Cystic partially differentiated nephroblastomas are rare pediatric cystic renal tumors. They are distinct from pediatric nephromas although they have very similar imaging appearances.
Evolving terminology regarding cystic nephromas and other cystic renal tumors reflects ongoing cha...
Cystic renal disease can be confusing. There are many conditions, many of which have similar names or are eponymous, and with a few exceptions, are relatively rare. It is easiest to think of them into two separate demographic:
pediatric cystic renal diseases
adult cystic renal disease
Cystic renal dysplasia refers to a subgroup of congenital anomalies of the kidney and urinary tract characterized by the dysplastic renal parenchyma and formation of cysts. The most severe form is multicystic dysplastic kidney, in which functional renal parenchyma is absent and only undifferenti...
Cystic renal neoplasms comprise of heterogeneous group of renal tumors. They can have variable biological profiles. They may be purely cystic or could be cystic with solid components.
mixed epithelial and stromal tumor of kidney
Cystic retroperitoneal lesions can carry a relatively broad differential, which includes:
retroperitoneal lymphatic malformation
retroperitoneal mucinous cystadenoma
retroperitoneal cystic teratoma
retroperitoenal cystic mesothelioma
pseudomyxoma retroperitonei with cystic change
Cystinosis, also known as Abderhalden Kaufmann Lignac syndrome, is the most common hereditary cause of renal Fanconi syndrome. Cystinosis is one of the lysosomal storage disorders.
It has a reported incidence of 1:192,000 1. Cystinosis is typically diagnosed in infancy.
Cystinuria is an inherited condition in which there is an excess of cystine in the urine. This excess predisposes to the formation of cysteine stones.
"Cysteine" refers to the amino acid. "Cystine" is the oxidized dimer of the amino acid.
It is thought to occur in 1:...
Cystitis cystica is the same condition as ureteritis cystica and closely related to cystitis glandularis. It is a relatively common chronic reactive inflammatory disorders that occur in the setting of chronic irritation of the bladder mucosa.
Cystitis cystica is seen in a variety ...
Cystitis glandularis is a proliferative disorder of the urinary bladder in which there is glandular metaplasia of the transitional cells lining the urinary bladder. This entity is closely related to cystitis cystica, with which it commonly co-exists. It is a relatively common chronic reactive in...
A cystocele, also known as a prolapsed bladder, is a form of pelvic organ prolapse where the bladder descends inferiorly and posteriorly into the vagina and perineum. It may be accompanied by prolapse of other pelvic organs.
CT / MRI
Sagittal images are particularly use...
Cystography is a fluoroscopic study that images the bladder. It is similar to a voiding cystourethrogram (VCUG), and the difference between the studies is primarily one of emphasis; a cystogram focuses on the bladder and a VCUG focuses on the posterior urethra. The study has been adapted to CT a...
Cystolithotomy is a urologic procedure to remove one or more bladder stones.
It is typically performed for a patient with large or numerous bladder stones or if an endoscopic approach has not been successful.
The traditional approach described below is an open cystolithotomy. Other approaches...
Dancing megasperm is the ultrasound finding of continuously oscillating/mobile tiny echogenic foci within dilated tubules of the epididymis. This is seen in post-vasectomy patients and others with obstruction of the spermatic cord and is thought to represent clumps/clusters of trapped spermatozo...
The dartos muscle is the thin rugated fascial muscle of the scrotum made of smooth muscle. Hence it is also referred to as dartos fascia or simply the dartos. It forms from the subcutaneous tissue of the scrotum and base of the penis and attaches to the scrotal skin and fibrous midline septum be...
The deep inguinal lymph nodes (often shortened to the deep inguinal nodes) form a subgroup of the inguinal lymph node group, and are located within the femoral sheath, medial to the femoral vein. They receive afferent lymphatic drainage from the deep lymphatics of the distal lower extremity and ...
The deep perineal pouch is an anatomic space superior (deep) to the perineal membrane in the urogenital triangle of the perineum, anterior to the transverse line between the ischial tuberosities.
The deep perineal pouch is above (deep to) the perineal membrane in the urogenital t...
The paired deep transverse perineal muscles (TA: musculus transversus profundus perinei) lie in the perineum and are important for stabilizing the perineal body.
origin: ischial ramus
insertion: the fibers of each muscle meet in the midline at the perineal body and decussate to intert...
A delayed nephrogram, commonly described on plain film urography, but also visible on CT urography, is when there is absence or reduction of the normal renal parenchymal enhancement on nephrographic phase images.
A delayed nephrogram is characteristically unilateral and is usually ...
The detrusor muscle (or detrusor urinae muscle)is the smooth muscle component of the urinary bladder and facilitates contraction of the bladder wall during micturition.
Forms the smooth muscle component of the bladder wall. The urothelial lining overlies it within the bladder cav...
Developmental anomalies of the kidneys and ureters are numerous and not only potentially render image interpretation confusing but also, in many instances, make the kidneys more prone to pathology:
horseshoe kidney: most common
cross fused ...
Diabetes insipidus (DI) is the deficiency or resistance to the hormone vasopressin (antidiuretic hormone), which results in polyuria and polydipsia.
DI occurs in 3 per 100,000 people 2.
DI may be described as 1-3:
central/neurogenic/hypothalamic: vasopressin deficie...
The dialysis disequilibrium syndrome (DDS) is a situation characterized by development of neurological symptoms following the rapid removal of urea during hemodialysis. It develops primarily from an osmotic gradient that develops between the brain and the plasma as a result of rapid haemodialysi...
Diverticula are outpouchings of a hollow viscus and can be either true or false.
Occasionally a diverticulum is used in a more general sense to mean the outpouching of other anatomical structures, e.g. frontal intersinus septal cells are hypothesized to form as diverticula from the frontal sinu...
Dorsal nerve of penis or clitoris is one of the two terminal branches of the pudendal nerve that arises from nerve whilst in the pudendal canal. The other terminal branch is the perineal nerve.
Entering the urogenital triangle of the perineum, the dorsal nerve of penis o...
Double contrast cystography (pneumocystography) is an older technique to evaluate the bladder lumen. It has rarely been used (if ever) after the advent of cross-sectional imaging.
The exam is performed similarly to a conventional cystogram, but gas is also introduced through the Foley catheter....
Double retroaortic left renal vein is a very rare entity that is usually clinically silent and detected incidentally at imaging, surgery, or autopsy.
The knowledge of anatomical variations helps the surgeon or interventionist to avoid complications during surgery and interventional procedures 4...
Drash syndrome, also known as the Denys-Drash syndrome, is associated with an abnormal WT1 gene (Wilms tumor gene) and consists of:
Dromedary humps are prominent focal bulges on the lateral border of the left kidney. They are normal variants of the renal contour, caused by the splenic impression onto the superolateral left kidney.
Dromedary humps are important because they may mimic a renal mass, and as such is considered a...
The drooping lily sign is a urographic sign in some patients with a duplicated collecting system. It refers to the inferolateral displacement of the opacified lower pole moiety due to an obstructed (and unopacified) upper pole moiety.
The similarity to a lily is further strengthened by the smal...
The drooping moustache sign refers to the appearance caused on axial pelvic MR images by posterior prolapse of the fat in the retropubic space, akin to the drooping corners of a moustache, due to loss of integrity of the urethral suspensory ligaments and level 3 endopelvic fascia.
Drug-induced renal calculi are a subtype of renal calculi, whereby the stone formation is related to the patient's medication.
Two main types of drug-induced calculi are described:
Overall drug-induced urolithiasis accounts for 1-2% o...
The ductus deferens (plural: ductus deferentes) forms part of the male internal genitalia where it transports sperm from the epididymis to the ejaculatory duct. In modern anatomic nomenclature, it is no longer referred to as the vas deferens (plural: vasa deferentia).
The ductus ...
Calcification of the ductus deferens can result from:
diabetes mellitus 4 - most common
chronic infection - more frequently irregular; unlike diabetic calcification, inflammatory calcification tends to be unilateral and segmental 3
A ductus deferens cyst (also known as a vas deferens cyst) is a type of juxtaprostatic - extraprostatic cyst. They are usually located along the course of the ductus deferens and superior to the prostate. They can arise from congenital abnormalities of the vas deferens or acquired causes such as...
A duplex collecting system, or duplicated collecting system, is one of the most common congenital renal tract abnormalities. It is characterized by an incomplete fusion of upper and lower pole moieties resulting in a variety of complete or incomplete duplications of the collecting system. While ...
Dynamic contrast enhancement (DCE) MRI is a component of a multiparametric MRI approach for evaluating the extent of primary and recurrent prostate cancer.
Protocol and equipment
Typically 3D T1-weighted fast spoiled gradient-echo MRI sequences are used to repeatedly image a volume of interes...
Echogenic renal pyramids in children can be due to many different causes.
Iatrogenic (most common cause)
An ectopic kidney, also known as renal ectopia, is a congenital renal anomaly characterized by the abnormal location of one or both of the kidneys.
They can occur in several forms:
cross fused renal ectopia
ectopic thoracic kidney
The estimated incidence of an ec...
Ectopic testes are a rare congenital anomaly, differing from undescended testis (cryptorchidism) in that ectopic testis is a congenitally abnormally located testis, that has descended from the abdominal cavity away from the normal path of descent while undescended testis are congenitally abnorma...
An ectopic ureter is a congenital renal anomaly that occurs as a result of abnormal caudal migration of the ureteral bud during its insertion to the urinary bladder. Normally the ureter drains via the internal ureteral orifice at the trigone of the urinary bladder.
In females, the most common ...
The ejaculatory ducts are paired structures of the male reproductive system and convey seminal fluid.
Each ejaculatory duct is formed by the union of the excretory duct of the seminal vesicle and the ampulla of the ductus deferens and is approximately 2 cm long. The ducts course ...
Ejaculatory duct cysts are a rare type of cyst of the prostate gland.
They occur due to obstruction of the ejaculatory duct which in turn can either be congenital or secondary (e.g. inflammation).
They are usually intraprostatic when small but may extend cephalad when large.
Ejaculatory duct obstruction refers to the congenital or acquired obstruction of the ejaculatory ducts.
Ejaculatory duct obstruction is rare, accounting for approximately 5% of infertile patients, but thought to be underdiagnosed 2.
Patients may complain ab...
A useful mnemonic to remember the ejaculatory pathway of sperm is:
S: seminiferous tubules of the testes
V: vas (ductus) deferens
E: ejaculatory duct
Emphysema refers to any disease process involving an abnormal accumulation of air/gas in the tissues. When used alone, it is usually taken to mean the lung disease, pulmonary emphysema, which forms part of the spectrum of chronic obstructive pulmonary disease (COPD).
gastric emphysema: include...
Emphysematous cystitis refers to a gas-forming infection of the bladder wall.
The condition is rare and usually confined to certain patient subgroups. Median age affected is 66 years. More common in women, 2:1 F:M 9.
Risk factors include:
Emphysematous epididymo-orchitis is a rare gas-forming epididymo-orchitis. The pathology of this condition is unknown. The diagnosis is usually made by ultrasonography with CT as an adjunct, to confirm the diagnosis, evaluate its extent and to rule out a coexistent retroperitoneal infective focu...
Emphysematous prostatitis refers to gas-forming infection of the prostate, nearly always occurring concurrently with prostatic abscess.
The condition is rare, most commonly presenting in males aged 50-70 years and usually confined to certain patient subgroups 1,2.
Emphysematous pyelitis is isolated gas production inside the excretory system, secondary to acute bacterial infection. It is a relatively benign entity and needs accurate differentiation from the far more serious emphysematous pyelonephritis, which is gas production from an infection in the rena...
Emphysematous pyelonephritis (plural: emphysematous pyelonephritides) refers to a morbid infection with particular gas formation within or around the kidneys. If not treated early, it may lead to fulminant sepsis and, therefore, carries a high mortality.
The patient usual...
Empyemas are purulent inflammatory collections within a body cavity. Contrast this with abscesses, which arise within parenchymal tissue, rather than occupying a pre-existing anatomical space.
Colloquially, the standalone term empyema is used to refer to thoracic empyemas but there...
Endometrial carcinoma staging allows appropriate treatment options to be considered and enables greater prognostic accuracy for endometrial carcinoma.
Staging can be based on the TNM or FIGO system.
MR imaging is the modality of choice for staging with CT having relatively low speci...
The endopelvic fascia is the enveloping connective tissue network for the pelvic viscera, suspending, supporting and fusing the pelvic organs to the arcus tendineus fasciae pelvis, which itself inserts onto the pelvic sidewalls and pubic bones.
The major anterior component is the pubovesical li...
End-stage kidney disease (ESKD), also referred as end-stage renal failure, corresponds to the last stage of chronic kidney disease (stage 5), when the kidneys' function is no longer sufficient to sustain life (GFR <15 mL/min/1.73m2) and kidney replacement therapy (dialysis or transplant) is requ...
Eosinophilic ureteritis (and eosinophilic pyelouerteritis) is a rare cause of ureteral inflammation. The clinical presentation and imaging features are non-specific.
Patients are usually atopic or hypereosinophilic with peripheral eosinophilia.
Associated with eosinophil...
Epidermoid cysts are nonneoplastic inclusion cysts derived from ectoderm that are lined solely by squamous epithelium. These are discussed separately by anatomic location:
epidermal inclusion cyst
intracranial epidermoid cyst
splenic epidermoid cyst
spinal epidermoid cyst
An epididymal abscess is an uncommon complication of epididymitis.
Causative organisms are the same that cause epididymitis:
Other rare etiological agents
Epididymal appendices, also known as appendix of the epididymis or appendix epididymis, are an testicular appendage found at the head of the epididymis 1. They represent a developmental remnant of the mesonephric duct (Wolffian duct). In 78% of the cases, it has a stalk configuration and is thus...
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 cysts are the most common epididymal mass.
Epididymal cysts have been reported in ~30% (range 20-40%) of asymptomatic individuals 5.
They are usually of lymphatic origin 2. The cysts contain clear serous fluid, lymphocytes, spermatozoa and debris.
Epididymal leiomyomas (fibrous pseudotumors) are uncommon smooth muscle tumors that do not have malignant potential. Their imaging features are not specific and, if small, it may be a difficult prospective diagnosis on imaging. They are usually encountered in a differential for epididymal/parate...
Epididymal lesions are most commonly encountered on ultrasonography. Most epididymal lesions are benign; malignant lesions are rare.
They can comprise of
Benign solid lesions
adenomatoid tumor of the scrotum: most common epididymal mass 4
papillary cystadenoma of the e...
The epididymis (plural: epididymides) is situated adjacent to the testis within the scrotal sac. Its primary function is the collection, maturation and transport of sperm via the ductus deferens.
The epididymis is an elongated structure, posterolateral to the testis. It can be su...
Epididymitis refers to inflammation of the epididymis and may be associated with inflammation extending to the testis itself, in which case the term epididymo-orchitis is used. This should be distinguished from isolated orchitis, which is by comparison much less common.
Epispadias is a rare congenital anomaly that is almost always associated with bladder exstrophy.
It occurs in 1 in 30,000 births, with a male: female ratio of 3:1.
The roof of the urethra is absent and the urethra opens anywhere between the base and the gl...
Epithelioid angiomyolipomas (EAML) are rare variants of the more common renal angiomyolipoma. They have malignant potential.
Like more common renal angiomyolipomas, EAMLs are considered perivascular epithelioid cell tumors (PEComas). EAMLs were regarded as a separate renal mass entit...
The erased charcoal sign describes the typical appearance of focal prostate cancer in the transition zone characterized as homogeneous hypointensity on T2WI with ill-defined borders, akin to a charcoal pencil drawing smudged with an eraser, often with a lenticular or waterdrop-like shape.
Erectile dysfunction is a common condition. Doppler ultrasound is a highly accurate means of assessing patients with erectile dysfunction.
Psychological factors (mental impulse) cause transmission of parasympathetic impulses to the penis. This causes relaxation of arterioles and cor...
The estimated glomerular filtration rate (eGFR) is widely used as a surrogate marker of renal function and is mathematically-derived from the patient's serum creatinine, using their age, sex and ethnicity.
The eGFR is calculated using a four variables Modification of Diet in Renal...
The external iliac lymph nodes can be found surrounding the external iliac artery and act as the draining nodes for several regions of the pelvis and lower limb.
The external iliac lymph nodes lie anterior to the internal iliac lymph nodes and usually form three separate subgrou...
Extra-adrenal myelolipomas are extremely rare myelolipomas that occur outside the adrenal glands, with the most common sites being the retroperitoneum (especially presacral region), perirenal space and the thorax.
The exact incidence is unknown. Less than 60 reported cases were re...
Extracorporeal shock wave lithotripsy (ESWL) is a common non-invasive treatment for urolithiasis, and less commonly for pancreatic or salivary ductal stones 4. It is less successful in obese patients and with stones >2 cm. Children respond equally well or better to ESWL than adults 5.
Extramammary Paget disease (EMPD) is the rarer non-breast form of Paget disease of the nipple. It is considered a form of adenocarcinoma of the apocrine glandular tissue. In men, the penis and scrotum are most frequently involved, and in women the vulva. Nodal and distant organ metastatic diseas...
Extraprostatic (extracapsular) extension of prostate cancer refers to local tumor growth beyond the fibromuscular pseudocapsule of the prostate gland into the periprostatic soft tissues, in particular, the periprostatic fat and is an established adverse prognostic factor and of importance for pr...
Extrapulmonary tuberculosis (TB) refers to the hematogenous spread of Mycobacterium tuberculosis.
Extrapulmonary tuberculosis can occur as a primary form of the disease, i.e. direct infection of an extrapulmonary organ without the presence of primary pulmonary tuberculosis or it can ...
Extrarenal pelvis refers to the presence of the renal pelvis outside the confines of the renal hilum; it is a normal anatomic variant.
It is found in ~10% of the population 2.
An extrarenal pelvis usually appears dilated, erroneously suggesting...
The differential diagnosis for extratesticular cystic lesions includes:
loop of bowel from an inguinal hernia
Very rarely, a scrotal mesothelioma may present as a cystic mass.
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...
A faceless kidney refers to one in which the normal appearance of the renal sinus on cross-sectional imaging is absent. It was initially described as a sign of duplication of the collecting system 1 (a slice obtained between the two collecting systems will not demonstrate the normal components o...
The falling snow sign describes the appearance of movement of internal echoes in spermatoceles away from the transducer, resulting in an appearance similar to falling snow when color Doppler is applied. The sign can be used to aid in the diagnosis of a spermatocele.
The eponym Fallopian may refer to:
Fallopian canal (facial nerve canal)
Fallopian tube (uterine duct)
Fallopian ligament (inguinal ligament)
History and etymology
It is named after Gabriele Falloppio (also known by his Latin name Fallopius), Italian anatomist (1523-1562).
Fanconi syndrome describes generalized proximal renal tubule dysfunction causing impaired reabsorption of many urinary solutes.
Clinical features include poor growth, fatigue, dehydration, polyuria, muscle weakness, and bone pain. Features on a basic blood panel include ...
There are numerous fat-containing renal lesions, including:
renal cell carcinoma (often has calcifications when contains macroscopic fat)
renal or perirenal lipoma/liposarcoma
Non-mass lesions may also occasionally contain fat:
Female prostate sign is a characteristic imaging sign seen in patients with a large urethral diverticulum.
A large urethral diverticulum in females surrounds the urethra, and elevates the base of the bladder, mimicking the typical appearance of enlarged prostate in males.
Female pseudohermaphroditism (FPH) is a form of disorder of gender development.
Patients with female pseudohermaphroditism have female internal genitalia and female karyotype (46 XX) with various degree of external genitalia virilization.
congenital adrenal hyperplasia (CA...
The female urethra is a simple short tube, that transports urine out of the body, extending from the internal urethral orifice of the bladder to the external urethral orifice in the vestibule of the vagina.
The female urethra measures approximately 4 cm in length. It is embedded...
Fetal cystic renal disease can be in included in three of the four types classified according the system by Osathanondh and Potter 1:
Potter type I: infantile polycystic kidney disease
Potter type II: multicystic dysplastic kidneys
Potter type III: adult polycystic kidney disease
A fetal hydrocele refers to a hydrocele present in utero.
They may be sonographically identified in ~15% of male fetuses in the third trimester 6.
Often result from a patent processus vaginalis. They are more frequently unilateral.
Fetal hydronephrosis represents the abnormal dilatation of the fetal renal collecting system, with pelviureteric junction obstruction the most commonly encountered cause.
Please, refer to the article on fetal pyelectasis for a dedicated discussion on this relatively common and usually benign f...
Fetal megacystis refers to the presence of an unusually large bladder in a fetus.
The estimated incidence of antenatal imaging is at ~1:1500 pregnancies.
It can result from a number of causes but the main underlying mechanism is either distal stenosis or reflux.
Fetal pyelectasis refers to the 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 a...
A fetal urachal cyst refers to a urachal cyst occuring in utero. It may or may not communicate with the vertex of the fetal bladder. It may also arise within the umbilical cord. Umbilical cord urachal cysts originate from an extra-abdominal urachal system.
fetal intra-abdominal cysts...
Fetal urinary ascites is one of the causes of fetal ascites and can arise from a number of pathologies:
in utero bladder perforation
transudation from the fetal bladder
persistent urogenital sinus
The presence of fetal ascites without fe...