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Radiology
Ambiguous Genitalia
Built from Obstetric Imaging
What’s inside
12 sections · 88 slides
Overview
- What this deck covers
What the term means
A morphologic label sitting inside a much larger family of conditions
- Why fetal sex comes up at all
- Two more medical reasons
- What ambiguous genitalia means
- What DSD means
- What sits under the DSD umbrella
- Words that are no longer used
- A look, not a diagnosis
- How the classes are grouped
- Disorders of Sexual Development
- Reading that table in one line each
- 1:4500
- Where those numbers come from
How genitals normally form
One starting body plan, one hormone, and a narrow window of time
- Everyone starts the same
- The timetable of genital development
- The gonad that could go either way
- Which way the gonad turns
- Cloaca dividing into urogenital sinus and rectum
- Why that picture matters here
- The hormone that builds male genitals
- Two ways the build goes wrong
- When DHT fails to act
- Timing decides how virilization looks
- Where the extra androgen comes from
Congenital adrenal hyperplasia
The commonest cause — an enzyme block that diverts hormone traffic
- What CAH is
- The gene and the enzyme
- The steroid hormone assembly line
- Where 21-hydroxylase sits on that line
- How the block masculinizes a female fetus
- What happens to boys with CAH
- The second half of the block
- Why salt wasting is the emergency
- Classic and nonclassic forms
The other causes
Chromosome problems and named syndromes that produce the same appearance
- What else produces this appearance
- Reading that list
How it comes to attention
Usually after birth — but screening tests are changing that
- When the diagnosis is usually made
- Cell-free fetal DNA screening
- A published example of the mismatch
- Why the DNA screen can still be wrong
- How amniotic fluid is sampled
- The two invasive tests
Ultrasound
Know the normal appearances first, then the mixed ones
- The normal female appearance
- The uterus is an unreliable sign
- The normal male appearance
- Measuring instead of eyeballing
- What ambiguous looks like on the scan
- Ambiguous genitalia in a triplet pregnancy
- What to notice in that image
- A second view of the same fetus
- Do not scan for sex too early
- Adding the third dimension
- Surface rendering of ambiguous genitalia
- Ambiguous genitalia on three-dimensional ultrasound
- What the rendered images add
- Confirming CAH before birth
MRI and the other modalities
A thin evidence base, but a real strength for internal structures
- What the MRI evidence actually is
- Two cases where MRI helped
- Where MRI genuinely helps
What else it could be
The look-alikes that must be excluded before the label is applied
- Hypospadias versus clitoromegaly
- Recognising bladder exstrophy
- The rest of the differential list
Treatment
Almost nothing before birth, and a careful team afterwards
- Before birth: nothing to treat
- What prenatal dexamethasone is for
- The timing problem
- 1:4
- Reading those odds
- Who the target population is
- What the treatment does not do
- How good is the evidence
- After birth: the team
- The one thing that cannot wait
Sex assignment and the family
The part of this topic that imaging cannot answer
- How sex assignment is decided
- Culture is part of the decision
- The harm of the examination itself
- What gender dysphoria means
- How the thinking has changed
- What the outcome literature shows
- What families need long term
Take it away
The five key points the authors themselves ask you to keep
- Key points
- Key points continued
- A practical checklist
- References
- References (continued)
- References (continued)
- References (continued)
- Suggested readings
- Suggested readings (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition