Ob/Gyn Registry Review Study Guide Notes

Gynecology Normal Anatomy and Physiology

• Bony Boundaries of the Pelvis: The sacrum, coccyx, and innominate bones (comprising the ilium, ischium, and pubic symphysis).
• Linea Terminalis: An imaginary line extending from the pubic symphysis to the sacral prominence (the top of the sacrum).
• True Pelvis: This region is deep and located below (inferior to) the linea terminalis. It contains structures visible in transvaginal imaging, including the bladder, small bowel, ascending colon, descending colon, rectum, uterus, ovaries, fallopian tubes, internal iliac vessels, and five specific muscles.
• Musculature (True Pelvic Muscles):
  • Pelvic Diaphragm: Composed of the levator ani and coccygeus. These are hammock-shaped muscles providing support for pelvic organs. Weakening of these muscles leads to uterine prolapse. They are identified scanning transversely at the level of the vagina, posterior to the bladder, vagina, and rectum.
  • Adnexa ("O.P.I." muscles): Obturator internus (lateral to the bladder), Piriformis (posterolateral), and Iliopsoas (anterolateral). In transverse, they appear ovoid and hypoechoic; in sagittal, they elongate. They are adjacent or lateral to the bladder, ovaries, and uterus.
  • Other Muscles: Muscles like the psoas major, rectus abdominus, and oblique muscles are NOT in the true pelvis and are not adjacent to true pelvic organs.
• Uterine Ligaments:
  • Broad Ligaments: A double fold of peritoneum extending from the lateral sides of the uterus to the pelvic walls. It is only visualized sonographically in the presence of pelvic ascites.
  • Round Ligaments: Found between folds of the broad ligament, supporting the fundus of the uterus superiorly.
  • Cardinal Ligaments: Contain the vasculature of the uterus.

Pelvic Spaces and Vasculature

• Intraperitoneal Cavities (Potential Fluid Collection Spaces):
  • Retropubic Space (Space of Retzius): Located anterior to the bladder.
  • Adnexa: Located in the lower quadrants of the abdomen, lateral to the uterus. The ovaries reside here.
  • Anterior CDS (Vesicouterine Pouch): Located between the bladder and the uterus (anterior to the uterus).
  • Posterior CDS (Rectouterine Pouch / Pouch of Douglas): Located between the uterus and the rectum (posterior to the uterus).
• Arterial Supply:
  • Uterine Arteries: Branches of the internal iliac artery (also known as the hypogastric artery).
  • Arcuate Arteries: Located at the periphery of the myometrium.
  • Radial Arteries: Extend deeper into the myometrium.
  • Straight and Spiral Arteries: Feed the layers of the endometrium. Straight arteries feed the basal layer; spiral arteries feed the functional layer.
  • Ovarian Arteries (Gonadal Arteries): Originate directly from the aorta. Note: The ovaries receive dual blood supply from both the ovarian and uterine arteries.
• Venous Drainage:
  • Uterine Veins: Drain into the internal iliac veins.
  • Right Ovarian Vein: Drains into the Inferior Vena Cava (IVC).
  • Left Ovarian Vein: Drains into the left renal vein. This is the longest pelvic vessel.

Uterine Anatomy, Physiology, and Positioning

• General Characteristics: Pear-shaped, retroperitoneal organ. Located anterior to the rectum into the posterior to the bladder.
• Embryology: Developed from the fusion of paired Müllerian ducts.
• Divisions of the Uterus:
  • Fundus: The most superior and widest portion. The fallopian tubes attach at the uterine cornu.
  • Corpus: The body, representing the largest area.
  • Isthmus: The lower uterine segment, particularly noted in pregnancy.
  • Cervix: Contains the internal and external os. The external os opens into the vaginal canal (the most inferior part) and is surrounded by the vaginal fornix.
• Layers of the Uterus:
  • Serosa (Perimetrium): The outermost organ fascia.
  • Myometrium: The muscular middle layer.
  • Endometrium: The mucosal inner layer, consisting of the Basal layer (deep) and the Functional layer (superficial, shed during menses).
• Size and Shape Variations:
  • Neonatal: Prominent due to maternal hormones; cervix-to-body ratio is $2:1$.
  • Prepubertal: Tubular shape where body equals cervix.
  • Puberty: Increase in fundal diameter leads to a pear shape.
  • Reproductive years: Length of $6-8\,cm$.
  • Menopause: Decreased size of $4-6\,cm$.
• Orientation:
  • Anteversion: Body tilts forward, forming a $90^{\circ}$ angle with the cervix.
  • Anteflexion: Body folds forward, contacting the cervix.
  • Retroflexion: Body tilts back and contacts the back of the cervix.
  • Retroversion: Body tilts back without a bend.

Fallopian Tubes and Ovaries

• Fallopian Tubes (Oviducts/Salpinges):
  • Dimensions and Features: $7-12\,cm$ long; contain cilia for transport. Not typically seen on ultrasound unless pathology or fluid is present.
  • Interstitial: Proximal segment at the uterine cornu.
  • Isthmus: The "bridge" connecting interstitial to ampulla.
  • Ampulla: Longest, most tortuous segment; most common site for fertilization and ectopic pregnancies.
  • Infundibulum: Distal, widest portion containing fimbria.
• Ovaries:
  • Characteristics: Paired, oval intraperitoneal endocrine organs. Outer cortex contains follicles (oogenesis); inner medulla contains vasculature and lymphatics.
  • Support: Ovarian ligament (lateral uterus to ovary) and suspensory ligament (lateral pelvic walls to ovaries).
  • Volume Formula: $L \times W \times H \times 0.523$.
  • Hormonal Response: Stimulated by FSH and LH to produce estrogen and progesterone.
  • Development: FSH causes follicle development. The Graafian (dominant) follicle contains the ovum within the cumulus oophorus (seen as a daughter cyst). Ovulation occurs within $36\,hours$ of dominant follicle maturity. LH ruptures the follicle, which becomes the corpus luteum (releasing progesterone), and eventually the corpus albicans.

The Normal Menstrual Cycle

• Overview: Regulated by the hypothalamus (GnRH) and anterior pituitary (FSH/LH).
• Ovarian Phases:
  • Follicular Phase (Days 1-14): FSH stimulates follicles. Dominant follicle grows to $2.5-2.7\,cm$. Follicles produce estrogen, thickening the endometrium.
  • Ovulation (Day 14): LH surge causes rupture. Occurs exactly $14\,days$ before the next menses. Calculation: $\text{Total Cycle Days} - 14 = \text{Ovulation Day}$.
  • Luteal Phase (Days 15-28): Follicle becomes corpus luteum, producing progesterone to maintain the endometrium.
• Endometrial Phases:
  • Menstrual Phase (Days 1-5): Shedding of the functional layer.
  • Proliferative Phase (Days 6-14): Estrogen thickens the lining.
    • Early Proliferative: Thin, echogenic, $\le 4\,mm$.
    • Late Proliferative (Periovulatory): $6-10\,mm$; "three-line sign" appearance (echogenic basal layer, hypoechoic functional layer).
  • Secretory Phase (Days 15-28): Progesterone-driven; thick and echogenic lining, $7-16\,mm$.
• Relationships: Follicular matches Proliferative; Ovulation matches Late Proliferative; Luteal matches Secretory.

Clinical History and Imaging Techniques

• Gravida (G): Number of pregnancies. Para (P): Number of pregnancies carried to term.
• Transabdominal (TA) Ultrasound:
  • Frequency: $2-6\,MHz$.
  • Prep: $32\,oz$ water (full bladder). Global view, better for large pathology.
• Transvaginal (TV) Ultrasound:
  • Frequency: $6-9\,MHz$.
  • Prep: Empty bladder. Better resolution, limited field of view. Contraindicated in pediatrics or patients unable to tolerate.
• Clinical Terms:
  • Mittelschmerz: Pain near ovulation mid-cycle.
  • Primary Amenorrhea: Never reached menarche by age $16$.
  • Secondary Amenorrhea: Menses stopped.
• Measurement Protocols:
  • Uterus: Measured in sagittal (length, AP) and transverse (width).
  • Endometrium: Measured in sagittal AP dimension at greatest thickness; exclude fluid. If fluid is present, measure layers separately and add together.

Congenital Malformations

• Etiology: Abnormal fusion of Müllerian ducts. Always check kidneys for associated anomalies.
• DES (Diethylstilbestrol) Exposure: Associated with a T-shaped uterus.
• Malformations:
  • Arcuate: Mildest; slight fundal indentation.
  • Bicornuate (Bicornis Unicollis): One cavity dividing into two at the fundus ("Y" shaped).
  • Septate: Most common anomaly; two separate cavities with a flat fundal contour.
  • Subseptate: Normal contour with partial separation.
  • Didelphys: Complete lack of fusion (2 vaginas, 2 cervices, 2 uteri).
  • Unicornuate: One duct fails to form (single horn).
• Vaginal Malformations:
  • Imperforate Hymen: Most common cause of obstruction. Leads to hematometracolpos (fluid in vagina and uterus).
  • Vaginal Atresia: Closed vagina; fluid accumulates only in uterus and cervix (hematometra).

Uterine and Endometrial Pathology

• Adenomyosis: Invasion of endometrial tissue into the myometrium. Presents with dysmenorrhea and menometrorrhagia. Sono: Heterogeneous myometrium, posterior thickening, and "linear striations."
• Leiomyoma (Fibroid): Benign smooth muscle tumor; estrogen-stimulated.
  • Intramural: Most common; within the wall.
  • Submucosal: Distorts endometrium; causes bleeding issues.
  • Subserosal: Distorts outer contour.
  • Pedunculated: Attaches by a stalk; may mimic adnexal mass.
• Leiomyosarcoma: Malignant form of fibroid; rapid growth in perimenopausal women.
• Endometrial Hyperplasia: Result of unopposed estrogen. Thickened lining. Limits: Asymptomatic post-menopausal $\le 8\,mm$; Symptomatic $\le 5\,mm$.
• Endometrial Polyps: Hyperplastic nodules; best seen on Saline Infused Sonohysterography (SIS).
• Endometrial Carcinoma: Most common GYN malignancy. Linked to obesity and HRT.
• Endometrial Atrophy: Thinning ($\le 4\,mm$) in post-menopausal patients; most common cause of post-menopausal bleeding.
• Asherman Syndrome: Adhesions/synechiae due to surgical scarring; appears stringy on SIS.
• Miscellaneous: Nabothian cysts (cervical retention cysts), Gartner Duct cysts (vaginal wall), IUDs (echogenic with shadowing/reverberation).

Ovarian and Adnexal Pathology

• Polycystic Ovarian Disease (PCOD): Chronic anovulation, "string of pearls" appearance. Most common cause of infertility.
• Endometriosis: Ectopic functional endometrial tissue. Endometriomas ("chocolate cysts") are complex with low-level echoes and enhancement.
• Ovarian Cysts:
  • Follicular: Common, simple, $\gt 3\,cm$.
  • Corpus Luteum: Common in pregnancy; hemorrhagic/lacy.
  • Theca Lutein: Bilateral, multiloculated "grape clusters," associated with $\text{hCG} \gt 100,000$ and molar pregnancy.
• Benign Tumors:
  • Cystic Teratoma (Dermoid): Most common benign tumor. Features: "tip of the iceberg" (shadowing), dermoid plug, and mesh (hair).
  • Fibroma: Solid, hypoechoic, associated with Meigs Syndrome (ascites + pleural effusion).
  • Brenner Tumor: Small, solid, calcified; does not produce estrogen.
  • Thecoma/Granulosa Cell: Estrogen-producing sex-cord stromal tumors. Granulosa is the most common estrogenic tumor, can cause precocious puberty.
• Malignant Tumors:
  • Serous Cystadenocarcinoma: Most common ovarian malignancy. Large cystic mass with mural nodules.
  • Mucinous Cystadenocarcinoma: Associated with pseudomyxoma peritonei.
  • Krukenberg Tumor: Metastatic from GI tract (stomach); bilateral masses.
  • Dysgerminoma: Malignant germ cell tumor in young patients ($\lt 30$); elevated hCG and serum lactate dehydrogenase.
  • Yolk Sac Tumor: Rapid growth, elevated AFP in non-gravid females.
• Ovarian Torsion: Twisted blood supply; enlarged, heterogeneous, diminished flow. Use high sensitivity Doppler settings.

Pelvic Inflammatory Disease (PID)

• Etiology: Starts as vaginitis, often caused by STDs (chlamydia, gonorrhea).
• Stages:
  • Stage 1: Early acute; endometritis (thick/heterogeneous lining, comet tail artifacts).
  • Stage 2: Spread to tubes (salpingitis, pyosalpinx, hydrosalpinx).
  • Stage 3: Severe; Tubo-Ovarian Abscess (TOA). Loss of discrete borders.
• Differences:
  • Acute: Active infection, fever, leukocytosis, endometritis, pyosalpinx.
  • Chronic: Damage-related, hydrosalpinx, adhesions (echogenic bands), TOA.

Normal First Trimester Obstetrics

• Chronology: Fertilization in ampulla ($Day 14$) $\rightarrow$ Zygote $\rightarrow$ Morula ($Days 3-4$) $\rightarrow$ Blastocyst ($Day 5$) $\rightarrow$ Implantation ($Days 7-9$).
• Blastocyst Components: Trophoblast (produces hCG, becomes placenta) and Embryoblast (becomes embryo, amnion, cord, yolk sac).
• Gestational Sac (GS): Visible TV by $1000-2000\,mIU/mL$ hCG. Double decidual sign confirms IUP and rules out pseudogestational sac. Grows $1\,mm/day$.
• Yolk Sac (YS): First definitive sign of IUP. Should be seen when MSD is $10\,mm$. Should measure $\lt 6\,mm$. Functions: AFP production, hematopoiesis.
• Fetal Pole: Must be seen when MSD is $25\,mm$. CRL (Crown Rump Length) is the most accurate for age: $\text{CRL (cm)} + 6.5 = \text{GA (weeks)}$. Heartbeat must be seen if CRL is $5\,mm$.
• Rhombencephalon: Cystic structure in head at $8\,weeks$.
• Physiologic Bowel Herniation: Normal between $9-12\,weeks$; must resolve by $12\,weeks$.
• 1st Trimester Screening ($11-13w 6d$): Nuchal Translucency (NT) $\le 3\,mm$. Combined with hCG and PAPP-A.

Abnormal First Trimester

• Ectopic Pregnancy: Most common in ampulla; most dangerous in interstitium/cornu. Classic triad: pain, bleeding, palpable mass. Suspect if hCG is above threshold with no seen IUP.
• Gestational Trophoblastic Disease (GTD): Molar pregnancy involving excessive trophoblast proliferation and extremely high hCG.
  • Complete Mole: "Vesicular snowstorm," no fetus, bilateral theca lutein cysts.
  • Partial Mole: Coexisting fetus/GS.
  • Invasive Mole / Choriocarcinoma: Malignant, may metastasize to lungs.
• Miscarriages (Spontaneous Abortions):
  • Threatened: Spotting with closed cervix.
  • Incomplete: Still in process; Retained Products of Conception (RPOC) visible.
  • Missed: Intact GS with embryonic demise (CRL $5\,mm$ with no FHR).
  • Anembryonic (Blighted Ovum): GS $\gt 25\,mm$ with no pole.
• Subchorionic Hemorrhage: Crescent-shaped bleed between endometrium and GS. Worrisome if $\gt 50\%$ of GS size.

2nd Trimester Anatomy and Pathology

• Screening ($15-20\,weeks$): Quadruple screen (hCG, AFP, estriol, inhibin-A). Elevated AFP suggests open defects.
• Fetal Lie: Cephalic/Vertex (head down), Breech (feet/buttocks down), Transverse. Determine using spine-to-stomach orientation.
• Cardiac Anatomy:
  • Normal: $45^{\circ}$ apex to left. Rate $120-180\,BPM$.
  • Shunts: Ductus venosus (umbilical vein to IVC), Foramen ovale (RA to LA), Ductus arteriosus (MPA to Aorta).
• Cardiac Pathology:
  • Hypoplastic Left Heart: Small LV; associated with T13.
  • VSD: Most common cardiac defect; associated with T21.
  • Ebstein Anomaly: Apically displaced tricuspid valve.
  • Rhabdomyoma: Cardiac tumor associated with tuberous sclerosis.
• Chest/Lung Pathology:
  • Diaphragmatic Hernia: Most common is Bochdalek (left side). Stomach appears in chest.
  • CCAM: Type 1 (Macrocystic), Type 3 (Microcystic/Echogenic).
  • Pulmonary Sequestration: Nonfunctioning lung tissue with its own blood supply from the aorta.

Brain and Neural Tube Defects

• Landmarks for HC/BPD: Cavum Septum Pellucidum (CSP), Thalami, Falx. Avoid orbits/cerebellum.
• Brain Pathology:
  • Ventriculomegaly: LV atrium $\gt 10\,mm$. "Dangling choroid" sign.
  • Aqueductal Stenosis: Dilated 3rd and Lateral ventricles.
  • Hydranencephaly: Brain replaced by fluid; no cerebral rim.
  • Holoprosencephaly: Failure of midline split; associated with T13. Alobar (horshoe monoventricle) is most severe.
  • Dandy-Walker Malformation: Splayed cerebellum, "key-hole" 4th ventricle, CM $\gt 10\,mm$.
• Neural Tube Defects (NTD):
  • Acrania/Anencephaly: Absence of skull/brain. High AFP. "Frog-like" orbits.
  • Spina Bifida: Splaying of laminae. Aperta (open) is associated with Arnold-Chiari II Malformation (lemon head, banana cerebellum, obliterated CM).
  • Cephalocele: Brain herniation from skull. Occipital is most common.

Face, Neck, and Skeletal Systems

• Markers of Trisomy 21 (Down Syndrome): Flattened profile, nuchal fold $\ge 6\,mm$, macroglossia, sandal gap feet, absent nasal bone.
• Cystic Hygroma: Accumulation of lymphatic fluid; associated with Turner Syndrome.
• Skeletal Dysplasias:
  • Thanatophoric Dysplasia: Most common lethal dysplasia. "Cloverleaf skull" and "telephone receiver" femurs.
  • Achondroplasia: Most common non-lethal (dwarfism). Findings include rhizomelia and trident hand.
  • Osteogenesis Imperfecta: Brittle bones, multiple fractures, "soft skull."
  • Caudal Regression Syndrome: Sacral agenesis; associated with maternal diabetes.
• Appendicular Defects: Clubfoot (Talipes equinovarus) - associated with T13; Rockerbottom feet - associated with T18.

Gastrointestinal and Genitourinary Systems

• GI Obstructions: Result in Polyhydramnios ($\text{AFI} \gt 24\,cm$, $\text{DVP} \gt 8\,cm$).
  • Esophageal Atresia: No seen stomach; associated with VACTERL.
  • Duodenal Atresia: "Double-bubble sign"; associated with T21.
  • Gastroschisis: Right-sided cord herniation of bowel; not covered by membrane.
  • Omphalocele: Midline cord herniation covered by membrane; associated with T18/T13.
• GU Pathology: Most frequent cause of Oligohydramnios ($\text{AFI} \lt 5\,cm$, $\text{DVP} \lt 2\,cm$).
  • Renal Agenesis: Bilateral leads to Potter Syndrome (No fluid, No bladder). Features "lying down adrenal."
  • Infantile PKD (ARPKD): Bilateral, enlarged echogenic kidneys. Fatal.
  • UPJ Obstruction: Most common cause of hydronephrosis; pyelectasis only.
  • Posterior Urethral Valves (Bladder Outlet Obstruction): "Key-hole" bladder; male fetuses.

Multiple Gestations and Placenta

• Twinning:
  • Dizygotic (Dichorionic/Diamniotic): 2 eggs, 2 placentas, 2 sacs. "Twin peak/lambda" sign.
  • Monozygotic (Identical): Splits from 1 egg.
    • $0-4\,days$: Di/Di.
    • $4-8\,days$: Monochorionic/Diamniotic ("T" sign).
    • $\gt 8\,days$: Mono/Mono (Everything shared).
• Complications: Twin-to-Twin Transfusion Syndrome (TTTS) - Donor (IUGR/Oligo) vs Recipient (Hydrops/Poly). TRAP sequence (Acardiac twin).
• Placenta:
  • Variants: Succenturiate lobe (extra small lobe), Circumvallate (curled edges).
  • Previas: Complete (covers internal os), low-lying (within $2\,cm$ of os).
  • Accreta: Abnormal adherence to myometrium.
  • Abruption: Premature separation; retroplacental hematoma.

Obstetrics Dopplers and Maternal Conditions

• Umbilical Artery: Measures placental resistance. High resistance (S/D ratio $\gt 3.0$) indicates hypoxia/IUGR.
• MCA (Middle Cerebral Artery): Low resistance indicates "brain-sparing" shunting due to hypoxia.
• Ductus Venosus: a-wave flow reversal indicates high fetal resistance (CHF/Hydrops).
• Maternal Complications:
  • TORCH: Group of infections (Toxoplasmosis, Rubella, CMV, Herpes).
  • Preeclampsia: Hypertension and proteinuria. Leads to placental insufficiency.
  • HELLP: Hemolysis, Elevated Liver enzymes, Low Platelets.
  • Incompetent Cervix: Painless dilation; treated with cerclage.

Physics and Doppler Principles

• ALARA: As Low As Reasonably Achievable. Thermal Index (TI) and Mechanical Index (MI) should be monitored.
• Doppler Optimization:
  • PRF/Scale: Match to flow ($\text{High scale} = \text{Arteries}$, $\text{Low scale} = \text{Ovarian flow}$).
  • Wall Filter: Removes low frequency noise.
  • Power Doppler: Sensitive to presence of flow but lacks directional data.