Complication (medical)

Complication, in medicine, is an unfavorable evolution or consequence of a disease, a health condition or a therapy. The disease can become worse in its severity or show a higher number of signs, symptoms or new pathological changes, become widespread throughout the body or affect other organ systems. A new disease may also appear as a complication to a previous existing disease. A medical treatment, such as drugs or surgery may produce adverse effects and/or produce new health problem(s) by itself. Therefore, a complication may be iatrogenic, i.e., literally brought forth by the physician.

Medical knowledge about a disease, procedure or treatment usually entails a list of the most common complications, so that they can be foreseen, prevented or recognized more easily and speedily.

Depending on the degree of vulnerability, susceptibility, age, health status, immune system condition, etc. complications may arise more easily. Complications affect adversely the prognosis of a disease. Non-invasive and minimally invasive medical procedures usually favor fewer complications in comparison to invasive ones.

Disorders that are but are not caused by the other disorder are comorbidities. This conceptual dividing line is sometimes blurred by the complexity of the causation or the lack of definite information about it. The terms sequela and complication are often synonymous, although complication connotes that the resultant condition the management of the causative condition (makes it more and challenging).

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