CRP-46

CRP-46

Clinical History

Diabetes mellitus with retinopathy, hyperlipidemia, acute renal failure. Gastric bypass 4 months ago. Serum creatinine had increased from 1.8 at the time of surgery to 8.1 two months later. However, the elevated creatinine was not noted at that time and she subsequently took NSAIDs. Two months later her creatinine had risen to 11.

Gross Description

Received in transport media are two cores measuring 4 and 12 mm in length and 2 mm in diameter. Four 1-mm pieces are taken for EM. The larger core is bisected and equally divided for immunofluorescence and light microscopy. The remaining tissue is submitted for light microscopy.

Pathology

Case CRP-046 PASH

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

Sections contain two fragments of renal cortex and one fragment of medulla. A total of thirty glomeruli are examined in the three levels. Twenty-two of these are globally sclerotic, and the remaining glomeruli show marked increase in mesangial matrix with occasional Kimmelstiel-Wilson nodules. There is mild mesangial hypercellularity. The glomerular basement membranes appear diffusely thickened. PASH and trichrome stains show diffuse, moderately severe interstitial fibrosis and tubular atrophy. However, in addition to the chronic tubulointerstitial injury, there is also extensive acute tubular necrosis, and examination of the tissue with polarized light reveals large numbers of oxalate crystals in the tubular epithelium as well as within the tubular lumina. There is patchy mild interstitial inflammation associated with the severe tubular injury. There is severe hyaline arteriolosclerosis.

Immunofluorescence

There are three glomeruli in the sections. There is diffuse 3+ linear staining for IgG and albumin along the glomerular basement membranes. There is no glomerular staining for IgM, IgA, C3 or light chains. There is 2+ focal and segmental staining for Clq in the mesangium. There is 3+ linear staining for IgG and albumin along the tubular basement membranes. There is 2+ staining for C3 in the arterioles.

Electron Microscopy

Three thick sections are available, but there is only one glomerulus. Ultrastructural examination confirms marked increase in mesangial matrix and diffuse thickening of the glomerular basement membranes. Most of the capillary loops are denuded. No immune complex deposits are identified. The tubular epithelium shows acute degenerative changes, and occasional crystals are noted in tubular epithelial cell cytoplasm as well as within the tubular lumina.

Diagnosis and Comments

Kidney, needle biopsy - Diabetic nephropathy.

- Oxalosis with severe acute and chronic tubular injury.

This is a very unusual biopsy, which shows two distinct lesions. The first is advanced diabetic nephropathy, with extensive glomerular sclerosis and interstitial fibrosis. However, there is also extensive calcium oxalate deposition, presumably secondary to her gastric bypass five months ago, which has caused severe acute and chronic tubular injury The extent of glomerulosclerosis and tubulointerstitial scarring suggests that significant recovery of renal function is very unlikely.

Renal failure is the severe reduction of renal function and often leads to reduced urinary output.