Radiological diagnosis of perinephric pathology: pictorial essay 2015

Abstract

The perinephric space, shaped as an inverted cone, sits between the anterior and posterior renal fasciae. It can play host to a variety of clinical conditions encountered daily in the reporting schedule for a radiologist. Lesions may be classified and diagnosed based on their imaging characteristics, location and distribution. A broad range of differential diagnoses can be attributed to pathology sitting within this space, often without clinical signs or symptoms. An understanding of commonly encountered conditions affecting the perinephric space, along with characteristic imaging findings, can illustrate and often narrow the likely diagnosis. The aim of this essay is to describe commonly encountered neoplastic and non-neoplastic entities involving the perinephric space and to describe their key imaging characteristics.

Teaching point: • Despite often a bulky disease, perinephric lymphoma does not produce obstruction or stenosis. • In primarily fatty masses, defects within the renal capsule likely represent angiomyolipoma. • Consider paraganglioma if biopsy is planned; biopsy may lead to catecholamine crisis.

Keywords: Kidney; Magnetic resonance imaging; Neoplasms, connective and soft tissue; Perinephric space; Tomography, spiral computed.

Fig. 1

Diagrammatic representation of the perinephric space. The posterior pararenal space (PPS) and anterior pararenal space (APS) have been exaggerated to provide representation of their relation to other retroperitoneal structures. Perinephric bridging septa are seen between the left kidney and the adjacent renal fascia

Fig. 2

Lateral longitudinal representation of the perinephric space. The adrenal gland lies within the perinephric space, superior to the kidney. The anterior renal fascia and posterior renal fascia join inferiorly into the pelvis as the combined inter-fascial plane

Fig. 3

Conal portal venous CT shows gas in the perinephric space (arrowhead), demonstrating its longitudinal conal orientation and that it contains both the kidney and the adrenal (arrow). The gas was secondary to a perforation during colonoscopy

Fig. 4

a Acute left-sided haematoma that is isodense to muscle (arrow), displacing the kidney anteriorly (star). b The portal venous phase shows active bleeding (arrows) into the haematoma. The bleed was secondary to an ultrasound-guided biopsy

Fig. 5

Delayed-phase CT in a patient with calyceal rupture following lithotripsy shows fluid in the perinephric space (arrow) and extravasation of contrast (arrowhead) in keeping with active urine leak

Fig. 6

Delayed-phase CT shows fluid filling the right perinephric space in a patient following blunt trauma. The kidney has been lacerated (short arrow), and urinary contrast extravasation is shown posteriorly (long arrow)

Fig. 7

A delayed-phase CT shows a left renal pelvis with extravasation of urine anterior to it (arrow). Note the unopacified urine in the perinephric space (arrowheads)

Fig. 8

a A well-defined and fluid attenuation homogeneous cystic lymphangioma in the left perirenal space (arrow), with no capsule and no evidence of mass effect on the adjacent kidney. b A T2-weighted MRI shows the fluid signal of the lesion (arrow)

Fig. 9

Ultrasound image showing multiple subcapsular cystic lesions (arrowheads) bulging into the perinephric space outlining the entire kidney in a patient with lymphangiectasia

Fig. 10

A right perinephric pseudocyst (short arrow). Note the substantial inflammation in the anterior pararenal space centred on the pancreas (long arrow) in a patient with acute pancreatitis

Fig. 11

Portal venous CT shows a right renal abscess that has burst into the perinephric space (arrow), best appreciated as the soft tissue density interposed between the kidney and adjacent liver

Fig. 12

Three types of bridging septa have been described: reno-renal, fibres running parallel to the renal capsule and attaching back onto the kidney; reno-fascial, septa connecting the capsule to the adjacent anterior or posterior renal fasciae; and interconnecting fascia, connecting the anterior and posterior layers of the perinephric fascia

Fig. 13

Hypo-enhancing soft tissue fills the right renal pelvis, obliterating sinus fat and propagating along the proximal ureter (arrows). The overall reniform shape of the kidney is preserved, and the parenchyma is stretched but not invaded (arrowheads)

Fig. 14

Diffuse large B-cell lymphoma filling the left perirenal space and laterally displacing the kidney. The best clue to the diagnosis is that patent vessels can be seen passing through the mass (arrows)

Fig. 15

A soft tissue mass indents the kidney and cava (short arrows) and displaces gut. Biopsy showed it was a liposarcoma, although no macroscopic fat was evident on imaging

Fig. 16

A homogenous low-density myxosarcoma (arrows) in the left perirenal space encases the anterolateral kidney

Fig. 17

Retroperitoneal blood in the perinephric space secondary to haemorrhage from a large angiomyolipoma, evident as a fatty cleft in the right kidney (arrows). Only a small amount of kidney can be seen on the medial side

Fig. 18

A predominantly fat-containing exophytic suprarenal angiomyolipoma. Note the small cleft (short arrow) in the superior pole renal cortex and the prominent vessel (long arrow) passing through this

Fig. 19

Axial portal venous CT shows a heterogeneous mass (short arrow) at the right renal hilum, with invasion of the inferior vena cava (long arrow). This was excised and was pathologically shown to be a phaeochromocytoma

Fig. 20

A homogenous low-density mass extending into the right perinephric space (arrow), with broad contact with the psoas fascia. This is a biopsy-proven neurofibroma

Fig. 21

Coronal portal venous CT demonstrating an exophytic heterogeneous renal cell carcinoma arising from the lower pole of the right kidney (arrow)

Fig. 22

A large perinephric heterogeneous melanoma metastatic mass displaces the right kidney superiorly. A separate liver metastasis is present (short arrow), as is a metastasis to the small bowel (long arrow)

Fig. 23

Axial portal venous phase CT shows a homogenous soft tissue metastasis in the right perinephric space, slightly indenting the adjacent kidney (arrow). The primary tumour, an adrenal carcinoma, had been excised previously (see clips dorsal to the inferior vena cava)

Fig. 24

a A portal venous phase CT shows a soft tissue rind encasing both kidneys and extending into the renal sinus. b The coronal reconstruction shows underlying renal parenchyma appearing normal in this patient with Erdheim-Chester disease

Fig. 25

Marked expansion of the right perinephric fat with irregular soft tissue bands passing through it (arrows). More nodular soft tissue is present in the sinus fat and medial aspect of the perinephric space in this patient with excision-proven Rosai-Dorfman disease