Applications of intraoperative ultrasound in the treatment of complicated cases of acute and chronic pancreatitis and pancreatic cancer - own experience.

Both acute and chronic inflammation of the pancreas often lead to complications that nowadays can be resolved using endoscopic and surgical procedures. In many cases, intraoperative ultrasound examination (IOUS) enables correct assessment of the extent of the lesion, and allows for safe surgery, while also shortening its length. AIM OF THE RESEARCH: At the authors' clinic, intraoperative ultrasound is performed in daily practice. In this paper, we try to share our experiences in the application of this particular imaging technique. RESEARCH SAMPLE AND
METHODOLOGY: Intraoperative examination conducted by a surgeon who has assessed the patient prior to surgery, which enabled the surgeon to verify the initial diagnosis. The material presented in this paper includes 145 IOUS procedures performed during laparotomy due to lesions of the pancreas, 57 of which were carried out in cases of inflammatory process. RESULTS AND
CONCLUSIONS: IOUS is a reliable examination tool in the evaluation of acute inflammatory lesions in the pancreas, especially during the surgery of chronic, symptomatic inflammation of the organ. The procedure allows for a correct determination of the necessary scope of the planned surgery. The examination allows for the differentiation between cystic lesions and tumors of cystic nature, dictates the correct strategy for draining, as well as validates the indications for the lesion's surgical removal. IOUS also allows the estimation of place and scope of drainage procedures in cases of overpressure in the pancreatic ducts caused by calcification of the parenchyma or choledocholitiasis in chronic pancreatitis. In pancreatic cancer, IOUS provides a verification of the local extent of tumor-like lesions, allowing for the assessment of pancreatic and lymph nodes metastasis, and indicating the presence of distant and local metastases, including the liver. IOUS significantly improves the effectiveness of intraoperative BAC aspiration or drainage of fluid reservoirs.

Ultrasonography is the primary method in diagnostic imaging of the abdomen. Currently, due to the broader scope of technical capabilities, ultrasound examination may in many cases substitute a whole range of classical X-ray procedures, such as computed tomography (CT), vascular examination, or even magnetic resonance imaging (MRI)(. Ultrasonography is the only recognized noninvasive, and thus safe, imaging method.

Introduced in the 1960s, intraoperative ultrasonography (IOUS) was initially used in diagnostics of the abdomen, and the assessment of cholelithiasis and biliary disorders(. Owing to considerable developments, mainly in terms of technology, in the 1980s and after the introduction of B-scan presentation in ultrasonography, Lane and Glazer have described IOUS in “The Lancet”, referring to the technique as a useful method in examining pathological lesions of the pancreas(. The new generation of ultrasound devices with multi-purpose scanner heads and software which allows for accurate imaging of the scanned organ made ultrasonography something more than a diagnostic tool. It has led to a significant development of interventional ultrasonography, including laparoscopic ultrasonography (LUS)(.

Intraoperative ultrasonography is increasingly being used during pancreas surgery – mainly in cases of tumor-like lesions and cancers, but also in acute and chronic pancreatitis surgery(. Its fundamental task is to visualize lesions, determine their nature and extent, and provide material for histopathological examination during surgery. IOUS enables the differentiation between cystic, litho-cystic, and tumor changes in the pancreas itself and its vicinity(. An important factor is the assessment of secondary changes arising in the course of both the inflammation of the pancreas, and the expansion of pancreatic cancer with lymph node involvement and the escalation of tumor metastasis. The correct assessment of anatomical structures during surgery and the operating field after the completion of treatment, in combination with ultrasound, allow for a precise choice of the aggressiveness of treatment.

IOUS of the pancreas is best performed using high-frequency scanner heads, mainly in the frequency range of 7.5–10 MHz(. The shape and size of the heads are matched to the ability to assess the organ in two dimensions – longitudinal and transverse. Currently, the most commonly used shaped for scanner heads are “T” and “I”; these are typically Convex array heads, with sectorial and linear designs being less popular. The equipment must be easy to sterilize and convenient to use.

A very important element of the examination is the direct application of the scanner to the pancreas, which allows for correct imaging and detection of even small details in the organ's structure and potential lesions(. The pancreas should be carefully isolated and released from adhesions typically surrounding the organ in inflammatory processes, after this is done, the lesser sac needs to be open, which – in such cases – may often prove to be difficult. In cases where the specialist cannot surgically access the pancreas, it is possible to perform ultrasound scan of the organ through the left lobe of the liver, or the acoustic window formed by pressing the stomach wall(. In such conditions, in order to obtain a better image of the head of the pancreas and the surrounding structures, a useful approach is to place the scanner over the duodenum, even from the side, and to place it towards the portal vein. When assessing the head of the pancreas, one should also concurrently pay attention to such anatomical structures as the uncipate process, portal vein, the portal-mesenteric confluence, and the superior mesenteric artery. It is also important to obtain images of the section of the hepatoduodenal ligament – the common bile duct and vascular structures – and to examine the gallbladder. Next, distal pancreas should also be examined, together with the adjacent large arteries, splenic vessels and the spleen cavity(.

A correctly developed pancreas is divided into lobules. Parenchymal echogenicity is judged as being slightly greater in relation to the liver tissue. Echogenicity depends on the patient's age. In younger patients it may be slightly reduced, while in elderly it may be increased, which is mainly related to the content of the fibrous and fatty elements(. Increased echogenicity of the pancreas is a characteristic symptom of chronic inflammation, in the course of which the amount of fibrous elements and calcification increases, with a reduction of the organ's normal parenchyma(. Abundant adipose tissue surrounding the retroperitoneum and its infiltration of the pancreas in some patients may negatively affect the possibility of imagining the organ's edges. In such cases, it might be beneficial to determine the position of the adjacent vascular structures extending along the pancreas and crossing it(. An important element of the examination is the evaluation of the entire pancreas by applying the scanner to multiple locations, and the use of Doppler scanning and color imaging(.

This paper attempts to assess the suitability of IOUS and to determine the indications for the use of this method in the treatment of pancreatic lesions, mainly inflammatory complications, based on our own experience and the literature cited.

Research sample and methodology

The II Department of General and Gastrointestinal Surgery and Surgical Oncology of the Alimentary Tract has been performing ultrasound examinations since 1996. During this period, approximately 500 such procedures have been carried out, mainly necessitated by the various diseases of the liver and the pancreas. Since 2007, IOUS examination have been performed using the new BK Medical. Pro Focus system, and the 5-12 MHz linear array probe with oblong “I” shape, adapted for intraoperative biopsy and ablation. Previously, the examination was performer using a 12 MHz linear probe and a Hitachi EUB 410 12 ultrasound. In the last 10 years, over 280 procedures of intraoperative ultrasonography were performed, including 145 cases of laparotomy due to various pancreatic diseases. In this group of patients, percutaneous ultrasound, including Doppler, was used prior to surgery, with multislice CT, 33 – MRI or PET performer in the case of 113 patients. In patients with underlying disease of the pancreas, in most cases the reason for UOUS examination were nodular changes, both already confirmed by previous imaging and fine needle aspiration biopsy targeting (BACC) as cancerous, with and without an explicit result with regard to the nature of the tumor or inflammation, i.e. cases classified for differential diagnosis. The procedure was performed on 88 patients with tumors of the pancreas, including 41 with confirmed (through BACC) or suspected cancer of malignant transformation. The remaining group of patients required intraoperative verification of pancreatic tumor. In 57 patients IOUS was performed due to other, non-oncological diseases of that organ – mainly chronic pancreatitis – in order to verify the changes occurring in the enlarged pancreatic duct, identifying plaques and cysts. Less often, the examination was carried with the aim of providing intraoperative assessment of the changes in the course of acute pancreatitis, mainly to provide images of the abscesses and fluid reservoirs. Table 1 presents details on the patients examined.

Tab. 1

IOUS examination in patients operated due to lesions of the pancreas (years 2004–2014)

IOUS in patients operated due to lesions of the pancreas	145
Patients with confirmed pancreatic cancer	41
Differential diagnosis of tumors	47
Non-cancerous pancreatic tumors	57

Before each examination, an intraoperative probe (BK Pro Focus) was sterilized using appropriate antiseptic agents. Over the last 5 years, disposable covers – also used in laparoscopy – which mask the entire section of the cable were used. For over a year now, special disposable covers for ultrasound heads are also in use. Apart from not requiring prior sterilization, covers of this type protect the front of the scanner head, and are filled with gel. During the examination, the entire pancreas was evaluated, starting from head imaging, through the duodenum, and the direct application of the probe to the organ, after the incision of lesser sac and the release of all adhesions, starting from the stomach curvature and proceeding through to the root of the transverse colon mesentery. This was followed by the examination of the body of the organ's, the tail of the pancreas, and the spleen cavity. Attention was paid to the lobular parenchyma construction, its dimensions, and adjacent vessels; this included flow evaluation by Doppler scanning. Arteries and veins were scanned, both using color and power Doppler, and – in some cases – pulsed Doppler as well. The assessment included any abnormalities in the pancreas itself, lesions present in its surroundings, and vascular infiltrations. In cases of neoplastic lesions, lymphatic involvement was evaluated, including the assessment of potential metastases, mainly in the liver and subsequent lymph nodes. In cases where the surgery was performed due to causes other than cancer, examination was conducted for the extent and type of secondary degenerative lesions, and the changes in the organ's structure. The size, location, and number of fluid reservoirs was determined, as well as the gastrointestinal tract and other nearby organs and vessels of the upper section of the abdominal cavity.

In differential diagnostics, in cases of suspected malignant changes of hard-to-determine nature, IOUS was accompanied by biopsy using fine- or – more often – core needle. For a long time, the authors have been using the Sonocan (B Braun), which provides cylindrical tissue samples. An important aid in biopsy is the special needle holder which allows sampling with one hand. The setup is equipped with a 10 mm aspiration syringe and needles with a diameter of 7 to 12 mm. In the case of changes which are adjacent to the duodenum, it is possible to use needles of larger diameter, including sets for biopsy of cylindrical tissue samples (12–16 mm “tru-cut” needles). In such cases, the surgeon always waited for the result delivered by a pathologist directly to the operating room.

Results

In the last 10 years, IOUS examination was carried out in a group of 145 patients operated for pancreatic diseases identified in previous imaging and laboratory tests. Among these, in 41 cases the presence of a malignancy was confirmed prior to surgery, both in cytology, in fine-needle biopsy, and in number of imaging tests, defining the nature of malignancy using the markers CA 19-9, and – less frequently – CA 125 or CEA. In these cases, the aim of IOUS was to determine the severity of the malignancy and the feasibility of safe resection, or deciding on a palliative bypass. In another group of 47 patients who underwent laparotomy without a definitive diagnosis, IOUS examination was conducted in order to perform a differential diagnosis of nodular changes.

Table 2 presents the results of the study. The largest group, containing 23 cases, was related to the confirmation of the presence of cancer, mainly by IOUS-guided biopsy with an immediate assessment provided by the pathologist, as well as the determination of the expansion of the tumor to the surrounding structures, and lymph node imaging, with the possibility to collect samples during intraoperative examination. Intraoperative biopsy was performed using tissue needles (“tru-cut”) of a larger diameter than needles used for cytological biopsy. In cases where the lesions occurred in the head of the pancreas, perforation was performed mostly via the duodenum, in order to prevent the formation of a fistula or bleeding.

Tab. 2

IOUS examination in patients undergoing laparotomy for a differential diagnosis (years 2004–2014)

The study group with pancreatic tumors of previously undetermined nature	47
Cystic tumors	7
Confirmation of pancreatic cancer	23
Benign tumors	11
Cases without final confirmation using IOUS	6

IOUS examination confirmed the presence of seven lithium-cystic changes with the characteristics of cystic tumors of the pancreas. In these patients, BACC including aspiration was performed. Only in two patients content analysis (cytology, marker levels, mucus) gave a positive result; in the case of the remaining group the results were inconclusive. During surgery, in six of the cases, resection of the tumor was conducted, together with a corresponding portion of the pancreas. In one patient, the presence of malignant tumor infiltrating the surrounding area together with the liver was confirmed. This case was evaluated as inoperable. IOUS proved to be an effective method of intraoperative assessment with regard to determining the structure of liquid tumors, evaluating the boundary of the resection, and in the latter case – imaging of small metastases occurring in the liver.

Within the studied sample group of 145 patients who underwent intraoperative ultrasound examination, in 64 cases (41 confirmed preoperatively and 23 during surgery) the presence of pancreatic cancer has been confirmed. In these patients, the size of the tumor was analyzed, as well as its location in relation to the portal-mesenteric confluence and other venous and arterial vessels. Echogenicity and the structure of the tumor was carefully examined, together with the presence of enlarged regional and farther-located lymph nodes. The evaluation also included the width of the bile and Wirsung's duct. In all cases, the liver parenchyma was investigated in search of metastatic lesions.

In another 11 of the studied patients, a high probability of a non-cancerous tumor was determined. Ultrasound was used to scan small degenerative changes such as fibrosis, calcification, local and extended changes in the structure, which may correspond to the presence of a proinflammatory tumor, most often due to chronic pancreatitis, imitating metabolic changes typical of cancer. In all these cases, intraoperative biopsy, mainly tissue, confirmed the absence of cancer.

Among the remaining 57 patients IOUS was conducted during laparotomy, due to non-malignant changes in the pancreas. The largest group, consisting of 37 patients, included cases of chronic pancreatitis (CP). The course and the content of the pancreatic (Wirsung's) duct were evaluated during the removal of deposits as a preliminary procedure to Puestow anastomosis. In this group, there were also patients with choledocholitiasis combined with the presence of cysts or complicated cases of cystic lesions, qualified for surgical treatment of chronic pancreatitis. The remaining group of 16 patients underwent laparotomy as a part of the treatment for acute pancreatitis complications and proinflammatory lesions, mostly cystic and thus not qualified for endoscopic drainage. The aim of IOUS was to evaluate the intensity of tissue damage, the viability and location for drainage, including necroses and complicated cysts (determination of the anastomosis). In four cases, IOUS assessment was carried out for pancreatic cancer metastasis resulting from other cancerous changes in other organs, mainly in cancer of the stomach; the aim of the examination in such cases was to determine the scope of the planned operation. The last six studied cases included pronounced changes in the pancreas leading to its remodeling, including the infiltration of neighboring structures, without the possibility of a final verification using IOUS and a resection. These patients were evaluated during the period after laparotomy. Table 3 presents a complete IOUS evaluation of the sample group with lesions of the pancreas.

Tab. 3

Final verification of the group of patients operated due to lesions of the pancreas and examinied using IOUS (years 2007–2014)

IOUS examination of patients operated due to pancreatic diseases	145
Cystic tumors of the pancreas	7
Confirmation of pancreatic cancer	64
Benign tumors of the pancreas	11
Chronic pancreatitis	37
Complicated cases of acute pancreatitis	16
Other (pancreatic metastasis)	4
Unverified lensions	6

Discussion

The most important advantage of IOUS examination is the ability to apply the scanner head directly to the organ during abdominal surgery. The basic task of intraoperative ultrasonography is the staging of tumors, their operability, as well as identifying possible metastases(. IOUS is a useful method that helps solve problems in pancreatic surgery, during liver resection, and in a variety of therapeutic and diagnostic procedures in laparotomy(. Along with LUS, IOUS is now the most widely used method in intraoperative assessment of the liver, gallbladder, and the evaluation of pathology and the biliary tract construction(. Other purposes of IOUS is the determination of the nature of focal liver lesions and the extent of resection of liver cancer in terms of criteria, as well as the control of ablation procedures in the case of metastatic tumors. An important element of the examination is also evaluating the changes in the levels of the lymphatic system, both in the peritoneal and retroperitoneal cavity(.

Surgical procedures in pancreatic diseases are classified as the most difficult among all abdominal surgery. In many cases, intraoperative ultrasound is the major factor in the decision on the type of planned surgery, or even its cancelation. The use of IOUS may change the initial plans for surgery formulated with the use of preoperative imaging even in 38–49% of the cases(. IOUS is frequently used in the differentiation of pancreatic lesions, mainly pancreatic intraductal cancer and inflammatory lesions, or cystic and neuroendocrine tumors(. At present, the recommended method enabling the surgeon to identify these is to extend the examination using Doppler imaging, including color, power, and pulse Doppler, and even elastography based on tissue Doppler(. The examination concerns the evaluation of visceral vessels, both arteries and veins, and the determination of their path in relation to the changes under investigation. Color Doppler is useful in differentiating pancreatic pseudoaneurysms, which affects the course of surgical procedure(.

Despite ongoing developments in diagnostic imaging, it is still problematic to differentiate tumor-like lesions of the pancreas, and the changes which become clearly distinguishable only during laparotomy(. Intraoperative ultrasound is the method of choice in such situations, where no alternative diagnostic approaches are viable(. High resolution imaging used in intraoperative scanning probes allows for a correct visualization of almost the entire pancreas. IOUS enables the determination of the criteria indicating the presence and location of the tumor mass, its echostructure and homogeneity, the imaging of its borders, and the presence of changes occurring beyond the pancreas itself (lymph nodes, infiltration of adipose tissue, vascular walls of the gastrointestinal tract, metastases in other organs)(. The primary objective of the examination is to provide images of the tumors, distinguish it from other commonly-inflammatory or proinflammatory changes in solid tumors, and to classify it, leading to establishing a concrete treatment strategy(. In the last 10 years, the authors have used intraoperative study in 145 patients with pancreatic diseases. In most cases, the reasons for IOUS examination are nodular changes, with confirmed malignancy, and the lack of an explicit result with regard to the nature of the tumor or inflammation, or qualification for differential diagnosis (Fig. 1).

Fig. 1

IOUS. Tumor in the head of the pancreas with uneven surface and heterogeneous echostructure

In some of the cases, the examination procedure can be further improved by directly placing the scanner head to a particular segment of the pancreas. Conditions of the examination can be enhanced by cutting the gastro-colonic ligament and mobilizing the duodenum (Kocher's maneuver)( (Fig. 2).

Fig. 2

IOUS. Large pancreatic tumor (diameter: 5 cm). Direct application of the probe in the tumor after duodenum mobilization

In the case of lesions in the uncinate process, the alignment of the superior mesenteric artery and vein should be monitored (Fig. 3). If there is a change in the head of the pancreas, this requires a careful evaluation of the superior mesenteric vein, portal-mesenteric confluence, portal vein, gastro-duodenal vein and hepatic arteries. The evaluation of the vessels, including their movement, infiltration, changes in the diameter, and changes in blood flow, substantially affect the choice of surgical procedure to be adopted. Imaging the distal body and tail of the pancreas, and the entire length of the splenic vessels should be evaluated(. In this case, the area of spleen cavity, the structure of left kidney, large vessels in this area, and the entire adjacent retroperitoneal area should be scanned and evaluated.

Fig. 3

Power Doppler IOUS. Tumor of the uncinate process of the pancreas. HP – head of the pancreas, MV – superior mesenteric vein, TUP – tumor of the uncinate process of the pancreas

Biopsy performed during surgery is an important part of the differential diagnosis, especially in scenarios where there is no preoperative confirmation on the nature of focal changes in the pancreas(. The combination of IOUS and fine or core needle biopsy leads to increased diagnostic accuracy, with both: sensitivity and specificity reaching 90–100%(. In this study, the authors aim at performing intraoperative BACC, guiding the needle through the duodenum for changes located in the head of the pancreas. In such cases, tissue needles can be used, as well as “trucut” sets, allowing the sampling of optimal material for histopathological evaluation. This prevents the risk of pancreatic fistula, and in many cases, also of bleeding in the diagnosed area. When performing a biopsy within the body or tail of the organ, a narrower set is used, with the procedure supervised using Doppler, thus avoiding penetration to the surrounding vascular structures (Fig. 4). An important aspect of intraoperative ultrasound is the assessment of peripancreatic vascular infiltration, portal vein flow, superior mesenteric artery, and the celiac trunk. In one of the first comprehensive studies, Machi et al.( demonstrated a significant advantage of sensitivity, specificity and accuracy of IOUS in diagnosing malignant invasion to the portal vein flow, as compared to pre-operative examination – percutaneous ultrasound, angiography and computed tomography. IOUS accuracy was determined at 89.7%, as compared to the average of 64.1%, for other imaging procedures. Modern multidetector computer tomography (MDCT) allows for a better assessment of tumor severity with the ability to assess peripancreatic lymphadenopathy. These are particularly difficult to distinguish, especially in cases of an existing inflammatory reaction, extensive infiltration of surrounding structures, or abundant adipose tissue(. This was also reflected in our study (Fig. 5).

Fig. 4

Power Doppler IOUS. Hypoechoic tumor in the head of the pancreas. Intraoperative BAC, needle introduced through the duodenum. Needle bevel marked by an arrow

Fig. 5

IOUS. Cancer of the pancreatic head. Peripancreatic lymph nodes (marked by an arrow)

Another important issue is the assessment of cystic changes. Most often, these include pseudocysts, formed as a complication due to acute and chronic pancreatitis. It should be noted, however, that the changes may sometimes also include cysts and cystic tumors. According to current studies, 2–5% of the cystic lesions of the pancreas designate cancer and cystic tumors, and that these constitute up to 10% of all tumors of the pancreas(. Tumors of this type generally possess a diversified structure. A characteristic feature of serous adenocarcinomas cystoma are numerous small cysts, sometimes with internal calcification forming polycyclic structures. The presence of intraductal papillary mucinous neoplasia (IPMN) of the pancreas (IPMN) is indicated by the image of the cystic enlargement of the pancreatic duct, and the presence of non-uniformly thickened wall – mucinous cystic tumor and internal cystic lesions, and a cystic tumor followed by changes of the non-uniformly thickened wall, with often additional partitions, solid intramural nodules and peripheral calcification(. Depending on the type of tumor, these may include benign or malignant forms, structure infiltration and metastases, including lymph nodes and the liver(. IOUS examination is essential in the surgical treatment of cystic tumors, as it allows for accurate positioning of the changes and determining the condition of the adjacent vessels. It is important to note that these may be multiple tumors, unrecognized prior to the surgery. This is confirmed by our material, wherein the cystic tumor was recorded both in the body as well as in the tail of the pancreas (Fig. 6, 7).

Fig. 6

Doppler IOUS. Serous cystadenocarcinoma in the pancreas. “Honeycomb” structure

Fig. 7

Doppler IOUS. Secomd serous cystadenocarcinoma; slightly smaller tumor located in the tail of the pancreas

IOUS is an important study in surgery of pancreatic endocrine tumors. The most commonly imaged types include insulinomals, usually single lesions with reduced echogenicity, homogeneous, and well isolated(. In some cases, hormonally active tumors may be isoechogenic, as a results of which they are difficult to distinguish from the rest of the pancreatic parenchyma making the initial diagnostic imaging harder, particularly in percutaneous ultrasound. The use of a contrast agent (CEUS) and ultrasound heads with high-resolution of harmonic imaging has a significant impact on the proper imaging of the internal vascularity of the tumor, reducing the risk for potential diagnostic errors. This applies to both percutaneous and intraoperative examination. The increased cell flow is observed in pancreatic insulinomals, and – partially – in neuroendocrine tumors(. The presence of multiple of neuroendocrine tumor foci should also be kept in mind, as well as their non-pancreatic location(. The less frequently diagnosed neuroendocrine tumors include glucagonoma, gastrinoma, VIPoma, somastatinoma, and carcinoid(. These tumors give hypo- or izoechogenic ultrasound image, and like the insulinoma, they are usually well disconnected from the pancreatic parenchyma. More often, however, they present a malignancy, as exemplified by the VIPoma tumor, located in the tail of the pancreas, in the hilar region of the spleen (Fig. 8).

Fig. 8

IOUS. Hypoechoic, well-demarcated malicious VIPoma tumor located in the tail of the pancreas (arrows) in the hilar region of the spleen. Small internal calcification

The echogenicity of the pancreas is correlated with the patient's age, the amount of adipose tissue and fibrous elements. It is usually slightly larger in relation to the liver, and may be increased in the case of adipose tissue infiltration, and the changes occurring in chronic pancreatitis(. The inflammatory processes lead to local and extended destruction of the organ, causing changes in the internal echostructure and significant obstruction in determining the outer boundary as a result of infiltration of surrounding retroperitoneal space, which typically takes place due to acute pancreatitis. Surgical treatment for acute pancreatitis due to extensive infected necrosis, abscesses and pancreas abscesses, peripancreatic tissue, retroperitoneal space and concomitant intraperitoneal lesions, require the use of proper surgical technique. Preoperative imaging studies (ultrasound, CT) determine only generally the extent of lesion formation, which, due to extensive tissue damage, the exact location and nature, can only be assessed after, often complicated, laparotomy or opening of the retroperitoneal space. In such cases, IOUS allows for proper access to the affected area, determines the surgical planes, places the outbreak or outbreaks of largest disintegration lesions of necrosis that should be reached, removed and drained( (Fig. 9). This enables the surgeon to avoid damaging vital life structures, including the main vascular branches, infiltrated parts of the gastrointestinal tract, the structure of the bile duct and the main pancreatic duct. In such situations, it is important to evaluate Doppler images, which allows to distinguish space with no vital vessels, mainly tanks and fluid spaces and structures that may indicate major blood vessels.

Fig. 9

Doppler IOUS. Disintegrated tissues near the pancreas. Evaluation of blood around during planned access to the lesions in order to place a drain

Local complications in acute pancreatitis in the form of abscess or pseudocyst require careful differentiation, including intraoperative, due to considerable differences in surgical strategies. It is important to evaluate the fluid reservoirs, distinguishing acute phase reservoirs, pseudocysts and inflammatory fluid in the abdomen, often limited by inflammatory or post-operative adhesions. Good interpretation influences the choice of appropriate treatment, choice of the type of drainage, thus helping to avoid many postoperative complications. The characteristic echogenicity in the structure of the vessel may indicate the presence of dense fluid and gas, which is characteristic of an abscess(. A similarly characteristic echo image may suggest the present of hematoma or retroperitoneal phlegmon. Both the pancreatic pseudocyst and reservoir of the lesser sac may contain necrotic elements, necrosis of the pancreas and nectrotic adipose tissue fragments (Fig. 10). Intraoperative examination enables the surgeon to correctly determine the indications for their removal, particularly in cases where the elements are separated from the retroperitoneal space and are not vascularized. Intraoperative evaluation can also provide information about the concomitant gallbladder disease, cholelithiasis or choledocholithiasis(.

Fig. 10

IOUS. Pseudocyst of the pancreas after acute pancreatitis. Cyst with visible abscess, located to the rear of the stomach

Treatment of pancreatic abscesses depends on its location, the experience of the diagnostic and therapeutic personnel, and the assessment of the pancreatitis, including the condition of the pancreas, peripancreatic changes, and the general condition of the patient(. In cases where there is no immediate indication for surgery, pancreatic abscess can be addressed using minimally invasive procedures. Currently, percutaneous image-guided drainage is carried out, as well as internal drainage using endoscopic techniques and laparoscopy include the use of LUS( (Fig. 11). External drainage conducted when the pouch (reservoir) is located the organs, in order to prevent any damage to the bowel and adjacent organs. In cases of pancreatic abscesses, it is recommended to use large diameter tubing – from 14F to 24F, and – in some cases – even 30F – this is associated with high contents of abscesses fragments and the presence of necrotic tissue resulting from the decay of peripancreatic vessels and the pancreas itself.

Fig. 11

Endoscopic drainage of pancreatic abscess. Cystogastrostomy prosthesis during implanting

IOUS is a useful procedure in evaluating the position of pseudocysts in relation to certain parts of the gastrointestinal tract, primarily the stomach and duodenum. This allows for the determination of the correct drainage approach(. Adhesion to the stomach cyst may suggest the use of Jurasz’ method, i.e. cystogastrostomy. In the absence of connection with the stomach or the duodenum, or in cases where – despite correct position – anastomotic adhesion treatment is not possible due to technical reasons, attaching the duct to a loop of the small intestine is recommended (Roux-en-Y anastomosis). Furthermore, in the case where Jurasz’ method was used, Doppler IOUS allows for the selection of a suitable location for anastomosis, in which no major blood vessels are present, and consequently, where cutting the walls of the gastrointestinal tract will not cause major bleeding (Fig. 12).

Fig. 12

Doppler IOUS. Ooperational cystogastrostomy; IOUs with Doppler allows the selection of a suitable linking spot distant from larger vessels

Chronic pancreatitis can be correctly diagnosed using imaging examination. In some cases, however, examination may be inconclusive, especially when dealing with tumors. If the structure of the tumor can be seen as a degeneration of cysts, focal fibrosis and calcification, the presence of tumor inflammation can be suspected. If, however, the changes are ambiguous in nature, with a dominant solid structure, and degenerative features are poorly marked, a more detailed examination is necessary. This may include ultrasonography, intraoperative ultrasound and fine needle biopsy. These methods allow for a thorough definition of the border of both normal and pathological changes of the organ. The offer highly accurate image of the abnormal structure of the inflamed pancreas, seen as small pseudocysts, bands and hiperechogenic fibrosis(. They enable a correct evaluation of the extension of pancreatic ducts and their course, localized calcification in the main ducts and branches, and the surrounding parenchyma. They can also contribute to the proper differentiation of inflammatory and malignant tumors of the pancreas, including aspiration biopsy.

Tumors in the head of the pancreas due to chronic inflammation are accompanied by numerous factors of degenerative nature. With the right adjustment of the intraoperative probe, the surgeon can determine the tortuous, extended course of the pancreatic duct and the presence of numerous calcifications inside the duct and the perenchyma (Fig. 13). When performing drainage, mainly using Puestow's method, it is possible to determine the point of incision into the enlarged pancreatic duct, which makes the identification and removal of pancreas duct stones(. IOUS provides a correct imaging of the differences in the structure of cystic changes, litho-cystic and solid tumors in the pancreas itself and in the retroperitoneal space.

Fig. 13

IOUS. Chronic pancreatitis. Tortuous, expanded pancreatic duct with calcification present. Preparing for the Puestow procedure, creating an incision along the pancreatic duct, draining, and attaching the duct to a loop of the small intestine (Roux-en-Y anastomosis)

At first glance, intraoperative ultrasonography seems to prolong surgery time. However, in reality it often reduces the total time of the operation. It enables a thorough assessment of the changes occurring in the pancreas and the surrounding area is crucial, without extensive tissue preparation. The final interpretation of the results is not dependent on other medical staff, and can be carried out during surgery itself. In some of the cases, IOUS examination leads to the decision to change the scope of the operation or to use additional therapeutic procedures. This is mainly due to the complicated nature of the cases, both due to acute and chronic pancreatitis. The procedure has no major restrictions, except in cases of significant adiposity around the pancreas, or pancreatic infiltration, which impede direct assessment of the organ.

Pancreas treatments performed in referral centers due to the advanced stage of the changes, often require sophisticated diagnostic and surgery techniques. IUOS is now becoming a compulsory technology, allowing for proper classification and proper conduct of complex surgical procedures. It is one of the basic tools of the surgeon, and thus only the surgeon involved in pancreas surgery will benefit from the use of this method.

Conclusions

IOUS examination is mainly used for the determination of the level and extent of pancreatic cancer, the assessment of liver for the existence of metastases, and the imaging of small neuroendocrine tumors.

IOUS also plays an important role in the differentiation of cystic tumors of the pancreas and pseudocysts, differentiation and non-malignant tumors, mainly arising in the course of inflammation of the pancreas.

In cases of acute pancreatitis, IOUS enables a supervised surgery, the removal of necrotic tissues, abscesses and phlegmon in complicated cases.

IOUS is a useful procedure in the diagnosis and localization of pseudocysts, allowing for the selection of the appropriate corrective surgery.

IOUS is also very useful in monitoring of drainage procedures, treatment in complicated cases of chronic pancreatitis, cystic changes, and overpressure of the pancreatic system and choledocholithiasis.