To estimate the stage renal function by RIFLE criteria one should know the
baseline creatinine level. This may be difficult when baseline laboratory is not
available. The creatinine level and GFR can be estimated using the “modification
of diet in renal disease” (MDRD) formula which normalizes the GFR to the body
surface area based on age, sex and race. Unfortunately, this formula can only
estimate the baseline creatinine in children over 12 years of age. One should
remember that estimations using the MDRD formula are not accurate when the
patient is not in a steady state of creatinine balance such as the case of infants
and patients with restricted creatinine secretion due to chemotherapy, cimetidine
or AIDS therapy. [17]
Causes of renal failure
In developed countries, only 10% of cases of ARF are due to primary kidney
disease. The majority are secondary to cardiac surgery for congenital heart
disease, sepsis and nephrotoxic medications. [6] [14][15]
Years ago, hemolytic uremic syndrome was the main cause of ARF in children of
developed countries. This is still the case in developing countries.
a) Pre-renal failure
In pre-renal failure, the kidney attempts to retain as much sodium and
water as possible to increase the intravascular volume. Usually, this effect
is mediated by the renin-angiotensin-aldosterone axis. Non-steroidal anti-
inflammatory medications, which inhibit this physiologic response, cause
renal insufficiency during states of hypoperfusion.
During renovascular disease and renal hypoperfusion states, the release
of angiotensin causes vasoconstriction of the efferent arteriole, this way
providing enough pressure for transglomerular filtration. The
administration of ACE-inhibitors in patients with renovascular disease is