CHESS classification of bladder-outflow obstruction. A consequence in the discussion of current concepts.

The present discussion on the natural history, growth rate pathophysiology, morbidity, and possible treatment of benign prostatic hyperplasia (BPH) reinforces the need to objectify mechanical BPH-induced obstruction with pressure-flow study. Different methods for the quantification of BPH-induced obstruction exist and the grade of simplification depends on their working mechanism. To review the limitations of the current concepts, 118 BPH patients were selected for computerized pressure-flow data analysis according to quadratic passive urethral resistance relation (PURR) function. The CHESS classification differs from all other concepts due to its two-dimensional character and was developed as a result of the following way of thinking: (1) the whole individual pressure-flow plot is the most accurate basis for further analysis; (2) PURR as the true low-pressure flank of the individual plot is the most favorable definition for mechanical obstruction; (3) PURR quantification requires at least two parameters, footpoint and curvature/slope, with regard to the documented missing significant correlation of both; and (4) a two-parameter-based classification is two-dimensional (CHESS classification).