A 3-year-old child presents to the emergency center with history of bloody diarrhea and decreased urination. The mother states that the child's symptoms began 5 days ago after the family ate at a fast-food restaurant. At that time the patient developed fever, vomiting, abdominal pain, and diarrhea,On physical examination the patient appears ill. He isj)ale and lethargic.
Definition. Hemolytic uremic syndrome is a systemic disease that causes acute renal failure in young children, as well as hematologic manifestations.
Risk Factors/Etiology. Hemolytic uremic syndrome is caused by Escherichia coli (0157:H7). This organism may be transmitted by undercooked meat and unpasteurized milk. It has also been associated with other bacterial and viral infections. In addition, bathing in contaminated swimming pools, drinking contaminated apple cider, and oral contraceptives have also been associated with hemolytic uremic syndrome. E. coli (0157:H7) produces a verotoxin that is absorbed from the intestines and causes endothelial cell injury of the infected individual. Endothelial injury of the kidney results in localized clotting. Red blood cell and intrarenal platelet damage causes microangiopathic anemia and thrombocytopenia.
Presentation. This syndrome usually occurs in children younger than 4 years of age. The patient may have had gastroenteritis before onset with bloody diarrhea or upper respiratory infection symptoms. Approximately 1 week after these symptoms the patient may develop oliguria and may be pale, weak, and lethargic.
Physical Examination. In addition to the physical findings described above in the Presentation, the patient may be dehydrated and have hepatosplenomegaly and petechiae. The patient may appear ill tempered.
Diagnostic Tests. This syndrome should be suspected in patients with acute renal failure and microangiopathic hemolytic anemia. The diagnosis is made on history and clinical and laboratory findings. The complete blood count may show the white blood cell count to be 30,000/mm3, hemoglobin to be 5-9 g/dL, and platelets to be 20,000-100,000/mm3. Helmet and burr cells may be seen on peripheral smear. The Coombs test is negative. Hematuria and proteinuria may be seen on urinalysis. The renal involvement varies from mild renal insufficiency to severe renal failure requiring dialysis.
Treatment. Management of renal failure and hematologic problems should be the goal of therapy. Peritoneal dialysis is essential to control the uremic state and to remove an inhibitor of fibrinolysis. Ninety percent of patients survive the acute phase of the disease, and most regain normal renal function. Corticosteroids are not helpful as therapy for hemolytic uremic syndrome.
Complications/Follow-up. Anemia, hypertension, acidosis, heart failure, diabetes mellitus, seizures, and colitis are some of the complications of hemolytic uremic syndrome. The pathogenesis of these complications is unknown. Patients with hemolytic uremic syndrome should be monitored for late onset of hypertension and chronic renal disease.
Differential Diagnosis. Hemolytic uremic syndrome looks similar to thrombotic thrombocytopenic purpura (TTP), but TTP occurs in young women and affects the central nervous system. Patients with TTP also have fever, decreased platelets, and cutaneous symptoms. Lupus and malignant hypertension should also be considered in the differential because both may have acute renal failure and anemia. Bilateral renal vein thrombosis has a similar presentation to hemolytic uremic syndrome (gastroenteritis, pallor, dehydration), but children with renal vein thrombosis have large kidneys.
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