Acute renal failure: causes and pathogenesis

The causes of acute renal failure are not completely clear, however, four main mechanisms of its development are noted:

• tubular obstruction;
• interstitial edema and passive reverse current of the glomerular filtrate at the level of the tubules;
• hemodynamic disorder of the kidney;
• disseminated intravascular coagulation.

On a large statistical material has now been proved: the morphological basis of acute renal failure is the lesion of the tubular apparatus mainly in the form of nephrothelial necrosis with or without damage to the basal membrane; with indistinctly defined lesions of glomeruli. Some foreign authors use the Russian-language term "acute canal necrosis" as a synonym for "acute renal failure". Morphological changes, as a rule, are reversible, therefore, the clinical and biochemical symptom complex is also reversible. Nevertheless, in a few cases, with severe endotoxic (less exotoxic) effects, it is possible to develop bilateral total or subtotal cortical necrosis, differing in morphological and functional irreversibility.

There are several stages of development of acute renal failure:

• the initial stage (the effects of the damaging factor);
• stage oliguria or anuria (an increase in the clinical signs of the disease). The period of kidney failure is characterized by the instability of diuresis, the condition periodically shifts from anuria to oliguria and vice versa, so this period is called oligoanuric;
• diuretic stage (the beginning of the resolution of the disease);
• stage of recovery.

The action of damaging factors causes damage to the tubular apparatus and, above all, the tubular epithelium in the form of necrobiotic and dystrophic processes, which leads to the development of the oligoanuric stage. Since the damage of the tubular apparatus, the anuria acquires a stable character. Moreover, for the detailed acute renal failure, one more factor is characteristic: tubular obstruction, resulting from the destruction of nephrothelia, its congestion with pigment slags. If the basal membrane is preserved and functions as a scaffold, then in parallel with the necrosis of nephrothelia, the regeneration process develops. Regeneration of the tubule is possible only with the preservation of the integrity of the nephron. It is established that the newly formed epithelium is initially functionally inferior, and only by the 10th day from the onset of the disease signs of restoration of its enzymatic activity appear, which clinically corresponds to the early diuretic stage.

In patients with surgical profile who are in inpatient treatment, the causes of acute renal failure can be divided into two groups:

• progression of the underlying disease or development of complications;
• complications of drug, infusion therapy or blood transfusion complications.

In patients who undergo surgery, in the postoperative period, the definition of the etiological factors of acute renal failure represents a significant diagnostic difficulty. These factors are directly related to the trauma of surgery and complications of the postoperative period, among which the most likely are peritonitis, destructive pancreatitis, intestinal obstruction, etc. In this case, it is necessary to take into account the significant changes in some of the body's reactions characterizing the purulent-inflammatory process. Fever with purulent-septic process often softens, chills are not always accompanied by a corresponding increase in body temperature, especially in patients with hyperhydration. Development of acute renal failure in surgical patients who underwent surgery. Complicates the diagnosis of purulent complications from the abdominal organs. A significant improvement in the patient's condition after hemodialysis testifies to the absence of complications.

Anesthetic management can lead to toxic and toxic-allergic effects on the kidneys. For example, there is evidence of halothane nephrotoxicity. Often in these cases anuria is preceded by arterial hypertension during the operation or on the first day of the postoperative period; a prolonged exit from a narcotic dream; prolongation of mechanical ventilation.

Postural acute renal failure is most often due to acute obstruction of the urinary tract.

• Obstruction of ureters:
  • stone;
  • blood clots;
  • necrotic papillitis.
• Compression of the ureters:
  • a tumor;
  • retroperitoneal fibrosis.
• Bladder infection:
  • stones;
  • a tumor;
  • schistosomiasis
  • inflammatory obstruction of the neck of the bladder;
  • adenoma of the prostate;
  • disturbances of innervation of the bladder (spinal cord injury, diabetic neuropathy).
• Stricture of the urethra.

In acute anuria, accompanied by pain, it is necessary to exclude urolithiasis. Even with unilateral obturation of the ureter with severe pain (renal colic), it is possible to stop urinating with a healthy kidney (reflex anuria).

With necrotic papillitis (necrosis of the renal papillae), both postrenal and renal acute renal failure develop. More common postrenal acute renal failure due to ureteral obstruction by necrotic papillae and blood clots in diabetes mellitus, analgesic or alcoholic nephropathy. The course of pogrenal acute renal failure with necrotic papillitis is reversible. At the same time, renal acute renal failure caused by acute total necrotic papillitis complicating purulent pyelonephritis often turns into irreversible renal failure.

Perhaps the development of acute renal failure and with TUR syndrome, complicated TUR prostate for adenoma (occurs in about 1% of cases). TUR-syndrome occurs in 30-40 minutes from the beginning of resection of the prostate and is characterized by increased blood pressure, bradycardia, increased bleeding from the wound; many patients have excitement and convulsions, possibly the development of coma. In the early postoperative period, hypertension is replaced by hypotension, which is poorly amenable to correction; develops oliguria, anuria. By the end of the day, jaundice appears. During the operation, it is necessary to constantly or fractionally rinse the operating wound and bladder with distilled water at a pressure of 50-60 cm of water. Since the pressure in the venous vessels of the operation area does not exceed 40 cm of water, the irrigation fluid enters the venous vessels. The possibility of fluid absorption through paravezic space during the dissection of the glandular capsule is proved. The rate of absorption of irrigation fluid from the operation area is 20-61 ml / min. Within an hour, 300 to 8000 ml of liquid can be absorbed. When using distilled water, the hypoosmolarity of the blood plasma develops with subsequent intravascular hemolysis of erythrocytes, which was considered the main cause of TUR syndrome development. However, subsequently, using non-hemolytic solutions, TUR syndrome was completely avoided and acute renal failure failed, despite the absence of hemolysis. In this case, all researchers note hyponatremia, hypocalcemia and general hyperhydration. According to the literature, the following causes of acute renal failure are likely:

• mechanical blockade of renal tubules by deposition of blood pigment;
• the appearance of nephrotoxicity in the action of electrical current on the tissue;
• disturbance of blood circulation in the kidneys.

In TUR-syndrome, acute renal failure occurs in 10% of patients, and in 20% of cases leads to death.

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