Urinary Pathology

Question 0

What is acute tubular necrosis?

Answer 0

Results from ischaemic or toxic insult to renal tubular epithelial cells. The PCT has a high metabolic rate and therefore is most susceptible to injury, especially from toxins . Degeneration > necrosis > desquamation. ATN often results in oligura/anuria due to intratubular obstruction, leakage of urine to the interstitium, activation of the renin agiotensin system.

Question 1

What is glomerulitis?

Answer 1

suppurative glomerulitis - caused by bacteraemia > localisation of bacteria wi thin glomeruli and interstitial capillaries. Viral: some viruses can attack capillary endothelium in glomeruli > swelling (eg infectious canine hepatitis).

Question 2

Describe the different subtypes of ATN (acute tubular necrosis)

Answer 2

1)ischaemic/tubulorrhectic ATN - e.g severe hypotension - Haemoglobinurea can complicate this. This form is more likely to cause basement membrane damage. 2). Nephrotoxic ATN - h heavy metals, oxalates, excreted through kidneys and precipitate as crystals in the kidneys causing damage, obstruction and uraemia. Antibacterials, oak/acorns - contain oak tannins which are toxic to kidneys.

Question 3

What are tubulointerstitial diseases?

Answer 3

Diseases affecting tubules and thee interstitium. This can arise as a consequence of systemic viral/bacterial disease. Grossly lesions can be diffuse or multifocal and acute subacute or chronic. Eg Leptospira canicola, infectious canine hepatitis virus, E. coli septicaemia, malignant catarrhal fever.

Question 4

Describe how leptospira canicola causes tubulointerstitial disease

Answer 4

Exposure to the organism followed by bacteraemia > localisation in the renal capillaries> migration through the vascular endothelium into the renal interstitium > migration through intercellular junctions of renal tubular epithelial cells > tubular lumen and become associated with the epithelial microvilli > persistence (within phagosomes of CT and DCT) > degeneration of epithelial cells.

Question 5

What is granulomatous nephritis?

Answer 5

Granulomatous nephritis usually accompanies chronic systemic diseases characterised by the formation of multiple granulomas. A good example of this is in cats with feline infectious peritonitis. Multiple granulomas are particularly a feature in ‘dry’ form. The lesions are present as multiple irregular cortical foci which bulge from the capsular surface.

Question 6

What is Dictophyma Renale?

Answer 6

Giant kidney worm in fish eating mammals - resides in renal pelvis causing haemorrhage, inflammation and obstruction > hydronephrosis. NB toxocara migrating toxocara canis larvae can also induce small 2-3mm granulomas throughout the subcapsular renal cortex.

Question 7

What is pyelonephritis?

Answer 7

Inflammation of both the renal pelvis and the renal parenchyma and is associated with suppurative tubulo interstitial inflammation. Pyelonephritis usually arises as an ascending infection from the lower urinary tract establishing infection in the renal pelvis and inner medulla. rarely, pyelonephritis can result from descending bacterial infection.

Question 8

Describe the gross appearance of pyelonephritis

Answer 8

The pelvis contains variable amounts of mucupus and the medulla exhibits streaks of inflammatory debris which extend into the kidney substance. It is often bilateral and in crhonic cases the kidneys are markedly deformed due to the ongoing inflammation and scarring.

Question 9

Describe the histological appearance Of pyelonephritis

Answer 9

Organisms are present in the tubules which become involved in a vigorous inflammatory reaction arising in the interstitial tissue. In ascending infection, glomerular involvement tends to be confined to degeneration and fibrosis of bowman’s capsule. In long standing cases fibrosis dominates the picture.

Question 10

Which Primary renal tumours can occur?

Answer 10

Renal adenocarcinoma: the most common primary neoplasm. Usually unilateral but Occassionally bilateral. Commonly metastasise to the lung. Renal Adenoma: usually incidental, small, rare. Nephrobastoma: most common primary renal tumour of pigs. Embryonal tumour of mesenchymal origin. Occasionally also primary haemangiosarcomas, fibromas/fibrosarcomas can arise.

Question 11

Name potential metastatic renal tumours

Answer 11

Lymphosarcoma - common in cats and cattle. Haemangiosarcoma - malignant melanoma, mammary adenocarcinoma.

Question 12

What is an ectopic ureteter?

Answer 12

The most important ureteral anomaly. Most common in females with opening into the bladder neck, urethra or vagina. The resulting incontinence can be cured surgically. Ectopic ureters are more prone to obstruction/infection.

Question 13

What is a patent urachus?

Answer 13

Failure of seal between the bladder and umbilicus at birth resulting in a direct channel between the bladder apex and the umbilicus. Increased susceptibility to infection. Commonest in foals.

Question 14

What are diverticuli of the bladder?

Answer 14

Cogenitally weak areas of the bladder wall usually at the vertex, can progress to cystitis.

Question 15

Describe potential bladder displacements

Answer 15

Retroflexion: sequel of vaginal prolapse, perineal hernia. can be a serious complication of perineal hernia resulting in a hydronephrosis or bladder rupture. Neuromuscular dysfunction - reflex dyssynergia - failure of sphincter relaxation during micturition.

Question 16

What is Cystitis?

Answer 16

The usual cause of cystitis is bacterial infection from the urethra. Predisposing factors include urine stagnation and epithelial trauma. A variety of bacterial pathogens can be involved. Important in large animals are C.renale and E suis. Note that pathological urine can be a better growth medium for bacteria e.g glucosuria.

Question 17

Describe Acute Cystitis

Answer 17

Described by the dominant morphological features i.e haemorrhagic, fibrinopurulent, necrotising, ulcerative - there may be a progression through these types in severe cases. The histopathoogy is characterised by acute inflammation oedema of the lamina propria and superficial hyperaemia/haemorrhage. Urine is often thick, foul smelling and haemorrhagic.

Question 18

Describe Chronic Cystitis

Answer 18

Diffuse: Thickened mucosa, thickened submucosa and in some cases hypertrophy of t he muscularis. Inflammatory reaction is dominated by mononuclear cells. Follicular: multifocal nodular proliferation of mononuclear cells. The nodules may be surrounded by a thin zone of hyperaemia. Polypoid: most common in the bitch, single or multiple discrete polypoid masses resulting from chronic infection or chronic urolithiasis.

Question 19

Describe Emphysematous Cystitis

Answer 19

Develops in some dogs and cats with diabetes mellitus - relates to fermentation of sugar by glucose fermenting bacteria.

Question 20

What is Mycotic Cystitis

Answer 20

Colonisation of bladder by opportunistic fungi e.g following prolonged antibacterial therapy, immunosuppression. Can cause extensive inflammation and ulceration.

Question 21

What is Urolithiasis?

Answer 21

Urinary calculi - Concretions formed in the urinary tract - most commonly in the bladder lumen. Urolithiasis occurs in both males and females, however urinary obstruction caused by calculi is much more common in males due to the anatomy of the lower urinary tract.

Question 22

What are the most common sites of obstruction?

Answer 22

Dogs: Base of os penis
Bulls: Ischial arch, proximal end of sigmoid flexure
Rams: Vermiform appendage
Cats: Urethra generally

Question 23

What is Enzootic Haematuria (Neoplasia)

Answer 23

A syndrome characterised by persistent Haematuria and anaemia as a result of haemorrhages or neoplasms within the lower urinary tract. This is caused by chronic ingestion of bracken fern which contains several toxic substances. Ectasia and engorgement of capillaries occurs and these vessels are prone to haemorrhage. The tumours occur chiefly in the bladder but can also occur in the renal pelvis, ureter and liver.

Question 24

What is Transitional Cell Carcinoma

Answer 24

This neoplasm spreads through and along the bladder wall destroying the epithelium and invading the muscle layers. Metastases to regional nodes and lungs occur in approximately 50% of cases. Peritoneal implantation or retrograde spread to soft tissue/bone of hindlimbs can also occur.

Question 25

What is a Leiomyoma of the bladder

Answer 25

Common, it occurs in the smooth muscle of the bladder wall forming well defined white nodular projections. The consequences of this benign tumour depend on its location.

Question 26

What is botyroid Rhabdomyosarcoma

Answer 26

Occurs in the bladder of young large breed dogs. Origin may be embryonic myoblasts. Usually occurs at the trigone of the bladder as large fungating mass which is infiltrative and can metastasise.

Question 27

Describe normal prostatic cytology

Answer 27

Normal prostatic epithelial cells occur in small/medium sized clusters - regular centrally placed nuclei. Cells of non-prostatic origin which may also be evident are sperm and squamous cells.

Question 28

Describe hyperplastic and metaplastic change of the prostate (benign prostatic hyperplasia).

Answer 28

The prostate gland slowly increases in size under the influence of testosterone. The prostate is usually diffusely involved and may contain cysts. The enlargement of the prostate gland may be associated with constipation due to physical pressure on the rectum. Much less commonly, there may be interference with the urinary tract manifesting as dysuria.

Question 29

What is squamous metapasia of the prostate?

Answer 29

Squamous metaplasia of the prostatic epithelium occurs in the dog following oestrogen administration or concurrently with testicular neoplasia. This change results in conversion of the prostatic epithelium to stratified squamous epithelium and there is a predisposition of the prostate to inflammation.

Question 30

Describe suppurative prostatitis/prostatic abscess

Answer 30

Prostatitis can occur either in conjunction with BPH or as a primary disease entity. The prostate may be diffusely or focally involved with signs typical of acute or chronic inflammation. Prostatic abscessation can occur as a sequel to prostatitis.

Question 31

What are prostatic/paraprostatic cysts?

Answer 31

Prostatic cysts may be congenital or arise secondary to hyperplasia, inflammation or neoplasia. Paraprostatic cysts which are thought to be a developmental anomaly can reach a large size. (15cm) and are lined by a secretory epithelium

Question 32

Describe Prostatic Neoplasia

Answer 32

The commenest form is prostatic adenocarcinoma in old dogs. It can also occur in male cats rarely. Usually highly Aggressive and often metastasise to regional nodes and parenchymatous organs. Additionally these are capable of metastasising to lower lumber vertebrae, pelvis, hindlimbs.