Wet gangrene occurs due to venous obstruction leading to tissue ischemia and bacterial proliferation in moist tissues. It presents as soft, swollen, foul-smelling black tissue without a clear line of demarcation. Diabetic foot gangrene results from peripheral vascular disease, neuropathy, and infection facilitated by hyperglycemia. Dry gangrene occurs from arterial insufficiency and presents as a dry, shrunken black tissue with a well-demarcated border. Gas gangrene involves Clostridium bacteria producing tissue-damaging toxins and crepitus. Prompt surgical debridement and antibiotics are critical for treatment.
3. SLO
• DEFINITION & TYPES OF GANGRENE
• WET GANGRENE – ETIOPATHOGENESIS, WITH SPECIAL REFRENCE TO
BOWEL & DIABETIC FOOT
• MORPHOLOGY & CLINICAL FEATURES OF WET GANGRENE
• ETIPATHOGENESIS,MORPHOLOGY & CLINICAL FEATURES OF DRY
GANGRENE
• ETIPATHOGENESIS,MORPHOLOGY & CLINICAL FEATURES OF GAS
GANGRENE
• DIFFERENCES BETWEEN WET & DRY GANGRENE
• REVISION WITH QUIZ
• CLINICAL CASE
5. WET GANGRENE
INTRODUCTION & EXAMPLES
This occurs in naturally moist tissues and organs such as the
mouth, bowel, lung, cervix, vulva
Examples:
• Gangrene of bowel due to strangulated hernia & Volvulus and
intussusceptions of GIT
• Diabetic foot
• Bedsores
6. WET GANGRENE
ETIOPATHOGENESIS
• Blockage of venous drainage, resulting in stasis of blood
with ischemia
• Also seen in organs with dual blood supply, like lung &
bowel , where one source of blood flow is blocked, while
other is open
• Affected organ like skin, GIT contain bacteria which
proliferate rapidly due to abundant nutrition and no host
defense as blood flow is blocked/poor
7. BOWEL NECROSIS & GANGRENE
ETIOPATHOGENESIS
• Some organs such as bowel with anastomosing blood supply,
or liver with a dual blood supply, are hard to necrose [infarct]
• Bowel is often affected when it is caught in a hernia and the
mesenteric blood supply is constricted by the small opening
to the hernia sac [photo in next slide]
• If the necrosed bowel is not resected, it will become
gangrenous
8. The small intestine is necrosed
The dark red necrotic bowel [ischemia with congestion]
contrasts with the pale pink normal bowel
If this necrotic area is not removed surgically, it will be
followed by gangrene [patient’s photo]
9. DIABETIC FOOT
ETIOPATHOGENESIS
Poorly controlled diabetes mellitus of long duration may lead
to gangrene of lower limb
Contributing factors are as follows:
• Ischemia secondary to atheroma,
• Peripheral neuropathy (atrophic changes in skin, neglect of
minor infections and injuries) and
• Immunosuppression with excess sugar in the tissues which
predisposes to infection
10. WET GANGRENE
PATHOLOGIC CHANGES
GROSS
• The affected part is soft, swollen, putrid, rotten and dark
and foul smelling
• The line of the demarcation between gangrenous segment
and viable tissue is generally not clear cut.
• Lumen of the bowel contains mucous and blood
15. WET GANGRENE
PATHOLOGIC CHANGES
MICROSCOPY
• There is Coagulative necrosis with abundant RBCs in
background
• Bacterial proliferation is present, this may cause some
liquefactive necrosis also
• Non specific inflammation may be present
• Ulceration of mucosa / skin may be seen
16. WET GANGRENE
CLINICAL FEATURES
• Affected part is black, may show ulceration [loss of epithelium]
• It is foul smelling & there is no clear line of demarcation
• Infection of epithelium & deeper tissues is usually prominent
• Classical features of inflammation may be absent in
immunocompromised host
• Signs & symptoms of underlying pathology are present
• Bacterial proliferation may lead to septicemia
• If gangrenous part is not surgically removed, septicemia may
be fatal
18. DRY GANGRENE
ETIOPAPATHOGENESIS
Most commonly due to ischemia of decreased arterial flow, due
to:
• Atherosclerosis
• Thromboangitis obliterans (Buerger’s disease)
• Raynaud’s disease
• Trauma
• Ergot poisoning
Seen in distal part of the limbs, specially lower limb
19. DRY GANGRENE
MORPHOLOGY
GROSS
• Line of demarcation is clear b/w dead & living tissues
• The affected part is dry, shrunken, and dark black resembling
the foot of a mummy, it smells bad, but less than wet
gangrene
• It is black due to liberation of hemoglobin from haemolysed
red blood cells; this Hb reacts with hydrogen disulfide
produced by bacteria, resulting in formation of black iron
sulfide
20. DRY GANGRENE
MORPHOLOGY
• At the line of separation the necrotic tissue may be
separated and fall off, if the gangrenous tissue is not
removed surgically (AUTOAMPUTATION)
MICROSCOPY
• There is coagulative necrosis of the tissue.
• The line of separation consists of inflammatory granulation
tissue
21. DRY GANGRENE
CLINICAL FEATURES
• Affected part is black in color with clear line of demarcation
• It is dry & shrunken
• It is malodorous
• Underlying pathology is present
• As bacterial proliferation is poor, risk of septicemia is low
• Gangrenous part may auto amputate
23. GAS GANGRENE
ETIOPATHOGENESIS
• Is a special form of wet gangrene caused by gas forming
bacteria ka Clostridia (gram positive anaerobic bacteria)
• Microorganism gains entry into the deep tissues like the
muscles in cases of road traffic accidents or war injuries
• It also occurs as a complication of operation on colon which
normally contains Clostridia perfringens
• Clostridia produce various toxins which produce necrosis and
edema locally.
24. GAS GANGRENE
PATHOLOGICAL CHANGES
GROSS
• The affected area is swollen, edematous and crepitant due to
accumulation of gas bubbles within the tissues.
• Subsequently the affected tissue becomes dark black and
foul smelling.
25. GAS GANGRENE
PATHOLOGICAL CHANGES
MICROSCOPICY
• There is both Coagulative & liquefactive necrosis.
• Large number of gram positive bacilli can be identified.
• At the periphery a zone of leucocytic infiltration, edema and
congestion are found.
• Capillary and venous thrombi are common
27. GAS GANGRENE
CLINICAL FEATURES
• Affected part is extremely painful
• It is tender & crepitant on palpation
• There is marked septicemia
• Needs aggressive treatment, both medical & surgical
• Untreated 100% mortality
28. DIFFERENCES BETWEEN DRY AND WET GANGRENE
FEATURE DRY GANGRENE WET GANGRENE
SITES COMMONLY LIMBS MORE COMMON IN BOWEL
ETIOPATHOGENESIS (MECHANISM) ARTERIAL OCCLUSION MORE COMMONLY VENOUS
OBSTRUCTION, LESS OFTEN
ARTERIAL OCCLUSION
GROSS PART IS DRY, SHRUNKEN AND
BLACK
PART IS MOIST, SOFT,
SWOLLEN, ROTTEN AND
DARK
PUTREFICATION LIMITED DUE TO VERY LITTLE
BLOOD SUPPLY
MARKED DUE TO STUFFING
OF ORGAN WITH BLOOD
LINE OF DEMARCTION PRESENT AT THE JUNCTION
BETWEEN HEALTHY AND
GANGRENOUS PART
NO CLEAR LINE OF
DEMARCATION
BACTERIA BACTERIA FEW NUMEROUS PRESENT
PROGNOSIS GENERALLY BETTER DUE TO LITTLE
SEPTICEMIA
GENERALLY POOR DUE TO
PROFOUND TOXEMIA
29. REVISION WITH QUIZ
• What is the cause of wet gangrene ?
• How gangrene occurs in bowel, despite good anastomosis?
• What factors contribute to gangrene in diabetics ?
• Enumerate some causes of dry gangrene
• What is the cause of gas gangrene?
• Why gangrenous part is crepitant?
• What is autoamputation?
• What is prognosis of gas gangrene ?
30. SHORT ESSAY – CLINICAL CASE
A 60 yrs old female is admitted with blackening of right big toe. On
examination there is swelling of the black area and the skin is showing
small areas of ulceration. Tissue around the black area is reddish in
colour. There is also a malodour. Lab tests – Hb 9 gm/dl, random
blood sugar – 320 mg/ dl . Ans the following :
• What is your diagnosis?, give two reasons.
• What is the etiopathogenesis of this condition?
• What is the cause of redness around the black area ?
• If crepitations develop in the black area; what does it
suggest ?
