PATHOLOGY AND URODYNAMICS OF MEGALOURETER

Abstract

Congenitally dilated ureters (32 cases) were urodynamically and histopathologically investigated. In the majority of instances the pathogenetic significance of the distal narrowed segment was reconfirmed. Difference in the development of the ureteral sheaths was also incriminated as a contributing factor in the genesis of these ureteral dilation—the more than well developed deep sheath by inherently constricting the terminal ureteral end in the non-refluxing (primary) megaloureter, and their poor development by allowing free reflux in the refluxing megaloureter. 5 cases (4 infants, 1 adult) of non-refluxing megaloureter and 1 infantile case of refluxing megaloureter were also described as unusual ones by demonstrating functional and morphological evidence of severe dysplasia of the dilated ureteral wall.
Clinical materials in the last 14 years and their data are illustrated in Table 1. At the time of surgery prospective study was started from 1974 to elucidate functional features of the obstruction by pressure flow study (PFS) with empty and full bladder, respectively. The ureteral end was then freed from the bladder wall by meticulously dissecting along the plane of Waldeyer's space. Operative specimen from the distal ureteral end inclusive of the ureteral orifice and dilated portion were submitted to detailed histological study by both light and electron microscopic methods. The followings are the results of this prospective study of 34 ureters in 32 cases.
Undisputed obstruction, namely progressive elevation of pressure in PFS with or without bladder distension, was documented only in 3 infantile cases of non-refluxing megaloureter. All the remainder, regardless of arbitary classification of refluxing versus non-refluxing megaloureter, failed to show obstructive effect when the bladder was continuously drained. When the bladder was not drained, however, they proved to be truly obstructed ureters as demonstrated by cinefluoroscopy and PFS. After the ureter was disconnected from the bladder, its ureteral end was no longer obstructive even when the bladder was filled to its capacity. Reuxing megaloureter in association with paraureteral diverticulum appeared to belong to reflux with obstruction as seen in delayed emptying of the refluxed urine.
Histologically condition of extrinsic ureteral muscle, namely the ureteral sheaths, differs in the refluxing and non-refluxing mugaloureter. Its development was inconspicuous in the former, while it was more than well developed in the majority of the latter, this being more aptly so in their deep sheath. Regarding the intrinsic ureteral muscle, however, they generally shared common microscopic feature by demonstrating either total disarrangement, predominantly circular orientation, normal or hypoplastic development of the narrowed segment with or without increase in the interstitial connective tissues. Meanwhile in the dilated portion muscular integrity and interstitial feature were relatively normal except for some evidence of hypertrophy and hyperplasia and/or fibrosis. Ultrastructural apparatuses such as thick and thin filaments in the individual muscle cell, nerve fibers and nexuses were uniformly observed to be normal throughout the whole length of the ureter. An exception to these general feature of ureteral musculature was noted exclusively in the 5 infantile and 1 adult cases including 3 cases discussed previously as cases of undisputed obstruction. The dilated portion was characterized by sparse distribution of muscle cells with an increase in the interstitial connective tissue. Individual muscles, scattered among large amount of collagenous fibers, were much smaller than those of the narrowed segment and lacked nearly all thick myofilaments. Nerves were seen as well as nexuses, the latter being attenuated however. These contrasted well to the histopathology of the narrowed segment which was characterized by relative normalcy in regard to musculointerstitial arra