1. Focal renal FDG uptake
H. Adams

2. Gross anatomy
The Renal System Explained. Deshmukh. Nottingham University Press 2009
Renal column
Major calyx
Minor calyx

3. Transverse section

4. Incidental focal renal FDG uptake

5. FDG PET:
Primary detection of RCC
Ceyssens, Mortelmans. Positron Emission Tomography in Renal Cancer. 2008, Renal Cell Cancer, Pages 131-136
N
90
53
17
10
Not highly effective for primary diagnosis. Studies with PET standalone, not PET-CT.
Difficulties with urinary excretion. Inconsistencies depending on cell differentiation.
Very high specificity!

6. Incidental focal renal FDG uptake
Differential
• Benign:
– Pyelum
– Calyceal Diverticulum
– (adrenocortical) Oncocytoma
– Infected cyst / Abcess / hematoma
– xantogranulomatous pyelonephritis
– Angiomyolipoma
• Malignant:
– (cystic) Renal Cell Carcinoma (RCC)
– transitional cell carcinoma (TCC)
– Renal lymphoma
– Metastasis
If low dose CT not sufficient, then
contrast enhanced (diagnostic) CT
Additional
strategies

7. Imaging the Solid Renal Mass in Adults
CT: strategies
Ball versus
the Bean
Visible on
Unenhanced CT
+
Enhanced CT
Not visible on
Unenhanced CT

8. Ball versus the
Bean
PET +
PET +
PET +
PET +
PET +
PET +
PET +
PET - ?
PET - ?
PET +

9. Balltype RCC on CT
Unenhanced CT + Enhanced CT
renal hump at unenhanced CT well-defined ball-type lesion
Radiology: Volume 247: Number 2—May 2008

10. RCCs in context of acquired cystic disease
Unenhanced CT + Enhanced CT
numerous masses bilaterally in atrophic
kidneys. Calcification (arrowhead) is
seen in cyst
well-defined ball-type lesion:
2-cm enhancing mass: RCC

11. RCC on CT
Enhanced CT: Improved mass conspicuity during nephrographic phase
Corticomedullary phase Nephrographic phase: RCC

12. Bean type lesion: TCC
Transitional cell carcinoma
(TCC) / urothelial cell carcinoma
• Focal intraluminal
mass in the renal
collecting system
• Alters the regional
architecture of renal
sinus and parenchyma
but preserves the renal
contour.
Unenhanced CT: obliteration of the sinus
fat in upper aspect of the right kidney

13. Bean type lesion: TCC
Enhanced nephrographic-phase:
poorly defined parenchymal mass
with no alteration of the renal contour
Obliteration of caliceal elements in
the upper pole (phantom calyces

14. Angiomyolipoma (AML) Lesions
• Ball-type renal lesion contains detectable fat at CT imaging:
nearly specific diagnosis of AML
• Fat: clustered pixels with negative CT numbers (defined as at
least 3 adjacent pixels with attenuation -20 HU or less)
1.3-cm lesion (arrow)
Primarily fat (attenuation -66 HU)
No further workup necessary

15. Angiomyolipoma (AML) Lesions
Indeterminate mass: pixel mapping; internal attenuation 16 HU.
Clusters of pixels < < -20 : Angiomyolipoma, but Follow up required.

16. Multiple AMLs
Pt with Tuberous sclerosis:
Near-total replacement of the right kidney by multiple fat-containing AMLs
Left kidney (K) also harbors numerous smaller but similar-appearing masses

17. Ball type: Oncocytoma
• RCC and oncocytoma can be indistinguishable, especially when the tumor
is small
• May be quite large (up to 25 cm)
• central stellate scar
• Most commonly excised benign
Solid renal mass!
Stellate central scar (arrow). Presence of
pseudocapsule at posterior margin of the mass.

18. Renal metastases
• Fifth most common site of hematogenous
metastases (4x more than RCCs)
• Lung, breast, gastrointestinal tumors and
melanoma are the most common
• Often as a part of widespread disease.
• Metastatic lesions are typically:
– small, multifocal, and bilateral,
– exhibiting an infiltrative growth pattern.
– The contrast enhancement is much less than that
of normal renal parenchyma

19. Renal metastases
Two poorly defined
bean-type lesions:
squamous cell lung
carcinoma
Extensive hepatic
metastatic disease
and abnormal
retroperitoneal
lymphadenopathy

20. Renal lymphoma
large B-cell type non-Hodgkin lymphoma
Multiple masses, incl. right kidney
Non-Hodgkin lymphoma:
- bilateral Bean type lesions
- Splenic lesions (arrow)

21. Focal renal FDG uptake
Differential
• Benign:
– Pyelum  low dose or CT
–  Calyceal Diverticulum  low dose or CT
– (adrenocortical) Oncocytoma  CT or biopsy
– Infected cyst / Abcess / hematoma
– xantogranulomatous pyelonephritis
–  Angiomyolipoma  low dose or CT
• Malignant:
– (cystic) Renal Cell Carcinoma (RCC)  CT or biopsy
–  transitional cell carcinoma (TCC)  CT or biopsy
–  Renal lymphoma  CT in case clinically relevant
–  Metastasis  CT in case clinically relevant

22. Renal hematoma
Unenhanced CT: heterogeneously
hyperattenuating (46 HU) renal mass
(arrows) with calcifications
Enhanced CT scan during nephrographic
Phase: no enhancement of the mass
Silverman et al. Hyperattenuating Renal Masses: Etiologies, Pathogenesis, and Imaging Evaluation. RG 2007

23. Benign Hyperattenuating Cysts
Benign cysts are overwhelmingly the most common type of
hyperattenuating renal mass. (Bosniak class.)
Unenhanced CT:
Hyperattenuating (80 HU) renal mass
Contrast-enhanced CT:
No enhancement of the mass.

24. Other types of
hyperattenuating renal masses
• Renal cell carcinoma
• Angiomyolipoma with minimal fat
• Multilocular cystic renal cell carcinoma
RCC: enhancement of the mass

26. hyperattenuating renal masses
• If PET positive:
– CT, MRI and eventually biopsy can be needed
– Ultrasound not modality of choice
Multilocular cystic renal cell carcinoma: enhancing septa

27. Focal renal FDG uptake
Differential
• Benign:
– Pyelum  low dose or CT
–  Calyceal Diverticulum  low dose or CT
– (adrenocortical) Oncocytoma  CT or biopsy
–  Infected cyst / Abcess / hematoma  low dose (if hyperattenuating: CT, MRI or
biopsy)
– xantogranulomatous pyelonephritis
–  Angiomyolipoma  low dose or CT (if hyperattenuating: MRI)
• Malignant:
– (cystic) Renal Cell Carcinoma (RCC)  CT or biopsy (if hyperattenuating: MRI)
–  transitional cell carcinoma (TCC)  CT or biopsy
–  Renal lymphoma  CT in case clinically relevant
–  Metastasis  CT in case clinically relevant

28. Xanthogranulomatous pyelonephritis
• Rare inflammatory condition usually secondary to
chronic obstruction
• Is associated with a staghorn calculus in
approximately 70% of cases.
• Classic urographic triad:
– unilaterally decreased or (more commonly) absent renal
excretion
– a staghorn calculus
– poorly defined mass or diffuse renal enlargement.

29. Xanthogranulomatous pyelonephritis
right xanthogranulomatous pyelonephritis

30. • Benign:
– Pyelum  low dose or CT
–  Calyceal Diverticulum  low dose or CT
– (adrenocortical) Oncocytoma  CT or biopsy
–  Infected cyst / Abcess / hematoma  low dose (if hyperattenuating:
CT, MRI or biopsy)
–  xantogranulomatous pyelonephritis  low dose or CT
–  Angiomyolipoma  low dose or CT (if hyperattenuating: MRI)
• Malignant:
– (cystic) Renal Cell Carcinoma (RCC)  CT or biopsy (if
hyperattenuating: MRI)
–  transitional cell carcinoma (TCC)  CT or biopsy
–  Renal lymphoma  CT in case clinically relevant
–  Metastasis  CT in case clinically relevant
Focal renal FDG uptake
Differential

31. Reference: PET
• Positron Emission Tomography in Renal Cancer.pdf
• PET and PETCT of Urological Malignancies An Update Review.pdf
CT/MRI
• Simplified imaging approach for evaluation of the solid renal mass in adults Radiology
2008 331.pdf
• Hyperattanuating renal masses etiology pathogenesis and Imaging Evaluation Radiogr
2007 1131[1].pdf
Focal renal FDG uptake
Differential