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Flashcards in Ultrasonography Deck (47)
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What are ultrasound waves? 

Sound waves with frequencies higher than the human audible range (20kHz) 


How far do ultrasound waves travel in a patient? 

Only a few centimetres 


Describe the pulse echo principle 

The ultrasound/ probe transducer has two functions: 

  1. Emits a soundwave 
  2. Recieves echos from the original wave 

When ever an ultrasound passes through a tissue it can 

  • be reflected 
    • OR 
  • pass through and continue propagating 


What is the fate of ultrasound waves when they can pass through tissue? 

  • Can be reflected 
    • OR
  • Pass through and continue propagating


What affects how much of the sound wave is reflected? 


  • Dense tissue (like bone, gas) will reflect the sound waves at a high amplitude producing a white image
  • Less dense tissue (fluid, amniotic fluid, urine) will not reflect, and ultrasound waves propagate producing a black image 


List some advantages of ultrasound use? 

  • No radiation 
  • No documented side effects
  • Usually non-invasive (sometimes invasive if trans-vaginal or endo-anal) 
  • Widely accessible 
  • Results available immediately 
  • 'Real time' imaging 
  • Well tolerated 


List some disadvantages of ultrasound use? 

  • Ultrasound image is highly dependant on patient habitus (e.g weight) 
  • Effectiveness is operated dependant 
  • No known side effects 
  • Training is more resource intensive 


What are some clinical applications of ultrasounds?


  • Obstetrics (pregnancy, childbirth, postpartum period) 
  • Gynaecology 
  • Abdominal 
  • Urinary 


  • Trauma = POCUS 
  • Testicular 
  • Breast 
  • Head and Neck 
  • Vascular 
  • Cardiology 
  • Musculo-skeletal 
  • Lungs  


Describe the advantage of using an ultrasound over X-ray/CT scans in obstetric imaging 

Doesnt use ionising radiation 


Describe the 12 week scan ultrasound scan in obstetrics 




  • Foetus is approximately 45-84mm in length 
  • First routine scan offered to most low risk pregnancies 
  • Detects ‘viability’, number of foetus’, gross anatomy, detectable major abnormalities, morphology of ovaries and an accurate gestational age of foetus


Describe some pathologies picked up on a 12 week scan 

Anencephaly = Some or all foetal brain, skull and scalp is missing 

Omphalocele/ exomphalos = Herniation of abdominal tissue (part of the intestine will protude through the abdominal wall at birth) 

Body stalk defect = Extreme form of herniation, where abdominal organs will have herniated through abdomen and develop outside of the cavity 


What does a blighted ovum/ missed miscarriage on an ultrasound represent? 

  • Something may have gone wrong in the pregnancy that has prevented the foetus from growing and there is scanning of an empty sac 
  • The empty sac will have caused all the same symptoms of pregnancy + positive pregnancy test 
    • ​Hence Ultrasound (12 week scan) is the first sign that something in the pregnancy has gone wrong 


What is the probabillity of getting a miscarriage? 

High at 3 weeks 

Decreases after that, once we get to 12 weeks the probabillity is extremely low 


What is a cystic hygroma and molar pregnancy? 

  • Cystic hygroma = fluid filled cysts of resulting from blockage in the lymphatic vessels will not form properly 
  • Molar pregnancy = Non-viable fertillised egg implants in uterus and fails to come to term, foetus doesnt form properly and baby doesnt develop 


Both picked up on 12 week scan 


What genetic disease can we also screen for at 12 weeks? 

We can scan for DOWNS SYNDROME (needs a blood test + scan) 

  • Scan we carry out a foetal nuchal translucency screening 
    • Measures size of nuchal pad at the nape of the foetal neck 


What is the frequency of Down's Syndrome? 

Around 2 per 2000 births 

However increased risk in older women 

  • 1:1500 at 20 years
  • 1:800 at 30 years
  • 1:270 at 35 years
  • 1:100 at 40 years
  • 1:50 at 45 years and over


At around what time do we need to carry out the foetal nuchal translucency screening for downs syndrome? 

Between 11 weeks and 13 weeks (+ 6 days) 


After 13 weeks the lymphatic system will have developed and drained the fluid from the back of the neck 

(Reminder nuchal translucency should not be confused with nuchal fold thickness test which is carried out between 16-24 weeks) 


Describe what a nuchal translucency is? 

Appearance of the collection of fluid under the skin behind the foetal neck in the first trimester of pregnancy. 


This fluid will go on to form part of the lymphatic system 


What is another marker of Down's Syndrome at 12 weeks? 

No nasal bone 


What is the purpose of a 20 week scan? 

Helps to identify abnormalities which 

  • May indicate the baby has a life-limiting condition 
  • May benefit from antenatal treatment 
  • May require early intervention following delivery 


Other standard aims:

  • placenta localisation
  • foetal biometry
  • fibroid monitoring
  • liquor assessment


What are some abnormalties that can be picked up from a 20 week scan? 

  • Spina bifida - neural tube defect, incomplete closing of the spine and membranes around the spinal cord, gap in lumbar- sacral spine 
  • Achondroplasia - short limbed dwarfism (torso is normal length) 
  • Low lying placenta - implantation os placental over cervical opening 
  • Talipes (Club foot) - foot turns inwards 
  •  Anhydraminios (complete or near complete lack of aminiotic fluid), Oligohydramnios (not enough aminiotic fluid)/ Polyhydramnios (too much amniotic fluid) 


What is spina bifida? 

What can severe spina bifida lead to? 

  • Neural tube defect, where the baby's spine and spinal cord doesnt develop properly
  • There is incomplete closing of the spine and the membranes surrounding the spinal cord 
  • There is a gap in the lumbar sacral spine 


  • Can lead to: 
    • Paralysis 
    • Incontinence 
    • Difficult walking 
    • Other chromosomal abnormalities 


How is an ultrasound used to detect for spina bifida? 

Detected via a skull ultrasound before getting to the spine 

  • The cerebellum will be pulled down because the spinal cord is protuding through the back which will pull at the base of the brain and disrupt the shape  


How do we treat spina bifida? 

Carried out in utero to repair gaps in the babys spine so they are closed before the baby is born 


Not taking folic acid can be one of the causes of an increased risk of spina bifida 


What is achondroplasia? 

  • Genetic disorder which results in short-limbed dwarfism 
  • Torso is the same length and there is bowing of long bones 
  • Thickened soft tissue surrounding long bones 
  • On 20 week scan 
  • Frontal bossing (forehead protuding is a characteristic of achondroplasia) 


Describe the implications of a low-lying placenta

  • Implantation of the placenta over the internal os (or lower region of uterus) 
  • If placenta is within 2.5cm of cervix = more scans required 
    • If placenta is not raised then a C-section may be required 


Describe Talipes (club foot) 

  • Where the foot turns inwards 
    • Can affect one or both feet 
      • Causes 
        • Mechanical → Due to position in the womb, foot may be trapped 
        • Chromosomal abnormalities (Downs syndrome-21, Patau Syndrome-13, Edwards Syndrome-18)


What is the treatment of Talipes (club foot) 


Ponseti Method 

Ligaments, joints and tendons are stretched after gentle manipulations. A plaster cast is applied after each manipulation to retain the degree of correction and soften ligaments 


What is polyhydramnios often caused by? 

Gestational diabetes 


What is the umbilical arterial doppler assesment used for? 

Used as a marker of placental insufficiency (failure of nutrient delivery) and consequent intrauterine growth restriction (IUGR) or suspected pre-eclampsia 

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