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Blunt Trauma Reveals a Single Kidney: A Disqualification Dilemma

Tom Terrell, MD, MPhil; Mike Woods, DO; David O. Hough, MD**


In Brief: An 18-year-old stunt water-skier collided with a stationary boat, causing an impact to his right flank and thigh. Imaging studies revealed spondylolisthesis, fractures to the transverse processes of three lumbar vertebrae, and a single right kidney, which was uninjured. The kidney lay slightly anterior to the normal position, making it more vulnerable to injury. Consequently, the patient was advised to avoid waterskiing and all collision sports. This case points up the dilemmas physicians may face when treating athletes who have just one member of a paired organ.

In treating athletes and physically active patients, physicians sometimes encounter unexpected findings that raise difficult questions about the safety of resuming sports participation. Such was true in the case described below, involving a young athlete in the relatively high-risk sport of stunt waterskiing. The case serves as a reminder of the need to be alert for the unusual, aware of the special risks faced by athletes, and diligent in explaining the risks to athletes and their families.

Case History

An 18-year-old competitive stunt water-skier, while racing at 40 miles per hour, collided with a stationary boat. He was struck on his right side and thigh, and the impact caused extreme lateral flexion of his lumbar spine.

The patient's history included surgery for undescended testes at age 5 but was otherwise unremarkable. On initial physical examination, he had pain and spasm over the right iliac wing and minor bruising over the right flank. He also had pain with lateral and anteroposterior compression of the pelvis, pain in the lumbosacral region, and tenderness along his lateral right thigh. The patient's abdomen was flat and exhibited minimal guarding, though he complained of intermittent abdominal pain. Sensory and motor function in his lower extremities was intact.

Radiographs of the lumbar spine showed acute nondisplaced fractures of the transverse processes at L-2, L-3, and L-4 on the patient's right side, and spina bifida occulta at L-5 with possible spondylolisthesis. Computed tomography (CT) scans revealed a 3-mm anterolisthesis of L-5 upon S-1 and confirmed the L-2, L-3 and L-4 fractures. The CT images (figure 1) also revealed a solitary right kidney. What would normally be the left kidney was fused with the right, producing a "pancake" kidney with double collecting systems and double ureters on the right (figure 2). When a kidney is located on the side opposite its ureter insertion into the bladder, the condition is termed crossed ectopia; this patient's condition was classified as crossed right renal ectopia with fusion. Ninety percent of crossed ectopic kidneys are fused to their ipsilateral mate (1).

This patient's kidney has an unusual shape and lies slightly anterior to the normal position, projecting under the right liver edge and down to approximately L-3. This location makes the kidney extremely vulnerable to injury. However, no contusion of the kidney was clearly visible, and no splenic or liver laceration was noted.

Because of the possibility of internal injuries, urinalysis and blood tests were done. Urinalysis showed large numbers of red blood cells. Blood tests revealed that hemoglobin was normal, and creatinine (0.9 mg/dL) and aspartate transaminase (117 U/L) were also in the normal range.

The patient was hospitalized for observation and given intravenous fluids and pain medication. He had an unremarkable hospital course and was discharged within 48 hours with a recommendation of limited ambulation as tolerated on the basis of pain.

He was able to return to moderate physical activity within 2 to 3 months of the injury. However, he was advised by his primary care physician, orthopedist, and urologist not to participate in collision sports such as ice hockey or acrobatic water-skiing because of the risk of damage to his single kidney. In the worst case, he could suffer acute renal failure that might necessitate hemodialysis or renal transplant. A flak jacket or rodeo vest was not deemed sufficient protection to make collision sports safe.

The patient sought a second opinion at our center, and after evaluating him, we concurred with the other physicians' recommendation that he not engage in collision sports. He wanted to be cleared to play with a protective vest, but we did not feel comfortable clearing him to play any collision sports.

The patient adapted to this activity modification with considerable difficulty. He struggled particularly with the requirement to avoid ice hockey, but eventually he took up other sports. As of a year later he had had no renal trauma.


Prevalence of renal ectopia. The prevalence of crossed fused renal ectopia in the general population is low: 0.5% to 0.013% (1 in 200 to 1 in 7,500). Most cases remain asymptomatic and are incidentally encountered on autopsy (2). In the rare instances when a single kidney is discovered in a young, otherwise healthy patient, the physician faces the problem of deciding whether to permit the patient to participate in sports.

Disqualification dilemmas. Sports participation issues for athletes may be highly emotionally charged. The safety of sports participation by individuals with a single kidney and other single organs has been debated in the sports medicine literature (3,4). The greatest risk to these patients is renal trauma. Some consensus guidelines on participation have been developed by the American Academy of Pediatrics (5) and other sports medicine groups. The standard recommendation is to advise athletes who have a solitary kidney not to participate in collision sports. Moeller (3) and Strauss and Townsend (2) reiterated this recommendation in recent articles in this journal. A few athletes with single organs have been cleared to play intercollegiate and high school collision sports after signing a waiver, but it is certainly more common to disqualify such an athlete.

Unfortunately, the incidence of renal trauma—and more specifically, of irreversible renal damage with subsequent renal failure—in sports is unknown. Sports-related injuries have been reported to account for 15% to 50% of renal injuries due to trauma (6). Case series that we found in the literature (involving patients with normal bilateral kidney except for one or two patients with anomalies) suggest percentages near the low end of that range. For example, Emmanuel et al (7) reported that 9 of the 59 cases of renal trauma at one children's hospital over a 15-year period were sports related. In a 9-year series of cases at another children's hospital, 4 of 78 patients who underwent renal surgery had been injured in football (8). And in a series of 65 pediatric patients treated for renal trauma over a 10-year period, 7 of the injuries were sports-related and another 6 were from sledding (9). Renal contusion was the most common urologic sports-related injury. But these reports supply no basis for estimating the risk of renal injury in particular sports.

In our case, the decision about participation was actually simpler than it probably is in most cases, because the location of the ectopic kidney under the right liver edge makes it extremely vulnerable to injury. The kidneys are normally protected from trauma by the ribs, fascia, spine, paravertebral muscles, and other structures. Given his kidney's location, our patient was very lucky to have escaped renal injury in his accident. This unusual case of crossed fused renal ectopia clearly contraindicates participation in collision sports.

The possibility of clearing the patient to participate while wearing a flak jacket or rodeo vest was considered, but such a vest would not have extended far enough inferiorly to protect the kidney. Because of the unusual location of the kidney, which clearly increased its vulnerability to injury, we would not have considered allowing him to sign a waiver to compete.

Although this case was relatively straightforward, disqualification from sports participation can be one of the most difficult decisions a sports medicine physician faces. An individualized approach to these patients is necessary, but it should be founded on some consensus guidelines regarding the risks of participation. Unfortunately, the risk of renal trauma in athletes with single kidneys or crossed fused renal ectopia has not been thoroughly researched, and this makes the decision more difficult. One measure that may help the physician decide may be to carefully interview the patient to ascertain the significance of sports participation to his or her well-being and career goals. This factor must be carefully weighed against the real, though difficult to quantify, risk of renal injury.

We did consider the importance to our patient of continued participation in collision sports. In view of the level of risk and because the patient was a recreational athlete, we felt that the benefits were not significant enough to justify allowing him to continue participating. The patient's father agreed strongly with our recommendation.

Dialogue Needed

Patients would benefit from an ongoing dialogue on this topic between sports medicine physicians and primary care and subspecialty physicians, including urologists and nephrologists. Such a dialogue would help to clarify some of the subtleties involved. We would encourage organizing an international forum on this issue, an approach that perhaps has not been tried previously.


  1. Bauer SB, Perlmutter AD, Retik AB: Anomalies of the upper urinary tract, in Walsh PC, Retik AB, Staney TA (eds): Campbell's Urology, ed 6. WB Saunders, Philadelphia, 1992, vol 2, pp 1347-1442
  2. Strauss RH, Townsend MC: The CT where nothing meant everything. Phys Sportsmed 1990;18(6):53-54
  3. Moeller J: Contraindications to athletic participation: spinal, systemic, dermatologic, paired-organ, and other issues. Phys Sportsmed 1996;24(9):57-75
  4. Wichmann S, Martin DR: Single-organ patients: balancing sports with safety. Phys Sportsmed 1992;19(2):176-182
  5. American Academy of Pediatrics Committee on Sports Medicine and Fitness: Medical conditions affecting sports participation. Pediatrics 1994;94(5):757-760
  6. Stricker PR, Puffer JC: Renal laceration: a skateboarder's symptoms are delayed. Phys Sportsmed 1993;21(8):59-68
  7. Emmanuel B, Weiss H, Golin B, et al: Renal trauma in children. J Trauma 1977;17(4):275-278
  8. Reid JS: Renal trauma in children: a ten-year review. Aust NZ J Surg 1973;42(3):260-266
  9. Persky L, Forsythe WE: Renal trauma in childhood. JAMA 1962;182(7):709-712

Dr Terrell and Dr Woods wish to dedicate this article to Dr Hough, who was a friend, mentor, and pioneer in sports medicine.

Dr Terrell is an assistant professor of family medicine/sports medicine and associate team physician at the University of Maryland in College Park, Maryland, and served as a physician at the Olympic Polyclinic at the 1996 Summer Games. Dr Woods is medical director at Arlington Group Sports Medicine in Harrisburg, Pennsylvania, and is a team physician for the Harrisburg Heat soccer team, for Dickson College in Carlisle, Pennsylvania, and for several high schools in the Harrisburg area. **Dr Hough died September 26, 1996. He was director of sports medicine and of the primary care sports medicine fellowship program at Michigan State University Sports Medicine in the Department of Family Practice at Michigan State in East Lansing. Dr Terrell and Dr Woods are members and Dr Hough was a fellow of the American College of Sports Medicine. Address correspondence to Tom Terrell, MD, Assistant Professor of Family Medicine/Sports Medicine, University of Maryland Sports Medicine at Kernan Hospital, 2200 Kernan Dr, Mansion House, Baltimore, MD 21201.



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