Medical kidney diseases

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This article describes medical renal disease or the medical kidney. Much in medical kidney depends on the clinical information. Most of the disease seen by pathologists is... glomerular disease. If in doubt... the answer to most questions is diabetes mellitus or systemic lupus erythematosus. Medical kidney is niche area in pathology. It is one of the few areas that routinely requires electron microscopy.

Kidney tumours are dealt with in the kidney tumours article.

Clinical

Glomerular filtration rate

  • Abbreviated GFR.
  • Ultimate measure of renal function.
  • Declines with age.
  • Normal range (dependent on age): 116-75 mL/min/1.73m2.[1]

Creatinine

  • The standard screening test for renal function.
  • 300 mmol/L is the general cut-point for referral to a nephrologist.[2]

Notes:

  • Dinosaurs use the units mg/dL; normal with these units is: 0.8 to 1.4 mg/dL.[3]
  • Conversion: 1.0 mg/dL = 88.4 umol/L.[4][5]

Urine protein to creatinine ratio

  • Indicator of proteinuria.
  • Predictor of glomerular filtration rate.[6]

Cut points:[7]

  • Normal (2 years and older): <0.2 g protein / g Creatinine
  • Nephrotic range: >3.5 g protein / g Creatinine.

Urine dip

Findings:[8]

  • RBC casts = acute bleed, e.g. nephritic syndrome.
  • WBC casts = interstitial nephritis, e.g. pylonephritis, parenchymal infection.
  • Hemegranular casts = acute tubular necrosis, transplant rejection.

Urine crystals

Clinical presentations

Nephrotic syndrome

Features:

  • Anasarca (whole body - edema).
  • Proteinuria (>3.5 g/24h).
  • Hypercholesterolemia.
  • Hypoalbuminemia.

Nephritic syndrome

Features - mnemonic PHAROH:[9]

  • Proteinuria.
  • Hypertension.
  • Azotemia.
  • RBC casts.
  • Oliguria.
  • Hematuria.

Mixed

  • Features of nephritic syndrome and nephrotic syndrome.

Normal

Epithelium[10]

  • The glomeruli visceral epithelium is part of the capillary wall (part of the glomerular tuft).
  • The parietal epithelium is part of Bowman's capsule.

Remember: visceral has vessels.

Basic approach to renal biopsy

Comment on:

  • Glomeruli.
  • Tubules.
  • Interstitium.
  • Vessels.

Glomeruli

  1. Mesangium
    • Matrix should be: "1 cell thick" (expanded in diabetes mellitus).
    • Cellularity of the mesangium - normal = upto 3 cells (don't count cell abutting the capillary lumen).
  2. Capillary loops "open"
    • Lumina patent? If not patent is it due to matrix or cells (endocapillary hypercellularity).
    • Capillary wall morphology - wavy thin is normal; hulla-hoop/wire-like abnormal (suggestive of immune complex deposition).
  3. Bowman's space (urinary space) - crescents present?
  • Count the number of glomeruli.
  • Count number of the obsolete glomeruli.

Components of the glomeruli (anatomical)

  • Podocyte - rarely affect by disease
    • One notable disease is collapsing glomerulopathy in HIV.[11]
  • Endothelial cell.
  • Mesangial cell.

Vessels

  1. Arteriolar hyalinosis - too much pink stuff???
  2. Intimal hyperplasia.

Consider:

  • Vasculitis? - inflammatory cells in vessel wall.
  • Amyloid? - pink.
  • Rejection? - PMNs.

Tubules & interstitium

Tubules - proximal portion is the most important.

  • Casts?
  • Necrosis?

Interstitium

  • Fibrosis - prognostically important.
    • Grading: mild = <25%, moderate 25-50%, severe >50%.

Important terms/process related

Obsolete glomeruli

  • Completely sclerosed glomeruli are not important - unless present in larger numbers than expected for the age of the patient.
Percent of sclerosed glomeruli = (age in years)/2 - 10%.[12]

Example:

  • It is normal for an 80 year-old to have 30% sclerosed glomeruli.

Glomerular disease terms[13]

  • Global = >50% of glomeruli.
  • Focal = <50% of glomeruli.
  • Segmental = part of glomerulus.
  • Diffuse = most of glomerulus.

Staining

The standard stain in kidney pathology is PAS. Section are usually 1-2 micrometers, as opposed to 4-5 micrometers seen in rountine section of other organs.

Interpretation of medical renal disease more difficult or even impossible if the sections are thicker, as one does not see the glomerular structures well.

In kidney that is cut thick the glomeruli look more nodular and it is more difficult to find open capillary loops.

Immunofluorescence

Routinue (mnemonic GAM CF):

  • IgG.
  • IgA.
  • IgM.
  • C3.
  • Fibrinogen.

Optional:

  • Kappa.
  • Lambda.

Immune complex-related disease

Can be:

  • Subepithelial - distal to basement membrane (BM).
  • Subendothelial - proximal to BM.

Tram-tracking of BM

DDx:[14]

  1. MPGN.
  2. Thrombotic microscopic angiopathy (TMA).
  3. Transplant glomerulopathy (TG).

Arteriolar hyalinosis

DDx:

  • Diabetes mellitus.
  • Hypertension.
  • Aging.
  • Drugs - tarolimus, cyclosporine.

Note:

  • Arteriolar hyalinosis - involves afferent and efferent arterioles in diabetes, in others it is only tha afferent.

Mesangial hypercellularity

Think:

  1. Lupus.
  2. IgA nephropathy.

Mesangial expansion

  • Diabetes mellitus.[15]
  • Immune complex mediated disease (e.g. IgA nephropathy).
  • Henoch-Schoenlein disease.
  • Lupus.

Pathologic DDx

The clinical presentations suggest a pathologic DDx.[16]

Nephritic

  • Post-infectious glomerulonephritis,
    • Classically streptococcal
  • Crescentic glomerulonephritis (AKA rapidly progressive glomerulonephritis (RPGN)),
    • Anti-GBM disease,
    • ANCA disease (e.g. Wegener's granulomatosis),
    • Goodpasture's syndrome.

Nephrotic

  • Minimal segmental disease (MSD) - AKA minimal change disease (MCD),
  • Focal segmental glomerulosclerosis (FSGS),
  • Membranous nephropathy.

Mixed presentation

  • IgA nephropathy,
  • Focal proliferative glomerulosclerosis (FPGS),
  • Membranoproliferative glomerulonephritis (MPGN).

Patterns - Table

Pattern Key feature Other findings EM Clinical Pathol. DDx Image
Nodular GS Key feature? Other findings? EM? Clinical? Pathol. DDx? Image?
Focal segmental GS (FSGS) Key feature? Other findings? EM? Clinical? Pathol. DDx? Image?
Minimal change disease (MCD) Key feature? Other findings? EM? Clinical? Pathol. DDx? Image?
Rapidly progressive GN (RPGN) Key feature? Other findings? EM? Clinical? Pathol. DDx? Image?

Nephrotic syndrome

A broad classification of nephrotic syndrome based on etiology:

 
 
 
Nephrotic
syndrome
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Primary
 
 
 
Secondary

In children nephrotic syndrome is assumed to be minimal change disease. Biopsies are done only there is no response to steriods.

Diabetes mellitus

General

  • Most common cause of end stage renal disease (ESRD).
  • Rarely biopsied.

Microscopic

Features:[17]

  • Thick glomerular basement membrane (GBM).
  • Thickened (eosinophilic) tunica media in both the afferent and efferent arterioles.[18]
  • Mesangial matrix expansion - leads to nodule formation Kimmelstiel-Wilson nodules (nodular glomerulosclerosis).

Other:

  • Armanni-Ebstein change - cytoplasmic vacuolization of tubular cells (usu. loop of Henle) -- innermost cortex, outer medulla;[19] not specific to diabetes mellitus.[20]

Other - with weak evidence:

  • Extra efferent vessels.[21]

Memory device:

  • GBM = thick GBM, both afferent & efferent artiole thickened, mesangial matrix expansion.

Images:

Notes:

  • Hypertensive kidneys have changes only in the afferent arteriole, i.e. the efferent arteriole is spared (see hypertension).

IgA nephropathy

General

  • AKA Berger disease.

Microscopic

Features:

  • Mesangial hypercellularity - may be only light microscopy finding.
  • Diagnosis based on immunofluorescence (IgA+).

Image: IgA nephropathy (med.utah.edu).

Membranous nephropathy

General

  • Presents as nephrotic syndrome.

Microscopic

Features:

  • Subepithelial immunocomplex deposition, spike forming.

Focal segmental glomerulosclerosis

General

  • Abbreviated FSGS.
  • Presents as nephrotic syndrome.
  • Does not respond to steroids (unlike MCD).

Microscopic

Features:

  • Partial sclerosis of some glomeruli.

Image:

Membranoproliferative glomerulonephritis

  • Abbrev. MPGN.
  • In adults most common cause: hepatitis C.

Histology

  • Endothelial cell proliferation.
  • Basement membrane double layering (tram-tracking).
  • Mesangial hypercellularity.

Lupus nephritis

Five classes:

  • Diffuse mesangial 2 vs. 4.
  • Focal patch mesangial 3.
  • Membranous 5 ???

Notes:

Fabry disease

General

  • Rare X-linked genetic disease.
    • Caused by defect in alpha-galactosidase A gene.
    • Women partially affected
  • Lysosomal storage disorder -- 2nd in prevalence only to Gaucher disease.
  • Multisystem disease affecting small vessels and kidney.

Presentation

  • Women: usually proteinuria.
  • Men: angiokeratomas (skin lesion), proteinuria.

Microscopy

LM:[22]

  • Foamy podocyte inclusions, best visualized with toluidine blue.
  • Mild mesangial hypercellularity.

EM:[22]

  • Myelin-like inclusions.
    • Concentric bodies with an onion-skin-like appearance.
  • Zebra bodies.
    • Ovoid inclusions with striped pattern.

Note:

  • Myelin-like inclusion are not pathognomonic for Fabry disease; they may result from drug use:[22]
    • Amiodarone,
    • Aminoglycosides,
    • Chloroquine.

Tx

  • Symptomatic treatment.
  • Enzyme replacement - agalsidase alpha (Replagal) or agalsidase beta (Fabrazyme).

Acute tubular necrosis

  • Best diagnosed clinically (using urine R&M) - hemegranular casts are diagnostic.
  • Often abbreviated ATN.

Histopathology

Features:[23]

  • Hemegranular casts in the lumen.
  • Regenerative activity (mitoses).

Hepatorenal syndrome

  • Acute renal failure due secondary to cirrhosis or fulminant liver failure.

Clinical

  • Urine sodium is low,[24] unlike in ATN (the main DDx).

Pathophysiology

  • Renal vasoconstriction.[25]

Histology

  • Normal.

Treatment

Medical and surgical:[26]

  • Vasoconstrictors (e.g. midodrine, terlipressin (counteracts splanchnic vasodilation), norepinephrine).
  • Albumin.
  • TIPS (transjugular intrahepatic portosystemic shunt).
  • Liver transplantation.

Note:

  • I suspect a portal vein pump would work... it reduces portal pressure and would likely increase hepatic function.

Alport disease

Clinical

  • Hearing loss (sensorineural).
  • Hematuria - usually preceeds hearing loss.[27]
  • Can be thought of a pathologic form of thin basement membrane disease.[28]

Etiology

  • Genetic defect - collagen type IV.

Inheritance:[27]

  • X-linked - 80%.
  • Autosomal recessive - 15%.
  • Autosomal dominant - 5%.

Polycystic kidney disease

Types:

  • Adult onset - autosomal dominant polycystic kidney disease (ADPKD).
  • Childhood onset - autosomal recessive polycystic kidney disease (ARPKD).

Autosomal dominant polycystic kidney disease (ADPKD)

General

Etiology

  • Mutation in PKD1 gene or PKD2 gene.
  • Is classified in a large group of diseases - ciliopathies.

PKD1 related disease:[29]

  • Encodes polycystin.
  • Death at ~53 years.
  • Assoc. with cerebral aneurysms.

PKD2 related disease:[29]

  • Death at ~69 years.
  • Assoc. with colonic diverticula, aortic aneurysm, mitral valve prolapse.

Liver cysts and PKD

General

Features:

  • Most common extra-renal manifestation of PKD; dependent on age, sex and renal function:[30]
    • Age dependence:
      • 10-17% <40 years old have liver cysts.
      • 70-75% >60 years old have liver cysts.
    • Renal function:
      • 60-70% of patients with end-stage renal disease (ESRD) and near-ESRD.
    • Females more often affected.
  • Hepatic function usu. preserved.

Complications:[29]

  1. Infected cyst.
  2. Cholangiocarcinoma.
Microscopic

Features:

  • Von Meyenburg complexes:
    • Cluster of dilated ducts with "altered" bile.
    • Surrounded by collagenous stroma.


See also: Medical liver disease.

Gross

Features:

  • Thin walled cysts.
    • Number of cysts:
      • If you can count 'em it favours acquired renal cystic disease... if you can't it favours the genetic condition.

Microscopic

Features:[31]

  • Cysts lined by simple flattened epithelium.
  • Normal renal tubules interspersed between cysts.
  • +/-Fibrosis (late-stage).

DDx:

  • Acquired renal cystic disease - rarely.[32]
    • Morphologically similar to acquired renal cystic disease.[33]

Acquired renal cystic disease

General

  • Thought to arise due to uremia,[34] not specific to the type of renal dialysis, i.e. hemodialysis vs. peritoneal dialysis.
  • Presence of cysts dependent on duration of dialysis:[34]
    • < 3 years ~44%.
    • >4 years ~80%.
    • >10 years ~90%.
  • Associated with renal cell carcinoma (papillary subtype).[35]

Microscopic

Features:[32]

  • Cysts - location: cortex and medulla.
    • Lined by simple flattened epithelium.

Transplant

Predictors

  • Associated with C4d+ IHC.[36]
  • Mean graft survival is ~4 years for C4d+ interstitial capillaries vs. ~8 years for C4d- renal grafts.[37]

Polyomavirus

  • This bad-boy is associated with failure of transplanted kidneys.[38]
  • Treatment: reduce immunosuppression.[39]

Microscopic features:[39]

  • Ground glass-like nuclear inclusions.
  • Nuclear enlargement.

Calcineurin-inhibitor toxicity

See also

References

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  11. AH. 13 August 2009.
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  13. Fogo, Agnes; Bruijn, Jan A.; Cohen, Arthur H.; Colvin, Robert B.;Jennette, J. Charles (2006). Fundamentals of Renal Pathology (1st ed.). Springer. pp. 82. ISBN 978-0387311265.
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  20. Zhou C, Byard RW (September 2010). "Armanni-Ebstein phenomenon and hypothermia". Forensic Sci Int. doi:10.1016/j.forsciint.2010.08.018. PMID 20875709.
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  23. PS April 2009.
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  33. RJ. 20 October 2010.
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  36. Vascular deposition of complement-split products in kidney allografts with cell-mediated rejection. Feucht HE, Felber E, Gokel MJ, Hillebrand G, Nattermann U, Brockmeyer C, Held E, Riethmüller G, Land W, Albert E. Clin Exp Immunol. 1991 Dec;86(3):464-70. PMID 1747954.
  37. Impact of humoral alloreactivity early after transplantation on the long-term survival of renal allografts. Lederer SR, Kluth-Pepper B, Schneeberger H, Albert E, Land W, Feucht HE. Kidney Int. 2001 Jan;59(1):334-41. PMID 11135088.
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  39. 39.0 39.1 Nickeleit, Volker; Singh, Harsharan K. Polyomavirus Allograft Nephropathy: Clinico-Pathological Correlations. URL: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=eurekah&part=A74503#A74539. Accessed on: 8 November 2010.
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