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.

Analysis of the urine may show signs of urinary tract infection. Specifically, the presence of nitrite and white blood cells on a urine test strip in patients with typical symptoms are sufficient for the diagnosis of pyelonephritis, and are an indication for empirical treatment. Blood tests such as a complete blood count may show neutrophilia. Microbiological culture of the urine, with or without blood cultures and antibiotic sensitivity testing are useful for establishing a formal diagnosis, and are considered mandatory.

The decision to treat bacteriuria depends on the presence of accompany symptoms and comorbidities.

If a kidney stone is suspected (e.g. on the basis of characteristic colicky pain or the presence of a disproportionate amount of blood in the urine), a kidneys, ureters, and bladder x-ray (KUB film) may assist in identifying radioopaque stones. Where available, a noncontrast helical CT scan with 5 millimeter sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis. All stones are detectable on CT scans except very rare stones composed of certain drug residues in the urine. In patients with recurrent ascending urinary tract infections, it may be necessary to exclude an anatomical abnormality, such as vesicoureteral reflux or polycystic kidney disease. Investigations used in this setting include kidney ultrasonography or voiding cystourethrography. CT scan or kidney ultrasonography is useful in the diagnosis of xanthogranulomatous pyelonephritis; serial imaging may be useful for differentiating this condition from kidney cancer.

Ultrasound findings that indicate pyelonephritis are enlargement of the kidney, edema in the renal sinus or parenchyma, bleeding, loss of corticomedullary differentiation, abscess formation, or an areas of poor blood flow on doppler ultrasound. However, ultrasound findings are seen in only 20% to 24% of people with pyelonephritis.

A DMSA scan is a radionuclide scan that uses dimercaptosuccinic acid in assessing the kidney morphology. It is now the most reliable test for the diagnosis of acute pyelonephritis.

Diagnosis is made by history and examination.

In immunocompromised patients, pus is present in the urine but often no organism can be cultured. In children, polymerase chain reaction sequencing of urine can detect fragments of the infectious agent.

The procedure differs somewhat for women and men. Laboratory testing of urine samples now can be performed with dipsticks that indicate immune system responses to infection, as well as with microscopic analysis of samples. Normal human urine is sterile. The presence of bacteria or pus in the urine usually indicates infection. The presence of hematuria, or blood in the urine, may indicate acute UTIs, kidney disease, kidney stones, inflammation of the prostate (in men), endometriosis (in women), or cancer of the urinary tract. In some cases, blood in the urine results from athletic training, particularly in runners.

Testing for bacteriuria is often performed in those with symptoms of a urinary tract infection. Testing is often done in other scenarios as in failure to thrive of a newborn or confusion in the elderly. Screening for bacteriuria is recommended in pregnancy as there is evidence that asymptomatic bacteriuria can lead to low birth weight and preterm delivery.

- Bacteriuria can be detected by urine dipstick test. The urinary nitrite test will be able to detect any nitrate-reducing bacteria in the urine. The leukocyte esterase test detects the presence of leukocytes (white blood cells) in the urine which can be associated with a urinary tract infection.The urine dipstick test is readily available and provides fast results.

- Microscopy can also be used to detect bacteriuria. It is more specific, especially when used with gram staining, but requires more time and equipment.

- The gold standard for detecting bacteriuria is a bacterial culture which identifies the actual organism. This test is more specific but can take several days to obtain a result. As a result, clinicians will often treat a bacteriuria based on the results of the urine dipstick test while waiting for the culture results. The culture will often provide antibiotic sensitivity.

Bacteriuria can be confirmed if a single bacterial species is isolated in a concentration greater than 100,000 colony forming units per millilitre of urine in clean-catch midstream urine specimens (one for men, two consecutive specimens with the same bacterium for women). For urine collected via bladder catheterization in men and women, a single urine specimen with greater than 100,000 colony forming units of a single species per millilitre is considered diagnostic. The threshold is also 100 colony forming units of a single species per millilitre for women displaying UTI symptoms.

In chronic bacterial prostatitis there are bacteria in the prostate, but there may be no symptoms or milder symptoms than occur with acute prostatitis. The prostate infection is diagnosed by culturing urine as well as prostate fluid (expressed prostatic secretions or EPS) which are obtained by the doctor performing a rectal exam and putting pressure on the prostate. If no fluid is recovered after this prostatic massage, a post massage urine should also contain any prostatic bacteria.

Prostate specific antigen levels may be elevated, although there is no malignancy. Semen analysis is a useful diagnostic tool. Semen cultures are also performed. Antibiotic sensitivity testing is also done to select the appropriate antibiotic. Other useful markers of infection are seminal elastase and seminal cytokines.

Acute prostatitis is relatively easy to diagnose due to its symptoms that suggest infection. The organism may be found in blood or urine, and sometimes in both. Common bacteria are "Escherichia coli, Klebsiella, Proteus, Pseudomonas, Enterobacter, Enterococcus, Serratia," and "Staphylococcus aureus." This can be a medical emergency in some patients and hospitalization with intravenous antibiotics may be required. A complete blood count reveals increased white blood cells. Sepsis from prostatitis is very rare, but may occur in immunocompromised patients; high fever and malaise generally prompt blood cultures, which are often positive in sepsis. A prostate massage should never be done in a patient with suspected acute prostatitis, since it may induce sepsis. Since bacteria causing the prostatitis is easily recoverable from the urine, prostate massage is not required to make the diagnosis. Rectal palpation usually reveals an enlarged, exquisitely tender, swollen prostate gland, which is firm, warm, and, occasionally, irregular to the touch. C-reactive protein is elevated in most cases.

Prostate biopsies are not indicated as the (clinical) features (described above) are diagnostic. The histologic correlate of acute prostatitis is a neutrophilic infiltration of the prostate gland.

Acute prostatitis is associated with a transiently elevated PSA, i.e., the PSA is increased during an episode of acute prostatitis and then decreases again after it has resolved. PSA testing is not indicated in the context of uncomplicated acute prostatitis.

Urinary catheters should be inserted using aseptic technique and sterile equipment (including sterile gloves, drape, sponges, antiseptic and sterile solution), particularly in an acute care setting. Hands should be washed before and after catheter insertion. Overall, catheter use should be minimized in all patients, particularly those at higher risk of CAUTI and mortality (e.g. the elderly or those with impaired immunity).

Antibiotics are the first line of treatment in acute prostatitis. Antibiotics usually resolve acute prostatitis infections in a very short time, however a minimum of two to four weeks of therapy is recommended to eradicate the offending organism completely. Appropriate antibiotics should be used, based on the microbe causing the infection. Some antibiotics have very poor penetration of the prostatic capsule, others, such as ciprofloxacin, trimethoprim/sulfamethoxazole, and tetracyclines such as doxycycline penetrate prostatic tissue well. In acute prostatitis, penetration of the prostate is not as important as for category II because the intense inflammation disrupts the prostate-blood barrier. It is more important to choose a bactericidal antibiotic (kills bacteria, e.g., a fluoroquinolone antibiotic) rather than a bacteriostatic antibiotic (slows bacterial growth, e.g. tetracycline) for acute potentially life-threatening infections.

Severely ill patients may need hospitalization, while nontoxic patients can be treated at home with bed rest, analgesics, stool softeners, and hydration. Men with acute prostatitis complicated by urinary retention are best managed with a suprapubic catheter or intermittent catheterization. Lack of clinical response to antibiotics should raise the suspicion of an abscess and prompt an imaging study such as a transrectal ultrasound (TRUS).

Antibiotic therapy has to overcome the blood/prostate barrier that prevents many antibiotics from reaching levels that are higher than minimum inhibitory concentration. A blood-prostate barrier restricts cell and molecular movement across the rat ventral prostate epithelium. Treatment requires prolonged courses (4–8 weeks) of antibiotics that penetrate the prostate well. The fluoroquinolones, tetracyclines and macrolides have the best penetration. There have been contradictory findings regarding the penetrability of nitrofurantoin , quinolones (ciprofloxacin, levofloxacin), sulfas (Bactrim, Septra), doxycycline and macrolides (erythromycin, clarithromycin). This is particularly true for gram-positive infections.

In a review of multiple studies, Levofloxacin (Levaquin) was found to reach prostatic fluid concentrations 5.5 times higher than Ciprofloxacin, indicating a greater ability to penetrate the prostate.

Persistent infections may be helped in 80% of patients by the use of alpha blockers (tamsulosin (Flomax), alfuzosin), or long term low dose antibiotic therapy. Recurrent infections may be caused by inefficient urination (benign prostatic hypertrophy, neurogenic bladder), prostatic stones or a structural abnormality that acts as a reservoir for infection.

In theory, the ability of some strains of bacteria to form biofilms might be one factor amongst others to facilitate development of chronic bacterial prostatitis.

Escherichia coli extract and cranberry have a potentially preventive effect on the development of chronic bacterial prostatitis, while combining antibiotics with saw palmetto, lactobacillus sporogens and arbutin may lead to better treatment outcomes.

Bacteriophages hold promise as another potential treatment for chronic bacterial prostatatis.

The addition of prostate massage to courses of antibiotics was previously proposed as being beneficial and prostate massage may mechanically break up the biofilm and enhance the drainage of the prostate gland. However, in more recent trials, this was not shown to improve outcome compared to antibiotics alone.

Unfortunately mesna is ineffective as a treatment once hemorrhagic cystitis has developed. Although rare, once a case of radiation-induced hemorrhagic cystitis is diagnosed there is no empirically-proven treatments to heal this type of condition, which can severely degrade a patient's quality of life and might possibly lead to renal failure with risk of death.

Viral hemorrhagic cystitis in children generally spontaneously resolves within a few days.

The first step in the treatment of HC should be directed toward clot evacuation. Bladder outlet obstruction from clots can lead to urosepsis, bladder rupture, and renal failure. Clot evacuation can be performed by placing a wide-lumen bladder catheter at bedside. The bladder can be irrigated with water or sodium chloride solution. The use of water is preferable because water can help with clot lysis. Care must be taken to not overdistend the bladder and cause a perforation.. Hyperbaric oxygen (HBO2) therapy has been proven to be effective in treating radiation-induced hemorrhagic cystitis.

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".

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.

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.

Due to the atypical presentation and rarity of the infection, it takes a physician longer to diagnose than more common types of bladder infections. Diagnosis requires a personalized investigation with consideration to risk factors and symptoms (Bobba). Radiology of the abdominal or pubic region has proven to be an important tool in reaching a definitive diagnosis of conditions causing gas in the urinary tract. Computer tomography, or CT scans, are of most help due to their high sensitivity in detecting gas and air bubbles (Gheonea, Bondari). However, radiology is normally not the first tool used to diagnose. Most diagnoses are made by chance after imaging examination (Weerakkody). Sometimes, even when patients don’t show symptoms, their Emphysematous cystitis infection level can be very advanced already (De Baets, Baert). Gas in the bladder wall will often have the appearance of cobblestone or a “beaded necklace” with the use of conventional radiography (Weerakkody). Delayed diagnosis can lead to a severe infection, extension of the uterus, rupturing of the bladder, and death. Emphysematous cystitis has an overall mortality rate of 7%. However, surgery is only considered in severe cases where the disease progresses involving the ureters, kidneys, or adrenal glands. When required, surgery may be extensive. (De Baets, Baert).

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".

The symptoms of IC/BPS are often misdiagnosed as a urinary tract infection. However, IC/BPS has not been shown to be caused by a bacterial infection and antibiotics are an ineffective treatment. IC/BPS is commonly misdiagnosed as chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) in men, and endometriosis and uterine fibroids (in women).

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

A diagnosis of IC/BPS is one of exclusion, as well as a review of clinical symptoms. The AUA Guidelines recommend starting with a careful patient history, physical examination and laboratory tests to assess and document symptoms of IC, as well as other potential disorders.

The KCl test, also known as the "potassium sensitivity test", is no longer recommended. The test uses a mild potassium solution to evaluate the integrity of the bladder wall. Though the latter is not specific for IC/BPS, it has been determined to be helpful in predicting the use of compounds, such as pentosan polysulphate, which are designed to help repair the GAG layer.

For complicated cases, the use of hydrodistention with cystoscopy may be helpful. Researchers, however, determined that this visual examination of the bladder wall after stretching the bladder was not specific for IC/BPS and that the test, itself, can contribute to the development of small glomerulations (petechial hemorrhages) often found in IC/BPS. Thus, a diagnosis of IC/BPS is one of exclusion, as well as a review of clinical symptoms.

In 2006, the ESSIC society proposed more rigorous and demanding diagnostic methods with specific classification criteria so that it cannot be confused with other, similar conditions. Specifically, they require that a patient must have pain associated with the bladder, accompanied by one other urinary symptom. Thus, a patient with just frequency or urgency would be excluded from a diagnosis. Secondly, they strongly encourage the exclusion of confusable diseases through an extensive and expensive series of tests including (A) a medical history and physical exam, (B) a dipstick urinalysis, various urine cultures, and a serum PSA in men over 40, (C) flowmetry and post-void residual urine volume by ultrasound scanning and (D) cystoscopy. A diagnosis of IC/BPS would be confirmed with a hydrodistention during cystoscopy with biopsy.

They also propose a ranking system based upon the physical findings in the bladder. Patients would receive a numeric and letter based score based upon the severity of their disease as found during the hydrodistention. A score of 1–3 would relate to the severity of the disease and a rating of A–C represents biopsy findings. Thus, a patient with 1A would have very mild symptoms and disease while a patient with 3C would have the worst possible symptoms. Widely recognized scoring systems such as the O'Leary Sant symptom and problem score have emerged to evaluate the severity of IC symptoms such as pain and urinary symptoms.

Bacteria and yeast, including those naturally occurring as part of the human microbiome, can travel along urinary catheters and cause an infection in the bladder, kidneys, and other organs connected to the urinary tract.

CAUTI can lead to complications such as prostatitis, epididymitis, and orchitis in men, and cystitis, pyelonephritis, gram-negative bacteremia, endocarditis, vertebral osteomyelitis, septic arthritis, endophthalmitis, and meningitis in all patients. Complications associated with CAUTI cause discomfort to the patient, prolonged hospital stay, and increased cost and mortality. It has been estimated that more than 13,000 deaths are associated with UTIs annually. Estimated > 560,000 nosocomial UTIs annually.

The disease incidence varies widely depending on the geographical location. The most extensive epidemiological survey on this subject has been carried out by Dharmasena et al. who analysed the number of neonates who developed neonatal conjunctivitis in England from 2000 to 2011. In addition to the incidence of this sight threatening infection they also investigated the time trends of the disease. According to them the incidence of Neonatal conjunctivitis (Ophthalmia Neonatorum) in England was 257 (95% confidence interval: 245 to 269) per 100,000 in 2011.

Even when caught early, aggressive treatment is required (Bobba). Antibiotics are proven to cure Emphysematous cystitis over time and reduce the amount of gas inside the bladder wall. Prognosis is poor if antibiotics are not used to treat the patient. Additional treatment consists of urinary drainage and good control of blood glucose. The treatment of underlying comorbid diseases, such as diabetes, is extremely important because they can intensify the infection (Gheonea, Bondari). Hyperbaric oxygen is an effective treatment, and has cured some cases in as little as 48 hours. Although it is unclear as to how gas formation occurs in emphysematous cystitis, it’s dependant on whether or not the patient has contributing diseases (Mccabe). Gas formation in diabetic patients diagnosed with Emphysematous cystitis has been determined to occur due to the production of carbon dioxide as a result of the fermentation of the high concentrations of glucose. Gas formation in nondiabetic patients is most likely due the breaking down of urinary lactulose and tissue proteins. Inflammation caused by infection increases pressure and decreases circulation, which provides the perfect environment for bacteria to produce gas (Sereno).

Treatment involves avoiding the trigger if that can be determined.