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Amniotic Fluid and Its Disorders in Obstetrics

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1. What Is Amniotic Fluid?

• Cushioning - protects the fetus from mechanical trauma
• Bacteriostatic properties - helps maintain a sterile intrauterine environment
• Space for movement - allows fetal mobility and supports normal development of lungs and limbs
• Diagnostic access - provides fetal cells and metabolic byproducts; used in amniocentesis (first performed in 1956 for sex determination)

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2. Volume of Amniotic Fluid

• Volume increases at 10 mL/week early in fetal period, peaks at 50-60 mL/week at 19-25 weeks
• After 34 weeks, volume falls at 60-70 mL/week at 40 weeks
• The late-pregnancy decline is a physiologic progression, not an aberration

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3. Composition of Amniotic Fluid

• Isotonic with maternal/fetal plasma
• Minimal protein
• Very low oxygen tension
• High concentration of sugar alcohols (product of anaerobic metabolism)
• Arises as a transudate of plasma - through nonkeratinized fetal skin or across uterine decidua/placenta

• Fetal urine becomes the major component (fetus produces dilute urine)
• AF osmolality falls to ~85-90% of maternal serum osmolality (drops by 20-30 mOsm/kg with advancing gestation)
• AF urea, creatinine, and uric acid increase to 2-3x fetal plasma levels
• The entire volume of AF turns over on a daily basis - a highly dynamic system

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4. Production and Resorption - Sources and Sinks

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5. Ultrasound Assessment of AF Volume

• Maximum Vertical Pocket (MVP) - single deepest pocket
• Amniotic Fluid Index (AFI) - sum of MVP in four uterine quadrants

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6. Disorders of Amniotic Fluid

A. Polyhydramnios (Hydramnios) - Excess AF

• Impaired fetal swallowing - neurologic abnormalities, obstructions
• GI anomalies - esophageal atresia, tracheoesophageal fistula
• Respiratory anomalies - congenital diaphragmatic hernia
• Maternal diabetes mellitus - fetal hyperglycemia leads to osmotic diuresis
• Fetal anemia - increased cardiac output and urine flow
• Twin-to-twin transfusion syndrome (TTTS) - recipient twin
• Idiopathic - no identifiable cause in many cases
• Hypoproteinemia with decreased maternal plasma oncotic pressure

• Preterm birth (PTB): 18.5% with mild, 21.8% with moderate, 14.3% with severe polyhydramnios
• Uterine overdistension triggers inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8, CCL2, PGE2, PGF2α) - causing preterm labor
• The underlying cause (congenital malformations, diabetes) determines PTB risk more than the fluid volume itself
• Maternal discomfort, dyspnea
• Malpresentation
• Cord prolapse
• Placental abruption (after rapid decompression)

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B. Oligohydramnios - Reduced AF

• Renal agenesis / bilateral renal anomalies - no urine production (Potter sequence)
• Posterior urethral valves / lower urinary tract obstruction - leads to oligohydramnios, pulmonary hypoplasia, renal dysplasia, Potter facies, clubfeet
• Placental insufficiency / uteroplacental insufficiency - reduced fetal perfusion reduces urine output
• Post-term pregnancy - AF falls 33%/week after 41 weeks (physiologic)
• Rupture of membranes (PPROM/PROM) - loss of AF
• Maternal dehydration - osmotic mechanism; rehydration can reverse it

• Pulmonary hypoplasia - AF is required for normal lung development; severe oligohydramnios early in pregnancy is particularly dangerous
• Limb deformities - restricted fetal movement
• Potter sequence - renal agenesis → oligohydramnios → pulmonary hypoplasia, Potter facies (flat nose, low-set ears, epicanthal folds), limb contractures
• Fetal distress - cord compression, fetal hypoxia
• Perinatal mortality - higher with severe oligohydramnios
• Intrauterine growth restriction (IUGR) association

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C. Amniotic Fluid Embolism (AFE)

1. Hemodynamic compromise (cardiovascular collapse)
2. Respiratory compromise
3. Disseminated intravascular coagulopathy (DIC)

• Sudden cardiovascular collapse and cardiac arrest
• Severe hypoxia
• DIC with hemorrhage
• Often occurs during labor, delivery, or within 30 minutes postpartum

• Early intubation + 100% O2 + PEEP
• High-quality CPR immediately for cardiac arrest
• If AFE occurs before delivery → emergent cesarean delivery to improve maternal resuscitation and fetal survival
• Large-bore IV access + arterial line
• Transesophageal echocardiography after intubation - to manage pulmonary hypertension and cardiac failure
• Pressors, inotropes, pulmonary vasodilators as needed
• ECMO - consider after prolonged arrest or severe ventricular dysfunction unresponsive to medical management
• Massive transfusion: Packed RBCs : FFP : Platelets in 1:1:1 ratio
• TEG / ROTEM point-of-care testing for coagulopathy guidance
• Note: Recombinant activated Factor VIIa is controversial - a systematic review found it may worsen outcomes in AFE

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7. Summary Table

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Breast - Complete Surgery Notes

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A) Classification of Breast Tumors

I. Benign Tumors

1. Fibroadenoma - most common benign lump in young women
2. Cystosarcoma phyllodes (Phyllodes tumor) - benign/borderline/malignant
3. Lipoma
4. Duct papilloma - solitary or multiple (papillomatosis)
5. Adenoma (tubular, lactating)
6. Granular cell tumor

II. Malignant Tumors (Carcinoma)

• Ductal Carcinoma In Situ (DCIS)
• Lobular Carcinoma In Situ (LCIS) - high-risk benign lesion per 8th AJCC edition

• Invasive Ductal Carcinoma (IDC / No Special Type) - most common (70-80%)
• Invasive Lobular Carcinoma (ILC)
• Mucinous (colloid) carcinoma
• Tubular carcinoma
• Medullary carcinoma
• Papillary carcinoma
• Inflammatory carcinoma (T4d)
• Paget's disease of nipple

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B) Carcinoma Breast

Etiopathogenesis (Risk Factors)

• Female sex, increasing age
• Early menarche, late menopause (prolonged estrogen exposure)
• Nulliparity, first pregnancy after age 35
• Family history / BRCA1 (chr 17q21) or BRCA2 (chr 13q12.3) mutation
  • BRCA1: 50-85% lifetime breast cancer risk + 40% ovarian cancer risk
  • BRCA2: 50-60% lifetime risk + 20% ovarian cancer risk
• Previous breast cancer, atypical ductal/lobular hyperplasia (ADH/ALH)
• Dense breast tissue

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Clinical Features

• Painless lump in the breast (most common presentation) - usually upper outer quadrant
• Nipple discharge (bloody)
• Nipple retraction / inversion
• Skin changes: dimpling, puckering, peau d'orange
• Axillary lump (lymph node metastasis)

• Hard, irregular, non-tender, fixed mass
• Skin dimpling (shortened Cooper's ligaments due to desmoplastic reaction)
• Peau d'orange (orange peel appearance) - dermal lymphatic obstruction
• Nipple retraction / Paget's disease of nipple (eczematous lesion)
• Inflammatory carcinoma: diffuse erythema + skin edema >1/3 of breast (T4d)
• Palpable axillary or supraclavicular nodes

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Spread of Breast Carcinoma

• Invades adjacent breast parenchyma
• Skin → ulceration, satellite nodules
• Deep → pectoralis major, serratus anterior, chest wall
• FGF → desmoplastic reaction → collagen shortening → Cooper's ligament retraction → dimpling/nipple retraction

• Axillary nodes (primary drainage - especially outer quadrant tumors)
  • Level I: lateral to pectoralis minor
  • Level II: behind pectoralis minor
  • Level III: medial to pectoralis minor (apical nodes)
• Internal mammary nodes - especially inner quadrant tumors
• Contralateral axillary nodes (via subdermal lymphatics or internal mammary interconnections)
• Supraclavicular nodes

• Bones (most common - spine, pelvis, femur, skull)
• Lungs (nodules, pleural effusion)
• Liver
• Brain
• Adrenals

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TNM Staging (UICC/AJCC 8th Edition)

• M0: No distant metastasis
• M1: Distant metastasis present

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Prognostic Factors

• Small tumor size (T1)
• Node-negative (N0)
• Low histologic grade (Grade 1)
• ER/PR positive
• HER2 negative
• Low Ki-67 (<20%)
• Luminal A subtype
• No LVI (lymphovascular invasion)

• Large tumor, N2/N3
• High grade (Grade 3)
• TNBC (Triple Negative)
• HER2 positive (before targeted therapy era)
• High Ki-67 (>30%)
• Presence of LVI
• Young age at presentation
• BRCA1 mutation

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Management of Breast Cancer

Surgery:

• Wide Local Excision (WLE) - up to 20% breast volume
• Oncoplasty - for >20% volume loss:
  • Level 1: Volume displacement (local tissue rearrangement)
  • Level 2: Volume replacement (local/distant flap)
• Must always be followed by adjuvant radiotherapy

• Simple mastectomy
• Modified Radical Mastectomy (MRM/Patey's):
  • Removal of breast + pectoralis minor + axillary node dissection (Levels I-III)
  • Pectoralis major is preserved
• Radical mastectomy (Halsted's): Now rarely performed; removes pectoralis major too

• Sentinel Lymph Node Biopsy (SLNB): First-line for clinically node-negative patients; sentinel node = first echelon of axillary nodes, identified with blue dye and/or radioisotope
• Axillary Lymph Node Dissection (ALND): For SLNB-positive patients

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Breast Reconstruction (after MRM)

• Immediate (at time of mastectomy)
• Delayed (months to years later)

• Direct implant (silicone/saline)
• Tissue expander followed by permanent implant

• Local flap for nipple, tattooing for areola

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Radiotherapy:

• Mandatory after BCS
• After mastectomy if: tumor ≥5 cm, skin/chest wall involvement, LVI, Grade 3, node-positive
• Dose: 45-50.4 Gy in 25 fractions OR hypofractionation 40-42.5 Gy in 15-16 fractions
• Axilla NOT irradiated after ALND (risk of lymphedema)

Adjuvant Systemic Therapy:

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C) ANDI - Aberrations of Normal Development and Involution

1. Development (age 15-25 years)
2. Cyclical hormone-related change (age 15-50 years)
3. Involution (age 35-55 years)

ANDI Classification Table:

Pathology:

• Hyperplasia: >2 cell layers in duct/acini lining; may be typical or atypical
• ADH → DCIS: If ADH involves >2 ducts or >2 mm - reclassified as DCIS
• Papilloma: Fibrovascular core + papillary projections; solitary (RR 1.5-2) or papillomatosis (RR 3)
• Cysts: Kinking of ductules during involution → microcyst → macrocyst

Clinical Features of ANDI:

• Cyclical breast pain (mastalgia) - peaks day 14, worst day 27-28, relieved with menses
• Nodularity (lumpiness) - upper outer quadrant, bilateral, cyclical
• Discrete lump - fibroadenoma in young, cyst in middle-aged
• Nipple discharge

Treatment:

• Reassurance (most cases)
• Mastalgia: Evening primrose oil, Tamoxifen, Danazol, LHRH analogues
• ADH/ALH: Close surveillance (RR 4-5x for developing cancer)

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VSAQ - Fibroadenoma of Breast

• Definition: Benign tumor of the breast derived from the terminal duct lobular unit (TDLU); represents an aberration of lobular development (ANDI)
• Epidemiology: Most common benign breast lump in women aged 15-35 years; accounts for ~13% of all palpable breast masses
• Cause: Lobular proliferation in response to estrogen

1. Simple fibroadenoma - <5 cm, common
2. Giant/Juvenile fibroadenoma - >5 cm, in adolescents
3. Complex fibroadenoma - contains cysts, sclerosing adenosis, epithelial calcifications (slight ↑ cancer risk)
4. Multiple fibroadenomas - bilateral, familial

• Smooth, rubbery, well-defined, mobile lump ("breast mouse")
• Non-tender
• Usually in upper outer quadrant
• No skin changes, no node involvement

1. Clinical examination
2. Ultrasonography - smooth, hypoechoic, well-defined oval mass
3. FNAC or core biopsy

• Reassurance if <3 cm, young patient, confirmed benign on triple assessment
• Surgical excision if:

  • 3-4 cm

  • Growing on serial USS
  • Patient anxiety
  • Not typical on imaging
  • Age >35 years

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