The cobra head sign (or 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 ureterocoele.
The lucent hood 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 pseudoureterocoele.
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Adder head sign||✓|
|spring onion sign||✓|
|Cobra's head sign||✗|