Pathology for non-pathologists

The Surgical (Pathological) sieve - VITAMIN ABCDEF

All diseases can only follow less than a couple dozen pathological processes

Vascular
Infective, Immunological
Trauma (physical, chemical, thermal, radiological) / Toxic
Autoimmune
Metabolic
Iatrogenic, Idiopathic
Neoplastic

Acquired
Behavioural
Congentital
Degenerative / Developmental
Endocrine
Functional

APPLIED PATHOLOGY

Each unique disease is really a combination of a specific anatomical region (gross, histological or biochemical) or physiological process combined with less than a couple dozen fundamental pathological process (see Pathological/Surgical sieve).

If you can identify the basic fundamental process you are more than half way there

THE CHRONOLOGY SUGGESTS THE PATHOLOGY

From this you can speculate on the likely causes to look for, the rate of progression of symptoms, the clinical features, the probable complications and the treatment for literally hundreds of conditions.
Achieving a diagnosis is much more than just crossing off a checklist of symptoms and signs
The order, time intervals and duration (secs-min-hr-days-wks-mnths-yrs) in which they occur provide a great deal of information that can be easily overlooked in the patient's history

Whilst pathologists are pre-occupied with the detailed visual descriptions (biochemical, histopathological, gross morphological) of disease, the more broadly relevant application of pathology comes from an understanding of the aetiology (cause) and mechanisms (pathogenesis).

BASIC PRINCIPLES OF PATHOLOGY

The onset of disease may be due to an underlying (predisposing) condition, unmasked by a precipitating event or continue unabated due to a perpetuating factor
Symptoms may also recur spontaneously and inexplicably
The condition can wax and wane gradually (relapsing-remitting) or abruptly recur (paroxsmal)
It may remain stable over time, abruptly or gradually worsen or resolve.
All of these observation represent the pathology concepts of natural history and complications.
A patient may present with symptoms purely of the disease, or of its complications
In the same way complications may occur soon after the onset of the disease or delayed (immediate, short-, mid-, long term complications)
The history can help pinpoint the likely point in the progression of a patient's illness.

A careful, thorough history mapping the time line of events from onset, progress and to current presentation provides essential clues to the basic pathological process

PATHOLOGIES AND CHRONOLOGIES

A rough approximation:

ACUTE / ABRUPT (seconds)

Vascular – thrombo-embolic, haemorrhagic
Toxic
Trauma (physical, chemical, thermal)
Immunological (Anaphylaxis)

SUB-ACUTE (hours-days)

Trauma (chemical, thermal, radiological)
Metabolic / Endocrine
Immunological (serum sickness)

CHRONIC (weeks-months-years)

Trauma (minor repetitive)
Vascular - arteriosclerosis
Metabolic / Endocrine
Neoplastic
Congenital
Developmental
Infection (chronic)
Immunological (cell mediated)

CHRONIC PROCESSES CAN BE

Persistent vs Episodic e.g. chronic osteoarthritis vs migrating polyarthritis
Resolving vs Stable vs Deteriorating e.g. common cold vs chronic asthma vs macular
Changes can be abrupt (paroxysmal), rapid, gradual e.g. dissecting aneurysm vs infected aneurysm vs expanding aneurysm
Episodes can be fleeting/transient or prolonged/protracted e.g. trigeminal neuralgia vs multiple sclerosis

Episodic = Relapsing/Remitting
Abrupt or rapid deterioration = acute on chronic

A change in pattern may indicate an acute complication or a new separate problem

Your diagnostic and management skills will improve markedly when you can elicit CHANGES in symptoms

"Discard in the first instance all attempts to identify or to name, and try instead to read the malady, tracing the symptoms to the seat of their cause, and discerning the nature of the morbid process by their character and course.

Sir William Gowers (Paediatrician, Neurologist)