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Cryptorchidism: a comprehensive assessment of the terminology and classification

https://doi.org/10.21886/2308-6424-2021-9-2-7-15

Abstract

The analysis of literature data (PubMed database, Google Scholar) is presented, devoted to the problematic study of the cryptorchidism's terminology and classification. The literature periodically calls for systematization terms used in describing the position undescended testis. Due to the confusion in terminology, it is difficult to generalize and analyze the data obtained. The same position of the undescended testis is described differently by various authors, which led to the appearance of many authors' cryptorchidism classifications at the beginning of the 21st century. This review of the literature states the fact that, over time, no consensus has been found regarding the classification of undescended testicles. Currently, there is a need to generalize the available data to select the optimal treatment algorithm. If the treatment algorithm for the palpable testicles is well studied, then the choice of a treatment method for the cryptorchidism non-palpable forms remains debated in the surgical community.

For citation:


Sizonov V.V., Makarov A.G., Kagantsov I.M., Kogan M.I. Cryptorchidism: a comprehensive assessment of the terminology and classification. Vestnik Urologii. 2021;9(2):7-15. (In Russ.) https://doi.org/10.21886/2308-6424-2021-9-2-7-15

Cryptorchidism is the most common abnormality of boys’ reproductive system and, as a result, the most common cause of surgical interventions on the male genitals in children. It is quite clear that the formation of generally accepted diagnostic and therapeutic tactics should be based on a broad understanding of the terminology and classification of developmental abnormalities.

The importance of consensus-building in the terminology used is best emphasized in the manuscript of Erokhin and Volzhin [1], where the authors cited Mallet-Gey and Kestens, who wrote: “It is very important to give words their exact meaning in surgery (maybe, more than in any other field), especially since in some cases the difference in them is not only linguistic in nature...”.

The history of the classification development and the formation of many terms used for the cryptorchid gonad characteristics is associated with attempts to create it basing on the description of the undescended testicle localization. Subsequently, the classification developed due to the expansion of the list of classified parameters – etiology, anatomical features of the retained gonad, clinical aspects.

In 1910, the classification described by Foth [2] was the first to include the division of undescended testicles into retention and ectopia. This principle has been preserved and is used nowadays in the construction of all current classifications.

In 1950, Eisenstaedt [3] in his work suggested not to turn the process of clarifying the cryptorchidism terminology into a word game, which, in his opinion, makes classifications difficult to understand. In 1971, Flinn [4] paid special attention to the level of the testicle position for inclusion in a particular group, in connection with which such concepts as “canalicular” and “extra-canalicular” testicles appear. In 1982, School [5] proposed the division of undescended testicles into retractile, subcutaneous, cryptorchid, and ectopic ones. The author reckoned that the dividing line between the subcutaneous and cryptorchid testicles was the superficial (external) ring of the inguinal canal. In his work, the author describes the cryptorchid testicle in some cases as located within the external inguinal ring, and in other cases, as a non-palpable one. Thus, the same term may be used to describe both palpable and non-palpable testicles. However, from a practical point of view, this leads to confusion in the distribution process of non-palpable testicles in a particular group. One might also think that the subcutaneous testes are not cryptorchid.

In 1969, Popović [6] proposed to include a description of the characteristics of the testicle, trying to expand the classification. The author recommended marking the cryptorchid testicle as a fixed or mobile one since the fixed testicle most often has a flabby consistency and signs of hypotrophy.

Due to the constant appearance of new proposals for various variants of systematization of undescended testicles, classifications became increasingly cumbersome due to the authors’ introduction of various terms and characteristics. In 1988, Mexican colleagues proposed a clinical classification of cryptorchidism based on their own experience of 1010 orchiopexies [7]. The classification was based on the testicle location, size, and mobility in the inguinal canal. In order to determine the mobility of the testicle, the inguinal canal was marked with a surgical marker into three parts, which corresponded to the 1st, 2nd, and 3rd testicle position in the classification; the 4th position was abdominal. The size distribution was carried out by using a ruler-orchidometer into 3 groups: normal, a decrease in the testicle volume up to 30%, a decrease in the testicle volume more than 30%. Summing up the research, the authors concluded that the proposed classification could be a valuable tool for a more uniform analysis of future prospective studies. Even though the proposals made were not widely used, it is worth noting the authors’ desire to systematize and unify the classification.

In 1992, Whitaker [8] stated the lack of success in developing a cryptorchidism classification. The author pointed out that differences in terminology and the lack of standards complicated statistical processing and distorted the true picture of the treatment results of cryptorchidism. In this connection, he demonstrated his classification; from his point of view, it was simple and understandable for practicing surgeons. All undescended testicles were proposed to be divided into inguinal, abdominal, or absent ones.

In 1993, Kaplan [9] stated in his article that the criteria described by Whitaker for the classification of non-descended gonads had disadvantages. According to Kaplan, the position of the testicle after manipulation depends on several factors, in particular, it is important which doctor performed the palpation, which patient was, and how the palpation was performed. The examination was recommended to be carried out in a warm room; the patient should have been in a dorsal recumbent position with his hips drawn out. Before palpation, first of all, the scrotum was examined visually. The classification proposed by the author distinguished two large groups – palpable and non-palpable testicles. Among the palpable ones, the following variants were determined: normal, retractile, ectopic, and non-descended (true cryptorchidism and iatrogenic one). In the group of non-palpable testicles, there were canalicular (sliding), abdominal, and absent (agenesis). In order to avoid further confusion in the classification, the author called for first developing and adopting a common terminology that would help to provide a better assessment while comparing different treatment options for cryptorchidism.

In his fundamental work on cryptorchidism, Erokhin [1] noted that there were periodic discussions in the literature about the terminology unification and clarification in the problem of an undescended testicle. Terminological confusion primarily does not allow analyzing and comparing the clinical materials of different authors; it can contribute to diagnostic errors and, consequently, the choice of the wrong treatment tactics.

The authors of this article suppose that a number of reasons are making it difficult to form a unified cryptorchidism classification. The same term is used for the description of different testicle types (for example, cryptorchidism can be used to refer to a congenital or acquired condition). Synonymous terms are used to describe the same testicle position. For example, cryptorchidism, retentio testis, maldescensus testis. The emergent terms – emerging or gliding testicles moving inwards or outwards from the external inguinal ring are currently not recommended because they are confused with testicles moving in the inner inguinal ring. As for abdominal and canalicular testicles, “cryptorchid testis”, “impalpable testis” can be found as synonyms in the literature. Many of the classifications are based on the results of the testicular position obtained as a result of the surgery, which does not contribute to the formation of the treatment algorithm.

Special focus in the recent literature is paid to the so-called acquired form of cryptorchidism without information about any surgical interventions in the medical history. Such testicles include those that were previously in a normal scrotal position, but as the boy grew, they ceased to be determined in the scrotum. Scorer [10] was the first person to notice that testicles, which were completely descended at birth and can eventually be found outside the scrotum. Since then, some authors have described this phenomenon [11][12].

A significant proportion of patients with this form of cryptorchidism were boys older than 2 years old. Until now, the etiology of this condition remains unclear and is subject to discussion. According to Acerini et al., the prevalence of acquired cryptorchidism in school-age ranges from 1 to 2% [13]. Therefore, there is a question – why was the phenomenon of acquired cryptorchidism not recognized earlier? Traditionally, it was believed that if a boy was born with completely descended testicles, he was not at risk of subsequent cryptorchidism development. Therefore, if the absence of a testicle in the scrotum was determined at a later age, this was attributed to a doctor’s fault as he conducted the child's patronage which resulted in an incorrect interpretation of the retractile testicle, or a late patient’s referral for the medical examination. In the cases of children with acquired cryptorchidism, there is often a discrepancy between the history of the child's development at the dispensary, the parents’ comments, and the doctor's conclusion. Back in 1984, Wyllie [14] recognized that many parents of older boys with undescended testicles insisted that the testicles were in the scrotum in infancy. The need to recognize the existence of an acquired cryptorchidism form has become apparent against the background of a tendency to lower the recommended orchiopexy age. Since the 1940s, this age has steadily declined from post-puberty to the age of 10–12 years in the 1950s, 2–3 years in the late 1970s, and 6 months – 1 year in the present. Due to the existence of a regulated age of testicular descent, there were two peaks in the number of surgeries: at 2–3 years and 10–12 years. It was this second peak that eventually led to the recognition of such a concept as acquired cryptorchidism. The exact etiology and pathogenesis of acquired cryptorchidism are not fully understood, and it is believed that both mechanical and endocrine factors are involved.

In 2003, Hack [15] and his colleagues described their version of the clinical classification of undescended testicles, which divided cryptorchidism into two large groups: congenital and acquired. According to the authors, this classification option is convenient in clinical practice. Congenital forms include abdominal, inguinal, supra-scrotal, and ectopic testicles. The acquired forms were divided into primary and secondary forms. The primary forms are described as testicles that eventually rise from their normal position in the scrotum. The secondary forms are the result of postoperative complications.

Cortesi and his colleagues [16] first used laparoscopy in 1976 for the diagnosis of non-palpable testicles, after which specialists started to understand its role in determining abdominal cryptorchidism forms. Therefore, during the active introduction of laparoscopy for the diagnosis and treatment of cryptorchidism, publications appeared where the authors tried to systematize data on the testicle position in the abdominal cavity [17].

In 1999, Hay and his colleagues [18] proposed to distinguish the following variants of non-palpable testicles: type I – there is not any testicle in the abdominal cavity, the testicular vessels and the sperm duct enter the inner inguinal ring; type II – the sperm duct and the testicular vessels enter the inguinal canal and loop back to the testicle located in the inner inguinal ring; type III — the testicular vessels and the sperm duct do not enter the inguinal canal, the testicle is located near the inner inguinal ring; type IV – the testicle is located in the abdominal cavity and is not connected to the inner inguinal ring. In 2012, the same authors supplemented and refined their classification due to the accumulation of their professional experience [19]. The modified classification was supplemented with a variant when the testicular vessels and the sperm duct, blindly ending, do not enter the inner inguinal ring. There was also such a thing in the classification as a peeping testis when the testicle is fixed in the inner inguinal ring. The peeping testicles were classified as non-palpable and combined with a non-obliterated inner inguinal ring. The testicles located far from the inner inguinal ring were divided into subgroups, where the gonads are located in the iliac region — high testicles, in the pelvic region — low testicles. Also, a separate group appeared in the classification, which includes undescended testicles associated with congenital prune belly syndrome, the persistence of the Muller ducts.

In 2010, Hassan [20] proposed his laparoscopic classification of non-palpable testicles, which includes all the main location variants of the testicles. The authors made up four groups with two subgroups each. Group I – disappeared testicles (vanishing testis). This group included boys with Testicular regression syndrome. In such patients, either during diagnostic laparoscopy or during the revision of the inguinal canal, “testicular nubbins” were detected, which were removed with subsequent histological examination. Depending on the localization, group I was divided into subgroups (IA – canalicular testicles, the ones found in the inguinal canal and IB – intraabdominal), group II – peeping testis (IIA – with a long loop of the duct and IIB – without a long loop of the duct), group III – intraabdominal testicles (IIIA – low abdominal retention, IIIB – high abdominal retention), group IV – violation of sex formation (IVA – persistent Muller duct syndrome, IVB – other variants not differentiated in the groups).

Speaking about the non-palpable testicles, it is necessary to note that the term “peeping testis” is interpreted differently in publications. In 1998, Lindgren [21] described 8 gonads located near the inner inguinal ring, which seemed to peek into the inguinal canal. Leung [22] attributed 13 gonads located within 2 cm proximal to the inner inguinal ring to the group of peeping testicles. Bae [23] described the peeping testicle as intra-abdominal in combination with a persistent vaginal process of the peritoneum, which enters the inner inguinal ring, in which the testicle was located.

The cryptorchidism classifications are also given in the recommendations of the following: European Association of Urology (EAU) [24], American Urological Association (AUA) [25], Canadian Urological Association (CUA) [26], German Society of Urology [27], Association of Pediatric Surgeons of Russia [28]. According to the opinion of the authors of this article, the classification proposed by the EAU is the easiest one for understanding among all the listed recommendations, as it includes all the main options for the position of the testicle that meets the requirements of today's surgery. In the course of analyzing the problem, the authors of this article attempted to combine the useful elements of these classifications (Fig. 1).

The authors suppose that the undescended testicles should initially be divided into two large groups: cryptorchidism and ectopia, i.e., ectopia should be attributed to the variant of an undescended testicle, and not to cryptorchidism. The term “congenital cryptorchidism” does not cause any controversy and is found in all recommendations and classifications. The term “acquired cryptorchidism” is also described in all recommendations, except for the Russian ones. All the classifications and recommendations, without exception, divide congenital cryptorchidism into palpable and non-palpable variants. Among the palpable forms of cryptorchidism in all classifications, there is a single definition of the “retractile testicle” concept previously considered false cryptorchidism or pseudo cryptorchidism. In most recommendations, palpable forms of cryptorchidism are divided into inguinal and retractile ones. However, in the AUA guidelines, the testicles located in the inguinal canal are called canalicular, and the term prescrotal is used for the gonads located at the entrance to the scrotum. At the same time, the authors of this article think that there may be ambiguity in determining the differences between the retractile and prescrotal testicles. The term “canalicular” is not considered to be an adequate one in use, because it is a general concept of any canal. In the context of cryptorchidism, the testicle, following the way of descent, can linger only in the inguinal canal but in no other. In the group of palpable testicles, the term “inguinal ectopia” is interesting, which is found in the European and German classifications. In this form of ectopia, the testicle is located in a pocket formed between the Scarp fascia and the external oblique fascia adjacent to the superficial ring of the inguinal canal. In the literature, this anatomical formation is named the Denis Browne pouch or the superficial inguinal pouch [29]. This variant of ectopia is believed to be called not inguinal, but supra-inguinal since the testicle is wrapped over the aponeurosis while coming out of the external inguinal ring. As for the term retractile and pendulum-shaped testicles, which belong to the same subgroup of congenital palpable cryptorchidism, they cannot be considered synonymous. It is optimal to use the term “retractile testicle”, because this condition describes the raising of the gonad to a different height from its original position, in contrast to the term “pendular” (pendulum-like). After all, the principle of the pendulum work is based on the principle of oscillation within certain limits. Therefore, the term “retractile testicle” is considered to be more accurate. The term “palpable testicles” (prescrotal and gliding), found only in the American and German classifications, was also analyzed; therefore, it was concluded that the use of the term “supra-scrotal testicle” is more preferable for the convenience of understanding the testicle position.

Fig. 1. Cryptorchidism classifications. Numbers from 1 to 5 correspond to the offers of various urological and surgical associations: 1 – European Association of Urology, 2 – American Urological Association, 3 – Canadian Urological Association, 4 – Germany Society of Urology, 5 – Russian Association of Pediatric Surgeons. Federal clinical guidelines. IIR — internal inguinal ring

Among non-palpable gonads, such a position as ectopia should be discussed as well. In different classifications, it is possible to find such concepts as ectopia of the testicle in the area of the kidney and bladder. Therefore, there is a question of whether this condition should be considered an ectopia. The authors of this article suppose that such a gonad ectopia in the kidney area should be attributed to a variant of high abdominal retention, and low retention – near the bladder.

The subgroup of peeping testicles (fixed at the inner ring of the inguinal canal) is described in only three of the five classifications mentioned above. Patients belonging to this group are of great interest for medical practice, as the methods of managing children with peeping testicles remain a subject of discussion. This is especially true in cases where the testicle detected during laparoscopy does not fit into the existing classification and treatment approach. Analyzing their own experience, the authors of this article considered it necessary to identify an additional group of patients with non-palpable testicles. These are gonads that move quite freely from the abdominal cavity to the inguinal canal and back, depending on the position of the child, its activity, which is associated with changes in intra-abdominal pressure. In three authors’ patients, the fact of finding a testicle during physical examination and ultrasound was documented in the anamnesis, and it was impossible to palpate the testicle while medical examination during the patient’s surgery under anesthesia due to the testicle migration into the abdominal cavity. Such a variety of non-palpable testicles, namely, migrating testicles, was found only in one publication in 2020, where a similar case is given [30]. The authors describe a peeping testicle as a moving one, not from the abdominal cavity to the inguinal canal, but in the opposite direction. This patient underwent inguinal orchiopexy without additional laparoscopic mobilization.

It is important to emphasize the points which do not result in consensus. First of all, these are different anatomical variants of abdominal testicles, when the lack of a single terminological approach does not allow standardizing the algorithms of surgical treatment in this most problematic group of patients (from the effectiveness point of view). Second, there is another thing that was not reflected in the classifications, and it is the status of the gonads, which easily move from the abdominal cavity to the inguinal canal. They can be classified in one case as palpable, and as non-palpable in the other. Choosing the optimal surgical approach for these patients is a difficult task, since the relegation of such testicles from the inguinal access is unattainable due to the lack of length of the testicular vessels, and the use of the Fowler-Stephens technology seems unjustified due to the attitude to such a testicle as a still palpable (although periodically) one.

In conclusion, it should be emphasized that the EAU cryptorchidism classification contributes to the standardization of diagnostic and therapeutic approaches to palpable forms of cryptorchidism. However, some positions in the classification of non-palpable forms remain unresolved and agreed, while maintaining the relevance of research in this area. In this regard, the authors’ proposals for clarifying the terms and classification are submitted for discussion.

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About the Authors

V. V. Sizonov
Rostov State Medical University; Rostov-on-Don Regional Children's Clinical Hospital
Russian Federation

Vladimir V. Sizonov - M.D., Dr.Sc.(M), Assoc. Prof. (Docent); Prof., Dept. of Urology and Human Reproductive Health (with Pediatric Urology and Andrology Course), Rostov State Medical University; Head, Pediatric Urological and Andrological Division, Rostov-on-Don Regional Children's Clinical Hospital.

344022, Rostov-on-Don, 29 Nakhichevanskiy ln.; 344015, Rostov-on-Don, 14 339th Strelkovoy Divisii st.


Competing Interests:

The authors declare no conflicts of interest.



A. G. Makarov
Rostov-on-Don Regional Children's Clinical Hospital
Russian Federation

Alexey G. Makarov - M.D.; Pediatric Urologist and Andrologist; Pediatric Urological and Andrological Division, Rostov-on-Don Regional Children's Clinical Hospital.

344015, Rostov-on-Don, 14 339th Strelkovoy Divisii st.

Tel.: +7 (904) 345-25-49


Competing Interests:

The authors declare no conflicts of interest.



I. M. Kagantsov
V.A. Almazov National Medical Research Centre; Pitirim Sorokin Syktyvkar State University
Russian Federation

Ilya M. Kagantsov - M.D., Dr.Sc.(M), Assoc. Prof. (Docent); Chief Researcher, Research Laboratory for Surgery of Congenital and Hereditary Pathology, Institute of Perinatology and Pediatrics, V.A. Almazov National Medical Research Centre; Prof., Dept of Surgical Diseases, Pitirim Sorokin Syktyvkar State University.

197341, St. Petersburg, 2 Akkuratova st.


Competing Interests:

The authors declare no conflicts of interest.



M. I. Kogan
Rostov State Medical University
Russian Federation

Mikhail I. Kogan - Honored Scientist of the Russian Federation, M.D., Dr.Sc.(M), Full Prof.; Head, Dept. of Urology and Human Reproductive Health (with Pediatric Urology and Andrology Course), Rostov State Medical University.

197341, St. Petersburg, 2 Akkuratova st.


Competing Interests:

The authors declare no conflicts of interest.



For citation:


Sizonov V.V., Makarov A.G., Kagantsov I.M., Kogan M.I. Cryptorchidism: a comprehensive assessment of the terminology and classification. Vestnik Urologii. 2021;9(2):7-15. (In Russ.) https://doi.org/10.21886/2308-6424-2021-9-2-7-15

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