NEPHROGENIC RESTS - PowerPoint Presentation

Slide1

NEPHROGENIC RESTS

The fetal kidney is formed by development of

nephrons

from fetal

metanephric

blastema

surrounding the

ureteric

bud

The fetal renal tissue matures into normal renal parenchyma during gestation

But occasionally fetal tissue persists into infancy as microscopic foci called

nephrogenic

rests Slide2
Slide3

Nephrogenic

rests are found in approximately 1% of infant kidneys at autopsy

Associated with an increased risk of

wilms

tomor

Associated with many syndrome :

1-Beck with-

wiedemann

2-Hemihypertrophy

3-Sporadic

aniridia

Slide4

Children with

identifible

syndromes once diagnosed should be screened for the development of

wilms

tumor

Nephrogenic

rests are associated with other lesions such as

multilocular

cystic

nephroma

and

multicystic

dysplasia usually without malignant complicationsSlide5

The terms

nephrogenic

rest and

nephroblastomatosis

describe persistence of embryonic renal parenchyma (

metanephric

blastema

) beyond 36 weeks of gestation when

nephrogenesis

is normally complete.

This persistent

metanephric

blastema

may undergo transformation into the malignant

embryonal

renal tumor known as

nephroblastoma

-or

wilms

tumorSlide6

It is well accepted that

nephrogenic

rests are precursor lesion to an estimated 30%-40% of

wilms

tumor

However the cause of

malignanttransformation

of

nephrogenic

rests to

wilms

tumor is not known

Nephrogenic

rests are discovered incidentally in approximately 1% of infant kidneys

Associatedwith

other mass ; cystic partially differentiated

nephroblastoma

(CPDN)Slide7

The fetal kidney begins definitive formation at 5 weeks

Fetal tissue around the

ureteric

bud called the

metanephric

blastema

is then induced to form

nephrons

around the collecting ducts in a centrifugal fashion adding layers of

nephrons

around each individual

medullary

ray

At 28weeks gestation the formation of renal lobes is generally complete

Nephrogenesis

is complete at approximately 36 weeks gestationSlide8

Nephrogenic

rests may be single –multiple –or diffuse

Multiple or diffuse

nephrogenic

rests are also referred to as

nephroblastomatosis

These rests are thought to represent foci of incomplete maturation of

embryonal

primitive cells

1% of infant autopsies and are typically absent in infants 4 months of age and older

Two

types of

nephrogenic

rests ;

1-intralobar(anywhere within the lobe)

2-perilobar(found in the cortex)Slide9
Slide10

Perilobar

nephrogenic

rests are usually multiple and may form a band of

metanephric

blastema

at the periphery of the lobe (diffuse

perilobar

nephrogenic

rests)

They are well circumscribed and usually smooth

Perilobar

much more than

intralobar

Slide11
Slide12

Intralobar

nephrogenic

rests occur randomly within the lobe and are not limited to the periphery

Margins are usually irregular are often indistinct and may

interdigitate

with the normal adjacent

interstitium

of the kidney

Stroma

or epithelium(rather than

blastema

) is predominant constituent tissue Slide13

Clinical presentation

Occult incidentally

Patients with

intralobar

nephrogenic

rests present with

neoplastic

change (

wilm

)

(median 16 months)

Perilobar

(median 36months)

Diffuse

nephroblastematosis

may manifest as unilateral or bilateral flank masses

The renal enlargement of diffuse

nephroblastomatosis

may be palpable at birth and is usually discovered within the first 12 months of life Slide14

Associated syndromes and genetic defects

Syndromes associated with

perilobar

nephrogenic

rests include

Beckwith-

wiedemann

syndrome(gigantism-

macroglossia

-

omphalocele

and genitourinary anomalies) and

hemihypertrophy

(fig5-6)

Some patients with

beckwith-wiedemann

syndrome and

hemihypertrophy

have abnormalities of the more distal loci of chromosome band 11p 15 (this 11p 15 locus has been referred to as

wilms

tumor gene)Slide15
Slide16
Slide17
Slide18
Slide19

Up to 77% of these patients have

perilobar

nephrogenic

rests and up to 56% have

intralobar

nephrogenic

rests

Perlman syndrome is similar to

beckwith-wiedemann

syndrome in that it manifests with

visceromegaly

gigantism and

cryptorchidism

-

butit

is distinguished by

polyhydramnios

and characteristic

facies

Perlman

syndromeis

also associated with

perilobar

nephrogenic

rests

asis

trisomy

18 syndromeSlide20

Of those syndrome associated with

perilobar

nephrogenic

rests –

hemihypertrophy

(alone or as part of

beckwith-wiedemannsyndrome

)

hasthe

highest associated with the development of

wilms

tumor-estimated at 3% of cases

Predominantly

intralobar

nephrogenic

rests are found in patients with

drash

syndrome (ambiguous genitalia-and progressive renal failure in genotypic males)

And sporadic

aniridiaSlide21
Slide22

Both of these syndrome s have a strong associated with abnormalities of chromosome band 11 p 13 (known as

wilms

tumor gene )

Which is thought to act a

wilms

tumor suppressor

Virtually 100% of patients with sporadic

aniridia

have

intralobar

nephrogenic

rests (20% also have the

perilobar

type )and up to 78% of patients with

drash

syndrome have

intralobar

nephrogenic

rests (11% have the

perilobar

type)Slide23

Intralobar

nephrogenic

rests are also found in WAGR(

wilms

tumor –

aniridia

–genital abnormalities and mental retardation)syndrome

Intralobar

neph

rests although less common than the

perilobar

type have a higher associated with the development of

wilm

s tumor

Patients with sporadic

aniridia

(either as an isolated anomaly or in associated with WAGR syndrome) have the highest likelihood (estimated at 33%of cases) of developing a

wilms

tumorSlide24

HISTOLOGIC CHARACTERISTICS

Subtype of

neph

rests that reflect their biologic behaviors and appearances

At

histologic

analysis –

neph

rests show variable proportions of

blastema

-

stromal

- and epithelial elements the appearance and of these elements can be used to

subclassify

them as dormant(nascent)-

sclerosing

(obsolescent)

Hyperplastic

-or

neoplastic

Neph

rests may regress-

sclerose

or become

mitotically

active –respectively giving rise to larger rests or frankly

neoplastic

rests (the latter being synonymous with

wilms

tumor)Slide25
Slide26

This classification scheme applies to both

intralobar

and

perilobar

neph

rests

Dormant (nascent);

blastema

or epithelial

But quite small-usually no bigger than a

glomerulus

Sclerosing

(regressing or obsolescent) rests are also microscopic and are characterized by

stromal

elements with few or no mitotic cells and usually few epithelial elementsSlide27

This type of rest is believed to be the end stage of rest regression

Dormant and

sclerosing

rests are both unlikely to transform into

wilms

tumor and thus are not premalignant entities

They are –however often found elsewhere in the parenchyma of kidneys that contain

wilms

tumor dormant and

sclerosing

rests are found incidentally at biopsy or resection of a

wilms

tumorSlide28

Hyperplastic

and

neoplastic

rests are larger and may be microscopic or macroscopic lesion resulting from proliferation of one or more cells in the rest

Represent proliferation of most or all of the cells of the rest

Hyper plastic rest are proliferative they are not believed to give rise to

wilms

tumor Slide29

Neo plastic rests which are thought to give rise to and be synonymous with

wilms

timor

–result from proliferation of a single cell within a rest they may be microscopic or macroscopic

Neoplastic

rests tend to be spherical and from

expansile

masses that are clearly demarcated from and exert mass effect on surrounding parenchyma Slide30

This mass effect suggests that the mass is rapidly enlarging

Both

neoplastic

and

hyperplastic

rests are

mitotically

active and may show cellular

atypia

The degree of

atypia

and mitotic activity helps distinguish hyperplasia from

neoplasia

Mitotic activity and

atypia

exist on a continuum and clear

distiction

of

neoplasia

from hyperplasia based solely on the appearance of the cellular constituents of the rest is often quite difficultSlide31

PATHOLOGIC CHARACTERISTICS

ONLY larger macroscopic rests (

hyperplastic

and

neoplastic

)are visible at gross inspection

Small mass(less than 3 cm) and appear as tan nodules in a background of normal renal parenchymaSlide32

Perilobar

neph

rests are found in the renal cortex or at the

corticomedullary

junction

Intralobar

rests may be found any where in the renal parenchyma

The number of rests is variable from few (typically

intralobar

neph

rests) to many (typically

perilobar

neph

rests)Slide33

In diffuse

nephroblastomatosis

the cut surface of the kidney may exhibit white plaques or whorls of tissue replacing much of the parenchyma and usually forming a rind at the peripherySlide34
Slide35
Slide36
Slide37

Small cysts are also commonly seen

Diffuse

nephroblastomatosis

may also contain masses if areas of

metanephric

blastema

have undergone

hyperplastic

or

neoplastic

changeSlide38

IMAGING APPEARANCE

Microscopic foci of

neph

rests are

radiologically

occult unless diffuse

nephroblastomatosis

is present

Diffuse

neph

rests may globally enlarge the kidneys

At us

corticomedullary

diff may be impossible in cases of

nephroblastomatosis

The kidneys may be diffusely

echogenic

or have NL parenchyma l

echogenic

variable –sized cysts have been with diff

nephroblastomatosisSlide39

At CT diffuse

neph

rests enhance little and from a thick rind at the periphery of kidney

The rind may show striated enhancement it may be difficult ton distinguish diffuse

nephroblastomatosis

from

autosomal

recessive polycystic kidney disease

leukemia or lymphoma and biopsy may be necessarySlide40
Slide41

Isolated macroscopic

neph

rests (

hyperplastic

or

neoplastic

) have a nodular appearance at imaging

at US they may be anechoic –

hypoechoic

or

hyperechoic

Slide42

At CT and excretory

urography

these nodules enhance less than adjacent renal parenchyma does and may if numerous cause the surface of the kidney to appear

lobulated

Simulating fetal

lobation

Similar nodular mass effect may be seen on the renal pelvis and calices

Enhanced ct demonstrates macroscopic rests better than us doesSlide43

Cotrast-enchancement

abdominal

Ctscan

rounded

hetergeneous

masses in the

rihgt

kidney with two focal areas of

hypoattenuation

(overhead) and two smaller areas of

hypoattenuation

in the left kidney (arrow) all lesions enhance less than

nl

renal parenchymaSlide44

At angiography the nodules do not

opacify

but contrast material may puddle in intervening normal renal parenchyma

The renal

hilar

vessels are normal but they attenuate as they extent to the periphery of the kidney

Magnetic resonance (MR_) imaging has been reported to show macroscopic foci (greater than 4mm in

dia

)

These foci appear

hypointense

relative to renal parenchyma on T1- weighted enhanced images and

iso

- to slightly

hyperintense

relative to renal parenchyma on T2-weightedimagesSlide45

T1-weighted MR shows masses have slightly lower signal intensity than that of renal parenchyma (arrow ) MR Slide46

T2weihgt MR right renal mass *arrow) has higher signal intensity than

nl

renal parenchyma two areas in the anterior

rt

kid (

arrowHEAD

)

corrresponding

to the low attenuation areas at CT are seen with T2 AND may have seen cysticSlide47

US of

rt

kid slightly

hypoechoic

mass in the upper poleSlide48

Contrast

enchanced

abdominal CT shows bilateral

rernal

masses Slide49

According

toone

report macroscopic

neph

rests are best seen on enhanced T1 – weighted .

At MR Imaging as well as at CT

neph

rests tend to appear

homogeneoyus

and

wilms

tumor heterogeneousSlide50

treatment

the choice of treatment however remains controversial

Rather –close radiologic follow-up is recommended to exclude the development of

wilms

tumor –which manifests as an enlarging massSlide51

Some advocate

chemothrapy

Stage 1

wilms

tumor for biopsy-proved

hyperplastic

neph

restsSlide52

Fig 13

Unenhanced abdominal CT shows enlarged kidneys with smooth contoursSlide53

Contrast enhanced abdominal CT heterogeneous enhancement of the kidneys and minimal

nl

renal parenchyma (arrowSlide54

Delayed contrast- enhanced CT collecting system effacement Slide55

Follow –up CT scan after

chemothrapy

shows marked reduction in the size of kid and massesSlide56

Sporadic

wilms

tumor Slide57

although the potential for invasion-

extrarenal

spread or metastatic disease is quite low the mass effect of growing

neph

rests may mechanically injure the kidney

Also with growth and increasing cell numbers the potential exists for an increase in the number of cells capable of

neoplastic

inductionSlide58

PROGNOSIS

CERTAINLY the presence of

neph

rests in a kidney is associated with an increased risk of

wilms

tumor development

Thus the highest risk for development of

wilms

tumor is probably in those

patiets

with diffuse

hyperplastic

perilobar

neph

rests of whom an estimated 35% develop

wilms

tumors during child hood

Remaining 65% of these

patiets

do not

develp

wilms

tumores

Slide59

SCREENING

It is

recOmmended

that children with a

neph

rests- associated syndrome such as

beckwith-wiedemann

syndrome or with identified

neph

rests undergo

abaseline

CT at diagnosis (for

patiets

with WAGR) OR 6 MONTHS OF AGE (FOR PATIETS WITH BECKWITH-

WIEDEMANNsyndrome

hemihypertrophy

-or

drash

syndrome)

Following renal

sono

shouldbe

performed every 3 months until the age of 7 years when the risk of

wilms

tumor development lessens

substantialySlide60

WILMS TUMOR

Wilms

tumor also known as

nephroblastoma

Is a malignant

embryonal

renal tumor composed of variable amounts of embryonic renal elements (

blastema

- epithelial and

stroma

)

It is the most common malignant tumor of the abdomen found in children

80% of patients with

wilms

tumors present between the ages of 1 and 5 years (mean age 36.5 months for boys and 42.5 months for girlsSlide61

No significant racial or gender predilection

Associated with genitourinary anomalies

Especially

cryptorchidism

(2.8%) and

hypopadias

(1.8%)

There is also a slightly increased prevalence of

wilms

tumors in patients with horseshoe kidneys

Bilateral 4%-13%

Children with bilateral

wilms

tumors and those with

neph

rests-associated

wilms

tumor present at a younger age (mean 2.5 )

Although

neph

rests are found elsewhere in 30%-44% of children containing

wilms

tumors

In the vast majority of patients with

wilms

tumors –

nephrogenic

rests are sporadic and not associated with a genetic abnormality or syndromeSlide62

In a small group of patients with sporadic

wilms

tumors –all or part of

wilms

tumor gene 1 is

deteted

A small group of cases of

wilms

tumor(1%-2%) is reported as being familial

Wilms

grows by expansion-forming a

pseudocapsule

Distorts collecting system

Invasion of the renal pelvis is un usual

Invasion of the renal vein and

inf

vena cava (4.1%)

Tumor thrombus extends into the right atrium (21%)

Metastases to the regional lymph nodes lung(85%) liver( 7%) bone (0.8%)

Most

relapes

occur within 2 year of initial diagnosisSlide63

Clinical presentation

Large painless-abdominal mass

10%

fo

llowing

trauma

Gross

hematuria

is un common

Microscopic

hematuria

25%

Gross

hematuria

may signify tumor invasion of the renal pelvis

Hyper tension 25%

Hyaluronic

acid in 74% elevatedSlide64

PATHOLOGIC CHARACTERISTICS

MOST

wilms

tumor s are large masses that distort the renal anatomic land marks

The appearances of cut section s vary from homogeneous to variegated depending on the amount of viable

neoplssm

necrosis –and hemorrhage present

This variegated appearance will also be affected by different tissue components (calcification-fat )within the tumor most tumors have a fibrous pseudo capsuleSlide65

HISTOLOGIC CHARACTERISTIC

Blastema

-

stroma

- and epithelium the components of

neph

rests and the fetal kidney are the three

histologic

component of

wilms

tumor

the microscopic appearance will vary depending on the proportions of these component

Tumors that contain all three component are referred to as

triphasic

wilms

tumorSlide66

Fig 15

Triphasic

wilms

tumorSlide67

Blastemal

areas may vary from diffuse to fairly well-defined aggregates of basophilic cells with high

nucleocytoplasmic

ratios

In some cases the tumors will show

differentition

along tissue lines that are not related to normal renal development such as striated muscle –fat bone cartilage or smooth muscle

These tissue have a

mesodermal

derivation such as that of

metanephric

blastema

Lesion s in which these

heterologous

mesodermal

elements such as cartilage and fat predominate are sometimes referred to as

teratoid

wilms

tumorsSlide68

The terms favor able and unfavorable

histologic

character are applied to

wilms

tumor

An unfavorable

histologic

character is defined as the presence of

anaplasia

6.2% of

wilms

tumors are

anaplastic

and characterized by

hyperchromatic

tumor cells with nuclei that are at least three times larger in diameter than the nuclei of adjacent tumor cells of similar type

Anaplastic

wilms

tumor tends to occur in older patients and is associated with an increased prevalence of lymph node metastases at diagnosis Slide69

Anaplastic

may be focal (localized) or diffuse (multiple topographic areas)

Although all

anaplastic

wilms

tumors are considered to have unfavorable

histologic

character the amount of

anaplasia

correlates with patient outcome

Patients with minimally

anaplastic

wilms

tumors have survival rates close to those of patients with similarly staged

nonanaplastic

wilms

tumors –whereas patients with diffuse

anaplastic

wilms

tumors fare substantially worse Slide70

Anaplastic

appears to confer resistance to chemotherapy not more aggressive tumor growth

Patients with diffuse

neph

rests who present with a

wilms

tumor at an older age (over about 3-4 years)Slide71

IMAGING APPEARANCE

At radiography

wilms

tumor may appear as a large flank mass which may obliterate the

psoas

margin

calcification is visible in approximately 9% of cases

Excretory

urography

may demonstrate

alarge

mass with

splying

but does not usually show invasion of the renal

calies

or collecting systemSlide72

Fig 16

A-excretory

urogram

shows

alarge

mass arising from upper

rt

kid with effacement and distortion but no define invasive of the collecting system

B-renal angiography show a

hypovascular

mass in the upper

Ctransverse

sono

a heterogeneous mass

wiyh

athin

rim renal parenchyma

anter

and posterSlide73

D-unenhanced abdominal CT scan

alow

attenuation

rt

renal mass

E-contrast-enhanced abdominal CT show a low attenuation slightly heterogeneous mass of renal origin

D-unenhanced abdominal CT scan

alow

attenuation

rt

renal mass

E-contrast-enhanced abdominal CT show a low attenuation slightly heterogeneous mass of renal originSlide74

At

sono

a predominantly solid but heterogeneous mass is seen often with anechoic areas from necrosis – hemorrhage or cyst formation Slide75

Fig 16-17

Image of

rt

kid a heterogeneous

paritially

cystic

massb

B-

inf

cava show

echogenic

material filling its

luman

(arrow) posterior extension of the mass and

adenopathy

Slide76

C-axial T1

mr

large heterogeneous mass

rt

kid

D-

axialgad

-

enchanced

T1 MR

enchances

less than

nl

renal parenchymaSlide77

Echogenic

areas that represent fat or calcium are also seen occasionally demonstrated

The presence of fat in childhood

renaltumors

in comparison with adult renal tumor s is not indicative of

abenign

mass

The mass appears well demarcated from the adjacent renal parenchyma and usually adopts a spherical configuration Slide78

Assessment of the renal vein and

inf

vena cava for tumor thrombus is routinely performed at

sono

Ctis

the preferred modality for evaluating the mass itself excluding regional invasion

And for identifying

adenopathy

At ct

wilms

tumor typically appear s heterogeneous –sometimes showing fat hemorrhage necrosis cyst or calcification

The tumor is well circumscribed and

abeak

or claw of renal tissue may extend partly around the mass helping confirm its renal origin Slide79

The tumor enhances less than adjacent renal parenchyma

Venous invasion with tumor thrombus may be demonstrated at ct

Although it is slightly better visualized at us Slide80

At MR imaging

awilms

tumor appears as

awell

-circumscribed mass of low signal intensity with T1-weighted and high signal intensity with T2 –weighted

The mass enhances heterogeneous but less than adjacent renal parenchyma

Mrimaging

may also show evidence of vascular invasionSlide81

TREATMENT

Complete surgical resection is the primary method of therapy

A tumor that is incompletely

resected

(either because of

ivasion

of vital structures or tumor spill)is classified as stage

IIIdisease

Staging of

wilms

tumors is based on extent and completeness of resection of the tumor and the presence of regional and distant nodal and

nonnodal

metastases Slide82

Staging of

wilms

tumor according to the national

wilms

tumor study group

Stage

I;tumor

entirely confined within the capsule of the kidney –without

caosular

or vascular invasion

Biopsy has not been performed before resection

II ;tumor extends beyond the renal capsule-

biopsyhas

been performed before resection or tumor has ruptured

intraoperatively

but it is completely

resectedwith

tumor-free margins

Local invasion of capsule renal sinus or

hilar

vessels may be presentSlide83

III ;

RESIDUAL

nonhematogenous

spread of tumor confined to the abdomen as evidenced by either (a)positive lymph nodes in the abdomen or pelvis (b)peritoneal invasion

©peritoneal tumor implants ( d)residual tumor at surgical margins (e)

unresectablity

because of

invasioninto

vital structure s or (f)tumor

spilloutside

the flank at surgery

IV

Hematogenous

or lymph node metastases outside the abdomen or pelvis

V ; BILATERAL WILMS tumor at time of original diagnosisSlide84

Surgical resection is followed by chemotherapy which is stratified for tumor stage that is patients with more advanced stage tumors receive more chemotherapy adjuvant radiation therapy of the abdomen and whole lung is introduced for stage IV tumors

Adjuvant

abdomenal

irradiation is given in addition to chemotherapy

topatients

with

anaplasticstage

II-

Ivwilms

tumor Slide85

The treatment for bilateral

wilms

tumor s is individualized

Each kidney is individually staged and usually renal-sparing resection is performed bilaterally followed by chemotherapy if stage IV disease is present in one or both kidneys adjuvant abdominal and whole lung irradiation is usedSlide86

The role of the surgeon is critical to

aggurate

staging if in the opinion of an experienced surgeon the tumor cannot be completely

resected

without excessive risk to vital structures or when renal-sparing surgery is imperative (as in cases of bilateral

wilms

tumors) preoperative chemotherapy is administeredSlide87

PROGNOSIS

TREATMENT OF WILMS TUMOR IS ONE OF THE GREAT success stories of modern oncology

Today the prognosis for children with even advanced stages of

wilms

tumors is excellent

The 4 year relapse –free survival rates from national

wilms

tumor study 3 are as follows

Stage I 90%

Stage II 88.1%

Stage III 78.5%

Stage IV 77.9%Slide88

The 4 year overall survival rate rises to 96.3%

--85.9% for stages I—III DISEASE and is 83.6% for stage IV disease

Forstage

V

wilms

tumor the 4 year overall survival rate approximately 70%

Survival rates for patients with

wilms

tumor with focal

anaplasia

approach those for patients with similarly staged

nonanaplastic

wilms

tumor

However patients with diffuse

anaplastic

wilms

tumor fare substantially worse

The4 year survival rate for stage II disease is 59%

stageIII

45% and stage IV 7%Slide89

MULTILOCULAR CYSTIC NEPHROMA

THE TERM

MULTILOcular

cystic

nephroma

encompasses two

radiologically

and pathologically identical lesions which differ only in the cellular components of their septa

Cystic

nephroma

is the term given an entirely cystic lesion of the kidney in which the cyst are epithelium-lined and the septa consist only of fibrous tissue and mature tubules

This lesion is typically seen in adult women

The same lesion when it contains

metanephric

blastema

in its septa is called cystic partially differentiated

nephroblastoma

(CPDN) AND is found primarily in young boysSlide90

These two lesions are distinguishable only by means of

histopathologic

assessment

Despite the presence of

blastema

in CPDN

Wilmstumor

has not been reported in associated with this lesion

However there is a single case report of

wilms

tumor developing in kidney with a coexistent but separate CPDNSlide91

PATHOLOGIC CHARACTERISTIES

Both

cysticnephroma

and CPDN are similar at gross inspection

They are well demarcated from the adjacent renal parenchyma and consist of multiple cysts with intervening septa

No

expansile

tumor nodules are seen in either lesionSlide92

F 18

Transverse US show

amulticystic

mass without solid elements arising from the

lt

kid Slide93

Contrast-enhanced abdominal CT the

multicystic

mass from

lt

kid

Contrast-enhanced abdominal CT the

multicystic

mass from

lt

kidSlide94

HISTOLOGIC CHARACTERISTIES

BOTH ENTITIES HAVE FIBROCONNECTIVE TISSUE SEPTA LINED BY FLATTENED

CUBOidal

or slightly protruding (hobnail)epithelium

They can be differentiated by the presence of primitive

metanephric

blastema

in the septa of CPDN Slide95

Imaging appearance

Cystic

nephroma

and CPDN are

multilocular

renal tumors that cannot be distinguished from one another

radiologically

At us they appear as multiple - anechoic cystic structures with thin septa and no solid elements

At CT they appear as sharply circumscribed

multicystic

masses Slide96

F 18-20

US

rt

kid

multicystic

mass in the renal

fossaSlide97

unenhancedabdominalCT

low attenuation mass in the

rt

kid Slide98

Contrast enhanced abdominal CT

unenhancing

cystic spaces with slender enhancing septa Slide99

The cystic contents have attenuation values close to those water

The septa enhance but the cysts do not

At MR imaging the

multicystic

masses have low signal intensity with T1-weighted and increase in signal intensity with T2 –weighted and often show

septal

en

hancement

Slide100

TREATMENT AND PROGNOSIS

SURGICAL EXCISION OF BOTH CYSTIC NEPHROMA and CPDN is usually curative although occasionally CPDN

recures

locally

CPDN therefore are usually monitored

radiologically

for several years after resection

The prognosis for patients with

eitherlesion

is excellentSlide101

NEPHROGENIC RESTS OCCURRING IN THE OTHER LESIONS

Neph

rests have been described in several congenital renal lesions including

Mesoblastic

nephroma

Multicystic

dysplastic kidney

And atypical renal dysplasia resulting from obstructive

uropathy

It is hypothesized that these congenital lesion s begin to form during

glomerulogenesis

with resultant and disruption of adjacent

metanephric

blastema

Slide102

As the lesion enlarges

metanephric

blastema

becomes trapped in the le

sion

There are less than 100 reported cases of cystic dysplasia containing

nephrogenic

rests despite the frequency of

multicystic

dysplastic kidney

These figures may reflect the growing trend toward conservative treatment of this disorder (observation without surgical resection)Slide103

It is plausible that any congenital renal lesion include

nephrogenic

rests

However the malignant potential of

nephrogenic

rests in these le

sions

is probably minimal as there have been only two reported cases of

wilms

tumor arising in

multicystic

dysplastic kidney and no reported cases of

wilms

tumor arising in

mesoblastic

nephromaSlide104
Slide105