Since scientific recommendations regarding the timing of orchidopexy in UDT were released, numerous studies have dealt with their implementation, starting in the early 1960s [4, 7]. Prior to these recommendations only a small percentage of boys (5%) underwent surgery before their second birthday, with a high mean age.However, since the early 1990s, these rates have significantly improved, ranging from 17 to 64% [16, 18, 22]. The rate of orchidopexies before the completion of the first 12 months of life ranged from 3 to 24% [19, 21]. Few studies adhere to the AUA recommendation of reporting rates of orchidopexy before the 18th month of life. The reported rates range from 16% to even 87%. However, these studies exclude orchidopexies performed after the age of 5 years in an attempt to exclude acquired cases [24, 25]. Overall, no clear improvement trend over time was reported highlighting the discrepancy between the recommendations and reality. In 2009, a multicentric approach was initiated to collect data on UDT. Our study revealed low rates (18.7%) of timely orchidopexy before the age of 12 months [8]. Continuous data analyses of our study group over the years have shown no relevant changes in these rates [9]. In our recent update, the rate of timely surgery before the age of 12 months in congenital cases remains low at approximately 25%, but it is higher than in all other comparable studies. In contrast, in a recent German study of InEK and BNKD data (Institute for the Remuneration System in Hospitals, professional association of pediatric surgeons) only 15% of patients treated in hospitals and only 5% of those treated in outpatient services were younger than one year [20].

Classifying solely based on age groups alone, carries the risk of imprecision, and heterogeneous age groups make a comparison challenging [11, 13, 17, 20, 23, 24]. Therefore, a closer look at the exact ages of the individuals is necessary. However, most studies that investigate the exact ages at surgery only provide the mean age, without any information about previous testing for normal distribution (Table 1).This lack of information hampers the interpretation of the data [4, 14,15,16, 18, 21, 22, 26,27,28]. The mean ages reported ranged from 44 to 64 months [15, 27] with an upward aberration from periods before the recommendations of the pediatric urologic associations of > 100 months [4], and one downward aberration in a very small cohort of only 88 cases with 23 months [16]. For comparative purposes, we calculated the mean age of our overall cohort to be 34 months. The median age at orchidopexy of 16 months for congenital cases in our cohort was similar to the AUA recommendation and markedly better than the median ages reported in other studies, which ranged from 19 to 30 or even 60 months [10, 19, 25].

In Germany, the first version of a guideline on the diagnosis and treatment of undescended testicles was published by the AWMF in 1999 with the recommendation of orchidopexy before the second birthday. Since then, it has been continuously updated in line with the latest scientific findings. The last two versions of the guideline, from 2009 and 2016, recommend treatment between the 6th and 12th month of life for primary undescended testicles [8, 29, 30]. In 2009, we started our evaluation to analyze the impact of the guideline recommendation on the clinical practice, but in fact the expected effect of significantly earlier orchidopexy could not be reproduced.

As a small aside, the risk of distorting the results by simply looking at age groups is already apparent in the focus on the pandemic years 2020 to 2022. In our cohort, the pandemic did result in less orchidopexies per year in 2020ß to 2022, a markedly longer time from referral to surgery, lower rates of orchidopexies in boys younger than 12 months, but not in higher median ages. The reduction of elective surgeries due to reduced surgical capacity during the pandemic and the hesitancy of some parents to schedule operations that may not have been perceived by them as urgent may be one explanation of the lower rates [31]. Furthermore, orchidopexies in children well beyond their first birthday may therefore have been considered less urgently in the allocation of surgical appointments than those in whom an orchidopexy could be performed in a timely manner. It may be anticipated that the number of orchidopexies will increase significantly in the following years, with the median age at surgery increasing at the same time. This will be investigated in the following studies.

The reason for the better results in our study regarding the age of orchidopexy, is due to the distinction made between congenital and acquired UDT. However, distinguishing between congenital and acquired UDT is discussed controversially. In the past, some authors believed that acquired UDT was actually an unrecognized congenital UDT [32]. In contrast, a prospective longitudinal population-based child cohort study of over 1000 boys showed that acquired UDT accounts for up to 58% of all cases of cryptorchidism. These findings are supported by several other studies [33]. In the context of this data, the collected data on acquired and congenital UDT of our current study is comprehensible. However, it is important to note thatthe anamnestic recording may be subject to some degree of error. For the early preventive examinations for children (U1–U9, J1), an obligation to participate is anchored in the Child Protection Act of Baden-Württemberg (§ 1 para. 1 sentence 1 KiSchG BW). From U2, which is typically conducted between the 3rd and 10th day of life, the genital and thus the testicular position is regularly examined as part of the thorough physical examination and deviations are noted accordingly. Acquired UDT results from inadequate longitudinal growth, restraining fibrous portions, spermatic cord or other factors such as iatrogenic after inguinal hernia surgery, that occurs at newborn age [33]. Studies on timing of orchidopexy are mostly based on DRG and OPS code-based data from health insurance companies or national healthcare system institutions, which do not differentiate between congenital and acquired UDT. Therefore, it is likely that the actual age of patients with congenital UDT is lower in these cohorts. We found no significant anatomical differences (e.g. hydatid or testis-epididymis-dissociation) between acquired and congenital UDT. A marked majority of cases of acquired UDT were located epifascial or in the low inguinal canal, while a slight majority of congenital cases were found in the middle and high inguinal canal or abdominal. The fact of higher rates of prematurity in boys with congenital UDT was not surprising.

However, to further reduce the median age of orchidopexy in congenital UDT,optimizing pediatric referral patterns is crucial. Our study, similar to other studies, identified a late referral as a primary reason for delayed surgery. High rates of late presentation have already been reported, indicating a need for modifications of the guidelines to address this issue [12, 25, 27, 34]. Second most likely comorbidities of boys led to delayed orchidopexy. The avoidance of multiple anesthesia for different operations certainly plays a relevant role and can only be handled differently to a limited extent. In addition, serious health restrictions can relativize the relevance of a timely orchidopexy in individual cases.

In summary, the herein reported cohort revealed a high rate of orchidopexies in congenital UDT below the age of 24 months and the highest rate of orchidopexies below the age of 12 months as well as the lowest median age compared to literature. This is certainly based on the exclusion of the acquired UDT, but there may also be a bias towards earlier orchidopexies due to ongoing years of data collection and evaluation in our centress. The fact that early preventive examinations in childhood are legally mandated in Baden-Württemberg may also contribute to a sbetter guideline consistency. As age at orchidopexy may be an indicator of the quality of the respective regional health service, significant regional variations are described in other studies [13].

The study is limited by its retrospective nature, which is a common limitation in studies on age at orchidopexy. However, the detailed data acquisition with discrimination between acquired and congenital UDT balances this limitation. by. In addition, the data is restricted to a small geographical area and a specific group of pediatric surgical/urological units in Germany, which limits the ability to compare with other units in different parts of the country.