In the United Kingdom, NGU is more often called non-specific urethritis; "" is a medical term meaning "specific cause has not been identified", and in this case refers to the detection of urethritis, and the testing for but found negative of gonorrhea. In this sense, the most likely cause of NSU is a chlamydia infection.

However, the term NSU is sometimes distinguished and used to mean that both gonorrhea and chlamydia have been ruled out. Thus, depending on the sense, chlamydia can either be the most likely cause or have been ruled out, and frequently detected organisms are "Ureaplasma urealyticum" and "Mycoplasma hominis".

It has been easy to test for the presence of gonorrhea by viewing a Gram stain of the urethral discharge under a microscope: The causative organism is distinctive in appearance; however, this works only with men because other non-pathogenic gram-negative microbes are present as normal flora of the vagina in women. Thus, one of the major causes of urethritis can be identified (in men) by a simple common test, and the distinction between gonococcal and non-gonococcal urethritis arose for this reason.

Non-gonococcal urethritis (NGU) is diagnosed if a person with urethritis has no signs of gonorrhea bacteria on laboratory tests. The most frequent cause of NGU (23%-55% of cases) is "C. trachomatis".

For sexually active women who are not pregnant, screening is recommended in those under 25 and others at risk of infection. Risk factors include a history of chlamydial or other sexually transmitted infection, new or multiple sexual partners, and inconsistent condom use. For pregnant women, guidelines vary: screening women with age or other risk factors is recommended by the U.S. Preventive Services Task Force (USPSTF) (which recommends screening women under 25) and the American Academy of Family Physicians (which recommends screening women aged 25 or younger). The American College of Obstetricians and Gynecologists recommends screening all at risk, while the Centers for Disease Control and Prevention recommend universal screening of pregnant women. The USPSTF acknowledges that in some communities there may be other risk factors for infection, such as ethnicity. Evidence-based recommendations for screening initiation, intervals and termination are currently not possible. For men, the USPSTF concludes evidence is currently insufficient to determine if regular screening of men for chlamydia is beneficial. They recommend regular screening of men who are at increased risk for HIV or syphilis infection.

In the United Kingdom the National Health Service (NHS) aims to:

1. Prevent and control chlamydia infection through early detection and treatment of asymptomatic infection;

2. Reduce onward transmission to sexual partners;

3. Prevent the consequences of untreated infection;

4. Test at least 25 percent of the sexually active under 25 population annually.

5. Retest after treatment.

If symptomatic, testing is recommended. The risk of contracting Micoplasma infection can be reduced by the following:

- Using barrier methods such as condoms

- Seeking medical attention if you are experiencing symptoms suggesting a sexually transmitted infection.

- Seeking medical attention after learning that a current or former sex partner has, or might have had a sexually transmitted infection.

- Getting a STI history from your current partner and insisting they be tested and treated before intercourse.

- Avoiding vaginal activity, particularly intercourse, after the end of a pregnancy (delivery, miscarriage, or abortion) or certain gynecological procedures, to ensure that the cervix closes.

- Abstinence

In female patients, urethritis can be caused by pelvic inflammatory disease.

In males, thepenis and testicles may show signs of pain and swelling. The urethra is visually examined by spreading the urinary meatus apart with two gloved fingers, and examining the opening for redness, discharge and other abnormalities. Next, a cotton swab is inserted 1-4 cm into the urethra and rotated once. To prevent contamination, no lubricant is applied to the swab, which can result in pain or discomfort. The swab is then smeared onto a glass slide and examined under a microscope. A commonly used cut-off for the diagnosis of urethritis is 5 or more granulocytes per High Power Field, but this definition has recently been called into doubt. The physician sometimes performs a digital rectal examination to inspect the prostate gland for swelling or infection.

A urinary tract infection may cause similar symptoms.

The diagnosis of genital chlamydial infections evolved rapidly from the 1990s through 2006. Nucleic acid amplification tests (NAAT), such as polymerase chain reaction (PCR), transcription mediated amplification (TMA), and the DNA strand displacement amplification (SDA) now are the mainstays. NAAT for chlamydia may be performed on swab specimens sampled from the cervix (women) or urethra (men), on self-collected vaginal swabs, or on voided urine. NAAT has been estimated to have a sensitivity of approximately 90% and a specificity of approximately 99%, regardless of sampling from a cervical swab or by urine specimen. In women seeking an STI clinic and a urine test is negative, a subsequent cervical swab has been estimated to be positive in approximately 2% of the time.

At present, the NAATs have regulatory approval only for testing urogenital specimens, although rapidly evolving research indicates that they may give reliable results on rectal specimens.

Because of improved test accuracy, ease of specimen management, convenience in specimen management, and ease of screening sexually active men and women, the NAATs have largely replaced culture, the historic gold standard for chlamydia diagnosis, and the non-amplified probe tests. The latter test is relatively insensitive, successfully detecting only 60–80% of infections in asymptomatic women, and often giving falsely positive results. Culture remains useful in selected circumstances and is currently the only assay approved for testing non-genital specimens. Other method also exist including: ligase chain reaction (LCR), direct fluorescent antibody resting, enzyme immunoassay, and cell culture.

Use of male condoms or female condoms may help prevent the spread of trichomoniasis, although careful studies have never been done that focus on how to prevent this infection. Infection with Trichomoniasis through water is unlikely because "Trichomonas vaginalis" dies in water after 45–60 minutes, in thermal water after 30 minutes to 3 hours and in d urine after 5–6 hours.

Currently there are no routine standard screening requirements for the general U.S. population receiving family planning or STI testing. The Centers for Disease Control and Prevention (CDC) recommends Trichomoniasis testing for females with vaginal discharge and can be considered for females at higher risk for infection or of HIV-positive serostatus.

The advent of new, highly specific and sensitive trichomoniasis tests present opportunities for new screening protocols for both men and women. Careful planning, discussion, and research are required to determine the cost-efficiency and most beneficial use of these new tests for the diagnosis and treatment of trichomoniasis in the U.S., which can lead to better prevention efforts.

A number of strategies have been found to improve follow-up for STI testing including email and text messaging as reminders of appointments.

Mucopurulent cervicitis (MPC) is characterized by a purulent or mucopurulent endocervical exudate visible in the endocervical canal or in an endocervical swab specimen. Some specialists also diagnose MPC on the basis of easily induced cervical bleeding. Although some specialists consider an increased number of polymorphonuclear white blood cells on endocervical Gram stain as being useful in the diagnosis of MPC, this criterion has not been standardized, has a low positive-predictive value (PPV), and is not available in some settings. MPC often is without symptoms, but some women have an abnormal vaginal discharge and vaginal bleeding (e.g., after sexual intercourse). MPC can be caused by "Chlamydia trachomatis" or "Neisseria gonorrhoeae"; however, in most cases neither organism can be isolated. MPC can persist despite repeated courses of antimicrobial therapy. Because relapse or reinfection with "C. trachomatis" or "N. gonorrhoeae" usually does not occur in persons with persistent cases of MPC, other non-microbiologic determinants (e.g., inflammation in the zone of ectopy) might be involved.

Patients who have MPC should be tested for "C. trachomatis" and for "N. gonorrhoeae" with the most sensitive and specific test available. However, MPC is not a sensitive predictor of infection with these organisms; most women who have "C. trachomatis" or "N. gonorrhoeae" do not have MPC.

Risk of some causes of urethritis can be lessened by avoiding unprotected sexual activity, chemicals that could irritate the urethra; this could include detergents or lotions as well as spermicides or contraceptives, and irritation caused by manual manipulation of the urethra.

Neonatal sepsis of the newborn is an infection that has spread through the entire body. The inflammatory response to this systematic infection can be as serious as the infection itself. In infants that weigh under 1500 g, sepsis is the most common cause of death. Three to four percent of infants per 1000 births contract sepsis. The mortality rate from sepsis is near 25%. Infected sepsis in an infant can be identified by culturing the blood and spinal fluid and if suspected, intravenous antibiotics are usually started. Lumbar puncture is controversial because in some cases it has found not to be necessary while concurrently, without it estimates of missing up to one third of infants with meningitis is predicted.

There are three main ways to test for Trichomoniasis.

- The first is known as saline microscopy. This is the most commonly used method and requires an endocervical, vaginal, or penile swab specimen for examination under a microscope. The presence of one or multiple trichomonads constitutes a positive result. This method is cheap but has a low sensitivity (60-70%) often due to an inadequate sample, resulting in false negatives.

- The second diagnostic method is culture, which has historically been the "gold standard" in infectious disease diagnosis. Trichomonas Vaginalis culture tests are relatively cheap; however, sensitivity is still somewhat low (70-89%).

- The third method includes the nucleic acid amplification tests (NAATs) which are more sensitive. These tests are more costly than microscopy and culture, and are highly sensitive (80-90%).

Mycoplasmas have a triple-layered membrane and lack a cell wall. Commonly used antibiotics are generally ineffective because their efficacy is due to their ability to inhibit cell wall synthesis. Micoplasmas are not affected by penicillins and other antibiotics that act on the cell wall. The growth of micoplasmas in their host is inhibited by other broad-spectrum antibiotics. These broad-spectrum antibiotics inhibit the multiplication of the mycoplasma but does not kill them. Tetracyclines, macrolides, erythromycin, macrolides, ketolides, quinolones are used to treat mycoplasma infections. In addition to the penicillins, mycoplasmas are resistant to rifampicin. Mycoplasmas may be difficult to eradicate from human or animal hosts or from cell cultures by antibiotic treatment because of resistance to the antibiotic, or because it does not kill the mycoplasma cell. Mycoplasma cells are able to invade the cells of their hosts.

To make the diagnosis of a urinary tract infection in children, a positive urinary culture is required. Contamination poses a frequent challenge depending on the method of collection used, thus a cutoff of 10 CFU/mL is used for a "clean-catch" mid stream sample, 10 CFU/mL is used for catheter-obtained specimens, and 10 CFU/mL is used for suprapubic aspirations (a sample drawn directly from the bladder with a needle). The use of "urine bags" to collect samples is discouraged by the World Health Organization due to the high rate of contamination when cultured, and catheterization is preferred in those not toilet trained. Some, such as the American Academy of Pediatrics recommends renal ultrasound and voiding cystourethrogram (watching a person's urethra and urinary bladder with real time x-rays while they urinate) in all children less than two years old who have had a urinary tract infection. However, because there is a lack of effective treatment if problems are found, others such as the National Institute for Health and Care Excellence only recommends routine imaging in those less than six months old or who have unusual findings.

In straightforward cases, a diagnosis may be made and treatment given based on symptoms alone without further laboratory confirmation. In complicated or questionable cases, it may be useful to confirm the diagnosis via urinalysis, looking for the presence of urinary nitrites, white blood cells (leukocytes), or leukocyte esterase. Another test, urine microscopy, looks for the presence of red blood cells, white blood cells, or bacteria. Urine culture is deemed positive if it shows a bacterial colony count of greater than or equal to 10 colony-forming units per mL of a typical urinary tract organism. Antibiotic sensitivity can also be tested with these cultures, making them useful in the selection of antibiotic treatment. However, women with negative cultures may still improve with antibiotic treatment. As symptoms can be vague and without reliable tests for urinary tract infections, diagnosis can be difficult in the elderly.

Salpingitis may be diagnosed by pelvic examination, blood tests, and/or a vaginal or cervical swab.

Symptoms and the isolation of the virus pathogen the upper respiratory tract is diagnostic. Virus identification is specific immunologic methods and PCR. The presence of the virus can be rapidly confirmed by the detection of the virus antigen. The methods and materials used for identifying the RSV virus has a specificity and sensitivity approaching 85% to 95%. Not all studies confirm this sensitivity. Antigen detection has comparatively lower sensitivity rates that approach 65% to 75%.

Regular testing for sexually transmitted infections is encouraged for prevention. The risk of contracting pelvic inflammatory disease can be reduced by the following:

- Using barrier methods such as condoms; see human sexual behavior for other listings.

- Seeking medical attention if you are experiencing symptoms of PID.

- Using hormonal combined contraceptive pills also helps in reducing the chances of PID by thickening the cervical mucosal plug & hence preventing the ascent of causative organisms from the lower genital tract.

- Seeking medical attention after learning that a current or former sex partner has, or might have had a sexually transmitted infection.

- Getting a STI history from your current partner and strongly encouraging they be tested and treated before intercourse.

- Diligence in avoiding vaginal activity, particularly intercourse, after the end of a pregnancy (delivery, miscarriage, or abortion) or certain gynecological procedures, to ensure that the cervix closes.

- Reducing the number of sexual partners.

- Sexual monogamy.

- Abstinence

A number of other causes may produce similar symptoms including appendicitis, ectopic pregnancy, hemorrhagic or ruptured ovarian cysts, ovarian torsion, and endometriosis and gastroenteritis, peritonitis, and bacterial vaginosis among others.

Pelvic inflammatory disease is more likely to reoccur when there is a prior history of the infection, recent sexual contact, recent onset of menses, or an IUD (intrauterine device) in place or if the partner has a sexually transmitted infection.

Acute pelvic inflammatory disease is highly unlikely when recent intercourse has not taken place or an IUD is not being used. A sensitive serum pregnancy test is typically obtained to rule out ectopic pregnancy. Culdocentesis will differentiate hemoperitoneum (ruptured ectopic pregnancy or hemorrhagic cyst) from pelvic sepsis (salpingitis, ruptured pelvic abscess, or ruptured appendix).

Pelvic and vaginal ultrasounds are helpful in the diagnosis of PID. In the early stages of infection, the ultrasound may appear normal. As the disease progresses, nonspecific findings can include free pelvic fluid, endometrial thickening, uterine cavity distension by fluid or gas. In some instances the borders of the uterus and ovaries appear indistinct. Enlarged ovaries accompanied by increased numbers of small cysts correlates with PID.

Laparoscopy is infrequently used to diagnose pelvic inflammatory disease since it is not readily available. Moreover, it might not detect subtle inflammation of the fallopian tubes, and it fails to detect endometritis. Nevertheless, laparoscopy is conducted if the diagnosis is not certain or if the person has not responded to antibiotic therapy after 48 hours.

No single test has adequate sensitivity and specificity to diagnose pelvic inflammatory disease. A large multisite U.S. study found that cervical motion tenderness as a minimum clinical criterion increases the sensitivity of the CDC diagnostic criteria from 83 percent to 95 percent. However, even the modified 2002 CDC criteria do not identify women with subclinical disease.

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.

Over one million cases of acute salpingitis are reported every year in the US, but the number of incidents is probably larger, due to incomplete and untimely reporting methods and that many cases are reported first when the illness has gone so far that it has developed chronic complications. For women age 16–25, salpingitis is the most common serious infection. It affects approximately 11% of females of reproductive age.

Salpingitis has a higher incidence among members of lower socioeconomic classes. However, this is thought of being an effect of earlier sex debut, multiple partners, and decreased ability to receive proper health care rather than any independent risk factor for salpingitis.

As an effect of an increased risk due to multiple partners, the prevalence of salpingitis is highest for people age 15–24 years. Decreased awareness of symptoms and less will to use contraceptives are also common in this group, raising the occurrence of salpingitis.

There are no definitive diagnostic tests for CP/CPPS. This is a poorly understood disorder, even though it accounts for 90–95% of prostatitis diagnoses. It is found in men of any age, with the peak incidence in men aged 35–45 years. CP/CPPS may be inflammatory (Category Ⅲa) or non-inflammatory (Category Ⅲb), based on levels of pus cells in expressed prostatic secretions (EPS), but these subcategories are of limited use clinically. In the inflammatory form, urine, semen, and other fluids from the prostate contain pus cells (dead white blood cells or WBCs), whereas in the non-inflammatory form no pus cells are present. Recent studies have questioned the distinction between categories Ⅲa and Ⅲb, since both categories show evidence of inflammation if pus cells are ignored and other more subtle signs of inflammation, like cytokines, are measured.

In 2006, Chinese researchers found that men with categories Ⅲa and Ⅲb both had significantly and similarly raised levels of anti-inflammatory cytokine TGFβ1 and pro-inflammatory cytokine IFN-γ in their EPS when compared with controls; therefore measurement of these cytokines could be used to diagnose category Ⅲ prostatitis. A 2010 study found that nerve growth factor could also be used as a biomarker of the condition.

For CP/CPPS patients, analysis of urine and expressed prostatic secretions for leukocytes is debatable, especially due to the fact that the differentiation between patients with inflammatory and non-inflammatory subgroups of CP/CPPS is not useful. Serum PSA tests, routine imaging of the prostate, and tests for Chlamydia trachomatis and Ureaplasma provide no benefit for the patient.

Extraprostatic abdominal/pelvic tenderness is present in >50% of patients with chronic pelvic pain syndrome but only 7% of controls.

Healthy men have slightly more bacteria in their semen than men with CPPS. The high prevalence of WBCs and positive bacterial cultures in the asymptomatic control population raises questions about the clinical usefulness of the standard 4-glass test as a diagnostic tool in men with CP/CPPS. The use of the four-glass test by American urologists is now rare, with only 4% using it regularly.

Men with CP/CPPS are more likely than the general population to suffer from Chronic Fatigue Syndrome (CFS), and Irritable Bowel Syndrome (IBS).

Experimental tests that could be useful in the future include tests to measure semen and prostate fluid cytokine levels. Various studies have shown increases in markers for inflammation such as elevated levels of cytokines, myeloperoxidase, and chemokines.

A number of other conditions can cause fevers following delivery including: urinary tract infections, breast engorgement, atelectasis and surgical incisions among others.

Cervicitis can be caused by any of a number of infections, of which the most common are chlamydia and gonorrhea, with chlamydia accounting for approximately 40% of cases. As many half of pregnant women are asymptomatic with a gonorrhea infection of the cervix. "Trichomonas vaginalis" and herpes simplex are less common causes of cervicitis. There is a consistent association of M. genitalium infection and female reproductive tract syndromes. M. genitalium infection is significantly associated with increased risk of cervicitis.

Some conditions have similar symptoms to chronic prostatitis: Bladder neck hypertrophy and urethral stricture may both cause similar symptoms through urinary reflux ("inter alia"), and can be excluded through flexible cytoscopy and urodynamic tests.