Ch 114 Kidneys

Question 1

Gross Anatomy

Answer 1

• cranial pole of the right kidney lies in the renal fossa of the caudate liver lobe
• Nerves, vesses, lymphatic and ureter enter at the hilus
• Outermost, there is a thin, fibrous capsule covering the kidney
• renal cortex is composed of glomeruli and adjacent structures
• The medulla is striated in appearance and projects into the renal pelvis

Question 2

kidney functions

Answer 2

• removal of metabolic waste products
• maintenance of normal fluid balance
• regulation of blood pressure

Question 3

How often are multiple renal arteries reportedly found?
In which kidney is this most common?

Answer 3

• 13% of dog kidneys
• 10% cat kidneys
• Left kidney is more common

Right kidney more commonly has multiple renal veins

Question 4

Where do the capsular arteries commonly arise from?

Answer 4

Phrenicoabdominal and adrenal arteries

Question 5

What is the role of the vasa recta capillaries?

Answer 5

• Extend from the cortec 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

Question 6

Physiology

Answer 6

• basic functional unit of the kidney is the nephron
• the glomerulus is a tuft of capillaries enclosed within the glomerular capsule.
• glomerulus of a juxtamedullary nephron is located deep in the cortex near the corticomedullary junction. The thin limb of the loop of Henle extends deep into the inner medulla.

example functions:
- glomerulus filters blood
- proximal tubule bulk reabsorption or water and solutes
- regulation of acid, HCO3, Ca, Na, K
- juxtaglomerula appartus regulate GFR and BP

Question 7

What structure helps to maintain renal autoregulation of blood flow?

Answer 7

Macula densa (between glomerulus and afferent arterioles)

Question 8

What cells within the glomerulus are responsible for filtration?

Answer 8

• Podocytes - water and small particles under 60,000 daltons can freely pass through the filtration slits (Most cellular components of blood exceed this size)
• Inherent negative charge of the glomerulus basement also enhances the selective nature of filtration

Question 9

What is normal urine production?

Answer 9

20-45ml/kg/d

Question 10

What is the osmolality of the glomerular filtrate and of the medullary interstitial fluid?

Answer 10

Glomerular filtrate - 300mOs/L
Medullary interstitial fluid - 1200-1400mOs/L

Question 11

What is normal renal blood flow?

Answer 11

• Approx 25% of CO
• 4ml/min/g of renal tissue

Question 12

RBF

Answer 12

• Calculated as renal perfusion (systemic BP)/renal vascular resistance
• Vasoconstriction and vasodilation of the afferent and efferent renal arterioles are primarily responsible for renal vascular resistance.
• These vessels are therefore the targets for renal autoregulation.
• Autoregulation allows adequate blood flow during times of systemic hypotension or hypertension
• diseased kidney has decreased autoregulatory ability > susceptible to ischemic injury during times of hypotension

Question 13

How does GFR relate to blood flow?

Answer 13

GFR is roughly 20% of renal plasma flow

Question 14

What determines the concentrating ability of the kidney?

Answer 14

Based on renal medullary hyperosmolarity which is maintained by the vasa recta through a counter-current mechanism

Because of increased osmolarity of blood leaving the renal medulla, particles such as urea transfer from blood exiting the medulla into blood entering the medulla. This countercurrent exchange permits the medullary interstitium surrounding the collecting ducts to maintain a high osmolarity.

Question 15

What can cause decreased concentrating ability of the kidney?

Answer 15

Increased blood flow through the vasa recta
- Vasodilation
- Increased arterial pressure
- Increased fluid volume

Question 16

What mechanisms create medullary interstitial hyperosmolarity?

Answer 16

• 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

Question 17

Healing of the Upper Urinary Tract

Answer 17

• Inflammation and infarction occur with parenchymal ischemia secondary to compression, electrocoagulation, vascular transection, or inflammation and delay wound healing
• Horizontal mattress suture > parenchymal necrosis, fibrosis, scarring and atrophy

Question 18

diagnostics

Answer 18

• Thoracic radiographs should be performed in any animal in which neoplasia is suspected
• normal canine kidney is 2.0 to 2.5 times the length of the adjacent vertebra
• normal feline kidney length is 2 to 3 times the adjacent vertebrae

excretory urogram or intravenous pyelogram
- contrast is removed by passive glomerular filtration and is therefore a function, but not a measurement, of glomerular filtration rate (GFR)
- contrast toxicity: exact mechanism of renal toxicity is not well understood. Systemic administration of contrast agents may result in hypotension
- RADS: 5, 20, and 40 minutes after injection
- 400 mg/kg
- 1st = renal angiographic phase, demonstrates the arterial supply of the kidney
- 2nd = renal phase, “blush” throughout the parenchyma.
- 3rd = excretory phase, contrast flows into the collecting ducts and transported into pelvis

Pyelography
- direct injection into the renal pelvis
- concern about giving a systemic dose of contrast or when the renal artery is obstructed

Ultrasound
- Major ultrasound findings in affected dogs included renal pelvic dilatation (usually with proximal ureteral dilatation)
- noninvasively evaluating renal structure
- Doppler ultrasonic imaging can be used to determine the resistance index of the kidney

CT
- accurately predict renal vasculature anatomy and is thought to be superior to excretory urography for evaluation of renal vasculature in potential kidney donors.
- Dynamic CT has been used to estimate glomerular filtration rate

Question 19

List some indications for renal surgery

Answer 19

• Unresponsive pyelonephritis
• Perinephric abscess or cyst
• Unilateral renal neoplasia
• Severe renal trauma
• Ureteral consitions causing severe irresolvable hydronephrosis

Question 20

What factors increase the risk of haemorrhage during renal surgery?

Answer 20

Hypertension
Thrombocytopaenia
Azotaemia - inhibits platelet adhesion and aggregation. Should perform BMBT

Question 21

What is the rate of pulmonary metastasis with primary renal neoplasia?

Answer 21

Dog: 16-48%
Cat: 43%

Question 22

Which lateral radiographs is better for viewing both kidneys?
What is the normal kidney size?

Answer 22

Right lateral
Dogs: 2-2.5x length of adjacent vertebra
Cats: 2-3x length of adjacent vertebra

Question 23

What imaging modality of best for determining the GFR (and therefore function) of the kidneys?

Answer 23

• Nuclear scintigraphy
• Plasma clearance tests are more accurate but more difficult to perform and time consuming
• Inherent renal autoregulatory mechanisms can result in substantial variation in glomerular filtration rate of normal animals

Question 24

What radiopharmaceuticals can be used for scintigraphy of the kidney?

Answer 24

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

Question 25

pre-op consdierations

Answer 25

- uremia, blood pressure irregularities, anemia, coagulopathies, and electrolyte imbalances - urinary catheter is placed to monitor urine production - Maintenance of renal perfusion under anesthesia is critical - Drugs that cause hypotension (e.g., acepromazine) or nephrotoxicity (e.g., aminoglycosides or nonsteroidal antiinflammatory drugs) should be avoided - Dopamine or dobutamine may be required intraoperatively in hypotensive - Epidural administration can reduce intraoperative anesthetic - nephrectomy, ideally functional test of contralateral kidney

Question 26

list developmental anaomolies

Answer 26

- Renal agenesis - renal dysplasia - renal ectopia - fised kidney - Polyctstic Kidney disease

Question 27

Where is the most common location of renal ectopia?

Answer 27

Pelvis

Question 28

What breeds are predisposed to polycystic kidney disease?

Answer 28

Persians (37-38% of breed) Bull Terriers

Question 29

What breeds are overrepresented with renal calculi? What is the most common calculi? List potential causes of renal calculi

Answer 29

* Siamese cats, Bichon Frise * Calcium oxalate Oversaturation of the urine with calculogenic substances - Organ dysfunction (liver dz) - neoplasia (hyperCa2+) - Increased Ca intake - Drugs - Increased intestinal absorption - Impaired renal reabsorption - Excessive skeletal mobilisation

Question 30

List options for stone removal | cannot be dissolved with medical protocols

Answer 30

* Extracorporeal shockwave lithotripsy * Nephrotomy * Pyelolithotomy * Endoscopic nephrolithotomy (intracorporeal lithotripsy) * nephrectomy (with a unilateral severely hydronephrotic, infected, or nonfunctional) *cats with mild to moderate renal disease, the presence of renal calculi was not associated with progression of renal disease or a difference in mortality rates from renal disease - sx may not be needed*

Question 31

What are the most common renal neoplasias in cats and dogs?

Answer 31

Cats: Lymphoma (can frequently be diagnosed with fine needle aspiration.) Dogs: Carcinoma | hematuria, weight loss, lethargy, inappetence, abdominal mass

Question 32

ddx neoplasia

Answer 32

transitional cell carcinoma transitional cell papilloma anaplastic sarcomas and carcinomas, hemangiosarcoma, lymphoma, nephroblastoma angiomyxoma.

Question 33

What inherited neoplastic condition of the kidneys can effect young GSD?

Answer 33

Renal cystadenocarcinoma with nodular dermatofibrosis - Bilateral multifocal renal tumours - Firm nodules of dense collagen in the skin and SQ - Females commonly also have uterine leiomyoma - Mutation of FLCN gene, affecting folliculin (a potentially tumour suppressing portein) - 50% mets

Question 34

List paraneoplastic syndromes which can be seen with renal neoplasis

Answer 34

Polycythaemia and thrombocytosis in cats HyperCa Hypoglycaemia Leucocytosis Peripheral neuropathy

Question 35

What is the rate of bilateral renal neoplasia?

Answer 35

4-32%

Question 36

Neoplasia Sx

Answer 36

- Unilateral nephrectomy - humans: (partial nephrectomy) > nephron-sparing procedures helps to prevent development of anuria

Question 37

What is the MST for renal neoplasia?

Answer 37

Carcinoma - 16m Sarcoma - 9m Nephroblastoma - 6m HSA - 278d (haemoperitoneum has significantly shorter survival 62d

Question 38

ist some DDx of abnormal appearance of the kidney

Answer 38

Developmental abnormalities Calculi Neoplasia Acquired renal cyst Perirenal pseudocyst Renal abscess Trauma Kidney worms (Dioctophyma renale)

Question 39

Acquired Renal Cysts

Answer 39

- secondary to chronic nephropathies or may be incidental findings in healthy dog - All affected dogs had systemic hypertension - Cysts were drained percutaneously in anesthetized dogs > 95% ethanol instilled then removed

Question 40

List some treatment options for severe renal trauma?

Answer 40

* 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

Question 41

Idiopathic Renal Hematuria

Answer 41

- Affected dogs are often large breed and less than 2 years of age. - Accumulation of blood clots in the bladder or ureters may result in obstruction and secondary hydronephrosis/hydroureter. - 30% have or will develop bilateral disease. - Diagnosis is best performed via cystoscopy. - Local sclerotherapy (better than kidney removal)

Question 42

List some contraindications for renal biopsy What needle can be used?

Answer 42

Contraindications: - Uncontrolled coagulopathy - Hypertension - Large or multiple renal cysts or abscesses - Extensive pyelonephritis - Ureteral obstruction - Severe hydronephrosis Monopty biopsy needle | sufficient size so can be submitted for transmission electron microscopy

Question 43

list methods of renal biopsy

Answer 43

- percutaenous - ultrasound guisded - keyhole - laparscopic - incisional biopsy (closed with simple interrupted or cruciate sutures of 3-0 or 4-0 absorbable, consdier arterial occlusion for <20min)

Question 44

What is the complication rate of surgical renal biopsy? What factors have been associated with increased complications?

Answer 44

* Complications 1-21.7% (Major in 8.9%, haemorrhage most common) * 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 - hypertension haematoma, cyst, hydronephrosis, fibrosis)

Question 45

List some indications for nephrotomy

Answer 45

Biopsy Removal of nephroliths or other obstructive lesions Chronic infection Persistent haematuria of renal origin Persistent hydronephrosis

Question 46

What are the 2 options for nephrotomy?

Answer 46

* 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 *Inconsistent findings regarding the effect of nephrotomy on renal function serve to remind the surgeon that numerous factors may affect renal function after surgical incision.* | temporary occlusion of vessels, better control over intraop hemorrhage.

Question 47

What should be the maximum occlusion time of the renal vessels?

Answer 47

20min

Question 48

How do you close a partial nephrectomy? indications?

Answer 48

* Overlapping mattress sutures through the parenchyma and apposition of the overlying capsule * If cannot be apposed, can tack omentum to exposed surface * Nephron-sparing surgery may be a more appropriate option for animals that have a reduced glomerular filtration rate in their remaining kidney

Question 49

List potential complications following a partial nephrectomy

Answer 49

Haemorrhage Urine leakage Urine fistula

Question 50

What is the expected orientation of the renal vessels?

Answer 50

When in normal orientation, renal vein is ventral to renal artery When the kidney is rotated ventromedially, renal artery is lateral to renal vein

Question 51

Nephrectomy and Ureteronephrectomy

Answer 51

- If possible, function of the kidney to be left in the patient should be evaluated with scintigraphy - Failure to accurately identify an early branch or a double renal artery can result in significant hemorrhage - leaving the smallest ureteral remnant possible. - concerned that a distal ureteral remnant permits urine reflux with resultant persistence or development of urinary tract infectio

Question 52

How many ports are required for a laparoscopic nephrectomy?

Answer 52

3 to 4 port technique (1 caudal to umbilicus, 1 caudal to last rib and 1 cranial to pelvic limb for triangulation)

Question 53

Complications associated with nephrectomy

Answer 53

* progression of preexisting kidney disease, * acute renal failure, * failure to resolve underlying clinical signs, * inadvertent damage to other abdominal organs

Question 54

Nephrostomy Tube Placement

Answer 54

Nephrostomy catheter placement is used to stabilize patients - Earlier use of Foley, red rubber, or latex catheters led to high complication rates, including urine leakage, infection, and hemorrhage. - A retrospective study reported complications in 46% of cats, with urine leakage being the most common issue. - More recent studies using locking-loop pigtail nephrostomy catheters showed fewer complications (10%), such as subcutaneous urine leakage and accidental dislodgment. - Renal function improved in most patients who survived 72 hours post-surgery. - Catheters were typically removed after a median of 7 days, with longer durations (21 days) in cases without concurrent nephropexy.

Question 55

Unilateral nephrectomy in dogs is associated with a high rate of intraoperative and postoperative complications Carley Johnson 2024

Answer 55

69 dogs. Retrospective. Unilateral nephrectomy in dogs > high rate of complications neoplastic renal lesions (n = 37), benign lesions (30) 44.9% intraoperative and 42.6% postoperative (Most lower-grade) 7 dogs mortality acute kidney injury > 12 dogs postoperatively (17%), 2 dogs euthanized Chronic kidney disease in almost 50% @ long-term follow-up. (and 50% of these were euthanised for this reasons) Pre-op GFR assessed in 9 (13%) dogs, with only 2 abnormal., Humans > Unilateral nephrectomy cause postop AKI in 21% to 34% suspected that these animals may be more susceptible to CKD due to the reduction of functional nephrons.

Question 56

Transarterial chemoembolisation for palliative treatment of renal cell carcinoma in two dogs with pulmonary metastasis A. Kimata 2022

Answer 56

postoperative radiographs demonstrated a decrease in the tumour size. The dogs died 215 and 525 days after the initial evaluation, respectively. As a palliative treatment

Question 57

Upper urolithiasis in cats with chronic kidney disease: prevalence and investigation of serum and urinary calcium concentrations Huai-hsun Hsu 2022

Answer 57

Among the 140 cats with CKD, the prevalence of upper urolithiasis was 73%. Cats with CKD that were purebred, fed dry food and fed urine-acidifying food only often had upper urolithiasis upper urolithiasis itself may be a cause of CKD as obstruction of ureteroliths or nephroliths can unknowingly damage the kidney when occurring unilaterally

Question 58

Diagnostic utility of renal fine-needle aspirate cytology and ultrasound in the cat Camille A McAloney 2018

Answer 58

Of 96 cytologic submissions available for review, diagnostic yield was 68% Of 12 confirmed cases, cytology was 100% sensitive and specific for the detection of neoplasia

Question 59

Simple ectopic left kidney in the pelvic cavity in a cat

Question 60

NSAID in cats based on current evidence, the WSAVA supports the long-term administration of the lowest effective doses of meloxicam and robenacoxib in cats with concomitant chronic pain and CKD as part of a multimodal approach. not all cats are satisfactory candidates > must have stable CKD, and maintenance of proper hydration is paramount. safety of NSAID therapy in cats with advanced CKD remains unknown.

Question 61

Endoscopic nephrolithotomy for the removal of complicated nephroliths in dogs and cats: 16 kidneys in 12 patients (2005–2017) Brian Petrovsky 2019

Answer 61

Endoscopic nephrolithotomy in dogs and cats: 12 patients involves intracorporeal lithotripsy with removal of stone fragments through a renal-access sheath > dilation and spreading of the nephrons, rather than transection Indications : massive calculi displacing parenchyma, recurrent UTI, and obstruction complications: renal hemorrhage requiring a blood transfusion (n = 1), renal capsule tear (1), and ureteral puncture (1); all were managed without adverse consequence. No mortalities. 5/12 patients alive at the final follow-up decrease in GFR associated with surgical nephrotomy is a major concern.