What Is Hemolytic Uremic Syndrome?

Hemolytic uremic syndrome (HUS) is a type of syndrome of acute intravascular hemolytic anemia with renal failure of unknown cause. The disease involves multiple systems and is mainly characterized by microangiopathic hemolysis, acute renal failure, and thrombocytopenia. It is one of the common causes of acute renal failure in children. More than a third of children with HUS may have neurological involvement. Because HUS and thrombocytopenic purpura (TTP) have similarities in etiology, pathogenesis and clinical manifestations, more and more scholars believe that the two are clinical manifestations of different stages of the same disease, which can be collectively referred to as HUS / TTP or thrombotic microangiopathy (TMA). With the improvement of diagnosis and treatment technology, the prognosis of HUS has changed.

Basic Information

English name

hemolytic uremic syndrome

Visiting department

Nephrology

Common causes

Related to family genetics, infections, drugs, secondary to certain immunodeficiency diseases, etc.

Common symptoms

Abdominal pain, vomiting and diarrhea, melena, vomiting blood, anuria, oliguria or hematuria, etc.

Causes of hemolytic uremic syndrome

Primary

No clear cause. May be related to family heredity, the disease is autosomal recessive or dominant, and occurs in the same family or siblings. Three siblings have been reported in China.

Secondary

(1) The infection is currently relatively clear in E. coli O157: H7, which produces helical cytotoxin. Shigella dysenteriae type I can also produce this toxin. Neuraminidase produced by Diplococcus pneumoniae can cause glomeruli. And vascular endothelial damage. Others are also found in typhoid fever, Campylobacter jejuni, Yersinia, Pseudotuberculosis, Pseudomonas, Pseudomonas, and some viral infections such as myxovirus, coxsackie virus, ecovirus, influenza virus, EB Virus and Rickettsia infection.

(2) Secondary to certain immunodeficiency diseases such as agammaglobulinemia and congenital thymic hypoplasia.

(3) Drugs such as cyclosporine, mitomycin and contraceptives.

(4) Others who are combined with pregnancy, organ transplant, glomerular disease and tumor.

3. Recurrent

It is mainly seen in children with genetic predisposition and after transplantation, and sporadic cases can also be seen.

Clinical manifestations of hemolytic uremic syndrome

The prodromal symptoms are mostly gastroenteritis, which manifests as abdominal pain, vomiting, and diarrhea. It can be bloody diarrhea, which is very similar to ulcerative colitis. There are also reports of acute abdomen. A few prodromal symptoms are respiratory infections, accounting for 10% to 15%. The prodromal period lasts 3 to 16 days (average 7 days). Mortality was significantly higher in those without gastroenteritis precursor symptoms. A few days or weeks after the prodromal period, an acute onset immediately followed by severe manifestations within a few hours, including hemolytic anemia, acute renal failure, and bleeding tendency. The most common complaints were melena, vomiting blood, anuria, oliguria, or hematuria. The child was pale and weak. Hypertension accounts for 30% to 60%, nearly 25% of patients have congestive heart failure and edema, 30% to 50% of patients have hepatosplenomegaly, and about 1/3 of patients have skin ecchymosis and subcutaneous hematoma, 15% to 30% Children have jaundice.

Some symptoms vary by region, and the main prognosis is the degree of kidney damage. 86% to 100% have oliguria, and 30% of patients have no urine (for 4 days to several weeks). In some infant cases, only transient oliguria and abnormal urine are present. Renal function is fully restored in most patients. Some cases of chronic renal insufficiency and hypertension. Children with this disease may have relapses, and those with relapses have a poor prognosis.

Hemolytic uremic syndrome test

Hematological changes

Due to acute hemolysis, the hemoglobin drops significantly, which can be reduced to 30-50 grams / liter, reticulocytes are significantly increased, and serum bilirubin is increased. Peripheral blood features are characteristic of abnormal red blood cell morphology, manifested as unequal size, polychromatic, triangular, thorn-like, and red blood cell debris. Leukocyte elevation can be seen in 85% of patients. In 90% of cases, thrombocytopenia occurred at the beginning of the disease, with an average of 75 × 10 ⁹ / L, and most of them returned to normal within 2 weeks.

2. coagulation factor test

The result is closely related to the illness. In the early stage, prolonged prothrombin time, decreased fibrinogen, increased fibrin degradation products, and decreased coagulation factor , , , and X, but returned to normal after a few days.

3. Urine routine

Can be seen in varying degrees of hematuria, red blood cell debris, 10% of gross hematuria, severe hemolysis may have hemoglobinuria. In addition, there are varying degrees of proteinuria, leukocytes, and casts. Renal function tests showed varying degrees of metabolic acidosis, hyperkalemia, and azotemia.

Diagnosis of hemolytic uremic syndrome

It is not difficult to make a diagnosis based on the precursor symptoms and sudden appearance of hemolytic anemia, thrombocytopenia and acute renal failure, but it should be distinguished from other causes of acute renal failure, glomerulonephritis, thrombocytopenia, and hemolytic anemia.

Complications of hemolytic uremic syndrome

In the acute phase, various complications of acute renal failure can occur, such as congestive heart failure, pulmonary edema, hypertensive encephalopathy, hyperkalemia, and metabolic acidosis. Chronic renal insufficiency, sequelae of nervous system damage such as mental retardation, limb paralysis, mental and behavioral abnormalities, and seizures can occur in the chronic phase.

Hemolytic uremic syndrome treatment

There is no special treatment for this disease. Mainly early diagnosis, early treatment of water and electrolyte disorders, early control of hypertension, early peritoneal dialysis and hemodialysis.

1. Treatment of acute renal failure

Similar to general acute renal failure treatment. Emphasis should be placed on strictly controlling the dose, actively treating hypertension, and giving intravenous high nutrition appropriately.

2. Indications for dialysis

(1) No urine for 24 hours;

(2) BUN rises rapidly;

(3) Those with severe water overload, such as congestive heart failure and volume hypertension, who do not respond to furosemide;

(4) Electrolyte and acid-base balance disorders who do not respond to non-dialysis therapy, such as serum potassium> 6mmol / L.

3. Correction of anemia

The blood transfusion should be as little as possible and a small amount of blood transfusion. If the hemoglobin is below 50 g / l, the fresh red blood cells can be transfused three times, 2.5 to 5 ml / (kg · times), and slowly input within 2 to 4 hours. Bleeding due to thrombocytopenia can be transfused into platelets.

4. Anticoagulation therapy

There is no uniform effective therapy.

(1) Heparin treatment is clinically controversial. Because the basic pathological change of the disease is local intravascular coagulation, which is theoretically effective, it should be given early and pay attention to the bleeding tendency of the disease, which should be performed under close observation.

(2) Antiplatelet agglutination drugs Aspirin and persantin can shorten the time of thrombocytopenia. However, because aspirin is a prostate cyclooxygenase inhibitor, it can inhibit the production of prostacyclin (PGI ₂ ) and thromboxane A ₂ (TXA ₂ ) at the same time.

(3) Increasing the level of anti-platelet aggregation agent PGI _{2 in} blood It has been reported that continuous infusion with PGI ₂ intravenously, transfusion of fresh frozen plasma (recover PGI ₂ activity) or plasma exchange therapy (supplemental stimulation of PGI ₂ production, supplementation or removal of required plasma factors The substance that inhibits PGI ₂ in plasma), preliminary observation can increase platelets, and diuretic and improve renal function, further research is needed.

(4) Other therapies Adrenocortical hormone is not used because of its procoagulant effect. In addition, it should be noted that in HUC caused by pneumococcus, plasma transfusion is contraindicated. Intravenous gamma-globulin treatment was also ineffective.

Prognosis of hemolytic uremic syndrome

It is mainly determined by the severity of renal involvement, and individual deaths due to damage to the nervous system, without prodromal disease, relapse, and familial tendencies, the prognosis is poor. In the 1950s, the case fatality rate was as high as 40% to 50%. Due to the improved treatment of acute renal failure, the case fatality rate has dropped to about 15% in recent years, and some reports have been as low as 4.5%.