Urinary Tract Anatomy

Question 1

What type of organ are the kidneys with regard to peritoneum?

Answer 1

Primary retroperitoneal

Question 2

Where are the kidneys located?

Answer 2

On the posterior abdominal wall, lying along vertebral body and the renal hylum (root of organ) tends to be extend from vertebral level T11 to L2/3, right tends to be lower and hila sits around L1
Around ribs 11-12
Ureters pass vertically down at L1 from the hylum inferior to pelvic cavity following tip of lumbar vertebrae transverse processes
The SMA can lie over the top of the left renal vein (can partially obstruct flow)
The pancreas and duodenum is anterior to them and gallbladder fundus can be close

Question 3

What is the hepatorenal recess?

Answer 3

AKA morrisons pouch - fluid can accumulate here in infection if patient is supine and create an abscess

Question 4

What are the anatomical relations of the kidneys?

Answer 4

On right: Suprarenal gland, liver, transverse colon, right colic flexure, jejunum and 2nd part of duodenum
On left: Suprarenal gland, stomach, spleen, pancreas (body), left colic flexure and jejunum

Question 5

What are the posterior relations to the kidney?

Answer 5

Costodiaphragmatic recess, diaphragm, parietal pleura, quadratus lumborum and psoas major

Question 6

How can kidneys be injured and why might a renal biopsy damage a lung?

Answer 6

Decreased/lost blood flow
Trauma to abdomen and haemorrhage to perinephric space
A renal biopsy may damage the lungs as the lungs can come behind the kidneys if a deep breath is taken by the patient

Question 7

Where would you palpate a kidney and can you feel them in a healthy person?

Answer 7

Balloting (palpating between 2 hands) can be done at the renal angle between 12th rib and lateral border of vertebral column extensor muscles
They are often not palpable

Question 8

Describe the kidneys internal structure.

Answer 8

Cortex - outer element
Multiple renal pyramids - in medullary region
Renal papilla - renal pyramid end where filtrate will drain through to appear in collecting duct system
Minor and major calyx - collecting duct system join to form broad area called renal pelvis leading into the ureter
Enormous bloody supply because of huge endocrine function
CT can pick up the structure of the kidneys

Question 9

What are the kidneys fascial coverings?

Answer 9

Surrounded by fat and supportive renal fascia:
Renal fascia space is over both left and right kidney (infection can spread between them) - supportive, protective and keeps them roughly in same place
Renal fascia - covers suprarenal glands too
Perinephric fat - supportive
Paranephric fat - protective

Question 10

What happens if the renal fascia is too lose?

Answer 10

Nephroptosis can occur which can obstruct urinary outflow from kidneys if they drop too low when the patient stands up

Question 11

Where does the kidney develop from in embryology?

Answer 11

They develop from the intermediate mesoderm (metanephros) and the ureteric bud

Question 12

How does the kidney develop in embryology?

Answer 12

Several stages: kidneys develop and become functional and then disappear
1st of all pronephros develops high up and disappears
Then mesonephros develops lower down and disappears
The adult kidney develops from metanephros and ureteric bud will develop collecting duct system within them
At this point the kidneys are near the cloaca so need to ascend to position on posterior abdominal wall

Question 13

What happens when the adult kidney structures in embryology start to ascend to their adult position?

Answer 13

They pick up new blood supplies from the aorta at each position, utilizing it and then getting rid of it

Question 14

What problems can arise in kidney embryology?

Answer 14

Polar renal artery - retains an extra blood supply from the ascent ->
Abberant renal artery - can squash ureter and dilate renal pelvis if enlarged for e.g. (can be asymptomatic)
Horseshoe kidney - joining of inferior poles of kidney AKA kidneys joined together -> can get stuck at midline IMA at L3 so cannot ascend to normal position
Agenesis of normal kidney
Pelvic kidney - no ascending
2 ureters attached to 1 kidney
Bifid/bifurcation of 2 ureters on 1 kidney
Duplicate kidney (could be useful)

Question 15

What can happens to the allantois in embryology of the bladder?

Answer 15

Allantois passes from bladder region of cloaca to umbilicus

This should disappear but instead becomes a fibrous cord from bladder to belly button called the urachus

Question 16

In rare cases, what can go wrong with the urachus in newborns?

Answer 16

This can grow cysts and lumps because its embryonic -> a cavity called a sinus may open so there is discharge seeping out of bellybutton from the cyst
Fistula could also occur where a sac of urine (allantoic cyst)/urine can come out of bellybutton as there is a connection from bladder to outside world due to remnants of allantois

Question 17

Why is the segmentation of the kidney important?

Answer 17

Formed from functionally independent segments alike the liver
Arteries run into each segment and branch
If a branch dies that means a segment will die as there is no collateral supply between segments

Question 18

What is the blood supply and venous drainage of kidneys and suprarenal glands?

Answer 18

Abdominal aorta branches off into right and left renal artery -> interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles
Left and right renal veins drain the kidneys and empty directly into the inferior vena cava
Around L1

Question 19

Why can men get left-sided varicocele?

Answer 19

Because the left testicular vein joins the left renal vein so issues with the left renal vein can present as left-sided varicocele of the testicles

Question 20

Where would pain present if a kidney stone/calculus was passing down the ureter?

Answer 20

Classic shifting long-groin pain from mid back to the groin on the same side of the body as the calculus descends the ureters
Visceral sensory nerves from ureter travel to CNS alongside sympathetic nerves - upper urinary system sends signals to T12 (innervates loin) -> lower urinary system sends signals to L1/2 (innervates groin)

Question 21

Where are the 3 classic positions for renal stones to get stuck in the ureter?

Answer 21

Renal pelvis
Where ureter crosses iliac arteries
Point of entry of ureter into bladder

Question 22

What is the ureters point of entry into the bladder?

Answer 22

At the vesico-ureteric junction level with the ischial spine

Question 23

What are the 4 surfaces of the bladder?

Answer 23

Posterior, superior and 2 x inferolateral

Question 24

What are some important structural features of the bladder?

Answer 24

Not balloon-shaped
Neck leads down to urethra
Trigone is a triangular shaped flattened area of mucosa and smooth muscle in which you can identify the ureter openings if it is inspected
Bladder and ureters lined by transitional epithelium so stretch out and are waterproof
Detrusor smooth muscle of bladder helps with weeing as it contracts the bladder

Question 25

Why does the detrusor muscle thicken in the bladder at one point?

Answer 25

To form the vesico-uteteric valve which prevents urine reflux during micturition

Question 26

What nerve are the urinary sphincters (many somatic) mostly innervated by?

Answer 26

Pudendal nerve (S2-4)
Innervates voluntary sphincters and carries sensitivity from external genitalia

Question 27

What are the male urinary sphincters?

Answer 27

Internal (involuntary) urethral sphincters
External (voluntary) urethral sphincters
Compressor urethrae

Question 28

What are the female urinary sphincters?

Answer 28

May/may not have a internal urethral sphincter
External urethral sphincter
Compressor urethrae
Sphincter urethrovaginalis

Question 29

How can sphincters and/or nerve supply be damaged?

Answer 29

Vaginal childbirth
Infections of brain/spinal cord
Stroke
Heavy metal poisoning
Diabetes

Question 30

What is the blood supply to the pelvic viscera?

Answer 30

Originates from internal iliac arteries which branch off to each organ i.e. ones to bladder are called vesical arteries
Venous drainage is from the external iliac vein, internal iliac vein and common iliac vein
Lymph tracks back along arterial supply

Question 31

How can the superior expansion of the bladder be exploited medically?

Answer 31

Suprapubic catheterisation: bladder can be accessed via the anterior abdominal wall layers - access via this route does not enter the peritoneal cavity

Question 32

What structures support the urinary bladder?

Answer 32

Pelvic floor
Perineal membrane & ligaments
Pubo-prostatic ligament (male)/pubo-vesical ligament (female)
Leviator ani

Question 33

What happens if the soft tissue support of the urinary bladder becomes weak in females?

Answer 33

Cystocele/prolapse of bladder

Question 34

Where do you feel the urge to micturate and why?

Answer 34

Because the top of the bladder is covered in peritoneum (pelvic pain line reminder), sensory nerves will travel back to the CNS with sympathetic nerves to T12-L2 which is where you will feel the urge to urinate

The other parts of the bladder are not covered in peritoneum so sensory nerves travel to CNS with parasympathetic nerves to S2-4 - this is the perioneal region where external genitalia is so you may feel the need to urinate here as well

Question 35

How do we learn to control the reflex of micturition?

Answer 35

In newborns, the bladder will stretch and the sensory signal will go back to sacral part of spinal cord and brain and the reflex to pee will just happen but in toilet training, children learn to suppress the reflex and contract voluntary sphincters however, this means when they need to pee they must promote the reflex so you can a master level of control over an involuntary reflex

Question 36

What spinal nerves are involved in micturition?

Answer 36

S2, 3 and 4 parasympathetic activity will cause micturition by contracting the detrusor muscle and relaxing the internal urethral sphincter
L1-2 sympathetic activity will stop micturition by contracting internal urethral sphincter and relax detrusor muscle
S2-4 pudendal somatic nerves will stop micturition by contracting external urethral sphincter which need to be relaxed to allow urination