How to study pathology: follow each process from cause to lesion to signs

The short answer

Study pathology as chains of cause and effect. For every process, follow it from the cause, through what happens in the cells and tissues, to the lesion it leaves and the signs and symptoms it produces. Learn the general processes first, cell injury and death, inflammation, repair, haemodynamic disorders, the immune response and neoplasia, because the diseases of the clinical years are built from them, and tie each one to the normal physiology it disrupts.

Then test yourself on those chains instead of rereading them: draw processes such as the inflammatory response from memory, explain why each sign appears, and work through cases from cause to findings and back. In a study by Woods, Brooks and Norman (2005), students who learned disorders through their underlying mechanisms still diagnosed 52% of cases correctly a week later, while those who learned which features go with which disease had dropped to 43%. Come back to each process the next day and at growing gaps until the exam.

Why pathology is hard, and why mechanisms help

General pathology is where the basic sciences meet disease. It asks you to hold a great many cells, mediators and molecular steps, and each one only makes sense as part of a process: what sets it off, what it does next, what it leaves in the tissue and what the patient notices. Learned as lists, the mediators of inflammation or the steps of carcinogenesis blur together within weeks; learned as chains, they can be rebuilt when you need them.

That’s more than a feeling. Nicole Woods, Lee Brooks and Geoffrey Norman (2005) taught 36 students four neurological disorders, either with explanations of the underlying mechanisms or with the probabilities linking each feature to each disorder. Straight afterwards both groups diagnosed equally well; a week later the mechanism group was still at 52% correct, while the other had dropped to 43%. In a follow-up with made-up diseases, students who had learned the cause behind each feature got 89% right a week later, against 78% for those who hadn’t (Woods, Brooks & Norman, 2007). Knowing the mechanism helps you remember the findings, and rebuild them when you’ve forgotten.

The method, a step at a time

Pathology is taught in very different ways: a review of 86 papers on pathology teaching found courses differing in when they come, how long they last, who teaches them and how they are assessed, with more and more of them folded into integrated curricula (Marshall, Cartwright & Mattick, 2004). Follow your own course’s order and exam. Within it, every topic, from necrosis to hypersensitivity, can be studied the same way: find the chain from cause to signs, draw it, and check that you can run it from memory in both directions.

1. Go over the normal first: the physiology and histology the process disturbs. Oedema is a change in the forces across the capillary wall; inflammation starts in the microcirculation; neoplasia is the cell cycle out of control.
2. Read for the chain. For each process, write down four links: the cause, the mechanism in cells and tissues, the lesion it leaves, and the signs and symptoms it produces.
3. Close the book and draw the chain on a blank page, as a flow diagram with arrows or as a sketch of the tissue at each stage. Then open the book and correct it in another colour.
4. Ask what if: change the cause, how strong it is or how long it lasts, and predict what follows. A brief, mild lack of oxygen leaves a swollen cell that recovers; a long, severe one ends in necrosis.
5. Explain it out loud without notes, as at an oral, saying why each step follows from the one before.
6. Try it on a case: start from a patient’s findings and work back to the process, or from a cause forward to what you’d expect to find.
7. Link it forward to the diseases in the clinical subjects that are built on it, and come back to it the next day and at growing gaps.

Cause, lesion, signs: three chains worked through

Cell injury from lack of oxygen. With too little oxygen, the cell makes less ATP; the sodium–potassium pump slows, sodium and water flow in, and the cell and its organelles swell, which can still be reversed. If it goes on, membranes are damaged, calcium floods in and enzymes break the cell down: necrosis. In the heart that is a myocardial infarction, and proteins that leak out of the dead cells, such as troponin, are what the blood test picks up.

Acute inflammation. An injury or a microbe sets off the release of mediators such as histamine, prostaglandins and cytokines; small vessels dilate and become leaky, and white blood cells roll along the vessel wall, stick to it, cross it and move towards the injury. Each cardinal sign comes from a step in that chain: redness and heat from the widened vessels, swelling from fluid leaking out of them, pain from mediators such as prostaglandins and bradykinin acting on nerve endings, and loss of function from all of these.

Fever. Cytokines released in inflammation, such as interleukin-1 and tumour necrosis factor, lead to prostaglandin E2 being made in the hypothalamus, which raises the set point for body temperature; the body then holds on to heat and makes more until it gets there. Aspirin and the other NSAIDs bring fever down by blocking prostaglandin synthesis: pharmacology you’ll learn later, already explained. Chains like these are what tie pathology to physiology before it and to the clinical subjects after.

Draw the processes from memory

Pathology is full of sequences that are easier to draw than to read: the steps by which white blood cells leave the vessels, the complement and coagulation cascades, the phases of wound healing, the path from a normal cell to an invasive cancer, the four types of hypersensitivity. Learn each well enough to draw it on a blank page and say what every step does and what can block it.

Draw with the book shut. Jeffrey Karpicke and Janell Blunt (2011) found that practising recall produced more learning than building concept maps with the text in front of you, even on questions that needed inference; in a later study, Blunt and Karpicke (2014) found that maps built from memory worked as recall practice too. So draw the inflammatory response from memory and then check it, rather than copying the textbook’s figure neatly.

Draw the tissue as well: a quick sketch of what each stage looks like under the microscope, the swollen cell, neutrophils crossing a venule, the granulation tissue of a healing wound. It joins general pathology to the histology you’ve learned and to the histopathology still to come.

In Breef, each process can be a note of its own, with the lecture slides or a photo of your drawing attached, linked with [[double brackets]] to the notes it depends on and the ones built on it: a note on acute inflammation links to the microcirculation, to fever and to the drugs that block prostaglandins, and Knowledge draws them all as one map, so you can see where a topic connects and where it doesn’t yet.

Cases and spaced review

Cases put the chains to work, but they don’t replace learning them. A systematic review of case-based learning in the health professions by Thistlethwaite and colleagues (2012), covering 104 studies, found that students overwhelmingly enjoy it and think it helps them learn, while the evidence on whether it teaches more than other methods was inconclusive. Use cases as a test: read one, say which process is at work and why each finding appears, and only then read the explanation.

What matters is saying how the science causes the clinical picture. Kulasegaram and colleagues (2015) taught 94 first-year students four disorders in one of four ways. All did equally well straight away, but a week later the students given cause-and-effect explanations linking the basic science to each clinical feature had barely slipped, while those given only the list of features, or the clinical features before the science, slipped the most. Putting the two side by side isn’t enough; spell out how one leads to the other.

Spread the practice out. In a randomised trial by Kerfoot and colleagues (2007), medical students who were sent short clinical cases and questions by email every week after a rotation remembered significantly more of those topics at the end of the year, with the largest effect for those whose rotation was six to eleven months earlier. Recall a process the day after you study it, again a few days later, then about a week later and every week or two until the exam: Cepeda and colleagues (2008) found the best gap grows with how long you need to remember, from about 20 to 40% of the time to the test when that was a week to about 5 to 10% when it was a year.

Breef can run that schedule for you. Record a lecture in a note and Breef writes it up, with what the lecturer stressed; the note comes back the next day and then at gaps fitted to how fast you forget, with three questions written from it each time; and once the course has its exam date, every note that would fade by then gets a last review in the days before.

A plan for the weeks before the exam

Pathology exams, the oral above all, test whether you can follow a process from cause to consequences, so the last weeks are for practising exactly that.

1. Six weeks out: list the topics on the syllabus, cell injury, inflammation, repair, haemodynamic disorders, immunology, neoplasia and the rest, and mark each by whether you can draw and explain it from memory, partly, or not yet. Start with cell injury and inflammation, since much of the rest builds on them.
2. Weeks six to three: a topic or two a day with the method above, starting each day by redrawing the processes from the days before.
3. Week two: cases and connections. Work through past exam questions and cases that cross topics, such as a wound that heals badly in diabetes or a chronic inflammation that ends in fibrosis, following each from cause to signs.
4. The last week: only recall. Draw every cascade and pathway from memory, explain each out loud, and look things up only to fix what you got wrong.
5. The day before: go over the processes you were shakiest on, and get a full night’s sleep.

Common mistakes

Learning mediators and molecules as lists. Know what each one does in the chain, and what would happen without it.

Studying pathology apart from physiology. Every process is a normal one gone wrong: go over the normal first.

Copying the textbook’s diagrams neatly. Draw them from memory, then correct them.

Stopping at the lesion. Follow every chain through to the signs and symptoms, which is what clinical subjects and exam cases ask about.

Reading cases without answering them first. Say what’s going on and why before you read the explanation.

Leaving immunology, or any big block, for the end. Spread it through the course like everything else.