Onconephrology: The intersections between the kidney and cancer

Tumor cells from malignancies of any type-carcinoma, sarcoma, lymphoma, leukemia-may cause systemic arteriolar and capillary obstructions. The high shear rates of blood passing through these obstructions result in fragmentation of the red cells and can cause severe anemia, described as microangiopathic hemolytic anemia (MAHA).The thrombi caused by these obstructions consume platelets and can lead to severe thrombocytopenia. MAHA (defined by fragmented red cells on the peripheral blood smear and evidence of hemolysis) and thrombocytopenia are the clinical features of syndromes described as thrombotic microangiopathies (TMAs). If a malignancy is not recognized as the cause of TMA, the diagnosis of thrombotic thrombocytopenic purpura (TTP) may be considered and plasma exchange, the essential treatment for TTP, may be initiated-a critical decision because this treatment carries a high risk of serious complications. This review describes the clinical features that should suggest a search for systemic malignancy as the cause of unexpected MAHA and thrombocytopenia. Recognition of a systemic malignancy is critical to the initiation of appropriate chemotherapy and avoidance of inappropriate use of plasma exchange treatment.

Chronic renal failure is a common pathology. The high frequency of this disease in the general US population has been assessed in the NHANES III study. However, the frequency of chronic renal insufficiency among cancer patients remains unclear. 316 cancer patients were in a one-month study, included regardless of their pathology, treatment (antineoplastic drugs used or programmed to be used, pretreated, or no treatment), or any other criteria. Among the patients, 287 (90.8%) had normal serum creatinine levels (<110 micromol/l), i.e. a frequency of 9.2% for renal insufficiency in our population. However, when renal function was estimated by calculating creatinine clearance using the Cockcroft and Gault formula, 33% of the patients had an estimated GFR of less than 80 ml/min. Among these, 28% had a creatinine clearance ranging form 80 to 50 ml/min and 5% had a creatinine clearance of less than 50 ml/min. Renal insufficiency is frequent in cancer patients since almost one third of the patients present renal insufficiency. Furthermore, among patients with normal serum creatinine levels, one patient out of five has asymptomatic renal insufficiency. Therefore, it is of major importance that renal function be assessed by calculation of creatinine clearance using the Cockcroft and Gault formula in every patient, even when serum creatinine is within the normal range.