Original Article Severe acute kidney injury and multiple myeloma: Evaluation of kidney and patient prognostic factors Luís Rodrigues ⁎, Marta Neves, Helena Sá, Henrique Gomes, Jorge Pratas, Mário Campos Centro Hospitalar e Universitário de Coimbra, Praceta Prof. Mota Pinto, 3000-075 Coimbra, Portugal abstract article info Article history: Received 11 April 2014 Received in revised form 14 June 2014 Accepted 25 June 2014 Available online 15 July 2014 Keywords: Acute kidney injury Multiple myeloma Hemodialysis Prognosis Background: Patients with multiple myeloma (MM) manifesting acute kidney injury (AKI) and who later recover renal function and independence from renal replacement therapy (RRT) are considered to have a better outcome. The aim of this work was to study the factors associated with renal function recovery (independence of hemodi- alysis) and longer survival in these patients. Methods: A retrospective single center study including patients with a diagnosis of MM and severe AKI, defined as stage 3 of the Kidney Disease: Improving Global Outcomes (KDIGO) criteria: 3.0 times baseline increase in serum creatinine (sCr) or increase in sCr to ≥4.0 mg/dL or initiation of RRT, was conducted. Data was registry-based and collected between January 2000 and December 2011. We examined demographic and laboratorial data, present- ing clinical features, precipitating factors, need for RRT and chemotherapy. Death was considered the primary endpoint. Results: Lower serum β2-microglobulin was the only independent factor associated with recovery of renal function and independence of RRT (OR 0.95, 95% CI: 0.91–0.99, P = 0.02). The median survival after AKI was 10.7 ± 12.1 months. The factors associated with longer survival were independence of RRT (HR 2.21; 95% CI: 1.08–4.49; P = 0.02), lower CRP (HR 1.07; 95% CI: 1.03–1.12; P = 0.001) and younger age (HR 1.03; 95% CI: 1.01–1.06; P = 0.005). Conclusions: Our study suggests that MM patients with lower serum β2-microglobulin have a higher likelihood of recovering renal function after severe AKI. Independence of RRT, lower CRP and younger age are associated with longer survival. © 2014 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. 1. Introduction Multiple myeloma (MM) represents a plasma cell malignant disease leading to uncontrolled production of monoclonal immunoglobulins, accounting for 10% of all hematological malignancies [1,2]. The tumor, its products and the host response result in a number of organ dysfunc- tions of which lytic bone disease, hypercalcemia, anemia and kidney dysfunction compose the clinical picture. Acute kidney injury (AKI) is a common form of disease presentation and its basis yields an extensive differential diagnosis: pre-renal disease (hypovolemia, sepsis, use of non-steroidal anti-inflammatory drugs — NSAIDs), hypercalcemia, glomerular amyloid or non-amyloid deposits, cast nephropathy and in- frequent kidney infiltration by myeloma cells must all be considered. At diagnosis, 50% of patients show a serum creatinine (sCr) N 1.3 mg/dL, 15–20% have sCr N 2 mg/dL and 2–10% need renal replacement therapy (RRT) [3,4]. In the presence of severe AKI (defined generically as sCr N 4.0 mg/dL), recovery of renal function and independence of RRT are considered to have a better outcome than those remaining dialysis dependent [5–8]. Increased incidence of RRT due to end stage renal disease secondary to MM is noticeable and mean survival in these patients is 0.91 years vs. 4.46 years in patients without MM [9]. Our aim was to study the factors associated with renal function recovery (defined as independence of hemodialysis at discharge) and longer survival after severe AKI in MM patients. 2. Subjects and methods We conducted a retrospective registry-based single center study in patients admitted to the Nephrology Department of the Coimbra Uni- versity Hospitals and reviewed the medical records of all patients referred with severe AKI and the diagnosis of MM between January 2000 and December 2011 (12 years). The patients were identified through a search of our hospital's electronic database by cross- referencing these two diagnoses. Severe AKI was defined as stage 3 of the Kidney Disease: Improving Global Outcomes (KDIGO) criteria for staging AKI: 3.0 times baseline in- crease in sCr or increase in sCr to ≥ 4.0 mg/dL or urine output of European Journal of Internal Medicine 25 (2014) 652–656 ⁎ Corresponding author at: Rua Ântero de Quental, N110, 1°C, 3000-031 Coimbra, Portugal. Tel.: +351 965771436. E-mail addresses: luis.arodrigues@hotmail.com (L. Rodrigues), martaraq_neves@hotmail.com (M. Neves), helena.oliveirasa@sapo.pt (H. Sá), henriquevgomes@gmail.com (H. Gomes), jpratas.sousa@gmail.com (J. Pratas), mariocampos@huc.min-saude.pt (M. Campos). http://dx.doi.org/10.1016/j.ejim.2014.06.023 0953-6205/© 2014 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect European Journal of Internal Medicine journal homepage: www.elsevier.com/locate/ejim