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Erschienen in:
17.10.2017 | Classics in Abdominal Imaging
The lambda (twin peak) sign
Erschienen in: Abdominal Radiology | Ausgabe 7/2018
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The lambda sign refers to the triangular projection of chorion between the layers of inter-twin membranes which resembles the Greek alphabet “lambda” (Fig. 1). It is best observed between 10 and 14 weeks of gestation on pelvic sonography, and its presence is highly suggestive of dichorionic diamniotic (DCDA) twin pregnancy (Fig. 2). The fused dichorionic placenta also assumes the appearance of a mountain top between the twin gestational sacs; thus the metaphorical source of its alternate title, the “twin peak” sign (Fig. 3) [1].
Fig. 1
The eleventh lower-case Greek alphabet “lambda”
Fig. 2
Transabdominal pelvic ultrasound image obtained at 16 weeks of gestation shows both foeti labeled A and B. The limbs of the lambda sign are highlighted with arrows. The ‘peak’ is labeled with an asterisk
Fig. 3
A peak [2]
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