In a patient with urinary discomfort related to urinary disorders, the urologist must determine whether these symptoms are related to prostatic obstruction or not.
The ultrasound assessment takes place at several levels:
- Analysis of the repercussion of prostatic obstruction with the measurement of the post-voiding residue and the search for complications at the bladder level and in the upper urinary tract.
- Precise analysis of the prostatic volume on which therapeutic indications depend.
- Follow-up of prostatic obstruction, changes in the gland, result in micturition, and bladder emptying of treatment initiated.
The completion of the examination
This is an ultrasound examination performed by a qualified radiologist, specialist physician.
The urologist may also have an ultrasound in his consulting room, the ultrasound probe revealing a natural extension of the clinical examination.
In a homogeneous medium, the ultrasound propagates in a straight line, and when stopped by an obstacle, they return an echo. This is the principle of sonar used in submarines. The variety of echoes returned is a function of the density of the tissues through which the images are transmitted, and their analysis makes it possible to obtain, in real time, cross-sectional images in all the planes. These images allow the analysis of the contents of the anatomical regions explored.
The reflection wave is a function of the acoustic impedance specific to each tissue.
The signal is scanned on a gray scale with matrix reconstructions of a two-dimensional image.
The cutting plane is defined by the position of the probe on the patient.
It is not necessary to be fasting for this examination. On the other hand, it is advisable to present the full but not distended bladder in order to avoid post-void pseudo-residues.
There was no intravenous injection during the examination.
The latter comprises a first phase using a transparietal sector probe of 2 to 5 MHz. The patient is lying on his / her back on the examination table
The second phase, with the consent of the patient, is performed with an endo rectal probe with a frequency of 5 to 9 MHz, protected by a condom and lubricated. The patient is then usually lying on the side turning the back to the radiologist.
The patient then urinates to empty his bladder and a measure of the post-void residue is carried out with the surface probe.
The ideal if the equipment allows it is to carry out at the time of this urination a flow meter.
The organs monitored
Ultrasound is not only prostatic but renal, vesico-prostatic and post-voiding.
This complete examination of the deep and urinary genital tract in man allows the study:
- Kidneys: size, contours, analysis of the parenchyma and cavities It can allow to chance discovery a renal tumor that would have been misunderstood without this examination, or kidney stones. Renal ultrasound reveals the possible repercussions of prostate adenoma on the upper urinary tract if a dilation of the renal cavities is found, and then the symmetrical character of this distension.
- Bladder: capacity in a state of replication, thickness of the wall, measurement of residual post-voiding. The diagnosis of adenoma on the bladder is indicated by the presence of signs of control: thickening and irregularities of the bladder wall, presence of trabeculations with “cells and columns”, presence of diverticula of the vesical wall or calculations of Bladder, eventual presence of a bladder tumor of fortuitous discovery.
From the prostate and the seminal vesicles by the supra-pubic approach using the abdominal surface probe, followed by the endo-rectal study. It allows to evaluate the volume of the prostate, to analyze its contours, and to study the central zone of the prostate and the peripheral zone, noting for each one its echogenicity and looking for pathological heterogeneities or nodules Of benign adenomatous character, or inflammatory or malignant tumors. It also reveals the existence of calcifications in the prostatic parenchyma, often located at the junction between the central zone and the peripheral zone. It may recover fluidic cavities in the form of cysts or utricles, or with purulent contents in the case of prostatic abscesses.
Echography in the BPH balance sheet
In the context of the prostate adenoma, or benign prostatic hyperplasia (BPH), ultrasound allows us to study:
1. The characteristics of the prostate.
a. The volume of the prostate
It is estimated by the multiplication of the three largest dimensions of the prostate (maximum transverse diameter, anteroposterior and sagittal height) by 0.52. There may be errors especially in the measurement of the length in the sagittal plane of the prostate.
This formula results in a volume. The density of the prostatic tissue is assimilated to that of water, that is to say 1 to obtain an estimated weight in grams. It is therefore not a direct measure of the weight of the prostate as if it were placed on a scale and this estimate is subject to a certain margin of error.
The prostatic volume can also be estimated by planimetry with an automatic calculation software integrated into the ultrasound system, which generally gives an estimate of the higher prostatic volume of about 20%, more reliable in large prostatic volumes than that given by formula former.
The variability of the total prostate measurements by ultrasound can reach 30%.
When ultrasound scanning is used solely to determine prostatic volume, suprapubic ultrasound results equivalent to endo-rectal ultrasound.
The normal volume of the prostate is about 15 to 20 grams in adults. Prostatic volumes up to about 40 grams correspond to moderate volume adenoma. Between 40 and 70 or 80 grams, these hypertrophies are of average degree and above 80 grams, one speaks of important hypertrophies and large adenoma knowing that one can meet considerable hypertrophies, 300, 400 grams or more.
b. The morphological characteristics of prostate hyperplasia
The ultrasound allows to appreciate:
- The mode of development of the gland: hypertrophy involving only the two lateral lobes, or existence of a third intra-vesical developmental prostate lobe raising the bladder floor called a prostatic median lobe. Asymmetric hypertrophy of the lateral lobes of the prostate is not usual in the context of the benign pathology of the adenoma which usually leads to a symmetrical repercussion, and it may be for its own account an indication of prostate biopsy in search of a cancer.
- The homogeneity of the prostatic tissue. The adenoma develops at the expense of the central area of the prostate, in the area surrounding the urethral canal. Cancer develops more often in the peripheral zone and abnormalities in this area may lead to the formation of a rectal examination and / or biological abnormalities in the PSA (prostate specific antigen) Ultrasound-guided prostate biopsies. Biopsies are never performed at the same time as ultrasound which allows the morphological analysis of the gland. They are examined on the occasion of a second examination, after a certain delay in relation to this first ultrasound, of the indications for the indication of these biopsies given by the urologist who reviews his patient with the result of the ultrasound, The acceptance of the patient and a preparation, in particular an antibiotic.
2. The impact of prostate adenoma:
a. On the lower urinary tract, mainly on the bladder
When it presents signs of struggle: thickening of the wall, trabecular ducts, columns, diverticula of wrestling, calculations of bladder whose formation is related to the stasis of the urine linked to a bad emptying of the bladder reservoir, existence of a residue post Greater than 100 or 150 ml. The importance of this residue may also be subject to variations in the same patient and in case of significant residue, its reality must be asserted by several measures; In particular, the bladder replication required by standard prostate ultrasound can constitute a discomfort to urination if the patient presents a bladder that is abnormally distended by the usual conditions of its urination. Under these conditions, the residue may be artificially increased and a new study, under normal and more physiological bladder rejection conditions, may invalidate the results of the first evaluation.
b. On the upper urinary tract
Lack of resonance when kidney cavities are not dilated. Under these conditions, the existence of a biological kidney failure translated by an elevation of the plasma creatinine level in a patient is not related to a prostate adenoma and leads to seek the opinion of a nephrologist.
However, in the same circumstances, if there is bladder retention and dilation of the renal cavities, the responsibility for this renal insufficiency is related to the adenoma of the prostate and the operative indication is then formal. Renal dilatation in relation to BPH is usually symmetrical; A frank asymmetry must attract attention and make seek the existence especially of prostate cancer.
Special aspects of the prostate study
Two particular aspects deserve to be developed.
1. The prostatic median lobe
This is a third intraocesical developmental lobe. It is best seen by supra-pubic ultrasound where this median lobe appears as an “enlarged sugar” hypertrophy raising the bladder floor.
At present, the protrusion index (PPI), corresponding to the measurement of this protrusion in bladder light, is being insisted.
Less than 5 mm. This PPI is grade 1, moderate.
Beyond one centimeter, PPI is grade 3, correlated with significant clinical urinary discomfort and a frequency of absence of recurrence of urination by natural pathways after complete bladder retention. It is an element supporting a surgical indication.
Grade 2 between 5 and 10 mm. Of IPP is intermediate.
The dysectasizing character of these prostatic median lobes, ie the importance of the discomfort they cause for urination and their pejorative impact on the urinary tract and the risk of degradation to which they expose it, is well known. They come to apply on the bladder neck at the moment of urination making clamshell on it.
They constitute a frequent surgical indication as medical treatment often has little effect on their development. A very important repercussion can exist even for medial lobes seemingly little hypertrophied, because of the central position in the level of the cervical urethral channel of these median lobes which quickly lead to mechanical compression and obstruction of the bladder neck. Because of bladder uplift and trigonal stretching, a portion of the bladder with particularly rich innervation, they are also the cause of an irritative and inflammatory symptomatology often causing very important genes For patients.
2. Prostate adenoma already performed:
A good result after prostate adenoma surgery whatever it is will be a well-hollow prostate and reduced to its peripheral shell with a prostatic box corresponding to the enucleation of the broad and regular adenoma. These morphological aspects of the prostate are associated with an absence of repercussions on the upper urinary tract, that is to say the disappearance of a dilation of the renal cavities if it existed, correlated with the disappearance of a biological renal insufficiency or its regression Important if it also existed before the intervention. The good result also results in the disappearance of a bladder retention if it existed in preoperative and the observation of a bladder emptying complete or nevertheless acceptable as a function of the contractility capacities that the bladder fiber has retained or recovered.
Ultrasound can therefore assess the causes of surgery failure and in particular the regrowths or remnants of prostatic tissues which may be at the origin of the persistence or the resumption of the discomfort of the patient and which may correspond to an iterative surgical indication .
It may also be useful for long-term follow-up after treatment with an initially satisfactory result, in particular to check the absence of development of a cancer on the prostate shell.
The indications of the ultrasound in the balance of the adenoma of the prostate
An ultrasound of the genital or urinary tract is not routinely performed as part of the BPH balance. This commonly performed assessment in a man in his fifties or more is based on the realization of a rectal examination and the blood test of the prostate specific antigen, PSA, usually supplemented by the study of other biological parameters And in particular renal function by the serum creatinine dosage.
Ultrasonography is indicated when there are voiding disorders, and / or clinical examination abnormalities, and / or biological abnormalities in particular of PSA.
Ultrasound is an excellent exam for understanding the overall condition of the human urinary and genital tract.
It is not invasive or even painful and therefore absolutely safe.
It is also not expensive and does not require equipment of an extremely high cost to be realized.
It is reproducible and it is an excellent examination to follow the evolution of a treated BPH, especially when this surveillance is carried out by the same radiologist. Ultrasound is indeed a highly dependent operator and is probably one of its main limitations.
It can by itself carry out the pre-therapeutic imaging assessment of a BPH, and in other circumstances it may lead to the realization of other complementary explorations.
Other explorations indicated on a case-by-case basis in addition to ultrasound
1. Flow measurement
It also allows a good appreciation of the impact of the adenoma of the prostate by informing about the quality of the urination, which does not do the ultrasound which gives only anatomical and morphological information. It is useful to couple it with ultrasound.
This flowmeter gives a visual result with the production of a curve reflecting the characteristics of urination.
Four parameters are particularly studied: the maximum rate of micturition in milliliters per second, the average flow rate of urination, the voiding volume and the duration of this voiding.
To be interpretable, the flowmeter must have a volume of at least 150 ml.
A bell-shaped curve reflects the absence of discomfort when urinating, whereas a flattened curve indicates a difficult urination because slow, dysuric and ultimately a pathological repercussion of BPH.
This flowmeter is also subject to variations in the same patient, especially in relation to the importance of bladder replication and it may be useful to repeat it.
2. Urethro retrograde cystography and micturition
It is an examination of imaging which makes it possible to study the lower urinary tract and in particular the cervico urethral channel. It is particularly useful when there is suspicion of a narrowing of the associated urethra or in case of regrowth or adenomatous residue in the prostatic chamber after failure of a surgical treatment.
3. Urethral bladder fibroscopy
It is an endoscopy of the lower urinary tract. The urologist performs local contact anesthesia by introducing a xylocaine gel into the urethra, allowing the urethra to be studied to eliminate a narrowing and to appreciate the hypertrophy of the prostatic lobes, the vesical neck to appreciate Stenosis, hypertrophy of the posterior lip or the existence of a median lobe, and the bladder to assess the existence of signs of wrestling, calculations, bladder tumor, especially in case of hematuria, Location of ureteral orifices.
4. The pelvic abdomino scanner
When ultrasound has unintentionally detected a tumor, bladder or kidney.
5. Multiparametric prostate MRI
When a cancer is suspected. Ultrasound makes it possible to suspect cancer when it describes rounded nodular images with contours more or less rounded, hypoechoic or, more rarely, heterogeneous. They are mostly located in the peripheral area of the prostate. Less than 30% of the hypoechoic images correspond to a real cancer. To increase the sensitivity of the results, echo-Doppler vascularization studies are indicated because the cancers are rather hyper vascularized. Ultrasound is a simple examination, but half of the anomalies detected are harmless and half of the cancers remain inapparent. Its specificity is close to that of MRI (90%) but its sensitivity is twice as low (40% vs. 80%). The coupling of ultrasound and MRI data by image fusion makes it possible to improve the detection of cancer areas to guide the realization of targeted ultrasound-guided prostate biopsies.
6. Ultrasound with Contrast Injection
It is not common practice. It is indicated especially in case of suspicion of prostate cancer and doubts after the realization of the MRI.
7. Prostate biopsies with ultrasound
In case of sufficiently argued suspicion of prostate cancer and it has been seen that the best mode of their current realization is the targeted biopsy after image fusion.
Some bibliographic elements
Ultrasound in the BPH balance (French)
Prostatic and echo-Doppler ultrasonography(French)