Urology - Anatomy of urinary tract

Question 1

Where are the kidneys located?

Answer 1

The kidneys are retroperitoneal organs located on the posterior abdominal wall. The right kidney is slightly lower than the left kidney due to the downward displacement from the liver.

Question 2

What are the important posterior relations of the kidneys?

Answer 2

Posteriorly, both kidneys are related to the diaphragm (separating the pleura), quadratus lumborum, psoas, transversus abdominis, the 12th rib and three nerves - subcostal (T12), iliohypogastric, and ilio-inguinal (L1)

Question 3

What are the anterior relations of the kidneys?

Answer 3

The right and left kidney have different anterior relations.
The right kidney is related to the liver, the second part of the duodenum (which may be opened accidentally in performing a right nephrectomy) and the ascending colon.

In front of the left kidney lie the stomach, pancreas and its vessels, the spleen and the descending colon.

Question 4

What is the renal hilum?

Answer 4

In the medial aspect of each kidney is a deep vertical slit called the hilum. This transmits from front to back, the renal vein, renal artery pelvis of the ureter and usually a subsidiary branch of the renal artery.

Lymphatics and nerves enter the hilum (these being sympathetic mainly vasomotor fibres).

Question 5

How do anatomical variations in the renal pelvis make pyelolithotomy difficult?

Answer 5

Pyelolithotomy = removal of renal calculus. The renal. ureteric pelvis exhibits a large degree of anatomical variation. In some, it lies completely outside the substance of the kidney, or it may be almost completely buried in the hilum.

If a calculus is lodged in the pelvis, removal is much easier if the pelvis is located extrarenally compared to intrarenal.

Question 6

How does the pelvis of the ureter divide once inside the kidney?

Answer 6

The pelvis of the ureter divides into two or three major calyces, each of which divides into a number of minor calyces. Each of those in turn is indented by a renal papilla where the collecting tubules of the kidney discharge urine into the ureter.

Question 7

What are the layers of fat surrounding the kidney?

Answer 7

The kidneys lie in a fatty cushion called the perinephric fat. This is contained within the renal fascia. Above, the renal fascia blends with the fascia over the diaphragm leaving a separate compartment for the suprarenal gland.

Medially the fascia blends with the sheaths of the aorta and inferior vena cava. Laterally it is continuous with the transversalis fascia. It is only open inferiorly, tracking around the ureter into the pelvis.

The kidney is also surrounded by its own capsule.

Question 8

Outline the blood supply to the kidneys

Answer 8

The renal artery derives directly from the abdominal aorta. The renal vein, drains directly into the IVC. The left renal vein passes in front of the aorta immediately below the origin of the SMA. The right renal artery passes behind the IVC.

Question 9

What is the lymph drainage of the kidneys?

Answer 9

Lymphatics drain directly into para-aortic lymph nodes.

Question 10

Where does blood from a ruptured kidney or pus in a perinephric abscess travel?

Answer 10

Blood from a ruptured kidney or pus from an abscess will first distend the renal fascia, then force their way within the fascial compartment downwards into the pelvis. The midline attachment of the renal fascia prevents extravasation to the opposite side.

Question 11

What is “floating kidney”?

Answer 11

Floating kidney is also called hypermobility of the kidney. In this condition, the kidney can be moved up and down its fascial compartment but not side to side.

Question 12

What are the components of the ureter?

Answer 12

The ureter is approximately 25cm long and comprises the pelvis of the ureter, and its abdominal, pelvic and intravesical portions.

Question 13

Describe the course of the abdominal ureter

Answer 13

The abdominal ureter lies on the medial edge of psoas major (which separates it from the tips of the transverse processes of L2-L5). It crosses into the pelvis at the bifurcation of the common iliac artery in front of the sacroiliac joint.

Question 14

What are the important relations of the abdominal ureters?

Answer 14

Anteriorly, the right ureter is covered at its origin by the second part of the duodenum and then lies lateral to the IVC and then behind the posterior peritoneum. It is crossed by the testicular, right colic and ileocolic vessels.

The left ureter is crossed by the testicular (or ovarian) and left colic vessels. It then passes above the pelvic brim, behind the sigmoid colon to cross the common iliac artery immediately above its bifurcation.

Question 15

What is the course of the pelvic ureter?

Answer 15

The pelvic ureter runs on the lateral wall of the pelvis in front of the internal iliac artery to just in front of the ischial spine. It then turns forwards and medially to enter the bladder. In the male it lies above the seminal vesicle and is crossed superficially by the vas deferens.

In the female, the pelvic ureter runs downwards and forwards once it passes over the pelvic brim. It passes underneath the base of the broad ligament. As it does so it is crossed by the uterine arteries.

Question 16

What is the blood supply to the ureter?

Answer 16

The ureter receives a segmented blood supply from all the available arteries along its course: the aorta, renal, testicular (or ovarian), internal iliac and inferior vesicle arteries.

Question 17

How can the ureter be exposed surgically?

Answer 17

Throughout its abdominal and upper part of its pelvic course, the ureter adheres to the overlying peritoneum. As the parietal peritoneum is dissected upwards, the ureter comes into view sticking to its posterior aspect.

Question 18

At what 3 sites is the ureter narrowed?

Answer 18

• at the junction of the pelvis of the ureter with its abdominal part
• at the pelvic brim
• at the ureteric orifice (narrowest of all)

A ureteric calculus is likely to lodge at one of these three levels

Question 19

What are the anatomical relations of the male bladder?

Answer 19

The bladder sits in front of the pubic symphysis. Superiorly, it is covered by peritoneum. Behind is the rectum, termination of the vas deferens, and the seminal vesicles. Laterally, there is the levator ani and obturator internus muscles.

The neck of the bladder fuses with the prostate in the male, in the female it lies directly on the pelvic fascia surrounding the shorter urethra.

There is a layer of fatty connective tissue that sits between the bladder and the rectum in the male.

Question 20

Describe the internal surface of the bladder

Answer 20

The bladder consists of smooth muscle lined with mucosa (uroepithelium). On each side, the ureters enter the bladder obliquely at the ureteric ostium. Urine leaves the bladder via the internal urethral meatus. There is a projection just above the meatus called the uvula.

The mucosal layer of the bladder is thrown into a trabecular arrangement which flattens out when the bladder is expanded. The mucosa becomes smooth in a triangle called the trigone, between the ureteric ostia and the internal meatus.

Question 21

What is the blood supply to the bladder?

Answer 21

Blood is supplied from the superior and inferior vesical branches of the internal iliac artery. The vesical veins form a plexus which drains into the internal iliac vein.

Question 22

What are the 3 parts of the male urethra?

Answer 22

1) prostatic
2) membranous
3) spongy

Question 23

How does prostatic fluid enter the urethra?

Answer 23

The prostatic urethra is the first part of the urethra in the male. It passes through the substance of the prostate gland. Prostatic fluid contributes a portion of the seminal fluid and enters the urethra from its posterior wall. In fact there is a longitudinal ridge on the posterior wall of the prostatic urethra called the urethral crest. On each side of the crest is a shallow depression called the prostatic sinus into which the prostatic secretions empty and join the urethra.

Question 24

What is the prostatic utricle?

Answer 24

The prostatic utricle must not be confused as the entry point for prostatic secretions into the urethra, they come from the prostatic sinus. The prostatic utricle sits at the middle of the urethral crest and is a blind passageway that passes upwards towards the middle lobe of the prostate. It is believed to be the male equivalent of the vagina and a remnant of the paramesonephric duct.

Question 25

How does seminal fluid from the ejaculatory ducts enter the urethra?

Answer 25

The ejaculatory ducts form from the fusion of the ampulla of the vas deferens and the duct of the seminal vesicle. On either side of the orifice of the prostatic utricle are the openings of the ejaculatory ducts.

Question 26

Describe the course of the membranous urethra?

Answer 26

The membranous urethra is the second part of the male urethral and emerges from the base of the prostate. In both males and females it must pass through the external sphincter (females only have an external sphincter) called sphincter urethrae. It is continuous with a sling of muscle that forms the pelvic diaphragm. The part that envelops the membranous urethra is called the levator prostatii. This is the most anterior and medial part of the pubococcageous muscle which in turn is part of the levator ani muscle complex.

Just below the pelvic diaphragm the membranous urethra passes through the perineal membrane.

Question 27

In what structure is the spongy urethra located?

Answer 27

The spongy urethra traverses the corpus spongiosum of the penis. It first passes forwards to lie below the pubic symphysis, where it can be damaged by a fall astride a sharp object.

Question 28

For what reason should catheters be introduced downwards into the beak of the urethra?

Answer 28

Immediately within the meatus, the urethra dilates into a terminal fossa with a roof that has a mucosal fold called the lacuna magna. This may catch the tip of a catheter which is why they should always be introduced downwards.

Question 29

Describe the course of the female urethra

Answer 29

The female urethra is much shorter than the male and is surrounded by the external urethral sphincter muscle (sphincter urethrae). Unlike the males, the female urethra only has one sphincter. The female urethra is embedded in the wall of the vagina and opens into the vestibule of the vagina. Both the urethra and vagina pass through the pelvic diaphragm to enter the vestibule.

The external urethral meatus opens above the clitoris.

Question 30

What is the mucosal lining of the urinary tract?

Answer 30

In both the male and female, the pelvis, ureter, bladder and urethra are lined by a transitional epithelium. In males, this extends to the entry of the ejaculatory ducts in the prostatic urethra. This is called uroepithelium.

The rest of the urethra has a columnar lining, except at its termination where the epithelium becomes squamous.

Question 31

What is the inguinal ligament?

Answer 31

The inguinal ligament is a thickening of the external oblique aponeurosis. It runs from the anterior superior iliac spine to the pubic tubercle medially. The edge of the ligament cannot be seen from the externally, because the fascia lata (the investing layer of fascia surrounding the lower limb) is attached to the lower edge of the ligament.

On the inside, the iliopsoas fascia is attached the lower edge of the ligament.

Question 32

What is the lacunar ligament?

Answer 32

Medially, as the inguinal ligament approaches its insertion onto the pubic tubercle, some of the fibres fan out and pass backwards to attach to the superior curved edge of the pubic ramus or pectin. This produces a traingular piece of ligament called the lacunar ligament.

Question 33

What is the conjoint tendon?

Answer 33

The conjoint tendon is formed by the fusion of fibres from the transversus abdominus and internal oblique aponeurosis. Both of these muscles arise from a thickening of the iliopsoas fascia.

The conjoint tendon inserts onto the pubic crest and the pectin.

Question 34

Where is the superficial inguinal ring located?

Answer 34

There are 2 rings that form the inguinal canal, superficial and deep. The superficial inguinal ring is formed from an opening in the external oblique aponeurous. It is important because the spermatic cord (or round ligament in females) passes through the canal. The opening itself has an inferior crus and a superios crus, which are attached to the pubic tubercle and pubic crest respectively.

The inguinal canal passes backwards through the superficial ring and underneath the free borders of the internal oblique and transversus abdominus muscles to meet the deep inguinal ring.

Question 35

Where is the deep inguinal ring?

Answer 35

The inguinal canal is formed by the descent of the testes as they pass from the abdominal cavity into the scotrum. The deep (or internal) inguinal ring represents the point at which the spermatic cord pushes through the transversalis fascia, dragging from it a covering which forms the internal spermatic fascia. The ring is demarcated medially by the inferior epigastric vessels passing upwards from the external iliac artery and vein.

Question 36

What are the borders of the inguinal canal?

Answer 36

The inguinal canal is best thought of as an oblique passageway from the outer to innermost layers of the abdominal wall.

Anteriorly - the skin, superficial fascia and the external oblique aponeurosis cover the full length of the canal

Posteriorly - the conjoint tendon forms the posterior wall of the canal medially, the transversalis fascia laterally.

Above - arch the lowest fibres of the internal oblique and transversus abdominis muscles

Below - inguinal ligament

Question 37

What are the contents of the spermatic cord?

Answer 37

As the testes descend from the abdomen and into the scrotum they take a layer of each muscle they pass through, which then wraps around the spermatic cord. The contents of the cord are best remembered by the “rule of 3s” - 3 layers of fascia, 3 arteries, 3 veins, 3 nerves, and 3 other structures.

3 layers of fascia - external spermatic fascia (from the external oblique aponeurosis), the cremasteric fascia (from the internal oblique) and the internal spermatic fascia (from the transversalis fascia)

3 arteries - testicular (from the aorta), cremasteric (from the inferior epigastric), the artery of the vas (from the inferior vesicle)

3 veins - pampiniform plexus, cremasteric vein, and vein of the vas (both of these accompany their arteries)

3 nerves - nerve to cremaster, sympathetic fibres from T10-11 spinal segments, ilioinguinal nerve (strictly on not in the cord)

3 other structures - vas deferens, lymphatics of the testis, and pathologically a third structure, a patent processus vaginalis in patients with an indirect inguinal hernia.

Question 38

What is the scrotum?

Answer 38

The scrotum is a pouch in which the testes and their coverings are held. In cryptorchidism, the scrotal pouch is usually underdeveloped.

Question 39

What are prone to form in the scrotum and why?

Answer 39

The scrotum has a large number of subaceous glands and is therefore a common site for sebacceous cysts to form.

Question 40

What is the dartos muscle?

Answer 40

The subcutaneous tissue of the scrotum contains no fat but does have an involuntary muscle called the dartos muscle, lying in the superficial fascia of testes, outside the external spermatic fascia.

Question 41

Why are fluid extravasations in the scrotum always bilateral? Where do they come from?

Answer 41

The scrotal subcutaneous tissue is continuous with the fascia of the abdominal wall and perineum, and therefore extravasations of urine or blood deep to this plane will gravitate to the scrotum. The scrotum is divided by a septum into right and left compartments but this septum is incomplete superiorly so extravasations of fluid into this sac are always bilateral.

Question 42

What is the tunica albuginea, how is it related to the tunica vaginalis?

Answer 42

Below the spermatic fascia formed by the external, cremasteric, and internal spermatic fascae, the testes are covered by a thin membranous envelope called the tunica vaginalis. The tunica vaginalis creates a fluid filled envelope around the testes. It is a remnant of peritoneum and like peritoneum has both parietal (outer) and visceral (inner) layers that are a continuation of one another.

The visceral layer of the tunica vaginalis covers a white fibrous capulse called the tunica albuginea which encloses the testes.

Question 43

Where is the epididymis located?

Answer 43

The epididymis is loosely attached to the posterior aspect of the testes. It has a head (formed by the efferent ducts of the testes), a body and a tail. The tail of the epididymis loops around to form the vas (or ductus) deferens.

The internal structure of the epididymis is extremely convoluted. It is covered by the tunica vaginalis except at its posterior margin where it is free.

Question 44

How do spermatozoa get from the seminiferous tubules into the epididymis.

Answer 44

Spermatozoa are produced in the seminiferous tubules. The seminiferous tubules pass upwards and backwards to converge on a fibrous area called the mediastinum of the testes. From here they form a network of tubules called the rete testes. About 4-12 efferent ducts emerge from the rete testes which leave the testes and pass into the upper part (or head) of the epididymis where they unite to form the duct of the epididymis.

Question 45

Describe the blood supply to the testes

Answer 45

The testicular artery arises from the aorta at the level of the renal vessels. It anastomoses with the artery to the vas which arises from the inferior vesical branch of the internal iliac artery. Between them they supply the testes, vas deferens and epididymis. This cross connection means that ligation of the testicular artery does not necessarily result in testicular atrophy.

Question 46

Where does venous blood from the right and left testes drain into?

Answer 46

Blood from the right testes drains directly into the IVC.

Blood from the left testes drains into the left renal vein.

Question 47

Where does lymph from the testes drain to?

Answer 47

The lymphatic drainage of the testes obeys the usual rules - it follows the venous drainage. Thus, it passes to the para-aortic lymph nodes at the level of the renal vessels. Free communication occurs between lymphatics on either side, as well as to intrathoracic and cervical nodes. Therefore the spread of malignant disease from the testes to the nodes at the root of the neck is not uncommon.

Question 48

Describe the developmental descent of the testes

Answer 48

The testes arise from a germinal ridge of mesoderm in the posterior wall of the abdomen just medial to the mesonephros. It links up with the epididymis and vas. As the testes enlarge, they also undergo a caudal migration:

• 3rd month of fetal life - reaches the iliac fossa
• 7th month - traverses the inguinal canal
• 8th month - reaches the external ring
• 9th month - descends into scrotum

Question 49

What is the gubernaculum testes?

Answer 49

This is a mesenchymal strand that extends from the caudal testes along its descent and blends into the scrotal fascia. The exact role of this structure in the descent of the testes is unknown, but it may act as a guide (gubernaculum = rudder)

Question 50

What is the processus vaginalis?

Answer 50

In the 3rd fetal month, a prolongation of peritoneal cavity invades the gubernacular mesenchyme and projects into the scrotum as the processus vaginalis. The testes slide into the scrotum posterior to this and projects into it. They are therefore covered on the front and sides by peritoneum. About the time of birth this processus obliterates leaving the testes covered by the tunica vaginalis.

Question 51

What area needs to be palpated if you suspect malignant spread of disease from the testes?

Answer 51

The upper abdomen must be palpated carefully for enlarged para-aortic lymph nodes. Because of cross communication in the lymphatics this may be present either side. Mediastinal and cervical lymph nodes may also be involved. It is a beginner’s mistake to feel for nodes in the groin! These are only involved if the tumour has ulcerated the scrotal skin and hence invaded scrotal lymphatics which drain into inguinal nodes.

Question 52

What can a rapidly developing varicocele suggest?

Answer 52

Varicocele = dilation of the pampiniform plexus of veins. If this is very rapid it can suggest a tumour of the left kidney, which, by invading the renal vein, blocks the drainage of the left testicular vein. Most examples of varicocele though are idiopathic.

Question 53

What differentiates failure of the testes to descend vs retraction of the testes?

Answer 53

The testes may fail to descend anywhere along their course - intra abdominally, within the inguinal canal, at the external inguinal ring, or high in the scortum. Failure to descend is different from testicular retraction. This is common in children, and retraction of the cremaster muscle draws up the testes into the superficial inguinal pouch - a potential space deep to the superficial fascia over the external ring. Gentle pressure from above can usually move the testes into the scrotum.

Question 54

What causes an indirect inguinal hernia?

Answer 54

Indirect inguinal hernias are caused by abnormalities in the obliteration of the processus vaginalis. Indirect hernias pass through the external inguinal ring and are confirmed surgically by lying lateral to the inferior epigastric vessels. They are differentiated from a femoral hernia by being inferior and medial to the pubic symphysis.

Question 55

What are the different types of hydrocele?

Answer 55

The closed off tunica vaginalis may become distended with fluid to form a hydrocele. These may be idiopathic (primary) or secondary to disease in the underlying testis. They are classified into:

1) Vaginal - confined to the scrotum and so called because it distends the tunica vaginalis
2) Congenital - communicating with the perionteal cavity
3) Infantile - extending upwards to the internal ring
4) Hydrocele of the cord - confined to the cord

Question 56

Outline the course of the vas deferens from the testes to the bladder

Answer 56

The vas deferens is formed from the tail end of the epididymis. The vas passes within the spermatic cord along with nerves and testicular blood vessels. The vas enters the inguinal canal at the superficial inguinal ring, located in the external oblique aponeurosis. It then passes through the canal and exits it via the internal or deep inguinal ring which is formed from an opening in the transversalis fascia. The vas then passes backwards over the dome of the bladder and crosses the ureter. It then moves downwards behind the bladder where it dilates to form the ampulla. The ampulla then joins with the seminal vesicles to form the ejaculatory ducts.

Question 57

What condition typically involves enlargement of the seminal vesicles?

Answer 57

Tuberculous infection

Question 58

Where is the prostate located?

Answer 58

The prostate is a pyramid shaped organ composed of smooth muscle and glands. It sits below the bladder and surrounds the prostatic urethra.

Question 59

What are the relations of the prostate?

Answer 59

Superiorly - the prostate is continuous with the neck of the bladder.

Inferiorly - the apex of the prostate rests on the external sphincter of the bladder which lies within the pelvic diaphragm.

Anteriorly - lies the pubic symphysis separated by the extraperitoneal fat of the cave of Retzius or retropubic space. Close against the prostate in this space lies the prostatic plexus of veins. Near the apex of the prostate, the puboprostatic ligament passes forwards to the pubis

Posteriorly - lies the rectum separated by the fascia of Donvilliers

Laterally - levator ani

Question 60

Where do the ejaculatory ducts enter the prostate?

Answer 60

The ejaculatory ducts pass through the upper part of the gland to open into the urethra. They do so in an area called the colliculus. This is a raised portion of the urethral crest on the posterior urethral wall where the prostatic utricle is located. There is one opening on either side of the utricle on the coliculus.

Question 61

What are the prostatic capsules? How many are there?

Answer 61

The prostate is enveloped in fibrous capsules. There are normally 2 of them, but in pathological processes there are 3.

1) A true capsule - a thin fibrous sheath which surrounds the gland
2) A false capsule - condensed extraperitoneal fascia which continues into the fascia surrounding the bladder and with the fascia of Denonvilliers posteriorly. Between these 2 capsules lies the prostatic venous plexus

3) Pathological capsule - when benign adenomatous hypertrophy of the prostate takes place, the normal peripheral part of the gland becomes compressed into a capsule around this enlarging mass.

Question 62

What is the blood supply to the prostate?

Answer 62

The arterial supply is designed from the inferior vesical artery (a branch of the internal iliac artery), a branch entering the prostate on each side at its lateral extremity.

The veins form a prostatic plexus which receives the dorsal vein of the penis and drains into the internal iliac vein on either side. Some of the venous drainage passes to the plexus of veins lying in front of the vertebral bodies and within the neural canal. These veins are valveless and constitute the valveless vertebral veins of Batson. This is an important haematogenous route of spread from prostate cancer to the vertebral column.

Question 63

Why is the fascia of Denonvillier’s important surgically?

Answer 63

In excising the rectum, it is the plane to be sought after in order to separate off the prostate and urethra without damaging these structures. A carcinoma of the prostate only rarely penetrates this fascial barrier so that ulceration into the rectum is very rare.

Question 64

Why is the colliculus an important landmark when performing a TURP?

Answer 64

A TURP involves removal of the hypertrophic mass of glandular tissue from the surrounding normal prostate, which is compressed into a thin rim around it - a false (or pathological) capsule. The colliculus is a useful landmark, because the surgeon must keep his resection above this structure in order not to damage the urethral sphincter.

Question 65

What is the internal structure of the penis?

Answer 65

The penis is composed of 3 cylindrical masses of expandable tissue. On either side are the 2 corpora cavernosa (singular = cavernosum). These are the main erectile tissue of the penis and are contained in a strong fibrous capsule, the tunica albuginea. Each cavernosa is composed of blood filled sinuses and are separated from each other by an incomplete septum.

Along the underside of the penis is the corpus spongiosum. The urethral is contained within it. It also contains expandable vascular tissue, but it remains soft during erection.