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Focal renal FDG uptake
H. Adams
Gross anatomy
The Renal System Explained. Deshmukh. Nottingham University Press 2009
Renal column
Major calyx
Minor calyx
Transverse section
Incidental focal renal FDG uptake
FDG PET:Primary detection of RCC
Ceyssens, Mortelmans. Positron Emission Tomography in Renal Cancer. 2008, Renal Cell Cancer, Pages 131-136
N
9053
1710
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!
Incidental focal renal FDG uptakeDifferential
• 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
Imaging the Solid Renal Mass in AdultsCT: strategies
Ball versus the Bean
Visible onUnenhanced CT
+Enhanced CT
Not visible onUnenhanced CT
Ball versus the Bean
PET +
PET +
PET +
PET +
PET +
PET +PET +
PET - ?
PET - ?
PET +
Balltype RCC on CTUnenhanced CT + Enhanced CT
renal hump at unenhanced CT well-defined ball-type lesion
Radiology: Volume 247: Number 2—May 2008
RCCs in context of acquired cystic disease
Unenhanced CT + Enhanced CT
numerous masses bilaterally in atrophickidneys. Calcification (arrowhead) is seen in cyst
well-defined ball-type lesion: 2-cm enhancing mass: RCC
RCC on CTEnhanced CT: Improved mass conspicuity during nephrographic phase
Corticomedullary phase Nephrographic phase: RCC
Bean type lesion: TCCTransitional 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
Bean type lesion: TCC
Enhanced nephrographic-phase:poorly defined parenchymal masswith no alteration of the renal contour
Obliteration of caliceal elements inthe upper pole (phantom calyces
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
Angiomyolipoma (AML) Lesions
Indeterminate mass: pixel mapping; internal attenuation 16 HU. Clusters of pixels < < -20 : Angiomyolipoma, but Follow up required.
Multiple AMLs
Pt with Tuberous sclerosis: Near-total replacement of the right kidney by multiple fat-containing AMLsLeft kidney (K) also harbors numerous smaller but similar-appearing masses
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.
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
Renal metastases
Two poorly defined bean-type lesions:squamous cell lung carcinoma
Extensive hepatic metastatic disease and abnormal retroperitoneal lymphadenopathy
Renal lymphoma
large B-cell type non-Hodgkin lymphomaMultiple masses, incl. right kidney
Non-Hodgkin lymphoma: - bilateral Bean type lesions- Splenic lesions (arrow)
Focal renal FDG uptakeDifferential
• 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
Renal hematoma
Unenhanced CT: heterogeneouslyhyperattenuating (46 HU) renal mass(arrows) with calcifications
Enhanced CT scan during nephrographicPhase: no enhancement of the mass
Silverman et al. Hyperattenuating Renal Masses: Etiologies, Pathogenesis, and Imaging Evaluation. RG 2007
Benign Hyperattenuating CystsBenign 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.
Other types of hyperattenuating renal masses
• Renal cell carcinoma• Angiomyolipoma with minimal fat• Multilocular cystic renal cell carcinoma
RCC: enhancement of the mass
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
Focal renal FDG uptakeDifferential
• 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
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.
Xanthogranulomatous pyelonephritis
right xanthogranulomatous pyelonephritis
• 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 uptakeDifferential
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 uptakeDifferential