Clinical Cases - Pelvic Neurovasculature
A 50-year-old man underwent surgery to remove cancer from his lower rectum. The surgery successfully removed the tumor; however, following the surgery, he began to experience urinary retention, erectile impotence, and ejaculatory difficulty. Prior to the surgery, the patient's sexual function was "normal."
Questions to consider:
- What structure was likely damaged by the surgery?The nerves of the inferior hypogastric plexus, which course on either side of the rectum, were probably damaged during the surgery.
- What other functions might be disturbed in this sort of injury in a male patient?The functions in a male which may be affected include micturition (resulting in urinary retention), erection (erectile impotence), ejaculation (ejaculatory impotence), intestinal motility especially in the rectum (reduced motility or paralysis, causing constipation), and functioning of the internal anal sphincter.
- What nerves supply the stimuli for erection? For ejaculation?Erection depends on stimuli from parasympathetic neurons carried to the inferior hypogastric plexus primarily by the pelvic splanchnic nerves. Inasmuch as contraction of the bulbospongiosus and ischiocavernosus muscles contribute to maintenance of erection, the pudendal nerve may also contribute. Ejaculation and subsidence of erection are controlled by sympathetic nerves which enter the inferior hypogastric plexus from the hypogastric nerve and possibly the sacral trunk.
- What functions might be disturbed in a female patient with a similar injury?In addition to difficulties related to micturition, defecation, and sexual function (erection of the clitoris and orgasm), uterine contraction/inhibition and vasoconstriction, which are modulated by the autonomic nervous system, may be affected; however, these functions are complicated by hormonal controls.
- Where might metastases from a rectal cancer be found?Lymphatic metastases are likely to appear in the pararectal, internal iliac, or sacral lymph nodes. Blood-borne metastases are commonly found in the liver, lungs, and bones primarily, but also in the serosal membrane of the peritoneal cavity, the brain, and other locations. Recall that blood drainage from the inferior and middle rectal veins is to the internal iliac veins and the inferior vena cava, and drainage from the superior rectal vein is through the inferior mesenteric vein and the portal system.
A 22 year old male arrives in the ED by ambulance from an outside hospital. The patient, a bouncer at a local bar, is complaining of severe pain after being stabbed in the groin with a pool cue. He states he was stabbed while trying to break up a fight; he remembers hearing the pool cue break. CT films from the outside hospital show a large, left-sided retroperitoneal hemorrhage. The outside hospital was unable to find the source of the hemorrhage and transported him to U of M for further treatment.
Additional CTs confirm the presence of a large left-sided retroperitoneal hematoma with some extraperitoneal blood in the pelvis. The hematoma has displaced his left kidney anteriorly and his retrosigmoid colon to the right. A CT also shows the end of the wooden pool cue (along with its plastic tip), still lodged in the patient's left inguinal area! Several other tests are ordered: a cystogram shows the bladder intact but elongated and displaced to the right by the hematoma; a venogram shows no damage to the left femoral or iliac veins.
The patient is taken to the OR to have the rest of the pool cue removed. As it is removed, the patient begins to bleed copious amounts of arterial blood from the site. The surgeons apply direct pressure to control the bleed and order an immediate arteriogram. The arteriogram shows active extravasation from the left superior gluteal artery. Interventional radiologists access the left internal iliac to place a titanium coil in the left superior gluteal artery. The coil occludes the vessel and bleeding is stopped. The rest of the surgery is uneventful and the patient returns home several days later.
Questions to consider:
- What is embolization?
In some cases, it is easiest to stop a hemorrhage by occluding the vessel. This process, called embolization, involves using radiographic imagery to place coils or beads in the affected vessel. Collateral vessels will provide circulation downstream of the occluded vessel. While this case illustrates this interesting treatment technique, it also allows us to look closely at the pelvic vasculature. The superior gluteal artery, when damaged, is difficult to access and difficult to control. Its path through the greater sciatic foramen leaves it especially vulnerable to injury in pelvic fractures (from motor vehicle accidents, falls, etc.) Damage can result in tremendous hemorrhage and death.
- In what way could this patient be considered "lucky"?This patient was lucky in that the impaled end of the pool cue provided partial occlusion of the vessel. Even so, the CT images show that his blood loss was substantial. The hematoma was large enough to displace organs as far away as his kidney. Large amounts of blood can hemorrhage into the abdominal and pelvic cavities without being externally detectable - no visible signs of bruising or distention were noted.
A twenty-six year old male presents to the E.R. after a motorcycle vs. car accident. The patient is awake and alert, and reports pain in his abdomen and pelvis. On physical examination you note that his vital signs are: heart rate 120, blood pressure 120/60, respiratory rate 30. Examination also reveals abrasions on his abdominal wall surface and no signs or presence of blood on his external urethral meatus. Palpation reveals generalized tenderness over the entire abdominal region. In addition, the patient shows particular discomfort when you attempt to assess the stability of his pelvis by placing your hands over his pubic symphysis and laterally applying pressure over the iliac blades. He does not have full hip extension and rotation when you assess his mobility while laying on the exam table. Rectal exam is negative for gross blood, and the patient has a normally placed prostate.
You then order x-rays of the pelvis in 3 planes (AP, lateral, and oblique views) to determine if the patient has a fractured pelvis and a flat plate of the abdomen to determine if the patient has free air in his abdomen. A diagnostic supraumbilical peritoneal lavage turns out negative. You suspect internal bleeding due to the abdominal pain, so you order an angiogram to locate the source. You diagnose a pelvic fracture, complicated by internal bleeding.
The patient is taken to angiography where a laceration of the internal pudendal artery is found, and a selective embolization is performed. External fixation of the pelvis is performed after the bleeding has been stabilized. Urology has been consulted to ascertain if there was any urethral injury.
Questions to consider:
- What are the diagnostic features of a fractured pelvis ?
Demonstrated instability of the pelvic ring can occur via a fracture of the two innominate bones which join the sacrum to form the pelvis. Stability of the pelvic ring is based in large part by ligamentous attachments: anteriorly, the pubic portions are joined by the pubic symphysis and posteriorly they are attached to the sacrum by strong posterior and anterior sacroiliac ligament. These ligamentous attachments themselves can be displaced.
X-rays of the pelvic region with a suspected pelvic fracture would include a view of the pelvic inlet arranged to view cephalad to caudad for a view of the anterior to posterior view (and includes pubic symphysis and sacroiliac joint dislocations). Pelvic outlet views are also performed obliquely in caudal to cephalic direction and obtain views of any vertical instabilities or sacral body fractures. In addition, standard AP and lateral views allow visualization of the innominate bones.
- What vessels branch off the internal iliac artery?The common iliac artery bifurcates into an external and internal iliac artery. The internal iliac artery is known as the "pelvic artery" and provides the blood supply to most of the pelvic structures. The branching pattern of the internal iliac artery is highly variable, but the most common pattern is for the artery to split into anterior and posterior divisions.
Posterior division, in order:
- umbilical artery which provides superior vesical artery branches
- obturator artery
- uterine artery (female)
- vaginal artery (female)
- inferior vesical artery (male, with prostatic branches)
- middle rectal artery which anastomoses with superior and inferior rectal arteries
- internal pudendal
- inferior gluteal
- What procedure would the urologist use to determine if the patient had urethral injury?
A diagnostic technique would be a retrograde urethral cystoscopy using contrast to ascertain if there is a tear in the membranous or spongy regions of the urethra.
Woodburne & Burkel, p. 523-64
Robbins Pathology, p.815-7
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