Morphometric analysis of muscle cell changes in the short‐term partially obstructed rabbit detrusor

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Abstract
It has been shown previously that both degenerative and regenerative muscle cell changes occur in the partially obstructed rabbit detrusor and are largely reversed after relief of the obstruction [Elbadawi et al., 1989]. In the present study, we quantitated these changes in the same animal model to define their chronologic evolution. Specimens for electron microscopic study were obtained from the bladder body detrusor in three normal rabbits, fifteen rabbits with 1–14 days of partial bladder outlet obstruction, and seven rabbits relieved of a 7‐day obstruction for 14 or 28 days. Sections from each specimen were analyzed quantitatively for the prevalence of normal, degenerative, and regenerative muscle cell profiles by determining the percentage of photographic prints showing only normal muscle cells and those depicting muscle cell change. Prints of 684 semirandom and 95 truly random photographs were so analyzed. Absolute counts of the various types of muscle cell profiles were also made in the former group of prints for comparison. In addition, 174 prints were analyzed for the presence of hypertrophic cell profiles. All data were analyzed statistically by the appropriate methods. Our observations led to classification of the material studied into three categories: (a) control, which includes both the normal and 1‐day obstructed groups; (b) obstructed, including the 3–7 day obstructed groups in which both degenerative and regenerative changes were maximal; and (c) recovered, including the 14‐day obstructed and both 14‐ and 28‐day deobstructed groups in which muscle cell changes were markedly—though incompletely—reversed. Our findings form a structural basis for the changes in contractility and biochemical profile of the partially obstructed detrusor that have been described previously in the same model [Malkowicz et al., 1986].