If, on every consult for acute kidney injury, you limited your differential to pre-renal azotemia, obstruction and run-of-the-mill ischemic ATN you would be capable of reaching the right diagnosis 95% of the time. Common causes of renal failure are common. All the time we spend learning and teaching about glomerulonephritis, interstitial nephritis, vasculitis and the other zebras of acute renal failure is usually time wasted. However, your job as a consult nephrologist is to hunt down and flush these zebras. I strive to try and fit every clinical scenario into one of these alternative rare diagnosis. Because if you are not actively hunting a zebra, you will never find one.
When you see community acquired pneumonia and the ICU intern mentions that there was a lot of blood during the intubation your mind needs to starting thinking about pulmonary-renal syndromes. Ask the family about a history of sinusitis, pay extra-attention to the red cells on the U/A, fire off that ANCA and anti-GBM ab. It is the job of the nephrologist to consider this diagnosis, if you don’t no one will and a week later when the ICU and ID teams begin scratching their collective heads on why this patient is not behaving like a typical pneumonia you will have the reason and prevent a low yield and dangerous bronchoscopy because you will have the serologic evidence you need to get the renal biopsy for the win.
The cryptic case of acute kidney injury starts off just like the banal case of acute renal failure, a rise in creatinine. If you open your eyes to the faint threads that don’t quite fit the standard narrative you will be more receptive to seeing the clues you need to make that rare diagnosis.
Thanks for this healthy reminder.
I tend to get "lazy" in my thinking since most of what I see fits into a template I could pretty much stamp on the chart and fill in the details like age and baseline creatinine. But you are right, we need to be hungry or we'll never find the gold.
I remember Jerry Levine, one of my teachers, told me the pre-test probability of ischemic ATN on AKI consult in the ICU was about 95%. He thought this pearl was particularly useful for late Saturday afternoon consults.