[Borderline indications for renal biopsy]

The Authors report 3 cases with clinical renal manifestations where the indication to perform a renal biopsy was defined as borderline. The uncertain indication was related to the clinical presentation, with a pattern of urinary abnormalities, such as isolated microscopic hematuria, microscopic hematuria associated with mild proteinuria, and isolated proteinuria. In addition, similar questions on biopsy are raised for chronic renal failure and elderly patients. In the literature, microscopic hematuria without significant proteinuria shows that 25% of adult patients have no histological abnormalities. A higher percentage is found among children. The other cases exhibit a pattern of IgA nephropathy, Alport's syndrome, thin BM nephropathy and arteriolar C3 deposition. The percentage of an abnormal histological picture increases if the patients have a family history of hematuria, and if there are concomitant episodes of macroscopic hematuria, because of an increase in IgA nephropathy and Alport's syndrome, respectively. In the last cases, therefore the indication to perform a renal biopsy increases. For those patients without these characteristics, a renal biopsy can be delayed whereas in cases of microscopic hematuria with proteinuria or isolated proteinuria the indication for a renal biopsy is stronger, because the spectrum of glomerulopathies is wider, and the possible evolution to renal failure after 10 years is higher (10-14% of cases). In patients with chronic renal failure the biopsy is contraindicated for cases where the thickness of the cortical section of the kidney is lower than 8-10 mm, because of possible technical difficulties, lower diagnostic information due to sclerosis and higher risk of complications. The prolonged bleeding time and the consequent risk of bleeding can be avoided by i.v. infusion of vasopressin 2 hours prior to biopsy. The higher indications are for those patients who may be susceptible to a medical treatment, capable to slowing down the progression of nephropathy. Finally, in elderly patients the biopsy is indicated in almost all cases because of the recently confirmed high incidence of glomerulopathies. In the aged there is a higher frequency of membranous GN, crescentic-ANCA associated GN, amyloidosis and, according to some Authors, post-infectious GN. In all cases a precise histological diagnosis can correct an erroneous diagnosis made according to clinical data alone. In the elderly the indication for biopsy aims at making an exact diagnosis of nephropathy, especially for acute renal failure: for this purpose age itself should not become an obstacle.