Chapter 13. Disorders of the Kidneys

This chapter reviews relevant aspects of renal disease that have implications for sport participation by adolescents, including solitary kidney, hypertension, hyponatremia, proteinuria, hematuria, exercise-related acute renal failure, and chronic/end-stage renal disease (ESRD).1 The effects of creatine and protein supplementation, including renal effects, are reviewed in Chapter 6.2,3

Definition and Epidemiology

Solitary kidney refers to the occurrence of one kidney instead of the normal situation with two kidneys. Approximately 1 in 1500 children and adolescents have a solitary kidney.4 The concern is whether sports activity should be avoided or limited for fear of injuring the one kidney the child or teen has and then having no kidney at all.

Pathogenesis

Solitary kidney may result from congenital or acquired causes (Table 13-1). Congenital causes include renal fusion anomalies. Acquired causes include the removal of a kidney because of malignancy or trauma.

Renal trauma from sports is fortunately an unusual condition and most of these are seen as a result of blunt trauma in contact/collision sports.4 Recreational bicycle riding is the most common cause of sports-related kidney injury in children, sometimes leading to major renal injury; team contact sport activity is an unusual cause of major renal injury.5 Also, the incidence of renal trauma from motor vehicle accidents is significantly higher in adolescents than renal trauma from sports activities.6

Clinical Presentation

Solitary kidney is typically asymptomatic and often is not known. Renal anomalies may be suspected in infants, if there is only one umbilical artery or other anomalies are present, such as congenital heart disease or multiple anomalies (such as imperforate anus, scoliosis, external ear defects, and others). Clinically, there are no specific manifestations of a solitary functioning kidney including renal agenesis. However, because of the generalized use of prenatal ultrasound, the diagnosis is commonly made prenatally and confirmed after delivery by repeated ultrasonography or nuclear renal scan. Unilateral renal agenesis in otherwise healthy individuals is compatible with normal longevity. Hypertension, proteinuria, hyperuricemia, focal segmental sclerosis, and decreased glomerular filteration rate (GFR) developing in individuals with a solitary functioning kidney are well documented in the literature. Renal hyperfiltration has been implicated as the cause of these abnormalities.

Diagnostic Studies

A renal sonogram may be done in cases of suspected renal anomalies or if an enlarged kidney is palpated.

More advance studies are undertaken in consultation with nephrologists as indicated based on initial clinical evaluation Box 13-1.