Click here to view next page of this article


Diagnosis of Acute Renal Failure

Although acute renal failure (ARF) is relatively uncommon, its mortality rate is potentially so high that it is important to recognize this condition in children. Rapid deterioration of renal function is caused by numerous insults and results in typical findings, including extracellular volume expansion, hyperkalemia,


ARF represents the rapidly progressive (within several hours or days) cessation of renal function, which results in the inability of the kidney to control body homeostasis, manifesting in retention of nitrogenous waste products (azotemia) and fluid and electrolyte imbalance. On the basis of pathophysiologic process, ARF has been divided broadly into three diagnostic categories: prerenal, intrarenal (organic-intrinsic).


Prerenal failure is the most common form of ARF in children. The main process in the development of prerenal failure is hypoperfusion of the kidney, secondary

Acute tubular necrosis (ATN) is the most common cause of intrinsic renal failure. It is associated with necrosis of the tubular epithelium following hypoxic or nephrotoxic injury. Various substances, including ethylene glycol, heavy metals, hydrocarbons, and certain antibiotics, including cephalosporins, aminoglycosides, sulfonamides, methicillin, and colistin, are potent nephrotoxins. Aminoglycoside-induced acute renal failure occurs typically 5 days after drug administration and represents a dose-dependent phenomenon.

Radiologic contrast material of the ionic type can cause ARF, usually within 24 hours after exposure, especially in individuals who are dehydrated.

Postrenal failure is a less frequent cause of ARF in children. It presents as an abrupt decline in glomerular filtration rate (GFR) secondary to lower tract obstruction or bilateral upper tract obstructions, unless the patient has a single kidney. Obstruction can be secondary to structural, congenital, or acquired anomalies.


Prerenal dysfunction can lead to development of renal failure and is characterized by a decline in renal blood flow (RBF), GFR, and urine flow. After an acute reduction in effective intravascular volume, compensatory mechanisms of both the organism and the kidney will operate to counteract the volume loss and restore renal perfusion. Central activation of several neural and humoral responses occurs.


The patient who has prerenal failure will evidence the signs and symptoms of decreased effective blood volume or perfusion. There may be a history of vomiting, diarrhea, recent febrile illness, surgery, imbalance between input and output, heart problems, thirst, weight loss, or decrease in urine output.


Clearly, the pediatrician must be alert to the possibility of renal obstruction. When a child presents with the signs of azotemia and a sudden decrease in urine output, the history and physical examination can help determine the location and treatment.