Obstructing stone?

CTEAU Urolithiasis 2026

Acute flank pain on an unenhanced CT; urology wants to know whether this stone passes on its own — and whether the kidney is infected.

Answer the surgeon

Urologic intervention (stent or nephrostomy) vs medical expulsive therapy — and the infected obstructed kidney, which needs decompression tonight.

Your answer must state:

Stone size in mm (axial and coronal) and location: UPJ / proximal / distal ureter / UVJ
Hydronephrosis and its grade
Possible infection signs — urothelial thickening, disproportionate stranding, gas; a striated nephrogram requires contrast. Imaging cannot exclude infection, so correlate urgently with fever, urinalysis, cultures, and inflammatory markers
Forniceal rupture (perinephric urinoma)
Solitary kidney or bilateral obstruction

Key and direct findings

1.Ureteric calculus with proximal hydroureteronephrosis
The stone plus upstream dilatation makes the diagnosis; measure it in two planes and name the ureteric segment.

Supportive signs & checks

1.Secondary obstructive signs
Perinephric and periureteric stranding, nephromegaly, and a delayed or persistent nephrogram support acute obstruction.
2.Soft-tissue rim sign
A rim of edematous ureteric wall around the calcification favors stone; a comet-tail of vessel favors phlebolith.
Pitfall: Pelvic phleboliths sit exactly where distal ureteric stones do — trace the ureter down to decide.
3.Size and location inform passage
Stones <5 mm often pass spontaneously, especially distally, whereas stones >10 mm are much less likely to pass; patient factors, anatomy, symptoms, and complications also guide treatment.
4.Recently passed stone
Residual hydronephrosis and stranding with no stone and a normal-caliber distal ureter — check the bladder for the passed stone and say so.
5.Pyonephrosis can look bland
An infected obstructed system may show only hydronephrosis on CT — layering debris, urothelial thickening, or gas are late clues; flag infection on clinical grounds.
Pitfall: Missing the infected obstruction is the on-call disaster here — it loses kidneys and lives, not the stone itself.

Wet-read snippets

Fill the blanks, then copy into your preliminary report.

Positive

___ mm obstructing calculus at the ___ with ___ hydronephrosis and perinephric stranding. Imaging cannot exclude superimposed infection; correlate urgently with clinical findings, urinalysis, cultures, and inflammatory markers.

Negative

No ureteric calculus or hydronephrosis — no CT evidence of urolithiasis; consider alternative causes of flank pain.

Sources

EAU guidelines on urolithiasis — European Association of Urology (2026)
Imaging in suspected renal colic: multispecialty consensus — Moore CL et al. J Urol (2019)

Content review: Content pending clinical review · 2026-07-15

Educational reference for trained clinicians. Verify every result against the cited original guideline before use. Not a substitute for clinical judgment or medical advice.