★Edema is abnormal accumulation of fluid in the interstitial tissue or body cavities.
★Causes:-
1-Increased intravascular hydrostatic pressure :due to venous obstruction.
2-Increased vascular permeability :as in acute inflammation.
3-Decreased plasma oncotic pressure :due to protein loss as in renal disease or decrease protein synthesis as in liver disease.
4-sodium retention:as in heart failure.
5-lymphatic obstruction:due to:-
Filariasis.
Tumor infiltration.
Surgical removal of LNs.
Irradiation.
Inflammation (Lymphangitis).
Congenital absence of the lymphatics.
★Distribution of edema:-
1-Generalized:
Cardiac edema.
Renal edema.
Nutritional (Hypoproteinemia)edema.
2-Localized:
Inflammatory edema.
Obstructive edema:
Lymphatic(Lymphedema).
Venous.
★General pathological features of edema:-
*Sites:
Subcutaneous tissue:most common site.
Serous sacs:pleura,peritonium and pericardium.
Lung:in left sided heart failure causes dyspnea.
Brain:localized or generalized cause headache and brain herniation.
*Pitting: subcutaneous tissue edema may be pitting or non-pitting.
*Edema fluid may be :
Transudate:in generalized edema and localized obstructive edema.
Exudate:in inflammatory edema.
Lymph: in lymphatic obstructive
*Anasarca is: Extensive generalized edema involving serous sacs.
Hydrothorax is: accumulation of transudate in pleural sac.
*Hydropericardium is : accumulation of transudate in pericardial sac.
*Hydroperitonium(ascitis) is: accumulation of transudate in peritonium.
Hydrocele is: accumulation of transudate in tunica vaginalis around testis.
*Hydroarthrosis is: accumulation of transudate in joint cavity.