The dialysis disequilibrium syndrome (DDS) is a situation characterized by development of neurological symptoms caused by 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 haemodialysis. I...
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...
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 - 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.
A useful mnemonic to remember the ejaculatory pathway of sperm is:
S: seminiferous tubules of the testes
V: vas (ductus) deferens
E: ejaculatory duct
Emphysematous cystitis (EC) 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 rarely reported entity with only a handful of case reports. It is reported as a rare cause of acute scrotum encountered in poorly controlled diabetics. The pathology of this condition is unknown with few possible hypotheses postulated. The diagnosis is usual...
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 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 usually presents with fevers and flank pain. I...
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...
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 masses are most commonly encountered on ultrasonography. Most epididymal masses are benign; malignant lesions are rare.
adenomatoid tumor of the scrotum (most common epididymal mass 4)
sperm granulomas / post vasectomy gran...
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.
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...
Extracorporeal shock wave lithotripsy (ESWL) is a common non-invasive treatment for urolithiasis. It is less successful in obese patients and with stones >2 cm.
steinstrasse: incomplete fragmentation that results in a pile-up of stone fragments that obstruct the ureter
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 disease...
Extraprostatic (extracapsular) extension of prostate cancer refers to local tumor growth beyond the fibromuscular band surrounding the prostate gland. It is a pathological finding important to prostate cancer staging.
Though imperfect, MRI is superior to transrectal ultra...
Extrapulmonary tuberculosis (TB) refers to the haematogenous spread of Mycobacterium tuberculosis.
Extrapulmonary tubercuosis 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
renal or perirenal lipoma/liposarcoma
Non-mass lesions may also occasionally contain fat:
renal junction line
fat in a renal scar
renal sinus lipomatosis
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 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 ...
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...
Fibromuscular dysplasia (FMD) is a heterogeneous group of vascular lesions characterized by an idiopathic, non-inflammatory, and non-atherosclerotic angiopathy of small and medium-sized arteries.
The prevalence is unknown 7. It is most common in young women with a female to male r...
Fibrous pseudotumor of the scrotum is a relatively rare, non-neoplastic extratesticular non-epididymal lesion.
It affects any age. Although rare, it is considered the third most common extra testicular mass after a scrotal lipoma and an epididymal adenomatoid tumor.
The filarial dance sign refers to a twirling motion of microfilariae (e.g. W. bancrofti) in dilated lymphatic channels. It is identified as a characteristic sign of scrotal filariasis.
The dilated channels are identified with the absence of color flow on color Doppler study and the microfilari...
Filariasis refers to infection with nematodes (roundworms) of the family Filarioidea. There are three species of these thread-like filarial worms:
Wuchereria bancrofti: responsible for 90% of cases
Brugia malayi: causes most of the remainder of cases
Brugia timori: an uncommon cause
It can a...
The Finnish type congenital nephrotic syndrome is a sub type of congenital nephrotic syndrome. A large placenta and proteinuria from birth are considered hallmarks of the disease 2. The proteinuria is often of intra-uterine onset. Although it is named the Finnish type, it can occur outside Finla...
Fishhook ureters, also known as J-shaped ureters or hockey stick ureters describe the appearance of the distal ureter in patients with significant benign prostatic hypertrophy. It has also been used to describe the appearance of a retrocaval ureter in type 1 or low loop variety. As the right ur...
A fistula (plural: fistulae) is an abnormal connection between two epithelial surfaces such as between hollow organs, skin or vessels. Conventionally, the name of a specific fistula type is a combination of the two organs
For discussions of specific fistulae please refer to individual articles....
Fluorine-18-labeled sodium fluoride (also known as 18F-NaF or sodium fluoride) is a PET radiotracer used primarily for skeletal imaging.
Fluorine-18-labeled sodium fluoride is an ionic compound comprised of a single sodium atom bound to a positron-emitting isotope of fluorine.
The Foley catheter is a urinary catheter with a balloon at its distal tip, which is inflated post-insertion to ensure that the catheter remains in the bladder. Originally inflation of the balloon required the instillation of fluid or air via a separate port, next to the external end of the cathe...
The term fornix (plural: fornices) is used for anatomical structures in multiple organ systems that all share an arch-like morphology:
History and etymology
Fornix is Latin for...
The fossa navicularis refers to a normal mild dilatation of the urethra. It occurs at the most distal/downstream portion of the urethra.
It is more evident in males, where it occurs in the penile/pendulous urethra, near the urethral meatus. There is also a fossa navicularis in women: the more f...
The fountain sign is sonographic sign described in acute idiopathic scrotal edema (AISE).
It refers to the appearance of the pattern of vascularity seen during transverse color Doppler sonography of the scrotum with both testes together 1. In these transverse views in patients with AISE, marked...
Fournier gangrene is necrotizing fasciitis of the perineum. It is a true urological emergency due to the high mortality rate but fortunately, the condition is rare.
Fournier gangrene is typically seen in diabetic men aged 50-70 years, rarely in women. Other predisposing factors in...
Fraley syndrome is the eponymous term for a dilated calyx (hydrocalyx) due to compression of a calyceal infundibulum from an adjacent artery or vein. It is rare, but it occurs more often in an upper pole calyx. The hydrocalyx may be painful.
The free/total PSA ratio (%fPSA) is an additional new parameter used in assessing PSA levels. Some authors 1,2 recommend that men with PSA levels of 4.1 to 10 ng/mL who are not suspected of having prostate cancer by whatever means should undergo %fPSA measurement and then be carefully monitored ...
Frenulum (plural: frenula) is an anatomical term and refers to a small fold of soft tissue that checks the movement of an anatomical part.
frenulum (ileocecal valve)
frenulum (labia minora)
History and etymology
Frenulum derives from ...
Frozen pelvis refers to a condition in which pelvic organs are distorted and tethered to each other as a consequence of adhesive processes.
It is commonly seen in endometriosis. Other causes include tumors, infections including pelvic inflammatory disease, post-surgical adhesions and post-treat...
Fungal balls of the urinary tract, also known as fungal bezoars or mycetomas of the urinary tract, are a rare manifestation of funguria, usually candiduria.
While candiduria may be seen in approximately 20% of hospitalized patients 1, development of fungal balls is considered very...
Ganglioneuromas are fully differentiated neuronal tumors that do not contain immature elements and potentially occur anywhere along the peripheral autonomic ganglion sites.
On imaging, usually, they present as well-defined solid masses and can be quite large at presentation. Generally, they ar...
There are numerous causes of gas in the urinary bladder. In the hospital setting by far the most common is the recent placement of an indwelling urinary catheter. Other causes include 1:
indwelling urinary catheter is by far the most common cause
Genitourinary tuberculosis is the second most common site of infection in humans by Mycobacterium tuberculosis, second only to pulmonary tuberculosis.
It can most easily be divided anatomically into:
renal tuberculosis (renal parenchyma, calyces and renal pelvis)
bladder and ureteric tubercu...
Germ cell tumors are classified into two broad groups: seminoma and non-seminomatous germ cell tumors (NSGCT). The later is then divided further according to histology.
non-seminomatous germ cell tumors (NSGCT)
yolk sac tumor...
Germ cell tumors are found widely throughout the body, and encompass a wide range of individual tumors.
This article does not deal with any specific body locations. For detailed discussion please refer the articles listed at the end of this page.
Germ cell tumors arise from ectopic...
A mnemonic for the differential diagnosis for germ cell tumors is:
E: embryonal cell carcinoma
E: endodermal sinus tumor (yolk sac tumor)
Germinoma is a term that if unqualified, usually refers to a tumor of the brain but can also refer to similar tumors of other regions particularly the ovary and testis.
dysgerminoma of the ovary
seminoma of the testis
CNS germinoma: see WHO classification of CNS tumors
All these tumors share...
The histological grading of prostate cancer has undergone many revisions, and for many years the primary system was the Gleason score, itself derived from the Gleason grade. In 2014, the Grade Group was introduced, and care must be taken to not confuse this with the Gleason grade.
The Gleason g...
Global testicular infarction is fortunately rare, and is most commonly seen in the context of testicular torsion. However rarely it can occur secondary to other causes.
surgery, e.g. inguinal hernia repair 7
Glomerulocystic disease (GCK) is a rare cystic kidney disease.
Histopathology typically shows normal-sized glomeruli with the enlarged Bowman’s space and tubular cystic changes. A proposed mechanism of glomerular cyst development is stenosis at the glomerulot...