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Unaltered fat is a permanent component of the abdominal cavity, even hietologia slim individuals. Visceral adiposity is one of the important factors contributing to diabetes, cardiovascular diseases and certain neoplasms. Moreover, the adipose tissue is an important endocrine and immune organ of complex function both when normal and pathological.
Its role in plastic surgery, reconstruction and transplantology is a separate issue. The adipose tissue has recently drawn the attention of research institutes owing to being a rich source of stem cells. This review, however, does not include these issues. The identification of fat is relatively easy using computed tomography and magnetic resonance imaging.
: Wojciech Sawicki: Books
It can be hisgologia difficult in an ultrasound examination for several reasons. The aim of this paper is to present various problems associated with US imaging of unaltered intra-abdominal fat located beyond organs. Based on the literature and experience, it has been demonstrated that the adipose tissue in the abdominal cavity has variable echogenicity, which primarily depends on the amount of extracellular fluid and histologix number of connective tissue septa, i.
The normal adipose tissue presents itself on a broad gray scale: The features that facilitate proper identification of this tissue are: The accumulation of fat tissue in the abdominal cavity can be generalized, regional or focal. The identification of the adipose tissue in the abdominal cavity using ultrasonography is not always easy. When in doubt, the diagnostic process should be extended to include computed sawickk or hisologia resonance imaging, or sometimes biopsy preferably the core-needle one.
Gas, bones and fat are known obstacles for ultrasound wave propagation. It is commonly believed that a greater amount of fat in a given organ increases its echogenicity. Fatty liver or pancreas is a typical example 1 — 4.
The entirely different image of fat can be seen in sonomammography, where it is characterized by low echogenicity 56. The adipose tissue xawicki in the abdominal cavity can have various acoustic patterns, and hixtologia knowledge of them should prevent diagnostic pitfalls. The aim of the paper is to present various problems associated with US imaging of unaltered intra-abdominal fat located beyond organs. The adipose tissue is not only a coat-like structure that protects against heat loss or 20088 energy, but is also an important endocrine and immune organ, the function of which is complex both in normal and pathological conditions.
Moreover, it draws the attention of research institutes owing to being a rich source of stem cells 78. The common methods for the identification of the adipose tissue are computed tomography CT and magnetic resonance imaging MRI.
However, even the most modern versions of computed tomography are unable to distinguish between two types of fat in the human body, i. Such discrimination is possible with the use of a special technique of magnetic resonance imaging and positron emission tomography 9 The brown adipose tissue is found in lower amounts and its stores decrease with age.
It is mainly localized in the neck, in the subcutaneous tissue between the scapulae, in the mediastinum, axillary fossae, deep in the retroperitoneal space and even between the paraspinal muscles 911 Ultrasound imaging does not enable these two types hitsologia be distinguished. Irrespective of the type, the adipose tissue can be acoustically manifested in various ways, which makes its certain identification difficult.
It was established very early that the varied acoustic profile of the adipose tissue mainly depends on two factors, namely the amount of histo,ogia and the number of connective tissue septa 13 The insolubility of fat in water is a commonly known fact. This way, fluid accumulated in spaces between adipocytes, together with the cells themselves, multiplies the number of areas that reflect and scatter ultrasonic waves.
As a result, it leads to the formation of an overwhelming noise that destroys the image of the examined structure. A typical example of such a phenomenon, which has not been reported so far, is a serious problem with ultrasound imaging in patients in a grave clinical condition with cardiovascular, renal or hepatic failure, or in acute pancreatitis.
In these cases, the transudate accumulates between subcutaneous fat lobules and generates noise that renders the imaging of the structures located deeper histtologia Fig.
Intra-abdominal fat. Part I. The images of the adipose tissue localized beyond organs
Numerous connective tissue septa that separate fat lobules cause slightly less troublesome acoustic effects — they increase the echogenicity of fat Fig. The proportion of these two elements, i. It must be assumed that the shades of the acoustic patterns of this tissue can have a very broad range in gray scale, i. The application of techniques that improve sonograms, i.
Other features of the normal adipose tissue are: However, the last feature is debatable since, on numerous occasions, we have observed posterior enhancement behind the extraperitoneal fat pad localized above the left liver hisrologia.
In these cases, a slightly hyperechoic focus can be seen in the liver and is sometimes misinterpreted as a focal lesion Fig. Another important feature of the adipose tissue in US is its elasticity evaluated in a simple test consisting in applying pressure with a transducer. In our non-published studies, we have found a marked relationship between the compressibility of fat and its echogenicity.
The lower the echogenicity, the greater the strain and vice versa: Moreover, the normal adipose tissue does not show any signs of vascularization in Doppler examinations of blood flow. Another feature that supposedly facilitates the assessment of the intra-abdominal fat is the symmetry of its distribution This is only relatively true since, due to considerable differences in the size between the liver and spleen, the left side holds considerably greater amounts of fat Fig.
One should remember, however, that the unaltered greater omentum is sometimes localized between the diaphragm and the right liver lobe, particularly in men Fig. Moreover, the extraperitoneal fat localized above the left liver lobe, which coats the round ligament of the liver on its way to the umbilicus, is characterized by constant asymmetrical deposition; it only slightly crosses the midline to the left Fig. Sometimes, the aforementioned fat pad can be erroneously interpreted as a subphrenic abscess when accompanied by acute clinical signs in the epigastric region.
This can be ruled out by observing a free visceral sliding movement induced by a deep inspiration against the immobile fat accumulation Moreover, individual predispositions to asymmetrical fat deposition, such as lipoatrophic-lipodystrophic syndrome, should be taken into account when discussing intra-abdominal fat distribution.
This issue is rarely discussed in the literature Examples of this condition include: A tumor-like fat accumulation in other areas of the abdominal cavity is, however, rarely encountered Fig. In such cases, a US examination itself does not enable the differentiation of focal lipomatosis from a high-grade liposarcoma. The diagnostic process should therefore include all other means available to establish a correct diagnosis.
Pelvic lipomatosis is also noteworthy. In this case, the deposited adipose tissue, frequently hyperechoic fat, can cause urological or intestinal problems by compressing organs localized in this area, e. Acute pancreatitis with a fluid collection C. Two views of the renal capsule with a low number of connective tissue septa arrows ; the echogenicity is similar to that of the renal parenchyma. Renal capsule in a different patient with numerous septa arrows that make this structure more echogenic than the renal parenchyma.
Above the fatty left liver lobe Lthere is an extraperitoneal fat pad of very low echogenicity which mimics a pathological fluid collection F. The same view shows the same fat pad F captured with a different technique of harmonic imaging; no signs of marked differences in echogenicity. An artefact that mimics a hyperechoic focus in the left liver lobe A by a biconvex fat pad F.
A year-old patient treated with Encorton because of rheumatoid arthritis. A year-old diabetic patient. A year-old patient with no injury. Above the spleen Sthe deposited fat mimics a hematoma. Above the right liver lobe Lthere is a slightly heterogeneous structure Owhich is the greater omentum. A year-old patient with left liver lobe agenesis. The fat pad is typically hypoechoic F. The site of the left liver lobe is occupied by the markedly hyperechoic greater omentum O.
A very slim year-old woman presents a fat pad in the right iliac fossa. A year-old man with normal weight. In the left hypochondriac region, there is a tumor-like fat accumulation F which should be differentiated from a highly mature liposarcoma. This fact is of particular significance in cancer patients in whom the appearance of any lesion in the tumor bed usually suggests a relapse.
This is well-illustrated by a hypertrophied fragment of the adipose capsule after nephrectomy Fig. To conclude this part, our observation concerning incompetent kidneys should be mentioned. Multiple patients with renal failure present a vaguely circumscribed hypoechoic area in the adipose capsule.
It is contiguous to the cortical layer and is not a fluid collection under the capsule Histologua. A hypertrophied fibrolipid mass in the site after a removed kidney in a cancer patient. The compression test shows the compressibility of the lesion. A different patient after right nephrectomy also presents hypertrophied adipose tissue F but with different echotexture compared with Fig.
A year-old doctor with kidney failure creatinine 1. US shows the kidneys of a normal size and normal thickness of the parenchyma. The only abnormality is decreased corticomedullary demarcation. The figure shows only the left kidney. An irregular hypoechoic area can be seen in the adipose capsule. The ability of ultrasonography to reflect a detailed structure of the adipose tissue compared with CT or MRI is a significant advantage of this modality.
Despite this, any doubts concerning the nature of a lesion detected by ultrasound must be resolved in CT or MRI, or sometimes even by a biopsy, preferably the core-needle one. Unaltered intra-abdominal fat is manifested by a broad echogenicity range, which makes the identification of its nature difficult. The signs that can aid the interpretation include: The deposited fat can present itself as diffuse, regional or tumor-like thickening.
National Center for Biotechnology InformationU. Journal List J Ultrason v. Histologgia online Sep