Approach To Fever

Intro Fever also called Pyrexia, is one of the most common presenting complaints in medical practice.

It is defined as a body temperature that is above the normal range, for that individual, without any physiological cause to it.

In other words, temperature raise due to exercise or menstrual cycle doesn't count as fever.

This is usually above 38°C recorded by thermometer.

In this case, oral and rectal temperature readings are more accurate than axillary temp.

The most important thing to keep in mind is that fever, in it of itself, is not a disease, but rather a symptom that indicates an underlying disease process.

Mechanism of Fever: Body temperature is usually set to its normal range by the hypothalamus, which acts as a sort of thermostat.

When the body suffers from certain pathological processes, namely "inflammation", certain chemicals are released by the body, collectively called pyrogens, in other words, of which is interleukin-2.

Pyrogens set the thermoregulatory point of the hypothalamus to a higher temperature, thus resulting in fever.

The causes of fever can be divided into the broad categories of 1) Infections, which is the most common cause of pyrexia.

It can include bacterial, viral, fungal or parasitic infections.

2) Clots 3) Cancers 4) Auto Immune Diseases, and 5) Miscellaneous, which can include things like heat stroke, medications, brain lesions and thyroid storm to name a few.

Diagnosing the Cause of Fever

We have mentioned 5 categories of diseases that usually result in fever and each category consists of a multitude of possible diseases.

In order to narrow down our diagnosis, we need to do a thorough history and examination, and request appropriate lab investigations where relevant.

Fever is usually accompanied by other symptoms as well, which may guide the diagnosis of underlying disease.

Important questions to ask in history.

These can be broadly divided into 2 categories: 1) General Fever Related 2) Review of Systems

Fever specific questions include: the duration of fever, the timing of the fever: what time of day is it more prominent?

the character: Is it remitting or relapsing?

Is it accompanied by chills or rigors?

Is there night sweating?

Is there weight loss?

Is there pain anywhere?

Review of systems is a systematic approach to identify accompanying symptoms in other body organs.

This is especially important in identifying a possible focus of infection.

Ask relevant questions pertaining to each organ system and move from head to toe.

So for example, ask about headache? Neck stiffness? Eye pain? Skin rashes or itching?

Runny nose? Ear pain or discharge? Coughing? Sputum? Sore throat?

Pain on swallowing? Is there difficulty breathing or chest pain? Is there any abdominal pain?

Any change in bowel habits? Is there any lymph node enlargement? Any burning sensation while urinating?

Any discharge from genitals? Any recent injuries? Any muscle or bone pain? Any recent surgery?

Your history will be directed further by the patients' responses and will probably start moving towards a probable diagnosis.

Examine the relevant organ system in thorough detail.

You mainly need to decide which of the 5 categories does the disease belong to and which organ system is likely affected.

For example, acute fever with complaint of burning sensation during urination points to an infection of the urinary tract, whereas chronic low grade fever with anemia and weight loss might be indicating a hematological cancer.