Effect of vesical overdistention on bladder mucin.

Histochemical staining of bladder tissue demonstrates a discrete layer of mucopolysaccharide (mu&) on the sur$ace of human and rabbit bladders. Studies have shown that an intact mucin layer may be important in helping the bladder to resist bacterial infections. This report correlates vesical over-distention with destruction of the muck layer in the rabbit bladder. These findings suggest that vesical over-distention may predispose to urinary tract infection because of bladder mucin disruption. Most authorities agree that urinary infections occur primarily from a retrograde contamination into the bladder.lF4 When Escherichia coli are inoculated into “healthy” bladders, no urinary infection occurs.’ Similarly, patients on intermittent catheterization (not a sterile technique) frequently maintain uninfected urine without antibiotics.‘j The reasons one bladder resists infection while another succumbs are not known. To prevent urinary infections, Lapides has long advocated frequent voiding feeling that increased intravesical pressure disrupts the tissue integrity or blood supply to the bladder.“8 Investigations have shown that voiding is an important physical mechanism by which the bladder resists infection.“” Parsons and associates12-14 have shown that bladder mucin has a significant role in the primary antibacterial defense of the bladder. Their data have shown the destruction of bladder mucin (by acid) to be associated with increased microbial attachment to the bladder. i2,13 If the mucin layer of the bladder could be disrupted by vesical overdistention, we could more clearly correlate vesical overdistention with uriPresented at the Annual Meeting, American Urological Association, Inc., Boston, Massachusetts, May, 1981. nary tract infections. The data obtained from this experiment indicate that vesical overdistention disrupts or destroys the mucin layer of the rabbit bladder. On the basis of histochemical staining of these bladders, we were able to blindly predict, with 94-per cent accuracy, which bladders were normal and which had been overdistended. Material and Methods Laboratory treatment Seventeen female New Zealand white rabbits weighing 2 to 4 Kg. were obtained for study. One of us (E.M.H.), in a random manner, chose some of the animals to be controls and some to be experimental. The experimental animals had their bladder necks ligated through a ventral midline incision. Twenty-four hours later they were sacrificed, as were the control animals. All rabbit bladders were excised, irrigated gently in normal saline, and placed in Bouin solution. The bladders were then sectioned and stained with colloidal iron. Colloidal iron stain is specific for mucin. Microscopic findings Two of us (D.L.P. and P.W.G.) then examined the stained bladder slides. On the basis of 380 UROLOGY / OCTOBER 1981 / VOLUME XVIII, NUMBER 4 staining layer overlying transitional epithelium; (C) di,srupted mucin-staining layer; and (D I pr~~sence and absence of mucin-staining layer in “mixed picture,” about which no prediction was made. the histochemical staining of the mucin. predictions were made as to whether tissue sections were fr-om a control or an experimental bladder. On examination of I7 bladders, 3 were found to have an intact mucin layer. These were characterized by clear evidence of a mudn-staining layer overlying the transitional epitheliun-r (Fig. 1A). These tissue sections were predicted to be from control bladders. Thirteen bladders were found to have an absent or significantly disrupted inrlc,in-staining la).er (Fig. lB, 0. These tissue sections were predicted to be from experimental bladders. One slide presented a “mixed picture” characterized by both the presence and absence of a mucin-staining layer (Fig. 1D). No prediction was made regarding this bladder.