Chapter A3: Atlas of Urinary Sediments and Renal Biopsies

Minimal change disease. In minimal change disease, light microscopy is unremarkable (A), whereas electron microscopy (B) reveals podocyte injury evidenced by complete foot process effacement. (ABF/Vanderbilt Collection.)

Focal segmental glomerulosclerosis (FSGS). There is a well-defined segmental increase in matrix and obliteration of capillary loops in the right part of the glomerulus, the sine qua non of segmental sclerosis not otherwise specified (NOS) type. (ABF/Vanderbilt Collection.)

Collapsing glomerulopathy. There is segmental collapse (arrow) of the glomerular capillary loops and overlying podocyte hyperplasia. This lesion may be idiopathic or associated with e.g., HIV infection and has a particularly poor prognosis. (ABF/Vanderbilt Collection.)

Hilar variant of FSGS. There is segmental sclerosis of the glomerular tuft at the vascular pole with associated hyalinosis, also present in the afferent arteriole (arrows). This lesion often occurs as a secondary response when nephron mass is lost due to, e.g., scarring from other conditions. Patients usually have less proteinuria and less steroid response than FSGS, NOS type. (ABF/Vanderbilt Collection.)

Tip lesion variant of FSGS. There is segmental sclerosis of the glomerular capillary loops at the proximal tubular outlet (arrow). This lesion has a better prognosis than other types of FSGS. (ABF/Vanderbilt Collection.)

Postinfectious (poststreptococcal) glomerulonephritis. The glomerular tuft shows proliferative changes with numerous polymorphonuclear leukocytes (PMNs), with a crescentic reaction (arrow) in severe cases (A). These deposits localize in the mesangium and along the capillary wall in a subepithelial pattern and stain dominantly for C3 and to a lesser extent for IgG (B). Subepithelial hump-shaped deposits are seen by electron microscopy (arrow) (C). (ABF/Vanderbilt Collection.)

Membranous nephropathy. Membranous nephropathy is due to subepithelial deposits, with resulting basement membrane reaction, resulting in the appearance of spike-like projections on silver stain (A). The deposits are directly visualized by fluorescent anti-IgG, revealing diffuse granular capillary loop staining (B). By electron microscopy, the subepithelial location of the deposits and early surrounding basement membrane reaction are evident, with overlying foot process effacement (C). Most cases of primary membranous nephropathy are due to autoantibodies to the phospholipase A2 receptor (PLA2R), which is present on podocytes, and this antigen can then be detected in the deposits by staining with anti-PLA2R antibody (D). (ABF/Vanderbilt Collection.)

IgA nephropathy. There is variable mesangial expansion due to mesangial deposits, with some cases also showing endocapillary hypercellularity or segmental sclerosis (A). By immunofluorescence, mesangial IgA deposits are evident (B). (ABF/Vanderbilt Collection.)

Membranoproliferative glomerulonephritis. There is mesangial expansion and endocapillary hypercellularity with cellular interposition in response to subendothelial deposits, resulting in the “tram-track” of duplication of glomerular basement membrane. (EGN/UPenn Collection.)

Dense deposit disease (membranoproliferative glomerulonephritis type II). By light microscopy, there is a membranoproliferative pattern. By electron microscopy, there is a dense transformation of the glomerular basement membrane with round, globular deposits within the mesangium. By immunofluorescence, only C3 staining is usually present. Dense deposit disease is part of the group of renal diseases called C3 glomerulopathy, related to underlying complement dysregulation. (ABF/Vanderbilt Collection.)

C3 glomerulonephritis. By light microscopy, there is a membranoproliferative pattern. C3 glomerulonephritis is part of the group of renal diseases called C3 glomerulopathy, related to underlying complement dysregulation. (ABF/Vanderbilt Collection.)

C3 glomerulonephritis. By immunofluorescence, only C3 staining is usually present, with occasional minimal immunoglobulin, in an irregular capillary wall and mesangial distribution. (ABF/Vanderbilt Collection.)

C3 glomerulonephritis. By electron microscopy, usual density deposits are present (arrows), including mesangial, subendothelial, and occasional hump-type subepithelial deposits. (ABF/ Vanderbilt Collection.)

Lupus nephritis with mixed proliferative and membranous glomerulonephritis lesions. This specimen shows pink subepithelial deposits with spike reaction, and the “tram-track” sign of duplication of glomerular basement membrane, resulting from subendothelial deposits, as may be seen in mixed membranous and focal or diffuse lupus nephritis (International Society of Nephrology [ISN]/Renal Pathology Society [RPS] class V combined with class III or IV) Segmental endocapillary and mesangial hypercellularity are evident, along with spikes (lower arrow) and segmental double contours of the glomerular basement membrane (top arrow). A small cellular crescent is present at 6 o’clock. (EGN/UPenn Collection/ABF/Vanderbilt Collection.)

Lupus nephritis. Proliferative lupus nephritis, ISN/RPS class III (focal) or IV (diffuse), manifests as endocapillary hypercellularity, which may result in segmental necrosis due to deposits, particularly in the subendothelial area (A). By immunofluorescence, chunky irregular mesangial and capillary loop deposits are evident, with some of the peripheral loop deposits having a smooth, molded outer contour due to their subendothelial location. These deposits typically stain for all three immunoglobulins, IgG, IgA, IgM, and both C3 and C1q (B). By electron microscopy, subendothelial (arrow), mesangial (white rim arrowhead), and rare subepithelial (black arrowhead) immune complex deposits are evident, along with extensive foot process effacement (C). (ABF/Vanderbilt Collection.)

Granulomatosis with polyangiitis (Wegener’s granulomatosis). This pauci-immune necrotizing crescentic glomerulonephritis shows numerous breaks in the glomerular basement membrane with associated segmental fibrinoid necrosis and a crescent formed by proliferation of the parietal epithelium. Note that the uninvolved segment of the glomerulus (at ~5 o’clock) shows no evidence of proliferation or immune complexes. (ABF/Vanderbilt Collection.)

Anti–glomerular basement membrane antibody-mediated glomerulonephritis. There is segmental necrosis with a break of the glomerular basement membrane (arrow) and a cellular crescent (A), and immunofluorescence for IgG shows linear staining of the glomerular basement membrane with a small crescent at ~1 o’clock (B). (ABF/Vanderbilt Collection.)

Amyloidosis. Amyloidosis shows amorphous, acellular expansion of the mesangium, with material often also infiltrating glomerular basement membranes, vessels, and the interstitium, with apple-green birefringence by polarized Congo red stain (A). The deposits are composed of randomly organized 9–11 nm fibrils by electron microscopy (B). (ABF/Vanderbilt Collection.)

Light chain deposition disease. There is mesangial expansion, often nodular by light microscopy (A), with immunofluorescence showing monoclonal light chain staining, more commonly with kappa than lambda light chain, of tubules (B) and glomerular tufts. By electron microscopy (C), the deposits show an amorphous granular appearance and line the inside of the glomerular basement membrane (arrows) and are also found along the tubular basement membranes. (ABF/Vanderbilt Collection.)

Light chain cast nephropathy (myeloma kidney). Monoclonal light chains precipitate in tubules and result in a syncytial giant cell reaction surrounding the casts and a surrounding chronic interstitial nephritis with tubulointerstitial fibrosis. (ABF/Vanderbilt Collection.)

Fabry’s disease. Due to deficiency of α-galactosidase, there is abnormal accumulation of glycolipids, resulting in foamy podocytes by light microscopy (A). These deposits can be directly visualized by electron microscopy (B), where the glycosphingolipid appears as whorled so-called myeloid bodies, particularly in the podocytes. (ABF/Vanderbilt Collection.)

Alport’s syndrome and thin glomerular basement membrane lesion. In Alport’s syndrome, there is irregular thinning alternating with thickened so-called basket-weaving abnormal organization of the glomerular basement membrane (A). In benign familial hematuria (often due to a carrier state of autosomal recessive Alport), or in early cases of Alport’s syndrome or female carriers, only extensive thinning of the glomerular basement membrane is seen by electron microscopy (B). (ABF/Vanderbilt Collection.)

Diabetic nephropathy. In the earliest stage of diabetic nephropathy, only mild mesangial increase and prominent glomerular basement membranes (confirmed to be thickened by electron microscopy) are present (A). In slightly more advanced stages, more marked mesangial expansion with early nodule formation develops, with evident arteriolar hyaline (B). In established diabetic nephropathy, there is nodular mesangial expansion, so-called Kimmelstiel-Wilson nodules, with increased mesangial matrix and cellularity, microaneurysm formation in the glomerulus on the left, and prominent glomerular basement membranes without evidence of immune deposits and with hyalinosis of both afferent and efferent arterioles (C). (ABF/Vanderbilt Collection.)

Arterionephrosclerosis. Hypertension-associated injury often manifests extensive global sclerosis of glomeruli, with accompanying and proportional tubulointerstitial fibrosis and pericapsular fibrosis, and there may be segmental glomerulosclerosis (A). The vessels show disproportionately severe changes of intimal fibrosis, medial hypertrophy, and arteriolar hyaline deposits (B). (ABF/Vanderbilt Collection.)

Cholesterol emboli. Cholesterol emboli cause cleft-like spaces (arrow) where the lipid has been extracted during processing, with smooth outer contours and surrounding fibrotic and mononuclear cell reaction in these arterioles. (ABF/Vanderbilt Collection.)

Thrombotic microangiopathy. This is the classic lesion in hemolytic uremic syndrome, with characteristic intraglomerular fibrin thrombi, with a chunky pink appearance (arrow). The remaining portion of the capillary tuft shows corrugation of the glomerular basement membrane due to ischemia. (ABF/Vanderbilt Collection.)

Systemic scleroderma. Acutely, there is fibrinoid necrosis of interlobular and larger vessels, with intervening normal vessels and ischemic change in the glomeruli, manifest by corrugation of the glomerular basement membranes (A). Chronically, this injury leads to intimal proliferation, the so-called onion-skinning appearance (B). (ABF/Vanderbilt Collection.)

Acute pyelonephritis. There are characteristic intratubular plugs and casts of polymorphonuclear neutrophils (PMNs) (arrow) with inflammation extending into the surrounding interstitium and accompanying tubular injury. (ABF/Vanderbilt Collection.)

Acute tubular injury. There is extensive flattening of the tubular epithelium and loss of the brush border, with mild interstitial edema, characteristic of acute tubular injury due to ischemia. (ABF/Vanderbilt Collection.)

Acute interstitial nephritis. There is extensive interstitial lymphoplasmocytic infiltrate with mild edema and associated tubular injury (A), which is frequently associated with interstitial eosinophils (B) when caused by a drug hypersensitivity reaction. (ABF/Vanderbilt Collection.)

Oxalosis. Calcium oxalate crystals have caused extensive tubular injury, with flattening and regeneration of tubular epithelium (A). Crystals are well visualized as sheaves when viewed under polarized light (B). (ABF/Vanderbilt Collection.)

Acute phosphate nephropathy. There is extensive acute tubular injury with intratubular nonpolarizable calcium phosphate crystals. (ABF/Vanderbilt Collection.)

Sarcoidosis. There is chronic interstitial nephritis with numerous, confluent, nonnecrotizing granulomas. The glomeruli are unremarkable, but there is moderate tubular atrophy and interstitial fibrosis. (ABF/Vanderbilt Collection.)

Hyaline cast. (ABF/Vanderbilt Collection.)

Coarse granular cast. (ABF/Vanderbilt Collection.)

Fine granular casts. (ABF/Vanderbilt Collection.)

Red blood cell cast. (ABF/Vanderbilt Collection.)

White blood cell cast. (ABF/Vanderbilt Collection.)

Triple phosphate crystals. (ABF/Vanderbilt Collection.)

“Maltese cross” formation in an oval fat body. (ABF/Vanderbilt Collection.)

Uric acid crystals. (ABF/Vanderbilt Collection.)