Sports participation in single-organ athletes remains controversial. These athletes include those with a single eye, kidney, testicle, or ovary. Given the physiologic and psychologic benefits of sports participation, it is essential not to restrict single-organ athletes from sports without an individualized discussion with the athlete and his or her family. Physicians should consider the risk of injury to a solitary organ, the subsequent post-injury comorbidities or mortality, and the psychosocial consequences of sports restriction in the evaluation of single-organ athletes.
Pediatric athletes are considered monocular when their best-corrected visual acuity in one eye is worse than 20/40 (1). Adults are considered monocular if their quality of life would be affected with impairment to their eye with the best visual acuity (1,2). Children between the ages of 10 and 17 years have the highest rate of sports-related ophthalmologic injuries, which results in a significantly greater concern for ocular injuries and permanent blindness in pediatric monocular athletes (3,4). The sports with the highest risk of eye injury include basketball, baseball, softball, hockey, martial arts, and boxing (2,3). Moderate-risk sports include tennis, golf, football, and soccer (2,3). Low- to minimal-risk sports include swimming, wrestling, skiing, track and field, and gymnastics (2,3).
The American Academy of Pediatrics (AAP) and the American Academy of Ophthalmology (AAO) recommend that all monocular athletes wear appropriate eye protection at all times during sporting, recreational, and work-related activities (2). The AAP and AAO recommend against monocular athletes' participation in boxing, wrestling, and full-contact martial arts, because protective eyewear is not practical in these sports (2,3). Eye protection should meet the American Society for Testing and Materials standards and be made of polycarbonate or Trivex lenses that are compatible with participation in the athlete's sport. Properly fitting protective eyewear can reduce the risk of serious eye injury by 90% (1–3).
Single-kidney athletes are those with only one morphologically normal kidney, without congenital abnormalities, that resides in the usual anatomic position (5). A survey study conducted by Grinsell et al. in 2012 found that 62% of pediatric nephrologists recommended against contact sports participation, due to a concern of injury and loss of function, and 86% would recommend against participation in American football (3,5). Grinsell et al. found only one reported case of renal injury to a single-kidney athlete that did not result in long-term complications (5,6). High-risk sports for renal injury include extreme skiing and snowboarding, horse racing, and cycling (7,8). Moderate-risk sports include football, soccer, and hockey (7,8). Low-risk sports included baseball, basketball, lacrosse, and wrestling (7,8).
The risk and implications of renal injury in single-kidney athletes participating in contact or collision sports continues to be a controversial topic. Though the consequences of a catastrophic renal injury to a single-kidney athlete are significant, the risk of catastrophic injury to unpaired organs to include the brain, heart, and spine is significantly higher (5).
The AAP recommends a “qualified yes” for contact and collision sports participation in athletes with a solitary kidney in the setting of an individual assessment (5). Although protective padding is available, routine use is not recommended because current evidence does not suggest that the use of protective padding decreases the risk of renal injury (9).
Athletes with a single testicle should be informed of the risk of injury and loss of fertility in contact, collision, and limited-contact sports. In a study done in 2014 by Bieniek and Sumfest (10), across all sports, approximately 18% of athletes reported at least one testicular injury, and 36% of athletes reported observing a testicular injury in a teammate. Higher risk sports include lacrosse, wrestling, baseball, and football (10). Although there is limited evidence to support the use of a protective cup to prevent testicular injuries, the AAP recommends that all athletes with an undescended testicle or an absence of one testicle may participate in sports with the use of a protective cup (7).
There is minimal risk of injury to a single-ovary athlete. As a result, the AAP recommends full participation in single-ovary athletes (7).
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