urinary system notes pt 4

Question 1

The primary functions of the kidneys include:

Answer 1

• excretion of waste products
• maintenance of normal salt and water concentrations
• acid-base regulation
• production of hormones (renin, erythropoietin, prostaglandins)
• conversion of Vitamin D to the active form - calcitriol (1,25- dihydroxycholecalciferol)

Question 2

3 things the kidneys need to perform their functions

Answer 2

• adequate perfusion (normal renal blood flow is up to 25 % of cardiac output)
• sufficient functional tissue mass (sufficient functional glomerular filtration rate)
• functional (unobstructed) normal outflow of urine

Question 2

Renal failure results in what? usually assessed how?
kidney failure leads to what?

Answer 2

• accumulation of waste, salt/water imbalances, acid-base imbalances, and decreased production of hormones
• commonly assessed by measuring urea, a relatively harmless molecule
• Failure of the kidney to perform its normal functions leads to uremia, a clinical syndrome with fairly consistent lesions and clinical signs

Question 3

general patterns of renal disease

Answer 3

• multifocal (embolic)
• segmental or wedge shape lesion of infarcts and pyelonephritis
• diffuse distribution of tubulointerstitial disease
• glomerular, cortical, and medullary patterns of injury

Question 4

major developmental abnormalities of the kidneys

Answer 4

• aplasia/hypoplasia
• juvenile nephropathy
• renal dysplasia
• renal cysts

Question 5

Aplastic/hypoplastic kidneys - can they be compatible with life?

Answer 5

• can be compatible with normal life as long as more than 50 % of renal tissue develops

Question 6

familial patterns in renal aplasia have been reported in what breeds?

Answer 6

Doberman pinschers and beagles

Question 7

Ectopic kidneys - risks of what?

Answer 7

• risk of obstruction due to the altered positioning of the ureters
• It is most commonly seen in pigs and dogs.

Question 8

Progressive juvenile nephropathy
- what is it?
- breeds?
- onset and signs?
- character of disease / lesions?

Answer 8

• broad term for many non-inflammatory, degenerative, and developmental diseases in young animals
• usually a congenital disease that may be inherited > if mode of inheritance is known = familial or hereditary nephropathy
• Lhaso Apsos, Shit Tzus, and golden retrievers
  <><>
• often develop uremia at 6-9 months (but can be late onset)
• changes are typical of glomerulonephritis
  > Glomeruli tend to be diffusely involved, with secondary tubular/interstitial changes
  <><><><>
  <><><><>
• Samoyed hereditary glomerulopathy
• familial glomerulonephritis of Doberman pinschers
• familial renal fibrosis of Norwegian elkhounds

Question 9

Renal dysplasia
- what is it?
- causes?
<><><>
- categories?
- gross appearance?
- clinical signs?

Answer 9

• disorganized development of the renal parenchyma due to anomalous differentiation
• usually congenital
  > in some species (dog, cat, pig), kidneys continue to develop after birth so some perinatal diseases can lead to the same lesions
  <><><>
  Types:
• development of anomalous structures
• the presence of structures that are inappropriate for the animal’s current stage of development
  <><>
• Grossly, the kidneys can be essentially normal, or be small, misshapen, and fibrotic.
• Animals with gross lesions of renal dysplasia usually develop uremia

Question 10

renal cysts
- significance
- mechanisms for development

Answer 10

• Single renal cysts are usually incidental lesions of no consequence
  <><><><>
  Mechanisms for developmment:
• obstructive lesions
• lesions in the tubular ECM matrix/basement membrane
• focal hyperplastic epithelial lesions
  > all of these result in an imbalance between the intratubular pressure and the strength of the tubule wall

Question 11

Polycystic kidney disease (PKD)
- etiology, forms, outcomes

Answer 11

• inherited polycystic disease described in many species/breeds
  <><><><>
  occurs in 3 forms:
• autosomal dominant form (ADPKD) occurs in Persian cats, bull terriers, pigs, and lambs
  > often concurrent hepatic and pancreatic cysts, sometimes with fibrosis
  > tend to be bilateral, arise in the convoluted tubules, progressively enlarge through life compressing adjacent normal parenchyma, and eventually result in renal failure with lesions of chronic tubulointerstitial nephritis
  <><>
• autosomal recessive form has been reported in Cairn terriers, West Highland white terriers, Persians, and sheep
  > biliary cysts occasionally occur in this form
  <><>
• congenital form of PKD (CPKD) has been described in pigs, lambs, goat kids, puppies, kittens, and foals
  > unknown mode of inheritance
  > hepatic and pancreatic cysts can also be present
  > often results in stillbirths or fatal renal failure in the first weeks of life

Question 12

renal infarction
- often arise how?
- possible sequelae?
- outcomes?

Answer 12

• They arise from thrombi or emboli in the renal artery or one of its branches, and often are secondary to valvular thrombosis / endocarditis
  <><>
• Septic thrombi result in abscesses which can resolve, become sequestered or drain into the renal pelvis
• Non-septic or bland thrombi produce the more classically described renal infarcts
  <><>
• Thrombosis of the renal artery will essentially cause necrosis of the entire kidney (there can be minimal collateral circulation from the capsular and perihilar vasculature)
• Involvement of the interlobar artery would give subtotal necrosis
• involvement of the arcuate or interlobular arteries gives the more common wedge-shaped lesion

Question 13

infarcted kidney - gross appearance and progression

Answer 13

• Initially affected tissue swells and is cyanotic with congestion due to blood oozing in from unaffected collateral vessels, which results in a poorly demarcated border between affected and unaffected tissue
• At the periphery, red cells survive resulting in a red rim (not truly hyperemia)
  > This lesion persists for 2-3 days, during which time normal circulation can be re- established
• After dehemoglobinization of the lesion (2-3 d) the infarcted region becomes pale in colour
  <><><><>
• Revascularization can occur in the peripheral areas, but the areas of complete necrosis undergo progressive fibrosis, becoming the pale white-tan-grey, sunken fibrotic lesions classically described in renal infarction

Question 14

Renal hemorrhage - how common? associated with what?

Answer 14

• frequent finding
• Petechiae with:
  > disseminated bacterial disease
  > viral disease
  > coagulation disorders

Question 15

hydronephrosis
- common?
- causes
- what typifies this condition
- outcomes / lesions?
- most severe forms are from what?

Answer 15

• common
• anything that occludes the ureters or urethra > can result in sufficient back pressure to cause the characteristics that typify this condition:
  > pelvic dilation
  > high fluid pressure of urine
  > renal compression and parenchymal loss
  <><><><>
• Back pressure and a nonexpansile capsule cause intrarenal pressure to increase, leading to ischemic lesions
  > Pressure and ischemia cause increased apoptosis of renal epithelial cells so that the cortex and medulla become reduced in size and the pelvis dilates
  <><><><>
• The most severe forms of hydronephrosis arise from unilateral incomplete obstruction

Question 16

general response of the inner renal medulla to ischemic insults
- when is this most seen?
- other possibilities?
- outcomes?

Answer 16

• Necrosis of the medullary crest or papillae
  (papillary necrosis)
• horses > administration of (NSAIDS) impairs prostaglandin production > juxtamedullary glomeruli cannot continue to supply blood to the medulla when required
  > prevents the protective effect of
  prostaglandin E2 on the medullary tubules and prevents the prostaglandin-based maintenance of medullary blood flow in situations of reduced renal blood flow such as in dehydration
  <><><>
• Similar disease can occur in cats and dogs with treatment or accidental ingestion of drugs such as ibuprofen or acetaminophen
  <><><><>
• generally, other conditions that cause reduction of blood flow to the area or direct compression can cause medullary crest/papillary necrosis
  > glomerular lesions (remembering that medullary flow comes from glomerular efferent arteries)
  > interstitial diseases such as fibrosis, interstitial inflammation, and edema, or amyloid that compress the vasa recta
  > compressive lesions like pelvic calculi or other causes of lower urinary tract obstruction.
  <><><><>
  Many instances of papillary necrosis are ‘incidental’ – few lead to clinical disease

Question 17

gross appearance of renal medullary necrosis?
possible sequelae?

Answer 17

• coagulation necrosis
  > well-demarcated area of yellow-green to grey to pink tissue
  > The necrotic tissue can slough, and, if large enough, can cause obstructions

Question 18

Medullary degeneration and necrosis
- when does it occur
- what are the body’s mechanisms to prevent this in situations of acute reduction in renal blood flow

Answer 18

• can occur due to prolonged dehydration
  <><><>
  Protective mechanisms
• effects PGE and nitric oxide in maintaining medullary blood flow
• reduction in metabolism of medullary epithelial cells in excessively hypoxic conditions

Question 19

end stage kidney - lesions, progression

Answer 19

• end result of all of the major diseases is renal fibrosis
  > follows pattern of initiating disease
  > a progressive and self-perpetuating lesion > restrictions of blood flow or the flow of filtrate soon result in secondary changes that exacerbate the fibrosis

Question 20

changes in the kidney associated with aging
- structural, functional, signs?

Answer 20

• decline in number of viable glomeruli
• increase in glomerulosclerosis
• increased interstitial fibrosis
• atrophic changes in tubules
• thickening of basement membranes
  > combine to result in reduced renal function
  <><><><>
• Kidney volume and weight can also decline, usually associated with thinning of the cortex
• Functionally:
  > reduced GFR
  > increased risk for/occurrence of hypertension
  > decreased ability to concentrate the urine
  > increase in vascular resistance
  <><><><>
• usually no clinically apparent disease, but can predispose to clinical problems of other disease (urinary or systemic)

Question 21

renal neoplasia
- usually primary or metastatic?
- species differences?

Answer 21

• usually metastatic
• horses: adenoma (benign) or carcinoma
• cats and dogs: renal carcinomas (metastatic)
• cats: renal lymphoma (malignant)
• pigs: nephroblastomas (benign usually)

Question 22

renal adenoma
- common?
- species?
- significance?

Answer 22

• rare
  > occasional finding in horses and cattle, less so in dogs
• usually incidental
• arise from the epithelium of the proximal convoluted tubules

Question 23

Renal carcinomas
- frequency? species?
- age? sex?

Answer 23

• cows, horses, and dogs: renal carcinomas are the most frequently observed primary renal tumour
• rare in cats, sheep, pigs
• older animals, male (except cattle > female, but more aged cows vs bulls…)

Question 24

clinical signs of renal carcinomas

Answer 24

• hematuria, weight loss, and palpable abdominal masses
• occasionally, paraneoplastic syndromes

Question 25

renal carcinomas, gross appearance? metastasis?

Answer 25

• ovoid to spherical
• unilateral
• often found at one pole of the kidney
• often grey to yellow with significant areas of hemorrhage and necrosis and can grow to be larger than the kidney it arose from
• neoplastic tissue is usually well demarcated from normal renal tissue
  <><>
• tumours often invade renal veins and lymphatics, and metastasis is common, often present at time of diagnosis

Question 26

Renal cystadenocarcinomas
- breeds?
- concurrent conditions?
- malignant?
- etiology

Answer 26

• Older German shepherd dogs
• in combination with nodular dermatofibrosis
• generally bilateral
• malignant forms often metastasizing to lymph nodes, liver, spleen, lung, and bone
• Females often have concurrent uterine leiomyomas
• autosomal dominant inheritance

Question 27

Nephroblastoma
- common for who?
- etiology
- appearance
- metastasis?

Answer 27

• AKA embryonal nephromas or Wilms’ tumour
• most common primary renal tumour in pigs and chickens
• arise from the primitive nephrogenic tissue and as such are usually seen in animals under 2 years of age but can arise in foci of renal dysplasia
  <><><><>
• often bilateral and multiple within affected kidneys,
• grow to enormous sizes leading to abdominal distension
• often contain tissue components not normally found in renal tissue such as cartilage, bone, collagen, adipose tissue, and skeletal muscle
• metastasis rare in pigs, does occur in affected cats and dogs