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Transrectal ultrasound (TRUS)

Alexey Portnov, medical expert
Last reviewed: 19.10.2021

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Transrectal ultrasound (TRUS) is now considered the main method of recognizing prostate diseases. Transrectal transducers operate at frequencies from 6 MHz and higher, which ensures high image quality and allows for detailed visualization of the structure of the prostate gland and surrounding organs and tissues. The transrectal sensor is compact, has a working length of 12-15 cm and a diameter of up to 1.5 cm.

According to various authors, TRUS provides more accurate and detailed information on the status of the prostate; visualization of the entire volume of the prostate and its capsules with good image quality, the best conditions for accurate measurement of its size, the possibility of conducting ultrasonic cystourethroscopy, which makes this method mandatory in the study of the prostate.

The only drawback of the technique is the restriction of its use in certain diseases of the rectum and after operations on the perineum.

Transrectal transducers are divided into three types: working in the same plane; biplane, having two transducers (allowing to obtain an image of the prostate in the transverse and longitudinal planes); multidimensional - with the possibility of changing the scan plane by 180 °.

Indications for transrectal examination of the prostate

Clinicians identify the following indications for TRUS:

increased level of prostatic specific antigen (PSA), detection of prostate cancer;
Evaluation of the volume of brachytherapy before its onset;
direction of brachytherapy;
tumor, palpable formation, enlargement of the prostate gland in a physical examination (per rectum);
the location of prostate biopsy;
infertility, diagnosis of obstruction or cyst of spermatic cord;
hematospermia, detection of stones;
abscess, prostatitis, infectious disease;
difficulty in urinating (infravesical obstruction);
evaluation of the effectiveness of therapy.

Preparation for TRUS

Before the TRUS, the patient needs to explain the technique of the procedure, to warn about possible unpleasant sensations. It is recommended to do a cleansing enema for the patient before the test, however, it is not necessary for a diagnostic examination. In cases of planned transrectal biopsy, careful preparation of the rectum is necessary. An obligatory condition of transrectal ultrasound is sufficient filling of the bladder (150-200 cm ³ ), providing conditions for examination of its walls.

During the study the patient lies on the left side with the knees brought to the stomach. The depth of introduction of the sensor should not exceed 15-20 cm, which minimizes the risk of injury to the rectum. If necessary, it is possible to examine in a supine position on the right side or on the back with dilated knees. The latter position is used for prostate biopsy by perineal access.

How is TRUS performed?

Beginning of transrectal ultrasound is recommended with an image in the transverse plane. This allows you to quickly assess the general condition of the prostate gland. At the first stage, the sensor is inserted into the rectum to the level of the seminal vesicles and the bottom of the bladder. Moving the sensor back about 0.5 cm, the most complete cross section of the prostate gland is obtained. Changing the operating frequency of the sensor in the range from 6 to 12 MHz allows you to adjust the depth of penetration of ultrasonic waves and not only to obtain images of the smallest structures of the prostate gland, but also to assess the condition of surrounding organs and tissues.

As well as with TAUZI, at TRUS, the following quantitative and qualitative characteristics of the prostate gland are evaluated:

type of prostate growth;
degree of invasion of the prostate in the bladder;
the shape of the prostate;
symmetry of the prostate;
dimensions (width, thickness, length) and volume of the prostate;
the volume of the average share (if any);
volume of hyperplastic prostate tissue;
echostructure of the prostate.

It should be noted that for assessing the type of growth, shape, degree of invasion of the bladder and symmetry of the prostate, the TAUSI has an advantage over the TRUS due to the large angle of the prostate scan area and the ability to withdraw the entire prostate to the ultrasound monitor. This is especially important in the study of large prostates (more than 80 cm ³ ). Unlike TAUZI, the causes of insufficient visualization in the prostate TRUS are much less.

The expressed intravesical and mixed forms of growth with an average share (the intravesical part of a prostate is not defined).
Reduction of the bladder capacity of less than 60 ml in patients with intravesical and mixed forms of prostate growth with an average proportion.

Hyperplasic prostate gland on echograms is defined as a uniform formation, different in shape and size, but always with clear, even contours and a well-traced capsule. Hyperplasic prostate tissue can develop unevenly and create asymmetry in frontal echoscanization.

Assessing the echostructure of the hyperplastic prostate gland in TRUS, it should be noted the high information value of this method. The following changes in the echomodality of the prostate are revealed:

hyperechoic areas with a clear acoustic path (stones);
hyperechoic areas without an acoustic path (sections of sclerotically altered tissue);
anechogenous areas (cysts);
decrease in echomodality of the prostate,
increased prostate echolightness;
heterogeneity of the echostructure of the prostate due to a combination of high and low echomolarities;
visualization of adenomatous nodes and their clear differentiation with unchanged prostate tissue.

The difference in measuring the size and volume of the prostate between TAUSI and TRUS is small and averages 5.1%. It should be noted that the thickness of the prostate varies most, which is not always explained by the correct choice of the angle of transverse scanning of the prostate by the abdominal sensor (several oblique cuts are obtained, which leads to an increase in its diameter). However, there is a tendency to decrease the volume of the prostate, calculated with TRUSI in relation to TAUS. This is due to a better visualization of the capsule of the prostate and, accordingly, a more accurate definition of the points of its measurement.

It should be noted that when comparing the results of measurement of the prostate on different ultrasound devices, there was no significant difference. It averaged 0.32 ± 0.04 cm for width, 0.39 ± 0.07 cm for thickness and 0.45 ± 0.08 cm for prostate length. However, the sizes of the prostate of the same patient differed significantly from those made by different researchers. They averaged 0.68 ± 0.08 cm for width, 0.74 ± 0.12 cm for thickness and 0.69 ± 0.09 cm for the length of the prostate gland. Such results can be justified by the fact that each specialist in ultrasound diagnostics has his own preferences in choosing the measurement points and the scanning angle of the prostate gland, which is especially noticeable when measuring the thickness (anterior-posterior size).

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