Urine eosinophil cationic protein in painful bladder disease

Urine eosinophil cationic protein (U-ECP), blood eosinophils and eosinophils in bladder biopsy specimens were studied in 30 patients with painful bladder disease (15 with detrusor mastocytosis, i.e. interstitial cystitis (IC) (greater than or equal to 28 mast cells/mm2 in the detrusor muscle) and 15 patients without detrusor mastocytosis). In patients with IC the median concentration of U-ECP was 140 arbitrary u/l versus 14 arb. u/l in the remaining patients (P less than 0.001). The mean peripheral leukocyte count was significantly lower in the IC group (P less than 0.05). Tissue infiltration with eosinophils was found in 43% of the bladder biopsies from patients with IC compared with 4% of the biopsies in the remaining patients (P less than 0.05). A negative correlation between peripheral eosinophils and U-ECP was found in the patients with IC (r = 0.52, P less than 0.05). These results suggest that eosinophils are attracted to the inflammatory site in the bladder wall where ECP is released. Eosinophils thus seem to participate actively in the inflammatory process. U-ECP seems to provide valuable diagnostic information when diagnosing IC in patients with painful bladder disease. It is suggested that ECP might be involved in the process of tissue destruction in IC.