Acute renal failure: diagnosis

Laboratory and instrumental diagnostics of acute renal failure

In clinical blood analysis, moderate anemia and an increase in ESR can be observed. Anemia in the early days of anuria is usually of a relative nature. Due to hemodilution, does not reach a high degree and does not require correction. Changes in blood are characteristic of an exacerbation of urinary tract infection. In acute renal failure, there is a decrease in immunity, resulting in a tendency to develop infectious complications: pneumonia, suppuration of surgical wounds and skin catheter sites installed in the central veins, etc.

At the beginning of the oliguria period, the urine is dark, contains a lot of protein and cylinders, its relative density is reduced. During the restoration of diuresis, low relative density of urine, proteinuria, almost constant leukocyturia as a consequence of isolation of dead tubular cells and resorption of interstitial infiltrates, cylindruria, erythrocyturia remain.

In patients with a high risk of developing acute renal failure, including after major surgeries, it is necessary to monitor the creatinine content daily. Diagnosis of acute renal failure requires the determination of urea concentration, but this study can not be used in isolation, however this indicator characterizes the severity of catabolism. Even with suspected acute kidney failure, it is extremely important to monitor the patient's electrolytes and, above all, the amount of potassium. Decreased sodium levels indicate hyperhydration.

Biochemical monitoring of liver function is important. It is necessary to conduct a study of the coagulation system of blood. For acute renal failure characterized by a violation of microcirculation with the development of DIC syndrome.

ECG monitoring is needed, as this is a good way to control the potassium content in the heart muscle and possible complications from the heart. In 1/4 of patients with acute renal failure, arrhythmia can occur, up to cardiac arrest, increased muscle excitability, hyperreflexia.

A general urine test can reveal hematuria, proteinuria. With symptoms of an exacerbation of the urinary tract infection, a bacteriological analysis of the urine is necessary.

In the recovery period, the definition of GFR for endogenous creatinine is necessary.

Ultrasonography of the kidneys allows to determine the presence of obstruction, the size of the kidneys and the thickness of the parenchyma, the level of blood flow in the renal veins. With isotope renography, the asymmetry of the curves can be determined, which indicates obstruction of the urinary tract.

Chest radiography is needed. The condition of the lungs is essential. It is, first of all, the hyperhydration of the pulmonary tissue or nephrogenic edema, a specific clinical and radiological syndrome. At the same time to exclude pericarditis control the dynamics of the size of the heart. Hyperhydration of the lung tissue often serves as the main indication for urgent hemodialysis with ultrafiltration.

Correctly and in time, the established cause of acute renal failure will allow the patient to get out of the critical state faster, and also increase the likelihood of reversibility of functional disorders in the kidneys.

The diagnosis of acute renal failure is rarely difficult.

Differential diagnosis of acute renal failure

At the first stages of differential diagnosis, it is necessary to identify the possible cause of acute renal failure. It is important to differentiate the prerenal and renal form of renal failure, since the first form can quickly move into the second. It should also be distinguished postrenal form of acute renal failure, which developed against urinary tract obstruction, from renal renal insufficiency. To do this, excretory urography with high doses of contrast medium, isotope renography and ultrasound are used. Less commonly, retrograde ureteropyelography is used. Determining the size of the kidneys with ultrasound helps to distinguish acute renal failure from chronic renal failure, to identify or rule out a violation of urinary outflow through the urinary tract.

If the patient has anuria (oliguria) with severe anemia in the absence of a source of bleeding, then this indicates rather the chronic nature of the kidney syndrome. For acute renal failure, severe anemia is uncharacteristic.

It is important to find out the time of onset of anuria, the symptoms preceding it. Presence in the anamnesis of chronic renal diseases, the presence of anemia. Often, renal syndrome is the first manifestation of progressive renal disease with the development of chronic renal failure or a syndrome of decompensation of latent chronic renal failure. In these cases, it is always accompanied by anemia.

With the development of polyuria, the patient's condition quickly improves, despite the high concentration of nitrous metabolites: perhaps even a slight increase due to intense dehydration. Usually the development of polyuria to the maximum level takes several days, weeks. Delaying the onset of polyuria or diuresis at a level of 1.0-1.5 liters, unstable diuresis usually indicates poor health in general status, attachment of complications in the form of sepsis or other purulent processes, the presence of undiagnosed disease or trauma.

[1], [2], [3], [4], [5], [6], [7], [8]

Differential diagnosis of anuria and acute retention of urination

For differential diagnosis of true anuria and acute retention of urination, you should make sure that there is no urine in the bladder percussion, by ultrasound or by catheterization of the bladder. If a catheter inserted into the bladder releases less than 30 ml / h of urine, it is necessary to immediately determine the content of creatinine, urea and potassium in the blood.

[9], [10], [11]

Differential diagnosis of acute and chronic renal failure

Quickly to distinguish acute renal failure from chronic renal failure allows:

• study of general symptoms and history data;
• assessment of the appearance of urine;
• assessment of the dynamics of azotemia and diuresis;
• determination of the size of the kidneys (ultrasound, rhentgenogamma)

It is also necessary to establish the form of acute renal failure (prerenal, renal, postrenal).

[12], [13], [14], [15], [16], [17], [18],

Indications for consultation by other specialists

Given the poly-physiology of acute renal failure and the possibility of its occurrence in any clinical department, in the treatment of acute renal failure, joint actions of physicians of various specialties are absolutely essential.

All patients with suspected acute renal failure or an established diagnosis of "acute renal failure" are consulted and monitored by a nephrologist, as well as specialists in detoxification and intensive care. In the case of diagnosis of renal acute renal failure associated with impaired renal vasodilation, for example, with their thrombosis, it is necessary to involve a vascular surgeon in treatment. When developing the renal form of acute renal failure due to exogenous intoxication, toxicologists need help. With the postrenal form of acute renal failure, treatment and monitoring of the urologist is indicated.

The diagnosis of "acute renal failure"

The diagnosis "acute renal failure" in a concise form expresses the essence and completeness of the entire pathological process. In the main diagnosis should be reflected:

• the main disease that caused acute renal failure;
• leading syndromes;
• complications in the order of their severity.

In each case, it is necessary to determine the place of acute renal failure in the pathological process - whether it is a manifestation of the underlying disease or its complication. This has not only a formal and logical, but also an important meaning, since it characterizes the main pathological process.

The diagnosis of "acute renal failure" includes the definition:

• the main disease that caused acute renal failure;
• the form of acute renal failure (prerenal, postrenal or renal);
• stage of the disease (initial manifestations, oliguric, diuretic, or recovery).