A persistent or increasingly dense nephrogram on imaging can indicate several potential issues: 1) Acute urinary tract obstruction, as shown by a prolonged nephrogram and no calyceal filling, often due to a kidney stone blocking the ureter. 2) Acute bacterial nephritis, seen as a persistent dense nephrogram with minimal collecting system opacification. 3) Acute renal failure, seen on an excretory urogram as bilateral persistent nephrograms with no calyceal filling 20 minutes after contrast injection. 4) Acute renal vein thrombosis, appearing as a dense nephrogram and absence of calyceal filling 5 minutes

1. 13Persistent or Increasingly
Dense Nephrogram

2. CLINICAL IMAGAGING
AN ATLAS OF DIFFERENTIAL DAIGNOSIS
EISENBERG
DR. Muhammad Bin Zulfiqar
PGR-FCPS III SIMS/SHL

3. • Fig GU 13-1 Acute urinary tract obstruction. (A)
Excretory urogram demonstrates a prolonged
nephrogram on the left with fine cortical striations
(alternating radiolucent and radiopaque lines) and no
calyceal filling. An arrow points to the obstructing
stone in the proximal left ureter. (B) In another patient,
there is a prolonged and intensified obstructive
nephrogram of the right kidney. On the left, there is
marked dilatation of the pelvocalyceal system but no
persistent nephrogram, reflecting an intermittent
chronic obstruction on this side.

4. Fig GU 13-2 Acute bacterial nephritis. Persistent dense
nephrogram on the left with minimal opacification of the
collecting system.

5. • Fig GU 13-3 Acute renal failure. Film from an
excretory urogram 20 minutes after the
injection of contrast material shows bilateral
persistent nephrograms with no calyceal
filling.

6. • Fig GU 13-4 Acute renal vein thrombosis. Film
of the right kidney taken 5 minutes after the
injection of contrast material shows a dense
nephrogram (arrows) and the absence of
calyceal filling.