Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 317
Causes of Hydronephrosis
Genitourinary Obstruction
Renal/ureteral stone
Transitional cell carcinoma
Sloughed papilla
Blood clot
Posterior urethral valves
Ureterocele
Ureteropelvic junction
obstruction
Ureteral stricture (prior
infection, surgery,
radiation)
Neurogenic bladder
Extrinsic Obstruction
Retrocaval ureter
Prostatic hypertrophy
Tumor (ibroid, ovarian
carcinoma, lymphoma)
Lymphadenopathy
Retroperitoneal ibrosis
Comments
Look for stone in common
sites of obstruction:
ureterovesical junction
and ureteropelvic junction
Hematuria
Hematuria
Bilateral, pediatric diagnosis
May be orthotopic or
heterotopic
If heterotopic, look for renal
duplication abnormality
Extrarenal pelvis may be
dilated out of proportion
to calices
History aids in diagnosis
Check for postvoid residual
May need CT for diagnosis
Enlarged prostate impinges
on bladder
Abnormal mass seen in
pelvis
Abnormal mass seen in
pelvis
Mass encasing the aorta
CT may be needed for
diagnosis
Genitourinary Obstruction
Aneurysm
Endometriosis
Pregnancy
Nonobstructive
Vesicoureteral relux
Congenital megacalices
Prior obstruction
Infection
High low states (diabetes
insipidus, psychogenic
polydipsia)
Distended bladder
Comments
Should be obvious on
Doppler assessment of
vessels
Mass typically seen in
pelvis
Ureter dilated to pelvic brim
Cortical scarring, typically in
upper poles
May be unilateral or
bilateral
If associated with
congenital megaureter,
both dilated ureter and
calices will be present
May need contrastenhanced
CT for
diagnosis
Prior severe dilatation may
not return to normal
Signs and symptoms of
infection
Typically mild dilatation
Returns to normal after
bladder emptying
PITFALLS IN ASSESSMENT
OF OBSTRUCTION
Although obstruction typically causes dilatation, early in the
process the renal collecting system may not dilate. In cases of
renal failure, a poorly functioning kidney may not make suicient
urine to demonstrate dilatation. In addition, in cases of severe
obstruction, pelvocaliceal rupture may lead to decompression
of the collecting system with a perinephric hematoma/urinoma.
Hydronephrosis (a condition in which dilated calices communicate
with central collecting system) should be distinguished from
multiple parapelvic cysts (which do not communicate).
CONGENITAL ANOMALIES
Anomalies Related to Renal Growth
Hypoplasia
Renal hypoplasia is a renal parenchymal anomaly in which there
are too few nephrons. Renal function depends on the mass of
the kidney. True hypoplasia is a rare anomaly. Many patients
with unilateral hypoplasia are asymptomatic; the condition is
typically an incidental inding. Patients with bilateral hypoplasia
oten have renal insuiciency. Hypoplasia is believed to result
from the ureteral bud making contact with the most caudal
portion of the metanephrogenic blastema. his can occur with
delayed development of the ureteric bud or from delayed contact
of the bud with the cranially migrating blastema. Hypoplasia is
established when fewer but otherwise histologically normal renal
lobules are identiied. 14 At ultrasound, the kidney is small but
otherwise appears normal.
Fetal Lobation
Fetal lobation is usually present until 4 or 5 years of age; however,
persistent lobation is seen in 51% of adult kidneys. 15 here is
infolding of the cortex without loss of cortical parenchyma. At
ultrasound, sharp clets are shown overlying the columns of
Bertin. 16
Compensatory Hypertrophy
Compensatory hypertrophy may be difuse or focal. It occurs
when existing healthy nephrons enlarge to allow healthy renal
parenchyma to perform more work. he difuse form is seen