Glossary of GU 1 -- Congenital

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If a congenital GU anatomic abnormality is present, what is the chance of a coexistant abnormality?
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?
What are they?


What does the pronephros become in the adult?
Nothing. Totally regresses.
So is a pronephros needed by the embryo?
For what?
Induction of the next major phase of renal development.
Which is what?
Greater than or equal to 14mm
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.

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
Doesnt actually move.
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?
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?
What is this called?
Potter's syndrome
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
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?
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?
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?
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?
What other abnormality is common in renal agenesis?
Ipsilateral adrenal agenesis
In what percentage?
What is incidence of renal agenesis?
1 in 1000 live births
Male vs female?
75% male
Does bilateral renal agenesis occur?
What is incidence of that?
1 in 3000 live births
What does it result in?
What does that result in?
Pulmonary hypoplasia

Facial anomalies
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)

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
Because it appears as a nondescript solid renal mass, which mimics malignant renal neoplasms, such as Wilms.
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?
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?
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?
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?
When is renal vascular analysis especially important?
In the case of UPJ obstruction
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?
So where is the incision made?
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?
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?
What is the clinical significance of this?
What should the renal parenchymal thickness be in fetal lobulation?
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?
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


(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?
Which kidney is more frequently involved?
What can hilar lip mimic?
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?
What is the cause?
Ectasia of renal collecting tubules
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?
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?
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)
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?
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?
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?
What should happen to MCDK over time?
Stay same or get smaller
What are the rare complications of MCDK
Cyst infection

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?
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?
What occurs in the perinatal variety?
Death in the perinatal period
What is true of hepatic disease in these cases?
What percent of collecting tubules are involved in the neonatal variety?
When do these kids present?
In the first month
What do they present with?
GI bleeding or other signs of hepatic failure
What is the end result in this disease?
Death within a few months
What is hepatic disease like?
When do kids with infantile ARPCKD present?
3-6 months
What is the natural history of this disease?
Death during childhood.
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 does this result in if untreated?
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?
How is it initially suspected usually?
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?
What is the pathologic term for medullary sponge kidney?
Benign renal tubular ectasia
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?
When is the first peak?
Boys in first decade of life
What percent occur during this phase?
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


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?
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
When is metanephric blastema tissue supposed to be all gone by?
36 weeks gestation
What happens when a lot remains?
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?

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