Eosinophilic cystitis (EC) is a rare inflammatory bladder condition caused by the build up of eosinophils in the bladder. The exact cause of this condition is not known. However, EC has been found in those with allergies and asthma, and in those with a history of bladder trauma or infection, open bladder surgery, or surgery for a bladder tumor. EC has also been found in those who take certain medications.

The cause of eosinophilic cystitis remains unclear, although it has been associated with allergies, reactions to certain medications (antibiotics, chemotherapy), bladder trauma, bladder tumors, and parasitic infections.

Common symptoms include urinary frequency, painful urination, blood in the urine, and abdominal/pelvic pain. Other less common symptoms include excessive urination during the night and urinary retention. Many of the symptoms commonly seen in EC mimic symptoms seen in other conditions. Rare features include gastrointestinal symptoms because of eosinophilic gastroenteritis, skin rash, and the passage of air in the urine (pneumaturia). EC has been observed in 2% of patients with superficial transitional cell carcinoma (bladder cancer).

In those with bladder lesions, surgery has been successful. Few patients with progressive EC not responding to medical therapy or surgery may be considered for more radical procedures, such as partial/total cystectomy (surgical removal of all or part of the bladder).

Most patients can be cured, but recurrence is a frequent finding. One study examined 118 patients who were treated for eosinophilic cystitis. Of these, 91 patients (77%) were cured, which was defined as the complete absence of symptoms in the short-term and long-term. However, the recurrence of symptoms has been noted in some affected individuals. Thus, those with EC require long-term follow-up with relevant blood tests, urine examination, appropriate imaging, and cystoscopy.