Renal Biopsy in Patients with Unexplained Renal Impairment and Normal Kidney Size

SUMMARY We report renal biopsy findings in 109 patients with unexplainedrenal impairment (serum creatinine >0.15 mmol/1) and normal-sizednon-obstructed kidneys. The most common histological lesionswere interstitial nephritis, rapidly progressive glomerulonephritisand a variety of other types of glomerulonephritis. The groupscouldnot be distinguished by the presence or absence of hypertension,haematuria, proteinuria, or features of systemic disease. Howeverinterstitial nephritis was found more frequently in patientspresenting with one or none of these features and rapidly progressiveglomerulonephritis in patients presenting with three or more.All four patients with none of these features had interstitiallesions. Fifty-two per cent of patients with interstitial nephritisimproved and 60 per cent of the patients with rapidly progressiveglomerulonephritis who received immunosuppressive treatmentimproved or remained stable with treatment. The benefits ofa biopsy diagnosis were almost wholly confined to these twogroups. Complications were recorded in nine patients–prolongedmacroscopic haematuria in six and symptomatic perirenal heaematomatain three. Six required blood transfusion. One required nephrectomyto control haemorrhage and subsequently died. Percutaneous renalbiopsy is not without risk in patients with renal impairmentbut the benefits of diagnosing interstitial nephritis and rapidlyprogressive glomerulonephritis outweigh the disadvantages.