Chronic kidney disease (CKD) is defined as a chronic decrease in glomerular filtration rate. In France, about 2 million people have CKD. Risk subjects were hypertensive, diabetic and aged 70 or more (where the frequency of CKD is higher among men than women; men of this age, the frequency of the IRC is 5-7 times higher than that among men 30 to 50 years).
As recommended by ANAES, renal function (that is to say, the glomerular filtration rate: GFR) must be assessed not only from creatinine, but also from the estimated or calculated clearance to using the Cockcroft and Gault:
Clearance = (140 – age) × weight × K / creatinine
Age is in years, weight in kg, creatinine in mmol / L, and K is about 1 in women and 1.25 in men.
Other formulas have been proposed to assess renal function (MDRD for example). The Cockcroft and Gault is the most simple.
However, it is not applicable to the child, the pregnant woman with very thin or very obese; it has not been well validated in patients over 75-80 years. Its performance can be improved by correcting the clearance according to the body surface area (calculated from the weight and size), that is to say in relation to the clearance of 1.73 m2.
The calculated clearance is often simpler and more reliable than the measured clearance (which requires a urine collection over a definite time and liable to errors). The calculated clearance is greater than the isolated serum creatinine which depends both of creatinine production by the muscle (and muscle mass) and its renal excretion.And creatinine 110 umol / L indicates a normal kidney function in a muscular man of 30 who weighs 80 kg and is 1.90 m (creatinine clearance> 100 mL / min per 1.73 m2), but a impaired renal function by half in a woman of 70, 55 kg for 1.60 m (clearance of about 40 mL / min per 1.73 m2).
We can offer a simple classification of kidney disease:
– Stage 1: chronic renal disease with clearance greater than 90 mL / min per 1.73 m2 (normal GFR);
– Stage 2: chronic kidney disease with clearance between 60 and 89 (impaired renal function in young adults and middle-aged, but more difficult to assess in the elderly due to a decrease in “physiological” GFR with the age, uneven from one topic to another);
– Stage 3: clearance between 30 and 59 (chronic renal insuffi moderate growth);
– Stage 4: clearance 15 to 29 (severe renal impairment);
– Stage 5: clearance below 15 (renal failure very advanced or terminal, requiring renal replacement therapy).
Determine the cause:
Make sure first that it is not an acute renal failure (where the kidneys are of normal size or increased, normal blood pressure, etc.). Also ensure that the IRC has been temporarily aggravated by dehydration, excessive fall in blood pressure, infection, medication, etc. Remove this aggravating factor to return to the ground state.
Determine the cause of the IRC because it is curable or IRC upgradeable. In addition to clinical examination, what simple explorations ask? Measure blood pressure, consider fresh urine using a dipstick (proteinuria, hematuria or infection), estimate the plasma electrolytes, including calcium, and request an ultrasound of the kidneys and urinary tract.
In a second step, according to the results, it may be necessary to seek the advice of a specialist and do other explorations.
So do not ignore such a prostatic obstruction or other cause of chronic distension of the urinary tract, severe hypertension, hypercalcemia, prolonged use of a potentially nephrotoxic drug (such as lithium) proliferative glomerulonephritis Extracapillary or croissants, result of vasculitis successive crops, constituting “slyly” IRC, always accompanied by abundant microscopic hematuria or gross.
Slow the progression:
In addition to the clean treatment of underlying renal disease, today there are two ways:
– Strictly control blood pressure; there is proteinuria 1 g / 24 hours, bring the voltage below 125/75 mmHg with proper treatment.
If proteinuria is less abundant, aim below 130/80. In patients 70 years and older, diabetic or in the subject “vascular” take precautions to avoid excessive orthostatic hypotension;
– Minimize proteinuria (<1 or 0.50 g / 24 hours). Therefore the angiotensin converting enzyme inhibitors or antagonists of angiotensin II are recommended.
Cardiovascular complications are at the forefront, leading causes of death; hence the importance of antihypertensive treatment, smoking cessation, equilibration of diabetes mellitus, correction of hypercholesterolemia and anemia. IRC is in itself a cardiovascular risk factor, independent of the preceding factors.
Calcium phosphate abnormalities of the IRC (hyperphosphatemia and hypocalcemia) should be prevented, often using calcium carbonate, sometimes a derivative of vitamin D. The purpose is to prevent secondary hyperparathyroidism and bone complications IRC.
The administration of erythropoietin subcutaneously in combination with martial supplements, corrects anemia of CKD and is indicated when the blood hemoglobin is less than 10.5-11 g / dL; it results in an improvement of the adaptation to stress and a better quality of life.
Vaccination against hepatitis B remains useful in renal impairment to prevent infection; think about performing early in the evolution and control plasma levels of anti-HBs.
Avoid the adverse effects of many drugs, adapting doses as recommended by the Vidal dictionary or database as ICAR. For any new drug as with any medication which we know or have forgotten, the precautions, consult the recommendations. Toxicity may result from renal elimination default but also increased tissue sensitivity; it can affect the kidney or other organs. Assess kidney function well to avoid these toxic accidents.
The injection of an iodinated radiographic contrast material carries the risk of worsening of the IRC; the risk is higher in the diabetic IRC. Take the following precautions to ensure that there is no alternative; suspend diuretics and metformin 24-48 hours earlier; it is recommended to administer acetylcysteine (Mucomyst®) 200 mg / x3 / day the day before and the day of the exam; use the most limited amount can be a product of low osmolality less nephrotoxic; especially administer isotonic saline solution intravenously 5-12 hours before, during and 5-12 hours after injection (about 1 000 to 1 500 mL total as tolerated).
Finally, it is necessary to adapt the diet at the IRC: restrict foods rich in K, moderate intake of NaCl, correct acidosis, restricting protein intake (about 0.8 g / kg / d), while maintaining adequate caloric intake (about 35 kcal / kg / day), and especially by avoiding malnutrition.
To achieve these objectives, joint and well synchronized monitoring by the general practitioner and nephrologist is necessary (see the recommendations of the ANAES).
Prepare the patient for renal replacement:
The progression of CKD is more or less rapidly according kidney disease, according to the patients and the quality of follow-up; this advanced stage (creatinine clearance ≤ 15-20 mL / min) can be reached in a few months or 20 to 30 years, sometimes forever if the previous therapeutic measures are implemented and effective. IRC stable for long, or very slowly progressive, are commonly observed.
The phase information of the patient and his entourage is required when the IRC becomes important to calmly prepare the renal replacement therapy: periodic dialysis and / or kidney transplantation. Treatment modalities should be explained to guide the choice of the patient. Autonomous processing modes, at home (peritoneal or hemodialysis) or a unit autodialysis, should be preferred whenever possible. Arteriovenous fistula for hemodialysis must be created months before the terminal stage; remember that in this perspective the veins of a forearm must be protected from any puncture. The establishment of the peritoneal dialysis catheter must also be well planned.Similarly, information on the kidney transplant (from a living donor or a deceased subject) and the necessary explorations must be integrated into the preparation for replacement therapy.
The quality of adaptation replacement therapy, prevention of cardiovascular complications and life expectancy depends largely on the quality of care provided before dialysis or transplantation.