A 28-year-old man is brought to the emergency department after a tree fell across his pelvis. The patient has severe pelvic pain. Past medical history includes type I diabetes mellitus. Medications include NPH insulin and over-the-counter nasal decongestants. Temperature is 37.0°C (98.6°F), pulse is 90/min, respirations are 20/min, and blood pressure is 100/75 mmHg. The patient is drowsy but responds to verbal commands. The abdomen is nondistended. Urologic examination reveals blood at the external urethral meatus. He is started on intravenous fluids, and a suprapubic cystostomy is performed. Which of the following abdominal layers is pierced during this procedure?

Anatomy clinical correlates: Male pelvis and perineum

Chapters:

Introduction0:00–0:33

The pelvis lies between the abdomen and the lower limbs, forming the lower part of the trunk. It supports and contains organs of the gastrointestinal system, the urinary system, and the reproductive system.

Furthermore, the structure and contents of the pelvis differs between biological male and biological female individuals.

For biological males, there are many clinical conditions that can affect the pelvis and the perineum, and we mean more than just the ones that will make you famous on Youtube or get you on America’s Funniest Home Videos.

The pelvis is formed by the ilium, ischium, pubis, and sacrum, forming a ring of bones called the pelvic ring. Pelvic bones, like any other bone in the body, are susceptible to injury and subsequent fracture.

Pelvic fractures0:33–2:45

Fractures of the pelvis usually occur following severe trauma, and this can happen through a variety of mechanisms. Fractures can occur in isolation, but since the pelvis is shaped like a bony ring, they tend to occur in two or more areas simultaneously, which means they’re unstable fractures.

Think of trying to break a pretzel at only one point! Direct trauma, for example a car crash, may fracture susceptible areas such as the pubic rami, the acetabulum, the sacroiliac joints, and the ala of the ilium.

Other mechanisms of injury include falling directly on one of the lower limbs, which can force the head of the femur into the pelvic cavity through the acetabulum.

These different injuries can damage pelvic structures such as vessels, nerves, and viscera, resulting in a variety of clinical manifestations.

One classic example is called an open book fracture, where there is pelvic ring disruption due to anterior widening typically at the pubic symphysis.

Fracture of the medial portion of the pubic rami can lead to injury of the urinary bladder and urethra, as well as sensory damage to the anterior and medial thigh and motor weakness to the muscles supplied by the femoral nerve.

Generally, pelvic fractures cause pain that increases with movement and mobility, as well as swelling and bruising at the area of impact.

In more severe cases, pelvic fractures can cause damage to vascular structures and organs of the pelvis, which can lead to life threatening hemorrhage that fills the expanded pelvis and extends into the retroperitoneum.

In patients with life threatening hemorrhage and hemodynamic instability, quick stabilization with a pelvic binder is done.

This is a device that compresses the pelvis along with the hemorrhaging vessels, therefore controlling the bleeding. Surgery may be done, which aims to stabilize and reduce the fracture.All right, now let’s switch gears and talk about the prostate gland, which is a small gland, about the size of a walnut, which is positioned inferior to the bladder and anterior to the rectum.

Benign prostatic hyperplasia2:45–5:52

One of the most common conditions affecting the prostate is benign prostatic hyperplasia, or BPH for short. This condition occurs due to the hyperplasia or proliferation of the prostatic tissue within the prostatic transitional zone.

This condition can begin to affect males as early as age 40, and can affect up to 60% of males at age 60, and over 80% of males at age 80!BPH can be asymptomatic, however it can also compress the prostatic urethra, causing symptoms such as nocturia, which is the need to void throughout the night; frequency, which is peeing more often typically in smaller volumes; incontinence, which is the inability to voluntarily urinate; dysuria, which is difficulty or pain during urination; and urgency, which is the sudden need to void.

Patients typically report that they have a slow urinary stream, they strain when trying to void, or they have dribbling of urine.

This can all lead to an increased risk of urinary tract infections, bladder distension, and renal injuries.BPH is often diagnosed clinically with a digital rectal examination, or DRE.

Here, a finger is inserted into the rectal orifice where it is directed anteriorly to feel the prostate through the anterior wall of the rectum, which is in contact with the posterior surface of the prostate.

In benign prostatic hyperplasia, the DRE findings may be normal, however the prostate can be enlarged, where it will have a homogeneously smooth and soft consistency.

This is in contrast to adenocarcinoma of the prostate, where a DRE would reveal a hard, irregular consistency of the prostate.

However, it’s worth noting that a definitive diagnosis of either BPH or prostate adenocarcinoma requires a prostatic biopsy, and only histological and pathological examination can distinguish benign disease from malignant disease.Now, there are also some clinical differences between the two.

BPH typically affects the transitional zone and compresses the prostatic urethra, so it causes symptoms earlier than adenocarcinoma.

Prostatic adenocarcinoma, on the other hand, typically affects the posterior lobe or peripheral zone of the prostate, so patients experience urinary symptoms much later, and they’ll often present with more advanced disease progression and metastases - most often, to lymph nodes, liver, lungs, brain and bone.

Metastases mainly occur in the internal iliac and sacral lymph nodes, which drain the prostate. Metastasis to the skeletal system occurs because the prostatic venous plexus directly communicates with the vertebral venous plexus which also has valveless communication with the cerebral circulation, allowing metastasis to the vertebrae and brain.Treatment of BPH aims at relieving the obstruction and allowing the urine to flow normally.

BPH treatment5:52–7:43

This can be done by using 5 alpha-reductase inhibitor medications such as finasteride, which inhibits the action of androgens on the prostate by preventing conversion of testosterone to dihydrotestosterone, trying to limit prostate enlargement.

Alpha-adrenergic blockers such as tamsulosin can also be used which relax the smooth muscle in the prostate and bladder neck to alleviate the symptoms.

Additionally, a transurethral resection of the prostate, or TURP, may be done, where “transurethral” means, well, through the urethra!

During a TURP, an instrument called a cystoscope is inserted through the tip of the penis and into the urethra to access the prostate gland.

Then, the enlarged part or even the entire prostate can be removed. Following TURP, or instead of it, a prostatectomy can also be performed, which is the surgical removal of the prostate or part of it.

There are two types of prostatectomy. A simple prostatectomy refers to the removal of prostate tissue within its capsule through methods such as open surgery, laparoscopic surgery, or even robotic surgery where a transurethral approach is difficult, and is often reserved for BPH.

On the other hand, a radical prostatectomy is the removal of the entire prostate gland, seminal vesicles, ejaculatory ducts, terminal ductus deferens, and potentially the surrounding lymph nodes.

This is typically done to treat more invasive disease, like prostate adenocarcinoma. In a prostatectomy, potential injury to the internal urethral sphincter can occur, and this results in urinary incontinence.

Additionally, within the prostatic fascia, there’s the prostatic nerve plexus which originates from the inferior hypogastric plexus, which receives parasympathetic innervation from the S2-S4 nerve roots.

Erectile dysfunction7:43–9:46

This prostatic plexus may become damaged during surgery and this is important as it gives rise to the cavernous nerves, which carry postsynaptic parasympathetic nerve fibers innervating the corpora cavernosa which are responsible for maintaining an erection.

To remember this, think of the phrase ‘S2, 3, 4 keeps the penis off the floor’. So, damage to the prostatic nerve plexus can result in erectile dysfunction, which is the inability to get or maintain an erection.

Remember that an erection happens when the parasympathetic nerve fibers are stimulated, which causes the cavernosal spaces to expand and fill with blood.

Then, the corpora cavernosa grow in size, and the penis maintains an erection. Ejaculation, on the other hand, and prevention of retrograde ejaculation is governed by sympathetic innervation, which comes from the T11 through L2 nerve roots and travels with the abdominopelvic splanchnic and hypogastric nerves.

Finally, the expulsion of sperm is assisted by somatic nerves, specifically the pudendal nerve. A good memory trick is the phrase ‘Point and Shoot’, where the P in pointing stands for parasympathetic and is responsible for erection, and the S in shoot stands for sympathetic and somatic which is responsible for ejaculation.

Besides injury to the cavernous nerves, other causes for erectile dysfunction include psychological and pathological causes.

Psychological causes include stress, performance anxiety, and depression. Cardiovascular diseases, such as atherosclerosis, may decrease the blood supply to the penis, resulting in erectile dysfunction.

Finally, endocrine disorders, such as hypogonadism, which causes low testosterone levels, can also cause erectile dysfunction.

Okay, now let’s take a deep breath and have a quick quiz! Can you name this condition in the prostate?

Quiz9:46–10:03

Okay, now this condition may be diagnosed with this clinical exam, can you recall its name?Okay, now let’s switch gears and look at how the anatomy of the male reproductive organs can impact reproduction!

Vasectomy10:03–11:14

Remember that the testes produce sperm cells, technically called spermatozoa, which are stored for maturation in the epididymis.

Then, the sperm cells are transported through a series of ducts which eventually continue as the ductus deferens, before travelling through the urethra during ejaculation.

In males who no longer want to reproduce, a procedure called a deferentectomy can be done, most commonly known as a vasectomy.

Here, part of the ductus deferens is manually felt in the superior part of the scrotum, where local anaesthetic is placed and a small incision is put into the superior part scrotum.

The ductus deferens is then located, and it is either ligated or excised. Following a vasectomy, the male can still ejaculate, but the semen contains no sperm.

But where does the sperm go? The sperm eventually degenerates in the epididymis and the proximal part of the ductus deferens.

And of note, vasectomy does allow for second chances as the procedure can be reversed and the sectioned ductus deferens can potentially be reattached.

All right, now let’s switch gears and talk about the urethra, which is anatomically different between biological males and females.

Male urethral catheterization11:14–12:21

In females, the urethra is only about 4 centimeters long, and it’s also straighter, and more elastic. In males, the urethra is longer, measuring roughly between 18 and 22cm, curved, and less elastic.

Due to the urethral length, along with the drier periurethral environment in males, they are less prone than females to microbial contamination and subsequent urinary tract infection.

Understanding the anatomy of the male urethra can also come in handy when it comes to transurethral catheterization. This is when a soft, hollow tube is passed through the urethra and into the bladder to drain urine in an individual who can’t urinate.

When using a catheter, the curves of the male urethra need to be considered. The male urethra has four parts; starting proximally from the bladder there is an intramural or preprostatic part, a prostatic part, an intermediate or membranous part, and lastly the spongy part.

Okay, now incorrect placement of the catheter during a urethral catheterization can damage and potentially rupture any part of the urethra; usually the membranous part, which is not as well protected.

Urethral injuries12:21–14:52

The membranous part of the urethra travels anterior-inferiorly as it passes the external urethral sphincter, so increased force may be needed to account for this curvature when inserting the catheter in order to get into the bladder.

Increased force may also be needed during male catheterization when there is enlargement of the prostate or potential urethral strictures, but care should be taken not to apply too much force, as it can result in urethral injury.

So you see, the shorter female urethra, along with the lack of prostate, makes urethral catheterisation often easier in these individuals.

Now, in males, there are two other types of urethral injuries which are a result of pelvic trauma. Posterior urethral injuries can be the result of pelvic fracture and occur proximal to the bulb of the penis at the membranous urethra as we said before, or the prostatic urethra.

This results in urine or blood passing into the deep perineal pouch, and the fluid may pass superiorly through the urogenital hiatus to surround the prostate and the urinary bladder.

Anterior urethral injuries typically occur with straddle injuries, such as trauma from a bike seat, and are located within the spongy urethra.

Here, blood or urine instead escapes into the superficial perineal pouch. Fluid then may pass inferiorly into the scrotum or the penis, or superiorly into the inferior part of the anterior abdominal wall, deep to the membranous layer of the subcutaneous connective tissue.

Typically, urethral injuries cause inability to void, or painful voiding. Additionally there may be bleeding at the external urethral meatus as well as a high riding boggy prostate during digital rectal examination when a hematoma develops below it.

Now, if an urethral injury is suspected, urethral catheterization is contraindicated, because the catheter may pass through the ruptured part of the urethra, worsening the injury.

Other contraindications for transurethral catheterization include urethral obstruction, bladder neck masses, severe benign prostatic hyperplasia, and prostate cancer.

In these cases, suprapubic cystostomy may be done, in which a catheter is introduced through the anterior abdominal wall and into the bladder.

Suprapubic cystotomy14:52–15:31

Just a quick note here: the superior border of an empty bladder is at the same level as the superior border of the symphysis pubis.

So when trying to place a suprapubic cystostomy with an empty bladder, there is a very high risk of puncturing the peritoneal cavity.

But as the bladder fills with urine, it pushes the parietal peritoneum out of the way and puts the filled bladder directly against the anterior abdominal wall, which makes it easy to puncture without going into the peritoneal cavity.Okay, now let’s take a deep breath and have a quick quiz!

Quiz15:31–15:45

Can you name this procedure? How about this other procedure?All right, now let’s take a closer look at the penis, which is made of three long cylindrical bodies: the corpus spongiosum, surrounding the penile urethra, and the two corpora cavernosa, made of erectile tissue.

Penis anatomy15:45–16:36

The corpora cavernosa are wrapped in a fibrous coat called the tunica albuginea, and each corpus cavernosum is made up of blood-filled spaces called the cavernosal spaces.

The penis receives both somatic and autonomic innervation through the cavernous nerves, which innervate both the corpus spongiosum, and the corpora cavernosa.

Now, males have a bit of skin covering the head of the penis, and this is called the foreskin or prepuce. This prepuce protects the head of the penis and acts as a natural lubricant.

Typically, the prepuce is elastic and can be easily retracted over the head of the penis. Some males are born with a prepuce that fits tightly over the glands of the penis, making it difficult to retract, and that’s called phimosis.

Phimosis and paraphimosis16:36–17:29

This causes the oily secretions from the sebaceous gland of the prepuce to accumulate in the preputial sac, which is a space between the head of the penis and the prepuce.

These oily secretions have a cheesy consistency and they’re referred to as smegma. When these secretions build up, they can irritate the skin covering the penis.

Now, in some males, retracting the prepuce over the head of the penis constricts the neck of the glans penis, which causes blood and fluid to accumulate in the glans penis.

This decreases the blood supply to the tip of the penis, and causes it to swell up. This swelling prevents the prepuce to be drawn over the head of the penis, forming a condition called paraphimosis.

Circumcision17:29–17:49

Treatment of phimosis and paraphimosis can be done by circumcision, a surgical procedure that removes the prepuce and exposes the head of the penis.

Circumcision is also done as a religious practice in Islam and Judaism, but some individuals also choose to do it for non religious reasons.

Now, let’s look at penile fractures, which are urological emergencies that result from blunt trauma to an erect penis. Onset of this injury usually starts with individuals hearing a snapping sound, followed by significant pain, swelling, immediate loss of erection, and penile shaft hematoma.

Penile fractures17:49–18:23

Surgery is the mainstay of treatment in penile fractures, in which stitches are used to close the tear in the tunica albuginea and corpus cavernosum.

A retrograde urethrography can also be performed to assess for concomitant urethral injury. And finally, just a few words on malignant tumors of the scrotum and testes.

Malignant tumors18:23–19:23

These tumors usually spread through the lymphatic system. Remember that the testes start developing in the abdomen, and descend in the scrotum during the last months of intrauterine life.

So metastatic disease from the testes usually spreads to the paraaortic or retroperitoneal lymph nodes, and from here can spread and metastasize through the blood to the lungs, liver, brain, and bone.

Next is the scrotum, which is an extension of the anterolateral abdominal wall. In scrotal cancer, tumor cells usually pass to the superficial inguinal lymph nodes, which lie just inferior to the inguinal ligament, and from here, they drain into the deep inguinal lymph nodes.

Pelvic lymph nodes form a very complex network whose interconnections allow cancerous cells to spread in any direction, which makes it difficult to guess the specific route of cancer metastasis.All right, as a quick recap, pelvic fractures usually happen during high energy traumas such as car crashes or falling from height, and this can injure pelvic neurovascular structures and organs.

Review19:23–22:25

Benign prostatic hyperplasia typically affects the transitional zone, and this growth may obstruct the prostatic urethra, causing nocturia, dysuria, and urgency.

Treatment is usually done with TURP. Prostatic adenocarcinoma typically affects the posterior lobe or peripheral zone and usually metastasizes to lymph nodes, liver, lungs, brain and bone.

On DRE examination, BPH can cause the prostate to have a smooth, homogenous soft consistency, while adenocarcinoma may have a hard, irregular consistency.

Sometimes a prostatectomy can be performed, which is when parts of the prostate, all of the prostate, or the prostate and surrounding structures may be removed to treat prostatic disease such as benign prostatic hyperplasia and adenocarcinoma.

Now, male sterilization is done in a procedure called deferentectomy, famously known as vasectomy where the ductus deferens is ligated or excised, preventing sperm cells from being expelled.

Urethral catheterization describes sliding a soft, hollow tube through the urethra and into the bladder to drain urine in individuals who have difficulty voiding.

Urethral catheterization and pelvic fractures can cause anterior or posterior urethral injury, making urine and blood pass into the surrounding tissues.

If urethral injury is suspected, urethral catheterization is contraindicated to prevent further complications. A good alternative to urethral catheterization is suprapubic cystostomy, which is the insertion of a catheter through the anterior abdominal wall and into the bladder.

Now, some males are born with a prepuce that is firmly attached to the head of the penis, making it difficult to retract, and that’s called phimosis.

Paraphimosis, on the other hand, describes the swelling of the glans penis that prevents withdrawing the prepuce over the head of the penis.

Treating phimosis and paraphimosis is done by circumcision, which is a surgical procedure that removes the prepuce and exposes the head of the penis.

Blunt trauma to an erect penis can result in penile fracture. Erectile dysfunction is the inability to get or maintain an erection.

Causes can be psychological, but also include cardiovascular or endocrine disease. Erection is controlled by parasympathetic innervation, where ejaculation is controlled by sympathetic and somatic innervation.

Testicular cancer cells usually metastasize to paraaortic lymph nodes, and can further metastasize to lung, liver, brain and bone.

Scrotal cancer usually metastasizes to the superficial inguinal lymph nodes. testicular, cancer cells.

Usually metastasize to pair a or take lymph nodes and can further metastasize to Long liver, brain and bone cancer. Usually metastasize to The Superficial, inguinal lymph nodes.