Kidney

• Kidney


  Converts more than 1,700 L of blood per day into about 1 L of a highly concentrated fluid called urine
• Kidney


  • Excretes the waste products of metabolism
  • Maintains the appropriate acid balance of plasma
  • Serves as endocrine organ secreting hormone such as erythropoietin, renin, and prostaglandins
  • Regulates Vitamin D metabolism
• Basic morphologic components of the kidney

  • Glomeruli
  • Interstitium
  • Tubules
  • Blood Vessels
• Glomerular diseases


  Most are immunologically mediated
• Tubular and Interstitial disorders

  Due to toxin or infection
• All forms of chronic kidney disease ultimately damage all four components of the kidney, culminating in to end-stage kidneys
• Azotemia


  Elevation of blood urea nitrogen (BUN) and creatinine levels, related largely to decreased glomerular filtration rate (GFR)
• Pre-renal azotemia


  Encountered when there is hypoperfusion of the kidneys (e.g. HTN or excessive fluid loss), impairment of renal function in the absence of parenchymal damage
• Post-renal azotemia


  Seen whenever urine flow is obstructed distal to the kidney
• Uremia


  Characterized by failure of renal excretory, metabolic, and endocrine functions, frequently manifest secondary involvement of the GIT, peripheral nerves, and heart
• Nephritic Syndrome


  Caused by glomerular disease and dominated by acute onset of hematuria and red cell casts on urinalysis, diminished GFR, mild-moderate proteinuria, and hypertension
• Rapidly Progressive Glomerulonephritis


  Nephritic syndrome with rapid decline in GFR (hours to days)
• Nephrotic Syndrome


  Characterized by heavy proteinuria, hypoalbuminemia, severe edema, hyperlipidemia, and lipiduria
• Asymptomatic Hematuria or Proteinuria

  Usually a manifestation of mild or subtle anomalies
• Acute Kidney Injury


  Rapid decline in GFR with concurrent dysregulation of fluid and electrolyte balance, and retentions of metabolic waste products such as urea and creatinine, manifested as oliguria or anuria
• Chronic Kidney disease


  Defined as presence of diminished GR that is persistently less than 60ml/min/1.73m2 for at least 3 months, persistent albuminuria, clinically silent decline in renal excretory function in milder form, end result of all chronic renal parenchymal damage
• End-stage renal disease (ESRD)

  GFR less than 5% of normal, terminal stage of uremia
• Renal Tubular defects


  Dominated by polyuria, nocturia, and electrolyte imbalance, result of diseases that directly affect tubular structures or cause defects in specific tubular functions (inherited or acquired)
• Urinary Tract Infection (UTI)

  Characterized by bacteriuria and pyuria, may affect the kidney (pyelonephritis) or bladder (cystitis)
• Nephrolithiasis


  Renal stones are manifested by spams of severe pain (renal colic) and hematuria often with recurrent stone formation
• 10% of people have potentially significant renal malformation
• 20% of CRF in children is due to renal dysplasia and hypoplasia
• 10% of CRF in adults is due to autosomal dominant polycystic kidney disease
• Renal Agenesis


  Bilateral agenesis is incompatible with life, unilateral agenesis is uncommon, and compatible with life, solitary kidney enlarges as a result of compensatory hypertrophy, some develop progressive glomerular sclerosis
• Renal Hypoplasia


  Refers to failure of the kidneys to develop a normal size, may occur bilaterally, leading to renal failure in early childhood, more commonly encountered as a unilateral defect
• Ectopic Kidneys


  Development of metanephros to kidney occurs in ectopic foci, either above the pelvic brim or sometimes within the pelvis, usually normal or slightly small in size
• Horseshoe Kidneys


  Most common, fusion of the upper (10%) or lower poles (90%) of the kidneys, continuous across the midline anterior to great vessels
• Cystic diseases of the kidneys are heterogeneous, comprising of hereditary, developmental and acquired diseases
• Polycystin-1 and -2


  Form a protein complex that regulates intracellular Ca++ in response to fluid flow, mutation leads to disruption of activity and alterations of intracellular Ca++, increase in Ca++ stimulates proliferation and secretion from epithelial cells lining the cysts, resulting in progressive cyst formation and enlargement
• Autosomal Dominant (Adult) Polycystic Kidney Disease


  Characterized by multiple expanding cysts of both kidneys that ultimately destroy the renal parenchyma and cause failure, common, high penetrance, one defective APKD gene is inherited, the other is somatic
• PKD1 gene


  Located in 16p13.3, encodes for polycystin-1, mutations account for 85% of cases
• PKD2 gene


  Located in 4q21, encodes for polycystin-2, mutations are less severe than those associated with PDK1
• Autosomal Recessive (Childhood) Polycystic Kidney Disease has subcategories: Perinatal, Neonatal, Infantile, and Juvenile
• PKHD1 gene


  Maps to chromosome 6p21-23, encodes for fibrocystin, an integral membrane protein with a large extracellular region, a single transmembrane component, and a short cytoplasmic tail
• Simple Renal Cyst


  Multiple or single, usually involves the cortex, 1-5 cm, may reach 10 cm or more, translucent, lined by a gray, glistening, smooth membrane, filled with clear fluid
• Multicycstic Renal Dysplasia


  Abnormal metanephric differentiation, maybe unilateral or bilateral, almost always cystic, enlarged, extremely irregular and multicystic, lined by flattened epithelium, normal nephrons present, many have immature collecting ducts, characterized by presence of islands of undifferentiated mesenchyme, often with cartilage, and immature collecting ducts
• Chronic Dialysis Associated Cystic Disease

  Prolonged dialysis shows numerous cortical and medullary cysts, measures 0.1-4cm, contains clear fluid, lined by hyperplastic or flattened tubular epithelium, often contains calcium oxalate crystals, asymptomatic, sometimes may bleed and cause hematuria, 12 to 18-fold increase risk of renal cell carcinoma
• Cystic Diseases of the Renal Medulla


  • Medullary Sponge Kidney
  • Nephronophthisis
  • Adult Onset Medullary cystic disease
• Medullary Sponge Kidney


  Multiple cystic dilations of the collecting ducts in the medulla, occurs in adults, discovered radiographically, unknown pathogenesis, papillary ducts in the medulla are dilated, small cysts present, lined by cuboidal epithelium, occasionally transitional, unless there is pyelonephritis, scarring is absent
• Nephronophthisis & Adult-Onset medullary cystic disease


  Progressive disorder characterized by variable number of cysts in the medulla, concentrated at the corticomedullary junction, injury involves the distal tubules with basement membrane disruption, followed by progressive atrophy, cortical tubulointerstitial damage is the cause of insufficiency