Recurrent cystitis is defined as an inflammation of the urinary bladder, although it most often refers to relapses or reinfection caused by bacteria. There may be factors that enhance the susceptibility to recurrent infections such as congenital abnormalities (structural changes that have existed from birth), metabolic disorders or systemic immunosuppression (a decrease in efficiency of the body's immune system); however, no underlying disorder need exist. It is also important to note that administering an incorrect antibiotic, or antibiotics at too low a dose or too short a course may not fully eradicate an infection, contributing to recurrent or persistent infections.

The clinical signs associated with recurrent cystitis may be mild, or even unnoticed, although some individuals may have severe, unrelenting signs of discomfort often associated with urinating. Depending on the specific case, certain diagnostics and therapeutics would be recommended and tailored to that individual.

Several diseases/disorders can present similarly to recurrent cystitis. These include:

Urolithiasis (stones) anywhere throughout the urinary tract may be associated with cystitis. In addition to the similarity in their presentation, stones are commonly the underlying cause of recurrent cystitis.

Pyelonephritis (kidney infection) may cause or be the result of patients with recurrent cystitis.

Chronic renal (kidney) failure may be associated with, cause or be the result of recurrent cystitis.

Metabolic illnesses, such as hyperadrenocorticism (Cushing's disease) or diabetes mellitus

Administration of medication (chemotherapy, corticosteroids), can suppress the immune system, creating an environment that favors recurrent cystitis. Additionally, cyclophosphamide, an agent used in many chemotherapeutic protocols, can cause a sterile (non-infectious) cystitis (inflammation of the bladder).

In addition to the above disorders, severe clotting (bleeding) disorders can often show signs similar to recurrent cystitis, most often with hematuria. Any bleeding disorder needs to be differentiated from recurrent cystitis. Some of the more common clotting disorders include:

Thrombocytopenia (a decrease in the number of platelets) can cause hematuria. Platelets are essential for normal clotting, and a decrease in their number is often associated with spontaneous bleeding. The urinary tract is one of many places thrombocytopenia may manifest itself.

The ingestion of rat poison (Warfarin toxicity) can cause hematuria by interfering with the normal clotting mechanism. The urinary tract is one of many places that can be associated with spontaneous bleeding.

Liver disease, including infections, inflammation and cancer, can interfere with the normal clotting mechanism, as a normal functioning liver is necessary to produce ample clotting factors.

Disseminated intravascular coagulation (DIC) can be associated with hematuria. This is an overwhelming syndrome in which spontaneous bleeding is common.

Trauma to the abdomen or external genitalia can cause bleeding in the urine. This may be due to rough housing with household pets, chewing or licking at the vulva or penus, or caused by repeat catheterizations for any reason.

Neoplasia (cancer) involving the lower urinary tract may need to be differentiated from cystitis in these patients, as slow and painful urination (stranguria), blood in the urine (hematuria) and painful urination (dysuria) are commonly seen.