notes by dr Claudio Italiano
We distinguish:
Acute mediastinitis:
a) esophageal perforation
b) bronchial perforation
c) spread of infections contiguous to the mediastinum or by blood
Before the development of modern cardiovascular surgery, cases of acute
mediastinitis usually arose from either perforation of the esophagus or from
contiguous spread of odontogenic or retropharyngeal infections. However, in
modern practice, most cases of acute mediastinitis result from complications of
cardiovascular or endoscopic surgical procedures.
Symptoms can mimic pneumonia.
This is a particularly devastating polymicrobial infection involving the neck and below to the mediastinum. It is often caused by an untreated odontogenic infection spreading to the mediastinum. It has a particularly high death rate and can lead to septic shock. The mortality rate is around 10-40% and is usually caused by multi-organ failure. Also, broad spectrum antibiotic therapy and intensive care is required along with the surgery. The culprits are usually Gram-positive bacteria and anaerobes, though rarely, Gram-negative bacteria are also present. This severe form represents 20% of acute mediastinitis cases
Chronic mediastinitis
They are characterized by
a) granulomatous forms such as tuberculosis, histoplasmosis, nocardiosis
b) fibrotic forms, infectious granulomatous processes
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Idiopathic or primitive mediastinal fibrosis is a rare form of fibrosis that is primarily located in the upper mediastinum and which, due to compression on the superior vena cava, leads to the onset of venous hypertension. The variant of the chronic fibrous - idiopathic mediastinitis - is in fact a very peculiar picture of chronic mediastinitis. In fact, it can also affect the retroperitoneum, the periorbital tissues, the biliary tract and the thyroid: the disease can therefore be expressed with "multi-organ" localizations that can also be simultaneous. Morphologically, it has the characteristics of a more or less dense fibrosis associated with inflammatory infiltration with lymphocytes and plasma cells associated with vasculitic changes. For this form, whose boundaries are still not completely defined, a possible autoimmune genesis is postulated starting from antigens derived from vasculitic lesions.
Secondary mediastinal fibrosis represents a severe complication of chronic
mediastinitis and acute chronic forms; in particular, purulent forms that evolve
into chronic pictures. It can in fact accompany, with significant frequency: the
severe forms of purulent mediastinitis secondary to pulmonary, mediastinal and
pleuropericardic inflammation; the complications of severe forms of tbc of the
lymph nodes of the pulmonary ail. Fibrosis is an event of a mainly phlogistic
nature that involves mechanical consequences for the compression performed on
the mediastinal structures, in particular on the major veins, on the nervous
trunks such as the phrenic nerve and the recurrent, on the bronchi and on the
trachea. The damage can also involve the pericardial sac, causing a constricting
fibrous pericarditis such as to compromise cardiac function. Mediastinal
fibrosis is always a very severe clinical and pathological picture, because the
possibilities for effective therapeutic measures are still very limited today.
Adhesive mediastinal-pericarditis arises as a result of radiating therapies
applied to the thorax for the treatment of mammary neoplasia, of mediastinal
malignancy. Pulmonary neoplasms with ilopolmonary metastases are other causal
events of fibrosis both in the mediastinum and in the pericardium. They are
pathological-clinical pictures peculiar to iatrogenic pathology that justify
their separate evaluation from non-iatrogenic fibrous mediastinites; also due to
the fact that they are clinically characterized by a dilated hypertrophic
cardiopathy, as well as by respiratory insufficiency, if the diaphragm is
involved.
The neoplastic infiltration of mediastinal tissues (ie neoplastic mediastinitis)
occurs mainly in cases of bronchopulmonary carcinoma, of carcinoma of the
esophagus, of thymomas, of malignant teratomas, of lympho- and
reticulo-mediastinal sarcomas. Often around metastatic neoplastic infiltrations,
which spread by casting along the pleura, the pericardium or the diaphragm, are
developing sclerous inflammatory processes, either reactive or caused by
infectious events resulting from perforation of the esophagus or
pleuro-pulmonary infections. Ultimately, a scoliopredoplastic mediastinal block
of fibrolardaceous appearance is formed, in which the lymph nodes are still
included and nerves, veins, arteries and bronchi are also incorporated.
The adipose mediastinites are not caused by inflammation, but are
pathological conditions generated by the accumulation of fat in the adipose
cells of the mediastinum, mostly in relation to the states of obesity.
Post-irradiative fibrous mediastinites are found in subjects subjected to very
intense radiant therapies undertaken for the treatment of mediastinal neoplasms:
they can cause sclerosis or mediastinal fibrosis, a condition of pathology
generated also by other therapeutic treatments - mediastinal androgenetic
fibrosis -; in any case, and usually, of a non-serious entity.
There are numerous pathology events that can configure radiological images of
mediastinal masses: generally they are pathological pictures that have
characteristic localizations.
- In the upper anterior region of the mediastinum, in front of the pericardial
sac and behind the sternum, anatomical site of the thymus, of the mediastinal
lymph-glands, of thyroid and parathyroid residues, most mediastinal masses are
found, being easier to observe those due to thymomas, lymphomas and teratomes;
while they are of infrequent observation, the masses connected with
proliferative events of thyroid and parathyroid residues - hyperplasias and
tumors;
- the region of the intermediate mediastinum is mainly home to lymph node masses
that may be phlogistic or neoplastic primitive - lymphomas - or secondary - in
particular ilopolmonary metastases -; as well as vascular neoplasms and
pleuro-pericardial or bronchogenic cysts;
- the region of the posterior mediastinum is home to neoplastic pathological
masses - mostly of a nervous nature - which generally give late clinical signs;
but also non-cancers such as meningoceles, diverticula of the esophagus and
myelo-meningoceles. In about half of the cases the confirmation of a
neoformation occurs mostly by chance for assessments carried out for clinical
suspects of different events.
Tumors, in clinical-pathological practice, represent the most frequent pathology,
constituting, together with cysts, about 90% of the mediastinal masses.