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270 Cards in this Set

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If a congenital GU anatomic abnormality is present, what is the chance of a coexistant abnormality?
75%
What does the urinary tract develop from?
Nephrogenic cord. The structures develop from it chronologically in a craniocaudal sequence
How many sets of primitive excretory structures are there?
3
What are they?
Pronephros


Mesonephros



Metanephros
What does the pronephros become in the adult?
Nothing. Totally regresses.
So is a pronephros needed by the embryo?
YES
For what?
Induction of the next major phase of renal development.
Which is what?
Differentiation of the mesonephros into the mesonephric duct.
What is the other name for the mesonephric duct?
Wolffian duct
What does the mesonephric duct become in the adult?
In male, becomes ducts of testes, epididymis, and vas deferens
How many cell lines does the metanephros come from?
Two separate cell lines
What are these cell lines?
Ureteric bud


Metanephric blastema
Where does the ureteric bud come from?
It is an outgrowth of the mesonephric duct
What does the ureteric bud become?
The collecting system, proximal to the bladder.
Meaning?
Ureter


Renal pelvis


Renal calyces


Medullary collecting tubules
What does the metanephric blastema develop from?
The caudal part of the nephrogenic cord
What does it develop into?
The excretory portion of the kidney
What does the metanephric blastema need?
To be induced
By what?
The ureteric bud
How?
They must come into contact with each other for induction to occur
What does the ureteric bud do when it contacts the metanephric blastema?
Digs into it (renal pelvis) and starts dichotomously branching (calyces, etc)
What does induction of the metanephric blastema result in?
Formation of glomeruli, loops of Henle, etc
What is the dominant force in renal development (i.e. how the kidneys will appear)?
The ureteric bud
What does its branching pattern define?
A renal lobe
What is a renal lobe
Single funtional unit of kidney
What does it consist of?
Calyx, collecting ducts leading to it, and overlying renal cortex
About how many lobes in each kidney?
14
When is renal maturation complete?
Age 5
What is going on during these 5 years?
Cortical growth.
What does this do?
Eventually obscures the lobular appearance of the renal surface.


After maturation is complete, no new glomeruli can be formed, although hypertrophy of those already there can take place.
What occurs in 5% of patients?
Persistence of the gross fetal lobular appearance of the kidney.
What does this represent?
An anomaly of cortical maturation
Until what age can renal tissue hypertrophy?
Age 60.
Can renal hypertrophy be asymmetric?
Yes
What is this called?
Renal pseudotumor
Where is it most commonly seen?
In patients with focal atrophy due to reflux, making the hypertrophied areas even more prominent
What happens to the kidney during the 4th to 8th weeks of embryogenesis?
Kidney rises from sacrum to midabdomen
How?
Doesnt actually move.
What else happens during this period?
renal hilum rotates from anterior to medial
How does the blood supply work?
Initially supplied by sacral branches of aorta, but as renal "ascent" occurs, the kidneys become supplied by successively higher and higher branches, until they are served by the adult renal arteries
Where are the adult renal arteries?
L2
What can happen anomalously w/r/t vascular supply?
Persistence of inferior vessels supplying kidney, due to failure of regression of the primitive vessels. Results in anomalous inferior vessels.
How common is this?
Common
What is the incidence of this in pelvic and horseshoe kidney?
Almost 100%
What is the classification of congenital renal anomalies?
Can involve anomalies of:

1) Number


2) Position



3) Fusion


4) Structure


5) Vasculature


6) UPJ obstruction
What are anomalies of renal number?
Renal agenesis

Supernumary kidney
What is cause of renal agenesis?
Failure of ureteric bud to form or reach metanephric blastema
What happens to the ipsilateral ureter?
May be absent, or may be blind ending stump coming off of the UVJ
What associated anomalies are common?
Depends if male or female
What if patient is male?
20% with absence of ipsilateral epididymis, vas deferens, or seminal vesicle
What if patient is female? What percent have associated abnormality?
70%!
What abnormalities?
Absence or atresia of uterus or vagina


Unicornuate uterus, with absence of that ovary and absence or atresia of vagina



Duplication abnormalities of genital tract
What syndrome are these anomalies part of?
Rokitansky-Meyer-Kuster-Hauser
What other abnormality is common in renal agenesis?
Ipsilateral adrenal agenesis
In what percentage?
10%
What is incidence of renal agenesis?
1 in 1000 live births
Male vs female?
75% male
Does bilateral renal agenesis occur?
Yes
What is incidence of that?
1 in 3000 live births
What does it result in?
Oligohydramnios
What does that result in?
Pulmonary hypoplasia


Facial anomalies
What is this called?
Potter's syndrome
What are the anomalies of position?
Rotational abnormalities


Renal ectopia
What is the rotational abnormality?
Nonrotation, with UPJ pointed anteriorly
What is renal ectopia?
Exaggeration or arrest of normal caudal to cranial renal ascent.
What other renal anomalies is ectopia usually associated with?
Vascular anomalies (usually supplied by vessels at level where stuck)


Fusion
How frequent are pelvic kidneys?
1 in 1000
What are they associated with?
Increased incidence of UPJ obstruction, VUR, functional abnormalities, and stone formation.
What should be expected of pelvic kidneys?
Expect that they will not have normal appearance of kidney on imaging.
How common is overascent?
Very uncommon.
Where is it?
Nearly always subdiaphragmatic, even though it may eventrate diaphragm, appearing to be in the chest.
What variant of pelvic kidney can occur?
If both are involved, will have a lump kidney, where both kidneys are just lumped together as a mass.
What is the most frequent renal anomaly?
Horseshoe kidney
What are the anomalies of fusion?
Horseshoe kidney



Crossed fused ectopia
What is the midline connection between the kidneys formed by?
Fibrous band or isthmus of functional tissue
Where are the kidneys fused?
Lower poles
Where is the horseshoe kidney?
Lower abdomen, NOT pelvis
Why?
The midline band gets hooked on the origin of the IMA
What is horseshoe kidney associated with?
Increased incidence of UPJ obstruction, stone formation, and UTI.
What is crossed fused ectopia?
One kidney crosses the midline to fuse with the opposite kidney
Where do the ureters insert?
Normally
What can the kidneys look like?
Vary in fusion from normal appearing kidneys all the way to lump kidney
Does one kidney cross the midline more frequently?
Yes
Which?
Left
What are the symptoms?
None, but increased risk of same things as horseshoe
How common are supernumary renal arteries?
Very. >25%
How common are supernumary veins?
Also common, but only about 1/2 as common as arterial.
What is true of left sided supernumary veins?
Retroaortic
In what cases is there nearly 100% incidence of anomalous vascularity?
Ectopic kidneys, including horseshoe.
When are these anomalies important?
Presurgical evaluation
What happens when there is ligation of one of the anomalous vessels?
Infarction, as all renal arterial vessels are end arteries.
What is a symptomatic effect of renal segmental infarction?
Hypertension
When is renal vascular analysis especially important?
In the case of UPJ obstruction
Why?
The treatment is endoscopic pyelotomy and pyeloplasty.
So?
If a vessel is compressing the UPJ or simply close to this part of the ureter, when the transmural incision is made, severe hemorrhage can occur.
Where to the vessels usually cross?
Anteriorly
So where is the incision made?
Posterolaterally.
In what percent of patients with accessory renal vessels does the vessel cross posterior to the UPJ?
5%. So besides notifying the urologist about any anomalous vessel, a posteriorly crossing vessel is crucial to notify about.
How is the vasculature best evaluated preoperatively?
CTA or MRA
What are the congenital abnormalities of renal structure?
1) Fetal lobulation



2) Renal tissue masses



3) Congenital cystic disease



4) Mesoblastic nephroma



5) Nephroblastomatosis
When is lobulation of the kidney always present?
At birth
By what age is the lobar anatomy of the kidney obscured?
Age 5
What percent of patients have persistent fetal lobulation?
5%
What is the clinical significance of this?
Nothing
What should the renal parenchymal thickness be in fetal lobulation?
Normal
Which is what?
Greater than or equal to 14mm
What is the key to diagnosing persistent fetal lobulation versus other cause of renal irregularity?
The calyces are centered between the indentations
What are other non-benign causes of renal irregularity?
Reflux nephropathy


Papillary necrosis


Multiple renal infarcts
Which type of renal infarcts?
Interlobar vessel infarcts, caused by small vessel dz such as diabetes
How do you distinguish diabetic changes versus fetal lobulation?
Indentations do occur between the calyces, like with fetal lobulation, but the renal cortical thickess will be diminished due to chronic atrophy
What are renal tissue masses?
Prominent areas of normal renal tissue
What are the entities?
1) Column of Bertin



2) Hilar lips



3) Dromedary hump



4) Duplication anomalies
What is column of Bertin?
Invagination of normal renal cortical tissue into the renal sinus
Where is the column of Bertin?
At junction of the upper and middle thirds of kidney
In what percent is it bilateral?
60%
How can this finding be distinguished from mass?
Using US, enhanced CT or MRI, one can confidently diagnose this "mass" as normal renal tissue
How is it confidently diagnosed?
(a) is located between the overlapping portion of two renal sinus systems

and

(b) contains renal cortex that is continuous with the adjacent renal cortex of the same subkidney.
What are hilar lips?
As they sound, they are collections of renal tissue at the most medial aspect of the kidney, which project into the renal sinus (hilum)
Where is hilar lip most common? Upper or lower pole?
Upper
Which kidney is more frequently involved?
Left
What can hilar lip mimic?
Mass
Why is it called lip?
Just because it looks like a lip on IVU.
How is it confirmed as normal tissue?
Normal echogenicity on US, normal uptake on enhanced CT, etc.
What is a dromedary hump?
An impression on the kidney which causes focal renal contour abnormality
Where is it located?
Upper pole of left kidney, laterally
What is it due to?
Impression by the spleen
When is it an issue?
Only on IVU. Cause is obvious on cross sectional imaging.
What is the most common congenital urinary tract anomaly?
Renal duplication.
In what percent of patients is there some degree of duplication?
10%
What is the cause?
Development of second ureteric bud, or redundant duplication of the single ureteric bud.
What is a duplication abnormality?
Presence of two or more pyelocalyceal elements
What is the spectrum of abnormalities?
Runs from bifid pelvis to two complete drainage systems
What are entities in the middle of the spectrum?
Partially duplicated ureter


Completely duplicated ureter with common insertion into the bladder


Complete duplication with ectopic entry of the upper pole moiety.
What findings go along with duplication?
Renal enlargement


Prominent area of normal renal parenchyma dividing renal sinus and kidney into two separate pyelocalyceal components. This appearance is similar to column of Bertin.
What are the congenital cystic diseases of the kidney?
1) Multicystic dysplastic kidney



2) Autosomal recessive polycystic kidney disease



3) Multilocular cystic nephroma


4) Medullary sponge kidney




5) Calyceal diverticulum
What is the most common cause of abdominal mass at infancy?
Hydronephrosis
What is the second most common cause?
Multicystic dysplaskic kidney
What is the cause of MCDK?
Failure of the ureteric bud to induce the metanephric blastema to produce nephrons
What is prevalence of bilateral MCDK?
Very rare.
What happens in bilateral MCDK?
Incompatible with life
What are the hallmark pathologic features of MCDK?
CYSTS--In place of normal renal tissue, there are simple cysts scattered throughout the parenchyma.


DYSPLASTIC TISSUE--Many ares of metanephric blastema are not induced to mature, and these immature rests undergo dysplasia to other tissue types.
What dysplastic tissue type is a hallmark?
Cartilage
What is renal function?
Usually absent. May have minimal function.
What are the two ends of the MCDK spectrum?
Pelvoinfundibular MCDK


Hydronephrotic MCDK
Which type is more severe (i.e. occurs at an earlier point, with more primitive tissue)
Pelvoinfundibular
What are the features of pelvoinfundibular variety?
Randomly occuring noncommunicating cysts


Where the renal pelvis would be, there is no dominant cyst


NO potential for renal function
Which is the less severe variety?
Hydronephrotic
What can this variety be thought of as?
A severe in utero form of UPJ obstruction
What are the features of hydronephrotic variety?
There is a dominant cyst in the expected region of the renal pelvis. Around this central cyst, there are radially oriented cysts, which may intercommunicate.
How are these cysts arranged?
Like calyces
What is possible in this variety?
Minimal renal function
What is the appearance of the ureter in pelvoinfundibular variety?
Atretic
What about in hydronephrotic variety?
Occluded at the level of the UPJ
What is the key point once a diagnosis of MCDK has been diagnosed?
Evaluating for treatable but potentially dangerous lesions of the contralateral kidney.
What condition is patient with MCDK at increased risk for in the contralateral kidney?
UPJ obstruction
What is the risk of malignancy in MCDK?
No increased risk
What should be done about a MCDK?
Nothing.
What should happen to MCDK over time?
Stay same or get smaller
What are the rare complications of MCDK
Cyst infection

Hypertension
What occurs pathologically in autosomal recessive polycystic kidney disease?
Normal renal parenchyma is replaced by dilated nonfunctional tubular structures
What is an unique feature of ARPCKD?
Hepatic involvement
What is the relationship between renal and hepatic disease?
Inversely related in severity.
What hepatic changes occur?
Periportal fibrosis
What does this result in?
In severe cases, hepatic failure with portal hypertension
What are the varieties of ARPCKD?
Perinatal, neonatal, infantile, and juvenile
What is the most common form?
Perinatal
What occurs in the perinatal variety?
Death in the perinatal period
Why?
More than 90% of normal collecting ducts are replaced by nonfunctional dilated tubules, resulting in oligohydramnios and subsequent pulmonary hypoplasia. They die of pulmonary insufficiency
What is true of hepatic disease in these cases?
Minimal
What percent of collecting tubules are involved in the neonatal variety?
60%
When do these kids present?
In the first month
What do they present with?
Severe renal insufficiency
What is the end result in this disease?
Death within a few months
What is hepatic disease like?
Mild
When do kids with infantile ARPCKD present?
3-6 months
What do they present with?
Renal insufficiency, nephromegaly, and HSM
What is the natural history of this disease?
Death during childhood.
What is the relationship between renal and hepatic disease?
Balanced
What percent of collecting tubules are involved in the juvenile variety?
Less than 10%
When do they present with their disease?
Teenage years
What is the nature of the renal disease in these patients?
Usually normal or only mildly impaired
What is their main problem?
Severe progressive periportal fibrosis, resulting in hepatic insufficiency and portal hypertension.
What do they present with?
GI bleeding or other signs of hepatic failure
What does this result in if untreated?
Death
What do parents know about their carrier status?
Usually do not, since it is transmitted autosomal recessive
When is the diagnosis of perinatal, neonatal, and infantile forms of ARPCKD usually made?
Prenatally
How is it initially suspected usually?
Oligohydramnios
What finding is virtually diagnostic of the disease?
Large echogenic kidneys bilaterally
What is the problem with making the diagnosis?
Normal infants may have mildly hyperechogenic kidneys
How do you separate these kids from ARPCKD patients?
They will also have renal enlargement
What is the characteristic CT appearance for ARPCKD?
Nephromegaly with striated nephrogram
Why striated nephrogram?
Result from normally functioning tubules adjacent to the nonfunctional dilated urine filled tubules
What is characteristically ABSENT in all varieties of ARPCKD?
Macrocysts
What is the pathologic term for medullary sponge kidney?
Benign renal tubular ectasia
What is the cause?
Ectasia of renal collecting tubules
What is the incidence of medullary sponge?
1 in 200
What is unusual about MSK?
May involve as few as one renal pyramid, to diffuse bilateral involvement
In most cases, what is MSK?
Incidental finding
What is the major complication of MSK?
Increased risk of nephrolithiasis
What is typically seen as evidence of medullary sponge kidney?
Medullary nephrocalcinosis
What diseases are associated with MSK?
Hemihypertrophy syndrome, Caroli disease, and Ehlers-Danlos
What occurs in hemihypertrophy?
Enlargement of one entire side of the body
What is hemihypertrophy associated with?
Increased risk of certain malignancies
What malignancies?
Wilms, pheochromocytoma
What is the appearance of MSK on imaging?
1) Focal collections of contrast material in the renal medulla peripheral to the calyx

2) Medullary nephrocalcinosis
When is the diagnosis of MSK given by the radiologist?
When there is history of nephrolithiasis
Otherwise, what are kidneys with this appearance called?
Benign renal tubular ectasia, which is just the pathologic term
What can mimic MSK?
Papillary blush and papillary necrosis
What is the appearance of papillary blush?
Homogeneous opacification of the entire papilla, without focal collection
Where is the papilla?
The area of renal medulla just peripheral to the calyx
What is the appearance of papillary necrosis?
Also see contrast pooling in the renal medulla
What is the difference between these pools and those seen in MSK?
These freely communicate with the calyx, AND the calyx itself is not normal in appearance, due to changes of papillary necrosis
Although you would never do it, how could you confirm whether the changes were due to papillary necrosis or benign tubular ectasia?
Retrograde pyelography
What would you see with benign tubular ectasia?
Nothing abnormal, except maybe medullary nephrocalcinosis
What would you see in papillary necrosis?
Filling of the medullary cavities, due to incompetent renal papillae, injured by papillary necrosis
What is multilocular cystic nephroma?
A rare neoplasm
What is it thought due to?
Defect in a segment of metanephric blastema
What is the age distribution?
Bimodal
When is the first peak?
Boys in first decade of life
What percent occur during this phase?
50%
What is the next peak?
Women in 20s-30s
What is the appearance?
Cystic mass with septations.
What is the finding that is characteristic for MLCN?
Herniation of the mass into the renal pelvis
What findings are characteristically absent?
Calcification, hemorrhage
What is the differential for this lesion?
Cystic Wilms
Cystic RCCa
Segmental multicystic dysplastic kidney
Renal abscess
Rare inflammatory renal diseases
What are these rare inflammatory diseases?
Segmental XGP


Echinococcus



Renal malakoplakia
How is definitive diagnosis made?
At biopsy or surgery
How is management handled differently if MLCN is suspected?
Renal sparing surgery is attempted
What is the cause of calyceal diverticulum?
Failure of a segment of the ureteric bud to induce nephron development in a region of the metanephric blastema
What is the result?
A calyceal diverticulum, which is a cavity lined by transitional epithelium located peripheral to a calyx, which directly drains into the calyx.
What is important to note about its anatomy?
The calyceal diverticulum represents an area of failed nephron development, therefore there are no collecting ducts draining into the diverticulum.
What are the types of calyceal diverticula?
Types I – III
What is the most common
Type I is by far most common
What is a type I?
Diverticulum arises from a minor calyx
What is a type II?
Diverticulum arises slightly more centrally, from the central infundibulum that would drain multiple minor calyces
What is a type III?
Diverticulum communicates directly with the renal pelvis
What is the imaging appearance of calyceal diverticula?
Smooth walled fluid-filled medullary outpouchings that fill with excreted contrast material slightly later than normal calyces
What are the common complications of calyceal diverticula?
Those related to stasis: Calculi and infection
What should calyceal diverticulum be differentiated from?
Hydrocalyx
What is hydrocalyx?
Basically focal hydronephrosis. A calyceal infundibulum becomes strrictured, and there is focal dilatation of the involved calyces.
How are the two differentiated?
Calyceal diverticulum is a smoothly rounded outpouching, while hydrocalyx has a squared-off appearance, as you would expect of a dilated calyx.
What is a mesoblastic nephroma?
A renal hamartoma
What is special about it?
It is the most common renal neoplasm of the NEONATAL period
How is the diagnosis made?
Surgically or by biopsy
Why?
Because it appears as a nondescript solid renal mass, which mimics malignant renal neoplasms, such as Wilms.
When is metanephric blastema tissue supposed to be all gone by?
36 weeks gestation
What happens when a lot remains?
Nephroblastomatosis
What is the pattern of nephroblastomatosis?
Primitive tissue intermingled with normal renal parenchyma
What is the appearance of nephroblastomatosis on enhanced CT?
1) Marked renal enlargement

2) Multiple foci low attenuation foci
Where are the low attenuation foci?
Subcapsular
Why are these lesions hypoattenuating on contrast CT?
They are foci of nonfunctional tissue
What is significant about nephroblastomatosis?
Increased risk of Wilms tumor.
What is the pathology in UPJ obstruction?
Increased collagen deposition in the proximal ureter, resulting in an adynamic segment, producing anatomic and functional obstruction
What are the suspected causes of the stricture resulting in UPJO?
In-utero ischemia


Aberrant crossing vessels


Fibrous bands
What is the main finding in UPJ obstruction?
Hydronephrosis
What occurs in severe cases of UPJ obstruction?
Renal insufficiency and cortical thinning
What is the key in UPJ obstruction?
Early diagnosis
What percent are bilateral?
20%
What conditions are associated with increased risk of UPJO?
Contralateral MDK


Contralateral renal agenesis


Ureteral duplication


VUR
What are the imaging findings?
Main finding = hydronephrosis



May be able to see focal narrowing at UPJ on IVU
What is the characteristic finding of longstanding UPJO?
Dilated renal pelvis with corkscrew upper ureter
What is this appearance called?
Balloon on a string
What is the perinephric space of the retroperitoneum surrounded by?
Gerota’s fascia
What is another fascial compartment within the perinephric space?
The renal capsule
What is located within the perinephric space?
Kidney

Adrenal gland

Renal hilum, including vessels and proximal collecting system
What is connected to Gerota’s fascia?
Multiple radial septae which subdivide the perinephric space
When can these perinephric septae become thickened?
Ureteral obstruction

Renal infection

Renal vein thrombosis

Renal tumors

Retroperitoneal fluid collections
What is the colloquial radiologic term to describe thickening of these radial septae?
Perinephric stranding
What is in the anterior pararenal space?
Pancreas

Retroperitoneal portion of duodenum

Ascending/descending colon
What is the superior extent of the perirenal space?
Bare areas of liver and spleen