A. General features
1. Location. The prostate gland lies between the base of the urinary bladder and the urogenital diaphragm. The anterior surface is related to the retropubic space; the posterior surface is related to the seminal vesicles and rectum. The prostate gland is palpated easily during a digital rectal examination.
2. Structure. The prostate gland has five lobes: right and left lateral, right and left posterior, and middle. The prostate gland is a collection of tubulo-alveolar glands and is divided into three zones: peripheral, central, and transitional (periurethral). The lumen of the glands normally contain deposits called corpora amylacea.
3. Prostatic fluid contains citric acid, acid phosphatase, prostaglandins, fibrinogen, and prostate-specific antigen (PSA), which is a serine protease that liquefies semen after ejaculation. Serum levels of acid phosphatase and PSA are used as diagnostic tools to detect prostatic carcinoma.
4. The arterial supply is from the internal iliac artery via the inferior vesical artery.
5. Venous drainage follows two pathways. One pathway is: prostatic venous plexus ->• internal iliac veins inferior vena cava (IVC). This pathway may explain how prostatic cancer metastasizes to the heart and lungs. Venous drainage also proceeds as: prostatic venous plexus > vertebral venous plexus cranial dural sinuses. This pathway may explain how prostatic cancer metastasizes to the vertebral column and brain.
1. Benign prostatic hypertrophy (BPH) is characterized by hypertrophy of the transitional (periurethral) zone, which usually involves the lateral and middle lobes. BPH compresses the prostatic urethra and obstructs urine flow. BPH may be caused by increased sensitivity of the prostate to dihydrotestosterone (DHT). BPH is not premalignant.
a. Clinical signs include: increased frequency of urination, nocturia, difficulty starting and stopping urination, and a sense of incomplete emptying of the bladder.
b. Treatment may include: surgery, 5a-reductase inhibitors (e.g., finasteride (Proscar) 1 to block the conversion of testosterone to dihydrotestosterone, or a-adrenergic antagonists (e.g., terazosin, prazosin, doxazosin) to inhibit prostate gland secretion.
2. Prostatic carcinoma (PC) most commonly is found in the peripheral zone, which usually involves the posterior lobes. The posterior lobes can be palpated on digital rectal examination.
a. Clinical signs. Because PC begins in the peripheral zone, it is in an advanced stage by the time urethral blockage, usually discovered when the patient complains of difficulty in urination, occurs. Prostatic intraepithelial neoplasia often is associated with PC. Serum PSA levels are diagnostic. Metastasis to bone (e.g., lumbar vertebrae, pelvis) is common.
b. Treatment may include: surgery or radiation; leuprolide (Lupron), which is a gonadotropin releasing hormone (GnRH) agonist that inhibits the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) when administered in a continuous fashion, thereby inhibiting secretion of testosterone; and cyproterone (Androcur) or flutamide (Eulexin), which are androgen receptor antagonists.
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