Imaging of the retroperitoneum

Retroperitoneal anatomy with the aid of pathologic fluid: An imaging pictorial review

The retroperitoneum, a complex anatomical space within the abdominopelvic region, encompasses various vital abdominal organs. It is compartmentalized by fascial planes and contains potential spaces critical in multiple disease processes, including inflammatory effusions, hematomas, and neoplastic conditions. A comprehensive understanding of the retroperitoneum and its potential spaces is essential for radiologists in identifying and accurately describing the extent of abdominopelvic disease. This pictorial review aims to describe the anatomy of the retroperitoneum while discussing commonly encountered pathologies within this region. Through a collection of illustrative images, this review will provide radiologists with valuable insights into the retroperitoneum, facilitating their diagnostic proficiency to aid in appropriate patient clinical management.

Pediatric retroperitoneal non-organ-originated malignancies: An analysis based on SEER database

Retroperitoneal non-organ-originated malignancies are rare pediatric tumors with challenging diagnosis and treatment. The present study aimed to analyze the clinicopathological characteristics, treatment, and prognosis of retroperitoneal non-organ-originated malignancies. In the study, we included the pathological diagnosis of pediatric retroperitoneal non-organ-originated malignant tumors between 2000 to 2019 through the updated Surveillance, Epidemiology, and End Results database. We use the Kaplan-Meier survival curve to calculate the overall survival (OS) and cancer-specific survival (CSS). The risk of all-cause death and disease-specific death were analyzed using Cox proportional hazard regression model and Fine-and-Grey competitive hazard model, respectively. In the study, a total of 443 pediatric retroperitoneal non-organ-originated malignancies were included. Of them, only 22.3% of patients had no metastatic disease, 42.9% had distant metastasis and 34.8% had locally advanced diseases. The primary pathological tumor was neuroblastoma followed by germ cell tumor. The overall 10-year OS and CSS were 70.7% and 73.1%, respectively, and the 10-year OS and CSS of metastatic diseases were 54.4% and 56.6%, respectively. Older children, worse tumor stage at diagnosis, incomplete resection, and prolonged time from diagnosis to treatment were significantly associated with worse survival outcomes. Radiotherapy and chemotherapy did not significantly improve the prognosis of patients without complete tumor resection. The study indicated that most pediatric retroperitoneal non-organ-originated malignancies diagnosed with metastatic diseases have plagued treatment. Radiotherapy and chemotherapy are the main treatment methods for children unable to undergo complete surgical treatment. However, these treatments do not reach the same therapeutic effect as complete tumor resection after early diagnosis. Hence, early diagnosis and surgery for complete tumor resection are of utmost importance.

Incidence, risk factors, and outcomes of venous thromboembolism in patients undergoing surgery for retroperitoneal tumors: a propensity-matched retrospective cohort study

BACKGROUND

Venous thromboembolism (VTE) is a common postoperative complication; however, the incidence and risk stratification of postoperative VTE in patients with retroperitoneal tumor remains unclear. The authors aim to quantify the incidence, identify risk factors, and determine the outcomes of VTE in patients undergoing retroperitoneal tumor surgery.

METHODS

The authors retrospectively reviewed the characteristics, perioperative outcomes, and overall survival (OS) of patients (VTE and non-VTE) who underwent retroperitoneal tumor surgery between 2015 and 2020. Perioperative and oncologic outcomes were compared using propensity-matching and Cox analyses.

RESULTS

Of 1223 patients with retroperitoneal tumor surgery, 2.1% had VTE. Age [odds ratio (OR) 1.140, 95% CI: 1.053-1.239, P =0.004], recurrence (OR 1.851, 95% CI: 1.241-2.761, P =0.003), and vascular resection (OR 2.036, 95% CI: 1.054-3.934, P =0.034) were independent risk factors, with significant between-group differences regarding age, recurrence, sarcoma, organ resection, vascular resection, and operation time. No between-group differences in 30-day all-cause mortality (8 vs. 4%, OR 0.657, 95% CI: 0.375-1.151, P =0.427) and major complications (12 vs. 8%, OR 0.775, 95% CI: 0.483-1.244, P =0.572) were observed. Mean hospitalization duration (20.1 vs. 22.9 days, OR 1.153, 95% CI: 1.022-1.386, P =0.033) and ICU stay (3.2 vs. 5.5 days, OR 1.193, 95% CI: 1.034-1.347, P =0.012) were shorter in non-VTE versus VTE, respectively, with inferior OS (hazard ratio 2.090, 95% CI: 1.014-4.308, P =0.046) in VTE.

CONCLUSIONS

Age, recurrence, and vascular resection are positively associated with VTE, which is associated with inferior OS.

Imaging of renal emergencies: Review of infectious, hemorrhagic, vascular, and traumatic etiologies

Diagnostic imaging allows for accurate and early recognition of acute renal pathologies, thus allowing for appropriate clinical triage, life-saving treatments, and preservation of renal function. In this review, we discuss the clinical presentation and imaging findings of renal emergencies with infectious, hemorrhagic, vascular, and traumatic etiologies.

Solid Primary Retroperitoneal Masses in Adults: An Imaging Approach

Mass lesions in the retroperitoneal space may be primary or secondary. Primary retroperitoneal mass lesions are relatively uncommon as compared to pathology that arises secondarily from retroperitoneal organs. These may be solid or cystic lesions. The overlapping imaging features of various solid primary retroperitoneal tumors make the diagnosis difficult, and hence, histopathology remains the mainstay of diagnosis. This paper provides a brief review of the anatomy of the retroperitoneal space and provides an algorithmic approach based on cross-sectional imaging techniques to narrow down the differential diagnosis of solid primary retroperitoneal masses encountered in the adult population.

ACR Appropriateness Criteria® Suspected Retroperitoneal Bleed

The initial diagnosis of retroperitoneal bleeding can be challenging by physical examination and clinical presentation. Prompt imaging can make the diagnosis and be lifesaving. When selecting appropriate imaging for these patient's, consideration must be made for sensitivity and ability to image the retroperitoneum, as well as speed of imaging.The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Retroperitoneum ganglioneuroma: imaging features and surgical outcomes of 35 cases at a Chinese Institution

Background

The preoperative evaluation is crucial for diagnosis and surgical plan of retroperitoneum ganglioneuroma (GN). In this study, we reviewed a relatively large series of histopathological proved retroperitoneum GN cases, summarized the imaging features and further depicted risk factors of increased surgical blood loss.

Methods

A total of 35 (18 male, 17 female) patients were retrospectively enrolled from January 2012 to June 2019 at our institution. Among them, 24 patients had undergone CT scans and 19 patients had undergone MR examination before treatment. The clinical and radiological features were analyzed and the relationships between image features and surgical blood loss were evaluated.

Results

The media age of the involved 35 patients was 40 years (range, 14–66 years). The histological tumor size was 10.12 ± 4.56 cm for average. Retroperitoneum GN was relatively low density on unenhanced CT images and showed delayed progressive enhancement on enhanced CT and MR images. The whorled sign could be seen in 14 patients. The vessel encasement sign could be found in 17 patients. Univariate analysis revealed maximal tumor size measured on axial image, maximal tumor size measured on coronal image, encasing one or both renal pedicles, encasing the aorta and/or vena cava and whorled sign on MRI showed significant difference between the blood loss ≥ 400 ml and blood loss < 400 ml group. Logistic regression further detected that maximal tumor size measured on axial images (OR: 1.12; 95% CI: 1.02–1.24; P = 0.023) and encasing one or both renal pedicles (OR: 22.39; 95% CI: 1.35–372.99; P = 0.030) were independently correlated with surgical blood loss.

Conclusions

Preoperative CT and MR imaging analysis was valuable for both diagnosis and surgical risk prediction of retroperitoneum GN.

Radiologic-Pathologic Correlation of Primary Retroperitoneal Neoplasms

An earlier incorrect version of this article appeared in print. The online version is correct.

Effects of Manual Therapy on the Diaphragm in the Musculoskeletal System: A Systematic Review

OBJECTIVES

To analyze the effects at the musculoskeletal level of manual treatment of the diaphragm muscle in adults.

DATA SOURCES

Systematic review using 4 databases: PubMed, Science Direct, Web of Science, and Scopus.

STUDY SELECTION AND DATA EXTRACTION

Two independent reviewers applied the selection criteria and assessed the quality of the studies using the Physiotherapy Evidence Database scale for experimental studies. A third reviewer intervened in cases where a consensus had not been reached. A total of 9 studies were included in the review.

DATA SYNTHESIS

Manual therapy directed to the diaphragm has been shown to be effective in terms of the immediate increase in diaphragmatic mobility and thoracoabdominal expansion. The immediate improvement in the posterior muscle chain flexibility test is another of the most frequently found findings in the evaluated studies. Limited studies show improvements at the lumbar and cervical level in the range of motion and in pain.

CONCLUSION

Manual diaphragm therapy has shown an immediate significant effect on parameters related to costal, spinal, and posterior muscle chain mobility. Further studies are needed, not only to demonstrate the effectiveness of manual diaphragm therapy in the long-term and in symptomatic populations, but also to investigate the specific neurophysiological mechanisms involved in this type of therapy.

Diagnostic approach to primary retroperitoneal pathologies: what the radiologist needs to know

Retroperitoneal soft tissue lesions represent a wide range of disease processes with overlapping imaging findings. Familiarity with the CT and MR characteristics of these conditions is important to guide clinical evaluation. We review the tissue types, characteristic clinical, demographic, and imaging features of retroperitoneal tumors and tumor-like non-neoplastic conditions with CT and MR correlation, including anatomic and imaging clues, and provide a diagnostic approach to aide the radiologist in making a specific diagnosis.

Minimally Invasive Surgery of Primary Retroperitoneal Tumors from the Perspective of General Surgeons: 6 Years of Experience at a Single Institution

Objective: This retrospective study aimed to present our surgical experience in patients with primary retroperitoneal tumors (PRTs) who underwent laparoscopic surgery and to compare the results with those of patients who underwent an open operation. Materials and Methods: We analyzed the medical data of patients who underwent retroperitoneal tumor resection through laparoscopic surgery or open operation between February 2014 and November 2019. Results: In total, 77 patients were enrolled. In total, 37 patients underwent open surgery and 40 patients underwent laparoscopic surgery. The tumor size in the open surgery group (10.2 ± 5.4 cm) was more significant than that in the laparoscopic surgery group (6.5 ± 3.1 cm) (P < .001). No difference was observed in operative time, blood loss, and transfusion between the two groups. Postoperative hospitalization in the open group (8.43 ± 2.77 days) was longer than that in the laparoscopic group (5.63 ± 2.16 days) (P < .001). The patients with PRTs in the IV area had minimal bleeding (16.67 ± 40.82 mL) and minimum postoperative hospitalization (3.83 ± 1.60 days). Conclusions: Laparoscopic resection of PRT is feasible in the selection of appropriate cases. The advantages are small trauma, light pain, quick recovery, and short hospital stay. It is especially suitable for benign PRTs with small size and cystic or small adhesion with vital organs or great vessels.

Retroperitoneal tumors: Review of diagnosis and management

Retroperitoneal tumors are extremely rare tumors occurring in the retroperitoneum. Retroperitoneal tumors are divided into benign tumors and malignant tumors, including retroperitoneal sarcoma. Approximately 70-80% of primary retroperitoneal soft-tissue tumors are malignant; however, these only account for 0.1-0.2% of all malignancies. Retroperitoneal sarcoma is an orphan malignant disease with a low incidence. The information on benign retroperitoneal tumors is limited. The American Joint Committee on Cancer/TNM classification updated to the 8th edition in 2017. In 2010, three new drugs for soft tissue sarcoma were approved based on the results of phase III trials, but the histological subtypes of the patients enrolled in the trials of each drug differed. Recently, in addition to surgery for retroperitoneal sarcoma, the effectiveness of perioperative radiation therapy has become interesting. For malignant retroperitoneal tumors and retroperitoneal sarcoma, survival improvement and locoregional recurrence prevention can be undertaken by carrying out surgery to secure negative margins with wide and combined resection of some adjacent organs, and cooperation with a trained medical team comprising of radiologists, pathologists and medical oncologists in centralized hospitals. Some clinical trials aimed at further improving treatment results by adding preoperative chemotherapy and radiation therapy based on histological confirmation using a correct needle biopsy are in progress. In recent years, molecular profiling has been used to select eligible patients for chemotherapy. In the future, precision medicine with next-generation sequencing technology will be expected among the diverse and potential future treatments for retroperitoneal sarcoma. In this review, we summarized the current state of retroperitoneal tumors and retroperitoneal sarcoma.

Primary retroperitoneal germ cell tumor in an adult female: A case report

RATIONALE

Primary retroperitoneal germ cell tumors are uncommon and especially rare in female patients. However, this type should be included in the differential diagnosis of retroperitoneal tumors that may metastasize from the gonads and be a primary tumor.

PATIENT CONCERNS

An abdominal mass was detected in a 38-year-old woman during physical examination, which was accompanied by left renal obstructive hydrops. She was admitted to our institution for further investigation. The patient had no obvious clinical symptoms, and the levels of serum tumor markers did not signifificantly increase. Abdominal noncontrast enhanced and contrast-enhanced computed tomography revealed a retroperitoneal neoplasm that invaded the left ureter, thereby causing left hydronephrosis.

DIAGNOSES

Imaging examination characterized the tumor as malignant based on its invasion in the left ureter. Histopathology and immunohistochemistry confifirmed the resected tumor as a dysgerminoma. The primary gonad-derived germ cell tumor was not found in the pelvis; therefore, the patient was fifinally diagnosed with primary retroperitoneal germ cell tumor.

INTERVENTIONS

Preoperative examination was completed, and the retroperitoneal mass was resected.

OUTCOMES

During the short-term follow-up, no tumor recurrence was detected.

LESSONS

Primary retroperitoneal seminoma should be included in the differential diagnosis of primary retroperitoneal tumors in female patients. The primary retroperitoneal seminoma/anaplastic tumor has an obvious occupying effect and can easily invade the surrounding structures. However, surgical resection of such tumors is an optional treatment strategy.

Clinical characteristics and surgical outcomes of retroperitoneal tumors: a comprehensive data collection from multiple departments

BACKGROUND

There are only a limited number of comprehensive reports for retroperitoneal tumors (RPTs). The aim of this study was to perform an interdepartmental data collection for RPTs and to comprehensively clarify the clinical characteristics of this rare disease.

METHODS

All patients who were diagnosed with RPT from January 2005 to July 2018 in a single institution were included. The analyzed factors included demographics, clinical features, treatment methods, pathological diagnosis, and prognosis.

RESULTS

A total of 422 patients (215 males and 207 females) with primary RPTs were identified. Biopsy for RPT was performed in 180 patients (43%). Among the 422 patients, 239 (57%) underwent surgery. The most common tissue origin was mesodermal (n = 99, 41%), followed by neurogenic (n = 54, 23%), extragonadal (n = 27, 11%), and metastatic tumors (n = 13, 5%). Among the 99 resected mesodermal tumors, the most common pathological subtypes were liposarcoma (n = 55, 56%) and leiomyosarcoma (n = 16, 16%). The long-term outcomes after surgery were analyzed in patients with intermediate and malignant sarcomas (including liposarcoma, leiomyosarcoma, and others combined, n = 71). The 3- and 5-year disease-free survival rates in the intermediate tumors were 68.2% and 54.2%, respectively, whereas those in the malignant tumors were 48.6% and 28.9%, respectively. The 3- and 5-year overall survival rates in the intermediate tumors were 100% and 94.1%, respectively, whereas those in the malignant tumors were 78.4% and 72.8%, respectively (p = 0.009).

CONCLUSIONS

The clinical manifestations of RPTs were extremely variable. Recurrence after repeating resection is commonly observed in patients with malignant retroperitoneal sarcoma.

Update on MR urography (MRU): technique and clinical applications

Magnetic resonance imaging of the upper tract (pyelocalyces and ureters) or MR Urography (MRU) is technically possible and when performed correctly offers similar visualization of the upper tracts and for detection of non-calculous diseases of the collecting system similar specificity but with lower sensitivity compared to CTU. MRU provides the ability to simultaneously image the kidneys and urinary bladder with improved soft tissue resolution, better tissue characterization and when combined with assessment of the upper tract, a comprehensive examination of the urinary system. MRU requires meticulous attention to technical details and is a longer more demanding examination compared to CTU. Advances in MR imaging techniques including: parallel imaging, free-breathing motion compensation techniques and compressed sensing can dramatically shorten examination times and improve image quality and patient tolerance for the exam. This review article discusses updates in the MRU technique, summarizes clinical indications and opportunities for MRU in clinical practice and reviews advantages and disadvantages of MRU compared to CTU.

Practical approach to primary retroperitoneal masses in adults

Primary retroperitoneal masses constitute a heterogeneous group of uncommon lesions and represent a challenge due to overlapping imaging findings. Most are malignant lesions. Although they are more prevalent in adults, they can occur at any age. Such lesions are classified as primary when they do not originate from a specific retroperitoneal organ and are divided, according to the image findings, into two major groups: solid and cystic. The clinical findings are nonspecific and vary depending on the location of the lesion in relation to adjacent structures, as well as on its behavior. The main imaging methods used for staging and surgical planning, as well as for selecting the biopsy site and guiding the biopsy procedure, are computed tomography and magnetic resonance imaging. In most cases, the treatment is challenging, because of the size of the lesions, vascular involvement, or involvement of adjacent organs. In this article, we present a review of the retroperitoneal anatomy and a practical approach to the main imaging features to be evaluated, with a view to the differential diagnosis, which can guide the clinical management.

Retroperitoneal Leiomyosarcoma From the Radiologic Pathology Archives

Leiomyosarcoma is a malignant neoplasm that shows smooth muscle differentiation. It is the second most common sarcoma to affect the retroperitoneum. Retroperitoneal leiomyosarcomas may grow to large sizes before detection and may be an incidental finding at imaging. When symptomatic, retroperitoneal leiomyosarcoma may cause compressive symptoms, including pain. Retroperitoneal leiomyosarcoma most commonly manifests as a large soft-tissue mass, with areas of necrosis. The most frequent pattern of growth is an entirely extravascular mass. Less commonly, leiomyosarcoma may demonstrate both extravascular and intravascular components. Rarely, retroperitoneal leiomyosarcomas are completely intravascular, typically arising from the inferior vena cava. Given its variable imaging features, a large variety of neoplastic and nonneoplastic conditions are included in the differential diagnosis of retroperitoneal leiomyosarcoma. In this review, the authors discuss retroperitoneal leiomyosarcoma, with emphasis on the pathologic basis of disease, and illustrate the multimodality imaging appearances of retroperitoneal leiomyosarcoma using cases from the Radiologic Pathology Archives of the American Institute for Radiologic Pathology. The authors review important differential considerations of retroperitoneal leiomyosarcoma, focusing on the extravascular pattern of growth, and emphasize clinical and imaging features that help radiologists differentiate leiomyosarcoma from the most frequent mimics. The information presented in this review will aid radiologists in fulfilling their key roles in the diagnosis, operative planning, and follow-up of patients with retroperitoneal leiomyosarcoma.

Understanding Retroperitoneal Anatomy for Lateral Approach Spine Surgery

Lateral approach spine surgery provides effective interbody stabilization, and correction and indirect neural decompression with minimal-incision and less invasive surgery compared with conventional open anterior lumbar fusion. It may also avoid the trauma to paraspinal muscles or facet joints found with transforaminal lumbar interbody fusion and posterior lumbar interbody fusion. However, because lateral approach surgery is fundamentally retroperitoneal approach surgery, it carries potential risk to intra- and retroperitoneal structures, as seen in a conventional open anterior approach. There is an innovative lateral approach technique that reveals different anatomical views; however, it requires reconsideration of the traditional surgical anatomy in more detail than a traditional open anterior approach. The retroperitoneum is the compartmentalized space bounded anteriorly by the posterior parietal peritoneum and posteriorly by the transversalis fascia. The retroperitoneum is divided into three compartments by fascial planes: anterior and posterior pararenal spaces and the perirenal space. Lateral approach surgery requires mobilization of the peritoneum and its content and accurate exposure to the posterior pararenal space. The posterior pararenal space is confined anteriorly by the posterior renal fascia, anteromedially by the lateroconal fascia, and posteriorly by the transversalis fascia. The posterior renal fascia, the lateroconal fascia or the peritoneum should be detached from the transversalis fascia and the psoas fascia to allow exposure to the posterior pararenal space. The posterior pararenal space, however, does not allow a clear view and identification of these fasciae as this relationship is variable and the medial extent of the posterior pararenal space varies among patients. Correct anatomical recognition of the retroperitoneum is essential to success in lateral approach surgery. Spine surgeons must be aware that the retroperitoneal membrane and fascia is multilayered and more complex than is commonly understood. Preoperative abdominal images would facilitate more efficient surgical considerations of retroperitoneal membrane and fascia in lateral approach surgery.

Retroperitoneal fibrosis and constrictive pericarditis-IgG4 related diseases: A case report

Retroperitoneal fibrosis (RPF) is a rare disease characterized by infiltration of inflammatory cells and deposition of thickened fibrous tissues. The present study presents the case of a 53-year-old patient treated for generalized weakness and fatigue for 1 year prior to hospitalization. A cardiac ultrasound revealed pericardial effusion that required pericardiocentesis, during which 1,400 ml serous fluid with the characteristics of an exudate was aspirated. A pericardiectomy was performed due to persistent effusion and histological examination indicated pericardial fibrosis. A thoracic-abdominal computed tomography scan revealed the presence of retroperitoneal fibrosis. The patient was treated with corticosteroids and azathioprine. Follow-up examinations showed a significant reduction in the amount of abdominal fibrous tissue and no increase in pericardial effusion 1 year following the end of treatment. The patient continues to have regular follow-up control examinations with a cardiologist and nephrologist.

Retroperitoneal fibrosis: retrospective descriptive study on clinical features and management

INTRODUCTION

Retroperitoneal fibrosis (RPF) is a rare condition characterized by the presence of inflammatory and fibrous retroperitoneal tissue that often encases the ureters or abdominal organs. This study describes the clinical characteristics, diagnostic methods, and treatments and their effects on renal function.

METHODS

We conducted a retrospective analysis of patients diagnosed with RPF at Maisonneuve-Rosemont Hospital.

RESULTS

We identified 17 patients with RPF between 1998 and 2013. Eight patients were females (47%), and the mean age was 62±18 years. Eleven patients were idiopathic. Back pain was the most common symptom. All diagnoses were made based on the finding of a retroperitoneal mass on the computed tomography scan. Three patients had histological diagnosis of RPF and seven patients had unspecific changes on their biopsy. Twelve patients needed double-J stents, three patients had a temporary percutaneous nephrostomy, two patients had to have a nephrectomy for refractory ureteral obstruction, and one patient required hemodialysis. Ten patients with idiopathic RPF received medical treatment. In the treated group, only two patients had complete remission of the disease and five patients had improvement of their lesions. There were no deteriorations and only one relapse. Seven patients did not receive any treatment; two of them achieved complete remission, one of them deteriorated, and two of them had no changes.

CONCLUSION

Most of our cases of RPF were idiopathic. Almost all treated patients received prednisone and seemed to respond, at least partially. There was a lot of heterogeneity in patient management, which makes it difficult to compare treatment effects. However, treated patients seemed to have more favorable outcomes than those who were not.

Chronic, nonspecific, postinfectious, retroperitoneal fibrosis and ureteral obstruction

INTRODUCTION

Two cases of severe ureteral obstruction following nonspecific, postinfectious, chronic retroperitoneal fibrosis are described, which both originated by a primitive intestinal pathology.

PATIENTS

This complication was observed in two women: first, 65 years old, submitted for ulcerative colitis to a total proctocolectomy, with ileo-pouch-anal anastomosis, complicated by an anastomotic fistula; and second, 66 years old, operated with an extended left hemicolectomy, for an adenocarcinoma of the recto-sigmoid colon complicated with a vaginal fistula. In these cases, computerized tomography demonstrated a unilateral hydronephrosis, secondary to a complete obstruction of the ureter; a subsequent nephro-ureterectomy became necessary. Histology demonstrated nonspecific inflammatory lesions.

DISCUSSIONS

Postinfectious, chronic inflammation of the retroperitoneum acts on the ureteral and peri-ureteral tissues, inducing an inflammatory and then a fibrotic process.

CONCLUSIONS

We underline the opportunity of a precocious and radical treatment of every retroperitoneal infection.

Three-dimensional segmentation of retroperitoneal masses using continuous convex relaxation and accumulated gradient distance for radiotherapy planning

An innovative algorithm has been developed for the segmentation of retroperitoneal tumors in 3D radiological images. This algorithm makes it possible for radiation oncologists and surgeons semiautomatically to select tumors for possible future radiation treatment and surgery. It is based on continuous convex relaxation methodology, the main novelty being the introduction of accumulated gradient distance, with intensity and gradient information being incorporated into the segmentation process. The algorithm was used to segment 26 CT image volumes. The results were compared with manual contouring of the same tumors. The proposed algorithm achieved 90 % sensitivity, 100 % specificity and 84 % positive predictive value, obtaining a mean distance to the closest point of 3.20 pixels. The algorithm's dependence on the initial manual contour was also analyzed, with results showing that the algorithm substantially reduced the variability of the manual segmentation carried out by different specialists. The algorithm was also compared with four benchmark algorithms (thresholding, edge-based level-set, region-based level-set and continuous max-flow with two labels). To the best of our knowledge, this is the first time the segmentation of retroperitoneal tumors for radiotherapy planning has been addressed.

Primary retroperitoneal masses: what is the differential diagnosis?

Primary retroperitoneal masses include a diverse, and often rare, group of neoplastic and non-neoplastic entities that arise within the retroperitoneum but do not originate from any retroperitoneal organ. Their overlapping appearances on cross-sectional imaging may pose a diagnostic challenge to the radiologist; familiarity with characteristic imaging features, together with relevant clinical information, helps to narrow the differential diagnosis. In this article, a systematic approach to identifying and classifying primary retroperitoneal masses is described. The normal anatomy of the retroperitoneum is reviewed with an emphasis on fascial planes, retroperitoneal compartments, and their contents using cross-sectional imaging. Specific radiologic signs to accurately identify an intra-abdominal mass as primary retroperitoneal are presented, first by confirming the location as retroperitoneal and secondly by excluding an organ of origin. A differential diagnosis based on a predominantly solid or cystic appearance, including neoplastic and non-neoplastic entities, is elaborated. Finally, key diagnostic clues based on characteristic imaging findings are described, which help to narrow the differential diagnosis. This article provides a comprehensive overview of the cross-sectional imaging features of primary retroperitoneal masses, including normal retroperitoneal anatomy, radiologic signs of retroperitoneal masses and the differential diagnosis of solid and cystic, neoplastic and non-neoplastic retroperitoneal masses, with a view to assist the radiologist in narrowing the differential diagnosis.

A comprehensive review of the retroperitoneal anatomy, neoplasms, and pattern of disease spread

A clear understanding of the normal anatomy and pattern of disease spread is important in evaluating many retroperitoneal disorders. Primary retroperitoneal tumors are uncommon, accounting for 0.1%-0.2% of all malignancies in the body; 80%-90% of all primary retroperitoneal tumors are malignant. The primary retroperitoneal neoplasms can be divided into solid or cystic masses. The solid neoplasms can be classified according to their tissue of origin into 3 main categories: mesodermal tumors, neurogenic tumors, and extragonadal germ cell tumors. Computed tomography and magnetic resonance imaging play a vital role in the localization, characterization, evaluation of the extent of local invasion, assessment of metastases, and determination of treatment response for these tumors. The diagnosis of a primary retroperitoneal malignancy is often challenging owing to overlap of imaging findings. A definitive diagnosis can be established only at histopathologic analysis. However, knowledge of the important tumor characteristics, growth pattern, and vascularity can assist in narrowing the differential diagnosis.

Anatomic connections of the diaphragm: influence of respiration on the body system

The article explains the scientific reasons for the diaphragm muscle being an important crossroads for information involving the entire body. The diaphragm muscle extends from the trigeminal system to the pelvic floor, passing from the thoracic diaphragm to the floor of the mouth. Like many structures in the human body, the diaphragm muscle has more than one function, and has links throughout the body, and provides the network necessary for breathing. To assess and treat this muscle effectively, it is necessary to be aware of its anatomic, fascial, and neurologic complexity in the control of breathing. The patient is never a symptom localized, but a system that adapts to a corporeal dysfunction.

Adrenal imaging: a primer for oncosurgeons

Differentiation of an incidental adrenal lesion into benign and malignant etiologies is an endeavor with significant and obvious clinical benefit. Advances in imaging now enable this differentiation in high proportion of patients in a non-invasive manner. The ACR guidelines elaborated in this review seek to promote clinically meaningful, evidence-based approach to an IAL. Knowledge of the potential as well the limitations of individual modalities is essential so as to streamline investigations in a cost-effective manner.