Intra-abdominal adhesions in ultrasound. Part II: The morphology of changes.

Despite their frequent appearance, intra-abdominal adhesions are rarely the subject of clinical studies and academic discussions. For many years the operators have been trying to reduce such unfavourable consequences of interventions in the abdominal structures. The aim of this article is to present the possibilities of intra-abdominal adhesion diagnostics by means of ultrasound imaging based on authors' own experience and information included in pertinent literature. The anatomy and examination technique of the abdominal wall were discussed in Part I of the article. In order to evaluate intraperitoneal adhesions, one should use a convex transducer with the frequency of 3.5-6 MHz. The article provides numerous examples of US images presenting intra-abdominal adhesions, particularly those which appeared after surgical procedures. The significance of determining their localisation and extensiveness prior to a planned surgical treatment is emphasized. Four types of morphological changes in the ultrasound caused by intra-abdominal adhesions are distinguished and described: visceroperitoneal adhesions, intraperitoneal adhesions, adhesive obstructions as well as adhesions between the liver and abdominal wall with a special form of such changes, i.e. hepatic pseudotumour. Its ultrasound features are as follows:The lesion is localised below the scar in the abdominal wall after their incision.The lesion is localised in the abdominal part of the liver segments III, IV and V.With the US beam focus precisely set, the lack of fascia - peritoneum complex may be noticed. An uneven liver outline or its ventral displacement appears.A hepatic adhesion-related pseudotumour usually has indistinct margins, especially the posterior one, and, gradually, from top to bottom, loses its hypoechogenic nature.In a respiration test, this liver fragment does not present the sliding movement - a neoplastic tumour rarely shows such an effect. The immobility of the liver is a permanent symptom of subdiaphragmatic abscess which needs to be included in the differentiation process.In case of doubts, the suspicious liver area may be examined without the consideration of the scar in the abdominal wall. In the differentiation of visceroperitoneal adhesions, firstly, one needs to exclude the peritoneum infiltration in the course of inflammation and neoplastic spreading, which may be very difficult in patients who have undergone a surgery. Pseudomyxoma peritonei constitutes a source of errors much more rarely.

Despite their frequent appearance, intra-abdominal adhesions are rarely the subject of clinical studies and academic discussions. Such changes mainly result from inflammatory processes of the intestines as well as various surgeries and their complications. Acoording to Ivarsson et al.(, intra-abdominal adhesions should be considered frequent and serous postoperative complications, which significantly increase the health care institution expenses on treatment, especially in the case of patients with intestinal obstruction. For many years, the operators have been trying to reduce such unfavourable consequences of interventions in the abdominal structures by the intraoperative administration of factors which inhibit the inflammatory reaction and migration of peritoneal fibroblasts, e.g. special gels, aerosols, dextrans, bioresorbable membranes and others(. Nonetheless, the most widespread method is the performance of minimally invasive procedures, in particular laparoscopy.

The aim of this article is to present the possibilities of intraabdominal adhesion diagnostics by means of the ultrasound imaging (US) based on authors’ own experience and information included in pertinent literature.

According to the authors of this article, four types of morphological changes caused by intra-abdominal adhesions may be distinguished.

I. Visceroperitoneal adhesions

They constitute the most frequently recognized changes in ultrasound tests. Their detection is possible in one of the two ways:

A. Through the atrophy of the fascia – peritoneum complex in a given area (the complex was described in the Part I of this article). Instead, the area in question presents abnormal tissue of various acoustic character and possible vascularisation visible in Doppler tests which code blood flow. It usually manifests itself as planar adhesions between the parietal peritoneum and adjacent viscera. Such a presentation may be seen in figs. 1 and 2, where the adhesions form a hypoechogenic band under the abdominal wall, one and five months after laparotomy respectively. Older changes of this type usually become heterogeneous or hyperechogenic (fig. 3). A belt of adhesions between the abdominal wall and viscera is observed much more rarely (fig. 4). Increased adhesive reactions are manifested by massive tissue thickening under the abdominal wall (figs. 5 and 6). Sometimes scarring changes are simultaneously visible in the layers of the abdominal wall (fig. 7). It needs to be emphasised that adhesions cannot be diagnosed solely on the basis of the lack of the viscera – peritoneum complex. After surgical incisions of the abdominal wall or after traumas affecting this area, its appropriate image is never observed. The healing process of these structures leads to their fibroblastic conversion.

Fig. 1

The fragments of the fascia – peritoneum complex are replaced by planar adhesion of the abdominal wall with the omentum (arrows)

Fig. 2

An irregular hypoechogenic adhesion (arrow) immobilizes the small intestine (j) and the abdominal wall

Fig. 3

Divided sonogram. After appendectomy. On the left, the arrows point to a slightly echogenic adhesion fixing the ascending colon to the abdominal wall, which show clear atrophy. On the right, a normal structure of abdominal wall in the left iliac region is presented

Fig. 4

After the removal of the left ovarian cystoadenoma. The hypoechogenic adhesion band (arrows) immobilizes the uterine fundus (M) and the abdominal wall. On the right, despite maximum inhalation, the uterus remains in the same location with the adhesion showing an increased tension

Fig. 5

The two sections present massive adhesions under the abdominal wall (arrows) which fix the intestine (j)

Fig. 6

The adhesion in the hypogastrium (arrows) after a C-section prevented the gynecologists from removing a cystic lesion of the left ovary

Fig. 7

Divided sonogram. On the left, a normal structure of the abdominal wall in the right lumbar region; on the right, a visceroperitoneal adhesion immobilizing the intestine (j) and intensified scarring changes in the abdominal wall (arrows)

B. Through easy or deep respiration. In this test, the viscera are immobile in relation to the peritoneum or their slide size does not exceed 1 cm(. This symptom is easily noticed above the postoperative scar of the abdominal wall. The changes are presented in figs. 8 and 9.

Fig. 8

Massive adhesions of the abdominal wall with the viscera after appendectomy (arrows). Respiration test. A complete lack of visceral slide

Fig. 9

Respiration test. The visceroperitoneal adhesions immobilise the viscera completely

The visceroperitoneal adhesions are much more frequent than intraperitoneal ones. Therefore, in this case, ultrasound is more effective. Taking under consideration the two manners of the visceroperitoneal adhesion evaluation presented above as well as methods of testing which include nine segments of the abdominal wall, one may draw a detailed map of the localisation of changes. It is of crucial importance for the operator in his or her decisions concerning the collisionfree intervention in the abdomen(. In their study, using the visceral slide as a criterion on the basis of 110 subjects, Kolecki et al.( obtained high accuracy of the method, i.e. 91%, and individual parameters were as follows: sensitivity 90%, specificity 92%, positive predictive value 90%, negative predictive value 92%. Taking into account the localisation, the alternative to this method is only magnetic resonance imaging movie since its diagnostic accuracy is similar: sensitivity 87.5%, specificity 92.5%(. This method, however, is still not very popular and not easily accessible.

II. Intraperitoneal adhesions

To date, ultrasonographers have been discouraged from examining such adhesions since intestinal gases and fatty abdominal wall constituted an obstacle for ultrasounds(. In some cases the intraperitoneal adhesions are possible to visualise. However, it is not easy. The adhesion between loops of the small intestine with frequent wall infiltration attest to the presence of the intraperitoneal adhesions. The following techniques are also helpful: deep respiration test with the evaluation of the intestinal loop location when the patients change their positions as well as the attempt to move these loops by means of compressions applied by the transducer. The adhesions themselves are not usually visible. If adhesions are located deeply in the peritoneal cavity, their etiology is more frequently non-operative. Such consequences may result from a range of inflammations, mainly appendicitis, cholecystitis, diverticulitis, adnexitis (fig. 10) as well as blunt of pervasive abdominal traumas and radiotherapy. According to the material of the authors of this article, adhesions in the surroundings constituted a frequent complication of Crohn's disease (figs. 11–13). Sometimes the adhesive process encompasses the whole abdominal cavity immobilizing all viscera. It should be born in mind that intensified adhesive reactions in the area are caused by endometriosis and carcinoid through released serotonines – “sunburst” appearance (fig. 14 A and B)(. The presented images imply that in order to evaluate intraperitoneal adhesions, a convex transducer with the frequency of 3.5–6 MHz is more useful.

Fig. 10

The glued small intestinal loops (arrows) after right adnexitis

Fig. 11

Crohn's disease. The glued small intestinal loops (arrows) around the internal fistula

Fig. 13

Crohn's disease. The glued small intestinal loops (arrows) around the internal fistula

Fig. 14 A

A carcinoid of the iliac part of the distal intestine with the fibroblastic reaction (arrows)

Fig. 14 B

The same case. A clear fibroblastic reaction (arrow) is a cause of small intestinal obstruction

Crohn's disease. The divided sonogram shows a B-mode and CD ultrasound image of glued loops (white arrows) around the interloop fistula (black arrow)

III. Adhesive obstructions

It is almost exclusively related to the small intestine and constitutes the most serious complication of this pathology. In the Western countries, adhesions place themselves at the top of the list of the small bowel obstruction causes, ahead of hernias. In Poland the situation is inverse(. In our study, ultrasonography was marked by an acceptable accuracy in diagnosing intestinal obstruction (89.6%), as compared with conventional radiography (63.8%). Nevertheless, the adhesions, being the main reason of this condition, had not been visualised before(. Within the last several years, our experience broadened thanks to which, in 5 cases we managed to visualise the adhesions as the main reason for such a condition. Fig. 15 A and B as well as 16 A and B present such a clinical situation. It is worth mentioning that computer tomography, with high precision, enables to visualise the intra-abdominal adhesions which cause mechanical obstruction of the small intestine(.

Fig. 15 A

Adhesive obstruction after right hemicolectomy in a 65-year-old patient. The dilated loops of the small intestine (up to 52 mm)

Fig. 15 B

The same patient. The cause of the obstruction is the clearly turned adhesion (z) between the abdominal wall and the intestine, presented in two sections

Small intestine obstruction after the resection of fibroid uterus in a 54-year-old patient. The sonogram shows the lumen of the small intestine which is dilated to 45 mm and is filled with echogenic content

The same patient. In two sections, the sonogram shows a clearly turned adhesion (z) between the abdominal wall and the intestine

IV. Adhesions between the liver and abdominal wall

They constitute a consequence of all surgical procedures performed in the right hypochondriac and epigastric regions (after a classic cholecystectomy, partial resections of the liver and pancreas, gastrectomy etc.). The ultrasound beam undergoes scattering and refraction on its encounter with a scar. This may produce various acoustic effects in the superficial liver layers. Figs. 17–22 present various acoustic effects of hepatic-integumental adhesions. A hepatic, adhesion-related pseudotumor constitutes a very curious diagnostic problem. Its ultrasound features are as follows:

Fig. 17

On the right side of the divided sonogram, there are discreet planar adhesions of the left liver lobe with the abdominal wall (arrows) after gastrectomy. On the left, the normal presentation of the fascia – fat – peritoneum complex (arrows) above the right liver lobe

Fig. 22

The right liver lobe echostructure and its surface which is considerably deformed by irregular adhesions

The lesion is localized below the scar in the abdominal wall after their incision.

The lesion is localized in the abdominal part of the liver segments III, IV and V.

With the US beam focus precisely set, the lack of fascia – peritoneum complex may be noticed. Instead, an uneven liver outline or its ventral displacement appear, which will be more visible when a high-frequency transducer is used.

A hepatic adhesion-related pseudotumor usually has indistinct margins, especially the posterior one, and, gradually, from top to bottom, loses its hypoechogenic nature.

In a respiration test, this liver fragment does not present the sliding movement – a neoplastic tumor rarely shows such an effect. The immobility of the liver is a permanent symptom of subdiaphragmatic abscess, which needs to be included in the differentiation process.

In case of doubts, the suspicious liver area may be examined without the consideration of the scar in the abdominal wall.

Divided sonogram. On the right, planar adhesions of the abdominal wall, which are in atrophy, with the left liver lobe. On the left, the normal presentation of the fascia – peritoneum complex presented in lateral relation to the scar after the resection of the large intestine

A scar in the abdominal wall (arrow) after cholecystectomy causes the displacement of the liver and prevents the assessment of the hepatic parenchyma

In the two sections of the right hypochondriac region, the arrows indicate a scar which causes the displacement of the liver, mimicking the presence of a focal lesion in its parenchyma

A scar in the abdominal wall visibly shifts the liver and is the cause of the hypoechogenic areas (arrows)

In fig. 23, a complete obstruction is presented caused by the adhesion of the liver sliding movement. Such an effect is a frequent consequence of adhesions in this localisation and it results in decreasing respiratory deflections of the diaphragm.

Fig. 23

Visceral respiration test. An adhesion (arrows) completely hinders the liver slide

In the differentiation of visceroperitoneal adhesions, firstly, one needs to exclude the peritoneum infiltration in the course of inflammation and neoplastic spreading (fig. 24) which may be very difficult in patients who have undergone a surgery. Pseudomyxoma peritonei constitutes a source of errors much more rarely (fig. 25).

Fig. 24

The sonogram presents the thickening of the parietal peritoneum (arrows) as a manifestation of peritonitis carcinomatosa in the course of ovarian cancer spread

Fig. 25

The gelatinous masses of a pseudomyxoma in the peritoneal cavity provoke a caudal movement of the intestines (j)

Conclusion

Ultrasound examinations allow for a precise determination of the location of visceroperitoneal adhesions and, if imaging conditions are favorable, also the intraperitoneal ones. Thanks to this method, it is sometimes possible to diagnose adhesive obstruction of the small intestine. Due to scattering and refraction of the US beam, the adhesions between the liver and the abdominal wall may alter its surface and echostructure to such an extent that an image of a pseudotumor appears.