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SECTION 5
Pelvis and Perineum

Question 1

A 13-year-old boy presents to the emergency department after acute onset of right hip pain
as he was preparing to kick a soccer ball. After feeling a pop, he was unable to bear weight
on the leg, and the pain was described as being from the groin area. No bone or
neurovascular deficits were found on examination; however, the pain was easily
regenerated with any non-passive external rotation of the leg, suggesting a muscle strain or
tear. Which of the following muscles is likely injured in this patient?

A. Obturator internus
B. Tensor fasciae latae
C. Gluteus medius
D. Gluteus minimus
E. Coccygeus

Answer: A

A. Obturator internus
Explanation: The obturator internus muscle is located in the groin region on the interior
surface of the obturator membrane, coinciding with the location of the pain. This muscle
inserts on the medial surface of the greater trochanter and provides external rotation when
stimulated. Thus, when this muscle is injured, pain on external rotation of the thigh at the
hip would be generated.

B. Tensor fasciae latae

Explanation: The tensor fasciae latae muscle is located on the most lateral portions of the
hip and thigh, serving as a thigh flexor, medial rotator, and abductor. External rotation
should not involve this muscle.

C. Gluteus medius
Explanation: The gluteus medius muscle serves as a thigh abductor and medial rotator.
External rotation should not involve this muscle.

D. Gluteus minimus
Explanation: The gluteus minimus muscle works in concert with the gluteus medius in
maintaining thigh abduction and also serves as a medial rotator of the thigh. External
rotation should not involve this muscle.

E. Coccygeus
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Explanation: The coccygeus muscle is located on the floor of the pelvis between the levator
ani anteriorly and the sacrospinous ligament posteriorly. This muscle serves to pull the
coccyx forward after defecation and does not participate in thigh rotation whatsoever.

Question 2

An 18-year-old man presents to the clinic with issues of erectile dysfunction. You find out
that 2 weeks prior he slipped on the pedal of his bike and slammed his ischiopubic region
of his perineum on the top tube of his bicycle. He had some swelling that has mostly
subsided, and there is now a bruise in the location of the impact. Based on this presentation,
you are concerned that he has injured the internal pudendal artery, which supplies all of the
blood to his penis. Which of the following lists the three branches of the internal pudendal
artery that supply blood to the penis?

A. Bulbo-urethral, dorsal, and cavernosal arteries

B. Bulbo-urethral, ventral, and cavernosal arteries
C. Dorsal, ventral, and cavernosal arteries
D. Cavernosal, internal pudendal, and dorsal arteries
E. Cavernosal, superior vesical artery, and bulbo-urethral arteries

Answer: A

A. Bulbo-urethral, dorsal, and cavernosal arteries

Explanation: The internal pudendal artery branches into three main arteries: the bulbo-
urethral, the dorsal, and the cavernosal arteries that supply blood to the penis. The internal
pudendal artery runs within Alcock’s canal that lies in direct apposition to the ischiopubic
ramus, where the patient’s blunt impact occurred.

B. Bulbo-urethral, ventral, and cavernosal arteries

Explanation: There is no ventral artery of the penis. The bulbo-urethral and cavernosal
arteries are two of the branches of the internal pudendal artery.

C. Dorsal, ventral, and cavernosal arteries

Explanation: There is no ventral artery of the penis. The dorsal and cavernosal arteries are
two of the branches of the internal pudendal artery.

D. Cavernosal, obturator artery, and dorsal arteries

Explanation: The obturator artery is a branch off the internal iliac artery separate from the
internal pudendal artery. It does not supply blood to the penis.

E. Cavernosal, superior vesical artery, and bulbo-urethral arteries

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Explanation: The superior vesical artery supplies numerous branches to the superior
portion of the bladder as well as portions of the ureter. The superior vesical artery is not a
branch of the internal pudendal artery, and does not supply blood to the penis.

Question 3

A 75-year-old man presents to the emergency department with significant lower abdomen
pain and back pain. An arteriogram confirms the patient has an embolic occlusion of the
posterior division of his internal iliac artery. It is hypothesized that the loss of blood flow
to a given region is causing his pain. Which of the following structures would likely have
a loss of blood flow?

A. Vagina
B. Bladder
C. Quadriceps femoris
D. Psoas major
E. Rectum

Answer: D

A. Vagina
Explanation: The vagina receives blood from the vaginal artery, which is a branch of the
anterior division of the internal iliac artery.

B. Bladder
Explanation: The bladder receives blood from the superior and inferior vesicular arteries,
which are both branches of the anterior division of the internal iliac artery.

C. Quadriceps femoris
Explanation: The quadriceps femoris muscles receive their blood supply from the femoral
artery. The femoral artery is derived from the external iliac artery and thus would not be
affected by occlusion in either division of the internal iliac artery.

D. Psoas major
Explanation: The psoas major muscle receives its blood supply from the iliolumbar artery.
This iliolumbar artery is a branch of the posterior division of the internal iliac artery; thus
a clot in the posterior division would affect blood supply to this muscle.

E. Rectum
Explanation: The rectum receives its blood supply from the superior rectal artery, a branch
of the inferior mesenteric artery, and the middle rectal artery, a branch of the anterior
division of the internal iliac artery. Thus the rectum would not be affected by occlusion in
the posterior division of the internal iliac artery.
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Question 4

A 30-year-old man presents to the emergency department after sustaining a significant

pelvic fracture. You are worried about an injury to the urethra, as this commonly occurs in
this type of injury. A urethral radiograph is taken in which contrast dye is injected into the
opening of the urethra, and the images are taken to see if any dye leaks out, which would
indicate a urethral injury. For this patient, dye leaks out of the damaged area of the urethra,
but the dye is confined to the penis alone. Which of the following facial layers must be
intact to keep the dye confined to the penis only?

A. Buck’s fascia
B. Dartos fascia
C. Colles’ (superficial perineal) fascia
D. Scarpa’s fascia
E. Camper’s fascia

Answer: A

A. Buck’s fascia
Explanation: If there is injury to the penile urethra and Buck’s fascia is intact, radiographic
dye, blood, and urine would be confined within the penis alone, as Buck’s fascia (deep
fascia of the penis) contains the urethra along with the three erectile bodies of the penis.

B. Dartos fascia
Explanation: Dartos fascia is a layer of smooth muscular fiber that lies outside Buck’s
fascia. It is continuous with Scarpa’s fascia on the abdominal wall. Because it is continuous
with these compartments, radiographic dye, blood, and urine would not be retained within
the penis alone in urethral injury.

C. Colles’ (superficial perineal) fascia

Explanation: Colles’ fascia, also known as the perineal fascia, separates the skin and
subcutaneous fat from the superficial perineal pouch. This pouch is a compartment of the
perineum and would not serve as a limiting fascial layer confining the radiographic dye to
the penis.

D. Scarpa’s fascia
Explanation: Scarpa’s fascia is the deep fascial layer of the anterior abdominal wall. It is
located superficial to the external oblique muscle and deep to Camper’s fascia. Scarpa’s
fascia is continuous with Dartos fascia in the perineum. Leakage of dye under this layer
would not be confined to the penis.

E. Camper’s fascia
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Explanation: Camper’s fascia is the superficial fascial layer of the anterior abdominal wall.
It is located deep to the skin and subcutaneous fat and superficial to Scarpa’s fascia.
Leakage of dye under this layer would not be confined to the penis.

Question 5

A 2-day-old infant remains in the ICU due to an inability to pass stool and frequent episodes
of emesis of a brown substance. A rectal biopsy is taken and a diagnosis of Hirschsprung’s
disease is made. This disease is characterized by the failure of the postganglionic neurons
of myenteric plexus to develop correctly in the walls of the colon, preventing the affected
portions of the colon from relaxing and allowing the passage of stool. From which of the
following nerves are the ganglia of the sigmoid colon and rectum derived?

A. Vagus nerve
B. Lumbar splanchnic nerves
C. Pelvic splanchnic nerves
D. Thoracic splanchnic nerves
E. Pudendal nerve

Answer: C

A. Vagus nerve
Explanation: The vagus nerve does send some visceral motor efferent innervation to the
smooth muscle of the transverse colon, but it does not populate the myenteric plexus of the
colon.

B. Lumbar splanchnic nerves

Explanation: The lumbar splanchnic nerves do not provide the ganglia for the myenteric
plexus of the sigmoid colon and rectum.

C. Pelvic splanchnic nerves

Explanation: The pelvic splanchnic nerves provide the parasympathetic innervation for the
ganglia located in the colon wall.

D. Thoracic splanchnic nerves

Explanation: The thoracic splanchnic nerves travel inferiorly to provide sympathetic
innervation to the abdomen, but they do not provide the ganglia for the myenteric plexus
of the sigmoid colon and rectum.

E. Pudendal nerve
Explanation: The pudendal nerve does not provide parasympathetic innervation to any part
of the digestive tract.
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Question 6

A motor vehicle accident injures a 20-year-old man who was riding in the passenger seat.
In the emergency department he is found to be hypotensive and complains of pelvic pain.
Gentle bimanual compression and distraction of the pelvis reveals instability (pelvic
springing) that suggests pelvic fracture. Anteroposterior radiographs show separation
(diastasis) of the pubic symphysis and sacro-iliac joints, with external rotation of the
hemipelves (open-book pelvis). Angiography reveals that the bleeding is caused by
laceration of the branch of the internal iliac artery, which runs near the sacro-iliac joint and
then ascends into the false (greater) pelvis. What is this branch of the internal iliac artery?

A. Iliolumbar artery
B. Inferior gluteal artery
C. Internal pudendal artery
D. Lateral sacral artery
E. Obturator artery

Answer: A

A. Iliolumbar artery
Explanation: The iliolumbar artery is a branch of the posterior trunk of the internal iliac
artery. It crosses the sacro-iliac joint and ascends to supply muscles of the posterior
abdominal wall. It is vulnerable to injury in cases of sacro-iliac joint separation.

B. Inferior gluteal artery

Explanation: The inferior gluteal artery is most often a branch of the anterior trunk of the
internal iliac artery. It passes through the greater sciatic foramen to reach the gluteal region
and is most at risk in fractures of the greater sciatic notch.

C. Internal pudendal artery

Explanation: The internal pudendal artery is a branch of the anterior trunk of the internal
iliac artery. It passes into the gluteal region via the greater sciatic foramen and then through
the lesser sciatic foramen to reach the perineum. It is most at risk in fractures of the greater
sciatic notch.

D. Lateral sacral artery

Explanation: The lateral sacral artery arises from the posterior trunk of the internal iliac
artery medial to the sacro-iliac joint. It courses inferiorly on the anterior surface of the
piriformis muscle and sends branches into the anterior sacral foramina. It is at greatest risk
in pelvic fractures through the foramina.

E. Obturator artery
Explanation: The obturator artery is a branch of the anterior trunk of the internal iliac
artery. It courses anteriorly and passes through the obturator canal to enter the medial thigh.
It is at risk in fractures of the pubic rami.
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Question 7

A 25-year-old woman comes to the emergency department after 6 hours of severe right
lower quadrant pain. Abdominal examination reveals tenderness in the right lower
quadrant. A tender fullness is felt in the right adnexal region on bimanual pelvic
examination. Ultrasound of the abdomen reveals an ovarian mass approximately 10 cm in
diameter. Exploratory laparoscopy identifies a large dermoid cyst that completely replaces
the right ovary. The cyst has produced complete torsion of the ovary. A decision is made
to remove the ovary. In which of the following locations will the ovarian vessels be found?

A. In the suspensory ligament of the ovary

B. In the recto-uterine fold
C. In the round ligament
D. In the median umbilical fold
E. In the transverse cervical (or cardinal) ligament

Answer: A

A. In the suspensory ligament of the ovary

Explanation: These vessels enter the pelvis by coursing over the iliac vessels just lateral to
the ureters.

B. In the recto-uterine fold

Explanation: This fold runs between rectum and uterus and is posterior and deep to the
field of dissection.

C. In the round ligament

Explanation: The round ligament runs from the uterus to the internal inguinal ring.

D. In the median umbilical fold

Explanation: This is the remnant of the obliterated urachus, and it connects the dome of
the urinary bladder to the umbilicus.

E. In the transverse cervical (or cardinal) ligament

Explanation: This ligament contains the uterine vessels.

Question 8

An 85-year-old woman complains of pain along the medial thigh. On examination, she is
cachectic and frail. There is an ovoid patch of decreased sensation to pinprick on the medial
thigh that is approximately 20 cm long and 15 cm in the transverse diameter. The remainder
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of the physical examination is negative, with the exception of a tender mass detected on
the ipsilateral wall of the vagina on pelvic examination. Which of the following is the most
likely diagnosis?

A. Femoral hernia
B. Lumbar hernia
C. Obturator hernia
D. Indirect inguinal hernia
E. Direct inguinal hernia

Answer: C

A. Femoral hernia
Explanation: A femoral hernia is felt just below the inguinal ligament. It does not cause
pain and numbness as described.

B. Lumbar hernia
Explanation: A lumbar hernia manifests through the back in the lumbar triangle. It does
not cause pain and numbness as described.

C. Obturator hernia
Explanation: An obturator hernia may be felt as a mass on vaginal examination. Pressure
on the obturator nerve causes characteristic numbness and pain in the distribution of this
nerve.

D. Indirect inguinal hernia

Explanation: An indirect inguinal hernia manifests as a mass in the groin, above the
inguinal ligament. It does not cause pain and numbness as described.

E. Direct inguinal hernia

Explanation: A direct inguinal hernia manifests as a mass in the groin, above the inguinal
ligament, and it does not cause pain and numbness as described.

Question 9

During an uncomplicated vaginal delivery, a 23-year-old woman receives a bilateral

pudendal nerve block to provide anesthesia of the lower vagina and the perineum. To
perform this procedure, the obstetrician inserts his finger into the vagina, palpates a bony
feature, passes the needle transvaginally, and uses his palpating finger as a guide to deliver
the anesthetic just medial to the landmark. Which bony feature is used as the landmark for
performing a transvaginal pudendal block?
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A. Coccyx
B. Ischial spine
C. Ischial tuberosity
D. Pectineal line
E. Sacral promontory

Answer: B

A. Coccyx
Explanation: The coccyx is the midline bony feature that marks the posterior boundary of
the perineum. The pudendal nerve enters the perineum anterior to this point, near the lateral
boundary of the perineum, and proceeds anteriorly from there. Only the terminal portion
of its inferior rectal (inferior anal) branch lies in the vicinity of the coccyx.

B. Ischial spine
Explanation: The pudendal nerve enters the perineum through the lesser sciatic foramen,
passes superficial to the sacrospinous ligament near its attachment to the ischial spine, and
proceeds anteriorly within the pudendal canal on the medial side of the obturator internus
muscle. The ischial spine can be palpated transvaginally, and anesthetic that is delivered to
that region provides effective perineal anesthesia (see Plate 391).

C. Ischial tuberosity
Explanation: The ischial tuberosity is not readily palpated transvaginally, but it can be
easily palpated through the skin of the perineum. It is used as the bony landmark for
pudendal block when anesthetic is delivered transcutaneously rather than transvaginally.
Such an approach is necessary, for example, when the fetal head is engaged and blocks the
transvaginal approach. The pudendal nerve lies deep to the sacrotuberous ligament near its
attachment to the ischial tuberosity.

D. Pectineal line
Explanation: The pectineal line is the sharp superior border of the superior pubic ramus. It
is part of the linea terminalis, which is part of the pelvic inlet (pelvic brim). Because it lies
superior to the pelvic diaphragm, it is in the pelvis rather than in the perineum, where a
pudendal block is performed.

E. Sacral promontory
Explanation: The sacral promontory is the superior border of the anterior aspect of the
body of the S1 vertebra. It is part of the pelvic inlet and therefore lies in the pelvis rather
than in the perineum, where a pudendal block is performed. The conjugate diameter of the
pelvic inlet (an important obstetric diameter) is measured from the sacral promontory to
the superior border of the pubic symphysis.

Question 10
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A 72-year-old man is embarrassed by unexpected dribbling of urine. During voluntary

urination, he produces only a weak urine stream. A cystometrogram shows suppressed
bladder tonus at 300 mL volume, a lack of spontaneous micturition contractions when the
bladder volume is 500 mL, and fluid eventually leaking around the catheter when the
volume exceeds 700 mL. He experiences no discomfort during the entire test. Which of the
following mechanisms best explains this patient’s condition?

A. Pelvic afferents from the bladder are nonfunctional

B. Pontine-descending inhibitory inputs are blocked
C. Psychologic factors dominate the loss of bladder control
D. Pudendal nerve efferents to the external sphincter are severed
E. Sympathetic innervation of the bladder via the hypogastric nerve is disrupted

Answer: A

A. Pelvic afferents from the bladder are nonfunctional

Explanation: Poor innervation is suggested by the flaccid or atonic bladder and the fact
that the patient can hold large volumes of urine without pain. The latter symptom points
specifically to denervation of sensory afferent nerves. “Dribbling” also suggests abnormal
neural activity, specifically the lack of an operative micturition reflex, which makes it
impossible to excrete urine except by overflow dribbling at higher bladder volumes and
pressures. Bladder stimulation techniques will provide the best solution to this patient’s
problem. An alternative is urine drainage by urethral/bladder catheterization; however,
abdominal pressure would have to be raised to help collapse the bladder.

B. Pontine descending inhibitory inputs are blocked

Explanation: Blocked descending inputs from the brain stem may play a role in this
patient’s inability to produce a stream of urine but would not suppress bladder tone or
spontaneous micturition contractions.

C. Psychologic factors dominate the loss of bladder control

Explanation: Psychologic factors are rejected because the micturition reflex can be neither
voluntarily nor involuntarily suppressed.

D. Pudendal nerve efferents to the external sphincter are severed

Explanation: Impaired functioning of pudendal nerves and disrupted sympathetic efferents
are each precluded as a cause of the patient’s symptoms because they have little effect on
the micturition reflex, the lack of which may explain the loss of bladder tonus and
suppressed bladder sensation.

E. Sympathetic innervation of the bladder via the hypogastric nerve is disrupted

Explanation: Impaired functioning of pudendal nerves or disrupted sympathetic efferents
are each precluded as a cause of the patient’s symptoms because they have little effect on
the micturition reflex, the lack of which may explain the loss of bladder tonus and
suppressed bladder sensation.
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