[The pathogenesis of interstitial cystitis--many hypotheses, but etiology remains uncertain]

Pathogenic aspects of interstitial cystitis (IC) are reviewed on the basis of the current literature applying the criteria of evidence-based medicine (EBM). Three hundred forty-six peer-reviewed publications of the past 30 years were retrieved via MEDLINE employing the key words "interstitial cystitis and pathogenesis or etiology" and classified according to EBM criteria and subject categories. The papers were then reviewed and summarized and are discussed considering the theory of acute and chronic inflammatory responses. In the literature, nearly all steps of the normal inflammatory response are considered pathogenically important in development of the IC syndrome. Applying EBM criteria, all studies fail to meet the criteria for sound statistical evaluation and to demonstrate reproducibly a reliable pathogenic factor. Most publications report only small numbers of patients. Control groups are frequently lacking or too small. Clinically useful criteria for the diagnosis of IC are not properly defined. There is no commonly accepted animal model in which IC occurs naturally or can be artificially induced. Of the 683 IC papers studied, 346 (50.7%) deal with pathogenic or etiological aspects of IC. The inflationary use of the terms pathogenesis or etiology in one out of every two papers calls for more prudent application of terminology in the future. As yet, none of the published pathogenic factors was found to represent the main trigger of the IC syndrome. Some of them seem to be part of a vicious cycle of the inflammatory reaction present. Detailed knowledge of the process of chronic inflammation can lead to treatments that may interrupt an inflammatory response. This might contribute to solving the pathogenic issue of IC and could be helpful in designing further investigations. Advances in understanding the causes of IC require objective criteria to subclassify the heterogenous patient cohort presently referred to as IC syndrome. Such subclassifications are a predisposition for pathogenic investigations and determining future treatment strategies.