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Gangrene - Bailey & Love's Short Practice of Surgery (28th Ed.)

Final Year MBBS Examination Notes - 25 Marks Each

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DEFINITION

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1. DRY GANGRENE (25 Marks)

Definition

Aetiology

• Gradual progressive arterial occlusion - commonest cause is atherosclerosis
• Other causes: Buerger's disease (thromboangiitis obliterans), Raynaud's disease, severe frostbite, ergotism
• The key feature is that occlusion is gradual, allowing collateral circulation to partially develop, preventing superadded infection

Pathology

• Gradual arterial obstruction leads to progressive ischaemia
• Venous return is also impaired; fluid cannot enter the dead tissue
• Tissue dries out, shrivels and becomes mummified
• Haemoglobin breaks down to iron sulphide - produces the black discolouration
• The part becomes hard, dry, shrunken, and wrinkled (like a mummy)
• Putrefaction is absent or minimal as the dry, avascular tissue resists bacterial growth

Clinical Features

Line of Demarcation

• A zone of demarcation between truly viable and dead tissue will eventually appear
• Separation is achieved by the development of granulation tissue between dead and living parts
• In dry gangrene, if blood supply of proximal tissues is adequate, the final line of demarcation appears in a matter of days and separation occurs neatly and with minimum of infection
• If bone is involved, complete separation takes longer; the stump tends to be conical as bone has a better blood supply than its coverings

Management

1. Conservative - Allow dry gangrene to demarcate spontaneously; no soaking or ointments needed
2. Treat underlying cause - Arteriography and revascularisation (bypass surgery or angioplasty) to improve proximal circulation
3. Surgical debridement - After demarcation, conservative amputation at the lowest viable level
4. Major limb amputation - Required when: blood supply cannot be improved, life-threatening sepsis develops, limb non-functional

Key Principle

Amputation in the presence of poor circulation will fail - gangrene will reappear in wound edges. The arterial supply must be assessed and improved first.

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2. WET GANGRENE (25 Marks)

Definition

Aetiology

• Sudden arterial occlusion (e.g., embolism) with no time for collateral circulation to develop
• The venous drainage continues briefly, allowing oedema and bacterial invasion
• Predisposing factors: diabetes mellitus, immunocompromised state, venous outflow obstruction

Pathology

• Sudden arterial blockage leads to rapid tissue necrosis
• The affected part is oedematous (venous return initially maintained)
• Putrefactive bacteria (saprophytes) invade the necrotic tissue
• Putrefaction releases gases - hence crepitus may be present
• Tissue liquefaction occurs
• Haemoglobin breakdown produces the black/green discolouration
• Toxins released by bacteria are absorbed systemically - patient becomes severely ill/septic

Clinical Features

Line of Demarcation

• In moist gangrene, the infection and suppuration extend into the neighbouring living tissue, causing the final line of demarcation to be more proximal than in dry gangrene
• If arterial supply to proximal living tissue is poor, the line of demarcation is very slow to form or may not develop at all
• Gangrene may spread to adjacent tissues or appear as 'skip' areas further up the limb on the other side of the foot, the heel, dorsum, or even the calf

Differences from Dry Gangrene

Management

1. Emergency surgery - Urgent debridement or amputation - this is a surgical emergency
2. IV antibiotics - Broad-spectrum covering aerobic and anaerobic organisms
3. Resuscitation - IV fluids, correction of septic shock
4. Control underlying disease - Especially diabetes mellitus
5. Revascularisation - Where possible, to improve limb salvage
6. Amputation level - Higher than in dry gangrene due to proximal spread of infection

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3. GAS GANGRENE (25 Marks)

Definition

Causative Organism

• Clostridium perfringens - Gram-positive, anaerobic, spore-bearing bacilli
• Widely found in nature, particularly in soil and faeces
• Spores survive in soil for years

Predisposing Factors / At-Risk Patients

• Immunocompromised patients
• Diabetic patients
• Patients with malignant disease
• Wounds containing necrotic or foreign material (anaerobic conditions)
• Military wounds - high-velocity missiles or shrapnel cause extensive tissue damage; the cavitation following passage of a missile creates a 'sucking' entry wound, leaving clothing and environmental soiling in addition to devascularised tissue
• Amputations performed for peripheral vascular disease with open necrotic ulceration

Pathogenesis

• Contaminated wound provides anaerobic environment ideal for Clostridium to germinate from spores
• Organism releases powerful exotoxins:
  • Alpha toxin (lecithinase/phospholipase C) - most important; causes haemolysis, myonecrosis, platelet destruction
  • Collagenase - breaks down connective tissue
  • Hyaluronidase - facilitates spread through tissue planes
  • Other proteases
• Gas (mainly CO₂ and H₂) produced by bacterial metabolism accumulates in tissues
• Rapid local spread → circulatory collapse → multi-organ failure

Clinical Features

Local Features

Systemic Features (Rapid Onset)

• High fever, tachycardia, hypotension
• Haemolysis and haemolytic anaemia
• Circulatory collapse
• Organ failure (renal, hepatic)
• Death if not treated promptly

Investigations

1. Plain X-ray - Gas in the soft tissues (pathognomonic)
2. CT scan - Extent of gas and tissue involvement
3. Wound swab - Gram stain (Gram-positive bacilli, no pus cells)
4. Blood cultures
5. FBC - Haemolytic anaemia, leucocytosis
6. Renal and hepatic function tests

Treatment (Summary box 5.9 / Summary box 33.9)

1. Surgical (Most Important)

• Radical and regular surgical excision of all affected tissue is the cornerstone of treatment
• Wound should be widely opened and all necrotic muscle excised
• Re-examine wound at 24-48 hours and repeat debridement as needed ("radical and regular" surgical excision)
• Early amputation may be life-saving - do not delay when limb is extensively involved
• Fasciotomy to decompress compartments

2. Antibiotic Therapy

• Large doses of IV penicillin (Penicillin G) - drug of choice
• Metronidazole - additional anaerobic cover
• Antibiotic prophylaxis should always be considered in patients at risk, especially when amputations are performed for peripheral vascular disease with open necrotic ulceration

3. Supportive

• High-dose oxygen (the organism is anaerobic; high-oxygen environment is bacteriostatic)
• Hyperbaric oxygen (HBO) - where available; inhibits toxin production and bacterial growth
• Aggressive IV fluid resuscitation
• Correction of haemolytic anaemia
• Intensive care management for organ support
• Antitoxin (where available)

Summary Box (Bailey & Love)

• Caused by C. perfringens
• Spores are present in soil
• Thrives in anaerobic conditions and produces many exotoxins
• Treat with radical and regular surgical excision
• Give oxygen and penicillin
• Early amputation may be life-saving

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QUICK COMPARISON TABLE - All Three Types

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IMPORTANT POINTS FOR 25-MARK ANSWER STRUCTURE

1. Definition (2 marks)
2. Aetiology / Causes (3 marks)
3. Pathology (5 marks)
4. Clinical Features (5 marks)
5. Investigations (3 marks)
6. Treatment / Management (5 marks)
7. Complications (2 marks)

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Female Sterilisation (Tubal Ligation) - Side Effects & Complications

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OVERVIEW

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A. IMMEDIATE / SURGICAL COMPLICATIONS

1. Anaesthesia-Related

• Most serious complications are related to general anaesthesia
• Risk of death: 1-2 per 100,000 sterilisations (largely anaesthesia-related)
• Regional/local anaesthesia is safer

2. Surgical Complications

3. Thermal/Electrical Burns (Electrocautery)

• Bowel burns from unipolar diathermy - can present days later with peritonitis
• Use of bipolar cautery significantly reduces this risk
• Thermal damage to adjacent structures (ureter, bowel)

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B. FAILURE RATES (Pregnancy After Sterilisation)

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C. ECTOPIC PREGNANCY (Critical Side Effect)

• If sterilisation fails, there is a significantly increased risk of ectopic (tubal) pregnancy
• The risk of ectopic pregnancy is highest with bipolar electrocoagulation failure
• 10-year ectopic pregnancy rate after sterilisation failure: up to 32% of all failures with bipolar cautery are ectopic
• Previous tubal surgery including sterilisation is listed as a major risk factor for ectopic pregnancy (Bailey & Love, 28th Ed.)
• Key teaching point: A woman who becomes pregnant after sterilisation must be assumed to have an ectopic pregnancy until proven otherwise

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D. LONG-TERM / LATE SEQUELAE

1. Menstrual Disturbances ("Post-Tubal Ligation Syndrome")

"Increased menstrual irregularity and pain are attributed to previous tubal sterilisation. Study of the problem is complicated by the fact that many women develop these symptoms as they age..." - Berek & Novak's Gynecology

• Heavier periods (menorrhagia)
• Increased menstrual pain (dysmenorrhoea)
• Cycle irregularity
• Intermenstrual bleeding

2. Pelvic Pain

• Chronic pelvic pain reported in some women post-sterilisation
• May relate to adhesion formation, hydrosalpinx, or congestion
• Difficult to distinguish from pre-existing conditions

3. Ovarian Function - Possible Disruption

• Interruption of blood supply to the ovary via the mesosalpinx may affect ovarian reserve (particularly with salpingectomy)
• Some studies suggest reduced ovarian reserve after salpingectomy
• Effect is minimal with clip/ring methods

4. Regret

• Regret is one of the most significant "side effects" of sterilisation
• Up to 20-26% of women express regret at some point
• Risk factors for regret:
  • Young age at time of sterilisation (highest risk: <25 years)
  • Change of partner
  • Death of a child
  • Financial/social pressure rather than personal choice
  • Sterilisation done at time of other procedure (post-partum) - decision made under emotional or physical stress
• Reversal (reanastomosis) success rates are variable (40-80%) and depend on method used and amount of tube remaining

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E. PSYCHOLOGICAL EFFECTS

• Generally high levels of satisfaction reported
• Some women report grief or loss after sterilisation, particularly if done under pressure
• Sexual dysfunction - rare; most studies show no significant change or improvement (relief from pregnancy anxiety)

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F. PROTECTIVE EFFECTS (Important for Exams)

Current recommendation: Opportunistic bilateral salpingectomy (complete removal of tubes) at the time of other pelvic surgery is increasingly recommended over tubal ligation, as it is more effective AND reduces ovarian cancer risk, since many "ovarian" cancers actually originate in the fallopian tube fimbriae. (Sabiston Textbook of Surgery)

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G. COMPARISON BY METHOD - Side Effect Profile

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SUMMARY TABLE

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EXAM KEY POINTS

1. Ectopic pregnancy after failed sterilisation is a surgical emergency - always suspect it
2. Regret is common and highest in women sterilised under 25
3. The "post-tubal ligation syndrome" is contested in the literature
4. Salpingectomy is now preferred over tubal ligation in many centres - more effective AND reduces ovarian cancer risk
5. Bipolar cautery has the highest long-term failure rate
6. Death rate is 1-2 per 100,000, mostly due to anaesthesia
7. Male sterilisation (vasectomy) incurs less risk and is more effective than female sterilisation (Sabiston)

• Perfect use: ~2% per year (2 pregnancies per 100 women)
• Typical use: ~13-18% per year

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Condom Failure Rate

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The Key Numbers

"Typical use" = real-world use with inconsistent or incorrect technique "Perfect use" = used correctly and consistently every single time

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What These Numbers Mean

• Male condom, typical use - 18%: Out of 100 women whose partners use male condoms for one year, 18 will become pregnant
• Male condom, perfect use - 2%: With perfect technique every time, only 2 per 100 women become pregnant in a year
• The enormous gap between 2% and 18% reflects human error - incorrect application, breakage, slippage, not used every time

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Comparison with Other Methods (from the Same Table)

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Why the Gap is So Large for Condoms

1. Incorrect application - putting it on after partial penetration, leaving no space at the tip
2. Breakage - using wrong lubricants (oil-based lubricants damage latex), expired condoms, wrong size
3. Slippage - during withdrawal, especially if erection subsides
4. Inconsistent use - not using it every time
5. Storage damage - heat (wallet, glove box), prolonged storage
6. Failure to use throughout - removed before ejaculation or not put on before any contact

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Additional Points for Exams

• STI protection: Male condoms are the only contraceptive method that also protects against sexually transmitted infections (HIV, gonorrhoea, chlamydia, etc.) - this is their major advantage over all other methods
• Latex allergy: Use polyurethane or polyisoprene condoms as an alternative
• Female condom: Larger failure rate than male condom with typical use (21% vs 18%), but empowers women to control protection; also provides STI protection
• Adolescents: Male condom is the most used birth control among adolescents with a failure rate of 18% typical use (Harriet Lane Handbook, 23rd Ed.)
• Dual protection: Condom + another method (e.g., OCP) is recommended for both contraception and STI prevention

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I-Pill (Levonorgestrel 1.5 mg) - Side Effects

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What is the I-Pill?

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SIDE EFFECTS

A. Gastrointestinal (Most Common)

"Nausea and vomiting occurred much less frequently with levonorgestrel alone (23.1% vs 50.5%, and 5.6% vs 18.8% respectively) compared to the combined EE/levonorgestrel method." - Berek & Novak's Gynecology

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B. Menstrual Disturbances (Very Common)

These menstrual changes are the most common complaint after taking the I-Pill and are normal and temporary.

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C. Other Common Side Effects

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D. Serious / Rare Side Effects

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E. Effect on Fertility

• No long-term effect on fertility - the I-Pill does not affect future fertility
• It should not be used as a regular contraceptive (hence "emergency" pill)
• Repeated use causes more frequent menstrual disturbances and is less reliable than regular contraception

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F. Effect in Obese Women (Important Exam Point)

• Reduced efficacy in obese women (BMI >30): Risk of pregnancy is 4.41 times higher in obese women taking levonorgestrel vs normal weight women (Berek & Novak)
• For obese women, ulipristal acetate (Ella, 30 mg) is preferred, OR a copper IUD (most effective emergency contraceptive of all)

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Comparison of Side Effect Profiles

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Practical Counselling Points

1. Take it as early as possible - most effective within 24 hours; effective up to 72 hours; WHO allows up to 120 hours with reduced efficacy
2. Nausea is common - taking it with food helps. If vomiting within 1 hour, repeat the dose and consider an antiemetic (domperidone/metoclopramide)
3. Next period may be irregular - this is normal and not a sign of pregnancy
4. If next period is >1 week late - do a urine pregnancy test
5. The I-Pill does NOT protect against STIs
6. It should NOT be used as routine contraception - it is less effective than regular methods and causes more cycle disruption with repeated use
7. Not an abortion pill - it works before fertilisation, not after

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