DHPLC E-slide PATH 425-175 – Pathological changes at the microscopic level – Cervical CancerPhysiology is the study of the function of cells, tissues ,and organs and so pathophysiology looks at the detrimental changes in these functions. Impaired function can have a big impact on overall quality of life, and it is often these changes that lead us to go see a doctor to find out what is wrong.

An Example From Everyday Life

Let’s use the analogy of a bicycle to illustrate these terms.

A bicycle is made of many parts: wheels, chain, gears, seat, etc.  However, for a bike to function properly, every single part has to be made properly and work in cooperation with the other parts.

Imagine one day you went to ride your bike, but it wouldn’t move. You phone up your bike doctor and say, “My bike won’t move. Can you fix it?” You are describing a symptom affecting your bike that relates to a loss of function (pathophysiology).

The bike doctor might ask, “Can you turn the pedals?” This question helps narrow down the reasons for the malfunction. The options are: the pedals function normally (they turn with a bit of resistance), the pedals turn too easily, or the pedals don’t turn at all.

If the pedals turn too easily, it usually indicates a problem with the chain or the gears not being engaged. If the pedals don’t turn at all, it might indicate a problem with the brakes or something impeding the wheel.

You check the bike, and the pedals do turn. You relay that information to your bike doctor. They ask you to take a picture of the bike and send it to them so that they can see what is going on for visual assessment. This is the equivalent to your doctor sending you for x-ray or ultrasound imaging to see if the pictures will shed light on the problem.

You send the following image:

You don’t have to know much about bikes to recognize that the front wheel is bent. This bent wheel represents the underlying pathology for the disease this bike has. The fact that the bike won’t go and yet the pedals can turn are the changes in function or the pathophysiology of this bike disease. The treatment would involve getting a new wheel. If only we could replace our broken parts so easily!

When Are Other Health Professionals Brought In?

Some types of pathology are unique or obvious enough that your primary care provider (your family doctor, nurse-practitioner, ER doctor) is able to recognize what is going on without involving other health care providers. More commonly, however, as with pedals that won’t turn, there might be more than one underlying cause. A primary care provider will take your presenting signs and symptoms, and compare them to those of known diseases. They will then collect more information through visual observation (changes in appearance, colour); through palpation (for difference in size, position, and pain indicators); auscultation (listening with a stethoscope for changes in sounds) and simple measurements such as temperature, blood pressure, pulse, and oxygen saturation. These will give them more information to determine what other health professionals Careers in Health Care in BC need to be involved to identify the underlying disease process, or pathology, or if the changes are just a normal variation.

^{How Does Pathology Fit into a Visit to the Doctor by Jennifer Kong, Adrian Marcuzzi, & Theo Lam, licensed under All Rights Reserved}

A Clinical Example

Let’s say you go to the doctor because you are more thirsty than normal and urinating much more frequently than normal. The signs and symptoms you are presenting with are of an increase in thirst and urination. An increase in thirst is a symptom because it is subjective while an increase in urination can be a sign because you can objectively measure an increase in volume or urine or the number of times you need to urinate in a day (or night). Of the three most common causes of increased thirst and urination, one is a medical emergency (potentially fatal if not treated right away); one needs you to see a specialist; and one the doctor can treat. How does the doctor figure out the underlying pathology (cause) responsible for your pathophysiology (change in function)? There are three diseases we are looking at here: Type 1 diabetes, which can be fatal if untreated; Type 2 diabetes, which the primary care provider can treat; and diabetes insipidus, which needs further testing and specialist involvement. All three have increased urine output, which results in increased thirst. The first two have increased thirst and urination because there is too much sugar in the urine. In Type 1 diabetes, the sugar in the blood and urine is too high because the body has destroyed the pancreatic beta cells that produce insulin, which allows the body to store glucose in cells. In Type 2 diabetes, the body produces insulin, but the cells have a harder time recognizing it. As a result, the body cannot store glucose in the cells as readily, leaving excess in the blood (and urine). On the other hand, diabetes insipidus has nothing to do with sugar levels; instead, the body cannot concentrate the urine because it is missing or unable to recognize the protein vasopressin (antidiuretic hormone), which is produced by the hypothalamus and stored in the posterior pituitary gland. A simple dip-stick test of your urine can rule out diabetes insipidus if there is too much glucose in the urine. Lethargy, unresponsiveness, confusion, and coma are all symptoms that point towards Type 1 diabetes as opposed to Type 2. Therefore, the primary care provider has to evaluate at the overall clinical picture, recognize the potential differentials and determine the necessary steps to distinguish different underlying pathologies. Often, they will order blood work or send samples for testing, both of which involve medical laboratory technologist and pathologists. Alternatively, they might order imaging, which involves radiation technologists, ultrasound technologists, radiologists, and etc.

Pathology as a Medical Specialty

We saw from the previous example that pathology is also a medical specialty (you need to be a doctor). There are different specialties within Pathology. Anatomic Pathologists look at tissues and organs to determine disease based on changes in the appearance of cells, tissues and organs, both grossly and microscopically, and often specialize in a particular organ system. Forensic Pathologists determine the cause of death by examining the entire body, specific tissues and organs, and ordering toxicological tests for foreign substances that may have contributed. Neuropathologists  specialize in the nervous system and muscle pathology. Hematopathologists specialize in changes to the blood cells and has Transfusion medicine as a subspecialty. Medical Microbiologists isolate, grow and identify micro-organisms that cause disease, along with which treatments may be effective against them. They work with  Infectious Disease specialists to identify, treat communicable diseases, and prevent their spread in the community. Medical Biochemists and Clinical Chemists oversee the laboratory testing of chemical substances in the body, either produced by the body (endogenous) or ingested (exogenous), including selecting the optimal methods to use, identify the test limitation, and establishing normal reference ranges for a given test.

Pathologists do not work in isolation. They are supported by a team of Medical Laboratory Technologists, who prepare specimens, perform the tests, and troubleshoot problems with techniques and instrumentation. Medical Laboratory Technologists cover a wide range of areas from phlebotomy (drawing blood), to preparing histological samples, to growing up microorganisms, to running complex chemical analysis equipment. Therefore, they tend to specialize as well.

Section Review

The fact that we live with injury and disease has led to disciplines focused on studying changes happening at the cellular, tissue, and organ levels. Pathophysiology looks at the functional changes, while pathology as a whole looks at both functional and structural changes associated with injury and disease. Pathologists and Medical Laboratory Technologists are closely involved with confirming the diagnosis of diseases and monitoring ongoing changes with disease progression or remission.