Diagnosis of acute renal failure

The main criteria for acute renal failure are:

• increase of creatinine in the blood plasma more than 0.1 mmol / l;
• decrease diuresis less than 0,5-1,0 ml / (kghh);
• acidosis and hyperkalemia.

In the case of detection of azotemia without oliguria, the diagnosis of neoliguric form of acute renal failure is authorized. In newborns with acute renal failure, hyperkalemia and metabolic acidosis may be absent.

Complications from other organ systems in acute renal failure

• Respiratory system:
  • "Shock lung" (respiratory distress syndrome);
  • pulmonary edema;
  • pneumonia;
  • hydrothorax.
• The cardiovascular system:
  • Arterial hypertension (for example, as a result of fluid retention in the body);
  • heart failure;
  • effusion in the pericardial cavity;
  • heart rhythm disturbances (due to electrolyte disorders).
• Gastrointestinal tract:
  • stress ulcers and erosions, including those accompanied by bleeding;
  • uremic gastroenteritis;
  • peritonitis;
  • hepatomegaly.
• CNS:
  • uremic encephalopathy;
  • edema of the brain;
  • micro- and macroblood.
• The system of hematopoiesis:
  • DIC-syndrome;
  • anemia (with hemolytic-uremic syndrome);
  • thrombocytopenia (with hemolytic-uremic syndrome);
  • impaired platelet function;
  • leukocytosis (sometimes).
• The immune system:
  • decrease in resistance to infections with an increased risk of infectious complications of any manipulation (IVL, catheterization of veins, urinary tract).

The duration of acute renal failure is different, depends on the general condition, the treatment and the course of the underlying pathological process.

Diagnosis of acute renal failure includes the identification of oligoanuria, the character of oliguria (physiological or pathological) and the diagnosis of the disease that caused the development of acute renal failure. It is necessary to carefully measure diuresis in a patient whose history allows you to suspect the development of acute renal failure, control of clinical and biochemical parameters of blood and urine, as well as the study of the acid-base state of the blood (CBS).

Determination of the cause of acute renal failure

In children with oligoanuria, it is first necessary to exclude the developmental defects of the urinary system. For this purpose, an ultrasound of the urinary system is recommended. This is the most simple, affordable and non-invasive method of diagnosis, which is used to exclude or confirm bilateral anomalies of the kidneys, ureters and various types of infra- and intravesical obstruction.

Doppler study of renal blood flow is used to timely diagnose the initial stage of acute renal failure (i.e., renal ischemia).

Mictic cystourethrography is usually used in boys to exclude the presence of the valve of the posterior urethra and other types of obstruction of the urinary tract. The method is sensitive and specific for the detection of infravesical obstruction, but carries the risk of infection of the urinary tract.

After exclusion of postrenal renal failure in a child with oligoanuria, it is necessary to establish the causes of renal or prerenal acute renal failure.

In detecting oligoanuria, an urgent determination of the level of creatinine, urea nitrogen and potassium in the blood is necessary in order to confirm or exclude the diagnosis of acute renal failure. These studies are repeated daily. With organic acute renal failure, the creatinine concentration in the plasma rises by 45-140 μmol / l per day. With functional oliguria, the level of creatinine does not change or rises very slowly for several days.

Differential diagnosis of acute renal failure

For differential diagnosis of functional and organic disorders in the oliguric stage of acute renal failure, a diagnostic loading test (a test with a water load) is carried out: for 1 hour, 5% glucose solution and isotonic sodium chloride solution is injected intravenously in a ratio of 3: 1 from the calculation of 20 ml / kg followed by a single administration of furosemide (2-3 mg / kg). With functional disorders after a sample diuresis exceeds 3 ml / (kghh). With organic lesions of the nephron, oliguria remains after normalization against the background of treatment of systemic hemodynamics and gas composition of the blood.

Different indices help differentiate prerenal acute renal failure from renal failure, but none of them has a therapeutic advantage, as well as diagnostic reliability in comparison with fluid loading and diuresis response. The most useful urinary index is the index of renal insufficiency (IPN), which is calculated by the formula:

IPN = U _Na : U _Cr : P _Cr, where U _Na is the concentration of sodium in the urine; U _Cr - concentration of creatinine in urine; P _Cr is the concentration of creatinine in the plasma.

With an IPI value of less than 3 oliguria prerenal, more or equal to 3 - renal. Although this index is quite sensitive in renal renal insufficiency, it is not of diagnostic value for preterm infants whose age is less than 31 weeks of gestation at birth.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]