

Masses — site, size, surface, mobility, pulsatility key finding

↺ Palpation is the centrepiece here — far more emphasis than in respiratory

Inherited — Percussion

Liver span — upper and lower borders emphasised

Spleen dullness — in the left flank emphasised

Shifting dullness — ascites detection emphasised

↺ Purpose here: mapping organ borders and detecting free fluid — not air/consolidation

Inherited — Auscultation

Bowel sounds — present/absent/tinkling emphasised

Bruits — renal artery, aorta emphasised

↺ Purpose here: detecting gut motility and vascular flow — not breath sounds

Less emphasis here than in respiratory — but never omitted

· Inherited from base

★ Emphasised in this system

↺ Purpose overridden here

The Paediatric Override

The same examination — with three layers of modification

When the patient is a child — the base is inherited, then modified

Sequence changed · New components added · Normal values overridden

Override · Sequence

The order changes

Observe before touching — frightened child gives false findings

Least distressing steps last — ears and throat after everything else

Auscultate early if child is quiet — opportunity may not come again

Use parent's lap as the examination table for small children

Adapt to the child's cooperation — be flexible, not rigid

Add · New Components

Paediatric-only additions

Fontanelle — open until 18 months; bulging = raised ICP

Growth parameters — weight, height, head circumference plotted on centile chart

Developmental assessment — gross motor, fine motor, language, social

Pubertal staging — Tanner staging where relevant

Feeding and nutrition assessment — especially in infants

Override · Normal Values

Reference ranges change with age

Heart rate — 140 is normal in a neonate; alarming in an adult

Respiratory rate — 40 is normal in an infant; abnormal in an adult

Blood pressure — lower in young children; rises through childhood

Liver edge — palpable 1–2 cm below costal margin is normal in infants

Fontanelle — open and flat is normal under 18 months

The paediatric examination does not replace the standard examination. It inherits it — and then overrides the sequence, adds new components, and resets the reference values. A student who understands inheritance knows exactly which parts are new and which parts are carried forward unchanged.

The Key Insights From This Analogy

What OOP teaches you about examination that memorisation cannot

Percussion is the same action everywhere — but the purpose is overridden. In the chest, you map air vs consolidation. In the abdomen, you map organ borders and free fluid. The technique is inherited. The interpretation is system-specific.

Auscultation is emphasised differently in each system. In respiratory, it is a centrepiece step. In abdominal examination, it is present but carries less weight. Inherited, not discarded — just weighted differently.

When you learn a new system, you only need to learn what is new. The four steps are already there. Ask: what does inspection look for here specifically? What does palpation reveal in this system that it does not in others? Fill the inherited frame with system-specific content.

When you examine a child, you override the sequence — not the content. The steps are the same. The order is adapted. The reference values are replaced. Everything else is carried forward from the standard examination unchanged.

Common Student Errors

What happens when the inheritance principle is not understood

Learning each system examination as a completely separate entity — memorising it from scratch rather than building on the shared base

Omitting auscultation in abdominal examination because it "feels less important" — inherited steps are never optional, only differently weighted

Applying the adult examination sequence rigidly to a frightened child — not recognising that the paediatric override changes the order, not the content

Using adult vital sign reference values when examining a child — not recognising that normal values are overridden at every age group

Forgetting growth parameters, fontanelle, and developmental assessment in paediatric examination — these are additions, not substitutions; the base is still present

Treating percussion as less important in abdominal examination — the purpose is overridden, but the step carries equal weight for detecting organomegaly, free fluid, and masses

Take-Home Message

"You never learn a new examination.
You extend the one you already have."

Inherit the base. Add what is system-specific.
Override what needs a different emphasis.
Reset the reference values when the patient is a child.

One base — many extensions Same steps · different emphasis Override ≠ discard

You do not learn a new examination for every system. You extend the one you already know.