Urine crystals and uroliths

What is found in urine sediment

• Crystals e.g. calcium oxalate, struvite 

• Bacteria and WBCs 

• Yeast 

• Blood 

• Sperm 

• Epithelial cells 

• Neoplasia 

What is the method for prepping sediment

• Sediment samples should be spun via a centrifuge 

• 1000-1500 for 5 minutes 

• Remove the supernatant and re-suspend sample 

• Pipette sample onto slide and place cover slip  

Are RBCs in urine normal

• <5 RBCs in field is normal

• Must consider how we got sample as can have caused bleeding thru cysto and urinary catheter as are traumatic ways to get urine 

• Can be iatrogenic 

What does iatrogenic mean

Relating to illness caused by medical examination or treatment

How to identify RBCs under microscope

• All similar size

• All similar colouring

Are WBCs in urine normal

• <5 WBcs in field in normal urine 

• >5 is called Pyuria- inflammation, infection, trauma, neoplasia 

• Presence can be due to contamination depending on how we obtained urine sample 

• If cysto or catheter WBCs should not be there 

What are the 4 different types of epithelial cells

• Transitional

• Squamous

• Neoplastic

• Neoplastic squamous

What are the characteristics of transitional epithelial cells

• Common

• Grainy cytoplasm

• Central nucleus

• Shouldn’t see loads

Where can we find squamous epithelial cells

• In free catch sample

• In expressed sample

Where can we find neoplastic epithelial cells

• In transitional cell carcinomas

Where can we find neoplastic squamous cells

• In squamous cell carcinomas

Example of neoplastic cells

What are casts

Mucoproteins

Where can we see casts

• Only on unstained slides

What are the 5 types of casts

• Hyaline

• Epithelial

• Granular

• Waxy

• RBC and WBC

• Fatty-lipid

What are the characteristics of hyaline casts

• Parallel sides

• Rounded ends

• Mucoprotein

• A few are normal

• Associated with proteinuria

What are the characteristics of epithelial casts

• Entrapment of sloughed cells in mucoprotein

• Aka acute red tubular disease

What are the characteristics of granular casts

• Degenerated epithelial cellular casts

• Few is normal

• Indicate acute renal disease/damage

What are the characteristics of waxy casts

• Degeneration of granular/cellular casts

• Never normal

What are the characteristics of RBC and WBC casts

• Always abnormal

• RBC-renal haemorrhage

• WBC-renal inflammation

What are the characteristics of fatty lipid casts

• Accumulate in kidneys

Cast images

UPLOAD IMAGE 49

What are the characteristics of bacteria

• If cystocentesis is obtained and bacteria present—>infection

• Free catch or expression= could be contamination but if large number and the same in appearance can be infection, will need more testing 

• Rods most easily identified 

• Confirm with gram stain or aerobic culture 

What are the characteristics of yeast

• Often result of contamination unless cysto or catheter then will indicate a yeast infection as there is no contaminated sample 

• Round to oval 

• Colourless 

• Usually treated with long term antibiotics  

What are the characteristics fungal hyphae

• Very rare 

• Most commonly due to contaminates overgrowth 

• Fungal infection can occur with aspergillus terreus-systemic infection including renal pelvis colonization 

What are the characteristics of lipids

• Common 

• Can be mistaken for RBCs 

• Vary in size 

• Most common in cats 

Where can you find sperm in urine

• Males

• Recently bred females

Where can you find plant material

• Debris in contaminated samples

• samples collected from floor or litter trays

What affects crystal formation

• Urine pH

• Concentration of crystal forming minerals

• Urine temp

• Length of time between collection and examination

• Not necessarily pathologic

What are the 7 types of crystals

• Struvite

• Calcium oxalate

• Calcium carbonate

• Ammonium urate

• Uric acid

• Cysteine

• Billirubin

What are the properties of struvite crystals

• Forms in alkaline urine

• Common in cats and dogs

• Dogs have a bacterial element to struvite crystals but cats don’t

• In dogs- struvite+UTI—>urolith

• Felines don’t get UTI (no bacterial element)—> no urolith

• Coffin lid/prism shaped

• Can treat with acidifying diets

What is the veterinary name for struvite crystals

Magnesium ammonium phosphate

What are the properties of calcium oxalate crystals

• Normally formed in acidic urine

• Common in healthy horses but less common in SA

• Form in stored urine

• Increased risk of urolith formation

• Can occur due to hypercalcemia and or renal injury

What s the veterinary name for calcium oxalate crystals

Dihydrate

What are the properties of calcium carbonate crystals

• Horses, rabbits and guinea pigs

• Alkaline pH

• Cause uroliths in guinea pigs

• Rare in dogs/cats

• Large circular crystals

• Smaller-pairs/tetrads

• Slightly brown

What are the properties of ammonium urate crystals

• Acidic urine

• Never normal

• Birds, dogs, reptiles

• Caused by liver disease (e.g. PSS)

• Certain breeds e.g. Dalmatians, bulldogs, Black Russian terriers

• Yellow/brwon

• Irregular, spiny projections

What are the properties of uric acid

• Formed in acidic urine

• Dalmatians are predisposed as can’t convert uric acid to allantoin (purine metabolism)

What are the properties of cysteine crystals

• Acidic urine

• Many breeds of dogs, ferrets

• Rarely cats

• Proximal tubular defect in amino acid resorption

• Six sided

• Variable in size

What are the properties of bilirubin

• Normal in dogs, cats

• Due to bilirubinuria—> due to cholestasis or haemolysis

• Detected on dipstick

• Brown

• Urchin shaped crystals

What are the 4 types of uroliths

• Struvite

• Calcium oxalate

• Urate

• Cysteine

Where are struvite uroliths most common

• Female dogs (associated with infection)

• Male cats

Where are calcium oxalate uroliths most common

• MN, obese dogs, monohydrate

• MN, obese cats, dihydrate

Where are urate uroliths most common

Males

What are properties of urate uroliths

• Uric acid 

• Xanthine 

• Very uncommon 

• Normally dogs treated with allopurinol 

Where are cysteine uroiths most common

• Male dogs

• Middle aged terriers