Surface topography of the female bladder trigone

The morphology of normal human bladder urothelium

A comprehensive study of human bladder urothelium was undertaken to define the normal histological and fine structural features of this tissue. Urothelial biopsies from consenting male and female patients undergoing diagnostic or review cystoscopies were analysed. In 31 patients there was an apparently normal urothelium lining the bladder, and in 3 patients the trigone appeared normal. Normal urothelium was not observed to contain lymphocytes, lymphoid follicles, mast cells, Brunn's nests or cysts. No mitoses were seen despite examining about 50,000 urothelial cells. Trigonal and bladder urothelium normally consisted of 3 and 3-6 cell layers, respectively, but they shared the same basic architecture of basal, intermediate and superficial (or surface) cell types. The urothelium possessed a regular, polarised architecture of increasing morphological complexity and differentiation from base to surface. Occasional, slender, cytoplasmic projections were observed to reach the basal lamina from the intermediate cell layer, but not from the surface cell layer. Human urothelium should therefore be considered a stratified, not a pseudostratified, epithelium. The nuclear shape in cross-section was indented in the basal layer, and rounded in the superficial layer. Correspondingly, chromatin configurations of urothelial nuclei were evenly and finely granular in the superficial layer and condensed in the basal layer, suggesting a greater degree of transcriptional activity in the former. Intermediate cell nuclei assumed intermediate degrees of shape and chromatin configuration. Prominent nucleoli were found in the nuclei of all cell layers. Both basal and intermediate cell nuclei and superficial cell nuclei contained characteristic nuclear bodies. Urothelial cells of all layers were connected by interdigitations of cytoplasmic processes and by desmosomes. Clusters of mitochondria were seen throughout the urothelium. Elaborate Golgi membranes and rough endoplasmic reticulum, although rare in the basal layer, were observed in the remainder of the urothelium. Large, prominent lysosomes were identified with the electron microscope and histochemically in the surface layer. The superficial aspect of the urothelium was lined, at least in some regions, by an asymmetric luminal membrane. Tight junctions linked adjacent urothelial surface cells. Such junctions were not observed anywhere else in the urothelium. Fine cytoplasmic filaments, probably of the intermediate type, were most conspicuous in the surface layer. Overall, normal human bladder urothelium is arranged in increasing complexity from base to surface.

Low-temperature and conventional scanning electron microscopy of human urothelial neoplasms

The appearance of neoplastic human urothelium viewed by low-temperature scanning electron microscopy (LTSEM) and conventional scanning electron microscopy (CSEM) was compared. Fixed, dehydrated neoplastic cells viewed by CSEM had well-defined, often raised cell junctions; no intercellular gaps; and varying degrees of pleomorphic surface microvilli. The frozen hydrated material viewed by LTSEM, however, was quite different. The cells had a flat or dimpled surface, but no microvilli. There were labyrinthine lateral processes which interdigitated with those of adjacent cells and outlined large intercellular gaps. The process of fixation and dehydration will inevitably distort cell contours and on theoretical grounds, the images of frozen hydrated material should more closely resemble the in vivo appearance.

Scanning electron microscopy of the upper urinary tract in transitional cell carcinoma of the renal pelvis

Three nephrectomy specimens with transitional cell carcinoma (TCC) of the renal pelvis were thoroughly examined by both light and scanning electron microscopy. The tumours as well as the urothelium of the upper urinary tract were studied. In all three cases, extensive areas of the urothelium, even in places remote from the tumours, were found by scanning electron microscopy (SEM) to be covered by pleomorphic microvilli. This suggests that there is a widespread failure of differentiation of the urothelium to a much greater extent than can be appreciated by conventional light microscopy.

Scanning electron microscopic exfoliative urinary cytology in patients with malignant and nonmalignant diseases of lower urinary tract

The possible clinical usefulness of scanning electron microscopic observation of urinary cytologic specimens has been suggested for selected patient populations. To begin to determine the specificity and sensitivity of the procedure, cytologic specimens (48 catheterized urine and 49 bladder washings) from 85 patients with bladder tumor or nonmalignant urologic diseases were observed by scanning electron microscopy (SEM) and compared with observations by light microscopy. This study provides evidence that SEM exfoliative cytology in catheterized urine and/or bladder washings has considerable specificity for low-grade, low-stage bladder tumors, but may not be sufficiently sensitive for use in routine urologic practice. However, this procedure may be of use in following patients with previously resected low-grade, low-stage bladder tumors for the early detection of recurrences.

Low temperature and conventional scanning electron microscopy of human urothelium

The appearance of fixed dehydrated non-neoplastic human urothelium viewed by conventional scanning electron microscopy (CSEM) is different from that of frozen hydrated human urothelium viewed by low temperature scanning electron microscopy (LTSEM). In the fixed dehydrated material the surface is formed by well defined, polygonal, domed superficial urothelial cells which have prominent surface microridges. In places intermediate urothelial cells are visible and they have surface microvilli. In the frozen hydrated material viewed by LTSEM most of the surface is smooth. This is formed in part by a glutaraldehyde soluble extracellular secretion which may be a mucin barrier to bacteria. We believe that the rest of the smooth surface is formed by superficial urothelial cells which are not well defined and which lack microridges. There are islands of rounded cells lacking microvilli which are probably intermediate urothelial cells as they correspond in appearance with the intermediate urothelial cells seen in freeze fractured material. It seems likely that fixation and dehydration will cause some change in surface configuration and in theory the frozen hydrated material should more closely resemble the natural state. We believe that LTSEM will be of value in investigating normal and diseased urothelium.

The incidence and significance of vaginal metaplasia of the bladder trigone in adult women

One hundred and six bladders were removed at autopsy from adult women dying of diseases unrelated to the urinary tract. A fixative solution had been introduced into the bladder as soon as possible after death. The naked-eye appearances were recorded before and after application of Lugol's iodine solution and the trigones then submitted to histological examination. Vaginal metaplasia of the trigone was present in the majority (72%) of bladders, a similar incidence being found in both pre-menopausal and post-menopausal age groups. Histological evidence of chronic inflammation was found significantly more frequently in bladders showing vaginal metaplasia and it is suggested that vaginal metaplasia is not a consequence of chronic inflammation but that its surface characteristics may predispose to chronic infection. Its purported hormonal aetiology does not explain all observed features. Prominent venous channels within the tunica propria around the urethral orifice were a constant feature in all bladders studied. Two of the 76 bladders showing vaginal metaplasia also displayed atypical hyperplasia of this squamous epithelium, a previously unrecorded observation. The possible implications of such atypical hyperplasia are briefly discussed.