Pathology of kidneys & lower UTI Flashcards
What are the 2 pathways an infection of the kidney can follow?
Haematogenous (descending)
Urinary (ascending)
Give examples of causes of infectious diseases of the kidney
Viral: Canine herpesvirus 1, Canine Adenovirus 1, Ovine Herpesvirus 2
Bacterial: Leptospira interrogans, Actinobacillus equuli, Escherichia coli, Corynebacterium renale
Parasitic: Toxocara canis, Halicephalobus gingivalis, Encephalitozoon cuniculi, Leishmania spp
What are the 2 types of nephritis?
Non-suppurative tubulointerstitial nephritis
- Lympho-histiocytic inflammation
Suppurative interstitial nephritis
- Embolic nephritis (Haematogenous)
- Pyelonephritis (Ascending) (Inflammation in both pelvis & renal parenchyma)
What are the main causes of non-suppurative tubulointerstitial nephritis?
Leptospira interrogans, Escherichia coli, Maedi-Visna virus, FIP virus, Canine herpesvirus 1, Canine Adenovirus 1, Ovine Herpesvirus 2, Encephalitozoon cuniculi
How do kidneys appear in acute and chronic non-suppurative tubulointerstitial nephritis?
Acute nephritis:
Swollen, pale tan kidneys.
Random gray mottling on capsular surface.
Chronic nephritis:
Fibrotic kidneys
What are the histological features of acute and chronic non-suppurative tubulointerstitial nephritis?
Acute:
Interstitial oedema, mononuclear infiltration, tubular degeneration & necrosis
Chronic:
Mononuclear cell infiltration (lymphocytes, plasma cells, histiocytes).
Interstitial fibrosis & tubular atrophy
What is suppurative embolic nephritis and what causes it?
Septic emboli lodge in glomerular/peritubular capillaries, leading to microabscesses
- larger emboli lodge in arteries & cause septic infarcts
Common causes:
Actinobacillus equuli (foals)
Erysipelothrix rhusiopathiae
Trueperella pyogenes
What are the main causes of pyelonephritis?
Endogenous bacteria of bowel & skin:
- Escherichia coli, Staphylococci, Streptococci, Enterobacter, Proteus, Pseudomonas
Specific pathogens of urinary tract:
- Corynebacterium renale (cattle)
- Actinobaculum suis (swine)
How does pyelonephritis develop?
Ascending infection → Bacteria ascend from lower urinary tract due to vesicoureteral reflux
Establishes infection in renal pelvis & spreads into medulla
What are the gross lesions of pyelonephritis?
Pelvic mucosa: Inflamed, thickened, exudate-coated
Papillae: Ulcerated, necrotic
Renal medulla: Irregular red or grey radial streaks extending from pelvis
What are the microscopic features of pyelonephritis?
Transitional epithelium: Necrotic, sloughed, covered in debris, fibrin, neutrophils & bacterial colonies
Medullary tubules: Dilated, filled with neutrophils & bacterial colonies
Chronic lesions: Severe fibrosis
What are the main pathways of lower urinary tract infections?
Descending (originating from nephritis or pyelonephritis)
Ascending (originating from urethra)
What are the 3 most common lower urinary tract infections?
Ureteritis (usually secondary to cystitis)
Cystitis (Most common, affects the bladder)
Urethritis (Often due to urinary obstruction or urethral plugs)
What are the common bacterial causes of cystitis?
Escherichia coli, Proteus vulgaris, streptococci, staphylococci, enterococci
Bacteria ascend from urethra, usually from rectal or cutaneous flora
What are the predisposing factors for cyctitis?
Urine stagnation (obstruction, incomplete bladder emptying)
Urothelial trauma (uroliths, catheterization, vaginoscopy)
Urinary incontinence, diabetes mellitus, antibiotic/corticosteroid use, hyperoestrogenism, immunodepression
Gender (shorter urethra in females)
Comorbidities (e.g., pyometra, prostatitis)
What are the defense mechanisms of the bladder against infection?
Urothelial barrier
Urine pH and osmolality
IgA, IgG, Tamm-Horsfall mucoprotein
Shedding of infected urothelial cells
What are the gross pathological forms of cystitis?
Acute:
Haemorrhagic, catarrhal, fibrinopurulent, necrotizing, ulcerative
Chronic:
Diffuse, follicular, polypoid (often associated with chronic infection or urolithiasis).
Emphysematous (associated with glycosuria)
What are the histological features of acute ulcerative cystitis?
Ulceration, inflammatory infiltrate and hyperaemia
What are the histological features of chronic follicular cystitis?
Aggregate of proliferating lymphocytes designing a lymphoid follicle.
What are the histological features of chronic polypoid cystitis
Polypoid (villus-like) projections covered by epithelium
Core of proliferated connective tissue with:
- Dense inflammatory infiltrate
- Haemorrhage
- Hemosiderin deposits
Epithelial down-growths appearing round in cross-section
What are some common non-infectious causes of cystitis in different species
What are the main categories of urinary tract pathology?
Tubulointerstitial nephritis
Neoplasia
Lesions secondary to renal failure
What is tubulointerstitial nephritis
Diseases involving primarily the interstitium and tubules
What are the main types of tubulointerstitial nephritis?
Non-suppurative (haematogenous or ascending)
Embolic suppurative (haematogenous, bacterial septic emboli)
Pyelonephritis (mostly ascending infection)
