renal biopsy is a principal diagnostic method used by the nephrologist in the study of renal diseases . kidney biopsy is examined using light microscopy ( lm ) , immunofluorescence ( if ) , and electron microscopy . adequate tissue must be available for all the three techniques for a full and final answer to the clinical problem . despite improvement in biopsy techniques , many a times tissues sent for lm or it is a common practice to obtain one core and divide it into two for lm and if . as a result , where the tissue for if shows cortical tissue , while the tissue for lm shows only medulla , a repeat biopsy for lm might be needed . to overcome this problem , we practice a procedure of recovering tissue for lm from the if tissue once adequate number of frozen sections are obtained . this retrospective study was performed at the department of pathology , gb pant hospital between 2003 and 2011 . two cores of renal tissue were usually received , one in buffered formalin for lm and the other in michels medium for if . instead of simultaneously processing both the tissues , the tissue sample sent for lm was first processed and slides prepared were stained with haematoxylin and eosin ( h&e ) , stain to look for the presence of cortical tissue . if the tissue was adequate , i.e. , a minimum of seven glomeruli were present , it was processed for lm , but if the tissue had insufficient number of glomeruli , the sample sent for if was processed with care and salvaged as much as possible . for frozen sectioning , the tissue was washed three times for 10 min in wash buffer prepared by standard method . the tissue was then rapidly frozen at 25c and sectioned at 3  thickness . the sections were stained with h and e to identify cortical tissue . sections were picked up as soon as cortical tissue was identified rather than cutting deeper till full face of the tissue was exposed . routinely we pick up two sections per slide and cut about 20 slides upfront . in cases where the tissue for lm was inadequate , as soon as even one glomerulus was identified , sections were picked up for if . also , only one section was picked up per slide . about 15 such sections were prepared upfront and kept in the refrigerator for further processing . the remaining block with tissue was washed in wash buffer and the tissue was put in formalin for secondary fixation . 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 [ table 1 ] . 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 . thus , by this method we could avoid a repeat biopsy in 74.7% of the inadequate biopsies . 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 . . lupus nephritis with presence of wire loop lesions , hyaline thrombi , and necrotizing lesions could be commented upon . the if pattern in cases of mgn was also classical and helped to confirm the diagnosis . 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 . 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 14 . ( 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 basement membrane [ 200 ] ; ( d ) photomicrograph of formalin fixed tissue in a patient of fsgs [ pas stain 400 ] ; ( e ) photomicrograph of processed if tissue showing segmental sclerosis in the glomerular tuft , indicated by arrow [ h and e , 400 ] ; ( f ) same highlighted by mt stain [ 400 ] ( 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 spikes being appreciated ( arrow ) [ sm stain 400 ] ; ( d ) photomicrograph of formalin fixed tissue in a patient of crescentic glomerulonephritis , with cellular crescent [ h and e , 200 ] ; ( e ) photomicrograph of processed if tissue with fibrocellular crescent indicated by arrow [ h and e , 200 ] ; ( f ) crescent better highlighted on pas stain [ 200 ] ( 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 ] ; ( d ) photomicrograph of formalin fixed tissue of a case of diabetic nephropathy [ pas stain 200 ] ; ( e ) photomicrograph of processed if tissue showing nodular glomerulosclerosis [ kw lesion ( arrow ) ] [ pas stain 200 ] ; ( f ) photomicrograph of mesangioproliferative glomerulonephritis displaying increase in mesangial matrix and cellularity [ h and e , 400 ] ( 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 , 400 ] ; ( c ) amyloid showing apple green birefringence under polarized light ; ( d ) photomicrograph of formalin fixed tissue showing features of acute tubular necrosis ( arrow ) [ h and e , 100 ] ; ( e ) and ( f ) photomicrographs showing poor tubular morphology and degenerative changes in tubular epithelial cells [ h&e & pas stains respectively , 200 ] performing renal biopsy is a hazardous procedure in the best of hands involving a fair degree of morbidity and mortality varying from 2.4% to 23.7% in different centers.[24 ] international guidelines have been fixed on the processing and evaluation of kidney biopsies to enable proper interpretation of the findings . the histomorphology is poorly preserved in comparison with that observed in a tissue fixed in buffered formalin as soon as it is biopsied . however , the glomerular pathology can be commented upon with a fair degree of accuracy thus avoiding a repeat biopsy . as seen in this study , we could diagnose cases of dpgn , mpgn and minimal change disease ( mcd ) . however , due to fixation artefact , tubular pathology and acute tubular necrosis could not be interpreted properly . degree of chronic parenchymal damage also could not be commented upon due to marked fixation artefact in the tubulo - interstitial compartment . in addition , the degree of activity and chronicity in lupus nephritis could not be commented upon . the if tissue can be evaluated only after the lm tissue is processed , resulting in a delay in the processing of the if tissue by 24 h. however , this small delay could be acceptable in comparison with a repeat invasive kidney biopsy . in some centers a small portion of the cortex from the single core biopsy is processed for if before fixing the remaining core in formalin , with a view to avoid taking two cores of tissue and decrease the incidence of complications . however , in our experience , often this small bit of cortical tissue for if is difficult to handle , especially by a poorly trained technician . on the other hand , processing two separate cores may yield adequate tissue for if , which might provide accurate insight into the primary etiology of the disease and subsequent treatment . moreover it may be helpful in instances when the formalin fixed tissue is inadequate for interpretation and the if tissue may be require processing in formalin for more definite opinion . in despite the degree of fixation artefact obtained when retrieving if tissue for lm , the quality of tissue was such that the glomerular pathology could be identified in large percentage ( 74.7% ) of cases and a repeat kidney biopsy had been avoided .
we highlight a method that is helpful in situations where the tissue sent for lm is inadequate whereas the tissue sent for if showed glomeruli useful for interpretation . 
 we utilized the leftover frozen tissue after the sections for if were taken . 
 this tissue was post - fixed in formalin for the purpose of light microscopic diagnosis . 
 the glomerular pathology could be commented upon with a fair degree of accuracy and a repeat biopsy was avoided in 74.7% of the cases . however , the tubules showed marked fixation artefact and tubular pathology was distorted . 
 this procedure can help to reach a correct diagnosis in large percentage of cases otherwise labeled as inadequate biopsy and hence , save the patient from the trauma of a repeat biopsy .