Kidney Disease

• What is a Kidney?

  • 2 relatively kidney bean shaped organ made to filter byproducts and excessive ions/metabolites out of the body
  • Excretion is urine
• What is a Kidney?

  • Other functions
  • Hormone production to regulate erythrocyte concentration and normalizing blood pressure
• Kidney Structure- External

  • Sits in retroperitoneal space in mid-lumbar area lateral to main vessels
  • Renal artery and vein feed from/ to aorta and caudal vena cava, respectively
  • Right kidney is more cranial than left
• Kidney Structure- External

  • A tough, fibrous renal capsule envelopes each kidney and provides support for the soft tissue
• Kidney Structure- External

  • Concave aspect is the hilus
  • Area that ureters attach- tube between kidneys and bladder
• Kidney Structure- Internal

  • Cortex
  • Contains glomeruli and convoluted tubules
• Kidney Structure- Internal

  • Medulla
  • Loops of Henle and collecting tubules
  • Makes up renal pyramids
• Kidney Structure- Internal

  • Corticomedullary junction between cortex and medulla
• Kidney Structure- Internal

  • Renal pelvis leads into renal crest
  • Both are internal structures leading from hilus
• Kidney Structure- Internal

  • Nephrons: corticomedullary and Juxtamedullary
• Nephrons

  • Parts of nephron
  • Glomerulus, peritubular capillaries, Bowman’s capsule, loops of Henley
• Nephrons

  • Corticomedullary
  • Glomeruli in the outer and middle cortices
  • Short loop of Henle that extends to junction of the cortex and medulla or into the outer zone of medulla
  • Excretory and regulatory functions
• Nephrons

  • Juxtamedullary
  • Glomeruli in the cortex close to medulla
  • Long loops of Henle that extend deeper into the medulla → some extend as deep as renal pelvis
  • Maintain osmotic gradient of interstitial fluid of medulla, from low to high in outer to inner medulla
• How do Kidneys Work?

  1. Blood comes into nephron through peritubular capillaries
  2. Pressure gradient in glomeruli forces solutes out of blood
• How do Kidneys Work?

  3. Proximal convoluted tubule reabsorbs water, electrolytes, and nutrients out of filtrate and puts back into interstitial fluid

  • Adjusts blood pH by removing toxins from interstitial fluid and putting into filtrate
• How do Kidneys Work?

  4. Descending loop of Henle has aquaporins that allow water to pass back and forth (as needed) from filtrate to interstitial fluid
• How do Kidneys Work?

  5. Ascending loop of Henle

  • Thin- passively transports Na+ and Cl- ions into interstitial fluid
  • Thick- actively transports Na+ and Cl- ions into interstitial fluid
• How do Kidneys Work?

  6. Distal convoluted tubule → K+ and H+ ions are selectively secreted into the filtrate, and Na+, Cl−, and HCO3− ions are reabsorbed
• How do Kidneys Work?

  • Collecting duct reabsorbs solutes and water from the filtrate, forming dilute urine
• Acute Kidney Injury (AKI)

  • Sudden damage to kidneys
  • Trauma, infection, autoimmune conditions, toxins, etc.
• Acute Kidney Injury (AKI)

  • Can have obvious signs of renal insufficiency, but not always
• Acute Kidney Injury (AKI)

  • Any species that has kidneys can encounter this
  • Can affect any part of nephron- causes insufficiency in a variety of ways
• Most Common Causes -AKI

  • Infections like leptospirosis
  • Spirochete bacteria that causes Na+ transport dysregulation and decreased aquaporin expression in medulla, resulting in polyuria and natriuresis
• Most Common Causes -AKI

  • Toxic plants
  • Almost all lilies → process for most is unknown
  • EVERY part of lilies including the water are toxic
  • Some make Ca2+ oxalate monohydrate crystal
• Most Common Causes -AKI

  • Toxic medications/chemicals
  • ethylene glycol poisoning can cause quick renal death
  • Shock inducing events
• Clinical Signs - AKI

  • Exact clinical signs dependent onunderlying cause
  • Oliguria- abnormally small amounts of urine
  • Polyuria
  • Painful kidneys
  • Vomiting and/or diarrhea
• Clinical Signs - AKI

  • Anorexia
  • Dehydration
  • Fever if infectious cause
  • Lethargy
  • Ulceration of mouth
  • Ataxia
• Physical Exam- AKI

  • Some animals will look perfectly normal but sometimes will see signs on exam
  • Tachycardia
• Physical Exam- AKI

  • Dry or tacky gums
  • Reduced CRT and exaggerated skin turgor
• Physical Exam- AKI

  • Lethargic +/- reduced stimuli response
• Diagnostics - AKI

  • CBC
  • If infectious → leukocytosis usually with neutrophilia +/- left shift (sign of extensive infection), anemia if have reached full failure
  • May see lymphopenia depending on cause
• Diagnostics - AKI

  • Chemistry
  • Renal azotemia- elevated BUN and creatinine
  • Hyperphosphatemia +/- hypocalcemia, hyperkalemia, metabolic acidosis
• Diagnostics - AKI

  • Urinalysis
  • Either significantly dilute or very concentrated due to lack of production
  • Active sediment- crystals, bacteria, WBCs and/or RBCs, hyaline casts
• Diagnostics - AKI

  • Ultrasound- not done often but good to check size of kidneys
  • IFA or PCR for infectious agents
• Treatment - AKI

  • Treatment highly dependent on underlying cause
  • Almost all will require hospitalization on fluids
• Treatment - AKI

  • Toxins
  • Hemodialysis recommended to flush system and prevent kidneys from further damage
• Treatment - AKI

  • Shock
  • Correct whatever caused shock and renal injury should recover
• Treatment - AKI

  • Anemia
  • Correct with whole blood transfusion
• Chronic Kidney Disease (CKD)

  • Chronic decline in the population of functional nephrons
  • Glomerular filtration rate (GFR) is no longer adequate to maintain normal excretory function
• Chronic Kidney Disease (CKD)

  • Happens in dogs and cats, but more frequently will diagnose in cats (3x more likely)