P0886 - Hemolytic Uremic Syndrome Associated with Entamoeba Histolytica

Introduction:
Hemolytic uremic syndrome (HUS) is a clinical syndrome characterized by progressive kidney injury from damage to the renal microvasculature, microangiopathic hemolytic anemia, and thrombocytopenia secondary to destruction and consumption of platelets. In most cases, HUS occurs after a severe bowel infection with certain toxic strains of the bacteria E. coli; however rarer causative organisms have also been reported, as in this patient.


Case Presentation:
A two-year-old male presented with three days of fever, watery diarrhea, and decreased oral intake in the setting of recent freshwater pond exposure one day prior. He was initially evaluated by his pediatrician with presumed viral gastroenteritis. However, disease progression and development of bloody stool prompted emergency room presentation. Initial evaluation revealed a non-focal exam with exception of dehydration and fever to 103F. Preliminary workup included blood work, stool, and urine studies which were significant for WBC 12.7 with 13% bandemia, presence of stool erythrocytes, and urine specific gravity >1.030 with 3+ ketones. Imaging studies (abdominal x-rays, intussusception/appendix ultrasounds) were normal. He was admitted to the floor for IV hydration and pain control. His floor course was notable for persistent hematochezia and fevers, worsening pain, and development of oliguria with new onset hypertension over 48 hours. Repeat labs demonstrated acute hemolytic anemia, thrombocytopenia, and profound acute kidney injury with rising creatinine from 0.31mg/dL at presentation to 2.37 mg/dL, consistent with the diagnosis of hemolytic uremic syndrome. Stool antigen studies returned positive for Entamoeba histolytica. The patient received dual antibiotic therapy with ceftriaxone and metronidazole, and was transferred to the ICU for dialysis and blood transfusions.

Discussion:
Parasitic colitis should be on the differential for patients with bloody diarrhea, especially if history suggests exposure to contaminated food/water or farm animals. Entaemoeba parasitic infection is primarily seen in developing countries and is transmitted via fecal-oral contact due to ingestion of amebic cysts. Symptoms are variable with up to 90% of cases being asymptomatic versus development of dysentery. Preferred diagnostic method is via stool/serum antigen studies or PCR to distinguish between E. histolytica (pathogenic) vs. E. dispar (nonpathogenic). Given the risk of severe infection and transmission, dual therapy is indicated for all E. histolytica with antibiotics to target colitis and amebicides for intraluminal infection.

While 90% of cases of HUS are caused by Shiga toxin-producing E.coli, HUS should also be considered with Entamoeba histolytica, as demonstrated by this patient. Special attention should be drawn to urine output as well as hypertension for patients with bloody diarrhea. Although urine output can be difficult to quantify with concurrent diarrhea, and reliable blood pressure readings may be challenging to obtain in pediatric populations, attention to these details may spark early detection and treatment of HUS.