Diagnosis is typically based on symptoms. Conditions that may result in similar symptoms include testicular torsion, inguinal hernia, and testicular cancer. Ultrasound can be useful if the diagnosis is unclear.

Epididymitis usually has a gradual onset. Typical findings are redness, warmth and swelling of the scrotum, with tenderness behind the testicle, away from the middle (this is the normal position of the epididymis relative to the testicle). The cremasteric reflex (elevation of the testicle in response to stroking the upper inner thigh) remains normal. This is a useful sign to distinguish it from testicular torsion. If there is pain relieved by elevation of the testicle, this is called Prehn's sign, which is, however, non-specific and is not useful for diagnosis.

Before the advent of sophisticated medical imaging techniques, surgical exploration was the standard of care. Today, Doppler ultrasound is a common test: it can demonstrate areas of blood flow and can distinguish clearly between epididymitis and torsion. However, inasmuch as torsion and other sources of testicular pain can consistently be determined by palpation alone, some studies have suggested that the only real benefit of an ultrasound, which is a fairly expensive procedure (~US$300 to US$800 in 2013), is to assure the patient that he does not have testicular cancer. Nuclear testicular blood flow testing is rarely used.

Additional tests may be necessary to identify underlying causes. In younger children, a urinary tract anomaly is frequently found. In sexually active men, tests for sexually transmitted diseases may be done. These may include microscopy and culture of a first void urine sample, Gram stain and culture of fluid or a swab from the urethra, nucleic acid amplification tests (to amplify and detect microbial DNA or other nucleic acids) or tests for syphilis and HIV.

Epididymitis can be classified as acute, subacute, and chronic, depending on the duration of symptoms.

Useful tests that may help in the determination of the cause include a urinalysis (usually normal in testicular torsion). Pyuria and bacteriuria (white blood cells and bacteria in the urine) in patients with acute scrotum suggests an infectious cause such as epididymitis or orchitis and specific testing for gonorrhea and chlamydia should be done. All people with chronic pain should be tested for gonorrhea and chlamydia.

Ultrasound is useful if the cause is not certain based on the above measures. If the diagnosis of torsion is certain, imaging should not delay definitive management such as physical maneuvers and surgery.

Testing for gonorrhea and chlamydia should be routinely performed.

A doppler ultrasound scan of the scrotum is nearly 90% accurate in diagnosis identifying the absence of blood flow in the twisted testicle, which distinguishes torsion from epididymitis.

Radionuclide scanning of the scrotum is the most accurate, imaging technique, but it is not routinely available, particularly with the urgency that might be required. The agent of choice for this purpose is technetium-99m pertechnetate. Initially it provides a radionuclide angiogram, followed by a static image after the radionuclide has perfused the tissue. In the healthy patient, initial images show symmetric flow to the testes, and delayed images show uniformly symmetric activity.

Prehn's sign, a classic physical exam finding, has not been reliable in distinguishing torsion from other causes of testicular pain such as epididymitis. In cases of true torsion the cremasteric reflex is typically absent (the twisted cords of the testicle make reflexive responses all but impossible). On physical examination, the testis will be swollen, tender, and high-riding, with an abnormal transverse lie. The individual will not usually have a fever, though nausea is common.

Through diagnostic ultrasound the accumulation of fluids can be diagnosed correctly.

Treatment is often with NSAIDs and antibiotics however, this is not always effective.

The two most common surgical approaches are retroperitoneal (abdominal using laparoscopic surgery), infrainguinal/subinguinal (below the groin) and inguinal (groin using percutaneous embolization). Possible complications of this procedure include hematoma (bleeding into tissues), hydrocele (accumulation of fluid around the affected testicle), infection, or injury to the scrotal tissue or structures. In addition, injury to the artery that supplies the testicle may occur, resulting in a loss of a testicle.

Whether having variocele surgery or embolization improves male fertility is controversial, as good clinical data are lacking. There is tentative evidence that varicoceletomy may improve fertility in those with obvious findings and abnormal sperm; however, this has a number needed to treat of 7 for varicoceletomy and 17 for embolization. There are also studies showing that the regular surgery has no significant effect on infertility. A 2012 Cochrane review found tentative but unclear evidence of improved fertility among males treated for varicocele.

Spermatoceles can be discovered as incidental scrotal masses found on physical examination by a physician. They may also be discovered by self-inspection of the scrotum and testicles.

Finding a painless, cystic mass at the head of the epididymis, that transilluminates and can be clearly differentiated from the testicle, is generally sufficient. If uncertainty exists, ultrasonography of the scrotum can confirm if it is spermatocele.

If an individual finds what he suspects to be a spermatocele, he is advised to consult a urologist.

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.

Because polyorchidism is very uncommon, there is no standard treatment for the condition. Prior to advances in ultrasound technology, it was common practice to remove the supernumerary testicle. Several cases have been described where routine follow-up examinations conducted over a period of years showed that the supernumerary testicle was stable.

A meta-analysis in 2009 suggested removing non-scrotal supernumerary testicles because of the increased risk of cancer, and regular follow-up in the remaining cases to ensure that the supernumerary testicle remains stable.

A retrospective postal survey of 396 men found that 4% had significant genital pain for more than one year that required surgical intervention.

Another study contacted 470 vasectomy patients and received 182 responses, finding that 18.7% of respondents experienced chronic genital pain with 2.2% of respondents experiencing pain that adversely affected quality of life.

The most robust study of post-vasectomy pain, according to the American Urology Association's Vasectomy Guidelines 2012 (amended 2015) found a rate of 14.7% reported new-onset scrotal pain at 7 months after vasectomy with 0.9% describing the pain as "quite severe and noticeably affecting their quality of life".

A primary hydrocele is described as having the following characteristics:

- Transillumination positive

- Fluctuation positive

- Impulse on coughing negative (positive in congenital hydrocele)

- Reducibility absent

- Testis cannot be palpated separately. (exception - funicular hydrocele, encysted hydrocele)kuth

- Can get above the swelling.

The fluid accumulation can be drained by aspiration, but this may be only temporary. A more permanent alternative is a surgical procedure, generally, an outpatient ambulatory (same-day) procedure, called a hydrocelectomy. There are two surgical techniques available for hydrocelectomy.

- Hydrocelectomy with Excision of the Hydrocele Sac: Incision of the hydrocele sac after complete mobilization of the hydrocele. Partial resection of the hydrocele sac, leaving a margin of 1–2 cm. Care is taken not to injure testicular vessels, epididymis or ductus deferens. The edge of the hydrocele sac is oversewn for hemostasis (von Bergmann's technique) or the edges are sewn together behind the spermatic cord (Winkelmann's or Jaboulay's technique). Hydrocele surgery with excision of the hydrocele sac is useful for large or thick-walled hydroceles and multilocular hydroceles.

- Hydrocele Surgery with Plication of the Hydrocele Sac: The hydrocele is opened with a small skin incision without further preparation. The hydrocele sac is reduced (plicated) by suture Hydrocele surgery: Lord's technique. The plication technique is suitable for medium-sized and thin-walled hydroceles. The advantage of the plication technique is the minimized dissection with a reduced complication rate.

If the hydrocele is not surgically removed, it may continue to grow. The hydrocele fluid can be aspirated. This procedure can be done in a urologist's office or clinic and is less invasive but, recurrence rates are high. Sclerotherapy, the injection of a solution following aspiration of the hydrocele fluid may increase success rates. In many patients, the procedure of aspiration and sclerotherapy is repeated as the hydrocele recurs.

Treatment depends on the proximate cause. In one study, it was reported that 9 of 13 men who underwent vasectomy reversal in an attempt to relieve post-vasectomy pain syndrome became pain-free, though the followup was only one month in some cases. Another study found that 24 of 32 men had relief after vasectomy reversal.

Nerve entrapment is treated with surgery to free the nerve from the scar tissue, or to cut the nerve. One study reported that denervation of the spermatic cord provided complete relief at the first follow-up visit in 13 of 17 cases, and that the other four patients reported improvement. As nerves may regrow, long-term studies are needed.

One study found that epididymectomy provided relief for 50% of patients with post-vasectomy pain syndrome.

Orchiectomy is recommended usually only after other surgeries have failed.

Small cysts are best left alone, as are larger cysts that are an asymptomatic condition. Only when the cysts are causing discomfort and are enlarging in size, or the patient wants the spermatocele removed, should a spermatocelectomy be considered. Pain may persist even after removal.

Spermatocelectomy can be performed on an outpatient basis, with the use of local or general anesthesia.

A spermatocelectomy will not improve fertility.

Some strategies suggested or proposed for avoiding male infertility include the following:

- Avoiding smoking as it damages sperm DNA

- Avoiding heavy marijuana and alcohol use.

- Avoiding excessive heat to the testes.

- Maintaining optimal frequency of coital activity: sperm counts can be depressed by daily coital activity and sperm motility may be depressed by coital activity that takes place too infrequently (abstinence 10–14 days or more).

- Wearing a protective cup and jockstrap to protect the testicles, in any sport such as baseball, football, cricket, lacrosse, hockey, softball, paintball, rodeo, motorcross, wrestling, soccer, karate or other martial arts or any sport where a ball, foot, arm, knee or bat can come into contact with the groin.

- Diet: Healthy diets (i.e. the Mediterranean diet) rich in such nutrients as omega-3 fatty acids, some antioxidants and vitamins, and low in saturated fatty acids (SFAs) and trans-fatty acids (TFAs) are inversely associated with low semen quality parameters. In terms of food groups, fish, shellfish and seafood, poultry, cereals, vegetables and fruits, and low-fat dairy products have been positively related to sperm quality. However, diets rich in processed meat, soy foods, potatoes, full-fat dairy products, coffee, alcohol and sugar-sweetened beverages and sweets have been inversely associated with the quality of semen in some studies. The few studies relating male nutrient or food intake and fecundability also suggest that diets rich in red meat, processed meat, tea and caffeine are associated with a lower rate of fecundability. This association is only controversial in the case of alcohol. The potential biological mechanisms linking diet with sperm function and fertility are largely unknown and require further study.

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.

Azoospermia is usually detected in the course of an infertility investigation. It is established on the basis of two semen analysis evaluations done at separate occasions (when the seminal specimen after centrifugation shows no sperm under the microscope) and requires a further work-up.

The investigation includes a history, a physical examination including a thorough evaluation of the scrotum and testes, laboratory tests, and possibly imaging. History includes the general health, sexual health, past fertility, libido, and sexual activity. Past exposure to a number of agents needs to be queried including medical agents like hormone/steroid therapy, antibiotics, 5-ASA inhibitors (sulfasalazine), alpha-blockers, 5 alpha-reductase inhibitors, chemotherapeutic agents, pesticides, recreational drugs (marijuana, excessive alcohol), and heat exposure of the testes. A history of surgical procedures of the genital system needs to be elicited. The family history needs to be assessed to look for genetic abnormalities.

Congenital absence of the vas deferens may be detectable on physical examination and can be confirmed by a transrectal ultrasound (TRUS). If confirmed genetic testing for cystic fibrosis is in order. Transrectal ultrasound can also assess azoospermia caused by obstruction, or anomalies related to obstruction of the ejaculatory duct, such as abnormalities within the duct itself, a median cyst of the prostate (indicating a need for cyst aspiration), or an impairment of the seminal vesicles to become enlarged or emptied.

Retrograde ejaculation is diagnosed by examining a postejaculatory urine for presence of sperm after making it alkaline and centifuging it.

Low levels of LH and FSH with low or normal testosterone levels are indicative of pretesticular problems, while high levels of gonadotropins indicate testicular problems. However, often this distinction is not clear and the differentiation between obstructive versus non-obstructive azoospermia may require a testicular biopsy. On the other hand, "In azoospermic men with a normal ejaculate volume, FSH serum level greater than two times the upper limit of the normal range is reliably diagnostic of dysfunctional spermatogenesis and, when found, a diagnostic testicular biopsy is usually unnecessary, although no consensus exists in this matter." But also, extremely high levels of FSH (>45 ID/mL) have been correlated with successful microdissection testicular sperm extraction.

Serum inhibin-B weakly indicates presence of sperm cells in the testes, raising chances for successfully achieving pregnancy through testicular sperm extraction (TESE), although the association is not very substantial, having a sensitivity of 0.65 (95% confidence interval [CI]: 0.56–0.74) and a specificity of 0.83 (CI: 0.64–0.93) for prediction the presence of sperm in the testes in non-obstructive azoospermia.

Seminal plasma proteins TEX101 and ECM1 were recently proposed for the differential diagnosis of azoospermia forms and subtypes, and for prediction of TESE outcome. Mount Sinai Hospital, Canada started clinical trial to test this hypothesis in 2016.

It is recommended that men primary hypopituitarism may be linked to a genetic cause, a genetic evaluation is indicated in men with azoospermia due to primary hypopituitarism. Azoospermic men with testicular failure are advised to undergo karyotype and Y-micro-deletion testing.

Ultrasonography of the scrotum is useful when there is a suspicion of some particular diseases. It may detect signs of testicular dysgenesis, which is often related to an impaired spermatogenesis and to a higher risk of testicular cancer. Scrotum ultrasonography may also detect testicular lesions suggestive of malignancy. A decreased testicular vascularization is characteristic of testicular torsion, whereas hyperemia is often observed in epididymo-orchitis or in some malignant conditions such as lymphoma and leukemia. Doppler ultrasonography useful in assessing venous reflux in case of a varicocele, when palpation is unreliable or in detecting recurrence or persistence after surgery, although the impact of its detection and surgical correction on sperm parameters and overall fertility is debated.

Dilation of the head or tail of the epididymis is suggestive of obstruction or inflammation of the male reproductive tract. Such abnormalities are associated with abnormalities in sperm parameters, as are abnormalities in the texture of the epididymis. Scrotal and transrectal ultrasonography (TRUS) are useful in detecting uni- or bilateral congenital absence of the vas deferens (CBAVD), which may be associated with abnormalities or agenesis of the epididymis, seminal vesicles or kidneys, and indicate the need for testicular sperm extraction. TRUS plays a key role in assessing azoospermia caused by obstruction, and detecting distal CBAVD or anomalies related to obstruction of the ejaculatory duct, such as abnormalities within the duct itself, a median cyst of the prostate (indicating a need for cyst aspiration), or an impairment of the seminal vesicles to become enlarged or emptied.

The most common diagnostic dilemma in otherwise normal boys is distinguishing a retractile testis from a testis that will not descend spontaneously into the scrotum. Retractile testes are more common than truly undescended testes and do not need to be operated on. In normal males, as the cremaster muscle relaxes or contracts, the testis moves lower or higher ("retracts") in the scrotum. This cremasteric reflex is much more active in infant boys than older men. A retractile testis high in the scrotum can be difficult to distinguish from a position in the lower inguinal canal. Though there are various maneuvers used to do so, such as using a cross-legged position, soaping the examiner's fingers, or examining in a warm bath, the benefit of surgery in these cases can be a matter of clinical judgment.

In the minority of cases with bilaterally non-palpable testes, further testing to locate the testes, assess their function, and exclude additional problems is often useful. Pelvic ultrasound or magnetic resonance imaging performed and interpreted by a radiologist can often, but not invariably, locate the testes while confirming absence of a uterus. A karyotype can confirm or exclude forms of dysgenetic primary hypogonadism, such as Klinefelter syndrome or mixed gonadal dysgenesis.

Hormone levels (especially gonadotropins and AMH) can help confirm that there are hormonally functional testes worth attempting to rescue, as can stimulation with a few injections of human chorionic gonadotropin to elicit a rise of the testosterone level. Occasionally these tests reveal an unsuspected and more complicated intersex condition.

In the even smaller minority of cryptorchid infants who have other obvious birth defects of the genitalia, further testing is crucial and has a high likelihood of detecting an intersex condition or other anatomic anomalies. Ambiguity can indicate either impaired androgen synthesis or reduced sensitivity. The presence of a uterus by pelvic ultrasound suggests either persistent Müllerian duct syndrome (AMH deficiency or insensitivity) or a severely virilized genetic female with congenital adrenal hyperplasia. An unambiguous micropenis, especially accompanied by hypoglycemia or jaundice, suggests congenital hypopituitarism.

The most common presentation of testicular cancer is a hard, painless lump which can be felt on one of the testis. It is either noticed by a clinician during a routine examination, or the patient themselves. Risk factors for TC include:

- Cryptorchidism

- Family history

- Previous testicular cancer

- Being white

The diagnosis is confirmed in different ways. An ultrasound scan can be used to diagnose to a 90-95% accuracy. Bloods can also be taken to look for elevated tumour markers which is also used to analyse the patient’s response to treatment. 80% of testicular cancer cases are from the 20-34 year old age range

A potential testicular rupture should be evaluated with ultrasound imaging. Testicular rupture is treated with surgery, though the procedure performed depends on the magnitude of the injury and the salvageability of the tissue. An orchiectomy - removal of the affected testis - is done when the testis is not salvageable and leads to reduced semen quality and higher rates of endocrine dysfunction than repair of salvageable tissue.