In this retrospective observational study, we found that only 86.1% of oncological patients undergoing major abdominal surgery in a tertiary university hospital had at least one sCr value available to detect postoperative kidney impairment. Among these, PO-AKI was present in 8.2% of cases. We do not have data on long-term kidney function for 21% of the patients enrolled, despite the fact that PO-AKI was detected in 3.3% of them. Interestingly, 33 of 423 patients (7.8%) had no sCr immediately postoperatively or in the long-term follow-up period, although all the physicians engaged with the care of those patients recognised that postoperative assessment of sCr is required after major oncological abdominal surgery, particularly in patients at high-risk to develop PO-AKI and LT-KDys (see Table 3).
PO-AKI is a very well known postoperative complication occurring in patients undergoing cardiac and non-cardiac surgery(Romagnoli and Ricci 2015). Wang and Bellomo showed that the incidence of cardiac surgery-associated AKI ranged from 5 to 42%(Wang and Bellomo 2017); in comparison, Long et al. showed that AKI after major abdominal surgery occurred in 12 to 22% patients (Long et al. 2016). This wide variability might be related to differences in case mix and diagnostic criteria used to define AKI. In a prospective study, we previously showed a 12% incidence of PO-AKI in a cohort of adults undergoing major abdominal surgery(Romagnoli et al. 2016a). A slightly smaller incidence of PO-AKI (8.2%) has been observed in the present study, notwithstanding the similarity of the cohorts observed. The lack of urinary output criteria in this retrospective study might explain the slightly smaller incidence of PO-AKI compared to that reported in the previous prospective study (where AKI was defined using both serum creatinine and urinary output criteria of AKIN classification).
Interestingly, there may be a widespread lack of awareness of the clinical relevance of PO-AKI in clinical practice. Indeed, while several technologically advanced tools and/or strategies for early identification of high-risk patients and PO-AKI are currently developed and described in the literature, sCr still remains the most used biomarker. Although physicians theoretically appreciate the diagnostic and prognostic role of perioperative sCr, in practice, they seem to miss the opportunity to measure sCr and individualise patients’ clinical management. The exact reasons for not measuring sCr after major surgery are not clear. Interestingly, in patients in whom sCr was measured postoperatively, a proportion of patients with PO-AKI did not have a repeat sCr measurement either before hospital discharge or at 1-year follow up or a referral for nephrology follow up.
Our analysis identified similar risk factors for PO-AKI as reported in the literature: preoperative CKD, older age and perioperative use of nephrotoxic drugs (An et al. 2018). Ideally, these risk factors should prompt clinicians to intensify perioperative monitoring for early diagnosis of PO-AKI. In particular, the early recognition of high-risk patients provides an opportunity for adoption of diagnostic and therapeutic measures to prevent renal impairment such as goal-directed fluid therapy based on physiological parameters in order to optimise oxygen delivery, avoidance of drugs that can impair renal function, strict glycaemic control.
In this retrospective study, 59 patients (13.9%) had no sCr assessed postoperatively, despite the fact that they had undergone major abdominal surgical procedures for a malignant disease. Interestingly, 4 of them (6.8%) had pre-existing CKD, 5 (8.5%) had more than three preoperative risk factors for perioperative AKI, and 3 (5.1%) had more than four (Table 1). Thus, all of them were potential high-risk patients. Yet, serial assessment of postoperative sCr was not undertaken and opportunities for intervention were missed. Furthermore, not all patients with PO-AKI received perioperative surveillance, specific recommendations or specialised nephrology consultations and, more importantly, for some of them (3.3%), long-term renal function was not assessed at all.
Our results show that preoperative cardiovascular comorbidities, perioperative shock, and PO-AKI were significantly associated with LT-KDys. The identification of these risk factors should prompt clinicians to intensify postoperative long-term monitoring for early diagnosis of CKD. Interestingly, among patients without a sCr available postoperatively, 33 (55.9%) did not have renal long-term follow-up after surgery (Fig. 1). For these patients, renal prognosis is unknown.
We recognise that our study has some limitations. First, this is a single centre retrospective analysis and some sCr results were missing which impacts the incidence of PO-AKI. Second, we only used sCr results to diagnose AKI and acknowledge that the incidence of PO-AKI might be underestimated. Third, data on fluid administration and fluid balance were not available to us. We acknowledge that sCr concentration is influenced by fluid accumulation (De Rosa et al. 2016). Fourth, all patients enrolled in this study underwent surgery for malignant disease. Although we excluded patients who underwent postoperative chemotherapy, we recognise that patients were exposed to other nephrotoxic agents in the first year postoperatively. Thus, the development of LT-kDys might be caused by more factors than PO-AKI alone. Finally, we were unable to reliably collect data on intraoperative blood loss, hypotension, blood transfusion, total vasopressor use, diuretic administration and duration of surgery (Wilson et al. 2016). Thus, the results presented in this study should be taken as preliminary findings, which we believe warrant external validation through a prospective multicentre study.