A 62-year-old man comes to the office due to an elevated prostate-specific antigen level on a screening test. When asked about genitourinary symptoms, the patient says, "It often takes a bit of time before my urine starts flowing," but he has no other problems. Abdominal and external genital examinations are unremarkable. Digital rectal examination reveals hard prostate nodules. A biopsy confirms adenocarcinoma, and the patient undergoes a radical prostatectomy. During the surgery, the nerves within the fascia surrounding the gland are inadvertently injured. Which of the following is the most likely consequence of the nerve injury?

Question

A 62-year-old man comes to the office due to an elevated prostate-specific antigen level on a screening test.  When asked about genitourinary symptoms, the patient says, "It often takes a bit of time before my urine starts flowing," but he has no other problems.  Abdominal and external genital examinations are unremarkable.  Digital rectal examination reveals hard prostate nodules.  A biopsy confirms adenocarcinoma, and the patient undergoes a radical prostatectomy.  During the surgery, the nerves within the fascia surrounding the gland are inadvertently injured.  Which of the following is the most likely consequence of the nerve injury?

Quizplus · Accepted Answer

11ec160b_358f_a376_9249_e98fec6ac4de_MD0001_00 The prostatic plexus lies within the fascia of the prostate and originates from the inferior hypogastric plexus (which itself is a continuation of the hypogastric nerve with additional input from the pelvic and sacral splanchnic nerves). The lesser and greater cavernous nerves arise from the prostatic plexus and pass beneath the pubic arch to innervate the corpora cavernosa of the penis and urethra. The cavernous nerves carry post-ganglionic parasympathetic fibers that facilitate penile erection. Prostatectomy or injury to the prostatic plexus can cause erectile dysfunction; as a result, surgeons attempt to preserve the integrity of the prostatic fascial shell during surgery. (Choice A) Detrusor muscle overactivity leads to urge incontinence, which is more common in women. The detrusor muscle is controlled by parasympathetic fibers from the pelvic splanchnic nerves and inferior hypogastric plexus, which are not usually injured during prostatectomy. (Choices C, D, and F) Branches of the pudendal nerve innervate the external urethral and anal sphincters. They also provide sensory innervation of the external genitalia. Pudendal nerve injury can lead to fecal incontinence, decreased penile sensation, or external urethral sphincter paralysis. Although urethral muscle injury can occur during prostate surgery, injury to the main pudendal nerve is less common with prostatectomy. (Choice E) The cremasteric reflex is elicited by lightly stroking the medial thigh, which causes contraction of the cremaster muscle to pull up the ipsilateral testis. This reflex is mediated by the genitofemoral nerve, which originates from the L1-L2 spinal nerves. Loss of the cremasteric reflex is most commonly seen with testicular torsion or L1-L2 spinal injury. Educational objective: The prostatic plexus (inferior hypogastric nerves plus pelvic and sacral splanchnic nerves) lies within the fascia of the prostate and innervates the corpus cavernosa of the penis, which facilitates penile erection. As a result, prostatectomy or injury to the prostatic plexus can cause erectile dysfunction. __________ References: Optimizing postoperative sexual function after radical prostatectomy. (http://www.ncbi.nlm.nih.gov/pubmed/23205061)

A 62-Year-Old Man Comes to the Office Due to an Elevated