Chapter 114 - Renal Dysgenesis and Cystic Kidney Disease

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Campbell's 9th edition - review

Causes of Renal Agenesis

Defect in any of 3 structures
- Wollfian duct
- Ureteric bud
- Metanephric blastema

What is Potter's Syndrome?

BL Renal agenesis (~500 cases reported)
More common in M
Early death d/t pulmonary hypoplasia from oligohydramnios (not lack of renal tissue)
Potters Facies (hypertelorism, recessive chin, prominent inner canthal folds)
Orho defects from intrauterine compression (claw hand, bowed, clubbed feet)
Usually sporadic - assoc with other cong anom
RF - +ve FHx, increased maternal age

How common is unilateral renal agenesis?

1/1000 births
Often assoc with ipsilateral malformations of wolffian or mullerian duct structures
Also assoc with other urologic abN 50%
- VUR in 30%, obstr megaureter 10%, UPJO 5%

What is Mayer-Rokitansky-Kuster-Hauser Syndrome?

Unilateral renal agenesis (or ectopia) + ipsilateral mullerian defects + vaginal agenesis

What is renal dysgenesis?

Maldevelopment of the kidney that affects size, shape or structure

3 types of renal dysgenesis

1) Dysplastic (obstruction, VUR)
2) Hypoplastic (Ask-Upmark, oligomeganephronia)
3) Cystic (Genetic - VHL, TS; Sporadic - MCDK, ARCD)
* Dysplasia always accompanied with hypoplasia, but hypoplasia can occur alone

What is renal dysplasia

Leading cause of renal failure in kids
No universal definition, histologic diagnosis - embryonic mesenchyme + primitive renal components
Metanephric development starts but doesn't or can't finish

2 types of renal dysplasia

Altered genetic pathway that leads to abN development of nephron or collecting duct
Obstruction

Features of renal dysplasia

Distorted renal architecture
Immature or primitive glomeruli
Nephron precursors (comma and S-shaped bodies)
Hallmark* is "primitive ducts" - duct encircled by collars of fibromuscular cells - ?remnant of ureteric bud
Cartilage seen on micropathology
Cysts may or may not be present

What are associations to renal dysplasia?

Obstruction - get peripheral subcapsular cysts, more common with PUVs than with UPJO
Ectopic ureters
VUR
Other dysmorphic conditions (Fraser syndrome, BOR syndrome, renal-coloboma syndrome, Kallman syndrome, etc.

What is familial renal adysplasia?

When all or part of a group of renal anomalies is seen in one family, AD inheritance
- Renal agenesis
- Renal dysplasia
- MCDK
- Renal aplasia

Differentiate renal hypoplasia and hypodysplasia

Hypoplasia
- true "oligonehpronia" - +/- N ureteral orifice
- Oligomeganephronia
- Segmental (Ask-Upmark kidney)
Hypodysplasia
- With ectopic UO (lateral ectopia, medial or caudal ectopia + ureterocele)
- with N UO (+/- obstruction)
- with urethral obstruction
- Prune-belly syndrome

What is renal hypoplasia?

Kidney with decreased no of calyces & nephrons, but otherwise N (not dysplastic nor embryonic)
- May be unilateral or BL, if uni - contra shows growth
- May be assoc with VUR
- May be associated with ectoipc ureters

What is oligomeganephronia?

Marked reduction in number of nephrons + hypertrophy of each nephron - elongated widened nephrons
- Usually BL condition and is associated with low birth wt
- Affects M>F (3:1)
- Presents with vomiting, dehydration, thirst, polyuria
- AbN GFR, but stable for years - can retard growth
- Marked proteinuria & deterioration of renal function occurs in early teen yrs
- Small kidneys
- Nephrons are elongated and widened at proximal end
Rx - high fluid intake, correction of salt loss and acidosis, limit dietary protein to 1.5 g/kg, dialysis and renal Tx for ESRD

What is an Ask-Upmark kidney?

Smaller than N kidney + segmental hypoplasia - usually associated with VUR + Severe HTN - likely acquired lesion
- May occasionally find some areas of dysplasia
- HTN'sive encephalopathy & retinopathy can occur
- If disease is bilateral there may be some renal insufficiency
Rx - control HTN, correct VUR
- Unilateral: partial or total nephrectomy
- BL - medical management until dialysis or Tx

What is renal hypodysplasia?

Usually occurs with ectopic ureters
- extent of dysplasia usually correlates with degree of ectopic, often see ectatic rounded calyces - not same as from VUR
- lateral ectopica - usually assoc with VUR
- medial or caudal ectopica - may have ureterocele
Can occur with N UOs
- With obstr (prim obstr megaureter, UPJO) or without
Can be assoc with urethral obstruction or prune-belly
- PBS - absent abdominal musculature, various degrees of renal dysplasia, wide & tortuous ureters. Large and laterally placed orifices, UDT

What are renal cysts

Ectatic tubules or collecting duct, diverticulum of nephrone or isolated sac
- Usually arise from nephrons & collecting ducts after they have formed
- MCDK is an exception as it arises before formation of the nephrone
- benign multilocular cyst is another exception - neoplastic growth
- May represent a form of dysplasia, have different features
Cysts w/ hyperplastic lining - AD PCKD, TS, VHL, Acquired renal cystic diseaes
Cysts made of ectatic collecting ducts - AR PCKD & MSK

Genetic classifcication of renal cystic diseases (CHART)

MC JAFA Man
Multiple malformation syndromes with cysts (TS, VHL)
Congenital nephrosis (familial nephrotic syndrome)
Juveline nephronophthisis
AD PCKD
Familial hyploplastic glomeulocystic disease
AR PCKD
Medullary cystic disease

Non-Genetic classification of renal cystic diseases

MB MASS-D
MCDK
Benign multilocular cyst (Cystic nephroma)
MSK
Acquired renal cystic disease
Simple cysts
Sporadic glomerulocystic kidney disease
Calyceal diverticulum

Polycystic vs multicystic

Multicystic - refers to a dysplastic entity
Polycystic - refers to several conditions, mostly inherited, all w/o dysplasia and all w/ nephrons throughout kidney

DDX of BL renal cystic disease

AR PCKD
AD PCKD
TS
VHL
BL simple cysts
Acquired renal cystic disease

Characteristic features of AR PCKD

Chromosome 6
Usually large homogenous echogenic kidneys with cysts of collecting duct
- Usually NO discrete cysts (Microcystic)
- Assoc with congenital hepatic fibrosis and biliary dysgenesis

Characteristic features of AR PCKD

90% PKD1 (chromosome 16), 10% PKD2 (chromosom 4), <1% PKD 3
- Large kidneys with scattered renal cysts throughout
- Associated with berry aneurysms, diverticulitis, renal artery aneurysms, MV prolapse & cysts in the kidney, liver, spleen, pancrease, lung, arachnoid, pineal gland, SVs

Characteristic features of Juvenile nephronophthisis/meddulary cystic disease complex

Juvenile nephronophthisis - AR, chromosome 2
- cysts at corticomedullary jxn that develop AFTER onset of ESRD
Senior-Loken syndrome - AR
- cysts at corticomedullary junction, assoc with retinitis pigmentosa
Medullary cystic Disease - AD, cysts at corticomedullary jxn that develop BEFORE onset of ESRD

Characteristic features of Congenital nephrosis

Chromosome 19, dilatation of PCT with diffuse hypertrophy of podocytes
- 2 types: 1) Finnish type, 2) diffuse mesangial sclerosis type (assoc with Denys-Drash)

Characteristic features of Familial glomerulocystic kidney disease

Small or normal sized kidneys, glomerular cysts

Characteristic features of Tuberous Sclerosis

AD, TSC1 (chromosome 9 - hamartin), TSC2 (Chromosome 16 - tuberin)
cysts and AMLs throughout kidney
Assoc with mental retardation, skin adenoma sebaceum, epilepsy, cranial tubers, Ash-Leaf spots, Shagreen patch, Pheo

Characteristic features of VHL

AD (chromosome 3p25)
Renal cysts, adenomas, and clear cell RCC
Assoc with cerebellar hemangioblastomas, rentinal angiomas, pancreatic cysts, pheo, peididymal cystadenomas

Characteristic features of MCDK

Renal maldevelopment w/ diffuse cysts and remnants of early metanephric development

Characteristic features of Benign multilocular cyst

Benign cystic tumour of kidney (rest of kidney is N)
More common in boys when younger and women when older

Characteristic features of MSK

Ectatic collecting duct with rest of nephrons fairly normal

Characteristic features of Acquired renal cystic disease

Diffuse cysts and adenomas, increase risk of RCC (usually papillary), incidence increases with duration of ESRD

Characteristic features of Simple cysts

Single or multiple cysts (rest of K N), very common with increasing age

Characteristic features of Sporadic glomerulocystic kidney disease

Large kidneys w/ predominantly glomerular cysts, associated with biliary dysgenesis (10%)

What is the genetic abnormality associated with AR PCKD?

PKHD1 gene on chromosome 6 - protein fibrocystin (aka polyductin)

What is the usual presentation of AR PCKD

Usually perinatally - most severe forms earliest in life, milder forms later in childhood
- 50% affected newborns die within first few days of life (perinatal type): large abdo masses make delivery difficult, oligohydramnios - pulm hypoplasia + potters, uremia & resp failure
- Earlier presentation = more severe disease
- All pts have varying degrees of congenital hepatic fibrosis (younger presentation = better liver disease)
- kids that present later in life develop renal failure & HTN more slowly (Juvenile type) - have more liver issues

What does AR PCKD look like on U/S

Early - BL enlarged kidneys, hyperechoic cortex, reniform, peripheral sonolucent rim (compressed cortex), macrocysts rate
Later manifestations - presence of discrete cysts w/ increasing age of presentation - usually < 1cm
Non-renal findings: Hepatomegaly, splenomegaly, congenital hepatic fibrosis, biliary dysgenesis

What does AR PCKD look like on IVP?

functioning kidneys w/ characteristic radial or medullary streaking ("sunburst" pattern) - caused by dilated collectin gtubules filled with contrast medium, may be present up to 48 hrs later
- calyces, renal pelvis and ureter are usually not visible, may or may not show functionning kidneys

What is the management of AR PCKD

Genetic counselling (all siblings 1/4 chance)
Early respiratory care
Those that survive need treatment for HTN, CHR, renal failure & liver failure (portal HTN, esophageal varices, hemodialysis, etc.)

What is Caroli's disease?

AR PCKD that presents with large echogenic cystic kidneys with slower deterioration of renal function
Live long enough to develop hepatic & Pancreatic cystic disease

What is the genetic abnormality associated with AD PCKD

AD inheritance with 100% penetrance
Genetic imprinting (worse if from mom) and genetic anticipation (earlier presentation in kids)
- 90% involve chromosome 16 (PKD1) - polycystin-1
- 10% involve chromosome 4 (PKD2) - polycystin-2 (usually milder form with later presentation)
- <1% involves abnormality in PKD3 - unknown gene

What is the usual presentation of AD PCKD?

Most present between 30-50 yo, earlier presentation = more severe disease; 50% that manifest in utero or in infancy have macrocysts
- Usually presents with flank pain, GI symptoms, HTN (50%), proteinuria, hematuria (50%), stones (20-30%), etc
Usually BL presentation
Renal failure seldome before age 40
10x more common than AR PCKD
Large cystic kidneys that are sometimes asymmetrical - cysts derived from entire nephron
Usually don't have any hepatic fibrosis but can get liver cysts

List anomalies associated with AD PCKD

Be DA Real MVP with 8 aCysts
Berry aneurysms - circle of willis
Diverticulitis
Aortic arch aneurysms
Renal artery aneurysms
MV Prolapse
cysts of kidney, liver, lung, spleen, pancreas, pineal gland, arachnoid, SVs
NOT associated with increased risk of RCC
- however when present more likely BL, multicentric and sarcomatoid variant

What is histopath of renal cysts found in AD PCKD?

Diffuse macrocysts from few mm to cms - only 1% of nephrons develop cysts. Found throughout cortex and medulla
Epithelial hyperplasia of cyst lining with hyperplastic polys (similar to VHL, TS, ARCD)

How is diagnosis of AD PCKD made?

Look for family Hx - renal cysts, HTN, strokes
If no Hx - presumptive dx made if BL renal cysts and >2 of the following:
- BL renal enlargement
- >3 hepatic cysts
- Cerebral artery aneurysms
- Solitary cyst of the arachnoid, pineal gland, pancreas or spleen

What does AD PCKD look like on imaging?

IVP - BL enlarged kidneys + stretched calyces, bubble or swiss cheese appearance in nephrogram phase, may resemble AR PCKD (sunburst)
CT and MRI - better than U/S, CT may show enlarged kidney with macrocysts +/- hemorrhage & calcifications, MRI good for those with renal insufficiency

Renal complications of AD PCKD

Renal failure
Stones
HTN
Flank pain
Pyelonephritis
Perinephric abscesses
Hematuria

What are the RF for progression of AD PCKD to ESRD?

M gender
Early age at presentation
PKD1 gene (Chromosome 16)
HTN
Blacks
Presence of gross hematuria

Management of AD PCKD

1) Genetic counselling
2) BP control - HTN more common in males; 60% of those w/o insufficiency have HTN
3) Renal insufficiency - 2% chance of renal failure by age 40, 25% by 50, and 50% by age 73., rate of renal deterioration correlates with cyst growth, tx with Tx or dialysis
4) Pain control
- 50-70% will have loin or back pain from stones, infections, hemorrhage etc
- Percutaneous aspiration + instillation of sclerosant
- Laparoscopic unroofing of cysts (Rovsing's procedure) - doesn't worsen Fn
- Nx
5) Tx of infections - more common in women

Differentiate between juvenile nephronophthisis and medullary cystic disease complex

JN
- AR inheritance (Chromosome 2): NPH1, NPH2, NPH3
- Incidence 1/50,000 births
- ESRD by early teens
- Medullary cysts: AFTER renal failure (40%)
- Tubular BM: Thickened
- Symptoms: polyuria, polydipsia, anemia, growth retardation. Onset after age 2. No HTN, salt-wasting nephropathy
MCDC
- AD inheritance (unknown Chr): MCKD1, MCKD2
- Incidence 1/100,000 births
- ESRD by 20-40s
- Medullary cysts: May develop before onset of renal failure (85%)
- Tubular BM - may not be thickened
- Symptoms: Polyuria, polydispia, anemia +/- hematuria and proteinuria. Onset after fully grown. HTN, no salt-wasting

3 types of juvenile nephronophthisis?

1) Juvenile (NPH1 gene)
2) Adolescent (NPH2 gene)
3) Infantile (NPH3 gene)

What are some anomalies that are associated with juvenile nephronophthisis?

Retinitis pigmentosa (16%) - if both present: Senior-Loken syndrome
Skeletal AbNs
hepatic fibrosis
Bardet-Biedl syndrome - obesity, MR, polydactyly, retinitis pigmentosa, hypogenitalism

How do juvenile nephronophthisis & medullary cystic disease complex appear on IVP?

Early - N or shrunken kidney - homogenous streaking of medullar (retention of contrast w/in dilated tubules)
Late - no value
No calcifications

How do juvenile nephronophthisis and Medullary cystic disease complex appear on U/S?

Parenchyma looks hyperechogenic due to tubulointerstitial fibrosis
Kidney is N size early on then develops tubulointerstitial nephritis and atrophy starts resulting in small kidney with granular surface
Cysts may be seen at corticomedullary junction if large enough

What is the management of juvenile nephronophthisis & medullary cystic disease complex?

Early Na replacement (for JV especially)
Supportive therapy for renal failure until dialysis or renal Tx - no recurrence after Tx

What is congenital nephrosis

condition associated with microcysts
- dilatation of PCTs
- profound proteinuria

What are the 2 main types of congenital nephrosis

1) Finnish type (CNF) - more common
- AR inheritance (Chr 19); assoc with enormously enlarged & edematous placenta (25% of birth weight)
- Presents early after birth
- Profound proteinuria - renal failure at birth - edema and starvation from protein loss, proliferation of mesangial cells on histology
2) Diffuse mesangial sclerosis (DMS)
- sporadic or famililal, may be related to gene NPHS1 (encodes nephrin)
- N placenta
- Also get proteinuria (renal failure by age 3)
- Acid-Schiff +ve and silver phosphate-staining mesangial fibrils on histology
- Insterstitial fibrosis present and more pronounced

What other condition is Diffuse Mesangial Sclerosis congenital nephrosis associated with?

Denys-Drash syndrome (nephrotic syndrome + Wilms +/- male pseudohermaphroditism) - the nephropathy is actually DMS

How is the diagnosis of congenital nephrosis made?

Prenatally - amniotic fluid - CNF type can be diagnosed by elevated amniotic AFP (from fetal proteinuria) as early as 6 wks gestation
Postnatally - U/S - shows enlarged kidneys that are more echogenic than liver or spleen, pyramids are small and hazy with absent CM junction

What is the management of congenital nephrosis?

Dialysis and renal Tx - no recurrence, not responsive to steroids

What is famillial hypoplastic glomerulocystic kidney disease (Cortical microcystic disease)?

AD inheritance
Diagnosis requires 4 features:
- Stable or progressive chronic renal failure
- Small or N sized kidneys with irregular calyceal outlines and AbN papillae
- Present in 2 generations of a family
- Histologic evidence of glomerular cysts - thin-walled and usually subcapsular
May find marked prognathism in some patients

List common multiple malformation syndromes associated with renal cysts

AD inheritance
- TS - variable size, eosinophilic, hyperplastic lining
- VHL - variable size with hyperplastic lining
AR inheritance
- Meckel's syndrome - large cysts with fibromuscular collars probably arising fromcollecting ducts (microcephaly, polydactyly, posterior encephalocele)
- Jeune's asphyxiating thoracic dystrophy - cysts range from subcasular cortical microcysts to dysplasia with cystic components (similar to AD PCKD), small chest and respiratory failure, + renal dysplasia
- Zellweger's cerebrohepatorenal syndrome: cysts vary from glomerular microcysts to 1 cm cortical. hypotonia, high forehead, hepatomegaly
- Ivemark's syndrome - renal-hepatic-pancreatic dysplasia
X-linked disorders:
- Orofaciodigital syndrome - cysts develop with age - hypertrophic lingular & buccal frenula, cleft lip/palate/tongue
Chromosomal disorders (microscopic cysts)
- Trisomy 13 (Patau's), 18 (Edward's), 21 (Down's)

What is Tuberous Sclerosis Complex?

AD with variable penetrance
- TSC1 (Chr 9) encodes hamartin
- TSC2 (Chr 16) encodes tuberin - may have overlap with AD PCKD (PKD1 gene on chr 16)
- Triad - Epilepsy + MR + Adenoma sebaceum
- Hallmark lesion of CNS is cortical hamartoma of serebrum & calcified periventricular subependymal nodules
- Kidneys have cysts, AMLs or both
Rx - MR head + serial imaging of kidneys to assess AMLs

List common features of Tuberous Sclerosis Complex

MR
renal cysts
AMLs
RCC
Pheochromocytomas
Epilepsy
Cortical tubers
Retinal hamartomas
Subependymal nodules
Skin ademona sebaceum (facial angiofibromas)
Ungal or subungal fibromas
Ash leaf spots (white spots)
Shagreen patches
Bone cysts
Lung Lymphangioleiomyomatosis (exclusively females)
Cardaic rhabdomyomas

What is VHL disease?

Cysts of variable size, often multiple and BL with hyperplastic lining
Type 1 VHL (RCC no Pheo) and type 2 (RCC + pheo)
AD Inheritance - chromosome 3p25
- VHL protein inactivates HIF (regulator for VEGF, PDGF)
- lack of VHL = lack of HIF-1 downregulation
Manifestations: (organs that tubularize by day 21) - RCC, Renal cysts, Benign retinal angiomas, benign CNS hemangioblastomas, Pheos, Pancreatic cysts, Pancreatic neuroendocrine tumours, epididymal cystadenomas, endolymphatic sac tumours
Rx - screening CT q1-2 yrs recommended, neuro Sx and optho consults, partial and rad nx for RCCs, screen family with + genetics (retinal exams and abdo CTs)

What are the NIH recommendations for VHL?

Annual P/E and eye check starting as infant
Periodic hearing test starting as infant
Urinary catecholamines at 2 yrs old then q 1-2 yrs
MRI of CNS q2yrs starting at age 11
Abdo/pelvis U/S annually starting at age 11 - CT q6/12 if cysts or tumours develop

What is a multicystic dysplastic kidney?

Non-reniform structure with multiple fluid-filled cysts, "bunch of grapes" - minimal to no parenchyma
Highly variable renal size (slightly less to N to enormous)
Usually N position (can be ectopic)
No calyceal drainage cystem
No the end result - active apoptosis and nephrogenesis
Involution occurs antenatally or postnatally
If contralateral renal dysplasia - incompatible with life

What is the epidemiology of MCDK?

Most common cause (single entity) of abdominal mass in infants
Most common type of renal cystic disease
More cmmon on L side
F more likely to have bilateral MCDK (usually assoc with chr abN, more severe, potter's facies)

What are the 3 forms of MCDK?

Classic type (large cysts with little stroma)->Most common
Hydronephrotic type (identifiable renal pelvis)
Solid cystic dysplastic kidney - Mostly stroma with fewer smaller cysts

Theories behind cause of MCDK

Obstruction
AbN union of ureteric bud and metanephriic blastema

What are the histologic findings of MCDK?

Cysts lined with low cuboidal epithelium
Cysts separated by thin fibrous septa and primitive dysplastic elements (primitive ducts)
Often see immature glomeruli - rarely mature gloms

Differentiating MCDK from UPJO

MCDK
- Non-reniform shape, random distribution of cysts of various sizes
- No large central cyst
- No visible communication b/w cysts
- Very small cysts present between cysts
- absent or small renal artery, no fn on DMSA
- May have hemitrigone or assymetrical trigone
UPJO
- Reniform
- "cysts"/calyces found at peripheray - similar sizes
- Large central "cyst" (pelvis)
- Communication between cysts
- Function on DMSA, N renal artery, N cysto

What is the workup for suspected MCDK?

U/S - confirm normal contralateal kidney, R/O hydro
VCUG - R/O contralateral VUR (routine is controversial)
DMSA - no functionl renal tissue on DMSA

Management of MCDK?

1) Assessment of contralateral kidney is essential (U/S +/- VCUG)
2) No role for prophylactic removal (no increased risk of wilms' tumour, no increased risk for HTN)
3) F/U imaging of MCDK is controversial (how long do we follow? image?)

What are indications to remove a MCDK?

Mass effect (compromising feeding or breathing)
Chronic infection
Causal HTN
worrisome features for Wilms'

What is the spectrum of multilocular cystic lesions in kids?

There is no evidence that one lesion can convert to another - prognosis is better even with malignant lesions
Benign multilocular cyst ->multilocular cystic partially differentiated Wilms'->Multilocular cyst w/ nodules of wilms'-->cystic wilms tumour

What is a benign multilocular cyst?

Benign, nondysplastic, neoplstic lesion
Dx can only be made after surgical excision

How do benign multilocular cysts of the kidney usually present?

Bimodal presentation:
- Before age 4 - 2x more likely to be M, often asymptomatic
- After 30 yrs of age - 8x more likely to be F, often symptomatic (flank pain, hematuria, flank mass)
Unilateral

What is the role of imaging for benign multilocular cysts of the kidney?

U/S and CT can distinguish MCDK from benign multilocular cyst
- however neither study can reliably differentiate it from multilocular cysts w/ nodules or wilms or adnocarciona, mesoblastic nephroma, cystic wilms or clear cell sarcoma

What is the mamagement of benign multilocular cyst?

Nephrectomy - partial if well circumscribed & well-preserved normal tissue (more likely in adults); radical Nx otherwise (esp if suspicious for multilocular cyst with nodules of Wilms or cystic Wilms
Chemo - if confirmed multilocular cyst w/ nodules of wilms or cystic wilms - better prognosis than usualy wilms/

What is Perlmann's syndrome?

Benign multilocular cystic lesion in adults.

What are simple cysts?

oval to round lesions with smooth outline - not connected to nephron - bordered by single layer of flattened cuboidal epithelium
Rare in fetus, most resolve by birth. Uncommon in kids but incidence increases with age
Often incidental

What are the histopathologic features of simple renal cysts?

variable size (most < 2cm)
Fibrous wall of varying thickness (no renal elements)
Cyst lined by single layer of flattened cuboidal epithelium

What is the imaging modalities used to assess simple renal cysts?

U/S - best for simple cysts
If any abN features - perform CT or MRI
If cysts are diffuse, multiple or bilateral - R/O AD PCKD

U/S features to diagnose a simple cyst?

1) sharply defined thin distinct smooth wall
2) spherical or ovoid shape
3) good transmission of sound waves through cyst + acoustic enhancement behind cyst
4) No internal echoes

CT features used to make diagnosis of simple cyst?

1) sharp thin distinct smooth walls and margins
2) Spherical or ovoid shape
3) homogenous content
4) HU < 20

Bosniak classification

Bosniak I - simple cyst
Bosniak 2 - simple cyst + few thin septations, minimal calcification or hyperdense (<3cm); no Rx, risk of malig = 15%
Bosniak 2F - Thicker/more nodular cyst wall + minimal "perceived" septal enhancement, hyperdense cysts > 3cm; No Rx but follow
Bosniak 3 - thick cyst wall, prominent septations, calcifcations, wall enhanceent. Rx = Sx, 50% chance of malignancy
Bosniak 4 - irregular margins + SOLID vascular enhancing elements, Rx = Sx. 85% risk of malignancy

Management of simple cyst

left alone
Sx indicated if pain, HTN, obstruction, infection
- Perc aspiration
- Perc aspiration + injection of sclerosant
- Intrarenal marsupialization
- Lap unroofing of cysts

What are indications for cyst puncture?

1) Suspected infection
2) Low level echoes on U/S but classic cyst on CT
3) Borderline lesion in poor surgical candidate

What variations of simple cysts exist?

1) Unilateral renal cystic disease
- simple cysts of varying size found side by side - large
- often more numerous at one pole, variation of simple cysts, rare - more likely to be unilateral asymmetric AD PCKD
Rx - long-term f/u to r/o development of cysts in other kidney, need to R/O AD PCKD, VHL, TS
2) Autosomal dominant simple cyst disease
- familial syndrome of simple cysts
- No evidence of AD PCKD, VHL, TS, etc.

What is MSK?

Dilatation of distal collecting ducts + small renal cysts (medullary) + diverticula
- cysts lined by urothelium
- dilated ducts have appearance of bristles on a brush
Can also have ectatic ducts that are filled with calcifications=>medullary nephrocalcinosis, "bouquet of flowers" appearance
Non-heritable condition
75% bilateral
More common in stone formers - especially F stone formers
Also more common in F with UTIs

List anomalies that are associated with MSK ("BECH")

Beckwith-Wiedemann Syndrome
Ehlers-Danlos syndrome
Caroli's disease
Hemihypertrophy

What is Beckwith-Wiedemann syndrome?

Most cases are sporadic but 15% are genetic (AD inheritance)
Features include macroglossia, hemihypertrophy, organomegaly, adrenal Ca, Wilms' tumour, medullary renal cysts, hypoglycemia from pancreatic beta cell hyperplasia, MSK

How does MSK usually present?

Many asymptomatic
Renal colic (50%)
Hypercalciuria (30-50%) - most common metabolic derangement
UTIs
Gross hematuria
Hypocitraturia
Impaired concentrating ability

What are the causes of CORTICAL nephrocalcinosis?

Cortical necrosis (acute)
Oxalosis (primary)
Rejection (chronic)
Toxins (ethylene glycol, etc)
Insufficiency of pyridoxine (B6)
Chronic GN
Alport's syndrome
sickLe cell disease

What are the causes of MEDULLARY nephrocalcinosis?

Type 1 distal RTA (2nd most common)
MSK (common)
Sarcoidosis, renal TB
Excess vitamin D
Renal papillary necrosis
Dent's disease
Paget's disease
Hypercalcemia (primary hyperPTH, immobilization, malignancy, hyperT4, pheochromocytoma, milk-alkali syndrome, Vitamin A, Vitamin D, steroids, HCTZ, Li, Ecstasy)

What are the IVP findings suggestive of MSK?

1) Enlarged kidneys + medullary nephrocalcinosis (bouquet of flowers, bristles on a brush)
2) Elongated papillary tubules with puddling of contrast
3) Papillary contrast blush + persistent medullary opacification

What is the management of MSK?

Treatment of complications of MSK (stones - CaOx most common), UTIs (more common in stone formers)
Thiazides (if stones or hypercalciuria), inorganic phosphates (if thiazides not effective,m avoid in patients with UTIs - risk of struvite stones)
consider prophylatic Abx for those with recurrent UTIs
SWL and PNL for stones

What is sporadic glomerulocystic kidney disease?

Cysts of the glomeruli or Bowman's space that are present diffusely and bilaterally
Dx only if
1) Non-heritable condition (no family members)
2) Bilaterally enlarged kidneys with small cysts, mainly of bowman's space
3) No associated anomalies
- may be hard to differentiate from AD PCKD - could be a new variant of classic AD PCKD
- different from familial hypoplastic glomerulocystic kidney diseaes (AD inheritance, small or N sized kidneys)

What conditions are associated with glomerular cysts?

Familial hypoplastic glomerulocystic disease
Sporadic glomerulocystic kidney disease
AD PCKD
Juvenile nephronphthisis with hepatic fibrosis
Multiple malformation syndromes (Zellweger's syndrome, Trisomy 13 (Patau's), Meckel's syndrome, TS, orofaciodigital syndrome type 1, short-rib polydactyly (Majewski type))

What is acquired renal cystic diseae?

cystic diseaes that develops in ESRD - not only assoc with hemodialysis, incidence increases with time, more common in ESRD from nephrosclerosis (HTN)
- Dx made once at least 3-5 cysts seen on imaging, can develop adenomas
- 7x more in M and more advanced, more in blacks & japanese
- May cause pain & hematuria & infection
- Associated with Increased risk of RCC (usually pap)

What is different about RCC associated with ARCD?

Approximately 5x more common (10x in blacks) than general population
Age at occurence is 5 yrs younger of general pop
Even more common in M (7x vs 2x in gen pop)
Usually multiple & bilateral - if RCC doesn't develop after ~10 years, likely won't develop

What is the cause of ARCD?

Several theories:
1) Uremic toxins - lesions are multiple and BL, regression of cysts seen after renal Tx, return of cysts after failed Tx and resumption of dialysis
2) Loss of functioning renal tissue leads to production of renotrophic agents that induce tumours

How does ARCD usually present?

Most common - flank pain + hematuria
Bleeding seen in 50% - urine or retroperitoneum
Polycythemia - may have increased epo production

What are the histologic findings of ARCD?

Cysts are mainly in cortex - microcysts
Cysts are usually 0.5-1.0 cm
Can be filled with Ca Oxalate cyrstals
Most cysts are lined by flat epithelium - can see hyperplastic lining in some cysts - explains RCC
Adenomas

What othe types of cysts are associated with hyperplastic lining?

ARCD - increased risk of RCC
VHL renal cysts - increased risk of RCC
TS renal cyts - likely increased risk of RCC
AD PCKD - no increased risk of RCC

What is the best imaging modality to assess ARCD?

CT or MRI - better than U/S

What is the managmenet of ARCD?

Treatment
- embolization or Nx if symptomatic
- percutaneous draininage of infected cysts - Nx if not effective
- Radical Nx if evidence of RCC
Screening
- Routine screening recommended if risk factors - prolonged dialysis, M gender
- Cysts may resolve w/ renal Tx but risk of RCC does not seem to decrease after Tx

What is a calyceal Diverticulum?

Pyelogenic cyst
- Smooth outlined intrarenal sac that communicates with the pelvicalyceal system by a narrow neck
- Lined by transitional epithelium

What is the difference between parapelvic cysts & renal sinus cysts?

Parapelvic cyst - cyst arising from renal parenchyma that happens to abut renal pelvis
Renal sinus cyst - derived from arteries, lymphatics or fat within renal sinus (NOT kidney)

What is a renal sinus cyst?

Derived from tissue within - lymphatic origin is most common
- Usually multiple & bilateral - can have polycystic disease of the renal sinus - multiple renal sinus cysts, stretching of infundibula and medial displacement of pelvis
- Most appear after 5th decade
- May be associated with inflammation, obstruction or a stones

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