As nephrology fellows we see a lot of Acute Kidney Injury (AKI) on the inpatient consultative service. When AKI in the hospital requires dialysis people and their families naturally want to know whether this means long term dialysis will be required.
The answer, as with many things in medicine, is it depends. AKI has a wide variety of causes but one of the most commonly encountered entities in the hospital is Acute Tubular Necrosis (ATN) and luckily we have a number of good studies to help inform prognosis.
One of the first things to realize about hospitalized AKI due to ATN that requires dialysis is that it is associated with a very high in-hospital mortality rate. In the ATN study which examined critically ill ICU patients with AKI presumed secondary to ATN randomized to either intensive or less-intensive dialysis there was a roughly 50% in-hospital mortality in both groups.
In those with ATN who require dialysis and survive hospitalization, whether or not long term dialysis is required depends on the demographic. In general, the lower the baseline kidney function at the time of AKI the higher the rates of long term dialysis dependence.
The ATN study excluded patient’s with advanced CKD (about 30% of patients though had moderate CKD with GFRs between 30 and 59 ml/min/1.73m2). Around 70% of people who survived to day 28 continued to require dialysis. In contrast, in a German cohort of 433 critically ill patients all with GFRs of greater than 90 ml/min/1.73m2 who developed dialysis requiring AKI from ATN not one survivor (in hospital mortality was again approximately 50%) required long term dialysis at discharge.
In terms of more advanced CKD, a study using the Northern California Kaiser Database looked at patients both in and out of the ICU who developed AKI requiring dialysis (greater than 90% of patient’s had likely ATN by subset chart review). Of those that survived the hospitalization (overall mortality was 26%) 42%, 63% and 90% of patients with eGFRs of 30-44, 15-29 and less than 15 ml/min/1.73m2 respectively were felt to be dialysis dependent within 30 days of hospital discharge (a selected chart review revealed no cases of recovery within three months).
In summary those with AKI secondary to ATN who require dialysis in the ICU have a very high mortality rate. Of survivors, approximately 70% will require long term dialysis unless they enter the hospital with completely normal renal function in which case the chances of renal recovery appear to be quite good. Patient’s with the most advanced form of CKD who develop AKI requiring dialysis are very unlikely to recover.