Lower Urinary System

UT 302 - Abdomen 1

Label this image

1. Renal cortex

2. Renal medulla (pyramids)

3. Renal sinus

During early embryology of urogenital system, kidneys develop in 3 successive waves from cranial to caudal:

1. Pronephros

2. Mesonephros

3. Metanephros

What is the pronephros?

• Early in 4^th embryologic week

• A transitory nonfunctioning kidney at this stage

What is the mesonephros?

• Late in 4^th week

• Mid kidney provides partial function while the permanent kidney develops

What is the metanephros?

• 5^th week

• Third most inferior part of kidneys becomes permanent kidneys

The ___ duct (from the first phase) becomes the ___ duct that helps form the genitalia

pronephric; mesonephric

In males, the ___ duct is called the ___ duct

mesonephric; Wolffian

The Wolffian duct eventually becomes the …

epididymis, vas deferens, and the ejaculatory duct

In females, the ___ duct is called the ___ duct

mesonephric; Mullerian

The Mullerian duct eventually becomes the …

uterus and vagina

What are some of the common indications for urinary bladder point-of-care ultrasound (POCUS) examination?

• Bladder volume estimation

• Bladder mass

• Bladder outlet obstruction

• Hematuria

• Hydronephrosis

• Anuria

• Flank or pelvic pain

• Confirm proper placement of Foley catheter

What transducer is ideal for scanning the bladder?

• The low frequency curvilinear transducer is ideal for scanning the bladder (BL)

  • Can use the phased array low frequency transducer if the curvilinear transducer is not available

What are some lab value indicators of urinary system disease?

• Hematuria

• Blood urea nitrogen (BUN)

  • 2-8 mg/dL

• Serum creatinine

  • 0.5 to 1.2 mg/dL

What is hematuria?

• More than two to three blood cells per high-powered field are seen

• The presence of red blood cells in the urine

  • Can be microscopic or macroscopic

• The underlying cause can be located in the kidneys, ureters, bladder or urethra

  • Kidneys, urethra, and bladder can be visualized by US

What is the most common cause of hematuria?

Renal calculi (kidney stones)

What are the symptoms of renal calculi?

• Severe colic pain

  • When they are at the ureteropelvic junction (UPJ), ureterovesical junction (UVJ), or in the bladder

• Pain

• Nausea

• Vomiting

• Fever and chills

  • From associated infection, hematuria, dysuria, bacteriuria and /or leukocytosis

What is the color of normal, healthy urine?

Pale straw or transparent yellow color

What urine color suggests mild dehydration?

Darker yellow or honey-colored

What urine color suggests liver problems or severe dehydration?

Darker, brownish color

What urine color may suggest blood in the urine?

Pinkish or red

Kidneys are part of the ___ urinary system

upper

The ureters, bladder, and urethra are part of the ___ urinary system

lower

What structures play important roles in transporting, storing, and eliminating urine?

• Ureters

• Bladder

• Urethra

What structures are conduits in the process of eliminating urine?

• Pelvic ureter

• Urethra

What is the primary function of the bladder?

Functions as a temporary reservoir for urine storage as the kidneys produce urine and it flows down the ureter

T/F: normal pelvic ureters, abdominal ureters, and the urethra are not usually seen on an ultrasound

True

When can structures that are not normally visualized on US be visualized?

• When there is coexisting pathologic conditions

• Example: kidney stone blocking urine in the ureter

T/F: a urine-filled bladder is hard to see on US

False

Describe the anatomy of the urinary bladder

• Hollow, smooth, musculomembranous, collapsible sac

  • Lined with a mucous membrane of transitional epithelium that allows for expansion

  • Mucous membrane lining contains rugae or folds

  • Capable of considerable distention

  • When bladder is empty, membrane appears folded or wrinkled

• Normally, bladder is a round-edged tetrahedron

• Has 1 superior, 1 posterior, and 2 inferior surfaces

Where is the bladder located?

• Anatomically between ureter and urethra

• In the retroperitoneum on the pelvic floor just posterior to pubic symphysis

Where are the two ureteral orifices located in the bladder?

In the body on the posteroinferior portion of the trigone

Where is the urethral orifice located in the bladder?

In the neck of bladder and in the most inferior region

Label the image

1. Ureters

2. Ureteric orifices

3. Trigone

4. Bladder neck

5. Urethra

Describe the anatomy of the trigone

• Triangular

• No rugae

• Attached to muscular coat

• 3 openings

  • 2 ureters

  • 1 urethra

Why is it important for sonographers to recognize the bladder anatomy, including size, shape and appearance?

Because it helps the sonographer identify congenital anomalies of the bladder, pathologies and abnormalities in the surrounding anatomy

Is this a trans or long image of the bladder?

Long (triangular appearance)

Is this a trans or long image of the bladder?

Trans (rectangular appearance)

T/F: a full bladder also provides an excellent acoustic window to view the uterus and other pelvic organs

True

Small intestine coils lie adjacent to the ___ surface of bladder and are displaced ___ as the bladder enlarges

superior; posteriorly

The lower abdomen may visibly bulge with ___ of the bladder (acute/chronic urinary retention)

overdistention

At what volume of fluid is the adult bladder considered to be moderately full?

500 mL ~ 1 pint (but can hold almost double if neccessary)

What is the upper limit of normal for bladder wall thickness when the bladder is distended?

3 mm

What is the upper limit of normal for bladder wall thickness when the bladder is empty?

5 mm

Infants have a proportionally ___ bladder wall

thicker

Describe the anatomy of the ureters

• Slender tubes that convey urine from kidneys to bladder

  • From the renal pelvis, ureters descend in retroperitoneum and course obliquely through posteroinferior bladder wall

    • Each ureter is a continuation of the renal pelvis

• Continually contracts and relaxes, forcing urine downward in to the bladder about every 10-15 secs

What is the average ureter length?

30 cm

What is the average ureter diameter?

6 mm

How do the ureters prevent backflow of urine into the kidneys?

As bladder fills, the pressure increases causing upper and lower walls of terminal portions of ureter to become closely applied to each other to act as valves to prevent regurgitation of urine from bladder

When bladder is distended, the openings of ureters are about ___ apart, and the distance between them is 2.5 cm when the bladder is empty and contracted

5 cm

Where can the ureters become constricted?

1. At the junction at renal pelvis (ureteropelvic junction - UPJ)

2. As they cross the iliac vessels

3. At the junction with bladder (ureterovesical junction - UVJ)

Normally, the ureters are not seen on an ultrasound after they leave the renal pelvis until …

their entrance into the bladder

How do the ureteric orifices appear on US?

Two small bumps on the posterior aspect of the bladder on either side of midline

Describe these images

• Left: simultaneous jets of low-intensity echoes (arrows) are visualized entering urinary bladder (BL)

• Right: color Doppler demonstrates both right and left ureteral jets on transverse image on a male patient

What happens to the bladder during urination?

The bladder muscles contract and sphincter opens to allow urine to flow through the urethra

How long is the male urethra?

20 cm (travels through the penis and caries both semen and urine)

How long is the female urethra?

4 cm

What is the urachus?

• Embryonic tract formed as bladder descends into true pelvis

• Usually obliterates by birth, if it doesn't it creates a channel between bladder and umbilicus

Where is the bladder located in a fetus?

• At the umbilicus

• Communicates with the allantois (extension of cloacae/urogenital sinus)

What are the types of urachal variants?

1. Completely patent urachus

2. Urachal cyst

3. Urachal sinus

4. Urachal diverticulum

What is a completely patent urachus?

• About 50% of cases

• Both ends remain open, causing urine to leak from the umbilicus

What is a urachal cyst?

• About 30% of cases

• Both ends close off, and a cyst forms in the middle

What is a urachal sinus?

• About 15% of cases

• Closes at bladder end but not umbilicus

What is a urachal diverticulum?

• About 5% of cases

• Closes at umbilicus but remains patent at bladder

What is micturition?

Mechanism for voiding urine

What are the steps of micturition?

1. Starts with involuntary and voluntary nerve impulses

2. When volume of urine exceeds 200 to 400 mL, stretch receptors trigger transmission of impulses to lower portion of spinal cord

3. Initiates conscious desire to expel urine and a subconscious, micturition reflex

4. Combination of voluntary relaxation of external bladder sphincter muscle, reflex contraction of linear smooth muscle fibers along urethra

5. Contraction of detrusor muscle squeezes urine out of bladder

What is incontinence?

• Involuntary emptying of bladder

• Results from aging or trauma to any parts of nervous system by cerebral hemorrhage or cord injury

What is retention?

• The inability to empty bladder even though bladder contains an excessive amount of urine

• Catheterization may be used to relieve discomfort accompanying retention

30% of patients who are routinely catheterized eventually develop a ___ posteriorly at bladder neck from catheter trauma

“ledge”

Why is it bad to develop a “ledge”?

• Makes voiding difficult

• Considerably complicates catheterization process

How does a Foley catheter appear on US?

The catheter appears anechoic, with an echogenic exterior

Label the directions in this image

• A - superior

• B - anterior

• C - inferior

• D - posterior

Label the directions in this image

• A - right

• B - anterior

• C - left

• D - posterior

How should patients prepare for a bladder ultrasound?

• It is important for patients to properly prepare in order to better visualize the bladder with a transabdominal approach

• Bladder distention is absolutely essential to optimal visualization of bladder, bladder wall, and related anatomy

What are the three methods that can be used for bladder filling?

1. Instruct patient to drink 16 ounces of water 1 hour before exam and not to void until exam is completed

2. Instruct patient not to void before examination

3. Catheterizing patient and instilling fluid into bladder through a Foley catheter

What are some techniques for scanning the bladder?

• Most widely used approach to scan the urinary bladder is transabdominal method

• Patient is usually examined in supine position

  • May be necessary to position the patient in LPO/RPO or RLD/LLD to better demonstrate bladder wall abnormalities, movement of debris or calculi to dependent bladder wall, or bladder tumors

• To lesser extent, endovaginal, endorectal, and transperineal methods may be used for lower urinary tract

• Not necessary to restrict diet or use catheters or enemas to reduce intestinal contents or air

• Scan in both longitudinal and transverse planes transabdominally

  • May scan in longitudinal and coronal planes endovaginally and transperineally

What role do Foley catheters play in bladder US examination?

• Foley catheters are not routinely inserted for bladder filling unless it is a medical emergency

• Many studies show catheter insertion may introduce infectious contaminants into body

• Foley catheter balloon appears as round cystic structure in filled bladder and may cast shadows in areas of interest

What sonographic purpose does a fully distended bladder serve?

• Cystic reference in abdominopelvic anatomy

• Pushes adjacent bowel and gas out of field of view

• Provides “window” to identify pelvic anatomy

• Facilitates identification of dilated ureters

What pelvic structures should be routinely imaged in males?

• Bladder

• Seminal vesicles

• Prostate

• Rectum

What pelvic structures should be routinely imaged in females?

• Vagina

• Bladder

• Uterus

• Ovaries

• Adnexa

• Rectum

T/F: disease processes in pelvic structures can involve or mimic those of other closely related anatomy

True

What are some considerations for scanning the bladder?

• Knowledge of pelvic anatomy, genitourinary tract, gastrointestinal tract, pelvic vasculature, and pelvic musculature are important

• Transducer selection should take into consideration body habitus and exam objectives

  • Select highest frequency transducer possible to make sure penetration is adequate to visualize posterior aspect of areas of interest

• Equipment instrumentation includes harmonics, speckle reduction, spatial compounding, and computerized techniques to aid elimination of artifact echoes

1

Fundus of uterus

2

Endometrium of uterus

3

Pouch of Douglas (posterior cul-de-sac)

4

Rectum

5

Cervix

6

Vaginal stripe

7

Full bladder

8

Vesicouterine pouch (anterior cul-de-sac)

1

Bladder

2

Uterus

3

Ovary

4

Right ureteral orifice

What is shown in this image?

Long image of uterus and bladder

What is shown in this image?

Trans image of uterus and bladder

What is shown in this image?

Trans image of right ovary and bladder

What is shown in this image?

Trans image of left ovary and bladder

1

Bladder

2

Seminal vesicles

1

Bladder