Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
a central core consisting of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessel...
Adrenal calcification is not a rare finding in healthy asymptomatic people and is usually the result of previous haemorrhage or tuberculosis. Addison disease patients only occasionally develop calcification.
sepsis: Waterhouse-Friderichsen syndrome
Adrenal cysts are rare lesions and are commonly incidental findings.
Adrenal cysts are reported to be rare with an incidence of <1% 1.
Patients can present with pain or swelling, although a significant portion (~40%) are incidental findings 1,3.
Despite its small size, the adrenal gland is affected by a relatively large number of neoplastic entities:
adrenal cortical carcinoma
adrenal lesions: for a more general list of...
Adrenal haemorrhage can result from a variety of traumatic and non-traumatic causes. When unilateral, it is often clinically silent. In contrast, bilateral adrenal haemorrhage can lead to catastrophic adrenal insufficiency.
The large majority of patients with unilateral a...
Adrenal lesions cover a broad spectrum from benign to neoplastic entities. Due to increased use of cross-sectional imaging they are frequently detected as incidental lesions ("incidentalomas"). If found incidentally, please refer to the Management of incidental adrenal masses: American College o...
Asbestos related disease, in particular affecting the lung, comprise of a broad spectrum of entities related to the inhalational exposure to asbestos fibres. They can be divided into benign and malignant changes 1-3.
Benign pleural and parenchymal lung disease
asbestos related benign pleural d...
The differential for bilaterally enlarged adrenal glands is relatively limited:
micronodular adrenal hyperplasia
macronodular adrenal hyperplasia
adrenocorticotropin (ACTH)-independent macronodular adrenocortical hyperplasia (AIMAH) 2
Bilateral renal enlargement can arise from a number of causes which include 1:
diabetic nephropathy (common)
renal involvement with lymphoma
adult dominant polycystic kidneys (ADPKD)
bilateral renal cell carcinoma
Bilateral testicular lesions have a relatively limited differential diagnosis.
lymphoblastic leukemia (acute or chronic)
primary testicular lymphoma is rare but the testes are often the site of lymphoma/leukemia recurrence due to ...
Bladder outlet obstruction (BOO) can arise from a number of conditions affecting the urethra and/or bladder outlet.
Patients often present with difficulty in urination, retention and urinary discomfort 2.
Obstruction can be caused by multiple etiologies...
Differential diagnosis for bladder wall thickening depends on whether the bladder is adequately distended. The bladder wall may be thickened if:
>3 mm when distended
>5 mm when nondistended
If the bladder is not distended, then it is difficult to exclude artifactual thickening from a collapse...
Brachytherapy, also known as sealed source radiotherapy or endocurietherapy, is a form of radiotherapy where a radioactive source is placed, under the guidance of imaging, within or next to the area requiring treatment.
Brachytherapy is commonly used to treat localised prostate cancer, breast c...
There are many signs in radiology that are related to Christmas:
snowcap sign in avascular necrosis
in total anomalous pulmonary venous return
in pituitary macroadenomas
snowstorm appearance in complete hydatidiform and testicular microlithiasis
holly leaf sign in calcified pl...
Chronic primary adrenal insufficiency has a number of causes. Primary adrenal insufficiency is termed Addison disease.
idiopathic atrophy: autoimmune adrenalitis 1
tuberculosis 1: 25% calcify
fungal disease 1
COL4A1-related disorders are a group of autosomal dominant disorders caused by a mutation in the COL4A1 gene.
The exact prevalence is unknown, but the group of disorders is considered to be under-recognised, especially asymptomatic variants 1.
The clinical ...
Congenital adrenal hyperplasia (CAH) is a form of adrenal hyperplasia related to a variety of autosomal recessive disorders in adrenal steroidogenesis; characterized by low cortisol, low aldosterone and androgen excess.
virilization/genital ambiguity of female fetuses (d...
Congenital anomalies of the male urethra include various anomalies due to complex development of urethra. These anomalies can be isolated or in association with other coexisting anomalies. They can be categorised as following:
posterior urethral valve
anterior urethral valv...
Congenital renal anomalies comprise of vast spectrum of pathologies and include:
congenital renal hypoplasia
congenital cystic renal disease
infantile polycystic renal disease: autosomal recessive polycystic kidney disease (ARPKD):...
Renal cortical nephrocalcinosis is ~20 times less common than medullary nephrocalcinosis.
renal cortical necrosis: common 2
toxaemia of pregnancy
extracorporeal shock wave lithotripsy (ESWL)
There several cystic lesions around the vagina and female urethra; some of the imaging differential considerations would include:
Gartner duct cyst: at or above the level of the pubic symphysis anterior to the vaginal wall
Bartholin gland cyst: posterolateral to distal v...
Testicular cystic lesions are a relatively common occurrence on testicular ultrasound. They result from widely variable pathological entities ranging from benign to malignant. These entities include:
simple testicular cyst
tunica albuginea cyst (mesothelial cyst)
cystic transformation of rete...
A cystic retroperitoneal lesion can carry a relatively broad differenital which includes:
retroperitoneal cystic lymphangioma
retroperitoneal mucinous cystadenoma
retroperitoneal cystic teratoma
retroperitoenal cystic mesothelioma
pseudomyxoma retroperitonei with cystic change
Echogenic renal pyramids in children can be due to many different causes.
Iatrogenic (most common cause)
Empyemas are purulent inflammatory collections within a body cavity. They are similar to abscesses, which arise within parenchymal tissue rather than occupying a pre-existing anatomical space.
Colloquially, the term empyema is used to refer to thoracic empyemas but there are variou...
The term epidermoid cyst can refer to a:
epidermal inclusion cyst
intracranial epidermoid cyst
splenic epidermoid cyst
spinal epidermoid cyst
testicular epidermoid cyst
Epididymal calcification can be seen on ultrasound as hyperechoic foci within the epididymal head. If the calcifications are large enough, then they may demonstrate acoustic shadowing.
chronic epididymitis: e.g. bacterial, granulomatous (TB) or genital filariasis
Epididymal masses are most commonly encountered on ultrasonography. Most epididymal masses are benign; malignant lesions are rare.
adenomatoid tumour of the scrotum (most common epididymal mass 4)
sperm granulomas / post vasectomy gra...
Multiple criteria are used to detect extracapsular extension of prostate cancer. They include 3:
an irregular bulge in capsule
obliteration of the rectoprostatic angle
asymmetry of the neurovascular bundle
angulation/step-off appearance to the tumour
focal capsular retraction and or thicken...
Extratesticular scrotal masses (non-testicle and non-epididymis) are mostly mesenchymal in origin and benign 1.
lipoma (most common)
leiomyoma of the scrotum
granular cell tumor
fibrous hamartoma of infancy...
There are numerous fat-containing renal lesions, including:
renal cell carcinoma
renal or perirenal lipoma/liposarcoma
Non-mass lesions may also occasionally contain fat:
renal junction line
fat in a renal scar
renal sinus lipomatosis
Fetal pyelectasis refers to a prominence of the renal pelvis in utero that is a relatively common finding, which in the majority of cases resolves spontaneously.
Please refer to the article on fetal hydronephrosis for a continued discussion on this matter.
Although there is an ...
There numerous causes of gas in the bladder. In the hospital setting by far the most common is the recent placement of an indwelling urinary catheter. Other causes include:
IDC by far the most common cause
intraluminal and intramural gas
Haematospermia refers to the presence of blood in semen or ejaculatory fluid. It is a symptom that can cause great anxiety in patients despite commonly being of benign aetiology.
urogenital infections including sexually transmitted disease
commonest cause in patients <40 ...
Despite the vast majority of renal cancers being sporadic, there are a number of hereditary renal cancer syndromes:
von Hippel Lindau syndrome: predominantly clear cell type
tuberous sclerosis: predominantly clear cell type
hereditary leiomyomata renal cell cancer syndrome: described in ISUP ...
Genitourinary manifestations of HIV/AIDS are protean and can be divided into:
renal diseases related to opportunistic infections: CMV, tuberculosis and MAC infections, fungal infections, pneumocystis carinii infection
drug-related renal diseases:
HIV-associated neoplasms are numerous and can be broadly divided into two groups:
associated but not AIDS defining malignancies
The development of these malignancies in HIV affected individuals generally implies progression to AIDS 4:
Hydronephrosis is defined as dilatation of the urinary collecting system of the kidney (the calyces, the infundibula, and the pelvis) 1. The term hydroureteronephrosis is used when the dilatation also involves the ureter.
Hydronephrosis in fetuses and newborns has specific causes that are cove...
Hyper-reninaemic hypertension may have many causes including:
renal artery stenosis
renal secreting tumour, e.g. renal cell carcinoma, reninoma
renal compression: large renal mass, subcapsular haemorrhage (Page kidney)
Infertility is common, affecting 15-20% of couples, and is defined as the inability to conceive after one year of unprotected intercourse in the fertile phase of the menstrual cycle 3. It can be due to a variety of both female and male factors, and these are discussed in separate articles:
Intra-abdominal calcification in a neonate can be caused by a number of pathologies that cause calcification within the peritoneal space or within organs.
The commonest cause is meconium peritonitis which is the result of aseptic peritonitis secondary...
There are relatively few of causes of low signal intensity renal parenchyma. Causes include:
paroxysmal nocturnal haemoglobinurea.
mechanical: malfunctioning prosthetic cardiac valve
sickle cell disease
hemorrhagic fever with renal syndrome (HFRS)
Medical devices in the abdomen and pelvis are important to be recognised, just like medical devices of the chest. Often we ignore these devices, considering them to be incidental and non-pathological, however it is essential to be aware of potential complications.
Renal medullary nephrocalcinosis is the commonest form of nephrocalcinosis and refers to the deposition of calcium salts in the medulla of the kidney. Due to the concentrating effects of the loops of Henle, and the biochemical milieu of the medulla, compared to the cortex, it is 20 times more co...
Patients with malignant ureteric obstruction and poor life expectancy usually require placement of ureteral stents to relieve the urinary obstruction and as a palliative measure to reduce pain and avoid major operation.
Metallic ureteric stents have recently been developed to try and offer bett...
Metastases to testis are a rare cause of a testicular mass and may be bilateral in up to 15% of patients.
Metastases to the testes are apparent in ~0.04% of autopsy studies in patients with known malignancy. The average age is 57 years, much older than the primary age for primary...
Milk of calcium (MOC) is a term given to dependent, sedimented calcification within a cystic structure or hollow organ. This sort of colloidal calcium suspension layering can occur in various regions:
renal cysts: milk of calcium in renal cyst (most common)
breast cysts: milk of calcium in bre...
Multiple endocrine neoplasia (MEN) syndromes are a collection of syndromes characterised by the presence of, as the name would suggest, multiple endocrine tumours. They are autosomal dominant in inheritance.
MEN1 (Wermer syndrome)
MEN2 (multiple endocrine adenomatosis)
MEN2a (Sipple syndrome)...
Multiple filling defects within a ureter, as seen on conventional IVU or CT IVU, have a relatively small differential including:
spreading or multifocal transitional cell carcinoma (TCC)
multiple ureteral stones (steinstrasse)
Nephrocalcinosis, previous known as Anderson-Carr kidney or Albright's calcinosis, refers to the deposition of calcium salts in the parenchyma of the kidney. It is divided into several types, with differing aetiologies, based on the distribution:
medullary nephrocalcinosis: 95%
Both neuroblastoma and Wilms tumour occur in early childhood and typically present as large abdominal masses closely related to the kidneys. Distinguishing between the two is important, and a number of features are helpful.
calcification very common: 90%
encases vascular structu...
Non-seminomatous germ cell tumours (NSGCT) is one of the main groups of germ cell tumours (the other being seminoma). Although they are made up of distinct histological entities, in general, they have similar radiographic appearances. They can, however, be found widely in the body, with variable...
An obstructive uropathy is a catch-all term encompassing any cause of complete or partial, congenital or acquired and permanent or intermittent obstruction to the urinary tract. Depending on the severity of obstruction and extent, it may result in permanent change in both the collecting system p...
Oxalosis results in supersaturation of calcium oxalate in the urine (hyperoxaluria), which in turn results in nephrolithiasis and cortical nephrocalcinosis.
This article focus on the secondary oxalosis, please refer to primary oxalosis for a specific discussion on this entity.
Paediatric renal tumours and masses are another group of diseases (just like cystic renal diseases in both the adult and child) that are bewildering in their number, nomenclature and overlapping findings.
Wilms tumour: common in older children 1-8 years old
Paratesticular lesions have a large list of differential diagnosis:
epididymal cyst (most common epididymal mass)
adenomatoid tumour (most common epididymal tumour)
scrotal tunica cysts
tunica vaginalis cyst
tunica albuginea cyst
A paratesticular mass may derive from a number of structures that surround the testicle within the scrotum; most commonly, they derive from the spermatic cord.
The masses can be categorised as benign (70%) or malignant (30%).
spermatic cord lipoma (most common pa...
Pear-shaped (or tear-drop-shaped) bladder is one whose normal round or ovoid shape has been extrinsically compressed to resemble a pear. The pear may be inverted or upright, depending on how the excess pelvic tissue compresses the bladder.
Causes of a pear-shaped bladder i...
Perinephric fluid collections are commonly seen after renal transplantation. The appearance of a perinephric fluid collection is often nonspecific, and generating a differential often relies on when the transplant occurred.
Early post-transplant period
PET-CT is a combination of cross-sectional anatomic information provided by CT and the metabolic information provided by positron emission tomography (PET).
PET is most commonly performed with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG). Fluorine-18 (F-18) is an unstable radioisotope and has a half-...
Transrectal ultrasound–guided biopsy is considered the standard approach for prostate biopsy and is most commonly performed on an outpatient with a positive screening for prostate cancer.
Nowadays, with the MRI capacity for depicting abnormal areas of the prostate, is possible to obtain target...
Prostate cystic disease encompasses a wide variety of pathologies that all result in cyst formation within the prostate.
midline cystic lesions / cyst like lesions
Mullerian duct cyst
prostatic utricle cyst
ejaculatory duct cyst (tends to be more paramidline 6)
cystadenoma of prostate
Prostate peripheral zone T2 hypointensity is a common finding in pelvic MRIs that needs to be differentiated. A prostate directed MRI is usually performed using a multi-parametric technique to differentiate prostate cancer from more benign changes. This includes T2 weighted images, dynamic contr...
Prostatic utricle cyst (PUC) is an area of focal dilatation that occurs within the prostatic utricle.
They are midline cystic masses in the male pelvis and can be very difficult or impossible to distinguish from a Mullerian duct cyst.
Utricle cysts are most often detected in the ...
Prostatomegaly is a term used to generally describe enlargement of the prostate gland from whatever cause. Usually the prostate is considered enlarged on imaging when it measures beyond 30 cc (30 grams) in size.
The term prostatomegaly is often used interchangeably with benign pro...
Pseudobladder refers to a pelvic cystic mass that simulates the urinary bladder.
The location of the lesion should allow differentiation from the bladder but if doubt exists and clinical necessity arises, a delayed phase CT or MRI with excreted contrast or IDC-administered retrograde contrast f...
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...
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.
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...
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 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 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 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 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...
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 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 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...
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.
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
Sciatic hernia is a rare type of pelvic floor hernia, which occurs through either the greater or lesser sciatic foramina.
curlicue ureter sign
The scrotum and its content are subject to a number of infective processes including:
Scrotal tunica cysts are paratesticular cystic lesions. They include:
tunica vaginalis cysts
tunica albuginea cysts
Typically seen as a simple appearing paratesticular cystic lesion not in the region of the epididymis.
Solitary filling defect with a ureter, as seen on conventional IVU or CT IVU has some differentials, including:
within the lumen
within the wall
transitional cell carcinoma (TCC)
When multiple fi...
Testicular cancers are the most common neoplasm in men between the ages of 20 and 34.
Testicular cancer is uncommon, accounting for less than 1% of all internal organ malignancies 2.
The demographics of affected individuals depends on the age of the histology of the tumour. Over ...
Testicular microlithiasis (TM) is a relatively common condition that represents the deposition of multiple tiny calcifications throughout both testes.
The most common criterion for diagnosis is that of five microcalcifications in one testicle, although definitions have varied in the past. In t...
Testicular trauma is the third most-common cause of acute scrotal pain and may result in various degree of damage to the testes.
Testicular rupture and testicular ischaemia/infarct are two severe complications which need to be ruled out. Other injuries that can occur include 1:
Tuberculous adrenalitis is the result of adrenal mycobacterium tuberculosis (TB) infection. Its incidence has decreased in the western world with the declining incidence of tuberculosis.
As the tuberculous infection causes destruction of the adrenal cortex, primary adrenal insufficie...
Tumours of the male urethra are uncommon. They can be categorised both on the grounds of histology and location.
squamous cell carcinoma of the urethra: 80%
urothelial/transitional cell carcinoma of the urethra: 15% (predominantly posterior urethra)
adenocarcinoma of the urethra: 5...
There are numerous causes of urinary bladder diverticula:
Primary (congenital or idiopathic)
Hutch diverticulum (in paraureteral region)
Bladder outlet obstruction
bladder neck stenosis
posterior urethral valve
prostatic enlargement (hypertrophy; carcinoma)
Bladder diverticulum are outpouchings from the bladder wall, whereby mucosa herniates through the bladder wall. They may be solitary or multiple in nature and can vary considerably in size.
There are two peaks - one at 10 years and the other at 60-70 years 2.
Causes of urinary bladder wall or lumen calcification include:
schistosomiasis of the urinary tract
calculus in a urachal cyst or in a bladder divertic...