Fishhook ureter | Radiology Signs

Answer:

The fishhook ureter, also called the J-shaped or hockey-stick ureter, is a smooth upward-then-downward curve of the distal ureter as it approaches the bladder, so that its terminal segment resembles a fish hook. It is an indirect sign of bladder outlet obstruction, most often from benign prostatic hyperplasia with median lobe enlargement, and is demonstrated on intravenous urography and on the excretory phase of CT urography. The enlarged prostate elevates the bladder base and trigone, lifting the intramural ureteric orifices with it, so the distal ureters must first ascend and then hook downwards to reach them. It is typically bilateral and symmetrical, and reverses after relief of the obstruction. It should be assessed alongside the direct signs of outlet obstruction: bladder wall thickening and trabeculation, diverticula, a raised post-void residual volume, and intravesical prostatic protrusion. Unilateral distal ureteric hooking should raise concern for a bladder or pelvic mass instead.

Why is it called so?

The terminal ureter curves up and then down like the shank and barb of a fish hook.

Pathophysiology

The ureters pierce the bladder wall obliquely at the trigone. When the prostate, particularly a median lobe, enlarges into the bladder base, it lifts the trigone and with it the intramural ureteric segments. The more proximal ureter remains tethered in its normal retroperitoneal course, so the intervening distal segment is drawn upward and must then turn sharply downward to enter the elevated orifice, describing the hook. Chronic outlet obstruction with raised intravesical pressure adds detrusor hypertrophy and, in advanced cases, vesicoureteric reflux and upper tract dilatation.

Alternative names: J-shaped ureter, hockey-stick ureter, hooked ureter

Other associated named signs: Intravesical prostatic protrusion, bladder trabeculation and diverticula, and the pine tree bladder of neurogenic dysfunction

References

1. Mamoulakis C, Herrmann TR, Höfner K, Oelke M. The fish-hook configuration of the distal ureter indicates bladder outlet obstruction due to benign prostatic hyperplasia. World J Urol. 2011;29(2):199-204. PMID: 21079967.