#425 - 🏖️ [COOL TOPICS] - Are We Missing Neonatal AKI Right in Front of Us? (ft. Dr. Caitlin Carter)

Dr. Caitlin Carter, Clinical Director of Nephrology at Rady Children’s Hospital and associate clinical professor at UC San Diego, joins the podcast to challenge how neonatologists recognize and follow up on acute kidney injury. She explains why creatinine alone is insufficient, how biomarkers like NGAL can detect tubular injury before function declines, and why AKI too often disappears from the discharge summary. She also outlines published consensus guidelines on post NICU nephrology follow-up, with clear thresholds based on gestational age and AKI severity.

Transcript

Ben Courchia MD (00:04.984) Hello everybody. Welcome back to the Incubator Podcast. We're live at Cool Topics in Neonatology in San Diego, California. We have the pleasure of being joined in the studio by Dr. Caitlin Carter. Caitlin, welcome to the podcast. You come to us from Rady Children's Hospital — not too far from here, just down the road. You are a pediatric nephrologist, and we are always —

Dr. Caitlin Carter (00:15.8) Thanks for having me.

Daphna Yasova Barbeau MD (00:30.328) I know.

Ben Courchia MD (00:30.926) — always so excited to talk to our subspecialty colleagues. You have a session on the agenda today: Making Sense of AKI — biomarkers, follow-up, and long-term outcomes.

Daphna Yasova Barbeau MD (00:48.706) That's a big topic.

Dr. Caitlin Carter (00:49.6) It is a big topic — there's so much to talk about.

Ben Courchia MD (00:52.034) What are we still getting wrong about AKI today — as neonatologists?

Dr. Caitlin Carter (00:55.01) I think we're still missing a lot of AKI in the neonatal ICU. We know that we're not always checking creatinine, and that creatinine may not be the best marker for diagnosing acute kidney injury. And even when we do identify AKI, it doesn't always make it to the problem list, then to the discharge summary, and then to outpatient follow-up. We're still missing a lot.

Daphna Yasova Barbeau MD (01:21.998) I have a few questions about that. The first is: we see so many babies where the kidney is clearly affected, but they get better. When it doesn't make it to the discharge problem list and nephrology follow-up isn't arranged — what are the long-term consequences?

Ben Courchia MD (01:23.31) Can you come a little bit closer?

Dr. Caitlin Carter (01:42.168) It's hard to separate the long-term effects of acute kidney injury from the risk factors for it. We know that preterm babies may have kidneys that aren't fully developed, putting them at higher risk for AKI — but they're also at higher risk for chronic kidney disease independent of any acute kidney injury. What we see over the long term is that kids who have had neonatal AKI — whether associated with surgery, sepsis, or early preterm birth — are at higher risk for hypertension, chronic kidney disease, and proteinuria, which is an early marker of CKD risk. We see this at two years, at five years, at seven years, and in adults who were once NICU graduates. We've started to really understand this and to follow it more closely. As we accumulate data on larger cohorts of neonates, we'll be better able to sort out what are risk factors for AKI versus CKD, and how those things relate to each other.

Ben Courchia MD (02:50.486) Some people might say, "But I do check creatinine and it's below one — I write it down. So why am I still missing AKI?"

Daphna Yasova Barbeau MD (02:53.89) Write it down.

Dr. Caitlin Carter (02:57.368) Creatinine should be going down in the early period right after birth. So even a stable creatinine indicates renal function isn't normal — that's one issue. The other is that there's a group of infants who have kidney injury without a decrease in function. Creatinine is really a marker of kidney function, not injury. So if injury is present but function is preserved, you'll miss it because you're not looking at the right lab.

Ben Courchia MD (03:25.966) So should people be looking at other specific labs? Kidney function shows up in so many places even inadvertently — and urine output is another diagnostic criterion. If somebody hasn't done a formal workup but has a standard flow sheet and vital signs, what should they be looking at?

Dr. Caitlin Carter (03:36.588) Right, so urine output is the other major diagnostic criterion for AKI. And then there are biomarkers, which we'll be talking about this afternoon. The best studied is probably NGAL — Neutrophil Gelatinase-Associated Lipocalin — which is a marker of tubular injury that rises before AKI is established. In neonates at high risk for AKI, it has a very high negative predictive value. So if a baby is high risk but has a low NGAL, that tells you this may be a baby who isn't going to develop AKI — maybe you don't need to check creatinine every day without another reason. But if NGAL is elevated, that tells you there has been kidney injury even if function appears preserved.

Ben Courchia MD (04:36.566) Is that something most labs can run? A lot of the time, when we're discussing more advanced testing, people wonder whether their lab is set up for it. The best way to find out is usually whether it's already being run in adults —

Dr. Caitlin Carter (04:52.35) Yes, there's a lot of data in adults. Interestingly, the earliest data actually came from pediatrics — starting with cardiac surgery — and then spread into the adult literature. I can't speak for every hospital, but at my institution I can get an NGAL nearly as quickly as a creatinine. We run it in-house, and it's a really useful tool for determining risk and identifying early injury.

Daphna Yasova Barbeau MD (05:23.81) What are some of the symptoms of AKI that we're not really connecting to the kidney? In our unit, for example, we see a lot of acidosis and poor growth, and I think people don't always recognize that the kidney may be the driver.

Dr. Caitlin Carter (05:46.23) Well, the kidney is really important for everything. I don't know if you know that.

Ben Courchia MD (05:51.502) We do.

Dr. Caitlin Carter (05:52.078) Homeostasis is pretty crucial. In terms of other manifestations, we know that AKI — especially if it persists — is associated with longer time on the ventilator, worse pulmonary outcomes, worse outcomes with HIE, and worse NEC outcomes. All of those things are impacted by even relatively low-grade AKI. So thinking about the kidney whenever you have a complex problem in a really sick baby is important.

Daphna Yasova Barbeau MD (06:39.63) And where are we missing the mark in preventing kidney injury? It seems like all of our babies are already at risk — prematurity itself is the risk factor.

Dr. Caitlin Carter (06:54.978) The biggest area where we can make a difference is medication use. Gentamicin, indomethacin — all of the drugs we have traditionally used with some regularity in premature infants put them at risk for AKI. There's good data over the last decade showing that reducing nephrotoxic exposures in the NICU can reduce the incidence of AKI. That's the "do no harm" piece. Everything you all do around hemodynamic management and fluid status is also really important. We know that fluid overload — once urine output starts to drop or hasn't picked up — is a major risk factor for worse outcomes. And being more fluid overloaded at the time you start dialysis puts a baby at much higher risk for a poor prognosis. Those are the preemptive things we can do.

And then in the bigger picture — the risk factors for being born preterm. The socioeconomic and demographic factors that put people at risk for preterm birth or IUGR, addressing those will ultimately help prevent neonatal kidney injury as well.

Daphna Yasova Barbeau MD (08:26.146) My last question: which babies — the baby who was sick, ventilated, premature — which of those babies do not need to see a nephrologist at follow-up?

Dr. Caitlin Carter (08:36.322) There are recently published, comprehensive guidelines on this. Any baby born under 28 weeks should probably have a kidney assessment at two years — just a comprehensive check to make sure everything looks good. Babies born between 28 and 32 weeks who have had AKI, particularly high-grade AKI, should have follow-up at six months and again at two years. Any baby who has had what we call stage two or stage three kidney injury needs to be seen by nephrology. And babies with other systemic disorders — particularly the congenital heart kids, the single-ventricle kids — probably need to see a nephrologist sometime in the first couple of years of life.

Daphna Yasova Barbeau MD (09:31.662) We actually covered this in our nephrology year-in-review episode — specifically the paper on kidney health monitoring recommendations for NICU graduates, a modified Delphi consensus statement. That was episode 344, which included a great discussion on nephrology.

Dr. Caitlin Carter (09:58.28) Yes — and I believe the follow-up chart from that paper is actually my last slide today.

Ben Courchia MD (10:03.912) Perfect — that's a great segue. Caitlin, thank you so much for dropping by the booth. We're looking forward to your talk.

Dr. Caitlin Carter (10:09.632) Thanks for having me.

Daphna Yasova Barbeau MD (10:10.744) Thank you.