Risk factors include catheter use and chronic urinary tract infections, being female, diabetes mellitus, neurogenic bladder, and being in an immunocompromised state (Weerakkody). In 50% of cases, patients are elderly and diabetic. Obstruction of the urinary tract as well as urinary stasis, often brought on by paralysis of the urinary tract, are also major risk factors in addition to diabetes (De Baets, Baert). Transplant recipients have also been found to be at risk (Weerakkody). Introduction of infection from external means was discovered in one case study where a male with no history of diabetes or abnormalities to his immune system had recently undergone a transrectal ultrasound needle-guided prostate biopsy contracted a severe case of sepsis, which led to a case of Emphysematous cystitis. The patient went on to develop disseminated intravascular coagulopathy and acute respiratory distress syndrome. After a stay in Intensive Care undergoing broad-spectrum antibiotic therapy, the patient was eventually discharged in stable condition (Hashimoto, Takeshi). Patients diagnosed with Emphysematous Cystitis are also commonly diagnosed with urinary tract infections and sepsis (Mccabe). Cases of Emphysematous Cystitis in a clinical study have shown to progress quickly and are life threatening and sometimes fatal due to inflammation caused by gas forming organisms (Mokabberi).

Signs and symptoms of emphysematous cystitis include air in the bladder wall, altered mental status, severe abdominal pain, weakness, dark urine, dysuria, fever, lethargy, vomiting, as well as white blood cells and bacteria in the urine (Mccabe). Where some patients may be asymptomatic, others may present with septic shock (De Baets, Baert). Symptoms can vary greatly from patient to patient, which makes the disease difficult to diagnose. In some cases of emphysematous cystitis, patients do not even claim to have any urinary symptoms (Mokabberi). Urinary symptoms can include blood in the urine, increased urinary frequency, urgency, occasional incontinence, difficulty voiding, and burning sensation. Emphysematous cystitis is often indicated in patients who have air in the urine (Bobba). In some cases, emphysematous cystitis can cause thickening of the bladder wall (Weerakkody). Clinical subcutaneous emphysema is a rare complication of emphysematous cystitis that has a poor prognosis (Ahmed-Ramadan, Blake).

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.

In young sexually active women, sexual activity is the cause of 75–90% of bladder infections, with the risk of infection related to the frequency of sex. The term "honeymoon cystitis" has been applied to this phenomenon of frequent UTIs during early marriage. In post-menopausal women, sexual activity does not affect the risk of developing a UTI. Spermicide use, independent of sexual frequency, increases the risk of UTIs. Diaphragm use is also associated. Condom use without spermicide or use of birth control pills does not increase the risk of uncomplicated urinary tract infection.

Women are more prone to UTIs than men because, in females, the urethra is much shorter and closer to the anus. As a woman's estrogen levels decrease with menopause, her risk of urinary tract infections increases due to the loss of protective vaginal flora. Additionally, vaginal atrophy that can sometimes occur after menopause is associated with recurrent urinary tract infections.

Chronic prostatitis in the forms of chronic prostatitis/chronic pelvic pain syndrome and chronic bacterial prostatitis (not acute bacterial prostatitis or asymptomatic inflammatory prostatitis) may cause recurrent urinary tract infections in males. Risk of infections increases as males age. While bacteria is commonly present in the urine of older males this does not appear to affect the risk of urinary tract infections.

Urinary catheterization increases the risk for urinary tract infections. The risk of bacteriuria (bacteria in the urine) is between three and six percent per day and prophylactic antibiotics are not effective in decreasing symptomatic infections. The risk of an associated infection can be decreased by catheterizing only when necessary, using aseptic technique for insertion, and maintaining unobstructed closed drainage of the catheter.

Male scuba divers utilizing condom catheters and female divers utilizing external catching devices for their dry suits are also susceptible to urinary tract infections.

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).

There are roughly 12–13 cases annually per 10,000 population in women receiving outpatient treatment and 3–4 cases requiring admission. In men, 2–3 cases per 10,000 are treated as outpatients and 1– cases/10,000 require admission. Young women are most often affected, probably reflecting sexual activity in that age group. Infants and the elderly are also at increased risk, reflecting anatomical changes and hormonal status. Xanthogranulomatous pyelonephritis is most common in middle-aged women. It can present somewhat differently in children, in whom it may be mistaken for Wilms' tumor.

IC/BPS has a profound impact on quality of life. A 2007 Finnish epidemiologic study showed that two-thirds of women at moderate to high risk of having interstitial cystitis reported impairment in their quality of life and 35% of IC patients reported an impact on their sexual life. A 2012 survey showed that among a group of adult women with symptoms of interstitial cystitis, 11% reported suicidal thoughts in the past two weeks. Other research has shown that the impact of IC/BPS on quality of life is severe and may be comparable to the quality of life experienced in end-stage kidney disease or rheumatoid arthritis.

International recognition of interstitial cystitis has grown and international urology conferences to address the heterogeneity in diagnostic criteria have recently been held. IC/PBS is now recognized with an official disability code in the United States of America.

Causes of hemorrhagic cystitis include chemotherapy (e.g. cyclophosphamide, Ifosfamide), radiation, or infection. Ifosfamide is the most common cause of hemorrhagic cystitis. Radiation-induced hemorrhagic cystitis develops in similar or smaller patient numbers when compared to cyclophosphamide-induced cases.

Adenovirus (particularly serotypes 11 and 21 of subgroup B) is the most common cause of acute viral hemorrhagic cystitis in children, though it can result from BK virus as well. A chemical hemorrhagic cystitis can develop when vaginal products are inadvertently placed in the urethra. Gentian violet douching to treat candidiasis has resulted in hemorrhagic cystitis when the drug was misplaced in the urethra, but this hemorrhagic cystitis resolved spontaneously with cessation of treatment. Accidental urethral placement of contraceptive suppositories has also caused hemorrhagic cystitis in several patients. The bladder irritation was thought to be caused by the spermicidal detergent nonoxynol-9. In the acute setting, the bladder can be copiously irrigated with alkalinized normal saline to minimize bladder irritation.

Although hemorrhagic cystitis post-transplantation/bone marrow transplantation is not technically infectious, a short discussion is in order for completeness. Patients undergoing therapy to suppress the immune system are at risk for hemorrhagic cystitis due to either the direct effects of chemotherapy or activation of dormant viruses in the kidney, ureter, or bladder.

Treatment involves avoiding the trigger if that can be determined.

A common cause of pneumaturia is colovesical fistula (communication between the colon and bladder). These may occur as a complication of diverticular disease.

Other key differentials:

- Crohn's disease

- Carcinoma of the colon or bladder

- A gas-producing UTI (emphysematous cystitis: rare).

Male scuba divers utilizing condom catheters or female divers using a She-p external catching device for their dry suits are also susceptible to pneumaturia.

Most cases of "community-acquired" pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are "E. coli" (70–80%) and "Enterococcus faecalis". Hospital-acquired infections may be due to coliform bacteria and enterococci, as well as other organisms uncommon in the community (e.g., "Pseudomonas aeruginosa" and various species of "Klebsiella"). Most cases of pyelonephritis start off as lower urinary tract infections, mainly cystitis and prostatitis. "E. coli" can invade the superficial umbrella cells of the bladder to form intracellular bacterial communities (IBCs), which can mature into biofilms. These biofilm-producing "E. coli" are resistant to antibiotic therapy and immune system responses, and present a possible explanation for recurrent urinary tract infections, including pyelonephritis. Risk is increased in the following situations:

- Mechanical: any structural abnormalities in the urinary tract, vesicoureteral reflux (urine from the bladder flowing back into the ureter), kidney stones, urinary tract catheterization, ureteral stents or drainage procedures (e.g., nephrostomy), pregnancy, neurogenic bladder (e.g., due to spinal cord damage, spina bifida or multiple sclerosis) and prostate disease (e.g., benign prostatic hyperplasia) in men

- Constitutional: diabetes mellitus, immunocompromised states

- Behavioral: change in sexual partner within the last year, spermicide use

- Positive family history (close family members with frequent urinary tract infections)

IC/BPS affects men and women of all cultures, socioeconomic backgrounds, and ages. Although the disease was previously believed to be a condition of menopausal women, growing numbers of men and women are being diagnosed in their twenties and younger. IC/BPS is not a rare condition. Early research suggested that IC/BPS prevalence ranged from 1 in 100,000 to 5.1 in 1,000 of the general population. In recent years, the scientific community has achieved a much deeper understanding of the epidemiology of interstitial cystitis. Recent studies have revealed that between 2.7 and 6.53 million women in the USA have symptoms of IC and up to 12% of women may have early symptoms of IC/BPS. Further study has estimated that the condition is far more prevalent in men than previously thought ranging from 1.8 to 4.2 million men having symptoms of interstitial cystitis.

The condition is officially recognized as a disability in the United States.

Bladder tamponade is obstruction of the bladder outlet due to heavy blood clot formation within it. It generally requires surgery. Such heavy bleeding is usually due to bladder cancer.

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.

Asymptomatic bacteriuria is bacteriuria without accompanying symptoms of a urinary tract infection. It is more common in women, in the elderly, in residents of long-term care facilities, and in people with diabetes, bladder catheters and spinal cord injuries. People with a long-term Foley catheter uniformly show bacteriuria. Chronic asymptomatic bacteriuria without urinary tract infection symptoms occurs in as many as 50% of the population in long-term care.

In pregnant women bacteriuria is associated with low birth weight, preterm delivery, and infection of the newborn. Bacteriuria in pregnancy also increase the risk of preeclampsia.

Eosinophilic cystitis is a rare condition where eosinophiles are present in the bladder wall. Signs and symptoms are similar to a bladder infection. Its cause is not entirely clear; however, may be linked to food allergies, infections, and medications among others.

Cystitis is a urinary bladder inflammation that results from any one of a number of distinct syndromes. It is most commonly caused by a bacterial infection in which case it is referred to as a urinary tract infection.

Diagnosis is made by patient history of passing air or a sputtering urine stream. CT scans may show air in the urinary bladder or bladder walls.

Symptomatic bacteriuria is bacteriuria with the accompanying symptoms of a urinary tract infection (such as frequent urination, painful urination, fever, back pain). Symptomatic bacteriuria can be indicative of a urinary tract infection like pyelonephritis or cystitis. The most common type of bacteriuria associated with urinary tract infections is "Escherichia coli" which is a gram-negative rod-shaped bacteria.

The causes of diseases of the body are common to the urinary tract. Structural and or traumatic change can lead to hemorrhage, functional blockage or inflammation. Colonisation by bacteria, protozoa or fungi can cause infection. Uncontrolled cell growth can cause neoplasia.

For example:

- Urinary tract infections (UTIs), interstitial cystitis

- incontinence (involuntary loss of urine), benign prostatic hyperplasia (where the prostate overgrows), prostatitis (inflammation of the prostate).

- Urinary retention, which is a common complication of benign prostatic hyperplasia (BPH), though it can also be caused by other types of urinary tract obstruction, nerve dysfunction, tethered spinal cord syndrome, constipation, infection and certain medications.

- Transitional cell carcinoma (bladder cancer), renal cell carcinoma (kidney cancer), and prostate cancer are examples of neoplasms affecting the urinary system.

- Urinary tract obstruction

The term "uropathy" refers to a disease of the urinary tract, while "nephropathy" refers to a disease of the kidney.

The drug Elmiron helps, for some patients, to prevent the formation of Hunner's Ulcers by coating the bladder wall, thus making it harder for the acid in urine to irritate the bladder wall lining, which can lead to ulceration. (not cited)

In addition to traditional IC therapies, diet modification remains a core self care strategy as foods that are irritating to the bladder dramatically worsen the symptoms that patients may experience. Foods high in acid and/or caffeine (such as all coffees, regular teas, green teas, sodas, diet sodas, artificial sweeteners and most fruit juices) should be avoided. The daily goal of patients should be to soothe rather than irritate the bladder wall.

Glomerulation refers to bladder hemorrhages which are thought to be associated with some types of interstitial cystitis (IC).

The presence of glomerulations, also known as petechial hemorrhages, in the bladder suggests that the bladder wall has been damaged, irritated and/or inflamed. In fact, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Diagnostic Criteria for IC, developed in 1987, required the presence of glomerulations or Hunner's Ulcers to make a firm diagnosis of IC and is still used, today, to determine patient eligibility for some clinical trials. Research conducted by Waxman, however, determined that the hydrodistention procedure itself may have created these tiny broken blood vessels. Thus, a diagnosis of IC is now based upon other, less invasive methods, such as the PUF questionnaire.

Urologic disease can involve congenital or acquired dysfunction of the urinary system.

Kidney diseases are normally investigated and treated by nephrologists, while the specialty of urology deals with problems in the other organs. Gynecologists may deal with problems of incontinence in women.

Diseases of other bodily systems also have a direct effect on urogenital function. For instance, it has been shown that protein released by the kidneys in diabetes mellitus sensitises the kidney to the damaging effects of hypertension.

Diabetes also can have a direct effect on urination due to peripheral neuropathies which occur in some individuals with poorly controlled diabetics.