Renal Histology Findings in Malignant Hypertension, a Systematic Review

BACKGROUND: Malignant hypertension (MH) causes acute target-organ injury (eyes, brain, heart, and kidneys). As kidney biopsy is seldom performed because of bleeding risk, the link between MH and renal histopathology-especially thrombotic microangiopathy-remains incompletely characterized. METHODS: We conducted a systematic review following PRISMA guidelines to analyze renal histological findings in adult patients with MH. Studies were included if they provided original data on MH and kidney histology in adult patients with MH. A comprehensive search across PubMed, Embase, Cochrane Library, and Web of Science identified eligible studies. Data extraction included demographics, clinical presentation, and histological findings. RESULTS: From 14 003 identified studies, 144 met the inclusion criteria, covering 1781 patients. In the pooled analysis, patients were predominantly men (67%) with an age of 38.4 (95% CI, 36.3-40.4). Serum creatinine was 587.8 µmol/L (95% CI, 511.2-664.4), and proteinuria was 4.3 g/g (95% CI, 2.8-5.8). Retinopathy-defined patients with MH (n=795) had worse renal damage and distinct histological patterns versus those without (n=871). Nephrosclerosis was present in 68.4% of biopsies, while 11.8% had IgA nephropathy, 6.9% focal segmental glomerulosclerosis, and 4.1% atypical hemolytic uremic syndrome. The pooled prevalence of hematologic thrombotic microangiopathy was 72.8% (95% CI, 54.3-85.8), and that of renal thrombotic microangiopathy was 95.2% (95% CI, 83.9-98.7), with increasing rates in recent decades. CONCLUSIONS: This review indicates that a third of patients with MH have other lesions than nephrosclerosis and that hematologic and renal thrombotic microangiopathy are present in two-thirds and almost all of patients, respectively. Further research into complement pathways and therapeutic targets is essential to improve prognosis and management.