We received a total of 1,094 renal biopsies during the study perios. A total of 87 [7.95%] were inadequate on LM but the tissue sent for IF showed renal cortex. In 69 (79.3%) cases, adequate material could be retrieved and a diagnosis made . In 18 cases (20.7%), the tissue retrieved after frozen sectioning was insufficient for diagnosis.
Distribution of cases diagnosed from frozen tissue
Of the 69 cases, a definite diagnosis could be offered in 65 cases. In the remaining four cases, a marked freezing artefact was seen producing morphological artefacts and a definitive diagnosis was not possible. These included two cases of acute tubular necrosis. Thus, by this method we could avoid a repeat biopsy in 74.7% of the inadequate biopsies.
The tissue so retrieved showed freezing-melting artefacts. However, the tissue was such that the glomerular pathology could be commented upon with fair degree of accuracy. Cases of diffuse proliferative glomerulonephritis (DPGN) and membranoproliferative glomerulonephritis (MPGN) could be diagnosed because of enlarged size of glomeruli and hypercellularity. Splitting of basement membrane was noted in cases of MPGN on Silver methenamine (SM) stain. In addition the IF findings in both these groups were characteristic. Thus LM and IF findings jointly helped in arriving at a definitive diagnosis. Lupus nephritis with presence of wire loop lesions, hyaline thrombi, and necrotizing lesions could be commented upon.
Crescents were also easily diagnosed. Spikes were identified in cases of membranous glomerulonephritis (MGN). The IF pattern in cases of MGN was also classical and helped to confirm the diagnosis. Amyloid deposits could be confirmed on special stains like Congo red under polarized microscope. Nodular glomerulosclerosis suggestive of diabetic nephropathy was corroborated with the clinical history. Cases of focal and segmental glomerulosclerosis could also be diagnosed, though with some difficulty.
However, the tubular pathology showed fair amount of freezing-melting artefact. Most of the tubules showed damage to the tubular epithelium and crush effect. Thus acute tubular injury could not be interpreted easily. The interstitium showed a glassy appearance and it was also difficult to comment upon the presence of chronic parenchymal damage. In cases of lupus nephritis, comments on activity and chronicity were also not possible.
A panel of photomicrographs of processed IF tissue, corresponding histochemical stains along with photomicrographs of formalin fixed tissues to compare the variation in morphology have been depicted in Figures –.
Figure 1 (a) Photomicrograph of formalin fixed tissue in a patient of minimal change disease [H and E, ×400]; (b) Photomicrograph of processed IF tissue [H and E, ×400]; (c) Jones’s silver stain of the case shown in B displaying unremarkable (more ...)
Figure 4 (a) Photomicrograph of formalin fixed tissue in a case of amyloidosis showing deposition of eosinophilic material along glomerular capillary loops [H and E, ×200]; (b) Photomicrograph of processed IF tissue showing amyloidosis (arrow) [H and E, (more ...)
Figure 2 (a) Photomicrograph of formalin fixed tissue in a patient of membranous glomerulonephritis displaying thickened basement membranes [PAS stain, ×400]; (b) Photomicrograph of processed IF tissue [H and E, ×200]; (c) Case shown in B with (more ...)
Figure 3 (a) Photomicrograph of formalin fixed tissue of a case of cortical infarct [H and E, ×100]; (b) and (c) Photomicrograph of processed IF tissue of a case of cortical infarct showing necrosed glomeruli (arrows) [H and E & PAS stain, ×100]; (more ...)