RECONSTRUCTIVE UROLOGY

The Anatomy and Embryology of Posterior Urethral Valves
Krishnan A, de Souza A, Konijeti R, Baskin LS
Department of Urology, University of California-San Francisco Children’s Medical Center, University of California, San Francisco, California, USA
J Urol. 2006; 175: 1214-20

• Purpose: We reviewed the literature to better elucidate the history behind our understanding of the anatomy, classification and embryology of posterior urethral valves.
• Materials and Methods: A directed MEDLINE literature review of the anatomy, classification and embryology of posterior urethral valves was performed. An effort was made to focus on the most frequently cited historical articles as well as those including detailed anatomical analyses of fetal specimens. Also included was the analysis of a specimen obtained at our institution in a novel manner that to our knowledge has not been previously described in the literature with respect to the anatomy of posterior urethral valves.
• Results: The precise origins regarding the anatomy and embryology of posterior urethral valves remain undefined. However, the literature is abundant in theories regarding the origin of posterior urethral valves, based primarily on small uncontrolled series or case reports. There are a limited number of reports of the anatomy of posterior urethral valves in methodical fashion using reproducible scientific techniques such as histopathology. These reports are invaluable for providing a foundation of how to properly study and define the origins of posterior urethral valves.
• Conclusions: Elucidating this most fundamental feature of a congenital condition central to the practice of pediatric urology is essential. More well designed studies specifically with this goal in mind are necessary. Incorporating new reconstructive imaging modalities may assist us in pinpointing the elusive origins of the embryology and anatomy of posterior urethral valves.
  
  
• Editorial Comment
  Although posterior urethral valves have a recognized incidence of 1/5000 to 8000 in male newborns, it is not known how common it might cause fetal demise (1).
  Almost 2 centuries after its first description, the posterior urethral valves is newly investigated by Krishnan et al. with modern computer imaging in combination with histopathology in one of the few virgin cases of an untreated malformation known as a posterior urethral valve which helped to clarify its origin.
  Until week 9, male and female urethral development is identical; whereas by week 14, the male urethra completes its development (2). Many of the former anatomical descriptions were misleading because of prior manipulations to the histological investigations with the result of several different described types first recognized by Dewan & Goh (3).
  Krishnan et al. investigated the rare case of an untreated posterior urethral valve histologically by cross sectioning and reconstructed by three-dimensionally using computer imaging from the histology of the infant’s urethra. With this investigation they revealed, as several times prior (4,5), the results of anatomical development in normal and malformed urethras. They demonstrated, with their outstanding work after an all-around literature analysis that the theory of Dewan et al. (6), seems to be the most likely with the single congenital obstructing posterior urethral membrane (COPUM).
  Works similar to Krishnan et al. need our recognition/attention because they complete the understanding of the embryological development. This combination of histology and three-dimensional reconstruction helps to recognize and understand the embryonic development and will help to improve early treatment.

References
1. Park JM: Normal and Anomalous Development of the Urogenital System. In: Walsh PC, Retik AB, Vaughan ED, Wein Jr AJ (eds.), Campbell’s Urology. Philadelphia, WB Saunders Co., 8th ed., vol 3, chapt. 49, pp.1735-1764, 2002.
2. Marsden RT: Posterior urethral valves in adults. Br J Urol. 1969; 41: 586-91.
3. Dewan PA, Goh DG: Variable expression of the congenital obstructive posterior urethral membrane. Urology. 1995; 45: 507-9.
4. Yucel S, Baskin LS: Neuroanatomy of the male urethra and perineum. BJU Int. 2003; 92: 624-30.
5. Kurzrock EA, Baskin LS, Cunha GR: Ontogeny of the male urethra: theory of endodermale differentation. Differentation. 1999; 64: 115-22.
6. Dewan PA, Keenan RJ, Morris LL, Le Quesne GW: Congenital urethral obstruction: Cobb’s collar or prolapsed congenital obstruction posterior urethral membrane (COPUM). Br J Urol. 1994; 73: 91-5.

Dr. Arnulf Stenzl, Dr. Joerg Seibold
& Dr. Karl-Dietrich Sievert
Department of Urology
Eberhard-Karls-University Tuebingen
Tuebingen, Germany