Acute Ipsilateral Renal Dysfunction after Partial Nephrectomy in Patients with a Contralateral Kidney: Spectrum Score to Unmask Ischemic Injury

Acute ischemic injury in the operated kidney after partial nephrectomy (PN) is often masked by a functional contralateral kidney; however, there is no practical method to assess this and its prognostic significance has not been defined.

We propose a spectrum score to reflect the degree of ischemic insult in the ipsilateral kidney and study its relationship to subsequent functional recovery.

From 2007 to 2014, 243 patients with a functional contralateral kidney underwent PN with necessary studies for detailed analysis of function and parenchymal mass before and after surgery in the ipsilateral kidney. Based on split function and percent parenchymal mass preserved in the ipsilateral kidney, we determined: serum creatinine (SCr)_ideal-peak: expected peak SCr presuming no ischemic injury; and SCr_{worstcase-peak}: expected peak SCr presuming temporary complete nonfunction of the ipsilateral kidney. The acute ipsilateral renal dysfunction spectrum score was defined: (observed peak SCr - SCr_ideal-peak)/(SCr_{worstcase-peak} - SCr_ideal-peak). Subsequent functional recovery was defined: (percent function preserved)/(percent mass saved).

PN.

Factors associated with spectrum score and relationship between spectrum score and subsequent functional recovery were evaluated by linear regression.

Median duration of warm ischemia (n=152) was 21min (interquartile range [IQR] = 15-27) and hypothermia (n=91) 26min (IQR=23-30). Median parenchymal mass preservation was 83% (IQR=74-91%). Warm ischemia and longer ischemia duration associated with higher spectrum score (both p<0.05). Increased spectrum score (<25%, 25-50%, 50-75%, and >75% quartiles) had decreased functional recovery (98%, 94%, 90%, and 89%, respectively, p<0.001). However, this trend was not observed in the hypothermia cohort. On multivariable analysis spectrum score and ischemia type significantly associated with functional recovery (both p<0.01), while age and comorbidities failed to associate (p=0.3-0.7).

Acute ipsilateral renal dysfunction spectrum score unmasks the degree of ischemic insult in the operated kidney after PN and associates with functional recovery. While increased spectrum score associates with suboptimal recovery, even patients with a high spectrum score reached 89-90% recovery.

Acute functional decline after partial nephrectomy is difficult to evaluate in patients with two kidneys, but a proposed spectrum score can be used to evaluate this. Increased spectrum score reflects increased ischemia and may impact the functional recovery of the kidney.