[A case of retroperitoneal capillary malformation examined by contrast-enhanced ultrasonography with perfluorobutane (Sonazoid®)].

A man in his 60s with hyperamylasemia underwent contrast-enhanced computed tomography, which revealed masses in his pelvic cavity on the right side and in the left axilla. Hence, a detailed examination was performed. Upon performing Sonazoid® (perfluorobutane) contrast-enhanced ultrasound, it was discovered that the right-sided pelvic cavity mass exhibited centripetal contrast-enhancement right from the early stage. Subsequently, the contrast material disappeared from the center and was washed out in the postvascular phase. The mass was suspected to be caused by vascular malformations. The right-sided pelvic cavity mass was excised, and upon histopathological examination, it was detected to be composed of capillary malformations. Thus, it was found that Sonazoid® contrast-enhanced ultrasound examination could aid in diagnosing retroperitoneal masses.

Retroperitoneum revisited: a review of radiological literature and updated concept of retroperitoneal fascial anatomy with imaging features and correlating anatomy.

PURPOSE: Spread of disease in the retroperitoneum is dictated by the complex anatomy of retroperitoneal fasciae and is still incompletely understood. Conflicting reports have led to insufficient and incorrect anatomical concepts in radiological literature. METHODS: This review will discuss previous concepts prevalent in radiological literature and their shortcomings will be highlighted. New insights from recent anatomical and embryological research, together with imaging examples, will be used to clarify patterns of disease spread in the retroperitoneum that remain unexplained by these concepts. RESULTS: The fusion fascia and the renal fascia in particular give rise to planes and spaces that act as vectors for spread of disease in the retroperitoneum. Some of these planes and structures, such as the caudal extension of the renal fascia, have previously not been described in radiological literature. CONCLUSION: New insights, including the various fasciae, potential spaces and planes, are incorporated into an updated combined retroperitoneal fascial concept.

Imaging Diagnosis of Retroperitoneal Müllerian Duct-derived Cyst Complicated by Diaphragmatic Hernia: A Case Report.

BACKGROUND: This case report describes a case of Müllerian duct cyst that occurred in a male retroperitoneum. The cyst lesion is rare and complicated with diaphragmatic hernia. Müllerian duct-derived cyst is a rare developmental disorder that is more common in male pelvic tissues and rare in the retroperitoneum. We investigated the important role of computerized tomography (CT) and magnetic resonance imaging (MRI) in preoperative diagnosis and disease prediction of this condition. CASE PRESENTATION: A 25-year-old male was found to have an abnormal occupying lesion in the left diaphragm in imaging examinations, usually healthy with no obvious clinical symptoms. X-ray examination showed a circular, high-density shadow near the left diaphragm. CT scan showed a soft tissue density shadow resembling a tumor in the left adrenal area, irregularly protruding into the chest cavity, with uneven density. MRI examination showed an irregular elongated T1 and T2 signal shadow in the left adrenal area. T2 fat suppression showed high signal intensity with unrestricted diffusion. Robotic-assisted laparoscopic surgery showed left retroperitoneal tumor resection. The patient recovered well postoperatively and had no recurrence after discharge follow-up. CONCLUSION: The preclinical symptoms of retroperitoneal Müllerian cysts complicated by diaphragmatic hernia in young men are difficult to distinguish, and it is difficult to diagnose other similar cysts with imaging. The method of combined CT and MRI diagnosis guides the endoscopic robot-assisted minimally invasive surgery for excision of cysts to achieve accurate diagnosis and treatment of such diseases.

Overview of F18-FDG uptake patterns in retroperitoneal pathologies: imaging findings, pitfalls, and artifacts.

INTRODUCTION: Retroperitoneum can be the origin of a wide variety of pathologic conditions and potential space for disease spread to other compartments of the abdomen and pelvis. Computed tomography (CT) and magnetic resonance imaging (MRI) are often the initial imaging modalities to evaluate the retroperitoneal pathologies, however given the intrinsic limitations, F18-FDG PET/CT provides additional valuable metabolic information which can change the patient management and clinical outcomes. We highlight the features of retroperitoneal pathologies on F18-FDG PET/CT and the commonly encountered imaging artifacts and pitfalls. The aim of this review is to characterize primary and secondary retroperitoneal pathologies based on their metabolic features, and correlate PET findings with anatomic imaging. CONCLUSION: Retroperitoneal pathologies can be complex, ranging from oncologic to a spectrum of non-oncologic disorders. While crosse-sectional imaging (CT and MRI) are often the initial imaging modalities to localize and characterize pathologies, metabolic information provided by F18-FDG PET/CT can change the management and clinical outcome in many cases.

Diagnosis of an epidermoid retroperitoneal cyst via ultrasound: A case report.

Retroperitoneal cysts (RPCs) are rare types of cyst in the retroperitoneal space that are frequently misdiagnosed as gynecological tumors. This case report details, an epidermoid RPC, identified through 2D ultrasound, with attempts to visualize its rendered images using 3D ultrasound. A 39-year-old female patient was admitted to the hospital following the detection of a pelvic mass during a routine physical examination. Initially, the lesion was suspected to be an ovarian tumor, but subsequent ultrasound investigations suggested an epidermoid RPC. This diagnosis was later confirmed by pelvic magnetic resonance imaging. The definitive diagnosis was made following laparoscopic exploration and pathological examination. This case is shared to analyze the ultrasound characteristics of epidermoid RPCs.

A prospective case series to evaluate subcostal nerve injury with high-resolution ultrasound in posterior retroperitoneoscopic adrenalectomy.

BACKGROUND: Posterior retroperitoneoscopic adrenalectomy has several advantages over transabdominal laparoscopic adrenalectomy regarding operating time, blood loss, postoperative pain, and recovery. However, postoperatively several patients report chronic pain or hypoesthesia. We hypothesized that these symptoms may be the result of damage to the subcostal nerve, because it passes the surgical area. METHODS: A prospective single-center case series was performed in adult patients without preoperative pain or numbness of the abdominal wall who underwent unilateral posterior retroperitoneoscopic adrenalectomy. Patients received pre- and postoperative questionnaires and a high-resolution ultrasound scan of the subcostal nerve and abdominal wall muscles was performed before and directly after surgery. Clinical evaluation at 6 weeks was performed with repeat questionnaires, physical examination, and high-resolution ultrasound. Long-term recovery was evaluated with questionnaires, and photographs from the patients were examined for abdominal wall asymmetry. RESULTS: A total of 25 patients were included in the study. There were no surgical complications. Preoperative visualization of the subcostal nerve was possible in all patients. At 6 weeks, ultrasound showed nerve damage in 15 patients, with no significant association between nerve damage and postsurgical pain. However, there was a significant association between nerve damage and hypoesthesia (p = 0.01), sensory (p < 0.001), and motor (p < 0.001) dysfunction on physical examination. After a median follow-up of 18 months, 5 patients still experienced either numbness or muscle weakness, and one patient experienced chronic postsurgical pain. CONCLUSION: In this exporatory case series the incidence of postoperative damage to the subcostal nerve, both clinically and radiologically, was 60% after posterior retroperitoneoscopic adrenalectomy. There was no association with pain, and the spontaneous recovery rate was high.

A Machine Learning Model to Predict the Histology of Retroperitoneal Lymph Node Dissection Specimens.

BACKGROUND/AIM: While post-chemotherapy retroperitoneal lymph node dissection (PC-RPLND) benefits patients with teratoma or viable germ cell tumors (GCT), it becomes overtreatment if necrosis is detected in PC-RPLND specimens. Serum microRNA-371a-3p correctly predicts residual viable GCT with 100% sensitivity; however, prediction of residual teratoma in PC-RPLND specimens using current modalities remains difficult. Therefore, we developed a machine learning model using CT imaging and clinical variables to predict the presence of residual teratoma in PC-RPLND specimens. PATIENTS AND METHODS: This study included 58 patients who underwent PC-RPLND between 2005 and 2019 at the University of Tsukuba Hospital. On CT imaging, 155 lymph nodes were identified as regions of interest (ROIs). The ResNet50 algorithm and/or Support Vector Machine (SVM) classification were applied and a nested, 3-fold cross-validation protocol was used to determine classifier accuracy. RESULTS: PC-RPLND specimen analysis revealed 35 patients with necrosis and 23 patients with residual teratoma, while histology of 155 total ROIs showed necrosis in 84 ROIs and teratoma in 71 ROIs. The ResNet50 algorithm, using CT imaging, achieved a diagnostic accuracy of 80.0%, corresponding to a sensitivity of 67.3%, a specificity of 90.5%, and an AUC of 0.84, whereas SVM classification using clinical variables achieved a diagnostic accuracy of 74.8%, corresponding to a sensitivity of 59.0%, a specificity of 88.1%, and an AUC of 0.84. CONCLUSION: Our machine learning models reliably distinguish between necrosis and residual teratoma in clinical PC-RPLND specimens.

Testicular Radiomics To Predict Pathology At Time of Postchemotherapy Retroperitoneal Lymph Node Dissection for Nonseminomatous Germ Cell Tumor.

INTRODUCTION: Testicular germ cell tumors are the most common malignancy in young adult males. Patients with metastatic disease receive standard of care chemotherapy followed by retroperitoneal lymph node dissection for residual masses >1cm. However, there is a need for better preoperative tools to discern which patients will have persistent disease after chemotherapy given low rates of metastatic germ cell tumor after chemotherapy. The purpose of this study was to use radiomics to predict which patients would have viable germ cell tumor or teratoma after chemotherapy at time of retroperitoneal lymph node dissection. PATIENTS AND METHODS: Patients with nonseminomatous germ cell tumor undergoing postchemotherapy retroperitoneal lymph node dissection (PC-RPLND) between 2008 and 2019 were queried from our institutional database. Patients were included if prechemotherapy computed tomography (CT) scan and postchemotherapy imaging were available. Semiqualitative and quantitative features of residual masses and nodal regions of interest and radiomic feature extractions were performed by 2 board certified radiologists. Radiomic feature analysis was used to extract first order, shape, and second order statistics from each region of interest. Post-RPLND pathology was compared to the radiomic analysis using multiple t-tests. RESULTS: 45 patients underwent PC-RPLND at our institution, with the majority (28 patients) having stage III disease. 24 (53%) patients had teratoma on RPLND pathology, while 2 (4%) had viable germ cell tumor. After chemotherapy, 78%, 53%, and 33% of patients had cystic regions, fat stranding, and local infiltration present on imaging. After radiomic analysis, first order statistics mean, median, 90th percentile, and root mean squares were significant. Strong correlations were observed between these 4 features;a lower signal was associated with positive pathology at RPND. CONCLUSIONS: Testicular radiomics is an emerging tool that may help predict persistent disease after chemotherapy.

Spontaneous retroperitoneal haematoma in severe dengue: A case report.

Dengue is endemic in over 100 countries worldwide, predominantly in the subtropical and tropical regions and the incidence has been increasing globally. Patients with severe dengue may develop massive bleeding, disseminated intravascular coagulopathy and multi-organ failure. Bleeding may occur in various body cavities and muscles; however, bleeding in the retroperitoneal space is uncommon. We report a case of a 37-year-old gentleman who presented with a 4-day history of fever associated with chills and rigours. On Day 6 of illness, he complained of left lumbar and left iliac fossa pain which was aggravated by movement. A computed tomography angiography scan of the abdomen showed the presence of a retroperitoneal haematoma, left iliopsoas and quadratus lumbarum intramuscular haematoma with active bleeding and left abdominal wall muscles haematoma. His condition gradually improved after multiple blood transfusions and he gained full recovery. Spontaneous retroperitoneal haematoma is an uncommon complication of severe dengue infection. Early diagnosis based on high index of clinical suspicion using appropriate imaging will aid in prompt management of these cases and may prevent deaths.

The anatomical positioning change of retroperitoneal organs in prone and lateral position: an assessment for single-prone position lateral lumbar surgery.

PURPOSE: There are reports that performing lateral lumbar interbody fusion (LLIF) in a prone, single position (single-prone LLIF) can be done safely in the prone position because the retroperitoneal organs reflect anteriorly with gravity. However, only a few study has investigated the safety of single-prone LLIF and retroperitoneal organ positioning in the prone position. We aimed to investigate the positioning of retroperitoneal organs in the prone position and evaluate the safety of single-prone LLIF surgery. METHODS: A total of 94 patients were retrospectively reviewed. The anatomical positioning of the retroperitoneal organs was evaluated by CT in the preoperative supine and intraoperative prone position. The distances from the centre line of the intervertebral body to the organs including aorta, inferior vena cava, ascending and descending colons, and bilateral kidneys were measured for the lumbar spine. An "at risk" zone was defined as distance less than 10 mm anterior from the centre line of the intervertebral body. RESULTS: Compared to supine preoperative CTs, bilateral kidneys at the L2/3 level as well as the bilateral colons at the L3/4 level had statistically significant ventral shift with prone positioning. The proportion of retroperitoneal organs within the at-risk zone ranged from 29.6 to 88.6% in the prone position. CONCLUSIONS: The retroperitoneal organs shifted ventrally with prone positioning. However, the amount of shift was not large enough to avoid risk for organ injuries and substantial proportion of patients had organs within the cage insertion corridor. Careful preoperative planning is warranted when considering single-prone LLIF.

[Spontaneous retroperitoneal hemorrhage].

A 50-year old male presented to our emergency department with sudden abdominal pain. Upon arrival he was diaphoretic, pale and tachycardic. A CT showed retroperitoneal hemorrhage with suspected tumor at the left adrenal gland. He was quickly stabilized with intravenous fluids and blood transfusion. Rebleed occurs roughly a week after discharge and a new CT showed a visceral pseudoaneurysm from the left middle adrenal artery. The pseudoaneurysm was embolized and the patient discharged in good condition. Follow-up MRI depicted reabsorption of the hematoma and no adrenal tumor. Thus, the etiology of the previous retroperitonal hemorrhage is considered spontaneous.

Evaluation of Inflammatory Infiltration in the Retroperitoneal Space of Acute Pancreatitis Using Computer Tomography and Its Correlation with Clinical Severity.

This paper investigates the correlation between the degree and severity of CT inflammatory infiltration in the retroperitoneal space of acute pancreatitis (AP). A total of 113 patients were included based on diagnostic criteria. The general data of the patients and the relationship between the computed tomography severity index (CTSI) and pleural effusion (PE), involvement, degree of inflammatory infiltration of retroperitoneal space (RPS), number of peripancreatic effusion sites, and degree of pancreatic necrosis on contrast-enhanced CT at different times were studied. The results showed that the mean age of onset in females was later than that in males; 62 cases involved RPS to varying degrees, with a positive rate of 54.9% (62/113), and the total involvement rates of only the anterior pararenal space (APS); both APS and perirenal space (PS); and APS, PS, and posterior pararenal space (PPS) were 46.9% (53/113), 53.1% (60/113), and 17.7% (20/113), respectively. The degree of inflammatory infiltration in the RPS worsened with the increase in CTSI score; the incidence of PE was higher in the group greater than 48 hours than in the group less than 48 hours; necrosis >50% grade was predominant (43.2%) 5 to 6 days after onset, with a higher detection rate than other time periods (P < 0.05). Thus, when the PPS was involved, the patient's condition can be treated as severe acute pancreatitis (SAP); the higher the degree of inflammatory infiltration in the retroperitoneum, the higher the severity of AP. Enhanced CT examination 5 to 6 days after onset in patients with AP revealed the greatest extent of pancreatic necrosis.

German specialists treating testicular cancer follow different guidelines with resulting inconsistency in assessment of retroperitoneal lymph-node metastasis: clinical implications and possible corrective measures.

BACKGROUND: Testicular germ cell tumors (GCTs) are aggressive but highly curable tumors. To avoid over/undertreatment, reliable clinical staging of retroperitoneal lymph-node metastasis is necessary. Current clinical guidelines, in their different versions, lack specific recommendations on how to measure lymph-node metastasis. OBJECTIVE: We aimed to assess the practice patterns of German institutions frequently treating testicular cancer for measuring retroperitoneal lymph-node size. METHODS: An 8-item survey was distributed among German university hospitals and members of the German Testicular Cancer Study Group. RESULTS: In the group of urologists, 54.7% assessed retroperitoneal lymph nodes depending on their short-axis diameter (SAD) (33.3% in any plane, 21.4% in the axial plane), while 45.3% used long-axis diameter (LAD) for the assessment (42.9% in any plane, 2.4% in the axial plane). Moreover, the oncologists mainly assessed lymph-node size based on the SAD (71.4%). Specifically, 42.9% of oncologists assessed the SAD in any plane, while 28.5% measured this dimension in the axial plane. Only 28.6% of oncologists considered the LAD (14.3% in any plane, 14.3% in the axial plane). None of the oncologists and 11.9% of the urologists (n = 5) always performed an MRI for the initial assessment, while for follow-up imaging, the use increased to 36.5% of oncologists and 31% of urologists. Furthermore, only 17% of the urologists, and no oncologists, calculated lymph-node volume in their assessment (p = 0.224). CONCLUSION: Clear and consistent measurement instructions are urgently needed to be present in all guidelines across different specialistic fields involved in testicular cancer management.