Renal lesions in leptospirosis.

Renal function studies and kidney biopsies were performed in four patients presenting with renal insufficiency and acute Leptospira pomona infection. The renal lesion in all patients revealed acute interstitial nephritis. There was no evidence of immunologically mediated disease in three patients who were biopsied seven, eight and eight days respectively following the onset of symptoms. The fourth, in whom there was no evidence of prior renal disease, and whose biopsy was performed 16 days after symptoms began, showed glomerular Clq, and C3 immunofluorescence and mesangial, subepithelial and intramembranous dense deposits by electron microscopy. In addition, circulating immune complexes were demonstrated in this patient. These findings suggest that in this instance at least, the renal lesions of Leptospira pomona infections can be immunologically mediated. Because this may well be a transient phase, the timing of investigations could be crucial to its detection.