Urinary leakage of tubular enzymes after shock wave lithotripsy.

OBJECTIVES

Urinary loss of tubular marker enzymes following shock wave lithotripsy (SWL) suggests corresponding morphological changes in the kidney. To date, the morphological correlate of enzymuria and its dependence on the energy applied remains unclear.

METHODS

In an animal study, the acute morphological changes occurring in the tubulus cells as the basis of enzymuria were investigated. It was evaluated whether SWL-induced enzymuria correlates with the extent of renal damage.

RESULTS

Acute morphological changes in the tubulus cells were demonstrated beneath isolated tubulus necrosis. The mechanically induced lesions of the cell organelles included fragmentation of the lysosomes and severe alterations of the cell membrane. The tubulus damage can be quantified. With the help of histochemical N-acetyl-beta-D-glucosaminidase (NAG) staining and electron microscopic observations, a significant correlation was found between the shock wave parameters number of impulses and intensity and the tubular damage. The intensity of NAG enzymuria reflected the severity of the tubular damage.

CONCLUSIONS

In this animal model, NAG proved to be a suitable marker enzyme for estimation of the degree of SWL-induced tubular damage.