rior urethral anomaly there were no secondary upper tractchanges, and he concluded that the condition is more commonthan previously appreciated, ranging from mild to severe.2 Also,Crooks documented 16 of 36 patients with posterior urethralobstruction who presented with voiding dysfunction but normalexcretory urography.11 The results of our study have also shownthat congenital obstruction of the posterior urethra appears toexist in a spectrum of severity but the lesion is a mem-brane.3,4,10 Furthermore, early presentation correlates with ahigher degree of obstruction, which is why children who presentlate often have a better prognosis than those who present ear-ly.12 However, a similar endoscopic appearance of severe lesionswith different upper tract changes would indicate that the blad-der response to outflow impedance and not just the membranedegree influences the clinical outcome in boys with high gradeobstruction.

Of the 9 patients with a minimal membrane for whomsymptomatology was available two, 5 and 2 were diagnosedduring the investigation of prenatal hydronephrosis, urinarytract infection and voiding dysfunction, respectively. How-ever, all symptoms and radiological findings were due toother factors and represented incidental findings other thana pathological condition. In the 86 cases studied we alsoidentified and confirmed the position and extent of the exter-nal sphincter and its relationship to the congenital posteriorurethral membrane.

The study of Hendren led to the suggestion that the proximalextent of the external sphincter is distal to the obstruction.Further assessment by Stephens showed that the proximalextent of the external sphincter was above and overlying thefolds attaching between the verumontanum and obstruction.13

It has since been demonstrated that rather than being a ring-like structure distal to the prostate the external sphincter con-sists of a complex tubular arrangement of muscle fibers extend-ing down from the bladder.14,15 This finding has been supportedby a study of video endoscopic recordings correlated with ure-thral radiological findings revealing in 42 cases a congenitalobstructive posterior urethral membrane distal to the proximalextent of the sphincter.10 Consistent with this finding in allexcept 4 of our 86 patients in whom a lesion was visualized theproximal end of the external sphincter was located above thecongenital obstructive posterior urethral membrane.

CONCLUSIONS

This study provides further evidence that a posterior ure-thral membrane may vary in degree, implying that all pos-terior urethral membranous lesions have the same embryol-ogy but a different expression of functional anatomysubsequently. In addition, the membranous nature of theobstructive lesion with a posterior defect and connectingfolds to the verumontanum was confirmed, as was its rela-tionship to the tubular external sphincter.

REFERENCES

1. Dewan, P. A.: Urethral valves or COPUM? Changing the nomen-clature. Contemp Urol, p. 15, September, 1999

2. Hendren, W. H.: Posterior urethral valves in boys. A broadclinical spectrum. J Urol, 106: 298, 1971

3. Dewan, P. A.: Congenital obstructing posterior urethral mem-brane (COPUM): further evidence for a common morphologicaldiagnosis. Pediatr Surg Int, 8: 45, 1993

4. Dewan, P. A. and Goh, D. G.: Variable expression of the congen-ital obstructive posterior urethral membranes. Urology, 45:507, 1995

5. Young, H. H., Frontz, W. A. and Baldwin, J. C.: Congenitalobstruction of the posterior urethra. J Urol, 3: 289, 1919

6. Presman, D.: Congenital valves of the posterior urethra. J Urol,86: 602, 1961

7. Robertson, W. B. and Hayes, J. A.: Congenital diaphragmaticobstruction of the male urethra. Br J Urol, 41: 592, 1969

8. Johnston, J. H. and Kulatilake, A. E.: Posterior urethral valves:

results and sequelae. In: Problems in Pediatric Urology. Ed-ited by J. H. Johnston and R. J. Scholteijer. Amsterdam:Exerpta Medica. p. 161, 1972

9. Dewan, P. A., Keenan, R. J., Lequesne, G. W. et al: Cobb’s collaror prolapsed congenital obstructive posterior urethral mem-brane (COPUM). Br J Urol, 73: 91, 1994

10. Dewan, P. A., Pillay, S. and Kaye, K.: Correlation of the endo-scopic and radiological anatomy of congenital urethral ob-struction and the external urethral sphincter. Br J Urol, 79:790, 1997

11. Crooks, K. K.: The protean aspects of posterior urethral valves.J. Urol., 126: 763–766, 1996

12. Dinneen, M. D. and Duffy, P. G.: Posterior urethral valves. Br. J.Urol., 78: 275–281, 1996

13. Stephens, F. D.: Urethral obstruction in childhood. In: Congen-ital Malformations of the Rectum, Anus and GenitourinaryTracts. Edited by R. Webster. London: E&S Livingstone,chapt. 14, p. 209, 1963

14. Oelrich, T. M.: The urethral sphincter muscle in the male. Am JAnat, 158: 229, 1980

15. Kaye, K., Milne, N., Creed, K. et al: The “urogenital diaphragm”,external urethral sphincter and radical prostatectomy. Aust.N Z J Surg, 67: 40, 1997

EDITORIAL COMMENTS

The authors have confirmed Hendren’s assertion that the mor-phology of posterior urethral valves is variable.

This report is part of a series of attempts to convince pediatricurologists that urethral valves should be renamed membranes.While the pursuit of this argument may be worthwhile, the descrip-tive classification the authors used may be more relevant. Whilearguments rage as to the best algorithm for treating valves, fewattempt to classify the degree of obstruction a valve causes and, thus,it is hard to compare 1 series with another. The classification ofvalves into mild, moderate and severe based on cystoscopic appear-ance may help to solve this problem. It remains to be shown if theappearance of a valve correlates with its urodynamic effect.

With regard to the discussion about whether valves are actuallymembranes, by strict definition a valve is a mechanism that allows flowin 1 direction but not in the other, which the authors have not demon-strated. They have not measured the resistance to flow from proximal todistal and compared it to the resistance to flow from distal to proximal.For the most part, anatomists and pathologists in the past have usedthe term loosely. There are other membrane-like structures in the bodythat are called valves without a functional basis, for example the valveof Vieussens in the cerebellum.

I note that the authors perform routine cystoscopy to follow valveablation. A voiding cystourethrogram is a better method to follow pa-tients and I reserve cystoscopy for those who appear to have residualobstruction. I am not yet convinced that routine circumcision for thesepatients is good. I disagree that the sphincter position can be accuratelyassessed at cystoscopy, as it gives only a vague idea of location. Otherstudies have shown the external sphincter to be a conical shape, ex-tending from the bladder neck down past the verumontanum. On crosssection it has an omega configuration. Thus, while I agree that theexternal sphincter complex extends from the bladder neck to below avalve, I am not sure that this can be deduced at cystoscopy.

Graham SmithDepartment of UrologyThe Children’s Hospital at WestmeadSydney, Australia

Dewan has long been a student of obstructive uropathy in the lowerurinary tract, and this article represents a culmination of thought andobservation gained through a career of study. In 1840 Budd, physicianto the Seamen’s Hospital in Dreadnought, attached the term “valve” tosome urethral obstructions. In an early volume of The Lancet Buddreported on a 16-year-old sailor who died in the hospital after a few daysof “insensibility.”1 Autopsy revealed “extraordinary dilatation of thekidneys, ureters, and bladder, in consequence of a membranous fold inthe urethra, which acted as a valve, and prevented free escape of theurine from the bladder.” Young et al put posterior urethral valves on theclinical map in 1919 with an analysis of 12 personal patients and aliterature review of 23 others, thereby producing terminology that hasendured until now (reference 5 in article). It was a deteriorating childwith urethral valves who inspired David Innes Williams in 1949 tofocus his career on pediatric urological disorders, thereby initiating anew medical subspecialty (personal communication, 1986). In 1971

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