Diagnostic ultrasound ( PDFDrive )

CHAPTER 52 The Pediatric Urinary Tract and Adrenal Glands 1795
A
B
FIG. 52.30 Chronic Pyelonephritis in 12-Year-Old Boy With a History of Urinary Tract Infection. (A) and (B) The right kidney (R) is small
(7.6 cm) compared with the left kidney (L; 11.5 cm), and demonstrates thin, echogenic parenchyma. The left kidney is hypertrophied but otherwise
appears normal.
A
B
FIG. 52.31 Renal Candidiasis in a Premature Neonate. (A) and (B) Longitudinal and transverse images show echogenic material within the
calyces (A) and pelvis (B) of the right kidney (arrows) representing fungus balls.
evaluation of patients who typically have hematuria, proteinuria,
or renal failure. 79
Acute Kidney Injury
Acute kidney injury (AKI), deined as a sudden loss of renal
function, may be caused by inadequate renal perfusion, renal
cell injury, or urinary tract obstruction. AKI usually develops
in hospitalized children as a consequence of systemic illness or
its treatment, and not from primary renal disease. he most
common causes of AKI in children are renal ischemia, nephrotoxic
drugs, and sepsis. Other important causes are listed in the
accompanying box. All forms of AKI can lead to chronic kidney
disease (CKD). Recovery of renal function depends on the
underlying events leading to injury. 80
Ultrasound is usually the initial diagnostic imaging study
performed in the workup of children with AKI, and is oten the
only imaging required. he role of ultrasound is to assess renal
size and to exclude anatomic abnormalities as the cause of AKI.
Pathologic changes of the renal cortex, medulla, and collecting
system are readily detected and correlate well with histologic
indings. Doppler ultrasound yields information about renal
perfusion and vascular abnormalities. Ultrasound is also used
to localize the kidneys for percutaneous biopsy. Functional
information may be obtained with nuclear medicine studies that
can aid in more precisely diferentiating among prerenal, renal,
and postrenal causes of AKI. 80
In the setting of prerenal injury, the kidney is intrinsically
normal, and renal function is diminished as a result of decreased
renal perfusion. he kidneys are sonographically normal, and
restoration of renal perfusion results in a prompt return of renal
function.
Renal ischemia caused by prolonged prerenal injury or by a
severe hypoxic or ischemic insult can result in acute tubular
necrosis (ATN). Imaging indings depend on the severity of
parenchymal injury. A generalized increase in renal cortical
echogenicity indicates intrinsic renal disease (Fig. 52.34). In mild