Lobster claw sign (kidney)

Last revised by Ayla Al Kabbani on 30 Nov 2019

Lobster claw sign refers to a urographic pattern of papillary excavation that may be seen with renal papillary necrosis.

The lobster claw sign occurs when there is excavation around the edge of the papilla and the contrast material that extends into this excavated region looks like the "claws" of a lobster when viewed en face.

This patterns of papillary excavation is most often seen with 

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Cases and figures

  • Figure 1: lobster
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  • Figure 2: normal calyx
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  • Figure 2: lobster claw - papillary necrosis
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