Circumscribed Changes in the Renal Pelvis and Renal Sinus

Table 49 ■ Circumscribed changes in the renal pelvis or renal sinus

Anechoic or hypoechoic Isoechoic or echogenic

Parapelvic cyst (solitary, multiple, p. 284) Hemorrhagic cyst (p. 287)

Sinus lipomatosis (p. 284) Pyelocalyceal stone (p. 288)

Parenchymal bands, hypertrophic renal columns Foreign body (drainage tube, p. 288) (p. 284)

Infected obstruction (p. 286)

Pyelitis (see p. 286)

Abscess, pyonephrosis (p. 286)

Inflammatory tumor, liquefying tumor (p. 287)

Xanthogranulomatous pyelonephritis (p. 287)

Carcinoma of the renal pelvis (p. 287)

Renal cell carcinoma, metastasis (p. 287)

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c o n Solitary parapelvic cysts (see Fig. 388c, p. 273; Fig. 389a, p. 273):

• Clinicalfeatures: may be tubular retention cysts (such as cortical and subcapsular cysts) or may have a lymphoid origin, arising from the lymphatic vessels of the renal sinus

• Sonographic criteria: The standard criteria for cysts are reviewed on p. 272. A cyst with an inherently flat shape may show internal echogenicity or irregular margins due to physical artifacts such as noise. A flattened oval shape is particularly common with multiple cysts.

n Multiple parapelvic cysts (Fig. 407; Fig. 388d, p. 273): usually bilateral, taking the form of "benign cystic lymphangioma."

• Several or numerous round, oval, or finger-shaped anechoic masses oriented toward the hilum

• Cyst boundaries are well defined by septations.

• CDS: absence of vascularity inside the cysts, with normal-appearing blood vessels in the septa

Parapelvic Cysts Ultrasound
Fig. 407a, b Multiple bilateral parapelvic cysts ("benign cystic lymphangioma"): round or oval anechoic masses in the central echo complex, separated from one another by septa. L = liver, K = kidney

n Atypical cyst (Fig. 408; see Fig. 392, p. 275; Fig. 401a, p. 280): The differential diagnosis includes calyceal cyst, abscess, cavitating tumor, flat cyst, sectional view of a parenchymal band, and obstructive pyelocalyceal ectasia

• Polygonal shape with intraluminal echoes due to noise

• Trabeculations or septations

• Extrarenal extension n Renal sinus lipomatosis (Fig. 409): excessive fat in the renal sinus

• Nonhomogeneous decrease of echogenicity in the central echo complex

• Patchy, tumor-like figures ("bear claws")

• Widening of the renal sinus echo complex with thinning of the parenchyma ("fatty atrophy"). Parenchymal-pelvic ratio often < 1:1

n Parenchymal bands, hypertrophic renal columns (Fig. 410; see Fig. 399, p. 279):

• Circumscribed, peg- or band-shaped iso- or hypoechoic area in the CEC

• CDS: normal vascular architecture

Sinus Lipomatosis
Fig. 408a, b Cystic calyceal ectasia. a Cystic anechoic and echogenic masses in the central echo complex. Obstructive calyceal ectasia? b Spectral analysis of the segmental and interlobar arteries shows a high RI of 0.76 (values > 0.70 indicate an obstruction with 77-96% accuracy)
Interlobar Reanl Artery

Fig. 409a, b Sinus lipomatosis. a Typical transformation of the central echo complex (arrows), which appears hypoechoic with irregular margins. K = kidney b "Fatty atrophy": increased fat in the renal sinus with thinning of the parenchyma (cursors: parenchymal-pelvic ratio of 0.6)

b

Fig. 409a, b Sinus lipomatosis. a Typical transformation of the central echo complex (arrows), which appears hypoechoic with irregular margins. K = kidney b "Fatty atrophy": increased fat in the renal sinus with thinning of the parenchyma (cursors: parenchymal-pelvic ratio of 0.6)

Renal Sinus

Fig. 410a, b Parenchymal bands. a Isoechoic mass completely occupies the renal section with slight ectopia and malrotation of the right kidney. b CDS: normal vascular architecture, no tumor vascularity. K = kidney

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c o n Infected obstruction (Fig. 411):

n Note: The main priority is to clear the outflow obstruction as soon as possible.

• Hypoechoic dilatation of the pyelocalyceal system

• Involvement of the ureteropelvic junction

Fig. 411 Infected obstruction: very hypoechoic pyelectasis (P) with swelling of the renal pelvic wall (cursors)

• Inflammatory swelling of renal pelvic wall to > 2 mm

• Anechoic or hypoechoic distention of the renal pelvis

Fig. 412 Suppurative pyelitis (urosepsis): faint hypoechoic rim in the central echo complex with swelling of the renal pelvic wall (arrows)

n Abscess or pyonephrosis (Fig. 413): may require decompression by percutaneous needle aspiration or drainage

• Anechoic or hypoechoic mass, often multiple

• Ill-defined margins

Renal Sinus
Fig. 413a, b Renal pelvic abscess and pyonephrosis. a Abscesses: anechoic "cystic" masses in the central echo complex. b Pyonephrosis: ill-defined confluent 286 masses, some with a tapered outline

Fig. 414 Liquefaction (intratumoral hemorrhage) in a carcinoma of the renal pelvis (cursors indicate the longitudinal renal diameter and tumor diameter)

• Absence of vascularity

• Wall of renal pelvis thickened to > 2 mm n Inflammatory mass, cavitating tumor or intratumoral hemorrhage (Fig. 414): Other inflammatory masses may also occur, such as tumor-mimicking vasculitis. n Xanthogranulomatous pyelonephritis: chronic inflammatory mass with fatty infiltration, also located in the parenchyma

• Irregular, heterogeneous hypoechoic mass n Renal pelvic carcinoma (urothelial carcinoma, Fig. 415):

• Circumscribed hypoechoic mass, often exhibiting the same echo pattern as the renal pelvis and ureter

• CDS: atypical vascularity (aberrant tumor vessels)

n Renal cell carcinoma (invading the renal pelvis and sinus), metastasis (Fig. 416):

Kidney Pelvic Area
Fig. 415 Renal pelvic carcinoma (T): hypoechoic mass growing into the ureter (difficult to distinguish from an infected obstruction, see Fig. 411, p. 286)

Fig. 416 Renal cell carcinoma (T) that metastasized to the lung. A metastatic lymph node (LN) is visible in the renal sinus echo complex of the same kidney (K)

n CDS: atypical vascularity (aberrant tumor vessels)

n Hemorrhagic cyst (Fig. 417): mainly requires differentiation from a tumor

• Smooth, round to oval hypoechoic area in the renal sinus echo complex

• Fine, flocculent internal echoes 287

Schmidt, Ultrasound © 2007 Thieme

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Fig. 417 Hemorrhagic parapelvic cyst (arrows) in the kidney, suspicious for metastasis from color carcinoma. FNAB: no tumor cells. CT: intracystic hemorrhage n Vascular calcification (segmental branches of the renal artery, Fig. 418):

• Echogenic streaks or bands in the renal sinus echo complex. It is common to see faint tramlines bordering a central, thread-like anechoic lumen.

• Acoustic shadows may occur, depending on the degree of calcification.

Where Parapelvic Area Body

Fig. 418 Vascular calcification (arrow): echogenic "tramlines" with a central anechoic lumen n Renal calyceal or pelvic stone (staghorn calculus, Fig. 419): The differential diagnosis includes vascular calcification, calcified papillary tips, and tumor-associated calcification.

• Intense echo pattern with a distal acoustic shadow

• Located in the calyx with hydrocalyx; in the ureteropelvic junction with an obstructed calyx or calyceal neck or with a renal pelvic obstruction n Drainage tube appearing as a foreign body (see Fig. 576a), p. 388): typical double-walled linear structure with a central, anechoic fluid-filled channel.

Echogenic Renal Pyramids

Fig. 419a, b Renal pelvic stone (nonobstructing): hyperechoic stone with a distal acoustic shadow (S; the "twinkling artifact" is helpful for confirming stones). b Papillary tip calcification in diabetes: bright echo at the tip of the medullary 288 pyramid (arrow) with an incomplete acoustic shadow (S)

Fig. 419a, b Renal pelvic stone (nonobstructing): hyperechoic stone with a distal acoustic shadow (S; the "twinkling artifact" is helpful for confirming stones). b Papillary tip calcification in diabetes: bright echo at the tip of the medullary 288 pyramid (arrow) with an incomplete acoustic shadow (S)

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