Type:
Educational Exhibit
Keywords:
CT, MR, Localisation, Diagnostic procedure, Neoplasia, Retroperitoneum
Authors:
E. Gonzalez Montpetit1, R. Expósito Díaz1, J. A. Gonzalez-Nieto1, A. PAINEL SEGUEL2, J. vizuete del rio1, J. Salvador García1; 1Valencia/ES, 2Valencia, Comunidad Valenciana/ES
DOI:
10.1594/ecr2018/C-2310
Background
Retroperitoneal masses are rare but constitute a significant and broad group of neoplasms.
Up to 70-80% of retroperitoneal masses are malignant,
although they only represent 0.1% of all malignancies in the body.
Therefore,
they are infrequent lesions in the daily practice,
and their differential diagnosis may be challenging.
A resolutive radiological study avoids the need for more invasive diagnostic tests,
although histological confirmation is often required for definitive diagnosis due to the considerable overlap of imaging features.
ANATOMY OF THE RETROPERITONEUM
Getting familiar with the anatomy of the retroperitoneum and recognizing its boundaries is essential to identify lesions within this space and be able to understand the different spreading patterns of retroperitoneal lesions.
The retroperitoneum is an extraperitoneal space lying between the posterior parietal peritoneum anteriorly and the transversalis fascia posteriorly.
The upper and lower limits are worse defined,
unlike the anterior and posterior margins which are marked by bands of connective tissue.
It extends in the abdomen from the underside of the diaphragm superiorly,
being in communication with the posterior mediastinum.
Inferiorly,
it communicates with the extraperitoneal space in the pelvis.
The retroperitoneal space is classically divided into three main compartments (Fig. 2).
-
Anterior pararenal space: It is the most anterior compartment of the retroperitoneum.
It lies right posterior to the peritoneal cavity from which the posterior parietal peritoneum separates it.
Its posterior limit is the anterior renal fascia or Gerota's fascia,
and its lateral boundary is the laterconal fascia or Sappey's fascia.
-
Posterior pararenal space: Unlike the rest of the retroperitoneal compartments,
the posterior pararenal space is characterized by not containing any organs,
but only fat.
It is located between the posterior renal fascia or Zuckerkandl’s fascia and the lateroconal fascia anteriorly,
and the transversalis fascia posteriorly.
-
Perirenal space: It is the largest of the three retroperitoneal compartments.
It is separated from the anterior pararenal space by the anterior renal fascia or Gerota’s fascia and the posterior pararenal space by the posterior renal fascia.
Kidneys,
renal vessels and proximal collecting system,
adrenal glands and perirenal fat are included in this compartment.
The perirenal fat is crossed by small septa,
known as Kunin’ septa and subdivided into multiple small compartments.
This traditional division has been questioned as it fails at fully explaining the growing patterns and ways of dissemination of retroperitoneal lesions.
The most recent revisions consider the perirenal fascias as multilayered connective-tissue bands with virtual,
potentially expandable interfascial spaces.
Most retroperitoneal lesions arise from major solid organs contained in the different compartments of the retroperitoneum (kidneys,
adrenal glands,
pancreas,
duodenum,
ascending and descending colon,
lymphatic structures) (Fig. 3).
Those lesions are considered secondary processes,
while primary lesions are those which originate in the retroperitoneum,
outside the main organs.
The purpose of this work focuses on primary as well as secondary retroperitoneal masses that present an infiltrative growth pattern explaining their main characteristics and the most distinctive radiological findings (Table 1).