What is the Meaning of High Serum Creatinine and High Urea Nitrogen

When I communicate with kidney disease patients, their first question usually is: what does the high creatinine mean? Does it suggest my kidney have been damaged? 

The normal level of serum creatinine is less than 133.3umol/L (1.5mg/dl). In the normal condition, the production speed of creatinine in the body and the glomerular filtration speed are in balace. And when the glomerular filtration function declines, the serum creatinine will rise. But because our body has strong compensation and the serum creatinine won't rise obviously until the glomerular filtration rate decline to 1/3 of the normal level. So in the early stage of renal dysfunction, although the creatinine clearance rate drops, usually, the serum creatinine is normal. And just in the decompensation of renal insufficiency, the serum creatinine will rise apparently. But we can find the pathological change by the ECT. The low creatinine can be seen during normal pregnancy. It also can be presented in patients with muscular dystrophy diseases.

The clinical meaning of the urea nitrogen change:
Urea nitrogen is the end product of human protein metabolism. Liver is the main organ producing urea nitrogen and kidney is the main organ discharging it. The urea nitrogen production depends on the intake of protein from the diet, protein catabolism, and liver function. Usually, all of the urea nitrogen in the blood can be filtrated by the glomerulis and a small part will be reabsorbed by the renal tubules. So the amount of urea nitrogen in the blood also can judge our renal function, but not quite sensitive, because it will not rise until the renal function declines to 1/2 of the normal level which is 2.5-7.6mmol/L (7-20mg/dl).

The level of urea nitrogen is easily be affected by the diet, renal blood flow and protein decomposition. In general, the ratio of blood urea nitrogen to the serum creatinine is 10. The rising ratio suggests that most azotemia is caused by the prerenal factors, like gastrointestinal bleeding, cardiac insufficiency; the decreased ratio may suggest the pathological change of renal parenchyma itself, or the excessively insufficient intake of protein and serious hepatic insufficiency etc.

I hope the above information can help you to have a general understanding of your own illness condition. If you want to know more about kidney disease, you can consult our experts online. Wish you a good health!