Renal Mass: Cystic versus Solid

Renal Mass

Cystic versus Solid

Nancy Chouinard and Ken Marken

A renal sonogram may be ordered to identify a mass or characterize the nature of a known mass. The task of the sonographer is to define whether the mass is cystic or solid. When the mass is cystic, it must be further defined sonographically to determine whether alternative imaging or other diagnostic procedures are necessary.

The sonographer must take particular care to demonstrate accurately whether the cyst is simple or contains features such as thick walls, septations, or nodules. The Bosniak Renal Cyst Classification System is a rubric for determining patient management based on these features.1 Although the system also includes contrast enhancement on CT, the remaining criteria can be helpful in determining appropriate follow-up of a renal cyst demonstrated on a sonogram (Table 7-1).

When cystic lesions are associated with decreasing renal function or other symptoms, such as hematuria or hypertension, a treatment plan must be developed to avoid other complications. The sonographic examination may assist in defining whether or not the renal cysts are part of a genetic disease.

This chapter explores numerous cystic lesions and cystic diseases of the kidneys. Descriptions of renal neoplasms and the normal sonographic appearance of the kidneys are provided in Chapter 5.

Simple Renal Cysts

Cortical Renal Cysts

Cortical renal cysts are common and have been identified in patients of all ages, although they are seen with increasing frequency with increased age. The exact origin of cortical renal cysts is unknown, but they are thought to be acquired. Cysts may be unilateral or bilateral, solitary or multiple. Simple cysts are usually asymptomatic and considered benign, although pain or hematuria may be present.

Sonographic Findings

The sonographic appearance of a renal cyst should meet the criteria of a simple cyst. The cyst should be anechoic, thin-walled, and round or oval, and the sonogram should show acoustic enhancement posterior to the cyst (Fig. 7-2). Edge shadowing is frequently shown along the lateral margins of the cyst. Doppler analysis of the cyst shows the absence of flow (Fig. 7-3, A). In addition, aside from recognition of a simple cyst, sonography can examine for renal contour or relational anatomy changes. The claw sign is a concavity in the renal contour where the parenchyma appears to be cupping the cyst or mass, indicating that the cyst or mass has a renal origin.2 A renal cyst or mass can cause distortion of the perirenal fat outline or displace adjacent structures (Fig. 7-3, B).

Complex Renal Cysts

When a cyst does not meet the criteria of a simple cyst, it may be classified as a complex cyst. Complex cysts may exist within the cortex, medulla, or pelvis. A complex cyst may have one or all of the following findings: a perceptible wall, internal echoes, and variable enhancement. A perceptible wall may include wall (mural) calcification, irregularity, nodularity, or thickening. Internal echoes may include thick viscous fluid, debris, or septations. Septations may result from material aggregating within the fluid or possibly from the inner lining of a cyst separating from its wall (see Table 7-1). These cysts can be hemorrhagic cysts, infected cysts, multilocular or septated cysts, cystic malignancies, or calcified cysts (Fig. 7-5). The diagnosis may be made based on the patient’s symptoms or may require additional imaging with CT or needle aspiration and histologic examination.

Calcification in Cyst

Calcifications within a cyst wall may be identified in a cyst that has been previously infected or hemorrhagic. A small amount of calcification may be clinically insignificant; however, thick calcifications are worrisome for malignant disease and should be investigated further.

Aug 27, 2016 | Posted by in ULTRASONOGRAPHY | Comments Off on Renal Mass: Cystic versus Solid
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