How investigations work
Tests explained
What different investigations can show, why a vet might suggest them, what they can’t tell us, and what you can expect. Every pet is different — your vet will explain what’s relevant for yours.
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Laboratory tests on samples
Blood and urine tests
Often one of the first steps. They give a broad picture of general health and how organs such as the kidneys and liver are working.
What it can show
- Signs of infection, inflammation or anaemia
- How well the kidneys and liver are working
- Crystals, blood or infection in the urine
- Whether a pet is likely to be fit for an anaesthetic
Why a vet might recommend it
- To look for clues about the cause of illness
- To check general health before sedation or anaesthesia
- To monitor a known condition or treatment
Limitations
- Results are often non-specific — they point in a direction rather than give a diagnosis
- Normal results don't rule out all problems
Possible alternatives
- Often used alongside imaging rather than instead of it
What you can expect
- A small blood sample is usually taken from a vein in the leg or neck
- Urine may be collected at home, or directly from the bladder with a fine needle
- Some results are available the same day; others take longer
Still pictures using X-rays
X-rays (radiography)
A widely available way to look at bones, the chest and some abdominal problems.
What it can show
- Fractures and many bone or joint changes
- The size and shape of the heart and lungs
- Many — but not all — swallowed objects and bladder stones
Why a vet might recommend it
- As a quick first look at the chest, abdomen or skeleton
- To check for some foreign objects or stones
Limitations
- Structures overlap, which can hide detail — especially in the skull and nose
- Soft tissues are harder to tell apart
- Some stone types and objects don't show up
Possible alternatives
- Ultrasound for abdominal organs
- CT for more detail, particularly of the head and chest
What you can expect
- Your pet usually needs to keep still in particular positions
- Sedation is often used to keep pets calm and comfortable, and to get clear images
A moving picture using sound waves
Ultrasound
Uses sound waves to look at soft organs in real time, particularly in the abdomen and heart.
What it can show
- The structure of the liver, kidneys, spleen, bladder and intestines
- The thickness and layers of the gut wall
- Fluid in the abdomen or around the heart
- Some stones that are hard to see on X-ray
Why a vet might recommend it
- To look at abdominal organs in more detail
- To guide a needle to take samples
- To assess the heart (echocardiography)
Limitations
- Sound waves can't pass through air or bone, so it's less useful for the lungs, nose and skull
- Images depend on the operator and the patient
- Can't always say what a change is without samples
Possible alternatives
- CT for areas ultrasound can't reach
- X-rays for an overview
What you can expect
- A patch of fur is usually clipped so the probe can touch the skin
- Many pets are scanned awake or with light sedation
- It's painless, though lying still can be tricky for some pets
A detailed 3D X-ray scan
CT scan
Combines many X-ray images into detailed cross-sections and 3D views of the body.
What it can show
- Fine detail inside the nose, sinuses and skull
- The chest and lungs
- Bones and joints
- The extent of a problem, to help plan treatment or surgery
Why a vet might recommend it
- When X-rays or ultrasound don't give enough detail
- To investigate nasal disease before rhinoscopy
- To plan surgery
Limitations
- Shows structure, not the surface of linings
- Often can't confirm exactly what a change is without samples
- Not available at every practice
Possible alternatives
- X-rays
- Ultrasound
- MRI for some brain, spinal and soft-tissue questions
What you can expect
- Your pet must be completely still, so a general anaesthetic or heavy sedation is usually needed
- A contrast agent may be injected into a vein to highlight certain tissues
- The scan itself is usually quick
A camera examination inside hollow organs
Endoscopy
A camera on a flexible tube is used to look at the inside of the gut or airways, and to take samples.
What it can show
- Inflammation, ulcers and lumps on the lining
- Swallowed objects
- Narrowing of the gullet
Why a vet might recommend it
- To see the lining directly and take biopsies
- To retrieve some swallowed objects without open surgery
Limitations
- Only sees the inner surface
- Some areas are out of reach
- Small biopsies can miss deeper changes
Possible alternatives
- Ultrasound
- Surgical biopsies
- Diet trials or treatment with review
What you can expect
- Fasting beforehand
- General anaesthetic
- Biopsy results usually take several days
A camera examination inside the nose
Rhinoscopy
A small camera is used to look inside the nasal passages, take samples and sometimes remove foreign objects.
What it can show
- Foreign objects such as grass seeds
- Inflammation, fungal plaques or abnormal tissue
Why a vet might recommend it
- Persistent nasal discharge, sneezing or nosebleeds not explained by simpler tests
- To take targeted samples, often after a CT scan
Limitations
- Some areas, including parts of the sinuses, are hard to see
- Bleeding can obscure the view
Possible alternatives
- CT alone
- X-rays
- Monitoring or treatment trials where appropriate
What you can expect
- General anaesthetic
- Some sneezing and mild nosebleeds for a short time afterwards are common
A camera examination of the bladder
Cystoscopy
A thin camera is passed along the urethra to look inside the bladder and, in some cases, remove small stones.
What it can show
- Stones, inflammation or growths in the bladder and urethra
- Some abnormalities present from birth
Why a vet might recommend it
- Recurrent urinary signs not explained by other tests
- To remove small stones or take samples
Limitations
- Limited by the size of the urethra — generally easier in females
- Larger stones may need another approach
Possible alternatives
- Ultrasound
- X-rays
- Surgery
What you can expect
- General anaesthetic
- Some pets have mild blood in the urine for a short time afterwards
Looking at tissue under a microscope
Biopsy and laboratory analysis
Small pieces of tissue are examined by a pathologist to understand what a change actually is.
What it can show
- Whether tissue is inflamed, infected or abnormal
- The type of a growth, which helps guide treatment
Why a vet might recommend it
- When imaging or a camera examination finds something that needs identifying
Limitations
- Small samples may not represent the whole area
- Some results are inconclusive
- Results take time — often several days
Possible alternatives
- Needle samples (cytology), which are less invasive but give less information
What you can expect
- Samples are usually taken during endoscopy, surgery or with a needle
- Your vet will contact you when the report is back
A keyhole camera examination of the abdomen
Laparoscopy
A camera is passed through a small incision to look inside the abdomen and, in some cases, take samples or perform surgery.
What it can show
- The surface of abdominal organs such as the liver
- Areas that may need sampling
Why a vet might recommend it
- To take biopsies of some organs through small incisions
- As part of certain keyhole surgical procedures
Limitations
- Requires specialist equipment and training
- Not suitable for every patient or problem
- May need to be converted to open surgery
Possible alternatives
- Ultrasound-guided needle samples
- Open surgery
What you can expect
- General anaesthetic
- Small wounds that still need rest and checks during healing