The Orchidometer


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Copyright © 2009
Purpose and description of use

An orchidometer is a device for determining testicular volume, shown by Prader in the 1960s to be a reliable indicator of the progress of puberty in boys. The following paragraphs and the list of references are a quote from the website of the Swedish company Dynavit Motion, suppliers of the orchidometer illustrated here.

Determination of testicular volume is of great value when assessing growth and development during male puberty and adolescence, when evaluting human male fertility and in clinical studies of various endocrinopathies and chromosomal aberrations.

Tecticular size can be used as a clinical criterion of testicular function permitting a rough assessment of spermatogenesis, while the testosterone production by the Leyding cells can be evaluated by the development of the male secondary characteristics.

Comparative palpation of the testes by means of an orchidometer ad modum  Prader has been demonstrated to be a reliable method that causes little embarrassment to the patient. The orchidometer consists of twelve models of various volumes from 1-25 ml having the form of ellipsoids of revolution. One testis is palpated with one hand while the model "testes" are held in the other hand. The ellipsoids are searched to find the one which is nearest to the testis in size.


Prader, A.: Testicular size: Assessment and clinical importance. Triangle 7:240-243, 1966.

Tanner, J.M. et al.: Clinical longitudinal standards for height, weight, height velocity, weight velocity and stages of puberty. Arch Dis Childh 51:170-179, 1976.

Taranger, J. et al.: Somatic pubertal development. Acta Paediatr Scand, suppl 258:121-135, 1976

Waaler, P.E. et al.: Studies in normal male puberty. Acta Paediatr Scand, suppl 249, 1974.

Zachmann, al.: Testicular volume during adolescence, cross-sectional and longitudinal studies. Helv Pediatr Acta 29:61-72, 1974.

Relevance to circumcision

During puberty, a layer of fat develops between the inner and outer foreskin. This makes circumcision more difficult, especially if a fit-&-wear clamp such as a Plastibell or Tara KLamp is to be used. If, for whatever reason, circumcision has not taken place in infancy but is required before adulthood, it is advisable to proceed no later than the boundary between Tanner developmental Stages 1 and 2. At this point the larger of a boy’s two testes (which rarely develop simultaneously) will by definition have a volume of 4 ml. The significance of the 4 ml figure is emphasised in the orchidometer design; that is the bead with the brown colour.

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