Pseudohydronephrosis refers to normal anatomy or non-significant pathologies that may mimic hydronephrosis. There is usually fluid-density material within a dilated of a part of the urinary tract, but without other signs of obstruction such as retroperitoneal fat stranding, renal perfusion abnor...
Pseudoureterocoeles are acquired dilatations of the submucosal portion of the distal ureter that mimic simple ureteroceles. The appearance of the radiolucent wall surrounding the dilated distal ureteral segment (cobra head sign) is an important differentiating point.
The distinction is importa...
A psoas hitch is a method of ureteric re-implantation following distal ureteric resection or injury.
The reconstruction is indicated when the distal ureter is injured or resected for cancer or stricture disease, and the remaining portion of ureter cannot reach the bladder for a ureteroneocystot...
Pulmonary-renal syndromes refer to a group of conditions that can affect the lung and kidneys. These conditions are typically characterised by diffuse alveolar haemorrhage and glomerulonephritis.
Diseases that can result in a pulmonary-renal syndrome includes:
certain pulmonary vasculitides
A putty kidney refers to a pattern of renal calcification associated with renal tuberculosis conventionally described on plain radiography. Calcification characteristically is very homogeneous and ground glass like, representing calcified caseous tissue 3-4. Premkumar et al labelled calcificatio...
Pyelography (or "pyelogram") refers to imaging of the urinary collecting system.
The term is most often encountered in 'intravenous pyelography' (or "IVP"). For some, this is a misnomer and a test that images intravenous contrast as it travels through the kidney parenchyma into the urinary coll...
Pyelonephritis refers to an upper urinary (renal) tract infection with associated renal pelvis, renal calyceal and renal parenchymal inflammation, and comprises a heterogeneous group of conditions.
Pyelostomy is a rarely performed procedure in which a externalized catheter drains the renal pelvis. It is different from a nephrostomy in that the catheter enters the renal pelvis directly without passing though the renal parenchyma. It is much more prone to complication than a nephrostomy.
Pyonephrosis is a term given to an infection of the kidney which leads to pus in the upper collecting system which can progress to obstruction.
The diagnosis of pyonephrosis is suspected when the clinical symptoms of fever and flank pain are combined with the radiologic evidence of obstruction ...
Both radiation and chemotherapy can result in severe haemorrhagic cystitis, the appearances of which vary with time from the therapy. It can be divided into acute and chronic.
In the acute phase of radiation and chemotherapy cystitis, there is a hemorrhagic cystitis secondary to denudat...
Randall's plaques are described as subepithelial calcification of the renal papilla 1 which are <2 mm in their greatest dimension. They act as an anchor for calcium oxalate crystals and are considered to be predisposing factor for renal stone formation.
RASopathies are a class of developmental disorders caused by germline mutations in genes that encode for components or regulators of the Ras/mitogen activated protein kinase (MAPK) pathway.
As a group, RASopathies represent one of the most common malformation syndromes, with an in...
Radiological manifestations of recreational drug use are not infrequently seen as the use of recreational drugs is widespread.
Interestingly, recent reports have suggested a decreasing incidence of reported drug use in the general population over the past decade, but it remains th...
The rectouterine pouch, also known as the rectovaginal pouch, cul-de-sac or pouch of Douglas, is an extension of peritoneum between the posterior wall of uterus and the rectum in females. It is the most dependent part of the peritoneal cavity and is analogous to the rectovesical pouch in males.
Rectovesical pouch is the forward reflection of the peritoneum from the lower third of the rectum to the upper part of the bladder in males.
The rectovesical pouch is the lowest part of the peritoneal cavity and usually contains loops of small bowel or sigmoid colon. It is 7.5 cm...
Renal abscess, like any other abscess, is a collection of infective fluid in the kidney. It is usually a sequela of acute pyelonephritis, where severe vasospasm and inflammation may occasionally result in liquefactive necrosis and abscess formation.
It can affect all ages and has ...
A renal adenoma is type of benign renal neoplasm.
It is traditionally classified into three distinct types 1
renal papillary adenoma
renal tubular adenoma
alveolar renal adenoma
Renal agenesis refers to a congenital absence of one or both kidneys. If bilateral (traditionally known as the classic Potter syndrome) the condition is fatal, whereas if unilateral, patients can have a normal life expectancy.
Unilateral renal agenesis affects approximately 1 in ...
Renal amyloidosis is rare as an isolated entity but can be associated with systemic amyloidosis. Renal involvement from amyloidosis in pathological specimens is quite common. However, renal function compromise is rare.
It usually manifests as nephrotic syndrome:
Renal angiomyolipomas (AMLs) are a type of benign renal neoplasm encountered both sporadically and as part of a phakomatosis, most commonly tuberous sclerosis. They are considered one of a number of tumours with perivascular epitheloid cellular differentiation (PEComas) and are composed of vascu...
Renal antibiomas are postinflammatory cystic fluid
collections during or after antibiotic treatment for acute
pyelonephritis. These are usually < 3 cm sized, with no or minimal
post contrast wall enhancement or thickening.
They may mimic a renal abscess or perinephric abscess.
Renal arterial cut-off sign as the name suggests is an abrupt termination of the vascular contrast opacified renal arterial lumen. It may be associated with or without any contrast extravasation
It is seen in a vascular injury like segmental or main renal artery thrombosis or occlusion.
The renal arterial resistive index (RI) is a sonographic index to assess for renal arterial disease.
It is measured as
RI = (peak systolic velocity - end diastolic velocity ) / peak systolic velocity
the normal value is ≈ 0.60
with 0.70 being around the upper limits of normal
Renal arteriovenous fistulae (AVFs) are anomalous direct communications between arteries and veins in the kidney, which may be confused with a renal arteriovenous malformation (AVM).
The incidence of renal AVF is variable, estimated at 0.3-19% in native kidneys and 6-8% in ren...
Renal arteriovenous malformations (renal AVMs) are an uncommon vascular anomaly, which may be confused with a renal arteriovenous fistula (renal AVF).
Like arteriovenous malformations elsewhere in the body, a renal AVM is formed by a connection between the arterial and venous structu...
The renal arteries originate from the abdominal aorta and enter the renal hila to supply the kidneys. Any variant in arterial supply is important to clinicians undertaking surgery or other interventional renal procedures.
They arise from the abdominal aorta at the L1-2 ...
Renal artery aneurysms (RAA) are considered the second most common visceral aneurysm (15-22%), most common being splenic artery aneurysm (60%). They are more common in females. Most of the lesions are saccular and tend to occur at the bifurcation of main renal artery.
RAAs occur i...
Renal artery dissection may occur as a result of the following processes 1:
aortic dissection extending to involve the renal artery
iatrogenic (e.g. catheterisation)
Renal artery occlusion can happen acutely due to in-situ thrombus, embolism, or dissection. Unless immediately treated, it can lead to renal infarction 1.
The condition is more common in the elderly, however, it may be seen in a younger age group if they have risk factors (describ...
Renal artery pseudoaneurysms are uncommon vascular finding, with the majority occuring after a renal intervention.
A renal artery pseudoaneurysm differs from a renal artery true aneurysm (as might occur in fibromuscular dysplasia) in that it does not involve all three layers of the a...
Renal artery stenosis (RAS) refers to a narrowing of a renal artery. When the process occurs slowly, it leads to secondary hypertension. Acute renal artery stenosis does not lead to hypersecretion of renin.
When the stenosis occurs slowly, collateral vessels form and supply the kidne...
Renal cell carcinomas (RCC) are primary malignant adenocarcinomas derived from the renal tubular epithelium and are the most common malignant renal tumour. They usually occur in 50-70-year-old patients and macroscopic haematuria occurs in 60% of the cases.
On imaging, they have a variety of ra...
Renal cell carcinoma staging using the TNM staging system for renal cell carcinoma. Older but still widely used system in some practices is the Robson staging system.
TNM staging (7th edition)
T1a: tumour confined to kidney, <4 cm
T1b: ltumour confined to kidney, >4 cm but <7 cm
Renal colic refers to a pattern of abdominal pain most commonly caused by ureteric calculi. The pain is felt in the loin radiating down to the groin and is typically colicky (i.e. coming in waves) corresponding to peristalsis or spasm of the ureter. While the term really only directly applies to...
Renal cortical defects have a variety of causes, and present on imaging as an area of focal cortical thinning or absence of renal cortex, sometimes accompanied by focal caliectasis.
The differential diagnosis for a renal cortical defect includes 1,2:
Renal cortical necrosis occurs as a result of severe systemic illness in a variety of settings and can result in permanent renal impairment.
severe haemodynamic shock
traumatic blood loss
Renal cysts are a common finding in the kidneys. Findings common to all "simple" renal cysts are well-marginated, thin walls with no enhancement of the cyst. They can be diagnosed on ultrasound, CT, or MRI. A cystic lesion in the kidney that deviates from the typical "simple" cyst appearance sho...
Renal dysgenesis is a very broad term which can include any form underdevelopment of the kidneys. The spectrum includes:
renal agenesis: complete lack of formation
renal hypoplasia: partial lack of formation
Some authors also classify any form of renal maldevelopment affecting size, shape of ...
Renal forniceal or calyceal rupture is the radiographic finding of a perirenal urine leak as a result of ureteric obstruction.
The renal fornix is the most susceptible part of the renal collecting system to rupture from increased pressure 2,3.
Causes include 1,2:
Renal hemosiderosis results from accumulation of hemosiderin in the kidneys.
Renal haemosiderosis is a known complication of the following conditions:
chronic intravascular hemolytic states such as haemolytic anaemias like sickle cell anemia and thalassemia 1,3
paroxysmal nocturnal hemoglo...
A renal hilar lip is a developmental anomaly of the kidney. It is an infolding of the cortex at the level of the renal sinus and in this region the renal cortex appears thicker.
On imaging it appears as supra- or infra-hilar cortical bulges. At certain levels of cross ...
Renal hydatid infection is extremely rare and is seen in less than 5% of patients with hydatid disease1. Infection is caused by a parasitic zoonosis with the Echinococcus tape worm. (see Hydatid disease for a general discussion). The kidneys are the most commonly affected urinary organs, but bla...
Renal hypoplasia refers to a congenitally small kidney where there is essentially normal residual parenchyma but smaller calyces, lobules and papillae. This is in contrast to renal atrophy where renal development was initially normal has become smaller as secondary sequelae from various other pa...
Renal infarction results from interruption of the normal blood supply to part of, or to the whole kidney. The main imaging differential diagnosis includes pyelonephritis and renal tumours.
The demographics of affected patients will depend on the underlying cause, although as most ...
Renal lymphangiectasia (or renal lymphangioma), is a rare disorder, where there is dilatation of perirenal, peripelvic and intrarenal lymphatics. The diagnosis can be suggested by imaging, and aspiration of chylous fluid is usually confirmatory.
It is important to note that there i...
Renal lymphoma is usually seen as a part of spectrum of multi-systemic lymphoma, however, rarely may be seen as a primary disease.
While renal lymphoma has autopsy incidence of 30-60% in lymphoma patients, actual CT diagnosis incidence is ~ 5%1.
The kidneys are the most common ab...
A renal mass can be broadly divided into two broad categories:
Renal medullary carcinoma is a rare variant of renal cell cancer, which is a highly aggressive malignant tumour of the kidney.
Renal medullary carcinoma occurs almost exclusively in adolescent and young adult blacks with sickle cell trait or haemoglobin SC disease but not with ho...
Renal milk of calcium cysts refer to the appearance of a calcium precipitate found within a calyceal diverticulum that has lost communication with the collecting system or within a simple renal cyst.
Renal milk of calcium cysts are typically asymptomatic.
Renal oncocytoma is a relatively benign renal tumour. The main clinical importance of this lesion is the difficulty in pre-operatively distinguishing it from renal cell carcinomas, as epidemiology, presentation, imaging and even histology can be very similar.
Renal oncocytomas ac...
Renal oncocytosis, also known as renal oncocytomatosis, is the presence of many concurrent renal oncocytomas with or without renal cell carcinomas. Typically a dominant larger tumour is present, with bilateral innumerable smaller tumours. Sometimes renal failure may develop 1.
Renal osteodystrophy (ROD), also known as uraemic osteopathy, is the constellation of musculoskeletal abnormalities that occur in patients with chronic renal failure, due to concurrent and superimposed:
osteomalacia (adults) / rickets (children)
secondary hyperparathyroidism: abnormal calcium ...
Papillary adenoma of the kidney is a benign renal neoplasm arising from the renal tubular epithelium and almost always located within the cortex. It falls under the general category of renal adenomas and is considered one of the commonest of renal epithelial neoplasms.
Renal papillary necrosis refers to ischemic necrosis of the renal papillae. Necrosis also occurs in the medullary pyramids.
Patients can present with both acute episodes or chronic renal papillary necrosis. Calyceal or ureteral obstruction by sloughed papillae manifest with f...
Mnemonics for the causes of renal papillary necrosis are plentiful and include:
AD SPORT C
The latter is a list of causes in order of incidence.
Most common causes:
N: non-steroidal anti-inflammatory drugs (NSAIDs)
S: sickle cell disease
A: analgesic abu...
The renal pelvis forms part of the pelvicalyceal system of the kidney and is the connection between the calyces and the ureter.
The renal pelvis is triangular in shape, lies posteriorly in the renal hilum surrounded by fat and vessels and is formed by the either the union of two-...
A renal pseudotumour is a mass that will simulate a tumour on imaging but is composed of non-neoplastic tissue. There are many examples 1:
prominent column of Bertin
persistent fetal lobulation
cross-fused renal ectopia
renal hilar lip
Renal replacement lipomatosis is a rare condition characterised by fatty tissue proliferation in renal sinus and perinephric space with marked destruction/atrophy of renal parenchyma (due to chronic inflammation).
It has been associated with ageing, calculus disease (nearly 70% of ca...
The renal sinus is a fat-filled compartment of the kidney.
The renal sinus is a fatty compartment located within the medial aspect of the kidney. It communicates with the perinephric space. It contains the renal hilum and is bordered by renal parenchyma laterally.
Renal sinus cysts are simple renal cysts that lie within the renal sinus.
It is worth noting that some authors 5,6 use the term renal lymphangiectasia interchangeably. It is likely that true renal lymphangiectasia is a separate and rare disorder, and is thus discussed separately.
Renal sinus lipomatosis refers to a condition where there is excessive renal sinus fat replacement.
It results from renal parenchymal atrophy, inflammation, calculous disease, ageing or exogenous or endogenous steroids.
There is usually no or rarely little mass effect on collecting ...
Renal sympathetic denervation (RSDN), also known as renal denervation, is an interventional procedure that uses radiofrequency ablation to destroy the nerve endings in the wall of the renal arteries. Endovascular (trans-catheter) techniques are an alternative to surgical sympathectomy.
Renal tract calculi, also known as urolithiasis, refer to renal stone formation at any point along the renal tract (from kidneys to bladder and urethra).
This is a summary article; read more in our article on urolithiasis.
presentation between 30 and 6...
Renal transplantation is one, if not the most, common transplant procedures undertaken worldwide. Consequently, purposeful and incidental imaging of renal transplants and renal transplant-related complications are increasingly common. These include acute renal transplant rejection and chronic re...
Renal transplant rejection is one of the feared complications of renal transplantation.
In terms of onset, this can be broadly divided into two groups
acute renal transplant rejection
chronic renal transplant rejection: usually after one year post transplantation (at least after 3 months)
The recipients of renal transplants are susceptible to a number of complications.
Renal transplant complications
These can be broadly categorised as perirenal, renal parenchymal, renal collecting system, and/or renal vascular complications 1,2:
renal transplant rejection
The central approach of renal transplant ultrasound is to evaluate for possibly treatable surgical or medical complications arising in the transplanted kidney.
Institutions vary in the exact schedule of renal transplant ultrasound assessment, but it is common to obtain an initial ultrasound 24-...
Renal trauma can result from direct, blunt, penetrating and iatrogenic injury.
Renal injuries account for ~10% of abdominal trauma, and thus the demographic of affected individuals reflects that population. The incidence of renal injuries increases in pre-existing congenital or ac...
Renal tuberculosis, a subset of genitourinary tuberculosis, accounts for 15-20% of extra-pulmonary tuberculosis and can result in varied and striking radiographic appearances.
Tuberculosis can involve both the renal parenchyma and the collecting system (calyces, renal pelvis, ureter, bladder a...
Renal tubular ectasia is an incidental finding that is seen more commonly on intravenous pyelography (IVP), but which can also occasionally be seen on CT urography (CTU).
Renal tubular ectasia is also known as benign renal tubular ectasia. The term "benign" was used to differentiat...
Renal tumours (for the purposes of this article taken to broadly mean neoplastic lesions) should be distinguished from renal pseudotumours.
Whilst renal tumours can be broadly divided into primary and secondary (metastatic), benign and malignant or adult and paediatric tumours, they are more fo...
Renal vascular pedicle injury is a severe form of renal trauma, which if not recognised and treated expediently with lead to the loss of the kidney.
Contrast enhanced CT is the Imaging modality of choice. On CT it is recognised as a non-enhaning kidney. Perirenal ha...
The renal veins are asymmetric paired veins that drain the kidneys.
The renal vein is formed by the union of two-to-three renal parenchymal veins in the renal sinus. It emerges from the renal hilum anterior to the renal artery and drains into the inferior vena cava at th...
There are several variations in renal venous anatomy. Some of these are specific to the left renal vein.
Left renal vein anomalies are generally classified into four types 2:
the ventral pre-aortic limb of the left renal vein is obliterated, but the dorsal retro-aortic limb persists a...
Renal vein thrombosis can be either from "bland" thrombus or tumour thrombus (extension of tumor into the vein). There are numerous aetiologies for bland thrombus, but it most commonly occurs in the hypercoagulable nephrotic syndrome. Renal vein thrombus is commoner on the left side, presumably ...
Renal vein varices develop for various reasons and are usually asymptomatic.
Renal vein varices are usually asymptomatic. Some patients may present with flank pain and/or haematuria.
chronic renal vein thrombosis
Renovascular hypertension (RVH) is a type of secondary hypertension, where high blood pressure develops secondary to renal artery disease.
Approximately 2.5% (range 0.5-5%) of hypertensive patients will have RVH as a cause 2,3.
There are a number of condit...
Retroaortic left renal vein (RLRV) is an anatomical variant where the left renal vein is located between the aorta and the vertebra and drains into the inferior vena cava.
Its recognition is important in order to avoid complications during retroperitoneal surgery or interventional procedures 2....
Retrograde pyelography (also known as retrograde pyeloureterography) is a method of imaging the upper urinary collecting system. After IVU and CTU were developed, it has been rarely performed as a primary study, but it still has a few potential indications as a secondary study.
Retroperitoneal fibrosis (RPF), is a condition that has previously been described as chronic periaortitis. It is an uncommon fibrotic reaction in the retroperitoneum that typically presents with ureteric obstruction.
The disease is part of a spectrum of entities that have a common pathogenic pr...
Retroperitoneal haemorrhage can be a source of significant yet occult blood loss.
The clinical features are varied depending on the amount of hemorrhage present, rate of onset and ability of the surrounding structures to contain the hemostatic system. The classical featur...
The retropubic space (also known as the prevesical space or cave of Retzius) is an extraperitoneal space located posterior to the pubic symphysis and anterior to the urinary bladder. It is separated from the anterior abdominal wall by the transversalis fascia and extends to the level of the umbi...
Rhabdoid tumour of the kidney is a rare, highly aggressive malignancy of early childhood, closely related to atypical teratoid/rhabdoid tumours (AT/RT) of the brain (see rhabdoid tumours)
Rhabdoid tumours occur exclusively in children, with 60% occurring before the age of 1 year o...
Rhabdomyosarcomas of the genitourinary tract are uncommon tumours occurring in pelvic organs. It is a disease nearly exclusive to the paediatric population.
For a general discussion of this type of tumour, please refer to the article on rhabdomyosarcomas.
The peak incidence of ...
Right iliac fossa mass is a common clinical presentation and has a range of differentials that need to be excluded. Radiology plays an important role in this differentiation.
The rim sign can be seen in association with chronic hydronephrosis.
In patient's with chronic hydronephrosis, in all forms of contrast-enhanced imaging of the obstructed kidney, enhancement may occur in the residual, but markedly atrophic, renal parenchyma, surrounding the dilated calices and...
Rim sign in renal vascular compromise is seen in major renal vascular compromise.
It can be seen in:
renal artery obstruction from embolism, thrombosis or dissection
renal vein thrombosis
acute tubular necrosis
At contrast enhanced CT or MR imaging, a thin (1-3 mm) ri...
Risk factors for testicular germ cell tumours (GCT) include:
Caucasians at higher risk than African Americans (9:1)
10-40x increased risk
around 10% of all tumours are associated with undescended testis
higher risk if intra-abdominal testis compared with intra-inguinal
Robson staging of renal cell carcinoma (RCC) is simple but has largely been replaced by the TNM system (see renal cell cancer staging article). Robson staging revolves around the relationship to Gerota's fascia, involvement of renal vein and regional nodes.
stage I: limited to kidney
The salt and pepper sign is used to refer to a speckled appearance of tissue. It is used in many instances, but most commonly on MRI. Please note that pathologists also use the term.
Used to describe some highly vascular tumours which contain foci of ha...
Sarcoidosis is a systemic inflammatory disease of unknown origin characterized by the formation of non-caseating granulomas. Virtually any organ system may be involved. Although the involvement of abdominal viscera is less frequent than pulmonary and mediastinal disease when it occurs, it may m...
Sarcomatoid renal cell carcinomas (sRCC) may develop when one of the more common subtypes of renal cell carcinoma degenerates into a sarcoma.
On imaging, they are generally large masses, with irregular contours, and malignant-appearing, but do not have specific imaging features.
Schiller-Duval body is a perivascular structure that can be found in 50% of testicular yolk sac tumours also known as endodermal sinus tumours. If present it is considered pathognomonic.
A central vessel is surrounded by tumour cells, and the cell-vessel complex is contained in a cy...