Hyperechoic Renal Mass



Hyperechoic Renal Mass


Winnie C.W. Chu, MBChB, FRCR

Stella S.Y. Ho, PhD, RDMS

Michael P. Federle, MD, FACR



DIFFERENTIAL DIAGNOSIS


Common



  • Renal Angiomyolipoma (AML)


  • Renal Cell Carcinoma (RCC)


  • Wilms Tumor


Less Common



  • Fat in Renal Scar


  • Milk of Calcium Cyst


  • Renal Junctional Line/Cortical Parenchymal Defect


  • Renal Calculi


  • Renal Papillary Necrosis


  • Abscess, Renal


  • Emphysematous Pyelonephritis


  • Renal Metastases


Rare but Important



  • Focal Bacterial Nephritis


  • Xanthogranulomatous Pyelonephritis


  • Tuberculosis, Urinary Tract


  • Renal Oncocytoma


  • Renal Trauma


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • The same lesions that cause fat density (intensity) lesions on CT and MR usually cause echogenic lesion on US



    • However, echogenicity alone is not a reliable indication of fat content


    • Other sources of renal echogenicity include calcification & gas


    • Lesions with calcification: Milk of calcium cyst, RCC, Wilms tumor


    • Lesions with gas: Renal abscess, emphysematous pyelonephritis


Helpful Clues for Common Diagnoses



  • Renal Angiomyolipoma (AML)



    • Well-defined hyperechoic mass, similar to renal sinus


    • Echogenicity created by high fat content and multiple vessel-tissue interfaces


    • May have posterior shadowing not typically seen with other masses


    • Small lesion: AML has much higher echogenicity than RCC


    • Larger tumors usually have prominent vascularity, evident on color Doppler


    • May have central necrosis simulating malignant lesion


    • US alone is not reliable in diagnosing AML; requires CT confirmation (perform NECT and CECT)


  • Renal Cell Carcinoma (RCC)



    • 30% of small RCCs appear as hyperechoic masses, mimic AML



      • Presence of necrosis in mass or anechoic rim favors RCC but large overlap


    • Larger RCC may have foci of calcification (also echogenic), rarely fat


    • Mass with calcification & fat in adult = RCC, not AML


  • Wilms Tumor



    • Highly variable morphology, including echogenic foci (fat &/or calcification)


    • Heterogeneous echotexture with areas of necrosis or hemorrhage


    • Consider Wilms for any renal mass in a child (most present before age 5)


Helpful Clues for Less Common Diagnoses



  • Fat in Renal Scar



    • Example: Following partial nephrectomy



      • Fat may be placed into cortical defect


  • Milk of Calcium Cyst



    • Echogenic lesion associated with characteristic comet-tail/ring-down artifact


    • Calcification may layer creating a fluid/debris level


  • Renal Junctional Line/Cortical Parenchymal Defect



    • Echogenic line at anterosuperior aspect, upper pole of right kidney, lower pole of left kidney



      • Infolding of renal capsule and fat creates hyperechoic line or “mass”


    • Also can see extension of renal sinus fat into same location


    • Less commonly appears as a triangular focus known as parenchymal defect


  • Renal Calculi



    • Usually hyperechoic with sharp shadowing


    • Calculi or milk of calcium may form within a calyceal diverticulum, mimic a hyperechoic mass


    • Most stones show color and power Doppler twinkling artifacts



      • Useful ancillary finding in equivocal cases


  • Renal Papillary Necrosis




    • Early stage: Echogenic “ring” in medulla = necrotic papillae, surrounded by rim of fluid


    • Late stage: Multiple cystic cavities in medullary pyramids ± nonshadowing echogenic sloughed papillae


    • Calcified sloughed papilla with strong acoustic shadowing simulates stone, may cause obstructive hydronephrosis


  • Abscess, Renal



    • Gas-forming abscess will be echogenic


  • Emphysematous Pyelonephritis



    • Gas within infarcted, infected parenchyma is echogenic



      • Non-dependent linear echogenic lines with strong distal posterior acoustic shadowing


    • Clinically extremely ill patient with fever, flank pain and electrolyte imbalance


    • Different from emphysematous pyelitis where gas is limited to renal pelvis and calyces (less serious diagnosis)


  • Renal Metastases



    • Variable echogenicity, typically hypoperfused masses


    • Look for metastases in other organs


    • Most common primary tumors include lung carcinoma, breast carcinoma, contralateral RCC


Helpful Clues for Rare Diagnoses



  • Focal Bacterial Nephritis



    • Increased echogenicity is related to hemorrhage


    • Usually wedge-shaped, poorly defined margin, I focal vascularity on power Doppler


    • Can be hypoechoic, related to liquefaction and abscess formation


    • Can be multiple lesions with patchy heterogeneous renal parenchyma


    • Other associated features of renal inflammation: Renal enlargement, urothelial thickening of renal pelvis


  • Xanthogranulomatous Pyelonephritis



    • Highly reflective central echo complex with strong shadowing corresponding to large staghorn stone


    • Echogenicity depends on amount of debris and necrosis within the masses


  • Tuberculosis, Urinary Tract



    • Active stage: Papillary destruction with echogenic masses near calyces


    • Late stage: Calcified granuloma or dense dystrophic calcification associated with shrunken kidneys


  • Renal Oncocytoma



    • Cannot be differentiated from RCC on imaging


    • Variable in echogenicity, may contain central scar, central necrosis or calcification


  • Renal Trauma



    • Hematoma can be hyperechoic or heterogeneous during acute phase


    • Regional distortion of corticomedullary differentiation






Image Gallery









Longitudinal transabdominal ultrasound shows a typical large, homogeneous, hyperechoic mass image at the upper pole of right kidney. Note the faint posterior shadowing image.






Oblique transabdominal ultrasound shows a typical small, homogeneous, echogenic lesion image at the lower pole of the kidney without alternation of renal contour. A small RCC would not typically be this hyperechoic.







(Left) Longitudinal ultrasound shows two irregular large echogenic AML lesions image in a patient with tuberous sclerosis. These lesions are heterogeneous in appearance and may mimic malignant lesions. (Right) Longitudinal ultrasound shows a mildly echogenic lesion image in the upper pole of the right kidney. It is not as echogenic as most small AMLs. A tiny intralesional cystic component image is present.

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Aug 2, 2016 | Posted by in GENERAL | Comments Off on Hyperechoic Renal Mass
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