Sunday, November 23, 2008

The great NEC scare of last week

About a week ago, shortly after graduating to an open crib and having been fully weaned from respiratory support and IV nutrition, Max's belly began to swell, he quit stooling, and he showed other signs of sepsis such as an inability to maintain his temperature. It turns out that infants react to infections with falling temperatures, as well as the fevers exhibited by older children. Max's white blood cell counts were elevated, but not terribly so. Nothing was growing in the blood or spinal fluid cultures. So what could be causing his symptoms?

The NICU team ordered x-rays of his gut every 12 hours and started him on a couple of antibiotics rather than wait to see bacteria gain clear purchase in his intestines. They suspected NEC or necrotizing enterocolitis. This is an infection of the gut that is quite common in preemies. Treatments include lengthy bowel rest (i.e. a return to IV nutrition), heavy antibiotics and, in some cases, surgery. The NICU staff returned Max to an isolette, put him back on a nasal canula with a little bit of additional oxygen, and returned him to IV nutrition. After a few days of bowel rest, Max's belly shrank significantly and his blood cultures continued to show no infection.

(Math problem: If 10 percent of preemies get NEC, the test is negative with a 5 percent false negative rate, what is the probability that Max actually has NEC?)

So Max either had a mild case of NEC that was quickly stomped on by the aggressive NICU treatment protocol, or he has something else. The NICU has recently been reintroducing Max to milk, and today he was on 100 percent milk, without supplementary IV nutrition. We'll see how he tolerates it this time. Unlike the last time Max was weaned from IV nutrition, he is getting some respiratory support with a nasal canula blowing room air, and is in an enclosed isolette to keep his temperature regulated. The idea is to minimize both the stress on his system, and to change only one thing at a time.

So what caused Max's bowel problems if not NEC, and might they reappear? The leading candidates, as we understand them, are:
  1. Sodium deficiency caused by Max's fairly regular lumbar punctures (aka "spinal taps")
  2. Something called "Hirschsprung's Disease", a 1:5000 genetic disorder that limits the gut's ability to digest food and move it along the intestine.
  3. A low-grade case of NEC that was stomped on so quickly and thoroughly that the offending bacteria were extirpated before they grew enough to be detected by the doctors.
In the meantime, the NICU staff are watching Max's belly for renewed swelling and also keeping him on a canula. Next week they'll do some tests for Hirschsprung's Disease.

Some useful links (scary links marked for the faint of heart to avoid):
  1. Necrotizing enterocolitis at Wikipedia (warning: scary link)
  2. Hirschsprung's disease study website at Johns Hopkins
  3. Bayes Law at Wikipedia