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%
Which lateral radiographs is better for viewing both kidneys?
What is the normal kidney size?
- Right lateral
- Dogs: 2-2.5x length of adjacent vertebra
- Cats: 2-3x length of adjacent vertebra
What imaging modality of best for determining the GFR (and therefore function) of the kidneys?
Nuclear scintigraphy
Plasma clearance tests are more accurate but more difficult to perform and time consuming
What radiopharmaceuticals can be used for scintigraphy of the kidney?
- Technitium 99m - DTPA (diethylenetriaminepentaacetic acid)
- Technetium 99m - MAG3 (mercaptoacetyltriglycine) - better for patients with very limited renal function and for performing renal perfusion studies to evaluate transplant patients
Where is the most common location of renal ectopia?
Pelvis
What breeds are predisposed to polycystic kidney disease?
- Persians (37-38% of breed)
- Bull Terriers
What breeds are overrepresented with renal calculi?
What is the most common calculi?
List potential causes of renal calculi
- Siamese cats, Bichon Frise
- Calcium oxalate
Oversaturation of the urine with calculogenic substances
- Organ dysfunction
- neoplasia
- Increased Ca intake
- Drugs
- Increased intestinal absorption
- Impaired renal reabsorption
- Excessive skeletal mobilisation
List options for stone removal
- Extracorporeal shockwave lithotripsy
- Nephrotomy
- Pyelolithotomy
- Endoscopic nephrolithotomy (intracorporeal lithotripsy)
What are the most common renal neoplasias in cats and dogs?
Cats: Lymphome
Dogs: Carcinoma
What inherited neoplastic condition of the kidneys can effect young GSD?
Renal cystadenocarcinoma with nodular dermatofibrosis
- Bilateral multifocal renal tumours
- Firm nodules of dense collagen in the skin and SQ
- Feline common also have uterine leiomyoma
- Mutation of FLCN gene, affecting folliculin (a potentially tumour suppressing portein)
- 50% mets
List paraneoplastic syndromes which can be seen with renal neoplasis
- Polycythaemia and thrombocytosis in cats
- HyperCa
- Hypoglycaemia
- Leucocytosis
- Peripheral neuropathy
What is the rate of bilateral renal neoplasia?
4-32%
What is the MST for renal neoplasia?
- Carcinoma - 16m
- Sarcoma - 9m
- Nephroblastoma - 6m
- HSA - 278d (haemoperitoneum has significantly shorter survival 62d
List some DDx of abnormal appearance of the kidney
- Developmental abnormalities
- Calculi
- Neoplasia
- Acquired renal cyst
- Perirenal pseudocyst
- Renal abscess
- Trauma
- Kidney worms (Dioctophyma renale)
List some treatment options for severe renal trauma?
- Ureteronephrectomy
- Wrap in semielastic polyglactin mesh
- Wrap in polyglycolic acid mesh
- Sterile, nonabsorbable cyanoacrylate for small lacerations
When comparing mesh to partial nephrecomy, creatinine clearance ratio was 0.93 for mesh and 0.58 for partial nephrectomy
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
What is the complication rate of surgical renal biopsy?
What factors have been associated with increased complications?
- Complications 1-21.7% (Major in 8.9%
- Mortality rate less then 3%
Factors associated with complications:
- Thrombocytopaenia
- Prolonged clotting times
- Creatinine above 5mg/dL
- Patient older than 4yo
- BW less than 5kg
List some indications for nephrotomy
- Biopsy
- Removal of nephroliths or other obstructive lesions
- Chronic infection
- Persistent haematuria of renal origin
- Persistent hydronephrosis
What are the 2 options for nephrotomy?
- Bisectional nephrotomy (sharp dissection of the renal parenchyma)
- Intersegmental nephrotomy (Blunt dissection)
Bisectional recommended - faster, easier, no difference in post-op GFR between the 2 techniques
What should be the maximum occlusion time of the renal vessels?
20min
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
List potential complications following a partial nephrectomy
- Haemorrhage
- Urine leakage
- Urine fistula
What is the expected orientation of the renal vessels?
- When in normal orientation, renal vein is ventral to renal artery
- When the kidney is rotated ventromedially, renal artery is lateral to renal vein
How many ports are required for a laparoscopic nephrectomy?
- 3 to 4 port technique (1 caudal to umbilicus, 1 caudal to last rib and 1 cranial to pelvic limb for triangulation)
List some DDx of abnormal appearance of the kidney
- Developmental abnormalities
- Calculi
- Neoplasia
- Acquired renal cyst
- Perirenal pseudocyst
- Renal abscess
- Trauma
- Kidney worms (Dioctophyma renale)
