Types of chronic renal failure

Classification of chronic renal failure

There are many different classifications of renal dysfunction developed by domestic and foreign authors and based on different principles. The latter are: the value of glomerular filtration, the concentration of serum creatinine, the dysfunction of the tubules and the staging of clinical symptoms. In our country, there is no single generally accepted classification of renal dysfunction in children.

According to the degree of involvement of various parts of the nephron in the pathological process, the following are distinguished:

• partial chronic renal failure - isolated or combined impairment of renal function;
• total chronic renal failure - a complete symptom complex of homeostatic disorders associated with the inclusion of all elements of the nephron in the pathological process;
• terminal chronic renal failure - the final stage of the disease, in which most of the nephrons do not function and the compensatory capacity of the kidneys is exhausted. The SCF at this stage is less than 15 ml/min.

It is important to consider that the clinical signs of chronic renal failure largely depend on the underlying disease that led to its development. The progression of the disease with damage to the glomerular apparatus and predominant involvement of the tubulointerstitium in the process proceeds differently. From this standpoint, the classification of renal dysfunction in children proposed by M.S. Ignatova et al. (1986), which takes into account the dominant substrate of the lesion, is of great interest.

Classification of renal dysfunctions

Degree of violations	Glomerular apparatus	Canalicular apparatus
PNO	There are no changes in functions	There are no changes in functions
Mon I	Disruption of circadian rhythm of filtration	Disruption of the circadian rhythm of tubular functions
PN IIa	Compensated and subcompensated filtration disorders	Compensated and subcompensated disorders of tubular functions
PN IIb-CRN I	Decompensated filtration and tubular function disorders	Decompensated tubular function and filtration disorders
PN II-CRN III	Total with homeostasis disorder	Most often partial with homeostasis disorder
CRF III-terminal renal failure	Terminal total	Terminal, often total

• RF - renal failure;
• CRF - chronic renal failure.

In addition, one can highlight the classification of stages of chronic renal failure proposed by V.I. Naumova (1991).

In the compensated (first) stage, only a decrease in the reserve capacity of the kidneys is noted without a violation of homeostatic constants.

The subcompensated (second) stage is characterized by intermittent hyperazotemia, increased creatinine concentration and impaired partial renal function.

In the decompensated (third) stage, signs of chronic renal failure are expressed. The terminal (fourth) stage is the final stage of chronic renal failure (uremia). According to the clinical classification, there are 3 stages of chronic renal failure:

• initial (SCF = 40-60 ml/min);
• conservative (SCF = 15-40 ml/min);
• terminal (GFR < 1-015 ml/min).

In 2002, the European Association of Nephrologists developed a unified classification of chronic kidney disease, which includes chronic renal failure.

Chronic kidney disease occurs as a result of a long-term (>3 months) course of any kidney disease. Its classification is based on the value of the SCF, calculated by formulas and independent of the collection of daily urine. There are 5 stages of chronic kidney disease.

Classification of chronic kidney disease (NKF/KD0QI, 2002)

Stage	Symptoms	Glomerular filtration rate, ml/min
I	Signs of nephropathy (kidney damage and/or microalbuminuria), normal or increased SCF	290
II	Signs of nephropathy (kidney damage and/or microalbuminuria), moderate decrease in SCF	60-89
III	Moderate decrease in SCF	30-59
IV	Severe decrease in SCF	15-29
V	Terminal renal failure	<15

More accurate values of creatinine clearance for determining SCF in children are provided by the Schwartz formula (1976):

Creatinine clearance (ml/min) = K x height (cm)/serum creatinine (mg/dl).

There is another formula:

Creatinine clearance = K x height (cm) x 80/serum creatinine (μmol/L), where K = 0.55 for all children aged 2 to 12 years and for girls aged 13 to 18 years. For boys aged 13 to 18 years, K = 0.77.

For children, a specific assessment of renal function is necessary, since the normal value of SCF varies depending on age, gender, physical characteristics and increases as the child matures, approaching the average adult values by the age of about 2 years.

Normal glomerular filtration rate in children and adolescents

Age	Glomerular filtration rate, ml/min
1st week	41115
2-8 weeks	66+25
Older than 8 weeks	96122
2-12 years	133127
13-21 years (men)	140130
13-21 years (women)	126122