Gangrene:

Gangrene is characterized by extensive necrosis superadded with putrifaction.   Visit: Necrosis

Dry gangrene (mummification):

This is due to arterial obstruction, commonly in old age with atherosclerosis followed by thrombosis of the large and medium size arteries of the limbs, slowly over a long period. Venous drainage is normal.    Visit: Hemostasis and Thrombosis

Dry gangrene usually starts in the most distal part of the extremities.

Skin of the affected areas is dry, shrivelled and black like that of mummy due to diffusion of hemoglobin from small vessels into the extra-vascular space (Example:  Senile gangrene, diabetic gangrene).

Gangrene extends upwards till it reaches a point where circulation is sufficient to keep the part alive.

This junction of living and dead tissue is called line of  demarcation and consists of granulation tissue formed due to irritation of dead tissue.

Granulation tissue erodes the dead tissue finally causing complete detachment (spontaneous amputation).

In younger age, it is seen in thrombo-angiitis-obliterans (Buerger’s disease)- due to inflammatory occlusion of both artery and vein.

Wet Gangrene:

This is due to obstruction of vein with intact arterial supply (Example: strangulated loop of gut in hernia, prolonged application of tourniquet etc).

Gangrene is distal to the site of obstruction.

Marked edema allows rapid growth of bacteria often with gas formation.

Absorption toxin causes profound toxemia.

Gas Gangrene: Gas Gangrene:click here

This is rapidly spreading tissue necrosis, often involving muscle as in crush injury in road accident.

This is due to infection by saccharolytic and proteolytic Clostridia along with other pyogenic bacteria.

This may be rarely seen in suppurative appendicitis, strangulated loop of intestine, puerperium. 

Affected muscles and soft tissues are edematous, crepitant on palpation due to gas bubbles in the tissue and commonly develops profound toxemia and septicemia.

    Microscopic features of Gangrene:

i) Absence of inflammation.

ii) Cell shrinkage.   

iii) Chromatin -condensation and fragmentation.

iv) Cellular blebbing and fragmentation are followed by removal by shedding or phagocytosis by macrophage.

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Anatomy and Histology of the Normal Lung and Airways

Examination of pulmonary and pleural biopsies

Useful chromatic and immunostains in pulmonary pathology

Percutaneous Needle and Trucut Biopsy Specimen

Bronchial Biopsy Specimen

Transbronchial Biopsy Specimen

Open lung biopsy