External genitalia in the male

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Contents

Introduction

The external genitalia of the male consist of the penis and the scrotum and its contents. These parts are involved in the processes of urination, intercourse and reproduction.

Penis

The penis protrudes from the anterior aspect of the male pelvis. It has two functions, that of facilitation of urination, and the process of erection and ejaculation.

Anatomy

The penis is made up of three cylinder-like arrangements of erectile tissue, the two corpora cavernosa and the corpus spongiosum. The penile urethra travels invested in the corpus spongiosum, which also constitutes the glans penis. The corpora are filled with sinusoidal tissue which becomes engorged with blood during erection. The distal end of the penis is occupied by the glans penis, which is a continuation of the corpus spongiosum which lies between and beneath the two corpora cavernosa. The penis is invested with penile skin which is continued from the skin of the anterior abdominal wall, and is doubled back on itself at its distal end over the glans, forming the foreskin.

The penis is richly supplied by arteries which are all branches of the internal pudendal artery. The penis is drained through a complex of veins, both superficial and deep, which drain to the periprostatic plexus.

The lymph drainage of the skin of the penis, the corporal tissue and glans penis is to the superficial and deep inguinal nodes.

The penis is richly supplied by the dorsal nerves, which follow the course of the dorsal arteries, and are especially prevalent in the glans. The cavernous nerves ramify in the erectile tissue, providing sympathetic and parasympathetic supply to the erectile tissue.

Penile lesions

Phimosis

The presence of a tight foreskin which cannot be retracted behind the glans is known as phimosis. This can lead to the overgrowth of smegma bacillus under the foreskin due to inability to cleanse the area. Alternatively the glans and foreskin may undergo scarring and fibrosis secondary to balanitis xerotica obliterans, giving rise to phimosis. This situation can be resolved by circumcision.

Paraphimosis

If the retracted foreskin becomes stuck behind the coronal sulcus and cannot be replaced over the glans, this gives rise to the painful condition of paraphimosis, with swelling of the glans distal to the constricting band of tissue, which may result in necrosis of the glans unless the condition is relieved. Treatment is by compression and manual reduction; if this is unsuccessful, urgent surgery in the form of a dorsal slit to release the constricting band is performed, with later circumcision.

Priapism

Prolonged persistence of erection is known as priapism and nowadays is often related to the injection of medications for the treatment of erectile dysfunction. Other causes include trauma, which leads to high-flow priapism, often through the formation of an arteriovenous fistula, or recreational drug use, leading to the more dangerous low-flow priapism, where the penis is engorged with deoxygenated blood, which can lead to penile necrosis and tissue loss. Treatment is by drainage of the blood from the penis, which if unsuccessful, necessitates the formation of a shunt between corporal and cavernosal tissue or directly from the cavernosal tissue to a large vein, such as the transposed saphenous vein.

Peyronie's disease

Abnormal curvature to the penis is often the result of the formation of a plaque of fibrotic tissue in the tunica albugina causing limited expansion and thus curvature in the opposite direction during erection. This may follow trauma but if the process is stable and interfering with intercourse, surgical correction can be undertaken.

Penile cancer

Penile cancer is an uncommon disease that usually occurs in the older patient and is almost exclusively found in the uncircumcised male. Risk factors include smoking and exposure to the human papilloma virus. It is usually a squamous cell carcinoma and can present in the form of carcinoma in situ. Treatment is penectomy, either total or partial, if a sufficient disease-free margin can be attained. If a total penectomy is undertaken, the urethra is rerouted through the perineum as a perineal urethrostomy to allow for voiding. Typically, the inguinal lymph nodes on one or both sides are found to be clinically enlarged. This is often secondary to superinfection of the cancer, so 6 weeks of treatment with antibiotics is often used before reassessing these clinically. If still enlarged, the patient may require staged lymphadenectomy with possible subsequent radiotherapy.

Scrotum and testes

Anatomy

The scrotum is the bag-like structure which hangs below the penis and contains the male reproductive units, the testes and other associated structures. The scrotum is divided into two spaces by a fibro-muscular septum in the form of the median raphe. The normal adult testes are ovoid in shape, 2–3 cm in transverse and antero-posterior diameter and 3–5 cm in length. They are approximately 30 mL in volume.

The scrotum is covered by hair-bearing skin, thrown up into multiple rugae. Under the skin lies the dartos muscle layer. The testes descend from an intraabdominal position and takes coverings from the layers that it passes through as it transverses the abdominal wall via the inguinal canal. Thus the external oblique muscle continues as the external spermatic fascia, and the internal oblique muscle continues as the cremasteric muscle. The internal spermatic fascia is a continuation of the tranversalis fascia and the tunica vaginalis is a continuation of the peritoneal layer. These layers constitute the spermatic cord, which also contains the vas deferens, testicular artery and vein and lymphatics. The testes themselves are surrounded by the tunica vaginalis, which has two layers — a visceral and a parietal layer. This is a potential space that can normally contain 2–3 mL of fluid. Deep to the tunica vaginalis lies the extremely tough tunica albugina, the dense fibrous capsule of the testes. The seminiferous tubules leading from the lobules of the testes coalesce and enter into the rete testis, which passes into the epididymis. This communicates with the vas deferens, travelling upwards via the spermatic cord.

The blood supply of the scrotum is derived from the external pudendal arteries anteriorly and the perineal arteries posteriorly. These vessels do not cross the median raphe, allowing for a relatively bloodless incision. The testis draws its own blood supply with it from the abdomen, and thus the testicular artery which travels in the spermatic cord originates from the aorta. Further arterial supply to the testis and vas deferens comes from the artery to the vas, and a large area of anastamosis occurs at the epididymis with the cremasteric, vasal and testicular arterial branches, allowing for a rich blood supply to the testis.

Venous drainage of the scrotum is via the external pudendal veins at the front and the posterior scrotal branches of the perineal vessels at the back. The testis is drained by many veins forming the pampiniform plexus. These may anastomose extensively with the cremasteric, vasal and external pudenal veins, and are usually in two to three branches in the inguinal canal. The testicular veins drain into the inferior vena cava on the left and the renal vein on the right.

The delineation of scrotal lymph drainage from that of the testes is of vital importance in the surgical treatment of testis cancer. The skin of the scrotum is drained by the superficial inguinal lymph nodes of the ipsilateral side. The testis drains via the spermatic cord to the para-aortic nodes on the same side. This implies that scrotal integrity should not be breached when performing an orchidectomy for testis cancer, as this will ensure that two areas of lymphatic drainage are now involved (see below).

The scrotal skin is innervated by the genital branch of the genitofemoral nerve, with a further input from the perineal branch of the posterior femoral cutaneous nerve. The testes are supplied by nerves from the renal and aortic plexuses, as well as by contributions from the pelvic plexuses accompanying the vas deferens.

Testicular torsion

Torsion involves rotation of the testis and usually occurs in teenage (postpuberty) or early adult life. The condition is due to high reflection of the tunica vaginalis, incomplete fixation or an excessively long mesorchium. The patient presents with sudden onset of pain and swelling, commonly after exertion or intercourse; epigastric pain may be present. The testis is extremely tender and often elevated due to cremasteric spasm but the spermatic cord is not tender. The differential diagnosis is acute epididymitis (see below). Doppler ultrasonography usually shows ischaemia of the testis, although false negative results also occur. The treatment is early surgical exploration since ischaemic necrosis of the testis will result if the torsion is not released as a matter of urgency. Following release of the torsion, the testis is fixed to the scrotum to avoid recurrence.

Scrotal masses

Hydrocoele

Primary hydrocoele represents a collection of fluid within the tunic vaginalis which obscures palpation of the underlying testis and is readily transilluminable. It is treated initially by aspiration; if recurrent, subtotal excision of the parietal tunica is performed.

Secondary hydrocoele is usually a response to underlying pathology in the testis or epididymis, so that treatment is directed to the underlying pathology.

Spermatoceles/Epididymal cysts

These fluid collections occur in relation to the head of the epididymis. They are of no importance unless they become large and uncomfortable, when they can be excised surgically.

Varicocoele

This presents as a dilatation of the pampiniform plexus, visible and palpable only in the erect position. It usually occurs only on the left side and is believed to be due to a deficiency in the valves in the left spermatic vein, which drain directly into the left renal vein.

No specific treatment is required, although when varicocoele is found during the investigation of infertility, it is common to suggest correction by high ligation of the spermatic vein. Sudden onset of varicocoele on the left side may suggest occlusion of the left renal vein due to renal tumour, and the rare right-sided varicocoele suggests situs inversus or, more rarely, vena caval occlusion.

Epididymitis

Clinical presentation

Acute epididymitis is a disease of young men, resulting from unprotected intercourse, commonly due to Chlamydia organisms, or of elderly men with bacterial urinary tract infection, when the organism is commonly Escherichia coli.

The presenting symptom is scrotal pain, usually gradual in onset (as distinguished from the sudden onset in testicular torsion). On examination, there is marked swelling and tenderness of the posterior part of the scrotal contents and the spermatic cord, and commonly a small secondary hydrocoele. There is usually a moderate pyrexia and accompanying leucocytosis.

Investigations

Urine culture is required, although it is common for there to be no positive findings in the young. Doppler ultrasound shows a high blood flow in contrast to the ischaemia of torsion.

Treatment

Bedrest, scrotal support, analgesia and antibiotics are required. If there is no positive urine culture, young men are treated with tetracycline and the elderly with trimethoprim. In the elderly, follow-up should include determination of the source of infection, usually stasis due to prostatic enlargement.

Testicular cancer

Testicular cancer is uncommon, but is the most common solid organ cancer of young males. It most commonly occurs between the ages of 20 and 35 years and usually presents with a painless testicular mass, which must be differentiated from an extra-testicular mass. Up to 50% of patients may present with metastatic disease.

Aetiology

The tumour is markedly more common in those with a history of undescended testes, especially if the testis is ectopic, i.e. found lying outside the normal path of testicular descent from the abdomen. In approximately 5%, a second tumour develops in the contralateral testis.

Pathology

Testicular cancer is most commonly (95%) originates from the germ cell, that is, it arises in the reproductive cells, although Leydig cell tumours and other tumours such as lymphomas can occur. The cancer types are broken down into two types, those which are seminomas and those which are not. These are known as non-seminomatous germ cell tumours (NSGCTs). These are a mixed group of tumours which may have a single cell type or be mixed in composition and are much more aggressive than pure seminomas. They consist of embryonal cancers, choriocarcinoma, teratomas, yolk sac tumours and mixed tumours. NSGCTs may express characteristics of trophoblastic or synctiotrophoblastic cells, and thus can produce proteins related to these, which can be used in diagnosis and monitoring of treatment outcome. The relevant proteins are alphafetoprotein (AFP), beta human chorionic gonadotropin (βHCG) and lactate dehydrogenase (LDH). Eighty to 90% of patients with NSCGTs will have a rise in one or both of AFP or βHCG, whilst a rise in βHCG will be seen in less than 10% of patients with seminoma, and rise in AFP is almost never seen. This rise may be due to an undetected element of NSGCT in the tumour or production by synctiotrophoblasts. LDH reflects bulk of tumour and is very useful in follow-up of metastatic disease.

Clinical presentation

The first sign is a lump in the scrotum noticed while bathing or by a sexual partner. Pain is an unusual feature but one not to be ignored.

Examination demonstrates a hard, heavy testis or a localised nodule, and there may be a secondary hydrocoele.

Investigations

Serum samples are taken for αFP, βHCG and LDH. Staging (see ) involves computed tomography (CT) scanning of the abdomen and chest initially.

Treatment

Treatment is initially by inguinal (not scrotal) orchidectomy, so as not to violate the scrotal lymphatic drainage area, and classically the vasculature is occluded prior to tumour manipulation to avoid potential seeding of metastatic disease. Seminomas confined to the testis are treated with low-dose radiotherapy to the abdominal nodes. NSGCTs confined to the testis with low or negative marker levels and favourable histology may be followed intensively with regular tumour markers, chest X-rays and CT scans. Alternatively, they may be offered a primary retroperitoneal lymph node dissection (RPLND). Patients with retroperitoneal nodal disease and/or more distant metastatic disease will be given platinum-based chemotherapy, and RPLND will be offered to those patients with residual masses postchemotherapy. Follow-up requires regular review of the tumour markers and CT scan as indicated.

Outcome

Testicular cancer represents one of the best examples of the immune benefits of multi-modality treatment of cancer, with a cure rate of less than 50% prior to 1970 rising to 95% at the present time.
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