Chapter 14

With contributions from Dr Rahul Mukherjee

Radiology is central to the clinical practice of medicine. Information gained from different imaging modalities can be used for diagnosis, monitoring treatment, assessing progression and detecting relapses of a wide variety of medical conditions in a minimally invasive and anatomically precise manner. As a junior doctor, you will spend much of your time requesting radiological investigations and explaining the results to patients. Many of the following guidelines come from the Royal College of Radiologists. Your hospital may also have its own which you should follow.

Requesting investigations

Radiology registrars are notorious for grilling you on exactly why a scan is required and how it is going to change your management plan. Radiologists have a duty not to expose a patient to unnecessary radiation. Scanners and radiographers are often overstretched resulting in some reluctance on the part of radiology staff to perform unjustified investigations. Take this as a learning exercise and a challenging opportunity to practice your communication skills. The ability to convince a reluctant radiologist to agree to a scan is a rite of passage! It saves a lot of time if you can supply logical and clinically coherent answers, so don’t be shy to ask your seniors why the investigation is needed and what you expect to find. If it isn’t clear to you then it probably won’t be clear to radiology either. By asking your seniors, you will also reinforce your understanding of the indications for certain investigations.

  1. Always book procedures as early as possible. Most radiological departments are overbooked. This is particularly true for contrast studies, CTs and particularly magnetic resonance imagings (MRIs). For urgent studies needed on the same day, it is usually best to go down to the department and speak to a radiologist face-to-face early on in the day. In some hospitals, approvals for specialized scans such as MRIs can only come from a registrar or even a consultant. It is best to prepare yourself beforehand with the patient’s details, brief history, results of investigations so far, differential diagnoses and why you think the scan will help to either make the diagnosis or change the management plan.
  2. The following information must be included on the radiology request form.

    • Patient ID.
    • Whether pregnant or not. Any reactions to contrast media.
    • Whether the patient has any infective issues, for example, Clostridium difficile or methicillin-resistant Staphylococcus aureus (MRSA) positive.
    • A specific question to be answered. Imagine being the radiologist reporting these scans without the benefit of patient history, examination or indeed notes. This is why writing a misleading request card to get a scan done more urgently is dangerous and completely unacceptable.
    • Clinical features (not just suspected diagnosis).
    • How the results will affect the management plan.
    • Any factors which may complicate the procedure (e.g. diabetes, epilepsy).

  3. Ask the radiographers about how to prepare patients for investigations if you are unsure, such as barium enemas. Often, the radiographer will liaise directly with the ward nurse, in which case you don’t have to do anything except prescribe preparations, such as enemas.

Minimizing radiation

Table 14.1 Radiation doses of radiological investigations.

Investigation Number of CXR equivalents (1 CXR = 0.02 mSv) Equivalent background radiation dose
Abdomen X-ray 35 105 days
Chest X-ray 1 3 days
CT abdomen 500 4.1 years
CT chest 400 3.3 years
CT head 100 300 days
MRI brain/abdomen/limbs 0 0
IVU 120 1 year
Barium swallow 75 225 days
Barium enema 360 3 years
Leg arteriogram 100 300 days
Thyroid isotope scan 50 150 days
PET scan 250 2 years

Lee RKL et al. (2012) Knowledge of radiation exposure in common radiological investigations: a comparison between radiologists and non-radiologists. Emergency Medical Journal 29:306–308. RCR Working Party (1998) Making the Best Use of a Department of Clinical Radiology: Guidelines for Doctors, 4th ed. The Royal College of Radiologists, London.

Common concerns about X-rays

Patients are usually concerned about being X-rayed. Therefore, wherever possible, tell the patient:

  1. What is about to happen to them
  2. Why they are having this done
  3. Duration of imaging
  4. Whether or not they will be sedated or have a general anaesthetic
  5. If they might experience any discomfort
  6. What to do if they have pain or other symptoms after the procedure
  7. When they can expect to receive the result


  • Referring clinicians (i.e. you) are responsible for informing the radiologist if a patient is pregnant. It is negligent not to do this. Where possible tell the radiologist and radiographer yourself.
  • If you need to X-ray a pregnant patient, ask the radiologist for advice; they may suggest an alternative.
  • Pregnant patients will be particularly concerned about the dose of radiation exposure so it is important to know the differences between investigations, alternative tests and the risks and benefits of proceeding with a test.

Plain films

Chest X-rays

CXRs use ionizing radiation in the form of X-rays to generate an image. It is able to provide views of the bones, lungs, heart, great vessels and trachea. As a result, they are one of the most commonly performed investigations when a patient is admitted to hospital (Fig. 14.1). A CXR can be used to diagnose a number of conditions including:

  1. Pneumonia
  2. Pulmonary oedema
  3. TB
  4. Pulmonary fibrosis
  5. Lung cancer
  6. Pleural effusions
  7. Sarcoidosis
  8. Pneumothorax
  9. Rib fractures
  10. Lung collapse

Figure 14.1  Anatomy of a chest X-ray.

Checking the CXR: The bare bones

  1. Patient’s name, the date of the film and whether the film is anterior–posterior projection or posterior–anterior projection.
  2. Trace the diaphragm and the lateral outline of the rib cage (look for pleural effusions, air under the diaphragm, raised hemi-diaphragm, pneumothorax).
  3. Check the size and shape of the heart (look for enlarged heart, atrial shadows, calcified valve rings). Also look ‘through’ the heart for lesions that it partially obscures such as hiatus hernia or a cancer.
  4. Check the position of trachea and heart (look for displacement or if the film is rotated).
  5. Look at the mediastinum (look for air, widened mediastinum, lymphadenopathy).
  6. Examine the hilar shadows (look for enlarged pulmonary arteries and veins).
  7. Examine the lungs (look for opacities – consolidation, fluid or nodules). For interstitial oedema, look for straight lines (normal interstitial shadows are ‘never’ straight).
  8. Check the bony structures (ribs, clavicles, spine) and the soft tissues (fractures, densities or lucencies, air in the tissues – surgical emphysema after trauma).

Abdominal films

An abdominal film can be used to diagnose the following conditions:

  1. Obstruction
  2. Constipation
  3. Volvulus
  4. Pneumoperitoneum
  5. Renal calculi (although not the best imaging modality for this pathology)
  6. Toxic megacolon
  7. Ulcerative colitis flare
  8. Abdominal aortic aneurysms, particularly if calcified

Checking an abdominal plain film

  1. Patient’s name and date of the film; whether erect, supine or lateral decubitus.
  2. Gas pattern and intestinal diameter (a small bowel >2.5 cm and colon >6 cm indicate obstruction).
  3. Look for ascites and soft tissue masses.
  4. Identify the liver and spleen.
  5. Check the borders of the kidneys, bladder and psoas muscles if possible.
  6. Calculi (gall stones, renal and pancreatic calculi, aortic calcification).
  7. Sub-diaphragmatic gas (or clear outline of organ) indicates perforation or recent surgery. (Note: sub-diaphragmatic gas is best seen on an erect CXR. The absence of free gas under the diaphragm does not rule out perforation.) A decubitus film is an alternative if the patient is too ill to sit up.


Sep 27, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on RADIOLOGY

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