Oliguria is a pathological condition characterized by a decrease in urine output (less than 400 ml of urine in 24 hours). Causes can range from insufficient fluid intake or long-term medication to severe kidney disease or shock. Oliguria indicates a decrease in the glomerular filtration rate, i.e. there is a violation of the excretion of products of nitrogen metabolism, which leads to their accumulation in the body. Correction is carried out by treating the underlying disease.
Classification
In clinical practice, it is customary to divide oliguria into 3 large groups:
- Prerenal . The most common variant of oliguria. The drop in diuresis is associated with a deterioration in renal perfusion as a result of bleeding, profuse recurrent vomiting, profuse diarrhea, etc.
- Renal. Oliguria is caused by kidney diseases: glomerulonephritis, acute tubular necrosis, interstitial nephritis, etc.
- Postrenal. A small volume of diuresis is associated with obstruction in the urinary tract due to urolithiasis, ureteral stenosis.
Causes of oliguria
prerenal oliguria
It is the most common type of this pathology. Urine is formed by filtration of blood in the kidneys, so any factors that cause a decrease in renal blood flow can cause oliguria. The mechanisms may be different: a decrease in the level of extracellular fluid, a decrease in the volume of circulating blood (hypovolemia), a drop in total peripheral vascular resistance, or a pronounced narrowing of the lumen of the renal artery.
A decrease in the volume of diuresis occurs acutely, with a gross violation of the blood supply to the kidneys, it can reach a complete absence of urination (anuria). With timely treatment, the vast majority of patients can achieve normalization of diuresis. Prerenal oliguria develops in the following cases:
- Severe fluid loss : through the gastrointestinal tract (vomiting, diarrhea), through the skin (extensive burns, profuse sweating with hectic fever), massive bleeding. Oliguria can occur with excessive administration of diuretic drugs.
- Cardiac diseases with a decrease in ejection fraction : myocardial infarction, congestive heart failure, cardiomyopathies, congenital or acquired heart defects, constrictive pericarditis.
- Decreased vascular tone : sepsis, shock conditions (cardiogenic, traumatic shock).
- Renal vascular obstruction: renal artery stenosis, fibromuscular dysplasia, thrombotic microangiopathy (hemolytic-uremic syndrome, thrombotic thrombocytopenic purpura, DIC).
Oliguria
Renal oliguria
This form is based on lesions of the kidney parenchyma, accompanied by a sharp inhibition of its functional state. This can occur due to primary kidney disease, kidney damage from systemic inflammatory pathologies, diseases of other organs, or the ingestion of nephrotoxic substances in the human body.
The degree of oliguria depends on the severity of the disease. Normalization of diuresis may occur at the beginning of treatment, but in some cases the oliguria regresses very slowly, after several months of continuous specific therapy. The causes of renal oliguria are given below:
- Acute or chronic glomerulonephritis.
- Acute pyelonephritis.
- Hydronephrosis.
- Polycystic kidney disease.
- Acute interstitial nephritis.
- Acute tubular necrosis.
- Nephropathy in rheumatic diseases: systemic lupus erythematosus, systemic scleroderma, systemic vasculitis.
- Muscle tissue breakdown: rhabdomyolysis, cardiorenal syndrome.
- Taking nephrotoxic drugs: antibiotics from the group of aminoglycosides (gentamicin, neomycin), non-steroidal anti-inflammatory drugs (analgin, diclofenac), cytostatics (cyclosporine).
- Introduction of X-ray contrast agents.
- Transfusion of incompatible blood by AVI Rh system.
- Poisoning with salts of heavy metals: mercury, lead.
Postrenal oliguria
This type of oliguria occurs in case of urinary tract obstruction, i.e. when there is a significant obstruction to the outflow of urine. It is worth noting that for the development of oliguria, the obstruction must be bilateral, or the patient must have a single kidney. Obstruction of the outflow of urine may be at the level of the ureters, bladder or urethra and be caused by a calculus, dysfunction of the bladder sphincter, compression by a tumor, or an enlarged lymph node.
Also, oliguria can be caused by a neoplasm of an organ located in anatomical proximity to the urinary tract. Oliguria almost immediately disappears after the removal of the obstruction in the MVP. The most common cause of postrenal oliguria is urolithiasis (urolithiasis). Other reasons are listed below:
- Bladder tumor.
- Severe prostatic hypertrophy (adenoma).
- Ureteral strictures.
- Fibrosis of the retroperitoneal tissue.
- Lymphoma.
- Urethral stricture.
- Aneurysm of the abdominal aorta.
- Colon cancer.
- Metastases of the lymph nodes of the retroperitoneal space.
- Taking medications that interfere with urination: anticholinergics (atropine).
Diagnostics
To find out the causes of oliguria, you should immediately contact a general practitioner, nephrologist or urologist. The doctor asks the patient in detail about the volume of urination, the presence of other complaints, previously diagnosed chronic pathologies, and the use of medications. The history of the disease is important - it is specified what preceded the appearance of oliguria.
A physical examination is also carried out: measuring body temperature, blood pressure, checking for Pasternatsky's symptom, and the presence of peripheral edema. This information helps the specialist to differentiate the etiological factor and correctly direct the diagnostic search. For this, an additional examination is assigned:
- Blood tests. With infections or autoimmune diseases, signs of inflammation are noted in the general blood test - leukocytosis and an increase in ESR. In the biochemical analysis of blood, the concentration of urea, creatinine, potassium, C-reactive protein is increased. With systemic bacterial infections, the blood is examined for the content of presepsin, procalcitonin. In the coagulogram, signs of hypercoagulability are often found - a shortening of the prothrombin time and aPTT.
- Urinalysis. With renal oliguria, signs of urinary, nephritic or nephrotic syndromes are revealed - proteinuria, hematuria, leukocyturia. To assess the concentration function of the kidneys or the presence of latent renal pathology, functional tests are prescribed - Zimnitsky, Nechiporenko, Kakovsky-Addis. In the case of a severe nephrological disease, microscopy of the urine sediment reveals casts (granular, erythrocyte), renal epithelial cells.
- Immunological research. If poststreptococcal glomerulonephritis is suspected, the level of antistreptolysin (ASLO) is checked. To confirm rheumatological diseases, tests for rheumatic factor and other autoantibodies are prescribed - antibodies to DNA, to the cytoplasm of neutrophils, to topoisomerase.
- ultrasound. Ultrasound of the kidneys can show various pathological signs - expansion of the pelvicalyceal system, parenchymal thickening, the presence of stones. On echocardiography in CHF, there is an expansion of the chambers of the heart, areas of myocardial hypertrophy, and a decrease in ejection fraction.
- Urography. Excretory urography allows you to establish the localization of a mechanical obstruction in the urinary system. It is often prescribed to patients with urolithiasis.
- Angiography. Angiography is recommended to assess the patency of the renal arteries. The narrowing of the lumen more than 50% indicates severe stenosis.
- CT. In case of oncological alertness, a CT scan of the abdominal cavity and small pelvic organs is performed to visualize a neoplasm of the kidneys or organs of the retroperitoneal space.
- Histological studies. To confirm the presence of a malignant tumor, a biopsy is taken, followed by pathological examination.
Also, for the differential diagnosis of prerenal and renal oliguria, the following is determined:
- osmolarity of urine incl. sodium concentration in urine;
- the ratio of urine osmolarity to plasma osmolarity;
- the ratio of urea and creatinine in urine to their level in plasma;
- partial excretion of sodium.
Hemodialysis
Correction
Conservative therapy
Regardless of the cause, a patient with oliguria should be hospitalized for treatment of the disease or pathological condition that caused this disorder. In case of kidney damage caused by taking a nephrotoxic drug, its urgent cancellation and replacement with a safer drug is necessary. In the hospital is carried out:
- infusion therapy. In case of prerenal oliguria, in order to compensate for the lack of fluid in the body and normalize the BCC, oral rehydration and parenteral administration of crystalloids (physiological saline, Ringer's solution) are prescribed. To stabilize the acid-base balance, namely, the correction of acidosis, the introduction of bicarbonate is recommended.
- Fight shock. In shock conditions, to improve renal blood flow, it is necessary to use cardiotonic (dobutamine, dopamine) and vasopressor agents (norepinephrine).
- Improving the pumping function of the heart. With a weak ejection fraction, drugs are used to treat heart failure - beta-blockers (bisoprolol), angiotensin-converting enzyme inhibitors (lisinopril), potassium-sparing diuretics (spironolactone).
- Fight against rheological disorders. In diseases accompanied by thrombosis, anticoagulants are prescribed - low molecular weight heparin, warfarin, dabigatran.
- Fight against infection. In patients with acute intestinal infection, antibacterial agents from the fluoroquinolone group (levofloxacin) are used. In pyelonephritis, the drugs of choice are penicillin antibiotics (amoxicillin) and cephalosporins (cefexime).
- Anti-inflammatory therapy. In the case of glomerulonephritis or nephropathy in rheumatological pathologies, drugs that suppress autoimmune inflammation are effective - glucocorticosteroids (prednisolone), cytostatics (azathioprine, cyclosporine).
- Chemotherapy. In oncological diseases, courses of chemotherapeutic drugs are prescribed - alkylating agents, antimetabolites, hormone antagonists.
- Extracorporeal detoxification . To remove the end metabolites of nitrogen metabolism accumulated in excess from the systemic circulation, as well as to combat hyperkalemia, hemodialysis or peritoneal dialysis is indicated.
Surgery
In case of urolithiasis, the method of removing stones is selected by the surgeon strictly individually for each patient (percutaneous nephrolitholapaxy, laparoscopic or open surgery). Depending on the volume of the lesion in polycystic or kidney tumors, resection or total nephrectomy is performed. With bilateral polycystic kidney transplantation is necessary.
Severe prostate hypertrophy is an indication for its removal or resection. With stricture of the ureter, reconstructive operations are performed - dissection of fibrous adhesions, plastic surgery with intestinal autograft, creation of an anastomosis. In severe stenosis of the renal artery, stenting is necessary.
Forecast
Oliguria is a severe pathological condition that requires the immediate establishment of an etiological factor and specific treatment. The outcome depends on the underlying disease. The most unfavorable prognosis is observed in patients with rapidly progressive glomerulonephritis, nephropathy with systemic scleroderma, and oncological pathologies.