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 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.

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.

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.

Review of diagnosis, differential diagnosis, and management of retroperitoneal lymphangioma.

Lymphatic malformation (LM) is the currently preferred term for what was previously known as lymphangioma. Retroperitoneal LMs are extremely rare, benign, cystic masses that arise from lymphatic vessels. They can be challenging to diagnose because they resemble other retroperitoneal cystic tumors. The development of treatment strategies for rare diseases, including retroperitoneal LM, requires the acquisition of new knowledge to enhance our understanding of the disease progression. Therefore, we present an update regarding fundamental and advanced issues associated with retroperitoneal LM. This review describes the epidemiology, histopathology, biomedicine, clinical manifestations, radiological features, differential diagnosis, and management of this lesion.

Multidisciplinary treatment of retroperitoneal ectopic pregnancy: a case report and literature review.

BACKGROUND: Retroperitoneal ectopic pregnancy (REP) is an extremely rare type of ectopic pregnancy, with a total of less than 32 cases reported in the English literature. Early diagnosis of REP is very difficult and all treatments entail a high risk of life-threatening complications. CASE PRESENTATION: A 29-year-old nulliparous woman presented a history of 50-day amenorrhea and 7-day upper abdominal pain without vaginal spotting. The serum beta-human chorionic gonadotropin (ß-hCG) value was 65,004 m-international units per milliliter (mIU/mL), but no intrauterine gestational sac was found via transvaginal sonography (TVS). Then transabdominal ultrasonography (TAS) and abdominal contrast-enhanced computer tomography (CT) identified a retroperitoneal ectopic pregnancy (REP) tightly adjacent to the inferior vena cava and the abdominal aorta. After consultation from a multidisciplinary team, systemic methotrexate (MTX, intramuscular 20 mg daily for 5 consecutive days) combined with ultrasound-guided local potassium chloride solution injection into the gestational sac was scheduled firstly for the patient. However, serum ß-hCG continued to increase and the patient experienced worsening abdominal pain. Laparotomy was performed jointly by a gynecologist and a vascular surgeon. During the operation, the gestational sac with fetal bud measuring about 4.5 × 4.0x3.0 cm, tightly adherent to the surface of inferior vena cava and the left side of abdominal aorta, was carefully dissociated out from the surrounding tissues and removed en bloc. Histopathology examination confirmed the diagnosis of REP. The patient recovered uneventfully and her serum ß-hCG returned to normal range on the 23th postoperative day. CONCLUSIONS: Considering the possibility of REP and combined radiological examinations, such as ultrasonography and CT, are crucial for the early diagnosis of this rare condition. A multidisciplinary team is necessary to treat REP.

Primary retroperitoneal hydatid cyst with intraperitoneal rupture: a case report.

BACKGROUND: Hydatid disease is endemic in Mediterranean countries and most commonly occurs in the liver followed by the lung. A primary localization in the retroperitoneum is extremely rare. CASE PRESENTATION: We report the case of a 29-year-old Tunisian patient presenting with progressive left flank pain and skin urticaria. On abdominal ultrasonography and computed tomography scan, a ruptured retroperitoneal hydatid cyst was diagnosed, which was confirmed by positive hydatid serology. The treatment consisted of resection of protruding dome. The evolution was favorable. No local recurrence was detected during postoperative follow-up. CONCLUSIONS: Primary retroperitoneal hydatid cyst is extremely rare and has uncommon presentation, but we should learn the keys to its diagnosis. In endemic regions, high suspicion for this disease is justified regardless of localization.

Giant pseudocyst of the retroperitoneal space mimicking a lesion arising from the left adrenal gland.

Not required for Clinical Vignette.

Imaging findings of retroperitoneal anastomosing hemangioma: a case report and literature review.

BACKGROUND: Anastomosing hemangioma is an uncommon benign vascular tumor that may be mistaken for a malignancy. The imaging findings of anastomosing hemangioma are not well provided from the previous reports. Herein, in the study, we discuss the imaging findings for one case of retroperitoneal anastomosing hemangioma. CASE PRESENTATION: One 64-year-old female patient had a left retroperitoneal mass that was incidentally detected upon physical examination. A hypoechoic mass with abundant blood flow signals was found by US in the perirenal space. CT and MRI detected a large cystic and solid lesion in the left retroperitoneal space. Plain CT indicated that the internal density was uneven, and the pattern of enhancement was obvious and progressive. MRI-T2WI showed high intensity, DWI showed isointensity, and the mass also showed obvious progressive enhancement. Finally, anastomosing hemangioma was diagnosed via histopathological studies. CONCLUSION: As a rare and benign tumour, anastomosing hemangioma is easily misinterpreted. We suggest that the observation of "genitourinary tract related, well defined, hyperintensity or isointensity on T2WI, isointensity on DWI, and obvious progressive enhancement patterns likely to the vascular enhancement" may consider the diagnosis of AH.

[A Case of Retroperitoneal Bronchogenic Cyst].

A 75-year-old male visited a clinic with the chief complaint of pollakiuria. A computed tomography scan revealed, a left adrenal mass, and the patient was then referred to our hospital. Since a malignant tumor could not be ruled out. We performed laparoscopic left adrenal resection. Postoperative histopathological findings revealed the mass to be a bronchogenic cyst, which had no continuity with the normal adrenal gland. The postoperative course was uneventful, and recurrence has not been observed. Retroperitoneal bronchogenic cysts are rare and often difficult to diagnose preoperatively using imaging studies.

Intravascular Ultrasound for the Evaluation and Management of Retroperitoneal, Genitourinary Malignancies.

PURPOSE OF REVIEW: Herein we provide a review of intravascular ultrasound (IVUS) and its ability to assist in the evaluation and surgical management of advanced retroperitoneal, genitourinary tumors. RECENT FINDINGS: Advanced retroperitoneal tumors such as advanced renal cell carcinoma, bulky retroperitoneal lymphadenopathy associated with advanced testicular carcinoma, large adrenal tumors, and retroperitoneal sarcomas can invade, compress, or distort vascular anatomy making surgical resection challenging and high risk. Intravascular ultrasonography is commonly used by vascular and cardiothoracic surgery to provide a real time assessment of vascular invasion, compression, and aberrant anatomy to assist with pre-operative and/or intraoperative decision-making. However, the application of this technology to assist with cancer surgery has been limited. The use of intravascular ultrasound prior to radical, extirpative, retroperitoneal surgery involving large vessels can aid in the planning and execution of such challenging operations.

Surgical Repair of a Ruptured Giant Abdominal Aortic Aneurysm in a 16-Year-Old with Takayasu's Arteritis: Case Report and Etiological Review

Abstract Takayasu's arteritis is a type of primary systemic vasculitis that affects medium and large arteries, including the aorta and its main branches, as well as the pulmonary and coronary arteries. Although rare in children, it is the third most common vasculitis in the pediatric population, often with delayed diagnosis due to the nonspecific presentation of clinical symptoms in its initial phase. This is a case of a 16-year-old girl with a giant ruptured abdominal aortic aneurysm, who needed surgery on an emergency basis. The etiological aspects involved in aneurysms in young patients are also addressed.

An asymptomatic huge primary retroperitoneal pseudocyst: a case report and review of the literature.

BACKGROUND: Retroperitoneal non-pancreatic or idiopathic pseudocysts are very rare lesions. This case report aimed to present our patient and to check all the available literature on this kind of rare disease. CASE PRESENTATION: Our patient was a 67-year-old Iranian man admitted with mild abdominal discomfort for three months. Ultrasonography and CT scan revealed a huge cystic structure within the retroperitoneal space. The lesion was excised through midline laparotomy and opening of the retro-peritoneum. The histopathology of the cyst wall revealed a benign cystic lesion with no epithelial lining. A histologic diagnosis of non-neoplastic retroperitoneal pseudocyst was made. CONCLUSION: The primary non-pancreatic retroperitoneal pseudocysts are rare lesions and have to be distinguished from other differential diagnoses of retroperitoneal lesions, and a surgeon should be aware of the possible occurrence of these lesions with unknown origin. Surgical excision is the only way to exclude malignancy and confirm the diagnosis.

[A Case of Retroperitoneal Bronchogenic Cyst Diagnosed by Fluorescence in situ Hybridization].

A 50-year-old woman was referred to our hospital for consultation for a suspected left adrenal tumor detected by ultrasonography during a health check. Computed tomography and magnetic resonance imaging revealed a 4.7×3.4 cm tumor in the retroperitoneal space near the adrenal gland. The patient subsequently underwent laparoscopic tumor resection. Using fluorescence in situ hybridization (FISH), the resected tumor was diagnosed as a retroperitoneal bronchial cyst. Here we present a case of a definitive diagnosis of a retroperitoneal bronchial cyst using FISH, and review the cases of retroperitoneal bronchial cyst in the literature.

A retroperitoneal bronchogenic cyst clinically mimicking an adrenal mass: three case reports and a literature review.

Bronchogenic cysts are a congenital primitive foregut-derived developmental malformation, generally occurring in the posterior mediastinum. Their development in the retroperitoneum is extremely rare. Imaging techniques, such as multidetector computed tomography (MDCT), are typically effective in the detection of these lesions. Here, we describe three cases of a retroperitoneal cyst presenting as a para-adrenal mass. Only one boy presented with abdominal pain, and the other two showed no clinical symptoms. Endocrinological evaluation of all three cases was performed, and no adrenal hormone secretion was detected. All three cases were misdiagnosed preoperatively. Each patient underwent surgery, and one symptomatic patient became asymptomatic after surgery. Pathologic examination confirmed all three masses as bronchogenic cysts. The three cases showed some similar MDCT imaging features, including a complete adrenal structure, a cystic or solid mass in the adrenal region, and no obvious enhancement. Therefore, bronchogenic cysts should be considered in the differential diagnosis of retroperitoneal masses, even though accurate preoperative diagnosis remains difficult. A contrast-enhanced MDCT scan may be useful for differentiating hyper-attenuated cysts from other soft tissue masses.