Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 361
require two renal cysts (unilateral or bilateral) to have the
diagnosis of ADPKD disease. For patients age 30 to 59, two cysts
in each kidney are required, and for those age 60 or older, four
cysts in each kidney are needed. hese criteria were modiied
to account for the relatively later onset of disease in patients
with type 2 polycystic kidney disease, but fewer than two renal
cysts in at-risk individuals older than age 40 was still suicient
to exclude the disease. 252
FIG. 9.70 Autosomal Recessive Polycystic Kidney Disease. Twoyear-old
patient with renal insuficiency. Sagittal sonogram shows marked
renal enlargement and innumerable microcysts.
Autosomal dominant polycystic kidney disease (ADPKD)
results in a large number of bilateral cortical and medullary renal
cysts. he cysts vary in size and are oten asymmetric. ADPKD
is the most common hereditary renal disorder and has no gender
predilection. Its incidence is 1 : 500 to 1 : 1000, and ADPKD
accounts for 10% to 15% of patients receiving dialysis. Up to
50% of patients have no family history. Seemingly sporadic
involvement is caused by variable expression and spontaneous
mutations. Signs and symptoms of palpable masses, pain,
hypertension, hematuria, and UTI usually do not develop until
the fourth or ith decade. Renal failure develops in 50% of patients
and is usually present by age 60. 248 Complications of ADPKD
include infection, hemorrhage, stone formation, cyst rupture,
and obstruction. Stone formation tends to occur in patients with
more and larger cysts. 249 Associated anomalies include liver cysts
(30%-60%); pancreatic cysts (10%); splenic cysts (5%); cysts in
thyroid, ovary, endometrium, seminal vesicles, lung, brain,
pituitary gland, breast, and epididymis; cerebral berry aneurysms
(18%-40%); abdominal aortic aneurysm; cardiac lesions; and
colonic diverticula. Patients with ADPKD who are not receiving
dialysis do not have an increased incidence of RCC. 248
Ultrasound is used for screening families of patients with
ADPKD, as well as for routine follow-up. At sonography, the
kidneys are enlarged and replaced by multiple bilateral, asymmetric
cysts of varying size (Fig. 9.71). Cysts complicated by
hemorrhage or infection have thick walls, internal echoes, and/
or luid-debris levels. Dystrophic calciication within cyst walls
or stones may be seen as echogenic foci with sharp, distal acoustic
shadowing.
Renal cysts in patients younger than 30 years are rare. Ravine
et al. 250 modiied the criteria of Bear et al. 251 and reported that
patients age 30 or younger with a family history of ADPKD
Multicystic Dysplastic Kidney
Multicystic dysplastic kidney (MCDK) is a nonhereditary
developmental anomaly also known as renal dysplasia, renal
dysgenesis, and multicystic kidney. he kidney is small, malformed,
and composed of multiple cysts with little, if any, normal
renal parenchyma. he kidney functions poorly if at all. he
dysplastic change is usually unilateral and involves the entire
kidney, although rarely it may be bilateral, segmental, or focal.
If bilateral, involving the entirety of both kidneys, it is incompatible
with life. Men and women are equally afected, as are both
sides. Up to 30% of patients have a contralateral UPJ obstruction.
he exact pathogenesis is obscure. However, 90% of cases are
associated with some form of urinary tract obstruction during
embryogenesis. he severity of the malformation and the age of
the patient at diagnosis account for the varying manifestations
of MCKD, from a large, multicystic mass present at birth to a
kidney with smaller cysts that are asymptomatic and not discovered
until adulthood.
Ultrasound indings of MCKD include (1) multiple noncommunicating
cysts of varying size, (2) absence of normal parenchyma
and normal renal sinus, and (3) focal echogenic areas
representing primitive mesenchyma or tiny cysts 253 (Fig. 9.72).
In adults a small, cystic renal fossa mass is seen, and cyst wall
calciication is appreciated as echogenic foci with shadowing.
Calciication may be so extensive that ultrasound visualization
is impossible, and CT is required to make the diagnosis. Segmental
disease is usually seen in duplex kidneys, and if the cysts are
tiny, the mass may appear solid and echogenic.
Lithium Nephropathy
Known complications of chronic lithium administration include
nephrogenic diabetes insipidus (polyuria-polydipsia syndrome)
and/or chronic renal disease. Diabetes insipidus develops in up
to 40% of patients on chronic lithium therapy, and is typically
reversible. On the other hand, a smaller subset of patients may
develop chronic focal interstitial nephritis that is manifested by
a progressive, permanent defect in urine concentrating ability
and chronic renal insuiciency. he diagnosis is typically made
based on clinical criteria, but biopsy indings include tubulointerstitial
ibrosis, tubular dilatation, and microcysts. 254
he histopathology of chronic lithium nephrotoxicity is
manifested at ultrasound by numerous microcysts and punctate
echogenic foci. hese foci are thought to be microcysts rather
than nonshadowing calciication 255 (Fig. 9.73).
Multilocular Cystic Nephroma
Multilocular cystic nephroma (MLCN) is an uncommon benign
cystic neoplasm composed of multiple noncommunicating cysts