Normally, serum creatinine is not affected by external factors like diet,
high catabolism and so on. On the condition that exogenous creatinine intake is
steady and internal generation is constant, concentration of serum creatinine
mostly depend on Glomerular filtrating rate. However, serum creatinine is not
equal to creatinine clearance rate which is more sensitive than the former one.
During renal function compensatory stage, creatinine clearance rate reduces but
serum creatinine is normal. Only if glomerular filtrating rate decreases to less
than 50%, serum creatinine will increase rapidly. Therefore, when serum
creatinine is obviously higher than normal condition, renal function has already
been damaged greatly. Because creatinine clearance rate is still related with
glomerular concentrated function, serum creatinine is a significant index to
reflect glomerular function once renal concentrated function in injured.
Normally, serum creatinine value of male should be in the range of 53 to
106gmol/L or 0.6 to 1.2rug/d1, and female value should be 44.2 to 97.2gmol/L or
0.5 to 1.1rug/d1. Because internal generation of creatinine is related with
muscle amount, serum creatinine value of people with well-developed muscle may
be high to 130gmol/L, while for very thin people, creatinine value may be only
26.5gmol/L. if patients serum creatinine is higher than 132gmol/L, their
glomerular function may have been greatly damaged. Besides emaciation, due to
the assimilation of increased glomerular filtrating rate and fetus, people who
are pregnant usually have a lower serum creatinine value than normal person.
Normally, very tiny creatinine is secreted by renal tubule, and some may
diffuse into enteric cavity. As for Uremia patients, renal tubule secretion
increases greatly, with 16% to 60% creatinine entering into enteric cavity.
Reproduction of streptococcus and enterococcus in upper gastrointestinal tract
can produce creatinine lyase which can degrade creatinine. For this reason, as
for some Uremia patients, concentration of serum creatinine and urine creatinine
as well as internal creatinine clearance rate may fluctuate.
