20 - Pediatric Genitourinary and Renal Disorders

The full complement of nephrons is present at birth, although newborn nephrons are heterogeneous in glomerular size and proximal tubule length. Anatomy and function mature postnatally. Although fetal urine is excreted into the bladder by 10 to 11 weeks of gestation, the ability to conserve and excrete sodium, concentrate urine, and reabsorb substrates such as glucose evolves to maturity over the first 2 years of life. In utero, the glomerular filtration rate (GFR) is minimal secondary to placental function; at birth, the GFR is 10% of adult values and matures by 12 to 24 months of age. Therefore, an increase in an infant’s creatinine to “normal” adult ranges can indicate pathology. • Children often cannot differentiate between abdominal pain and groin pain—a complete physical examination is therefore necessary. • The pathophysiology, clinical findings, and treatment of paraphimosis, testicular torsion, and priapism are similar in both the pediatric and adult population. They are emergencies that require immediate intervention. • The most common cause of acute renal failure in children is hemolytic-uremic syndrome. • Poststreptococcal glomerulonephritis is the most common cause of acute glomerulonephritis. IgA nephropathy is the most commonly diagnosed cause of glomerulonephritis in adolescents. • One third of patients with Henoch-Schönlein purpura have renal involvement. This disorder is the most common form of vasculitis in childhood and is usually characterized by the triad of abdominal pain, arthritis, and purpura. KEY POINTS