Around 15% of all adult males, up to 35% of men who are evaluated for male infertility, and around 80% of men who are infertile due to some other cause, have varicocele.

A hydrocele testis is not generally thought to affect fertility. However, it may be indicative of other factors that may affect fertility.

A hydrocele testis is an accumulation of clear fluid in the tunica vaginalis, the most internal of membranes containing a testicle. A primary hydrocele causes a painless enlargement in the scrotum on the affected side and is thought to be due to the defective absorption of fluid secreted between the two layers of the tunica vaginalis (investing membrane). A secondary hydrocele is secondary to either inflammation or a neoplasm in the testis.

A hydrocele usually occurs on one side, but can also affect both sides. The accumulation can be a marker of physical trauma, infection, tumor or varicocele surgery, but the cause is generally unknown. Indirect inguinal hernia indicates increased risk of hydrocele.

A hydrocele is normally seen in infant boys, as an enlarged scrotum. In infant girls, it appears as enlarged labia. However, hydroceles are more common in boys than girls.

A hydrocele can be produced in four ways:

- by excessive production of fluid within the sac, e.g. secondary hydrocele

- through defective absorption of fluid

- by interference with lymphatic drainage of scrotal structures as in case of elephantiasis

- by connection with a hernia of the peritoneal cavity in the congenital variety, which presents as hydrocele of the cord

A hydrocele is an accumulation of serous fluid in a body cavity. A hydrocele testis is the accumulation of fluids around a testicle. It is often caused by fluid secreted from a remnant piece of peritoneum wrapped around the testicle, called the tunica vaginalis. Provided there is no hernia present, hydrocoeles below the age of 1 year usually resolve spontaneously. Primary hydrocoeles may develop in adulthood, particularly in the elderly and in hot countries, by slow accumulation of serous fluid, presumably caused by impaired reabsorption, which appears to be the explanation for most primary hydroceles, although the reason remains obscure. A hydrocele can also be the result of a plugged inguinal lymphatic system caused by repeated, chronic infection of "Wuchereria bancrofti" or "Brugia malayi", two mosquito-borne parasites of Africa and Southeast Asia, respectively. As such, the condition would be a part of more diffuse sequelae commonly referred to as elephantiasis, which also affects the lymphatic system in other parts of the body.

Often the greatest concern with respect to varicocele is its effect on male fertility. The relationship between varicocele and infertility is unclear; some men with the condition are fertile, some have sperm that are normal in shape and move normally, but are compromised in function, and some have sperm with abnormal shapes or that do not move well. Theories as to how variocele affects sperm function include damage via excess heat caused by the blood pooling and oxidative stress on sperm (ROS).

Tobacco smoking and mutations in the gene expressing glutathione S-transferase Mu 1 both put men at risk for infertility; these factors may also exacerbate the risk that varicocele will affect fertility.

Fournier's gangrene ( an aggressive and rapidly spreading infection of the perineum ) usually presents with fever and intense pain. It is a rare condition but fatal if not identified and aggressively treated with a combination of surgical debridement and broad spectrum antibiotics.

Chronic scrotal pain (pain for greater than 3 months) may occur due to a number of underlying conditions. It occurs in 15-19% of people post vasectomy, due to infections such as epididymitis, prostatitis, and orchitis, as well as varicocele, hydrocele, spermatocele, polyarteritis nodosa, testicular torsion, previous surgery and trauma. In 25% of cases the cause is never determined. The pain can persist for a long and indefinite period of time following the vasectomy, in which case it is termed post-vasectomy pain syndrome (PVPS).

Most cases of polyorchidism are asymptomatic, and are discovered incidentally, in the course of treating another condition. In the majority of cases, the supernumerary testicle is found in the scrotum.

However, polyorchidism can occur in conjunction with cryptorchidism, where the supernumerary testicle is undescended or found elsewhere in the body. These cases are associated with a significant increase in the incidence of testicular cancer: 0.004% for the general population vs 5.7% for a supernumerary testicle not found in the scrotum.

Polyorchidism can also occur in conjunction with infertility, inguinal hernia, testicular torsion, epididymitis, hydrocele testis and varicocele. However, it is not clear whether polyorchidism causes or aggravates these conditions, or whether the existence of these conditions leads sufferers to seek medical attention and thus become diagnosed with a previously undetected supernumerary testicle.

A direct inguinal hernia is less common (~25–30% of inguinal hernias) and usually occurs in men over 40 years of age.

Men have an 8 times higher incidence of inguinal hernia than women.

Polyorchidism is the incidence of more than two testicles. It is a very rare congenital disorder, with fewer than 201 cases reported in medical literature and 6 cases (two horses, two dogs and two cats) in veterinary literature.

Polyorchidism is generally diagnosed via an ultrasound examination of the testicles. However, the diagnosis of polyorchidism should include histological confirmation. The most common form is triorchidism, or tritestes, where three testicles are present. The condition is usually asymptomatic. A man who has polyorchidism is known as a polyorchid.

Surgical correction of inguinal hernias is called a hernia repair. It is not recommended in minimally symptomatic hernias, for which watchful waiting is advised, due to the risk of post herniorraphy pain syndrome. Surgery is commonly performed as outpatient surgery. There are various surgical strategies which may be considered in the planning of inguinal hernia repair. These include the consideration of mesh use (e.g. synthetic or biologic), open repair, use of laparoscopy, type of anesthesia (general or local), appropriateness of bilateral repair, etc. Laparoscopy is most commonly used for non-emergency cases, however, a minimally invasive open repair may have a lower incidence of post-operative nausea and mesh associated pain. During surgery conducted under local anaesthesia, the patient will be asked to cough and strain during the procedure to help in demonstrating that the repair is without tension and sound.

Constipation after hernia repair results in strain to evacuate the bowel causing pain, and fear that the sutures may rupture. Opioid analgesia makes constipation worse. Promoting an easy bowel motion is important post-operatively.

Surgical correction is always recommended for inguinal hernias in child.

Emergency surgery for incarceration and strangulation carry much higher risk than planned, "elective" procedures. However, the risk of incarceration is low, evaluated at 0.2% per year. On the other hand, surgery has a risk of inguinodynia (10-12%), and this is why males with minimal symptoms are advised to watchful waiting. However, if they experience discomfort while doing physical activities or they routinely avoid them by the fear of pain, they should seek surgical evaluation. For female patients, surgery is recommended even for asymptomatic patients.

Many people are managed through day surgery centers, and are able to return to work within a week or two, while intense activities are prohibited for a longer period. People who have their hernias repaired with mesh often recover within a month, though pain can last longer. Surgical complications include pain that lasts more than three months, surgical site infections, nerve and blood vessel injuries, injury to nearby organs, and hernia recurrence. Pain that lasts more than three months occurs in about 10% of people following hernia repair.

About 27% of males and 3% of females develop a groin hernia at some time in their life. In 2013 about 25 million people had a hernia. Inguinal, femoral and abdominal hernias resulted in 32,500 deaths globally in 2013 and 50,500 in 1990.

Testicular factors refer to conditions where the testes produces semen of poor quality despite adequate hormonal support and include:

- Age

- Genetic defects on the Y chromosome

- Y chromosome microdeletions

- Abnormal set of chromosomes

- Klinefelter syndrome

- Neoplasm, e.g. seminoma

- Cryptorchidism

- Varicocele (14% in one study)

- Trauma

- Hydrocele

- Mumps

- Malaria

- Defects in USP26 enzyme in some cases

Mast cells releasing inflammatory mediators appear to directly suppress sperm motility in a potentially reversible manner, and may be a common pathophysiological mechanism for several of the above-mentioned factors.

In about 30% of infertile men no causative factor is found for their decrease in sperm concentration or quality by common clinical, instrumental, or laboratory means, and the condition is termed "idiopathic" (unexplained). A number of factors may be involved in the genesis of this condition, including age, infectious agents ( such as "Chlamydia trachomatis"), Y chromosome microdeletions, mitochondrial changes, environmental pollutants, and "subtle" hormonal changes.

A review in 2013 came to the result that oligospermia and azoospermia are significantly associated with being overweight (odds ratio 1.1), obese (odds ratio 1.3) and morbidly obese (odds ratio 2.0), but the cause of this is unknown. It found no significant relation between oligospermia and being underweight.

This disease is more common in women and an association with the gene FLT4 has been described. FLT4 codes for VEGFR-3, which is implicated in development of the lymphatic system.

Milroy's disease is also known as primary or hereditary lymphedema type 1A or early onset lymphedema.

It is a very rare disease with only about 200 cases reported in the medical literature. Milroy's disease is an autosomal dominant condition caused by a mutation in the FLT4 gene which encodes of the vascular endothelial growth factor receptor 3 (VEGFR-3) gene located on the long arm (q) on chromosome 5 (5q35.3).

In contrast to Milroy's disease (early onset lymphedema type 1A,) which typically has its onset of swelling and edema at birth or during early infancy, hereditary lymphedema type II, known as Meige disease, has its onset around the time of puberty. Meige disease is also an autosomal dominant disease. It has been linked to a mutations in the ‘forkhead’ family transcription factor (FOXC2) gene located on the long arm of chromosome 16 (16q24.3). About 2000 cases have been identified. A third type of hereditary lymphedema, that has an onset after the age of 35 is known as lymph-edema tarda.

Milroy's disease (MD) is a familial disease characterized by lymphedema, commonly in the legs, caused by congenital abnormalities in the lymphatic system. Disruption of the normal drainage of lymph leads to fluid accumulation and hypertrophy of soft tissues. It is also known as Milroy disease, Nonne-Milroy-Meige syndrome and hereditary lymphedema.

It was named by Sir William Osler for William Milroy, a Canadian physician, who described a case in 1892, though it was first described by Rudolf Virchow in 1863.

Mansonelliasis (or mansonellosis) is the condition of infection by the nematode "Mansonella".

The disease exists in Africa and tropical Americas, spread by biting midges or blackflies. It is usually asymptomatic.

Mansonelliasis is found in Latin America from the Yucatán peninsula to northern Argentina, in the Caribbean, and in Africa from Senegal to Kenya and south to Angola and Zimbabwe. "M. ozzardi" is found only in the New World, "M. steptocerca" is found only in the Congo basin, and "M. perstans" is found in both the previously described areas of Africa and Latin America. Prevalence rates vary from a few percent to as much as 90% in areas like Trinidad, Guyana and Colombia.

Infection is more common and has a higher microfilarial dose with age, though studies have found microfilarial dose not to be correlated with symptoms. In parts of rural South America, men have been found more susceptible than women, possibly due to more outdoors work by males as children, and possibly due to cooking fires serving as deterrents to vectors for women who perform more domestic duties. One study in central Africa found "M. perstans" to be a much more common cause of filariasis symptoms compared to Loa loa and Wuchereria bancrofti.

Since most Mansonelliasis is asymptomatic, it has been considered a relatively minor filarial disease, and has a very low, if any, mortality, though there is little data to base estimates on.

The World Health Organization recommends mass deworming—treating entire groups of people who are at risk with a single annual dose of two medicines, namely albendazole in combination with either ivermectin or diethylcarbamazine citrate. With consistent treatment, since the disease needs a human host, the reduction of microfilariae means the disease will not be transmitted, the adult worms will die out, and the cycle will be broken. In sub-Saharan Africa, albendazole (donated by GlaxoSmithKline) is being used with ivermectin (donated by Merck & Co.) to treat the disease, whereas elsewhere in the world, albendazole is used with diethylcarbamazine. Transmission of the infection can be broken when a single dose of these combined oral medicines is consistently maintained annually for a duration of four to six years. Using a combination of treatments better reduces the number of microfilariae in blood. Avoiding mosquito bites, such as by using insecticide-treated mosquito bed nets, also reduces the transmission of lymphatic filariasis.

The Carter Center's International Task Force for Disease Eradication declared lymphatic filariasis one of six potentially eradicable diseases. According to medical experts, the worldwide effort to eliminate lymphatic filariasis is on track to potentially succeed by 2020.

For similar-looking but causally unrelated podoconiosis, international awareness of the disease will have to increase before elimination is possible. In 2011, podoconiosis was added to the World Health Organization's Neglected Tropical Diseases list, which was an important milestone in raising global awareness of the condition.

The efforts of the Global Programme to Eliminate LF are estimated to have prevented 6.6 million new filariasis cases from developing in children between 2000 and 2007, and to have stopped the progression of the disease in another 9.5 million people who had already contracted it. Dr. Mwele Malecela, who chairs the programme, said: "We are on track to accomplish our goal of elimination by 2020." In 2010, the WHO published a detailed progress report on the elimination campaign in which they assert that of the 81 countries with endemic LF, 53 have implemented mass drug administration, and 37 have completed five or more rounds in some areas, though urban areas remain problematic.

Elephantiasis occurs in the presence of microscopic, thread-like parasitic worms such as "Wuchereria bancrofti" (the most common), "Brugia malayi", and "Brugia timori" (also known as "B. timori"), all of which are transmitted by bites from infected mosquitoes. It is a type of helminth infection. Three types of worm cause the disease and damage the lymphatic system:

The disease itself is a result of a complex interplay between several factors: the worm, the endosymbiotic "Wolbachia" bacteria within the worm, the host’s immune response, and the numerous opportunistic infections and disorders that arise. The adult worms only live in the human lymphatic system. The parasite infects the lymph nodes and blocks the flow of lymph throughout the body; this results in chronic lymphedema, most often noted in the lower torso (typically in the legs and genitals).

Secondary bacterial infection is common among patients with filariasis. Compromised immune function due to lymphatic damage in addition to lymph node ulcerations and abscesses exposure and impaired circulation due to elephantiasis can cause secondary bacterial or fungal infection. Elephantiasis, in addition to the physical burden of a swollen limb, can be a severely dehabilitating condition given bacterial infection. Part of the WHO's "Strategy to Eliminate Lymphatic Filariasis" targets hygiene promotion programs in order to alleviate the suffering of affected individuals (see Prevention Strategies).

However, clinical manifestations of infection are variable and depend on several factors, including host immune system, infectious dose, and parasite strain differences. Most infections appear asymptomatic, yet vary from individual to individual. Individuals living in endemic areas with microfilaremia may never present with overt symptoms, whereas in other cases, only a few worms can exacerbate a severe inflammatory response.

The development of the disease in humans, however, is not well understood. Adults typically develop worse symptoms, given the long exposure time required for infection. Infection may occur during childhood, but the disease appears to take many years to manifest. The incubation period for infection ranges from 1 month to 2 years and typically microfilariae appear before overt symptoms. Lymphedema can develop within six months and development of elephantiasis has been reported within a year of infection among refugees, who are more immunologically naive. Men tend to develop worse symptoms than women.

Wuchereria bancrofti is a human parasitic roundworm that is the major cause of lymphatic filariasis. It is one of the three parasitic worms, together with "Brugia malayi" and "B. timori", that infect the lymphatic system to cause lymphatic filariasis. These filarial worms are spread by a variety of mosquito vector species. "W. bancrofti" is the most prevalent of the three and affects over 120 million people, primarily in Central Africa and the Nile delta, South and Central America, the tropical regions of Asia including southern China, and the Pacific islands. If left untreated, the infection can develop into a chronic disease called elephantiasis. In rare conditions it also causes tropical eosinophilia, an asthmatic disease. There is no commercially available vaccine however high rates of cure have been achieved with various anti-filarial regimens and lymphatic filariasis is the target of the WHO Global Program to Eliminate Lymphatic Filariasis with the aim to eradicate the disease as a public health problem by 2020.

Prevention focuses on protecting against mosquito bites in endemic regions. Insect repellents and mosquito nets are useful to protect against mosquito bites. Public education efforts must also be made within the endemic areas of the world to successfully lower the prevalence of "W. bancrofti" infections.