General Medicine
The Annual Health Check: What Is Worth Testing
A useful yearly check is six or seven cheap tests, not a fifty-test package. What to ask for at each age, what to skip, and how to read the report.
30 Aug 202610 min read
CT scan
Also known as Computed tomography, CAT scan
A CT scan uses X-rays taken from many angles and reassembled by computer into cross-sectional images of the body. It is fast and detailed, which makes it the scan of choice in emergencies, and it delivers a meaningfully higher radiation dose than a plain X-ray.
The patient lies on a table that slides through a short ring while an X-ray tube rotates around them. Software turns those projections into slices, and the slices into a three-dimensional picture in which bone, blood, air, fat and soft tissue can be told apart. A scan of the head takes seconds; most others take a few minutes, and the whole appointment is usually under half an hour.
How the test is done
- Preparation is usually nothing more than removing metal. Fasting for a few hours is asked only when contrast is planned, and some abdominal scans need a drink of oral contrast an hour beforehand.
- Contrast is an iodine-based dye injected into a vein to light up blood vessels, inflammation and tumours. It causes a warm flush and a metallic taste that pass in moments. Tell the staff about kidney disease, any previous reaction to contrast, and metformin, because the dose may need adjusting.
- The scan itself is painless and you are alone in the room but in constant contact. You will be asked to hold your breath for a few seconds at a time.
- Tell the staff if you might be pregnant. CT is avoided in pregnancy unless the information cannot be obtained another way.
Radiation is the honest trade-off. A chest is a small fraction of a millisievert; a CT of the abdomen is several millisieverts, comparable to a couple of years of natural background exposure. For a suspected stroke, a serious injury, an internal bleed or a possible clot in the lung that is an easy trade. For a vague ache in a young person it is not, and an or an , neither of which uses radiation, often answers the same question. It is reasonable to ask what a scan will change before agreeing to it.
Where this comes up
Neurology
Stroke: The Warning Signs and Why Every Minute Counts
Face drooping, arm weakness, speech trouble — any one of them, appearing suddenly, is a stroke until proven otherwise. Call 1122 and note the time.
28 Aug 202611 min read
Pulmonology
A Cough That Will Not Go: When to Worry and What Causes It
In Pakistan a cough lasting two weeks or more should be tested for tuberculosis. What else causes a long cough, and the signs that mean see a doctor now.
27 Aug 202610 min read
Orthopedics
Low Back Pain: Causes, Treatment and When to Worry
Most low back pain settles within six weeks without a scan. What genuinely helps, what to skip, and the warning signs that need same-day care.
11 Aug 202610 min read
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Related terms
- MRIMagnetic resonance imagingAn MRI scan uses a strong magnetic field and radio waves to build detailed images of soft tissue. It involves no X-rays and no radiation.
- X-rayRadiograph, Plain filmAn X-ray uses a small dose of radiation to produce an image, and it is best at showing bone and the chest. It is quick, widely available and usually the first imaging test requested.
- UltrasoundSonography, Ultrasound scanAn ultrasound scan builds images from high-frequency sound waves reflected back off the body's tissues. It uses no radiation, which is why it is the scan used in pregnancy.
- StrokeCerebrovascular accident, CVAA stroke is a sudden loss of blood supply to part of the brain, either from a blocked artery or a bleed. It is an emergency — treatment works only within a few hours of the first symptom.