Common Diagnostic Tests: Blood Work, X-Rays, Ultrasound

Why Diagnostics Matter

Physical examination is a powerful tool, but it has limits. A vet can feel that an abdomen is painful, but not what is causing the pain. They can hear an abnormal heart sound, but not see exactly which valve is affected or how severely the heart muscle is compromised. Diagnostic tests extend the vet's ability to see inside the body — identifying what is wrong, how serious it is, and how best to treat it.

Understanding what each test looks for helps you participate meaningfully in conversations about your pet's care and make informed decisions about which tests are worth pursuing given your pet's specific situation. Book a vet appointment at Happy Paws whenever you notice concerning symptoms in your pet.

Blood Work: What Each Panel Measures

Complete Blood Count (CBC): Measures the cells in the bloodstream.

Red blood cells (RBC) and hemoglobin — detects anemia (too few) or polycythemia (too many)
White blood cells (WBC) — elevated suggests infection or inflammation; very low suggests immune suppression or bone marrow disease
Platelets — low platelets cause bleeding problems; assessed before surgery

Biochemistry Profile (Chem Panel): Evaluates organ function using substances in the blood.

BUN and creatinine — kidney function markers; elevated suggests kidney disease or dehydration
ALT and ALP — liver enzymes; elevated indicates liver stress or disease
Blood glucose — elevated in diabetes; low in insulinoma or insulin overdose
Albumin and total protein — markers of nutrition, liver function, and protein-losing diseases
Electrolytes (sodium, potassium, chloride) — critical for kidney disease, Addison's disease, heart disease management

Thyroid (T4): Evaluates thyroid hormone levels. Hyperthyroidism (high T4) is very common in older cats. Hypothyroidism (low T4) is the most common hormonal disease in dogs.

Urinalysis: A urine sample reveals kidney concentrating ability, signs of infection, crystals, glucose, blood, and protein — often the earliest indicators of kidney disease before blood markers change.

Imaging: X-Ray (Radiography)

X-rays (radiographs) use ionizing radiation to create images of internal structures. Dense structures (bone) appear white; air-filled structures (lungs) appear black; soft tissues appear in intermediate shades of gray.

X-rays are excellent for:

Bone — fractures, joint changes, bone tumors, hip dysplasia grading
Thorax (chest) — heart size and shape, lung disease (fluid, pneumonia, masses)
Abdomen — organ size, foreign body ingestion, gas patterns suggesting obstruction or bloat
Dental — root disease, bone loss, retained teeth (dental X-rays are a separate specialized equipment)

X-rays provide less detail for soft tissue structures (abdominal organs like the liver or spleen) than ultrasound, but they excel at showing the overall picture and bone structures.

Imaging: Ultrasound

Ultrasound uses high-frequency sound waves to create real-time images of soft tissue structures. The probe is placed on the skin surface (fur may need to be shaved over the area) and bounces sound waves off internal structures to build a moving image.

Ultrasound is excellent for:

Evaluating abdominal organ internal structure — the liver, spleen, kidneys, adrenal glands, lymph nodes, bladder
Detecting masses within organs
Guided fine needle aspiration — using ultrasound to safely guide a needle into a mass or organ to collect cells for analysis
Cardiac ultrasound (echocardiography) — measuring heart chamber size, wall thickness, valve function, and blood flow
Detecting free fluid in the abdomen or chest
Pregnancy confirmation and monitoring

Advanced Imaging: CT and MRI

CT (Computed Tomography): A series of X-ray slices processed into 3D images. Excellent for bone detail, thoracic disease, and surgical planning. Requires anesthesia in pets. Faster than MRI.
MRI (Magnetic Resonance Imaging): Uses magnetic fields rather than radiation. The gold standard for brain and spinal cord imaging, soft tissue masses, and complex orthopedic assessment. Requires anesthesia in pets. Takes longer than CT.

These advanced modalities are typically performed by or in consultation with a veterinary radiologist at a referral center. Track all diagnostic results and imaging reports in My Pets on TailRounds for a complete, organized medical record.