Percentage of Undescended Testis with Patent Processus Vaginalis
Approximately 60-70% of undescended testes are associated with a patent processus vaginalis (PPV), based on intraoperative findings during orchiopexy.
Epidemiological Data from Surgical Series
The prevalence of PPV in cryptorchidism varies by study methodology and patient population:
In boys with undescended testes undergoing orchiopexy, 71% (68 of 96 patients) had a patent processus vaginalis when one was present and communicating with the testis 1
A more recent surgical series found 62% (75 of 121 testes) had a patent processus vaginalis at the time of scrotal orchiopexy 2
Among boys with ectopic or ascended testes, approximately 20% overall required inguinal incision for PPV repair, with rates of 26% in children younger than 2 years, 15% in those 2-6 years old, and 19% in those older than 6 years 3
Comparison with General Population
This high prevalence in cryptorchid testes contrasts sharply with the general population:
The reported prevalence of PPV is as high as 80% in term male infants in the general population, but this declines significantly with age 4
The relationship between the processus vaginalis and testicular descent explains why more than 90% of pediatric inguinal hernias are diagnosed in boys 4
Mechanistic Relationship
The association between undescended testis and PPV is mechanistically linked:
During normal testicular descent between 25-35 weeks gestation, the testis descends through the inguinal canal, drawing with it an extension of the peritoneal lining that defines the processus vaginalis 4
Normally, the processus vaginalis obliterates and involutes, leaving no communication between the intra-abdominal peritoneal cavity and the scrotum 4
Incomplete involution results in a patent processus vaginalis, through which fluid can travel and accumulate as a hydrocele, or through which intra-abdominal structures such as bowel may herniate 4, 5
Clinical Implications
The high prevalence of PPV in cryptorchidism has important surgical implications:
Retractile testes are at increased risk for testicular ascent, which may be mechanistically related to the presence of a hyperactive cremasteric reflex, foreshortened patent processus vaginalis, or entrapping adhesions 4
Approximately one third (34%) of boys with a unilateral palpable undescended testis will have a contralateral patent processus vaginalis, with the rate increasing to 52% if the undescended testis is distal to the external ring 6
All inguinal hernias in infants should be repaired to avoid the risk of bowel incarceration and gonadal infarction/atrophy 4, 5
Important Caveats
Not all patent processus vaginalis cases result in clinical hernias—the estimated childhood risk of developing an inguinal hernia with a PPV is between 25-50% 4, 7. This distinction is critical because the presence of PPV alone does not mandate intervention unless there is an associated undescended testis requiring orchiopexy or a clinically apparent hernia.