obstetric ultrasound scanning technique
DESCRIPTION
Obstetric Ultrasound Scanning Technique. Harry Gee (teaching materials provided by David Cole, Lecturer at City University, Birmingham). 2 nd & 3 rd Trimester Scans. Identify fetus Orientation Fetal heart beat Placental site Biometry Bi-Parietal Diameter (BPD) - PowerPoint PPT PresentationTRANSCRIPT
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Obstetric Ultrasound Scanning Technique
Harry Gee (teaching materials provided
by David Cole, Lecturer at City University, Birmingham)
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2nd & 3rd Trimester Scans• Identify fetus
– Orientation– Fetal heart beat
• Placental site• Biometry
– Bi-Parietal Diameter (BPD)– Head Circumference (HC) – Abdominal Circumference (AC), – Femur length (FL)
• Liquor Estimation
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2nd & 3rd Trimester Scans
• Place probe longitudinal on lower abdomen superior to symphysis pubis
• Slide probe superiorly using sweeping movements to locate fetus
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2nd & 3rd Trimester Scans
• Slide probe superiorly - sweeping side to side up to uterine fundus.
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FH + Orientation
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Fetal Orientation
• Lie– longitudinal – Transverse– Oblique
• Presentation– cephalic– breech
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Cephalic
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Breech
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Breech legs extended
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Transverse lie
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Placental localisation
• Full bladder• Midline sagittal section• Placental position anterior or posterior• Low placenta - measure distance
between lower edge and internal os *
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Fundal placenta
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Major placenta praevia
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Minor placenta praevia
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Liquor volume
• Subjective assessment• Maximum deepest pool (MPD)• Amniotic fluid index
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Subjective Assessment
Normal liquor volume
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Maximum deepest pool
Deepest pool in cmDo not include cord or fetal limbs
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Amniotic Fluid Index
Sum of the deepest pools in each of four quadrants
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Oligohydramnios
MPD < 3 cm up to 36 weeksMPD < 2 cm 36 weeks - term
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Polyhydramnios
MPD > 8 cm
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Fetal Biometry
• Biparietal diameter BPD• Head circumference HC• Abdominal circumference AC• Femur length FL
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BPD Measurement
ROCK
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Biparietal diameter BPD
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BPD Errors
• Few (best inter-observer error)• Oblique section (increases
measurement)• Not at BPD (decreases measurement)
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Head CircumferenceTrans-ventricular Planechoroid plexus
posterior horn
falx cerebri
CSP
anterior horn
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Trans-ventricular Plane
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Measurement CriteriaBPD & HC
•Landmarks: CSP, Falx, thalami
•Alignment: symmetrical –midline no orbits, no cerebellum
•Calipers: BPD widest distance 90o midline.
•HC bony perimeter of skull
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Abdominal Circumference
• Long Axis of fetus (Spine)• Fetal trunk parallel to transducer• Rotate transducer at right angles• Move up and down until
landmarks identified.• Repeat to consistency
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Abdominal Circumference
UV
stomach
spine
Ao
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Abdominal Circumference
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AC Sources of Error
• Oblique Section (Salami Effect)• Too high • Too low• Abdominal compression (oligo-
hydramnios)• Fetal Breathing
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FL Measurement
• Identify femur close to fetal bladder/pelvis.
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FL Measurement• Slide probe so that femur is central
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FL Measurement
• Rotate probe to obtain full length image of femur.
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Femur Length
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Source of Error
• Oblique image (shortens measurement)
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