British Journalof Urology (1992), 70, 370-372 1992 British Journal of Urology

Increase in Presumptive Sensory Nerves of the Urinary Bladder in Idiopathic Detrusor Instability KATE H. MOORE, SALLY A. GILPIN, J. S. DIXON, D. H. RICHMOND and J. R. SUTHERST G ynaecological Urodynamic Unit, University of Liverpool; Department of Cell and Structural Biology, University of Manchester

Summary-The density of subepithelial, presumptive sensory nerves in the bladder wall was assessed in 21 women with idiopathic detrusor instability and compared with the density of these nerves in 21 asymptomatic women, using a point-counting technique on sections of bladder biopsies stained for acetylcholinesterase activity. The mean value ( S.E.) for the amount of s u c h nerves in patients with detrusor instability (91 f 13/mm2) was significantly greater than that from the control group (61 f7/mm2). This suggests that a relative abundance of subepithelial sensory nerves may serve to increase the appreciation of bladder filling, giving rise to the frequency and urgency of micturition which are characteristic of patients with detrusor instability.

Despite the fact that idiopathic detrusor instability with affects U P to one-third Of incontinence (Abrams et al.5 198319 the aetiology of this condition remains unknown. Such patients typicalb present with urgency and frequency Of micturition. However, the possibility that these symptoms may be associated with an enhanced sensory input from the bladder wall has not been investigated morphologically. A piexus Of presumptive has been described beneath the epithelium of the human urinary bladder which may be demonstrated using a staining technique for acetylcholinesterase (Gosling et al., 1983; Dixon and. Gilpin, 1987). The purpose of the present study was to assess the density of this acetylcholinesterase-positive subepithelial nerve plexus in a group of W 0 m x - 1 with urodynamically proven idiopathic detrusor instability compared with a group Of asymptomatic agematched controls. In this way it was hoped to determine whether there is any morphological evidence to support the possibility that an increased sensory innervation is associated with idiopathic detrusor instability. I -

Accepted for publication 27 September 1991

Patients and Methods A series of 21 females (mean age 56 years, range 43-77) with long-standing urodynamically proven idiopathic detrusor instability underwent endoscopic cold cup bladder biopsy. Control females with haematuria, but no urgency or frequency of micturition (mean age 56 years, range 29-81), were biopsied in the Same way. In view of the known regional variation in subepithelial nerve distribution (Gosling et al., 1983), all specimens were taken approximate~y2 cm lateral and 2 cm cephalad to the ureteric orifice. Biopsies were rapidly frozen in isopentane cooled in liquid nitrogen and stored at -80°C. Cryostat sections of 1Ofm thickness were stained for acetylcholinesterase using a modification of G ~ mori’s method (1952). For each patient at least 10 non-over~appingfields immediately below the intact epithelium were studied using a final magnification of ~ 4 0 0 Sections . were examined using a calibrated eyepiece graticule aligned parallel to the base of the epithelium. Both the total number of nerve fibres within the grid and the number of nerve fibres which crossed the intersecting grid lines (a technique known as “point counting”) were assessed blindly by the first 2 authors. An interobserver mean of the total and “point” counts for

370

INCREASED SENSORY INNERVATION OF BLADDER IN IDIOPATHIC DETRUSOR INSTABILITY

37 1

the 10 fields from each patient was then calculated. After assessing the normality of distribution of these data using Filliben’s method (Wainwright and Gilbert, 1981), the means for patients and controls were compared using Students’s t test.

Results The region examined for subepithelial nerves extended from the base of the epithelium to a depth of 0.15 mm (Fig.), thus excluding the perivascular nerve plexuses that are frequently associated with the larger submucosal blood vessels which lie at deeper levels in the submucosa. The mean point count ( S.E.) of enzyme-positive subepithelial patients was 91 13imm27 a Fig. Biopsy from a patient with detrusor instability showing for value significantly greater at the 5% level than that the subepithelial plexus of acetylcholinesterase-positivenerve obtained for control subiects (61 f7/mm2; P= fibres. The sauare indicates a tvpical _. area of the subepithelial 0.025) (Table). The values for the total nerve counts, connective tissue that was assessed by point counting ( x 256). while not statistically significantly different, showed the same trend, a higher value (295 f34) being which give an expression of the amount of nerve obtained for the unstable patients compared with per unit area, were generally more consistent within the 10 fields examined for each patient. 254 f26 for the controls. There was no correlation between the age of the However, whereas the total nerve counts varied considerably from region to region within the 10 patient and either the total nerve count or the point fields counted in each specimen, the point counts, count for either controls or unstable patients.



Table Point-counting Studies of Patients and Controls

Patient no. 1

2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 21 mean S.E.

Patients with idiopathic instability

Controls

Age (years)

Point count (per mm2)

Total number of nerve profiles (per mm2)

Age (years)

Point count (per mm2)

Total number of nerve profiles (per mm2)

49 48 61 70 43 50 44 55 50 63 47 48 62 52 54 77 69 57 56 63 60 56

195 124 222 101 34 15 61 177 107 123 40 109 72 87 88 12 15 63 34 170 68 91 13

540 297 437 335 206 64 288 530 253 354 70 245 244 360 472 139 80 220 141 582 330 295 & 34

69 29 59 39 61 69 60 74 68 39 30 73 47 65 60 32 81 52 63 80 29 56

119 44 51 53 47 72 84 85 136 52 84 64 35 112 53 45 14 35 8 42 52 61 27

502 200 232 274 205 363 335 212 466 26 1 350 372 24 1 292 181 101 30 181 65 217 265 254 & 26

372

Discussion The results of the present study have shown that the amount of acetylcholinesterase-positive subepithelial nerves in the urinary bladder is increased in patients with idiopathic detrusor instability compared with controls. This difference was statistically significant when using the values obtained by point counting. The same trend was seen when the results of total nerve counts were compared, although the difference did not reach significance since values for total counts fluctuated widely among the 10 fields examined for each patient. Nerves forming the subepithelial plexus of the human urinary bladder are unrelated to recognised neuro-effector target sites and are therefore considered to represent the terminations of afferent sensory neurons (Gosling et al., 1983).Furthermore, subepithelial nerves of the human urinary bladder have been shown to contain substance P (Islam et al., 1983), a well recognised constituent of primary afferent sensory fibres (Burnstock, 1986). In addition, the fine structure of the subepithelial axonal varicosities has been shown to differ in several respects from typical cholinergic effector terminals, such as occur in profusion among the detrusor smooth muscle cells (Dixon and Gilpin, 1987). The fact that the subepithelial nerves run close to the base of the urothelium, and in some instances actually penetrate between the epithelial cells, suggests that they function to convey sensory information from the bladder mucosa. As yet the precise nature of this sensory information remains unknown. The subepithelial nerve terminals may register touch, pain or temperature, or possibly act as stretch receptors which are stimulated as the bladder fills. Thus the finding that such nerves are relatively abundant in patients with detrusor instability may explain, in part, the increased appreciation of bladder filling giving rise to the urgency and frequency of micturition which are so characteristic of such patients. A previous study of female patients with idiopathic detrusor instability (Gu et al., 1983) focused on the detrusor muscle and demonstrated a relative paucity of vasoactive intestinal polypeptide (VIP) as measured by radioimmunoassay. VIP is believed to act as a neuromodulator with an inhibitory role in the control of detrusor contractile activity (Kinder and Mundy, 1985). More recently a significant decrease in the density of muscarinic receptors, together with an increase in the density of alpha-adrenergic receptors, has been reported in cases of detrusor hyper-reflexia (Restorick and

BRITISH JOURNAL OF UROLOGY

Mundy, 1989). While such studies provide insight into the altered excitatory control of the unstable detrusor muscle, the present study has shown that an increased afferent innervation of the bladder mucosa may also be a significant factor in the aetiology of detrusor instability.

Acknowledgement The authors thank Mr N. J. R. George, University Hospital of South Manchester, for clinical assistance during the course of this study.

References Abrams, P., Feneley, R. and Torrens, M. (1983). Urodynamics. London : Springer-Verlag. Burnstock, G. (1986). Autonomic neuromuscular junctions: current developments and future directions. J . Anat. 146, 130. Dixon, J. S. and Gipin, C. J. (1987). Presumptive sensory axons of the human urinary bladder: a fine structural study. J . Anat. 151, 199-207. Gomori, G. (1952). Microscopic Histochemistry. Principles and Practice. Chicago: University of Chicago Press. Gosling, J. A., Dixon, J. S. and Humpherson, J. R. (1983). Functional Anatomy of the Urinary Tract: an Integrated Text and Colour Atlas. Edinburgh: Churchill Livingstone. Gu, J., Restorick, J. M., Blank, M. A. et d.(1983). Vasoactive intestinal polypeptide in the normal and unstable bladder. Br. J . U r ~ l55,645-641. . Islam, K. N.,Gu, J.,McGregor,G. P. e t d . (1983). Morphological evidence of physiological functioning peptide-containing nerves in the human urinary bladder. In Proceedings of the 13th Annual Meeting of the International Continence Society, Aachen. Pp. 241-249.

Kinder, R. B. and Mundy, A. R. (1985) Inhibition of spontaneous contractile activity in isolated human detrusor muscle strips by vaso-active intestinal polypeptide. Br. J . Urol. 57,20-23. Restorick, J. M. and Mundy, A. R. (1989). The density of cholinergic and alpha and beta adrenergic receptors in the normal and hyper-reflexic human detrusor. Br. J . Urol. 63, 32-35. Wainwright, S. J. and Gilbert, D. I. (1981). A basic computer programme which tests for normality and the presence of outlines in data. Lab. Prac. 30,467469.

The Authors Kate H. Moore, MRACOG, Lecturer, Department of Obstetrics and Gynaecology, University of Liverpool. Sally A. Gilpin, MSc, Research Technician, Department of Cell and Structural Biology, University of Manchester. .I S. . Dixon, BSc, PhD, Senior Lecturer in Histology, University of Manchester. D. H. Richmond, MD, MRCOG, Senior Lecturer, Department of Obstetrics and Gynaecology, University of Liverpool. J. R. Sutherst, MD, FRCOG, Honorary Director of Gynaecological Urodynamic Unit, University of Liverpool. Requests for reprints to: J. S. Dixon, Department of Cell and Structural Biology, Stopford Building, University of Manchester, Manchester MI3 9PT.

Increase in presumptive sensory nerves of the urinary bladder in idiopathic detrusor instability.

The density of subepithelial, presumptive sensory nerves in the bladder wall was assessed in 21 women with idiopathic detrusor instability and compare...
403KB Sizes 0 Downloads 0 Views