Anatomy of the urinary tract – Part 2

Recap of the previous post :

• Location of the kidney
• coverings of the kidney
• muscles that are clinically related (quadratus lumborum etc)
• transpyloric plane – hilum
• differentiate kidney/splenic swelling (refer clinical notes)
• histology
• PCT, DCT –> difference in microscopic structure

Surgical relations

Left kidney

• Behind stomach lesser sac
• Infront left kidney : pancreas, splenic artery, stomach
• Left renal vein also drains left gonadal vein

Right kidney

• next to pouch of morrison (most dependent area for pus collection)

Anterior relations

 

Posterior Relations

3 important nerves lying anterior to the kidney:

• subcostal nerve
• iliohypogastric nerve
  • nephrectomy: post operative anaesthesia over the root of the scrotum –> nerve affected is the iliohypogastric nerve
• ilioinguinal nerve

Renal plexus

Sympathetic

• Abdominopelvic splanchnic nerves
• Have pain fibers
• Spinal segments: T11- L2 (loin pain – small of the back)
• Supplies the skin as well

Parasympathetic

• Vagus nerves
• No pain fibers

Nerves to Ureter:

• Renal plexus
• Aortic plexus
• Superior hypogastric plexus

Renal colic:

• very severe pain
• presenting suddenly and without warning
• at upper lateral mid back over the costovertebral angle (renal angle)
• radiates inferiorly and anteriorly towards the groin
  • Usually caused by stones in the kidey, renal pelvis or ureter
  • Pain is caused by dilatation, stretching & spasm of the ureter

Retrograde urography

From external urethral meatus, inject dye into the ureteric meatus. It is not invasive, therefore no pressure over kidney

 

Intravenous Pyelogram

Radio opaque dye. If kidney is not functioning properly, do not inject radio opaque dye, it will give more pressure to kidney. Only good to observe a normal kidney. Therefore it is not as preferable as the Retrograde Urography for diagnostic purposes.

Surface anatomy of the ureter in radiology can be found:

• lying on psoas major & tranverse processes (over the lumbar verterbra)

CT Scanning

Left side: liver & right kidney

Right side: pancrease & left kidney

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Left renal vein:

Also drains left testicular vein at right angle.

• Left kidney
• Left suprarenal
• Left testes, left ovary (left gonads)

Right renal vein:

Drains:

• Right kidney
• Right suprarenal

The left testes appears to be larger than the right testes. It is due to the left sided varicocele due to pressure effect on the left renal vein by the superior mesenteric artery. The superior mesenteric artery will obstruct the left renal vein, therefore will be ineffective drainage of blood in the left testicular vein causing a collection of blood in the left testis. The testicular vein will be dilated causing left sided varicocele.

 The ureter

Q: In xray, where are the 3 areas that we can see radio-opaque shadow? (the constrictions)

• where renal pelvis joins abdominal part of ureter
• where it crosses pelvic brim

  It enters pelvis by crossing bifurcation of common iliac arteries infront of sacro-iliac join.

• where it pierces the urinary bladder

Ureter:

• 25 cm long
• 3 parts

1) Pelvis of ureter

From hilum to lower pole of ki
dney

2) Abdominal part

From inlet of pelvis/pelvic brim to lateral angle of urinary bladder

3) Pelvic part, has 3 parts:

• From inlet of pelvis to ischial spine
• From ischial spine to outer wall of urinary bladder
• This part passes obliquely through bladder wall for about 2cm until opens into lateral angle of internal trigone

Course:

• Runs vertically downwards behind parietal peritoneum
• on psoas major muscle

IN FEMALE

In female:

• runs forward through the broad ligament (ligaments that connects uterus to lateral pelvic wall)
• related closely to cervix of uterus & uterine artery
• Also forms floor of ovarian fossa

Clinical significance:

When clamping uterine artery for surgery, ureter can be clamped accidentally.

Blood supply of the ureter:

Ureter receives blood supply from:

• Renal artery
• Aorta
• Common iliac artery
• Internal iliac artery
• Superior vesical artery
• Inferior vesical artery

In female, extra 2: (chain of anastomosis)

• uterine
• vaginal

During surgery, stripping of arteries can damage ureteric wall, because ureter depends on blood supply to undergo peristalsis for the excretion of urine. Therefore in this case, flow of urine can also be disrupted and might be the result of ureteric stricture.

_____________________________________________________________________Urinary Bladder

In young child:

• above pelvis

In adult:

• empty bladder –> lies in pelvic cavity behind pubic bones
• Urinary bladder full (500ml) –> part of bladder lies in lower abdomen (hypogastric region)

Parts of urinary bladder:

• Apex
• Base (posterior surface)
• Neck
• Superior surface
• Inferolateral surface

Blood supply:

• Superior vesical artery
• Inferior vesical artery

Venous drainage:

• Vesical venous plexus

Insertion of catheter will be resisted by 3 parts (curvature):

• At the bend of the penis (lift it up to straighten it)
• External urethral sphincter (voluntary – painful!)
• Internal urethral sphincter (involuntary)

If patient is unable to urinate for 24 hours (probably due to ureteric stones), there will be retention of urine in the urinary bladder. Urinary bladder will be distended into the abdominal cavity (full bladder). Therefore, perform a suprapubic cystostomy, the urine will flow out through there. This is like catheterisation but at the suprapubic region.

What are the structures in the bladder bed?

• Retropubic pad of fat
• Levator ani
• Prostate
• External urethral sphincter

Internal Trigone of bladder

Internal trigone: Equilateral triangle on inner aspect of bladder.

Entire bladder wall consists of many mucous folds, but there are no folds over the internal trigone (tense mucosa).

At the apex lies the: (inferior)

• Internal urethral orifice

At the base: (superior)

• Ureteric ridge

Internal urethral sphincter : Circular smooth muscle (involuntary)

Compressor urethrae/sphincter urethrae/external urethral sphincter (around membranous urethra): Actual voluntary sphincter (voluntary, control flow of urine)

When the integrity of the internal urethral sphincter is compromised –> incontinence.

Nerve supply of the urinary bladder

Autonomic

Parasympathetic (S2-4)

• Pelvic Splanchnic nerve
  • ganglia on bladder wall
  • contraction of detrusor muscle –> micturition reflex
  • autonomic reflex

Sympathetic (T11-L2)

• Hypogastric plexus
  • postganglionic fibres run in hypogastric plexus
  • Beta receptor: relaxes bladder wall
  • Alpha receptor: control internal urethral sphincter during filling (tonicity)
  • Incontinence: lack of sympathetic tone

Somatic

Pudendal nerve (S2-4)

• supply voluntary external urethral sphincter

Q: What are the 3 areas of the CNS that is involved in micturition?

1) Sacral Micturition centre (S2-4)

• Bladder contraction (stretch internal trigone –> sympathetic) by detrusor muscle (parasympathetic)

2) Pontine Micturition centre

• Relaxation of external sphincter (v
  oluntary)

3) Cerebral cortex (paracentral lobule)

• Inhibit sacral centre

Q: Injury of the sacral nerve root (S2-4) will cause:

• Detrusor areflexia
• Inability of detrusor muscle to contact
• Bladder will not be able to contract even when it is filled up
• Bladder will be distended
• Internal urethral sphincter will not be able to hold the large amount of urine –> overflow incontinence

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Urethra

Difference between male & female urethra

Female:

• Urethra: 4cm
• Embedded in anterior wall of vagina
• Orifice infront of vaginal orifice –> more chances of infection

Male:

• Urethra: 20cm
• 3 parts: Prostatic, membranous & penile (spongy)
• Penile part have 2 curves

 

Structures at posterior surface of urinary bladder in MALE:

Structures inside prostate:

• vas deferens
• seminal vesicle
• ejaculatory duct (vas deferens & seminal vesicle join)

Prostatic utricle: a blind sac, where numerous prostatic glands opens into prostatic urethra.

Secretions (for the protection of sperm):

• Acidic neutralize alkalinity of vaginal secretion
• Acid phosphatase
• Prostaglandin
• Zince

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Prostate

Prostate is a fibro-muscular-glandular organ, surrounding neck of urinary bladder & prostatic urethra.

Parts of prostate:

• Apex
• rests on sphincter urethrae
• Base
• around neck, anterior, posterior & infero-lateral surface

Lobes: (5)

• Anterior
• Median lobe
• In between 2 ejaculatory duct & prostatic utricle on back & urethra anteriorly
• 2 lateral lobes
• Posterior lobe

Q: Benign prostate hypertrophy (BPH): enlargement of inner part of gland, most MEDIAN lobe, by the action of TESTOSTERONE. Swelling of the uvula –> compresses the internal urethral orifce -> intermittent retention of urine. This occurs mostly in aged man, where there is always a frequent urge to urinate, however, urine cannot be expelled.

In BPH, transurethral approach (thru urethra) and enucleation of swelling is done.

True capsule of the prostate:

• Connective tissue of the prostatic gland

False capsule of the prostate:

• Outer to the true capsule: pelvic fascia
• It is in between veins of prostate.
• Therefore, if surgery is done from external, there will be bleeding. So, transurethral approach is favourable.

Structures inside the prostate:

• Vas Deferens
• Seminal vesicle
• Ejaculatory duct
• Multiple prostatic gland (acidic –> protect sperm)
• Prostatic utricle
• Prostatic urethra

Prostate can be felt par-rectal, during rectal examination.

Clinically important relations of the female urinary system.