Acute kidney injury is a frequent complication for critical newborns. Its management is a significant challenge, especially in extremely low-birth-weight (ELBW) infants. Currently, peritoneal dialysis (PD) is the most manageable treatment. However, data are lacking regarding when diuresis can be declared irreversible relative to the start of PD. A female infant born at 28 + 0 weeks with a birth weight of 800 g by monochorionic diamniotic pregnancy, complicated by twin-to-twin transfusion syndrome, developed acute renal failure on the second day of life because of long-term intrauterine hypoperfusion. PD was started on day 7. The patient remained anuric until the 52nd day of dialysis, when she presented adequate urine output of 2.5 mL/kg/h and PD was suspended for 11 days. After an episode of sepsis, PD was re-started, and after 50 days of treatment, given a urine output of 1.5 mL/kg/h, it was discontinued. The patient died on day 132 after a disseminate infection, which led to multiorgan failure. In ELBW infants, PD is a valid therapeutic instrument to treat patients with renal failure. Despite the evidence of low renal functional reserve in these patients, the duration of recovery from diuresis after a period of anuria can be very long.