WHAT IS THE VALUE OF MEASURING RENAL PARENCHYMAL THICKNESS BEFORE RENAL BIOPSY

Reduced renal length is widely used to diagnose chronicity in patients with renal impairment. A length of 9 cm or less measured ultrasonogra phically is considered to indicate irreversible disease. However, some patients with normal renal length have thin parenchyma. The aim of th is study was to determine the relationship between ultrasonographicall y measured parenchymal thickness and renal length and to correlate par enchymal thickness with the histology obtained at renal biopsy. Sixty- four patients, aged 16-74 years, who had had a renal biopsy were evalu ated retrospectively. Histology was considered in five categories: I, interstitial nephritis (n=13); II, glomerulonephritis (28); III, diabe tes mellitus/metabolic/other (8); IV, chronic renal disease (CRD) (11) ; V, hypertension/vascular disease (4). There was a good linear correl ation between renal length and renal parenchymal thickness (r=0.64, P< 0.001). Both were reduced most in patients with CRD. Sixty-four per ce nt of patients with CRD had renal parenchymal thickness 1.5 cm or less , compared to 38% in group I, 25% in groups II and V, and 7% in group II. Although 11/37 (30%) of patients whose serum creatinine had increa sed 3 months post-biopsy had parenchymal thickness 1.5 cm or less, so did 6/27 (23%) whose creatinine decreased. Like renal length, parenchy mal thickness gives an indication of the chronicity of renal failure. However, some patients with parenchymal thickness 1.5 cm or less still have potential for improvement. This measurement alone should not be used to obviate renal biopsy.