Diagnosis of acute renal failure

The main criteria for acute renal failure:

• an increase in the creatinine content in the blood plasma of more than 0.1 mmol/l;
• decrease in diuresis to less than 0.5-1.0 ml/(kg h);
• acidosis and hyperkalemia.

In case of detection of azotemia without oliguria, the diagnosis of non-oliguric form of acute renal failure is valid. 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.
• Cardiovascular system:
  • arterial hypertension (for example, as a result of fluid retention in the body);
  • heart failure;
  • pericardial effusion;
  • heart rhythm disturbances (due to electrolyte imbalances).
• Gastrointestinal tract:
  • stress ulcers and erosions, including those accompanied by bleeding;
  • uremic gastroenteritis;
  • peritonitis;
  • hepatomegaly.
• CNS:
  • uremic encephalopathy;
  • cerebral edema;
  • micro- and macrohemorrhages.
• Hematopoietic system:
  • DIC syndrome;
  • anemia (in hemolytic uremic syndrome);
  • thrombocytopenia (in hemolytic uremic syndrome);
  • platelet function disorders;
  • leukocytosis (sometimes).
• Immune system:
  • decreased resistance to infections with an increased risk of infectious complications of any manipulations (artificial ventilation, catheterization of veins, urinary tract).

The duration of acute renal failure varies and depends on the general condition, the treatment being carried out and the course of the underlying pathological process.

Diagnosis of acute renal failure includes detection of oliguria, determination of the nature of oliguria (physiological or pathological) and diagnosis of the disease that caused the development of acute renal failure. It is necessary to carefully measure diuresis in a patient whose medical history allows one to suspect the development of acute renal failure, control clinical and biochemical parameters of blood and urine, as well as study the acid-base balance of the blood (ABB).

Determining the cause of acute renal failure

In children with oligoanuria, it is necessary to initially exclude malformations of the urinary system. For this purpose, ultrasound examination of the urinary system is recommended. This is the simplest, most accessible and non-invasive diagnostic method, which is used to exclude or confirm bilateral anomalies of the kidneys, ureters and various types of infra- and intravesical obstruction.

Doppler examination of renal blood flow is used for timely diagnosis of the initial stage of acute renal failure (i.e. renal ischemia).

Voiding cystourethrography is commonly used in boys to rule out posterior urethral valves and other types of urinary tract obstruction. It is sensitive and specific for detecting bladder outlet obstruction, but carries the risk of urinary tract infection.

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

If oliguria is detected, it is necessary to urgently determine the level of creatinine, urea nitrogen and potassium in the blood in order to confirm or exclude the diagnosis of acute renal failure. These studies are repeated daily. In organic acute renal failure, the concentration of creatinine in the plasma increases by 45-140 μmol/l per day. In functional oliguria, the creatinine level does not change or increases very slowly over several days.

Differential diagnosis of acute renal failure

For differential diagnostics of functional and organic disorders in the oliguric stage of acute renal failure, a diagnostic loading test (test with water loading) is carried out: 5% glucose solution and isotonic sodium chloride solution are administered intravenously for 1 hour in a ratio of 3:1 at the rate of 20 ml/kg, followed by a single administration of furosemide (2-3 mg/kg). In case of functional disorders after the test, diuresis exceeds 3 ml/(kg x h). In case of organic lesions of the nephron, oliguria persists even after normalization of systemic hemodynamics and blood gas composition against the background of treatment.

Various indices help differentiate prerenal from renal acute renal failure, but none has a therapeutic advantage or diagnostic reliability over fluid loading and diuresis response. The most useful urinary index is the renal failure index (RFI), which is calculated using the formula:

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

If the IPI value is less than 3, oliguria is prerenal, if it is greater than or equal to 3, it is renal. Although this index is quite sensitive in renal renal failure, it has no diagnostic value for premature infants, whose age at birth is less than 31 weeks of gestation.

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