Kidney & Bladder

What structures are found in the great vessel space? This space lies anterior to what?

Aorta and IVC

Anterior to vertebral bodies and Psoas M

What structures are found in the posterior pararenal space?

mostly fat, blood vessels, lymphatic

What structures are found in the anterior pararenal space?

head, neck, & body of pancreas

ascending & descending colon

duodenum (except proximal first segment)

What structures are found in the perinephric/perirenal space?

adrenal glands

kidneys

ureters

vessels

How would the Psoas appear sonographically?

Medium level gray, inhomogeneous, bright striations through it.

where will the psoas muscle be located at on a ultrasound scan?

Will see it posterior of the kidney

Space between right kidney & liver; will only see with ascites

Morrison's Pouch

Will we see the ureter on a sonogram scan?

Unless if there is a obstruction, no

The kidneys are _____ (retroperitoneal/intraperitoneal)

retroperitoneal

Describe the innermost capsule (AKA true capsule) of the kidney.

a fibrous layer encased in a layer of perinephric fat

Describe the outermost layer of the kidneys.

Called Gerota's fascia; a fibrous tissue that surrounds kidney, perinephric fat, & adrenal glands

What two things does Gerota's fascia separate?

peri-renal fat from para-renal fat

The kidneys lie at the level of ___-___ vertebrae

T12-L3/4

Area where the renal artery, vein, and ureter exit/enter the kidney

renal hilum

Describe the following structures relative to the kidney:

Adrenals rest on _______ poles

Psoas Major M is ______ and ______

Quadratus Lumborum M is _______ & _______

superior

posterior & medial

posterior & lateral

Kidney Embryology:

What happens to the kidney at about 3 weeks of development?

Kidney development begins with intermediate mesoderm

Kidney Embryology:

What happens to the kidney in the early 4 weeks of development?

Pronephros (forekidney) develops and quickly degenerates, leaving behind a duct

Kidney Embryology:

What happens to the kidney in the late 4 weeks of development?

Mesonephros (midkidney) develops and provides minimal function support as the permanent kidney develops

Kidney Embryology:

What happens to the duct that was left behind after degeneration of the pronephrons in the late 4 weeks of development?

It becomes the mesonephric duct, which will eventually develop into structures of the male (Wolffian duct) or female (Mullerian duct) reproductive system and structures of the urinary system

Kidney Embryology:

What happens to the kidney in week 5 of development?

Metanephros (permanent kidney) begins to develop, incorporating aspects of the mesonephric duct

Kidney Embryology:

What happens to the kidney in week 8 of development?

nephrons begin functioning

Kidney Embryology:

What happens to the kidney throughout the remainder of embryogenesis up until 5-6 years of development?

"migration" of kidneys occurs; from pelvic region to renal fossae

Thin, hyperechoic layer that covers the kidney; may contain perinephric fat

renal capsule

What 3 portions of the kidney make up the renal parenchyma?

cortex, medulla, sinus

Finger-like projection/extension of the renal cortex between the renal pyramids.

columns of Bertin

The outer layer of the kidney that extends to the base of the pyramids and between columns of Bertin

renal cortex

The middle layer of the kidney, containing the pyramids

medulla

The size and echogenicity of the medulla are affected by what?

hydration status

Innermost layer of the kidneys, where the collecting system (calyces & ureter) and renal vessels are located and surrounded by fat

renal sinus

A cavity collection chamber that is continuous with the ureter and lies within the renal sinus

renal pelvis

The ureter courses to the...

urinary bladder

List the pathway of urine from the pyramids to the UB

Pyramids -> Papillae -> Minor Calyces -> Major Calyces -> Renal Pelvis -> Ureter -> Bladder

What are the functional units of the kidney?

nephrons

List the components of a nephron.

Renal corpuscle (glomerulus, glomerular capsule)

Renal tubule (PCT, Loop of Henle, DCT, collecting tubule)

Identify which components of a nephron are in the cortex of the kidney.

Renal corpuscle

Glomerulus

PCT/DCT

Identify which components of a nephron are in the medulla of the kidney.

Perinephric loop (Loope of Henle)

Collecting tubule

List the vascular components of a nephron.

efferent and afferent arterioles

peritubular capillaries

What portion of the kidneys is where filtration occurs?

in the renal cortex because it contains the glomeruli

Describe the sonographic features of the renal sinus.

Most hyperechoic/echogenic portion of the kidney due to fat, vessels, and collecting system

Describe the sonographic features of the renal pelvis.

Usually collapsed and not seen; if visible, anechoic (urine-filled/dilated)

Describe the sonographic features of the fibrous capsule.

a thin echogenic line forming the smooth outer contour of the kidney

Describe the sonographic features of the renal cortex.

medium-grey; homogenous; slightly hypoechoic to liver

Describe the sonographic features of the perinephric fat.

echogenic; surrounds kidney

Describe the sonographic features of the renal medulla.

hypoechoic to anechoic triangular areas (pyramids); good through transmission

Describe the sonographic features of the renal columns.

similar echogenicity to the renal cortex; hypoechoic compared to sinus

Describe the normal position of the adult kidney.

Left kidney is often 1-2cm higher than right

Superior poles more medial and posterior

Right (T12)/Left (T11-12)

Describe the normal position of a pediatric kidney.

Same retroperitoneal location as adults; more superficial, especially in infants

Inferior poles may extend below iliac crest (lower and more medial)

Describe the normal size of the adult kidney. Give:

Length

Wifth

AP

9-12 cm long

5-7.5 cm width

2-3 cm AP

What is the acceptable difference between the right and left kidney size in adults?

No more than 2 cm difference; more than 2 cm is abnormal

The parenchymal/cortical thickness is greatest where on the kidneys?

at the poles; can be measured

↑CKD = __ renal cortex thickness

↓

Describe the normal size of a pediatric kidney.

Proportionally larger kidneys relative to body size compared to adults.

Large pyramids relative to the cortex in neonates and infants.

By adolescence, kidneys will be adult sized

The large pyramids in pediatric kidneys are often mistaken for...

cysts

What part of the kidney grows with the child?

the renal cortex

What part of the kidney may not be well delineated in neonates?

renal sinus

The appearance of pediatric kidneys are very different from adult kidneys for the first __ _______.

6 months

Describe the normal shape of the adult kidney.

smooth, bean-shaped contour with echogenic capsule; c-shaped in transverse; ellipsoid-shaped

Describe the normal sonographic appearance of an adult kidney.

(Hypoechoic) Renal Medulla/Pyramids < Renal Cortex ≤ Liver < Spleen < Pancreas < Diaphragm < Renal Sinus = Renal Capsule (Hyperechoic)

Describe the normal sonographic appearance of a pediatric kidney.

cortex initially hypoechoic, then matures to adult echogenicity; pyraminds relatively larger early on

Describe the echogenicity of the renal cortex compared to the liver in a peds kidney.

Newborn: renal cortex is brighter (>) than the liver/spleen

6-8 Weeks: Cortex = liver/spleen

2-6 Months: Cortex is less echogenic (<) than liver/spleen

>6 Months: Cortex is more hypoechoic (<) to renal sinus

Possible scalloped appearance

Describe techniques that are useful for imaging the kidneys,

including patient positioning, transducer placement, and

respiratory techniques.

Patient Position: supine/RLD/LLD/prone; arm over head; pillow at waist level

Respiratory Techniques: suspended inspiration/expiration

Always scan both kidneys for comparison and compare their echogenicities to liver/spleen

Identify the blood supply to the kidneys.

Ao -> Renal AA -> Segmental AA -> Interlobar AA -> Arcuate AA -> Interlobular -> afferent arterioles -> glomerulus

Identify the blood supply from the kidneys.

glomerulus -> efferent arterioles -> peritubular capillaries -> vasarecta -> Interlobular -> Arcuate VV -> Interlobar VV -> Renal V -> IVC

What are the two most common lab requests for a renal sonogram?

BUN & creatunine

A BUN laboratory test measures what? Why is it important?

measures the amount of urea nitrogen in the blood; used to help determine renal function

An increase in BUN results indicates what?

renal failure

What is creatinine?

a waste product removed from the blood by glomerular filtration and eliminated in urine.

Increased levels of creatinine indicate what?

a decrease in kidney function; glomerulonephritis

A small defect of the cortex due to an incomplete fusion of the upper and lower poles during embryogenesis; extension of sinus fat into cortex

junctional parenchymal defect

How does a junctional parenchymal defect appear sonographically?

hyperechoic

wedge-shape in the anterior upper to middle aspect of the kidney

When part of the renal pelvis is located outside the renal hilum; has a cyst-like appearance.

extra-renal pelvis

How does an extra-renal pelvis appear sonographically?

prominent anechoic area central at hilum

With an extra-renal pelvis:

Transverse shows _______ (dilation/no dilation) in collecitng system

Renal cortex appears ______

________ (is/is not) surrounded by renal parenchymal

no dilation

normal

is not

When a kidney has two collecting systems and ureters separated by normal parenchymal tissue.

duplicated collecting system

Describe a duplicated collecting system with obstruction in the lower pole.

asymmetrical obstruction associated with vesicoureteral reflux and UTIs

A coritcal extension separating pyramids and occurs in 50% of the population.

enlarged column of Bertin

What are some sonographic features of an Enlarged Column of Bertin?

<3 cm

Resembles a pseudo-tumor

Isoechoic to renal cortex

A lateral buldge of the kidney cortex caused by pressure from the spleen; location?

dromedary hump, which may appear more often on the left

A dromedary hump variant may resemble...

neoplasm

When one or both kidneys do not ascend to their normal position in the upper abdomen, but to the pelvic region

ectopic (pelvic) kidney

What is the etiology of an ectopic (pelvic) kidney, and what is it associated with?

failed migration of one kidney; associated with gyn anomalies and abnormal blood supply

A congenital renal variant where there is excessive fat in the renal sinus.

renal sinus lipomatosis

What are some sonographic features of a Renal Sinus Lipomatosis?

Cortical thinning

Renal sinus thickens

Indented borders of the kidneys that are remnant of embryonic development; typically smooth out as child grows; appears lobulated

fetal lobulation

Which normal variant is not to be mistaken for hydronephrosis?

extrarenal pelvis

Failure of one or both kidneys to develop.

Renal Agenesis

Under/mal-development of a kidney; the contralateral kidney will increase in size to compensate for the dysfunctional kidney.

renal hypoplasia

T or F: A bilateral renal agenesis is usually compatible with life.

False

When both kidneys are fused at the upper and lower poles at the midline. Shows 2 distinct collecting systems.

pancake kidney

Pancake kidney etiology

fusion anomaly

A congenital anomaly in which two distinct functioning kidneys are connected at their lower poles by an isthmus of functioning renal parenchyma that crosses anterior to the aorta.

horseshoe kidney

Horseshoe kidney etiology and echogenicity.

fusion anomaly

same echogenicity as renal cortex

A fusion anomaly where one kidney crosses midline during embryonic development and the upper pole of one kidney fuses with the lower pole of the other.

Cross-fused kidney/crossed renal ectopia

T or F: A crossed ectopic kidney shows two collecting systems.

true

When you are born with more than 2 kidneys, more than 1 on one side.

supernumerary kidneys

Required longitudinal images of renal sonogram.

1. Survey medial to lateral

2. Long-axis at midline w/ and w/o length measurements

3. Long-axis of the most lateral aspect (2)

4. Long-axis of the most medial aspect (2)

5. Long-axis image demonstrating liver/spleen and kidney comparison

Required transverse images of renal sonogram.

1. Survey upper to lower poles

2. Trans. image: mid-pole w/ and w/o AP/width measurements

3. Trans. image: mid to superior

4. Trans. image: superior pole

5. Trans. image: mid to inferior

6. Trans. image: inferior pole

List the arterial supply to the UB.

Internal Iliac/Hypogastric Arteries -> Superior Vesicle Artery (Upper part for men & women) -> Inferior Vesicle Artery (Lower part for men) OR Vaginal Artery (Lower part for women)

Describe the shape of the UB

ovoid-rectangular when visualized in transverse (affected by surrounding structures)

Describe the size of the UB, the wall thickness, and the residual volume limit.

depends on urine amount, wall thickness should be ≤ 6mm; no more than 20cc of residual volume