Urinary albumin excretion: a predictor of glomerular findings in adults with microscopic haematuria.

BACKGROUND: Microscopic haematuria without proteinuria is a common clinical finding. When urological causes are excluded, usual findings on renal biopsy are IgA nephropathy (which can progress to end-stage renal failure) or thin basement membrane nephropathy (which has an excellent prognosis). A non-invasive test to discriminate between the two would be useful. AIM: To examine the value of measurement of urinary albumin excretion in discriminating glomerular causes of microscopic haematuria in patients without proteinuria on urine dipstick tests. DESIGN: Single-centre retrospective cross-sectional observational study. METHODS: Adult patients who underwent renal biopsy for microscopic haematuria over a 6-year period from January 1994 were identified. Study entry required normal renal function, no proteinuria detected by dipstick, and urinary albumin excretion <300 mg/24 h. Patients with IgA nephropathy had follow-up for a mean of 58 months after biopsy. RESULTS: Of 169 patients fulfilling study criteria, 119 (70%) had normoalbuminuria (<30 mg/24 h); 52 (30%) had microalbuminuria (30-299 mg/24 h). Of those with normoalbuminuria, 106 (89%) had thin basement membrane nephropathy or no glomerular abnormality. Thirteen (11%) had IgA nephropathy, and of 12 of these followed-up for a mean 64 months, none developed overt, dipstick-positive proteinuria. In contrast, 24 (48%) of those with microalbuminuria had IgA nephropathy, and of 22 followed-up for a mean 55 months, five developed overt proteinuria. DISCUSSION: Urinary albumin excretion is an indicator of likely glomerular findings in microscopic haematuria, and may influence whether a renal biopsy is necessary.

Atherosclerotic renal artery stenosis: is it worth diagnosing?

Atherosclerotic renal artery stenosis (ARAS) is the commonest cause of secondary hypertension and is the cause of end stage renal failure in up to 20% of patients starting dialysis. Associated with it is a high morbidity and appalling mortality. The aetiology of ischaemic nephropathy is complex and is not simply related to renal artery narrowing. Captopril renography is sensitive and specific for diagnosing ARAS in patients with normal renal function. In those with renal impairment gadolinium-enhanced MRA or spiral CT angiography clearly define renal anatomy. Over 80% of ARAS is ostial. Studies of revascularisation with angioplasty show poor short and long term patency rates. Renal artery stenting leads to high initial technical success and long term patency. Recent randomised controlled trials in patients with renovascular hypertension demonstrate no clear benefit of adequate revascularisation over medical therapy. Renal artery stenting for renal protection in ARAS appears more encouraging and current randomised controlled trials are in progress to answer the question definitively.

The relationship between albuminuria, MCP-1/CCL2, and interstitial macrophages in chronic kidney disease.

Glomerular-derived proteins may activate tubular cells to express the macrophage-directed chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2). Macrophages at interstitial sites have a central role in directing renal scarring. We have prospectively assessed the relationship between albuminuria, urinary MCP-1/CCL2, interstitial macrophage infiltration, in situ damage, and clinical outcomes in a large group of patients with chronic kidney disease. We studied 215 patients and quantified albumin-creatinine ratio (ACR), urinary MCP-1/CCL2, interstitial macrophage numbers, and in situ damage. ACR correlated with urinary MCP-1/CCL2 (correlation 0.499; P<0.001), interstitial macrophage numbers (correlation 0.481; P<0.001), and index of chronic damage (correlation 0.363; P<0.001). Macrophage numbers closely correlated with in situ damage (correlation 0.755; P<0.001). By multivariate analysis ACR, urinary MCP-1/CCL2, and interstitial macrophage numbers were interdependent. By Kaplan-Meier survival analysis albuminuria, urinary MCP-1/CCL2, interstitial macrophages, and chronic damage predict the outcome. ACR, macrophage numbers, chronic damage, and creatinine independently predicted renal survival. The association of ACR with other variables was strongest in patients with less advanced disease states. There is a close association between albuminuria, urinary MCP-1/CCL2, and interstitial macrophage infiltration with in situ damage and clinical outcomes. These findings support the hypothesis that albuminuria triggers tubular MCP-1/CCL2 expression with subsequent macrophage infiltration. These processes may represent the dominant pathway for the progression of renal injury before the establishment of advanced renal scarring.