RETROPERITONEAL MR IMAGING

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.

Primary malignant tumors of peritoneal and retroperitoneal origin: clinical and imaging features

Peritoneal carcinomatosis and metastatic involvement of the retroperitoneum are manifestations of many organ-based malignancies and lymphoproliferative disorders. Primary malignancies of peritoneal and retroperitoneal origin occur much less frequently, and are difficult to distinguish from metastatic disease on imaging alone. However, the imaging features of these primary tumors, taken in concert with the clinical data, can be helpful in narrowing the scope of the differential diagnosis. This review presents the clinical and imaging features of primary peritoneal and retroperitoneal tumors arising from the various tissue components that comprise the ligaments, mesenteries, and connective tissues of the peritoneal and retroperitoneal spaces.

Imaging of the retroperitoneum

The retroperitoneum is the compartmentalized space bounded anteriorly by the posterior parietal peritoneum and posteriorly by the transversalis fascia. It extends from the diaphragm superiorly to the pelvic brim inferiorly. This article discusses clinically relevant anatomy of the abdominal retroperitoneal spaces, their cross-sectional imaging evaluation with computed tomography and magnetic resonance imaging, and the imaging features of common retroperitoneal pathologic processes.

Ureteral obstruction due to retroperitoneal fibrosis secondary to a solitary internal iliac aneurysm

We report a case of ureteral obstruction due to retroperitoneal fibrosis secondary to a solitary left internal iliac aneurysm. It has been reported that as a cause of ureteral obstruction, an internal iliac aneurysm without aortic and/or common iliac aneurysms is very rare. In the present case, magnetic resonance imaging was a useful modality to diagnose retroperitoneal fibrosis secondary to an internal iliac aneurysm as a direct cause of ureteral obstruction.

Primary retroperitoneal neoplasms: CT and MR imaging findings with anatomic and pathologic diagnostic clues

Primary retroperitoneal neoplasms are a rare but diverse group of benign and malignant tumors that arise within the retroperitoneal space but outside the major organs in this space. Although computed tomography and magnetic resonance imaging can demonstrate important characteristics of these tumors, diagnosis is often challenging for radiologists. Diagnostic challenges include precise localization of the lesion, determination of the extent of invasion, and characterization of the specific pathologic type. The first step is to determine whether the tumor is located within the retroperitoneal space. Displacement of normal anatomic structures of the retroperitoneum is helpful in this regard. For tumors that are located within the retroperitoneum, the next step is to identify the organ of origin. Specific signs, including the "beak sign," the "embedded organ sign," and the "phantom (invisible) organ sign," are useful for this purpose. When there is no definite sign that suggests the organ of origin, the diagnosis of a primary retroperitoneal tumor becomes likely. Awareness of specific patterns of spread, specific tumor components, and tumor vascularity help in further narrowing the differential diagnosis. Attention to these diagnostic clues is essential in making an accurate radiologic diagnosis of primary retroperitoneal tumors and in obtaining clinically significant information.

Soft tissue carcinoma in the retroperitoneum: an often neglected diagnosis

AIMS

Successful surgical treatment of patients with retroperitoneal soft tissue sarcoma (RSTS) is based on pre-operative planning that starts with a correct pre-operative diagnosis. In a population-based study, we determined which patients were initially treated for assumed other conditions. The effect of an erroneous diagnosis on the installed treatment was analysed.

METHOD

With the help of the Dutch Network and National Database for Pathology (PALGA), data were collected on 143 patients in the Netherlands in whom a primary RSTS was found and confirmed histologically between 1 January 1989 and 1 January 1994. Satisfactory clinical information was obtained on 138 patients, 64 males and 74 females (54%). The median age was 60 (range 18-88) years.

RESULTS

At the time of actual treatment 37% of the patients with RSTS were assumed to have another disorder (group 1 n=51), whereas 87 patients were diagnosed as having RSTS (group 2). In group 1, an acute presentation was more common (18 vs 2% P=0.002), and the tumour was less often palpable at physical examination (43 vs 69% P=0.004), while clinical work-up less frequently included CT-imaging (57 vs 89% P<0.001) and a biopsy (29 vs 77% P<0.001). Although tumours in group 1 were smaller (median diameter 13 vs 19 cm P<0.05), this was not reflected in a better operative result: less patients underwent complete tumour resection (51 vs 57%) and more patients underwent surgery for tumours that proved to be irresectable (14 vs 1% P=0.004).

CONCLUSIONS

(1) More than one-third of patients with RSTS are misdiagnosed and inappropriately treated; and (2) biopsies and cross-sectional imaging improve diagnosis.

Laparoscopic treatment of retroperitoneal fibrosis: report of two cases and review of the literature

OBJECTIVES

We present the results of treatment by laparoscopy of two patients with retroperitoneal fibrosis and review the literature since 1992, when the first case of this disease that was treated using laparoscopy was published. We also discuss the contemporary alternatives of clinical treatment with corticosteroids and tamoxifen.

CASE REPORT

Two female patients, one with idiopathic retroperitoneal fibrosis, and other with retroperitoneal fibrosis associated with Riedel's thyroiditis, were treated using laparoscopic surgery. Both cases had bilateral pelvic ureteral obstruction and were treated using the same technique: transperitoneal laparoscopy, medial mobilization of both colons, liberation of both ureters from the fibrosis, and intraperitonealisation of the ureters. Double-J catheters were inserted before the operations and removed 3 weeks after the procedures. The first patient underwent intraperitonealisation of both ureters in a single procedure. The other had 2 different surgical procedures because of technical difficulties during the first operation. Both patients were followed for more than 1 year and recovered completely from the renal insufficiency. One of them still has occasional vague lumbar pain. There were no abnormalities in the intravenous pyelography in either case.

CONCLUSIONS

Surgical correction of retroperitoneal fibrosis, when indicated, should be attempted using laparoscopy. If possible, bilateral ureterolysis and intraperitonealisation of both ureters should be performed in the same operation.