Ch 114 - Kidneys Flashcards
How often are multiple renal arteries reportedly found?
In which kidney is this most common?
- 13% of dog kidneys
- 10% cat kidneys
- Left kidney is more common
Right kidney more commonly has multiple renal veins
Where do the capsular arteries commonly arise from?
- Phrenicoabdominal and adrenal arteries
What is the role of the vasa recta capillaries?
- Extend from the cortex into the medulla, reabsorbing water from the collecting ducts and returning it back to systemic circulation
- Help to maintain hypertonicity of the renal medulla through countercurrent exchange system
What structure helps to maintain renal autoregulation of blood flow?
Macula densa (between glomerulus and afferent arterioles)
What cells within the glomerulus are responsible for filtration?
- Podocytes - water and small particles under 60,000 daltons can freely pass through the filtration slits
- Inherent negative charge of the glomerulus basement also enhances the selective nature of filtration
What is normal urine production?
20-45ml/kg/d
What is the osmolality of the glomerular filtrate and of the medullary interstitial fluid?
- Glomerular filtrate - 300mOs/L
- Medullary interstitial fluid - 1200-1400mOs/L
What is normal renal blood flow?
- Approx 25% of CO
- 4ml/min/g of renal tissue
Calculated as renal perfusion/renal vascular resistance
How does GFR relate to blood flow?
GFR is roughly 20% of renal plasma flow
What determines the concentrating ability of the kidney?
Based on renal medullary hyperosmolarity which is maintained by the vasa recta through a counter-current mechanism
What can cause decreased concentrating ability of the kidney?
Increased blood flow through the vasa recta
- Vasodilation
- Increased arterial pressure
- Increased fluid volume
What mechanisms create medullary interstitial hyperosmolarity?
- Faculative diffusion of large molecules (urea) into the interstitium
- Limited ability of water to diffuse into interstitium
- Active transport of Na, K, Cl and other electrolytes into the interstitium from the thick portion of the proximal loop of Henle
Urea contributes 40-50%. Absorbed in the collecting ducts UT-A1, stimulated by ADH. It is then recycles by moving to thin limb of Loop of Henle
What suture pattern caused increased renal parenchymal damage?
Horizontal mattress
- parenchymal necrosis, fibrosis, scarring and atrophy
List some indications for renal surgery
- Unresponsive pyelonephritis
- Perinephric abscess or cyst
- Unilateral renal neoplasia
- Severe renal trauma
- Ureteral consitions causing severe irresolvable hydronephrosis
What factors increase the risk of haemorrhage during renal surgery?
- Hypertension
- Thrombocytopaenia
- Azotaemia - inhibits platelet adhesion and aggregation. Should perform BMBT
What is the rate of pulmonary metastasis with primary renal neoplasia?
- Dog: 16-48%
- Cat: 43%
List some contraindications for renal biopsy
What needle can be used?
Contraindications:
- Uncontrolled coagulopathy
- Hypertension
- Large or multiple renal cysts or abscesses
- Extensive pyelonephritis
- Ureteral obstruction
- Severe hydronephrosis
Monopty biopsy needle
How do you close a partial nephrectomy?
- Overlapping mattress sutures through the parenchyma and apposition of the overlying capsule
- If cannot be apposed, can tack omentum to exposed surface
