By Dr Sabujan Sainudeen, MD (Consultant Radiologist)
The ultrasound scan is one of the most widely used and most valuable diagnostic tools in modern medicine. It   came into medical practice more than 50 years ago and is now an essential facility in today medical practice. Ultrasound equipment uses high frequency sound waves which are transmitted to body parts and its reflections are reproduced as images. It is harmless, with no risk of radiation; it is not painful and has no after effects. It is relatively cheap, widely available, mobile and extremely patient friendly. Unlike most imaging tools, such as computed tomography (CT) and MRI scans the images are real time and can show structures and the movement of organs such as heart and blood vessels. The most popular use of ultrasound is in pregnant patients, where most other techniques are not so valuable and many are harmful to the baby.
Ultrasound scan in pregnancy

Ultrasound has become essential equipment in any maternal care centre. No other technique can see the baby, its movements and give information about the wellness of baby. All pregnant women are advised to do an ultrasound examination at least three times during pregnancy.

The first scan is recommended as early as possible when pregnancy is confirmed. Ideally it should be done at 6-8weeks after the last menses. This will help to confirm pregnancy, see whether the baby is developing normally and is in the proper place within the uterus. It is not so rare to have a pregnancy develop in abnormal positions as in the uterine tube, which may invariably result in abortion, bleeding and even the death of the pregnant mother.

A second scan is recommended before 20 weeks of pregnancy to see that the baby is developing properly. It helps to rule out congenital anomalies of the foetus, and abnormalities of the placenta and uterus. It is at this time the sex of the baby can be determined.

The third ultrasound scan is recommended a few weeks before delivery (ideally 34-38 weeks) to see the growth and maturity of baby, its position in the uterus, position of the placenta, status of amniotic fluid, etc. This will help to identify high risk labour. The time and mode of  delivery can be properly planned.

All pregnant patients should understand that an ultrasound examination done by a qualified radiologist or gynaecologist is harmless to mother and baby and is the only way to see the baby in uterus. If any pregnant lady has bleeding, reduced foetal movement after 20 weeks or an accident, an emergency ultrasound scan is required if advised by a doctor. A complicating illness during pregnancy may be another reason for an ultrasound.
Role of ultrasound in diseases

Ultrasound is the safest and most suitable least invasive investigation to see organs in the abdomen, blood vessels, heart, and external organs like breast, thyroid and testes.
Who may need

an ultrasound

examination?
1.  Abdominal pain: It can detect diseases of the liver, gall bladder, pancreas, kidneys, uterus, ovaries, etc. Kidney stones and gall bladder stones are common causes of severe abdominal pain. Infections like appendicitis, abscesses and intestinal diseases can also be detected on ultrasound.
2.  Vaginal bleeding: Non-periodical vaginal bleeding is an indication for an ultrasound study to see disease of the uterus and ovaries. Prolonged monthly periods, severe pain, or excess bleeding may need ultrasound to rule out any significant disease.
3.  Blood in urine: indicates disease of the kidneys, ureters, urinary bladder, prostate or urethra. A common cause of blood in the urine is stone disease which is easily diagnosed by ultrasound.
4.  Infertility: is an indication for ultrasound in males and females.
5.  Any swelling in any superficial body part
6.  Swelling or disease of neck: Goitre (enlargement of thyroid) and cancers of thyroid are identified by ultrasound.
7.  Breast swelling: Both cancers and non-cancerous breast swellings are detected by ultrasound. It can be used as guidance for a biopsy.
8.  Any recent onset of pain or swelling of the scrotum or testes: This may suggest serious disease like torsion (in which the blood supply of the testes is lost which when treated early can reverse testes damage) or infections.
9.  Difficulty in urination, painful urination, retention, increased frequency may indicate disease of the kidneys, bladder or prostate. Prostate hypertrophy is a common cause of these symptoms in elderly males.
10.  Heart disease: A special ultrasound technique called an echocardiogram is used in detecting disease of the heart.
11.  Pain, swelling of the limbs and venous engorgement may suggest a vascular disease.
Your doctor may decide the need for an ultrasound based on his clinical findings. A radiologist, gynaecologist or a trained doctor in ultrasound are the persons qualified to perform an ultrasound.
Preparation for an ultrasound

A usual abdominal ultrasound examination should preferably be done after fasting (overnight) to enhance the visibility of organs like the gall bladder, pancreas, and bowel. The bladder should be full before doing an ultrasound in order to see the pelvic organs like the uterus and ovaries. A mother in late pregnancy need not have to hold urine. Areas like the heart, blood vessels or any external organs may not need fasting or a full bladder. Bringing the old reports, any other investigation reports and discussing the relevant problems of the patient with the radiologist is mandatory for a good ultrasound study.

Safety, limitations

of ultrasound

Ultrasound has been widely used in medicine for the last 50 years. Though prolonged high intensity sound waves can produce certain physical effects like heating of the tissues in experimental animals, no such effects or complications have been noted in humans after the usual diagnostic ultrasound examination. In the last 30 years alone more than 50 million women have been screened by ultrasound during pregnancy and no equivocal adverse effects have been reported either in the developing foetus or mother, even on a long term follow-up.

Ultrasound may not be equally informative in all patients. More experienced radiologists give a consistently reliable report. The absence of fasting, inadequate bladder fullness, obese patients and non-co-operative patients may yield less reliable reports. It is to be remembered that ultrasound is a cheap, safe, often an early investigation; hence review and other diagnostic tests may be needed in some patients before starting proper treatment.
Conclusion

Ultrasound is a commonly performed, highly useful and safe radiological investigation. It is of great value in detecting the wellness of a foetus and mother. For many areas like abdomen it is the most important investigation which helps to identify the exact disease.

It can be used for specific guidance in biopsies, therapeutic aspirations and surgeries. If your doctor asks for an ultrasound, make sure that all relevant reports and details are taken along with you so you have adequate preparation for your examination.