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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 or produce new health problem(s) by itself. Therefore, a complication may be iatrogenic (i.e. literally brought forth by the physician).^[1]

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 concomitant 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 complicates the management of the causative condition (makes it more complex and challenging).^[2]

Complications are not to be confused with sequelae, which is a residual effect after the acute phase of an illness of injury. Sequelae can appear early or weeks to months later and due to the previous injury or illness. For example, a scar after a burn or dysphagia left after a stroke would be considered sequelae.^[3]

A complication is an adverse event that occurs due to a medical treatment or surgical procedure. Examples of complications would be bleeding after surgery, headache after a spinal tap, or an adverse drug reaction.

Examples of complications

• Generalized septicemia (infection of the blood) may occur as a complication of an infected wound or abscess.


• Allergic shock can be a reaction to several kinds of anesthetics, as a complication in a surgery.


• Fractured ribs and sternum may be a complication of cardiopulmonary resuscitation attempts in people suffering severe osteoporosis.


• 
  Miscarriage is the most common complication of early pregnancy.^[4]
  


• 
  Puerperal fever was a common complication of childbirth and used to kill a large proportion of mothers before the advent of antisepsis and antibiotics.


• 
  Diabetes mellitus may present a series of complications in an advanced or more severe stage, such as gangrene, diabetic foot, blindness, infections, etc.


• 
  Thrombosis in the heart or brain, causing stroke or acute myocardial infarction can be complications of blood coagulation disorders, phlebitis (inflammation of the veins), endocarditis and artificial heart valves
  


• 
  Eczema vaccinatum is a rare and severe complication of smallpox vaccination in people with eczema.


• Hepatotoxic dementia is a possible complication of hepatitis and liver cirrhosis.


• 
  Mental retardation is a common complication of untreated hydrocephalus.


• A paradoxical reaction to a drug; that is, a reaction that is the opposite to the intended purpose of the drug. An example is benzodiazepines, a class of psychoactive drugs considered minor tranquilizers with varying hypnotic, sedative, anxiolytic, anticonvulsant, and muscle relaxant effects; paradoxically they may also create hyperactivity, anxiety, convulsions etc. in susceptible individuals.^[5]
  


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  Erectile dysfunction and urinary incontinence which may follow prostatectomy.^[6][7]
  


• 
  Suicide is a common complication of many disorders and conditions that consistently affect a person's life negatively, such as major depressive disorder, schizophrenia, or substance abuse.


• Common complications of atrial fibrillation include stroke and the formation of a thromboembolus.^[8]
  


• Complications of outpatient drugs are very common and many patients experience worry or discomfort due to them.^[9]
  

Causes

There may be financial pressures which act in opposition to preventing complications. A United States study found that hospitals make more money per patient when patients have complications.^[10]

See also

• Adverse effect


• Classification of Pharmaco-Therapeutic Referrals


• Diagnosis


• Iatrogenesis


• Late effect


• Nocebo


• Placebo


• Prognosis


• Sequela

References

Further reading