Cobra head sign (ureter)

Last revised by Mohammadtaghi Niknejad ◉ on 7 Oct 2022

Citation, DOI, disclosures and article data

Citation:

Radswiki T, Niknejad M, Evangelou K, et al. Cobra head sign (ureter). Reference article, Radiopaedia.org (Accessed on 04 Jun 2023) https://doi.org/10.53347/rID-12602

DOI:

https://doi.org/10.53347/rID-12602

Permalink:

https://radiopaedia.org/articles/12602

rID:

12602

Article created:

22 Dec 2010, The Radswiki ◉

Disclosures:

At the time the article was created The Radswiki had no recorded disclosures.

View The Radswiki's current disclosures

Last revised:

7 Oct 2022, Mohammadtaghi Niknejad ◉

Disclosures:

At the time the article was last revised Mohammadtaghi Niknejad had no recorded disclosures.

View Mohammadtaghi Niknejad's current disclosures

Revisions:

25 times, by 19 contributors - see full revision history and disclosures

Systems:

Urogenital

Sections:

Signs

Tags:

ureter, bladder, refs

Synonyms:

Adder head sign (ureter)
Cobra-head sign
Adder's head sign
Spring onion sign (ureter)
Cobra's head sign

The cobra head sign, also known as the spring onion sign, refers to dilatation of the distal ureter, surrounded by a thin lucent line, which is seen in patients with an adult-type ureterocele. The cobra head appearance indicates an uncomplicated ureterocele.

During an excretory phase of an intravenous urography, the lucent "hood" of the cobra represents the combined thickness of the ureteral wall and prolapsed bladder mucosa, outlined by contrast material within the bladder lumen.

This lucent line should be thin and well defined. Any thickening, irregularity, or loss of definition of the cobra’s hood should raise concern for the presence of a pseudoureterocele.

Radiologic visualization can be established using radiographic urography, magnetic resonance urography, computed tomography urography or prenatal ultrasonography regarding fetal patients ³.