oliguria/anuria. Physical examination reveals irritability, pallor, and petechiae. Dehydration is often present; however some children have volume overload. Hypertension may be due to volume overload and/or renal injury. Central nervous system (CNS) involvement, including seizures, occurs in up to 25% of cases. Other potential organ involvement includes pancreatitis, cardiac dysfunction, and colonic perforation.
Children without evidence of a diarrheal prodrome mayhave a similar microangiopathic syndrome, identified asthrombotic thrombocytopenic purpura (TTP). Childrenwith TTP typically have predominant CNS symptoms butmay also have significant renal disease. Recurrent episodes are common. Because CNS involvement is also seen in HUS, TTP can be difficult to distinguish from HUS in some cases. Deficiencies of ADAMTS13, a von Willebrand factor-cleaving protease, have been identified in childrenaffected with TTP.
Common laboratory findings in HUS are listed in Table 164-1. Peripheral blood smear reveals evidence of microangiopathic hemolysis. Coombs test is negative. The diarrhea and presence of toxin-producing E. coli may have resolved by the time HUS is diagnosed.
Therapy for HUS is supportive and includes volume repletion, control of hypertension, and managing complications of renal insufficiency, including dialysis when indicated. Red blood cell transfusions are provided as needed. Platelet transfusions should be avoided because they may add to the thrombotic microangiopathy and are indicated only by active hemorrhage or in anticipation of a procedure. Antibiotics and antidiarrheal agents may increase the risk of developing HUS. Early hydration during the diarrheal phase may lessen the severity of renal insufficiency. Most children (>95%) with D+HUS survive the acute phase and recover normal renal function, although some may have evidence of long-term morbidity.
Acute kidney injury (AKI), formerly termed acute renal failure, refers to an abrupt decrease in glomerular filtration rate (GFR) and tubular function. This may lead to decreased excretion of waste products (e.g., urea) and a disturbance in fluid and electrolyte homeostasis. Early recognition and management of AKI are crucial.
AKI may be oliguric (<1 mL/kg/h in neonates and infants, <0.5 mL/kg/h in children) or nonoliguric, which is more difficult to recognize. Although urine output in nonoliguric AKI is normal or polyuric, electrolyte disturbances and uremia may become significant. The major causes of AKI may be divided into prerenal (renal hypoperfusion), intrinsic renal (tubular, glomerular, or vascular injury), and postrenal (urinary tract obstruction) categories (Table 165-1). In many cases the cause of AKI is multifactorial.
Prerenal azotemia is most commonly due to dehydration but may be secondary to other mechanisms of glomerular hypoperfusion. Tubular injury encompasses the most common causes of intrinsic AKI in children. Tubular injury may occur fromhypoxia-ischemia (acute tubular necrosis), infection (sepsis),nephrotoxic agents (medications, contrast, myoglobin) and inflammation (interstitial nephritis). Postrenal AKI may be due to either structural or functional urinary tract obstruction.
Available @ StudentConsult.com