Anatomy clinical correlates: Female pelvis and perineum

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Introduction0:00–0:39

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.
These anatomic differences are important to understand as they have large clinical implications in biological females for things such as fertility and childbirth.
So, why don’t we make like a baby and dive into the clinical correlates of the female pelvis and perineum head first! Speaking of babies, as cute and adorable as they are, pregnancy and childbirth can lead to a number of complications such as the risk of perineal or pelvic floor injury.

Perineal body and pelvic floor injury0:39–2:17

The pelvic floor holds the pelvic organs in a stable position, and during childbirth the pelvic floor makes every effort to support the fetal head.
During delivery the fetal head stretches the pelvic floor, frequently resulting in injury to the perineum, levator ani, and ligaments of the pelvic viscera.
Specifically, injury to the pubococcygeus and the puborectalis muscles of the levator ani often occur. These muscles surround and support the urethra, vagina, and anal canal.
So injury to these muscles can lead to decreased support for the vagina, bladder, uterus, or rectum. Another important structure that can be damaged is the perineal body, which is the fibromuscular center point of the perineum, that serves as an attachment point for structures such as the muscles of the levator ani, fibers from the external urethral sphincter and urethrovaginal sphincter, and the external anal sphincter.
Damage to the pelvic floor or perineal body can lead to urethral hypermobility and stress urinary incontinence, which is when drops of urine come out when intra abdominal pressure increases.
Unfortunately, this can occur with coughing, lifting, laughing, and constipation. Also, if the injury to the pelvic floor is severe enough, a pelvic organ may lose its support and herniate into the vagina, called pelvic organ prolapse.
Examples of this would be prolapse of the bladder into the anterior vaginal wall, the rectum into the posterior vaginal wall, or the uterus through the vaginal orifice.

Pudendal nerve injury2:17–3:17

Childbirth can also cause damage to the pudendal nerve, which can be stretched and damaged along its course near the ischial spine, especially during prolonged labour, when there’s pressure on the pelvic floor for a longer period of time.
The pudendal nerve provides motor and sensory innervation to the perineal region, so damage to it can cause weakness in the perineal muscles.
This can lead to inability to control bowel movements, leading to fecal incontinence. Individuals may also experience urinary incontinence, as well as perineal pain, and sexual dysfunction.
Now, trying to prevent injury to the pelvic floor or management of stress urinary incontinence can be done through Kegel exercises, which aim to strengthen the pelvic floor muscles by contracting and relaxing the levator ani muscles a few times each day, which is similar to the contraction when trying to stop peeing midstream.
Regularly performing these exercises lowers the risk of them getting injured during childbirth, which lowers the risk of having a stress incontinence.

Episiotomy3:17–4:30

On the other hand, sometimes an episiotomy can be performed during childbirth. This is an intentional incision of the female perineum and the posterior vaginal wall.
This incision enlarges the opening for the baby to pass through, so it reduces the risk of severe perineal lacerations and helps accelerate delivery during the second stage of labor.
Episiotomy is typically done in cases of fetal distress or a large baby that is stuck and can’t get out. There are two main ways to perform an episiotomy.
First is median episiotomy, which runs from the posterior vaginal wall to the perineal body, and tries to spare the external anal sphincter and rectal muscles.
This type of episiotomy is done because it’s thought that the fibrous tissue that develops during healing is similar to that of the already tendinous perineal body.
However, even though care should be taken not to injure the perineal body, median episiotomy can cause damage to the perineal body.
Next is mediolateral episiotomy, which runs at 45 degrees from the middle of the vaginal opening to the buttocks. This type has much lower risk of injuring the anal muscles, but it can potentially cause more pain, more bleeding, and a more difficult repair.

Anesthesia4:30–4:44

Now, childbirth can be painful, but for those soon to be mothers - don’t worry, because there are different anesthetic techniques which can be used for pain control.
These techniques include general and regional anesthesia. General anesthesia makes the mother become unconscious and is often used during emergency procedures, as it completely eliminates the pain and discomfort of delivery.

General anesthesia4:44–4:58

Here, both the mother and the baby are continuously monitored, and childbirth happens passively. Next is regional anesthesia, which is used for mothers who wish to participate in the delivery, but don’t want to experience the pain.

Regional anesthesia4:58–5:12

There are three types of regional anesthesia; spinal anesthesia, epidural block, and pudendal nerve block. With spinal anesthesia, the anesthetic agent is introduced with a needle into the subarachnoid space at the L3-L4 vertebral level and anesthesia usually occurs within 1 minute.

Spinal anesthesia5:12–6:19

The spinal anesthesia produces a temporary anesthesia below the waist, so individuals can’t feel pain in the perineum, pelvic floor and birth canal, or the sensation of uterine contractions, and the motor and sensory functions of the entire lower limbs.
This means that the mother is conscious, but they depend on electronic monitoring of uterine contractions to coordinate pushing.
However, bear in mind that with extended labor or inadequate anesthesia, it’s almost impossible to readminister the spinal anesthesia.
Furthermore, the anesthetic agent ascends proximally and circulates into the cerebral subarachnoid space in the cranial cavity when the individual lies flat, so the most common side effect of this type of anesthesia is a severe headache.Patients may also experience a decrease in blood pressure during administration of the anesthesia, as well as pain around the injection site.

Epidural block6:19–7:57

Next is the epidural block, which uses a catheter to inject an anesthetic agent into the epidural space within the vertebral canal, and does not pierce the dura or subarachnoid mater to enter the subarachnoid space like the spinal anesthetic.
Similar to the spinal anesthetic, this method affects all the nerves below the level of administration, especially trying to target the S2-S4 nerve roots.
This causes anesthesia of the superior vagina and the uterine cervix, as well as the structures supplied by the pudendal nerve which include the entire birth canal, the pelvic floor, and the majority of the perineum.
Epidural anesthesia can be titrated based on delivery, but is typically not as potent as spinal anesthesia, so the individual can often still feel and move their legs.Now, the body of the uterus lies above the pelvic pain line, so visceral pain from the uterine body will travel with sympathetic fibers to the spinal cord at the level of T10 to L1, where epidural anaestheia is usually given at the L2 to L4 level.
But since the epidural space is a continuous space along the length of the vertebral canal, the anaesthetic agent can travel superiorly and often blocks those sympathetic pathways at the T10 to L1 level, which is great for blocking all of the relevant pain pathways in labour!
Furthermore an epidural block when done correctly doesn’t cause a headache as the spinal and epidural spaces are not continuous.
However, headache may be a potential side effect if the needle is inserted too far and penetrates the dura. Epidural anaesthetic must be administered in advance of delivery as it takes time to become effective.Finally we have the pudendal nerve block, which is used when a woman has progressed too far into labour and is unable to receive an epidural.

Pudendal nerve block7:57–8:58

Here a needle is used to inject the anesthetic agent into the tissues that surround the pudendal nerve. This is done by palpating the ischial spines intravaginally, and injecting the anesthetic intravaginally, through the sacrospinous ligament, medial to the ischial spine.
This anesthetizes the area supplied by the pudendal nerve, which includes some of the area supplied by dermatomes S2-S4 and the lower quarter of the vagina.
This helps in the second stage of labor, or when the baby is descending through the birth canal. Now, the upper part of the vagina, the uterine cervix, and the uterine body are not anesthetized, so the mother still feels uterine contractions during delivery.
Complications include incidental injection or injury to the pudendal artery and vein which run in close proximity to the nerve, causing a hematoma.
Okay, now let’s take a deep breath and have a quick quiz! Can you name each of these types of regional anesthesia?

Quiz8:58–9:30

That’s right, the first area is where spinal anesthesia and epidural blocks can be administered. Both spinal and epidural anesthesia will block everything inferiorly, where spinal anesthesia works quicker and is typically more potent.
Yup, next is the pudendal nerve block. Note how the anesthetic agent is pushed into the tissues surrounding the pudendal nerve.
Alright, now, some bleeding is normal after delivery. However, when there’s more bleeding than expected, this is called postpartum hemorrhage, or PPH for short.

Postpartum hemorrhage9:30–11:51

Postpartum hemorrhage is defined as losing more than 500 milliliters of blood in a vaginal delivery, or more than 1000 milliliters in a cesarean section.
There are two types of postpartum hemorrhage; primary PPH, which happens in the first 24 hours of delivery, and secondary PPH, which happens after the first day up to six weeks after delivery.
The main causes of postpartum hemorrhage can be remembered using the 4 T’s. Lack of uterine Tone, Trauma such as lacerations or uterine damage, Thrombin which refers to issues with coagulation, and Tissue which refers to retained products of conception.
Okay, postpartum hemorrhage is mainly caused by uterine atony which is loss or uterine tone, one of our four T’s, and happens when the muscles of the uterus fail to contract after delivery.
This contraction is necessary to clamp the blood vessels shut where the placenta was attached, preventing bleeding. Other causes of postpartum hemorrhage include trauma to the birth canal, retention of the placenta, and bleeding disorders.Treatment of postpartum hemorrhage involves giving fluids, stopping the bleeding, as well as identifying and stopping the cause of the bleeding.
Treatment starts with giving fluids, which replaces lost blood, while properly examining and repairing any visible lacerations to the birth canal.
If bleeding persists, manual massage of the uterus is tried, which stimulates muscles of the uterus to contract. If this does not control the bleeding, medications that stimulate muscles of the uterus to contract, such as oxytocin, may be used.
Other medications such as ergot alkaloids and tranexamic acid may also be used. Then, if these options fail to stop the bleeding, surgery is indicated.
The uterus is supplied by branches of the internal iliac arteries, namely the uterine arteries, so bilateral ligation of the uterine arteries or the internal iliac arteries is done to stop hemorrhaging.
If the internal iliacs are ligated, the uterus still has a blood supply due to collateral blood flow from the ovarian arteries.
Finally, if bleeding cannot be controlled, a hysterectomy may be done. Simply put, a hysterectomy describes the removal of the uterus vaginally, laparoscopically, or abdominally.

Hysterectomy11:51–12:47

Conditions that may require hysterectomy in addition to postpartum hemorrhage include uterine fibroids, endometriosis, adenomyosis, prolapse, and cancers of the reproductive organs.
There are different types of hysterectomy which can be used depending on the type of disease and patient factors; First is a radical hysterectomy, which is the removal of the uterus with the surrounding parametrium including the round, broad, cardinal, and uterosacral ligaments, the cervix, and the upper one third to one half of the vagina.
Next is a total hysterectomy, which is the removal of the entire uterus and the cervix. Finally is a partial or supracervical hysterectomy, which is the removal of the uterus, sparing the cervix.
Alright, now surgical intervention of the uterus and its surrounding structures, such as a hysterectomy, carries a risk of injuring the ureters.

Ureter injury12:47–13:43

This is due to the course of the ureters as they enter the pelvis towards the bladder. Once past the pelvic brim, they cross anterior to the bifurcation of the common iliac arteries, and descend posterior to the ovarian arteries, then travelling posterior to the uterine vessels near the anterolateral surface of the internal cervical os.
This puts the ureters at risk of getting ligated, clamped, or transected during a hysterectomy when the uterine vessels are ligated.
A good way to remember this relationship is the phrase ‘bridge over troubled water’, where the ‘troubled water’ is the filtered urine we think about going through our ureters, and the ‘bridge’ is the uterine vessels.
Furthermore, the ureters can also be damaged during an oophorectomy from ligation of the ovarian arteries during removal of the ovaries.
Alright, let’s talk about the obturator nerve, which arises from the L2-L4 lumbar spinal nerves. It travels posteromedial to the iliopsoas muscle, and passes through a small opening in the obturator membrane, called the obturator canal.

Obturator nerve injury13:43–14:25

These branches enter the thigh and branch into an anterior and posterior division to supply the adductor muscles and overlying skin of the medial thigh.
Injury to the obturator nerve can occur during trauma, childbirth and pelvic surgeries such as bladder cancer removal. This can lead to weakness of thigh adduction and loss of sensation on the medial thigh.

Quiz14:25–14:36

Okay, now let’s take a deep breath and see if you can label these important structures!! Now, let’s look at a condition called ectopic pregnancy, which has the potential to cause a surgical medical emergency.

Ectopic pregnancy14:36–15:33

An ectopic pregnancy is when the fertilized ovum implants in a place other than the uterus. The most common place an ectopic pregnancy can occur is the ampulla of the fallopian tubes, however implantation can also occur in the fimbria, infundibulum, fallopian tube isthmus, or abdomen.
This can result in rupture of the fallopian tube, and severe hemorrhage into the peritoneal cavity causing peritonitis. Clinical features of an ectopic pregnancy include severe abdominal pain, amenorrhea, and vaginal bleeding, and diagnosis is confirmed with ultrasound.
It is important to note that the appendix lies close to the right ovary and fallopian tube, which explains why right-sided ruptured ectopic pregnancies can be misdiagnosed as acute appendicitis.
Alright, now let's move on to fistulas which are defined as an abnormal connection between two body parts, and can often occur between the different organs of the pelvis.

Fistulas15:33–16:52

Fistulas can occur between the vagina and the surrounding organs such as the bladder, urethra, and rectum. They are typically caused by an injury or prolonged inflammatory process, weakening the walls of these organs causing fistulas to form.Now fistula formation between the bladder and the vagina is called a vesicovaginal fistula, and between the urethra and vagina its called a urethrovaginal fistula.
These can occur during labour, where weakness or tears in the vaginal wall may occur along the bladder and urethra. These two fistulas can result in urine entering the vagina, potentially leading to pain or infection in the genital area, as well as abdominal pain and pain during intercourse.
Another type of fistula is between the rectum and the vagina, called a rectovaginal fistula. Rectovaginal fistulas can also result from childbirth and pelvic surgery, as well as inflammatory bowel diseases such as Crohn's disease.
This can lead to patients presenting with gas and fecal matter passing through the vagina, and may also result in pain and infection.

Ovarian torsion16:52–17:58

Alright, now let’s talk about ovarian or adnexal torsion. The ovaries are held in place by the suspensory ligament of the ovary, also called the infundibulopelvic ligament.
Travelling through this ligament is the ovarian artery, vein and nerve plexus which go on to innervate the ovary. Ovarian torsion occurs when the ovaries twist around the suspensory ligament of the ovary which holds it in place, in addition to twisting around the ovarian ligament as well.
When the blood supply to the ovary is completely occluded, the ovary becomes edematous and ischemic, leading to necrosis and bleeding which can cause sudden severe unilateral pelvic pain and nausea, and may also induce vomiting and fever.
Typically, ovarian torsions happen when the ovaries are larger than normal, which may be caused by an ovarian mass, such as a cyst or a tumor, or by fertility treatments, which aim to induce ovulation.
Also, being pregnant increases the risk of ovarian torsion. Complications of ovarian torsion include infection, bleeding, and infertility.
Now, let’s wrap up these correlations by discussing the greater vestibular or Bartholin’s glands, which are two pea-shaped glands that lie on each side of the vaginal vestibule, posterolateral to the vaginal orifice.

Bartholin gland cyst17:58–18:50

These glands secrete mucus to lubricate the vagina during sexual arousal through ducts that open into each vestibule of the vaginal orifice.
Now, the ducts of these glands may become blocked, which causes mucus to build-up inside the gland, forming a Bartholin gland cyst.
This cyst causes the gland to swell up, which makes it visible and palpable near the vaginal opening. The accumulated mucus may cause infection of the Bartholin’s glands resulting in an abscess which can lead to pain around the vaginal opening, pain during intercourse, discomfort while walking, as well as fever.Okay, now let’s take one last quiz before doing a recap!

Quiz18:50–19:05

Here are the two common fistulas that may happen in the female pelvis. Can you name each of these types?Alright, as a quick recap.

Review19:05–21:01

Injuries to the structures of the pelvic floor such as the levator ani and perineal body during delivery may cause stress urinary incontinence and pelvic organ prolapse.
Childbirth can also cause pudendal nerve injury, leading to loss of motor and sensory function of the perineal region.An episiotomy can be done to help prevent severe perineal lacerations and assist delivery during fetal distress.
The pain and discomfort of delivery may be reduced using anesthetic techniques. These include general anesthesia, spinal anesthesia, epidural block, and pudendal nerve block.
A common complication of childbirth is postpartum hemorrhage, which is an abnormal increased bleeding after delivery and is typically caused by uterine atony.
A hysterectomy is surgical removal of the uterus, and can be done vaginally, laparoscopically, or abdominally, and can be either radical, complete, or partial.
In some surgeries of the pelvis, such as a hysterectomy or oophorectomy, the ureters are at high risk of getting ligated, clamped or transected.
Injuries to the obturator nerve causes weakness of thigh adduction and loss of sensation of the medial thigh. An ectopic pregnancy is when the fertilized ovum implants in a place other than the uterus, most commonly the ampulla of the fallopian tubes.
The most common fistulas in females are vesicovaginal, urethrovaginal, and rectovaginal fistulas. Ovarian or adnexal torsion is when the ovaries twist around the suspensory ligament of the ovary and the ovarian ligament, causing severe pelvic pain, nausea, and vomiting.
Finally, when the Bartholin gland ducts become obstructed, that causes mucus to build up,
Anatomy clinical correlates: Female pelvis and perineum | Osmosis