Abdominal imaging

Imaging of the female pelvic floor is of rising interest due to an ageing population, harbouring an increasing incidence of pelvic floor disorders (PFD), and the rising need for comprehensive diagnosis and treatment. Magnetic resonance imaging (MRI) of the female pelvic floor combines high-resolution imaging with an excellent soft tissue contrast and provides the possibility to assess noninvasively and objectively a spectrum of possible disorders affecting the pelvic floor in one examination. There is general agreement that MRI of the pelvic floor should include static and dynamic MR images, whereas dynamic means imaging under maximum stress to the pelvic floor and MR defecography. Static MR images visualize pelvic floor anatomy and defects of the supporting structures, while dynamic MR images visualize pelvic organ mobility, pelvic floor weakness, pelvic organ prolapse (POP) and associated compartment defects. In this lecture, a standardized approach regarding indications, patient preparation, sequence acquisition, interpretation and reporting of MRI for diagnosis and grading of PFD is presented. Due to the different views of the clinical specialists involved in the treatment of PFD, adapting the MRI reporting scheme according to the speciality of the referring physician is discussed. Finally, the limitations of the technique are addressed.

Liver resection is proven to achieve long term survival in selected patients with primary or secondary focal liver lesions. Advances in surgical techniques including robotic liver surgeries, systemic adjuvant chemotherapy and postoperative intensive care improved the outcome of liver resection. Adequate liver remnant is crucial to guarantee the correct liver function after radical potentially curative liver resection. In borderline cases, portal vein embolisation (PVE), or associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) has been proposed before surgery to increase the liver remnant. Preoperative volumetric analysis of the liver based on imaging plays an essential role in the preoperative work-up previous to liver resection. Also the knowledge of the vascular hepatic anatomy and possible variants of the biliary system are also key aspects to avoid postoperative complications. Imaging tools based on multidetector computed tomography (MDCT) and magnetic resonance (MR) influencing preoperative decisions and surgical approaches will be discussed. The role of different imaging techniques as plain ultrasonography (US), contrast enhanced ultrasonound (CEUS), MDCT and MR for the detection and management of hepatic complications after liver resection or transplantation (infectious, vascular, biliar, parenchymatous (liver rejection) will be analysed.

Both benign and malignant pancreatic disease carry significant morbidity and mortality. Because of the fastidious nature of the pancreas and its local and regional anatomy, treatment of these disorders also carries significant morbidity. Indeed, perioperative morbidity of pancreaticoduodenectomy is approximately 30-40%. Due to the diversity of pathology, detection, and characterisation of postoperative complications can be challenging. Familiarity with the normal imaging appearances of the spectrum of surgical procedures and their complications is vital. In this presentation the common pancreatic surgical procedures performed for tumour resection (i.e., the Whipple’s operation, enucleation, central and distal pancreatectomy, spleen preserving distal pancreatectomy) and chronic pancreatitis (i.e., Puestow procedure, Beger procedure, Frey procedure) and their normal postoperative appearances are discussed. The common postsurgical complications including pancreatic fistulas and leaks, abscess formation, haemorrhage, and delayed gastric emptying are then described in detail.

Post operative assessment of the luminal GI tract is very complex and relies heavily on CT. It presents a major challenge for interpretation and detection of abnormalities in the context of a very broad range of normal post operative appearances. In judging whether the imaging appearances are normal or not it is essential to consider the time that has elapsed since the operation and the complexity of the procedure that was performed, since a straight forward procedure or one performed laparosscopically with carbon dioxide insufflation should have very little residual fluid or gas, compared with a complex open surgical procedure. Anastomotic leak is the most important complication to detect, and in this regard positive luminal contrast is the most sensitive for evaluation and this can be administered orally or rectally depending on the position of the anastomosis. An 8% concentration of 300mg/ml concentration non ionic contrast is used by the author. Other complications such as abscess can be detected by CT but this must be differentiated from haemostatic surgical material which is left in situ deliberately.

MRI has vast potential to non-invasively diagnose and characterize focal liver lesions as well as diffuse liver disease. Due to the large extent of different sequence types, various information about pathological changes can be obtained. Hence, it is sometimes difficult to shorten MRI protocols and to withdraw certain MRI sequences without losing relevant information. Furthermore, MRI of the upper abdomen can be challenging. Motion and breathing artifacts can considerably impede a reliable diagnostic workup. In addition, it can be difficult to acquire MR images during the correct contrast phases after i.v. gadolinium injection. Hence, it is crucial to choose and apply the right contrast delay. Strategies to overcome limitations and to handle the outlines challenges will be proposed in this lecture. A comprehensive and abbreviated examination protocol for liver MRI will be presented with a special focus on diffusion weighted imaging and liver specific contrast agents. Eventually, clinical cases and pitfalls will be discussed.

Magnetic resonance imaging/magnetic resonance cholangiopancreatography (MRI/MRCP) is increasingly used for the evaluation of patients with pancreatic diseases, such as pancreatic cystic neoplasms (PCN), pancreatic cancer and pancreatitis as well as for screening purposes, such as in individuals at increased risk of developing pancreatic malignancy (i.e. family history of pancreatic cancer, genetic factors, etc.). Particularly for the surveillance of patients with PCNs, MRI is the suggested imaging modality according to various existing clinical practice guidelines due to its exquisite contrast resolution, high sensitivity for the detection of lesion communication with the pancreatic ductal system and lack of ionizing radiation. However, MRI/MRCP protocols are time-consuming, costly and, in the case of serial follow-up examinations, the repeated use of gadolinium-based contrast agents raises potentially safety concerns. In this presentation, we will discuss various strategies for the development of abbreviated protocols useful in everyday clinical practice.

Magnetic resonance Imaging (MRI) is recommended as a second line investigation for characterisation of complex adnexal masses indeterminate on US. MRI gives superb contrast resolution and involves non-ionizing radiation. Typical protocols include both T1 and T2 weighted sequences, with imaging acquisition performed in 3 planes. Coronal FSE T2WI is very helpful in evaluating complex adnexal lesions. Adnexal lesions can be characterised by their specific signal characteristics on T1WI and T2WI. Simple fluid has homogeneous low signal on T1WI and high signal intensity on T2WI. Fat and haemorrhage have high signal intensity on T1WI. Fat suppression (FS) on T1W sequences is utilised to differentiate these entities. If the adnexal lesion demonstrates low or intermediate signal intensity on T1WI and low signal intensity on T2WI, these characteristics suggest fibrotic and/or smooth muscle components. Such lesions include pedunculated leiomyoma, fibroma, fibrothecoma, cystadenofibroma and Brenner tumours. Multi-phase contrast enhanced (CE) MRI after administration of intravenous gadolinium is very useful for characterisation of adnexal masses. Solid components will demonstrate enhancement, enabling the distinction between debris or retracting clot in the cyst wall from papillary projections. Subtraction images are essential to evaluate enhancing nodules within a background of hyperintense T1W lesion. Gadolinium also improves detection of peritoneal and omental implants in case of ovarian carcinoma. Dynamic-CE (DCE)-MRI are not yet routinely performed in evaluation of adnexal masses. Diffusion-weighted imaging (DWI) is very useful for visualisation of peritoneal implants.

Anastomotic leaks on CT are heralded by a number of signs including increasing free gas and free fluid in the abdomen, localised fluid around the anastomosis and in particular the extravasation of positive contrast from the bowel lumen. This is recommended for routine use in the post operative evaluation of patients wherever possible. Surgeons utilitise haemostatic agents in the intraoperative management of bleeding. These can cause confusion in imaging interpretation and can mimic an abscess. Radiologists should have a heightened awareness of this appearance and discuss such cases with the surgical team for clarification. Similarly retention of surgical swabs remains a substantial cause of morbidity for patients in the post operative period. Such swabs are readily identifiable by a radiolucent marker and in such cases the surgical team needs immediate notification to allow a return to theatre for swab retrieval.

Abdominal ultrasound plays a pivotal role in the imaging workup of patients with suspected appendicitis. It should be the primary modality, and only in case of a negative or inconclusive examination should it be followed by CT or MR. The specific advantages of US over CT are: US has an image definition in the close range which is much higher than that of CT. US is more interactive than CT. The patient’s history as well as the painful area or palpable mass can directly be correlated with the US findings. US is real time and shows peristalsis, pulsations and blood flow. US also shows the effects of respiration, Valsalva manoeuvre, gravity and compression with the probe, allowing to assess whether the appendix or other organs such as the bowel and gallbladder are soft or rigid. US allows immediate US-guided puncture of intraperitoneal fluid and drainage of pus. US in appendicitis should be performed with graded compres­sion. Compression is necessary to displace or compress bowel to eliminate the disturbing influence of bowel gas and to approach the pathological structure close­ly. This allows the use of a high-frequency transducer with a better image quality. The final US report should be integrated with the clinical findings, laboratory data, CT-scan and possible other radiolo­gical examinations. It is clear that the US examination, as described here, should not be performed by a technician or by a clinician, but by an experienced (abdominal) radiologist.

The first investigations in patients with suspected gallstone disease, especially if stones within the common bile duct (CBD) are suspected, are US and liver function tests (LFTs). On the basis of this, the risk of CBD stones can be estimated and the decision whether or not to perform the next test, MRCP, can be made. In the presence of stones in the gallbladder, the risk increases with a CBD of > 8 mm and increasing abnormal LFTs. My preference is for 2D T2 sequences without fat saturation in two planes. Breath-hold when possible is preferred in the interests of time, but can be gated in those that struggle. HASTE/SS-FSE/FSE-ADA/FASE is the first set of sequences, followed by FISP/GRASS/FFE/SARGE if a diagnosis is not made as stones vary in their conspicuity between the sequences. The examination can be terminated as soon as a positive diagnosis is made. T1-weighted images occasionally help.

The prognosis of pancreatic adenocarcinoma is very poor, and little improvement has been reported in the past several decades. Only a low percentage of patients in whom pancreatic cancer is detected at an early stage without local infiltration have the potential for long-term survival after surgical resection. The earliest possible diagnosis may be the most effective way to improve the prognosis. Dilatation of the main pancreatic duct may represent a secondary sign of pancreatic adenocarcinoma. Therefore, the diagnosis of dilated main pancreatic duct may be a predictive sign of pancreatic adenocarcinoma; therefore, careful follow-up in people with such signs and eventually prompt treatment have been recommended. Pancreatic endocrine neoplasms are relatively rare, with an incidence rate of approximately five cases per one million person-years. Some pancreatic endocrine neoplasms release hormones into the blood stream that cause clinical syndromes, whereas others are non-syndromic and present as a mass lesion. At diagnostic imaging, pancreatic endocrine neoplasms typically produce hyperenhanced well-demarcated lesions that are best seen on arterial phase images. Pancreatic endocrine neoplasms may be responsible for pancreatic duct stenosis, even when they are small in size (<2 cm) and be responsible for marked dilatation of the main pancreatic duct and/or marked atrophy of the upstream pancreas. Intraductal papillary mucinous neoplasm (IPMN) originates from the ductal epithelium and overproduce mucin which is responsible for the dilatation of the main pancreatic duct and/or the side branches. Diagnostic imaging is helpful in the diagnosis and follow-up of these patients.

Liver biopsy is the most common invasive procedure of the liver. Indications of biopsy in diffuse liver diseases have declined due to improvements in noninvasive assessment of fibrosis and steatosis. On the contrary, biopsy of liver tumours is still indicated mostly for diagnostic purpose and to a lesser extent for assessing the prognosis or the prediction of tumour response. Three keys are important. First, check the indication. There are very few contraindications (mostly related to coagulation disorders) and the most important is to ensure that there is a good indication for liver biopsy. Second, use ultrasound guidance, which is faster, easier and more accurate than CT. It allows real-time control. Third, if a primary tumour liver is considered, always perform a biopsy in the adjacent liver. This will help the pathologist in the diagnosis.

Acute mesenteric ischaemia (AMI) is defined by inadequate blood supply through the mesenteric vessels resulting in intestine injury and carries a high mortality rate. A combination of two phenomena is needed to generate AMI: vascular insufficiency and intestinal injury. The diagnosis of AMI should be made as soon as possible, since early stages of ischaemia are reversible if properly treated. The three main messages for the radiologist are: 1) CT angiography (CTA) should use a triple-phase protocol (unenhanced, arterial and portal venous phase), 2) assessment of bowel wall abnormalities at CTA (decreased enhancement, increased attenuation on pre-contrast phase, wall thickening, wall thinning) is a major step in the interpretation of CT scans and 3) always carefully check the mesenteric vessels (for thrombus, embolism, dissection) in patients with acute abdominal pain of unknown origin.

For diagnosis of acute pancreatitis, at least two of the three following criteria, (1) abdominal pain consistent with pancreatitis, (2) increase (≥ 3-fold) in serum amylase or lipase levels and (3) imaging findings of acute pancreatitis, have to be fulfilled. According to the Revised Atlanta Classification, the disease is categorized as interstitial oedematous or necrotizing pancreatitis. Development of necrosis may take some time, so that CT imaging should be performed not earlier than 2-3 days after clinical onset. Imaging too early may lead to underestimation of disease severity. Necrotizing pancreatitis presents with either combined pancreatic and peripancreatic necrosis (most common) or with pancreatic necrosis or with peripancreatic necrosis alone. Acute necrotic collections (ANC) in the early phase may evolve into walled-off necrosis (WON) in the late stage (≥ 4 weeks). A WON containing chunks of digested fat and parenchyma must not be confused with a pseudocyst containing enzymatic fluid (requiring different therapy). They may appear similarly hypodense at CT, but US or MRI will show the predominantly solid nature of a WON. Secondary infection of necrotizing pancreatitis usually occurs in the 3rd week after onset or later. Diagnosis of infection is difficult based on imaging alone. Infection is more likely if collections have broad contact with bowel. Gas within a collection is not a sensitive sign, but quite specific. In case of infection, percutaneous aspiration is sought, followed by drainage in positive cases. However, necrotic collections with large proportions of debris require a more aggressive approach for clearance.

My three top tips for Crohn's disease. In this session we are going to highlight the MUSTs in the assessment of Crohn’s disease using cross-sectional imaging techniques: (1) What to look for first: thickness and enhancement, and T2 sequences. (2) What to look after: complications- all sequences. (3) Not forget to look at: other sequences, and areas other than the bowel.

Follow-up of liver metastases relies mostly on imaging. The need for standardisation was initially prompted by clinical trials. Several systems, from WHO to RECIST, have been proposed, allowing better intra- and interobserver reproducibility and guiding treatment strategy. However, the need for follow-up might be different according to clinical situations, like neo-adjuvant, palliative or adjuvant therapy. The standard might also be adapted to the type of drug, cytotoxic, targeted or immune therapies. Therefore, the radiologist needs to be aware of the clinical situation and learn to identify the drug, to perform a personalised evaluation.

Perforation of the GI tract represents an emergency and life-threading condition. The causes of perforation may be traumatic (endoscopy, blunt trauma, ingested foreign body), inflammatory (peptic ulcer disease, diverticulitis, appendicitis, Crohn’s disease or other enteritis), bowel schema or neoplasms. Clinical diagnosis may be difficult and patients may be first radiologically evaluated with plain radiographs or ultrasound, but with limited information in cases of perforation. CT scanning is by far the imaging method of choice in these patients. CT findings of GI tract perforation can be direct or indirect. Direct findings include free air or/and oral contrast either intra- eller retroperitoneal. Indirect findings comprise inflammatory mass surrounding an appendicolith or a radiopaque foreign body. Non-specific findings include bowel wall thickening, mesenteric infiltration, interloop free fluid and abnormal bowel wall enhancement. With the use of both direct and indirect findings, the sensitivity of CT in diagnosing GI tract perforation is up to 92%. False-positive results usually occur in post-operative patients, where free air as a result of previous operation can be misdiagnosed as a sign of anastomotic leak or iatrogenic bowel trauma. CT is also able to depict the site of perforation with an overall accuracy between 82 and 90% and the cause of perforation in up to 67% of cases. It is well documented that CT plays a crucial role in the assessment of patients with GI tract perforation, by offering fast and accurate essential information to the clinicians and enabling the most correct therapeutic choice.

Bowel obstruction is responsible for a considerable number of surgical admissions for acute abdominal pain in the emergency department. It has a high morbidity and mortality if left untreated. The diagnosis can be suggested by plain abdominal films, but CT, and particularly contrast-enhanced CT, plays a crucial role in the diagnosis and management of these patients. Not only can CT confirm the diagnosis, but it can also grade the severity of the obstruction, locate it, and provide the aetiology. A dedicated technique is necessary and multiplayer reconstructions in the coronal and sagittal planes are mandatory. The causes of small bowel obstruction can be divided into intrinsic (inflammatory diseases, neoplasia), extrinsic (adhesions, hernias), and intraluminal (gallstones, bezoars). The three most frequent causes of large bowel obstruction are neoplasm, volvulus, and diverticulitis. The imaging findings vary according to the cause, and some are very specific. CT can provide a quick diagnosis and allow an early and optimal management of these patients, contributing to better patient care and improved survival.

Acute cholangitis is a serious condition which occurs most commonly in the context of bile duct obstruction due to stone disease or strictures. Unless diagnosed and treated correctly, acute cholangitis may lead to liver abscess formation, septicaemia and multiorgan failure. The role of noninvasive imaging is to determine the presence of obstruction of the biliary tree., as well as its level and its cause. Although ultrasonography or computed tomography are most commonly used in the emergency situation, magnetic resonance imaging offers the most detailed diagnostic results, especially with regard to the cause of obstruction. Depending on the level and the cause of bile duct obstruction, decompression of the biliary tree may be done by means of minimally invasive interventional techniques via the endoscopic- retrograde or the percutaneous - transhepatic approach. Acute gallbladder disease is most often associated with calculus disease and obstruction of the cystic duct. Depending on the clinical situation, a diagnostic workup may be required to exclude the simultaneous presence of bile duct stones.

Pancreatic cancer is the fourth leading cause of cancer-related death. Surgical resection is the sole curative treatment option; however, only 15%-20% are resectable at the time of diagnosis. Furthermore, the prognoses for patients with pancreatic cancer remain poor. Although the 5-year survival rate is up to 20% after complete resection, it is further improved to more than 75% in patients with a diagnosis of stage 1 disease. Computed tomography (CT) remains the initial imaging modality of choice for pancreatic solid neoplasms, because recent improvements in multidetector CT technology, including improved temporal and spatial resolution, have facilitated more precise timing of multiphasic imaging and increased the accuracy of CT for the detection and staging of pancreatic adenocarcinoma. Recently, magnetic resonance (MR) imaging has acquired a role in the early diagnosis of adenocarcinoma, because of diffusion-weighted (DW) MR imaging. By means of DW imaging, MRI is able to depict changes in water mobility caused by interactions with cell membranes, macromolecules, and alterations to the tissue environment, and thus provides a tissue contrast that is different from that on conventional T1- and T2-weighted images. DW imaging plays a role in oncology for tumour detection, in general. DW imaging allows detection of pancreatic adenocarcinomas with high sensitivity and specificity, because it appears hyperintense compared with the rest of the gland. DW-MR imaging is also useful in finding small functioning neuroendocrine neoplasms, responsible for a clinical syndrome, but difficult to diagnose because of their small size.

Magnetic resonance enterography (MRE) is increasingly used, particularly for Crohn’s disease assessment. It has an evolving role not only in grading inflammation and detecting complications, but also for monitoring the course of the disease. The diagnostic accuracy of MRE is heavily influenced by the technical quality of the examination. Patient preparation, bowel distension, sequence selection and scan technique must all be optimised to produce high-quality examinations. This presentation will review the recommendations of the recent ESGAR consensus statement on MRI small bowel imaging and will address commonly encountered problems that can arise before and during scan acquisition. The utility of novel sequences such as DWI and motility will also be discussed.