Fractal Dimension as a Novel Clinical Parameter in Evaluation of the Urodynamic Curves

Summary

The objective of this pilot study was to find out whether urodynamic curves possess fractal structure, and how this structure changes along with changes of detrusor function in patients with longlasting outflow obstruction? We analyzed 25 multichannel urodynamic curves representing normal function of urinary bladder (n=10 curves) and dysfunction of detrusor muscle (n=15 curves). The curves were analyzed by Size-Frequency algorithm, R/S algorithm or Power-Spectral algorithm. All curves analyzed possess fractal structure. This structure is defined by Size-Frequency dimension, fractal dimension, and Hurst coefficient. The latter one was found to be much lower than 0.5 for all urodynamic curves representing normal filling and voiding function of the urinary bladder. The long-lasting outflow obstruction caused increment of the Hurst coefficient close up to 0.8. Long-lasting outflow obstruction changes the regular contractions of detrusor muscle into the deterministic chaotic contractions. We hypothesize that the Hurst coefficient equal to 0.5 is a limit value which allows to distinguish between cases of benign prostatic hyperplasia which can be treated pharmacologically and those which should be treated surgically.