S. Thiyagarajan

3 overlapping renal systems are formed

in a cranial to caudal sequence during

intra uterine life in humans:

1. Pronephros

2. Mesonephros

3. Metanephros

PRONEPHROS

7- 10 solid cell groups in the cervical region at the beginning of the 4th week

These forms vestigeal excretory units, nephrotomes, that regress as caudal ones form

Completely disappears by end of week 4

MESONEPHROS

Derived from

intermediate mesoderm

from upper thoracic to

upper lumbar

segments, during

regression of pronephric

nephrotomes

Excretory tubules

develop in the

mesonephros which

open laterally into a duct

called Mesonephric or

Wolffian duct

METANEPHROS

Appear in the 5th

week

Forms the

permanent kidneys

The metanephros

develops in the

lower lumbar and

sacral regions

Excretory

units appear

in the

metanephros

The ureteric bud

(mesonephric

diverticulum) is an

outgrowth from the

mesonephric duct

close to its

entrance to the

cloacae

• It grows into the metanephros, dilating

to form the pelvis of the ureter

• Further divisions of the ureteric bud

give rise to the major and minor calyces

and collecting tubules (1 to 3 million)

Parts of the Kidney

Cortex

Medulla

KIDNEY

Renal sinus

Space within the

kidney that is

occupied by

renal pelvis,

calices, vessels,

nerves and fat.

Cortex

outer zone of the kidney

(approximately one third of its

depth)

Consist of

Glomerulous,

Proximal Convoluted Tubule,

Distal Convoluted Tubule.

Medulla

Inner zone of the kidney (approximately

two third of its depth)

consist of

o Pyramids, which consist

descending loop,

ascending loop,

& collecting tubule.

o Renal columns

Papillae and calices

The anatomy of the

collecting system is

variable.

The normal papilla is

usually seen as a

conical convexity

indenting the calyx

with sharply defined

fornices on either

side.

The superior end of the

ureter expands to form

the renal pelvis which

divides in 2-4 major

calyces, each of which

divide into 2-4 minor

calyces.

The minor calyces

drain into a major

calyx via a neck,

called infundibulum.

The infundibula may

be long or short.

Occasionally calices

arise directly from

the pelvis.

Normal interpapillary line

Drawing illustrates

how the renal

outline should be

closely paralleled by

a line connecting the

papillary tips (dotted

line).

Deviations from this

pattern require

explanation

The shape of the papillae varies widely

from patient to patient.

the variations tend to be symmetrical

and associated with other natural

variation in the kidney.

Fetal lobulations

Kidneys are

scalloped

appearance.

The number of lobe

depends on the

overall calyceal

number.

Lobes represents a

vestige of lobar

development of

kidney, which is

visible at birth.

With cellular

multiplication, lobar

anatomy is usually

obscured by the age

of 2 years.

Fetal lobulation of

kidney can mimic,

Tumor,

Pyelonephritic

scar,( reflux

nephropathy)

Multiple renal

infarcts. (when

interlobar vessels

are involved)

But these conditions can be easily ruled out.

In fetal lobulation ,

• parenchymal thickness should be normal (approx 1 cm).

• calyces are centered between indentation.

Normal “increased” parenchymal thickness

Nephrotomogram

shows prominent

cortical tissue

(arrowheads), a

finding that can also

reflect normal fetal

renal anatomy.

Typical areas of

prominence include

the hilar lips, cortical

columns (usually

seen at the junction

of the upper and

middle thirds of the

kidney), and other

“humps” that should

be reflected in the

interpapillary line

Suprahilar bump

Compound calices

Two or more

papillae may enter in

one major calyx.

Urographic image

shows the proximal

right ureter with a

“reversed J”

appearance, a

finding that is

characteristic of

circumcaval ureter

Circumcaval ureter

Flat or small papillae

confused with other causes of blunt

calices such as post-obstructive

atrophy.

The symmetry observed in normal

patients.

Megacalices

developmental

abnormality.

calices appear

uniformly „dilated‟.

Due to

underdevelopment

of the papillae.

Large papillae

much larger than usual.

symmetry is observed.

Simple papillae Mega papillae

Papillary blush

papillae show a homogeneous blush

due to well concentrated contrast

medium in the collecting tubules.

particularly prominent when low-

osmolality contrast media are used.

no clinical significance.

Papillary blush...

Early Urographic image shows prominent papillary opacity but no resolvable tubular structures in the region of the papillae.

Ten-minute image obtained with compression shows a decrease in the prominence of the papillary opacity, a finding that is typical of papillary blush.

Disappearing calyces

The number of calyces demonstrated on

EU may change from study to study in

the same patient.

Different calyces may be visualized on

sequential studies.

This is duo to contraction of smooth

muscle around the calyces may keep

contrast from entering and opacifying

them.

Duplex kidney

Minor degrees of

duplication are

extremely common.

Bifid renal pelvis

seen in about 10%

of the population.

Column of Bertin

Partial duplication

may be associated

with hypertrophy of

the septal cortex

(hypertrophied

column of Bertin).

Typically in upper or

mid polar region.

Diagnosis is made

by identify the

anomalous calyx on

EU, normal renal

cortex on nuclear

scintigraphy or

normally echogenic

renal cortex

extending in renal

sinus in the USG.

Vascular impressions

The renal vessels

run close to the

pelvis and major

calices in the renal

sinus and may

cause indentations

which can be

mistaken for

intraluminal filling

defects.

Such „filling defects‟

are most obvious

when the collecting

system is relatively

empty and usually

become less

obvious or even

vanish during

effective ureteric

compression.

Box shaped pelvis

Normal one is

delicate funnel

shaped pelvis.

Box shaped

extrarenal pelvis is

normal variation.

Bilobed calyx

Bilobed or cleft

lower pole calyx.

Cut-off calyx