1. KEY POINTS TO DIFFERENTIATE RENAL PSEUDOTUMORS
1 .- To Know renal anatomy and US correlation
2 .- To study typical US findings in common pseudotumors

2. 1.- To know renal anatomy and US correlation
- Cortex
- Medulla: pyramids (hipoechoic)
Renal sinus: Made up of different structures (hyperechogenic)
Fig 1. Renal anatomy and ultrasonography correlation. This image allows to differentiate the cortical ( ), the medullar ( ) and the renal sinus ( )
To know the anatomy and US correlation is the first step in order to distinguish these pseudolesions

3. 2.- Typical US findings in common pseudotumors
Hyperechogenic pseudotumors:
Focal cortical scar
Renal cortical defect
Fatty tissue from the renal sinus
Iso and hypoechoic pseudotumors:
Lobar dysmorphism
Dromedary hump
Cortical scar
Duplication artifact
Prominent columns of
Bertin
Sinus lipomatosis
CORTICAL
MEDU
LAR

4. Focal cortical scar Hyperechogenic pseudotumors
An optical effect: Perirrenal fat looks like an hyperechogenic lesion
Fig 2.- Focal renal scar in a sagital ultrasound projection. The pseudotumor is in a smooth transition with the renal capsule.
The pseudotumor does NOT cause mass effect.
Fig 3.- Renal exophytic angiomyolipoma. Focal cortical scar sometimes is confused with angiomyolipoma.
To distinguish this lesion from a renal scar we may pay attention in the mass effect.

5. Hyperechogenic pseudotumors
Focal cortical scar
Key points for the differential diagnosis:
1 .- Smooth transition with the capsule
2 .- Continue with the perirrenal fat
3 .- Does not cause mass effect
Fig 4.- a.- Focal renal scar. The pseudotumor has smooth transition with de renal capsule (obtuse angles ), shows continuity with the perirrenal fat and does not cause mass effect. b.- Renal angiomyolipoma. The lesion produces mass effect, and the transition with the renal capsule is abrupt (acute angles ). Angiomyolipoma causes mass effect because it changes the morphology of the lateroconal fascia.

6. Hyperechogenic pseudotumors
Renal cortical defect
- Due to an incomplete fussion of the renal lobes
- On the site of fussion, parenchymatous defects may appear and they must NOT be confused with true renal tumors
Fig 5.- Renal cortical defect. The pseudotumor is in the typical location (between the upper and the middle poles of the kidney) and has the typical triangular shape. These two features are more evident in sagital projection.
Lower-pole
Middle-pole
Upper-pole

7. Hyperechogenic pseudotumors
Key points for the differential diagnosis:
1 .- Typicaly triangular - linear shape
2 .- Typical location: Interpolar region
3 .- Communication with the renal sinus
Renal cortical defect
LIVER
Fig 6.- Renal cortical defect. These axial ultrasound images show a renal pseudotumor with the typical triangular shape ( ). It is located in the interpolar region. In addittion, we can clearly see the continuity of the pseudotumor with the renal sinus (pink arrows). The axial projection is the best to demonstrate this continuity.

8. Fatty tissue from the renal sinus
Hyperechogenic pseudotumors
Fatty tissue from the renal sinus a.
Fig 7.- Fatty tissue from the renal sinus (blue arrows). There is an hyperechogenic lesion in the renal cortex that seems a true renal tumor.
a.- This projection does not allow to show the connection between the pseudotumor and the renal sinus.
b.- However, if the probe is angled the connection is more evident. b.
Interdigitation of renal sinus fat into the cortex

9. Fatty tissue from the renal sinus
Hyperechogenic pseudotumors
Fatty tissue from the renal sinus
Key point for the differential diagnosis:
1.- To show the connection with the renal sinus
Fig 8.- Fatty tissue from the renal sinus. This picture clearly shows the connection between the pseudotumor and the renal sinus.
Fig 9.- Renal angiomyolipoma. Hyperechogenic lesion in renal cortex without connection with the renal sinus.

10. 2.- Typical US findings in common pseudotumors
Hyperechogenic pseudotumors:
Focal cortical scar
Renal cortical defect
Fatty tissue from the renal sinus
Iso and hypoechoic pseudotumors:
Lobar dysmorphism
Dromedary hump
Cortical scar
Duplication artifact
Prominent columns of
Bertin
Sinus lipomatosis
CORTICAL
MEDU
LAR

11. Mass effect
The alteration of the two lines of the renal cortex is very important when pseudotumors are isoechoic because of the low contrast between the lesion and the adjacent tissue.
A real renal tumor produces an alteration of the two renal cortical lines.
Outer cortex
Inner cortex
Fig 10.- Renal tumor. Both cortical lines (outer and inner cortex) are disrupted. Therefore, the lesion is producing mass effect and it suggests it is a true renal tumor.

12. Mass effect
Pseudotumors may mimic true renal tumors producing mass effect, but they disturb only one of the renal cortical margins.
a.-
b.-
c.-
d.-
Fig 11.- Renal pseudotumors. There is only one renal cortical line affected.
a.- Fetal renal lobulation
b.- Dromedary hump
c.- Cortical scarring
d.- Hypertrophy of Bertin column

13. TUMOR PSEUDOTUMOR
1.- Alteration of the two lines of the renal cortex
2.- Alteration of renal echostructure
3.- Vascular displacement
1.- No alteration of the two renal cortical lines
2.- No alteration of renal echostructure
3.- No vascular displacement
Fig 12.- Renal tumor. Both renal cortical lines are affected.
Fig 13.- Renal pseudotumor. There is only one renal cortical line affected.

14. Lobar dysmorphism Iso and hypoechoic pseudotumors
Key point:
The alteration of the contour center is a pyramid
There is a notch in the renal cortical parenchyma without loss it
Fig 14.- Lobar dysmorphism (yellow arrows).
Fig 15.- Lobar dysmorphism. There is an alteration of the outer cortical line and the alteration of the contour center is a renal pyramid (yellow arrows).
There is:
1.- No alteration of the two renal cortical lines
2.- No alteration of renal echostructure
3.- No vascular displacement

15. Iso and hypoechoic pseudotumors
Dromedary hump
There is:
1.- No alteration of the two renal cortical lines
2.- No alteration of renal echostructure
3.- No vascular displacement
The alteration of renal contour is located in the left kidney immediately below the spleen. a b c
SPLEEN
Fig 16.- Dromedary hump.
a.- Alteration of the renal contour that can simulate a renal mass.
b.- If we angle the probe can be seen only one renal cortical line affected. The inner cortical line is not affected and the renal sinus is clearly introducing into the pseudotumor.
c.- The Doppler signal shows that there is no displacement of the vessels and this finding suggests that it is not a true renal tumor.
The dromedary hump typically appears in the left kidney, just below the spleen.

16. Iso and hypoechoic pseudotumors
Key Point:
The alteration of the contour is located in the left kidney immediately below the spleen
Dromedary hump
SPLEEN
Fig 17.- Dromedary hump. Two findings suggests that this is not a true tumor:
1.- There is no alteration of the two renal cortical lines, only the outer one is affected (blue arrows). If we angled the transducer we can see how the renal sinus is introducing through the cortical (green arrows).
2.- There is no alteration of renal echostructure.

17. Cortical scar Iso and hypoechoic pseudotumors Key point:
Thinning of the cortex without involvement of the interpapilary line
Cortical scar
Fig 18.- Cortical scar. a.- A thinning of the cortex that can simulate a renal mass. There is only alteration of one of the both renal cortical lines and the renal echostructure is not affected. b.- Cortical scar. There is a cortical defect that can simulate a true renal tumor (blue arrows)
Key Data:
1.- No alteration of the two renal cortical lines
2.- No alteration of renal echostructure
3.- No vascular displacement

18. Iso and hypoechoic pseudotumors
Duplication artifact
The refraction of the ultrasound beam with the surface of the liver is disturbed, and an image duplication is created
LIVER
MASS
KIDNEY
LIVER
MASS
KIDNEY
Fig 19.- Diagram explaining the refraction of the ultrasound with the surface of the liver, giving the image the appearance of a “renal pseudomass”
Fig 20.- This image shows how the ultrasound beam strikes with the surface of the liver. It is the effect of refraction and results in the appearance of a mirror image of the right kidney, a"renal pseudomass”.

19. Iso and hypoechoic pseudotumors
LIVER
MASS
KIDNEY
Iso and hypoechoic pseudotumors
Duplication artifact
Fig Duplication artifact. It seems to be a renal mass in the upper pole of the right kidney because of the ultrasounds are reflecting in the surface of the liver. The presence of a mirror image of the right kidney and the line of separation (yellow arrows) suggest a pseudotumor producing by the duplication artifact. Changing the angulation of the transducer, the artifact disappears.

20. Prominent column of Bertin
Iso and hypoechoic pseudotumors
Prominent column of Bertin
Prolongation of the cortex towards the renal sinus. It can be confused with a tumor of the renal sinus.
Fig Prominent column of Bertin. There is a piece of the cortex protruding into the renal sinus.
Fig 23.- Prominent column of Bertin. If the probe is angled, we can see how the pseudotumor is always in connection with the cortex.

21. PROMINENT COLUMN OF BERTIN
Iso and hypoechoic pseudotumors
PROMINENT COLUMN OF BERTIN
TUMOR OF THE
RENAL SINUS
Key points:
- The lesion continue with the cortex - Isoechoic - Between two renal pyramids - In the middle-pole - Doppler: NO displacement of renal arteries
Fig Prominent columnof Bertin. It is an isoechoic pseudolesion in connection with the renal cortex.
Key points:
- NO continuity with the cortex - NOT isoechoic - NO located between two renal pyramids - In the renal sinus - Doppler: displacement of renal arteries
Fig Tumor of the renal sinus. It is a lesion located in the renal sinus, sligthly more hypoechoic than this one and shows no connection with the renal cortex.

22. PROMINENT COLUMN OF BERTIN
Iso and hypoechoic pseudotumors
PROMINENT COLUMN OF BERTIN
RENAL TUMOR
Fig 26.- Prominent column of Bertin. There is no displacement of the arteries and veins.
Fig 27.- Renal carcinoma. There is a displacement of the arteries and veins.