Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 313
the surface is concave; the medial surface is known as the renal
hilum. he renal hilum is continuous with a central cavity called
the renal sinus. Within the renal sinus are the major branches
of the renal artery, major tributaries of the renal vein, and the
collecting system. 3 he remainder of the renal sinus is packed
with fat. he collecting system (renal pelvis) lies posterior to the
renal vessels in the renal hilum (Fig. 9.3).
Renal parenchyma is composed of cortex and medullary
pyramids. he renal medullary pyramids are hypoechoic relative
to the renal cortex and can be identiied in most normal adults
(Fig. 9.4). Normal renal cortex is typically less echogenic than
adjacent liver and spleen. Platt et al. 5 found that 72% of 153 patients
with renal cortical echogenicity equal to that of the liver had normal
renal function. Greater renal echogenicity than liver echogenicity
showed a speciicity and a positive predictive value for abnormal
renal function of 96% and 67%, respectively. However, the sensitivity
of this ultrasound criterion was poor (20%).
During normal development, two parenchymal masses called
ranunculi partially fuse. Parenchymal junctional defects occur
at the site of fusion and must not be confused with pathologic
processes (e.g., renal scar, angiomyolipoma). he junctional
parenchymal defect is most oten located anteriorly and superiorly,
typically at the junction of the upper and middle thirds of the
kidney, and can be traced medially and inferiorly into the renal
sinus. Usually, it is oriented more horizontally than vertically
and therefore it is best appreciated on sagittal scans 6 (Fig. 9.5).
Junctional cortical defects are more oten shown within the right
kidney, although let junctional cortical defects may be detected
with favorable acoustic windows.
A hypertrophied column of Bertin (HCB) is a normal variant;
it represents unresorbed polar parenchyma from one or both of
the two subkidneys that fuse to form the normal kidney. 7
Sonographic features that may aid in the demarcation of HCB
include indentation of the renal sinus laterally and a border
formed by the junctional parenchymal defect. Hypertrophied
columns are usually located at the junction of the upper and
middle thirds of the kidney and contain renal cortex that is
continuous with the adjacent renal cortex of the same subkidney.
FIG. 9.3 Anatomy of the Kidney, Ureter, and Bladder.
A
B
FIG. 9.4 Normal Kidney. (A) Sagittal and (B) transverse sonograms of normal anatomy with corticomedullary differentiation show relatively
hypoechoic medullary pyramids, with cortex slightly less echogenic than the liver and spleen.