After a weekend trip with her family this past summer, an 8-year old girl began to suffer bouts of profuse watery diarrhea. After noticing large blood clots in her stool, her mom took her to the family’s pediatrician, who admitted the child to a local hospital for treatment of dehydration. But the girl’s symptoms worsened with intermittent excruciating abdominal pain and bilious emesis, which prompted her transfer to Hopkins Children’s. There the child, who had no family history of inflammatory bowel disease or kidney disease, appeared pale and mildly distended on her abdominal exam. Labs showed low sodium, high potassium, and rapidly declining platelets.
“So, we have bloody diarrhea and platelets that look pretty bad,” said pediatric resident Emily Thomas at a recent case conference. “Can anyone suggest what this might be?”
The room was somewhat silent for a moment until pediatrician Julia McMillan asked where this patient’s family had spent its weekend trip. And in that destination – Cowans Gap State Park in Southern Pennsylvania – came the answer.
“HUS,” someone said from the back row of the case conference.
The platelets finding goes along pretty well with HUS, or hemolytic uremic syndrome, Thomas confirmed: “I would agree with that diagnosis.”
Thomas explained that the stool culture from the patient’s first day in the hospital came back positive for E. coli-O157:H7, which according to news reports the child had picked up along with at least a dozen other people who swam in the lake at Cowans Gap from July 12-31. Five of those afflicted were treated for HUS, a serious complication of this particular strain of E. coli that can involve the kidneys. Indeed, three of the patients had to undergo dialysis due to kidney failure, though this patient avoided dialysis. Case conference issues, Thomas said, include epidemiology of E. coli/HUS, transmission vectors, and treatments.
Infectious disease fellow Paul Sue noted that hemorrhagic colitis was first linked to the E. coli-O157:H7 strain in 1983, in a series of 47 cases (NEJM, March 24, 1983). In 1993, a multi-state outbreak involving over 500 people infected via undercooked fast-food meat raised a new level of awareness of the strain. Since that time, there have been over 350 outbreaks involving 8,500 individual cases linked to infections from sources like bologna, cheese, cookie dough, frozen pizza, and Romaine lettuce. But as the Cowan Gap outbreak illustrates, recreational swimming is also a vector for transmission of E. coli-O157:H7.
“It grows very well in the environment,” Sue said. “It can live up to 15 weeks in soil and has been reported to live for months in fresh water lakes.”
Following exposure to the strain, the bacterium will take 3 to 9 days to colonize, adhere to the bowel wall, and release shigalike toxin triggering watery stools followed by bloody diarrhea, a hallmark sign of HUS. About 5-10 percent of E. coli exposures progress to HUS, usually within 2 weeks of getting diarrhea, noted nephrology fellow Erin Dahlinghaus. The overall incidence of HUS is 2.1 cases per 100,000 persons per year, with a peak incidence in children younger than 5 years (6.1 cases per 100,00). HUS is more common in females, and more common in the summer and fall, paralleling the seasonal fluctuation of E. coli-O157:H7.
The mainstay treatment, Dahlinghaus said, is supportive care, including rehydration, electrolyte monitoring, and transfusions, though giving platelets should be avoided as they “add fuel to the fire” of the disease course. Caregivers should keep an eye out for bowel perforation, intussusceptions, pancreatitis and pancreatic insufficiency, and especially signs of renal involvement like increased creatinine and electrolyte abnormalities. Guidelines for when to give dialysis include a 24-hour period of no urine output, rapidly rising blood urea nitrogen, severe fluid overload, or electrolyte abnormalities that are not responding to medical management. The prognosis?
“There’s low mortality with supportive treatment, but things that may predict poor prognosis include high blood counts and older age onset,” Dahlinghaus said. “Even if you do recover, many patients face long-term complications like chronic kidney disease, hypertension and renal insufficiency.”
Hopkins Children’s Director George Dover asked why this patient’s outcome was different than the other patients exposed at Cowans Gap? What would explain such a variation in the same syndrome?
“It really is important in contemporary medicine to think about how one patient is different than the other, and this is a phenomenally good case to illustrate that because you have exposures to the same organism with the same toxin and the same syndrome,” Dover said. “If we could figure out what made this child mild vs. the others who went on dialysis, we may come up with other options in treating these patients.”
For Sue, the big unknown in this particular case is the source of the exposure. The lake water and all of the tributaries tested negative and tests of the park’s sewage system have thus far been inconclusive. The current working hypothesis, he added, is human fecal contamination.
“What do children do in the water that most adults do not do?” Sue asked. “This was likely a human injection of the pathogen.”
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