THE TESTICLES
The male gonads are known as the testicles, or testes (singular: testis). They are equivalent to the female ovaries and are responsible for producing sperm and the male sex hormone, testosterone.
The testes are formed within the abdomen early during the development of the male foetus. In response to hormonal triggers, they gradually descend through the abdomen until they reach the pelvis. They then enter a passageway on either side that passes over the pelvic bone the inguinal canal and drop down into the scrotal sac. At birth, the testes can usually be felt within the scrotum.
Each mature testis is an oval organ around 44.25 cm (1.51.6 in) long and 22.8 cm (.751 in) in diameter. They are divided into 200400 compartments, each of which contains several highly convoluted seminiferous tubules. These are the 'sperm factories', where millions of sperm are made. The spaces between these seminiferous tubules are filled with nests of cells the interstitial cells of Leydig which are where the male sex hormone, testosterone, is made.
Each testis is protected by a tough fibrous capsule, the tunica albuginea, and is suspended in the scrotum at the end of the spermatic cord.
The Epididymis
Both ends of the seminiferous tubules within each testis open into a network of vessels that drain into the epididymis. This is a tightly coiled collecting tube attached to the top of the testis, at the back. If unravelled, an epididymis would measure around 6 m (18 ft) long. The coils of the epididymis are wrapped together to form a head (attached to the testis), a body, and a so-called 'tail'. Sperm that pass through the epididymis are still maturing, and most gain motility while passing through. The epididymis on each side leads into a vas deferens.
The Vas Deferens
Each vas deferens is a narrow, muscular tube that acts as a storage unit for mature sperm. During orgasm, it pumps sperm up from the epididymis and out into the penis. The two vas deferens, one on each side, are the tubes that are cut during a vasectomy (see vasectomy).
Each vas deferens takes a complicated route up through the scrotum, through the inguinal canal and pelvis and passes over a ureter (tube running from each kidney to the bladder) to drop down just behind the bladder. Here, each vas deferens joins with the outflow from a seminal vesicle to form an ejaculatory duct.
Seminal Vesicles
Each of the two seminal vesicles is a coiled, blind sac about 5 cm (2 in) long. They stretch upwards from the prostate gland to lie between the bladder and the rectum.
The seminal vesicles secrete a thick, gelatinous, protein-rich fluid which gives semen its initial clotted characteristic. These secretions are rich in fructose, a sugar which supplies the sperm with most of their energy. Yellow pigments are often present and may be seen in semen as yellow flecks. The seminal vesicles also secrete hormone-like substances (prostaglandins), which have an effect on the female tract. They help the cervix (neck of the womb) to 'pout' slightly so sperm can swim through more easily, and may also trigger wave-like contractions which induce eddy currents and help propel the sperm along.
The Ejaculatory Ducts
There are two ejaculatory ducts, one on each side, behind the neck of the bladder. These form where the vas deferens and seminal vesicle meet on each side. The ejaculatory ducts pass through the single, midline prostate gland to direct semen into the penis, within the prostate gland itself.
Cowper's Glands
Cowper's (bulbourethral) glands lie underneath the prostate gland on either side. They secrete a lubricating fluid into the urethra early on during sexual activity. This may appear at the end of the penis as a glistening drop of slippery mucus. These glands can become inflamed, for example because of sexually transmissible diseases such as Chlamydia and gonorrhoea.
The Spermatic Cord
Each testicle is suspended within the scrotum by a spermatic cord. This structure contains the vas deferens plus several arteries, veins and nerves. It is covered with three layers of tissue (picked up during the descent of the testicle through the abdomen during foetal development) and is sheathed in the cremaster muscle.
Cremasteric Reflex
The cremaster (literally, suspender) muscle is responsible for the cremasteric reflex the involuntary drawing up of the testicles towards the inguinal canal, for example when it is cold, during the fight-or-flight response to shock (see stress), or when touched.
Highly retractile testicles are normal in young children, but usually disappear by puberty. It is important that a retracted testicle (normal) is not confused with an undescended testicle (abnormal). These are easily told apart by a surgeon who, having identified the tiny testis at the bottom of the inguinal canal, can gently coax it down into the scrotum with a downward stroking action. Retractile testes are normal and require no treatment.
Sumo wrestlers can train themselves to withdraw their testicles high up towards the abdomen for protection during competition.
Testicular Descent and Undescended Testes
The testicles originally develop within the abdominal cavity of the male embryo, near the kidneys. They become attached to a structure known as the gubernaculum, which enlarges to anchor the testes near the groin. As the embryo develops, the testes appear to move downwards through the abdomen but in fact they stay anchored in the same place. The gubernaculum remains the same size, while the developing embryo and enlarging abdominal cavity differentially grow upwards around it.
Between the 28th and 35th week of pregnancy, the gubernaculum elongates through a passageway at the base of the abdominal cavity (inguinal canal), over the pelvic bone and into the scrotum. The gubernaculum becomes shorter and thicker and acts as a guide, keeping the inguinal passage open as the testis descends. Once the testis is in position in the scrotum, the gubernaculum withers away.
It was originally thought that the male hormone, testosterone, was directly responsible for the shortening and migration of the gubernaculum. Now it is known that testosterone masculinizes the genitofemoral nerve, which supplies the groin and scrotum. This triggers the nerve to secrete a protein (calcitonin gene-related peptide) which activates the gubernaculum causing it to contract in rhythmic waves. As a result, each gubernaculum shortens and pulls its attached testicle down.
If the genitofemoral nerve is cut, damaged, or fails to secrete enough of the peptide, the testes fail to descend. In 1 per cent of full-term baby boys, and 10 per cent of premature males, one testis is still within the abdomen or inguinal canal at birth. For babies born under 2 kg (4.4 lb) in weight, the incidence of undescended testicles is 45 per cent.
In a quarter of cases of maldescent, both testes are involved. This is known as cryptorchidism (hidden gonads) and is thought to be caused by insufficient testosterone production during foetal life. This in turn fails to stimulate secretion of enough calcitonin gene-related peptide needed to trigger testicular descent. For some reason, the incidence of cryptorchidism has increased by 60 per cent over the last 30 years. This may be related to foetal exposure to weak environmental oestrogens.
In many cases, an undescended testicle descends on its own within a few months of birth, so that by the age of 1 year, only 2 per cent of baby boys are affected. After this time, an undescended testis is unlikely to correct itself spontaneously and surgical intervention is needed.
An undescended testis which is left in the abdomen does not develop normally. It will fail to produce sperm, since this requires a temperature at least 4°C lower than core body temperature. A testis retained in the abdomen is also at increased risk of becoming cancerous (see below).
The operation to correct an undescended testis is called orchidopexy. This must be carried out in the first few years of life to give the testis the best chance of developing normally. The testis is freed from its position within the inguinal canal (occasionally, it needs to be found within the abdomen) and is brought down into the scrotum. The undescended testis is usually surrounded by a loose sleeve of tissue which pouches down from the membrane lining the abdominal cavity (peritoneum). This pouch is known as a hernial sac and needs to be tied off and cut away to prevent a future hernia (see hernias). The descended testis is then tethered loosely into the scrotal sac with a stitch, so it doesn't shoot back up to its original position.
In most cases, an undescended testicle is slightly smaller than normal. If it is abnormally small and poorly developed, it may have to be removed. This has little effect on future fertility as long as the other testis is normal. An artificial, egg-shaped prosthesis can be inserted into the scrotum to produce a good cosmetic result.
Rarely, undescended testicles are thought to be caused by a hormonal deficiency. Injections of human chorionic gona- dotrophin (hCG), a pregnancy hormone secreted by the placenta, sometimes helps to trigger testicular descent and may solve the problem without recourse to operation. This is only done in the rare cases when hormonal deficiency is demonstrated.
Researchers in Australia have patented a treatment that uses calcitonin gene-related peptide to trigger descent of retained testes. The peptide can be injected into the scrotum, implanted under the skin, or absorbed via a skin patch.
Ectopic Testis
An ectopic testis is one that has descended into an abnormal position. Rather than passing through the inguinal canal, it ends up:
• at the base of the penis
• in the abdominal wall
• behind the scrotum
• at the top of the leg.
As a maldescended testis is outside the abdominal cavity and therefore at a lower temperature, it usually develops normally but is vulnerable to injury. An exploratory operation is needed to find the testis, bring it down and tether it into the correct position (orchidopexy).
Testicular Pain
Testicular pain is called orchialgia. The testicles are sensitive structures and even mild injury causes pain. If a direct blow (e.g. kick) is hard, the wall of the testis may tear and vomiting, severe pain and even fainting can occur. An operation may be needed to evacuate blood clots and repair the damage.
Pain and tenderness are often noticed in the testis without a history of trauma and require urgent medical assessment. Torsion of the testis, bacterial infection and testicular cancer (see below) must be ruled out as these need immediate treatment. Another possibility is mumps orchitis (see below).
Pain may also be felt in the testes from problems elsewhere in the area, such as inflammation of the prostate gland, anal spasm, cystitis, or kidney stones.
Often, no cause will be found for testicular pain and the problem may be due to engorgement with semen or the opposite too many ejaculations.
Recent studies show that cutting the nerves to the testicles may relieve intractable testicular pain where no cause has been found. On the cases performed so far, all have remained pain free for at least three years.
Testicular Swelling
A swollen testicle should be medically examined as soon as possible. Painless swelling may be due to a hydrocoele, epididymal cyst, spermatocoele, or varicocoele. These are all explained below. A testicular tumour must also be ruled out.
Painful swelling of the scrotum may be caused by testicular torsion, injury and bleeding. When accompanied by a fever, swelling is usually due to infection of the testis (orchitis) or of the testis and epididymis (epididymo-orchitis). Only rarely is a painful swelling due to a tumour, but this important diagnosis must not be missed (see below).
Mumps Orchitis
Inflammation of a testicle is called orchitis. This is most commonly due to the mumps virus. This occurs in 2535 per cent of males who contract mumps after puberty. It is sometimes seen without enlargement of the salivary glands in the cheek, but there is usually a history of contact with mumps. Symptoms include swelling and severe pain in the affected testis along with a high temperature. Usually, only one testicle is affected.
If mumps orchitis occurs before puberty, complete recovery follows. If it occurs after puberty, the affected testicle usually shrinks and sperm production tails off. This is due to degenerative changes occurring in the seminiferous tubules.
As mumps orchitis tends to affect only one testicle, there is usually no future problem with fertility. Sperm counts may be lower than normal and the time taken for an affected man's partner to conceive may be slightly longer than normal, but there is usually no cause for concern. Encouraging results were found in a study of 72 young Israeli soldiers who suffered mumps. Of these, 19 had suffered mumps orchitis. Following recovery, some men had more abnormal sperm than expected and their sperm tended to be less active. All sperm samples were considered within the fertile range, however. Interestingly, men who smoke cigarettes and catch mumps are statistically more likely to develop mumps orchitis than are non-smokers.
Treatment of mumps orchitis is with painkillers plus ice-packs to reduce swelling and pain. Symptoms usually subside after four to seven days.
Acute inflammation of a testis and its attached epididymis is called epididymo-orchitis. Symptoms vary from mild swelling and tenderness to a high fever, severe pain, gross swelling and redness of the scrotum with incapacitation. Pain and swelling usually seem worse at the back of the testis. If infection and torsion of the testis cannot be differentiated, an exploratory operation is essential to clinch the diagnosis.
Epididymo-orchitis is caused by bacterial or viral infection spreading from the urinary tract or bowel, or via the bloodstream or vas deferens. The commonest causative organisms in men under the age of 40 are Chlamydia and gonorrhoea (see Chlamydia and gonorrhoea). In older patients it is often due to the bowel bacterium Escherischia coli. In rare cases, epididymo-orchitis is due to infection with tuberculosis (TB).
Treatment is with antibiotics (oral or intravenous, depending on severity), scrotal elevation and rest. Ice-packs may help to reduce swelling. Before the advent of powerful antibiotics, surgical drainage of the area was performed, but this is rarely needed nowadays.
If infection has spread from the urinary tract, tests are performed to see if there are any underlying anatomical abnormalities (e.g. kidney scarring, stones, etc.) that might have triggered the problem.
After an attack of epididymo-orchitis, it may take several months for the swollen testis to return to its normal size. In some cases, the organ will remain abnormally enlarged for life.
Hydrocoele
During development, the membrane lining the abdominal cavity (peritoneum) pouches down into the scrotum as the testicle descends. This closes off to leave an empty remnant in the scrotum (tunica vaginalis). In middle age, this remnant often fills with fluid to form a soft, painless swelling in the scrotum. This can grow quite large, to the size of a grapefruit or even a football. In most cases there is no underlying cause, but occasionally a hydrocoele forms as a result of inflammation, infection, injury, or rarely an underlying tumour of the testicle on that side.
A doctor tests for a hydrocoele by holding a pen torch next to the scrotal skin. The swelling will light up (trans-illuminate) if it is due to a fluid-filled hydrocoele.
Small hydrocoeles are often left alone. Larger ones may be drained off under local anaesthetic using a needle and syringe. The fluid is usually pale, clear and straw-coloured. Unfor-tunately, most hydrocoeles tend to reform. To help prevent this, an irritating substance (sclerosant) can be injected into the empty sac after drainage to set up a mild inflammation. This allows the walls of the empty sac to mat together.
Recurrent, large hydrocoeles are treated by surgical excision of the hydrocoele sac. Remnants are then turned inside out, so fluid secreted by the sac walls is absorbed by the scrotum and does not recollect.
In infants, a hydrocoele is usually left until the age of 1 as most seem to disappear spontaneously. After the first year, the hydrocoele is repaired to prevent a future hernia developing (see hernias).
Varicocoele
A varicocoele is literally a collection of varicose veins surrounding a testicle. This is a common condition affecting up to 15 per cent of males, almost exclusively on the left-hand side. This is because the left testicular vein empties vertically into the renal vein a long way up. The varicosities form when the valve system between these two veins fails, so that blood falls backwards under the pull of gravity. The right testicular vein enters directly into the major trunk vein (inferior vena cava) at an oblique angle, further down. Its valves do not have to support the same weight of blood as those in the left testicular vein and are therefore much less likely to fail.
A varicocoele feels like a warm tangle of worms in the scrotum. It can cause an aching discomfort which is relieved by wearing an athletic support, but is often symptomless.
It is traditionally believed that a varicocoele can trigger a fall in sperm count through keeping hot blood pooled within the scrotum rather than draining it away. Any increase in scrotal temperature damps down sperm formation, which ideally needs a temperature of 47°C less than core body temperature. Varicocoeles are therefore said to be linked with 3040 per cent of cases of male infertility. This belief is now controversial, with many reproductive physiologists claiming that varicocoeles have little effect on male fertility. A varicocoele will usually be surgically excised, however, if the sperm count is compromised in a man wishing to have more children. A trial that followed men up for longer than usual has at last shown a significant long-term outcome. Cumulative pregnancy rates were 30 per cent over a 31-month period for men who had surgical correction of their varicocoele, compared with 18 per cent over a 29-month period for men who kept their varicocoele intact. Varicocoeles are also removed if they ache, but are otherwise left in place.
A new device called a Varicoscreen has been developed to (as the name suggests) screen for varicocoeles. This is a heat-sensitive, spectacle-shaped plastic device that is wrapped around the scrotum. As a varicocoele increases the temperature of a testicle, it will turn one side of the Varicoscreen green, violet or blue. A red or brown result on both sides means no varicocoele is present. The test can pick up varicocoeles before they become clinically obvious; doctors in Holland are already using it to screen boys aged 1315. Around 1 in 50 are found to be affected.
Belgian surgeons have developed a technique that injects a substance similar to super-glue into a varicocoele via a tiny catheter. The glue hardens on contact with blood to seal off the affected vein and causes it to shrink.
Epididymal Cyst
An epididymal cyst is a harmless swelling arising from the epididymis, the coiled collecting tube attached to the back of each testis. Small, pea-sized epididymal cysts are common in men over the age of 40 and do not need treatment. Rarely, they enlarge to the size of a golf ball and beyond, to become uncomfortable or tender. Epididymal cysts are often multiple and may affect both sides. They are filled with a clear, colourless fluid and are usually left in place. If they become troublesome, epididymal cysts are easily removed surgically, usually as a day case procedure. Although epididymal cysts are harmless, any lump arising from the scrotum should be examined by a doctor to make sure it is not a testicular tumour.
Spermatocoele
A spermatocoele is similar to an epididymal cyst, but instead of containing clear fluid it is filled with milky semen and sperm. The two swellings can only be told apart if fluid is drained for examination. Spermatocoeles are harmless and are usually left in place. If they become troublesome, they can be surgically excised.
Torsion of the Testis
As each testis is suspended in the scrotum from the spermatic cord, it is possible for it to twist round on itself. The blood supply to each testis comes from three arteries within this spermatic cord, and by twisting, the blood supply is instantly cut off.
Symptoms include severe scrotal pain (due to lack of oxygen to the testicular tissues), sometimes felt more in the abdomen than in the scrotum. The twisted testis becomes swollen and tender and the scrotum discoloured. Nausea is often present.
Torsion of the testis is most common in adolescent boys around the age of puberty, but can occur at any age. It is more common if a slight anatomical abnormality is present, such as the testis lying upside down in the scrotum (uncommon), or if it lies back to front (common). These make the testis more mobile.
Testicular torsion is a surgical emergency. If the blood supply is not restarted within four hours, the testis will become irreparably damaged and die. If the condition is suspected, an exploratory operation is performed. The scrotum is opened and, if the diagnosis is correct, the testis can easily be un-twisted. If normal blood supply resumes, both testes are anchored into place with small stitches to stop the twisting from occurring again, and the scrotum closed.
If blood flow does not resume, this means the blood supply has clotted off and the testicle is irreparably damaged. It therefore has to be removed (orchidectomy). The remaining testicle is then stitched into place to prevent a future torsion on the other side too. There should be no problem with future fer- tility as the remaining testicle usually continues making sufficient sperm.
Cancer of a testicle is the commonest malignancy in young males between the ages of 20 to 40 years. It is the third leading cause of death within this age group. Unfortunately, the number of cases is on the increase, having quadrupled in incidence over the last 50 years. In the UK, over 1,000 new cases occur every year, with around 150 deaths.
The disease may have an hereditary component. Research shows that a man whose brother has testicular cancer is 10 times more likely to develop the disease himself than a man with no affected relatives. However, the risk is still small (1 in 450); having an affected brother only raises the risk to 1 in 50. These are good odds if you consider that a woman's lifetime risk of developing breast cancer is 1 in 11.
A male born with an undescended testicle is 36 times more likely to develop testicular cancer than a male born with both testicles in the scrotum. Overall, 10 per cent of cases occur in men who have had a previous operation to bring a testicle down.
If a tumour does develop in these males, it is four times more likely to develop in the testicle that failed to descend than in the testicle that was present in the scrotum at birth. If the undescended testicle is left inside the abdomen, the risks of a tumour developing are even greater.
Recent research has suggested a link between drinking milk and developing testicular cancer. Questioning of 200 males found that drinking an extra pint of milk per day during adolescence was associated with a 2.5 times increased risk of the disease. No link was found between eating other dairy products, including cheese, which suggests that substances present in milk but not in cheese are involved. The average difference in milk consumption between men with testicular cancer and those without was only a fifth of a pint, so the findings are not conclusive. Environmental oestrogens, including those present in cow's milk, are increasingly implicated in male birth defects, male sterility and cancers of the testes and prostate gland, however.
Examining Your Testes
The only good thing about testicular cancer is that 95 per cent of those affected are readily cured if the cancer is caught early enough. It is therefore essential that all males regularly examine their testicles for abnormal lumps. This is best done in the bath (or shower) when the scrotum is warm and relaxed.
Hold each testicle gently between the thumb and fingertips of both hands. Slowly bring the thumb and fingertips of
one hand together while relaxing the fingertips of the other. Alternate this action several times so the testicle glides smoothly between both sets of fingers. This lets you assess the shape and texture of the testis.
Don't press hard, and be careful not to twist the testicle. Each testicle should feel soft and smooth like a hard-boiled egg without its shell. You should be able to feel the soft epididymis attached at the back. What you are looking for is any lump, swelling, irregularity, abnormal hardness, tenderness, or any change within the body of the testicle itself.
If you notice anything unusual, even if you think it is a hydrocoele or a varicocoele, it is important to have a definitive diagnosis made by your doctor as soon as possible. If you notice blood in your urine or sperm, you should also seek a medical opinion without delay.
Types of Tumour
Ninety-six per cent of all testicular tumours are either seminomas (one in three tumours) or teratomas (two in every three tumours). The other 4 per cent are made up of embryonal cell cancers and choriocarcinoma both of which are rare.
Teratomas tend to affect men aged 20 to 30, with the peak age being 27 years. Seminomas are more common between the ages of 30 and 40, with the peak incidence occurring at age 35.
A seminoma is made up of a single type of cell (spermatocytes, which produce sperm), while a teratoma is made up of several different sorts of cell. It can contain cells similar to those of cartilage, bone, muscle and fat or, occasionally, even teeth or hair.
Eighty per cent of testicular tumours first present as testicular swellings. In 3540 per cent of cases, men also notice acute pain and tenderness of the testis, similar to that of epididymo-orchitis. This can make diagnosis of the condition difficult. Another 40 per cent of males notice a dull aching, dragging sensation in the scrotum, especially if the testis has swollen significantly. Other signs include general feelings of tiredness, loss of appetite and weight loss. Occasionally, there is abdominal pain, usually if lymph nodes (glands) within the abdomen are affected with secondary spread. Involvement of the lymph system can also cause swelling of the legs due to obstruction of fluid drainage.
Many men date the onset of their symptoms to an injury, but this is thought to be a coincidental effect the injury drawing attention to the tumour rather than causing it.
Testicular lumps are investigated by ultrasound, which can usually distinguish a malignant lump from a benign one; sometimes a testicular biopsy is performed. The other testicle also needs full investigation, as in 2 per cent of cases tumours are present in both testes.
Blood tests are also done, as four out of five testicular tumours secrete chemicals (alpha-fetoprotein, beta-HCG) which are easily detectable and help to pinpoint the diagnosis.
Other investigations are performed to look for cancer spread. These include special body scans, a dye test of the lymphatic system (lymphangiogram) and liver and bone scans.
When a testicular cancer is diagnosed, the testicle must be removed as soon as possible through a simple scrotal incision. The tumour is then immediately examined under the microscope to confirm the diagnosis.
Testicular tumours are now considered curable. The cure rate for cases caught early in the disease is 95 per cent and likely to increase with the advent of new drugs and treatments. Tumours caught in later stages have an 8090 per cent cure rate, which is still good.
Unfortunately, occasional tumours prove resistant to drugs. Increased awareness, regular examination of the testicles and early treatment are still a must.
Seminomas are usually curable just by removal of the affected testicle. If there is evidence of spread, chemotherapy (cisplatin, etoposide) is given. Unfortunately, chemotherapy's side-effects include nausea, vomiting and temporary hair loss. New anti-sickness drugs mean that these side-effects are less severe. Seminomas are also very sensitive to X-rays, and radiotherapy to the pelvic lymph nodes is an alternative treatment suitable for some cases after orchidectomy.
If a tumour is diagnosed as a teratoma, chemotherapy is sometimes started right away. If there is no evidence of spread to pelvic lymph nodes, surgery will be the main form of treatment, chemotherapy kept in reserve as another treatment option as necessary.
Providing the other testis is healthy, radiotherapy or chem- otherapy do not generally cause infertility in the remaining testis. The sperm count is lowered for up to two years, but this usually improves. Many men opt to have semen samples frozen before treatment and stored for future use in artificial insemination techniques.
