Integrating Modified National Early Warning Score 2, computed tomography staging, and laboratory markers for enhanced prognostic stratification in emphysematous pyelonephritis

Abstract

Emphysematous pyelonephritis (EPN) is a rare but life-threatening urological emergency with no universally accepted management protocol. The Modified National Early Warning Score 2 (mNEWS2), derived exclusively from six physiological parameters, has recently been proposed as a reliable tool for predicting treatment outcomes in EPN. Although higher mNEWS2 scores are associated with increased morbidity and mortality, clinical deterioration typically manifests only after substantial disease progression. In contrast, computed tomography-based classification systems and laboratory parameters - such as anemia, leukocytosis, thrombocytopenia, and hyperglycemia - may offer earlier prognostic insights before physiological deterioration occurs. Evidence from recent multicenter studies has identified these factors as independent predictors of mortality. Therefore, integrating mNEWS2 with computed tomography-based staging and relevant laboratory markers may allow more accurate risk stratification and facilitate timely decision-making, including consideration of early nephrectomy in high-risk patients with extensive paranephric involvement, ultimately improving clinical outcomes in EPN management.

Key Words: Emphysematous pyelonephritis; Modified National Early Warning Score 2; Computed tomography classification; Prognostic factors; Nephrectomy

Core Tip: Emphysematous pyelonephritis is a rapidly progressive and life-threatening infection that necessitates timely and precise prognostic evaluation. Although the Modified National Early Warning Score 2 provides valuable risk information based exclusively on physiological parameters, clinical deterioration typically manifests at a relatively advanced stage. In contrast, computed tomography based staging and critical laboratory indicators, including anemia, thrombocytopenia, leukocytosis, and hyperglycemia, may yield earlier prognostic insights before overt vital-sign abnormalities develop. A combined assessment incorporating Modified National Early Warning Score 2, computed tomography classification, and laboratory indicators may therefore improve early risk stratification, inform timely nephrectomy decisions in high-risk patients, and ultimately optimize clinical outcomes.

TO THE EDITOR

We have read with great interest the article by Krishnamoorthy et al[1], The Modified National Early Warning Score 2 (mNEWS2), based on six physiological parameters (respiratory rate, oxygen saturation, systolic blood pressure, pulse rate, level of consciousness, and body temperature), stratifies patients into three groups, enabling more individualized management. Patients in group 1 were treated conservatively, but patients in groups 2 and 3 needed more frequent procedures like percutaneous drainage or nephrostomy. Half of the patients in group 3 had an early nephrectomy. A cutoff score ≥ 15 showed high prognostic accuracy (sensitivity 87.5%, specificity 96.9%, accuracy 96.5%). The authors concluded that mNEWS2 improved risk stratification and supports timely treatment decisions in emphysematous pyelonephritis (EPN)[1]. However, it should be emphasized that this study employed a retrospective design and included a relatively small cohort, thereby limiting the robustness and external validity of its findings. Additional validation via extensive, prospective, and multicenter studies is necessary to corroborate these findings.

As the authors mention, no standardized protocol exists for EPN management, making prognostic scoring vital for identifying high-risk patients and guiding therapy. The computed tomography (CT)-based classification first proposed in 2000 remains widely used for its prognostic value[2]. It defines class 1 as gas confined to the collecting system, class 2 as parenchymal gas without extrarenal spread, class 3A as perinephric, class 3B as pararenal extension, and class 4 as bilateral disease or involvement of a solitary kidney. Increasing class severity correlates with rising morbidity and mortality, with class 4 carrying the poorest prognosis.

In a recent multicenter study, independent predictors of mortality identified by multivariable logistic regression included a quick Sepsis-related Organ Failure Assessment score ≥ 2, anemia, paranephric gas extension, leukocytosis, thrombocytopenia, and hyperglycemia[3]. In this condition, thrombocytopenia may reflect sepsis-induced coagulopathy and platelet consumption, anemia correlates with systemic inflammation and reduced renal perfusion, and hyperglycemia signifies both metabolic stress and bacterial proliferation in glucose-rich environments. In the presented study, the mNEWS2 score is derived exclusively from vital parameters. While it is logical that once vital signs begin to deteriorate, the risk of adverse outcomes rises substantially - explaining the high diagnostic performance of the score - the critical issue lies in anticipating a prognosis at an earlier stage and identifying patients who may require an early nephrectomy. Laboratory abnormalities may develop in some patients before they affect their vital signs. For instance, a patient presenting with marked paranephric gas on CT and laboratory abnormalities such as thrombocytopenia and hyperglycemia may initially appear hemodynamically stable, yet be at high risk of rapid deterioration if managed conservatively. Therefore, integrating CT-based classification with selected laboratory markers could provide more accurate and timely guidance for intervention before significant physiological deterioration occurs. Future studies could prospectively validate a composite risk model combining mNEWS2, CT findings, and laboratory parameters to determine predictive accuracy and clinical applicability. Conceptually, these tools could be applied sequentially in clinical decision-making: MNEWS2 for initial triage, followed by CT and laboratory assessment for refined prognostic stratification. Such a sequential or potentially composite approach could guide early nephrectomy decisions in patients with extensive paranephric involvement or multiorgan dysfunction.

In conclusion, even in cases where the mNEWS2 score is not markedly elevated, patients presenting with advanced gas formation on CT (class 3B or higher), along with anemia, thrombocytopenia, leukocytosis, and hyperglycemia, should be considered for early nephrectomy. Not taking action at this point could lead to permanent damage and a higher death rate. Early identification of these high-risk features can therefore support timely and individualized management, potentially improving survival outcomes in EPN.