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
A gasless abdomen refers to a paucity of gas on abdominal radiography, and the specific cause can usually be identified when the patient's history is known. Common causes include:
small bowel obstruction
Gastric outlet obstruction is a syndrome resulting from mechanical obstruction of stomach emptying.
Gastric outlet obstruction can be due to malignant or benign causes.
adenocarcinoma (second most common 4)
lymphoma (less common than other malignancies as...
The causes of generalized increase in bone density in adult patients, also known as generalized or diffuse osteosclerosis, can be divided according to broad categories:
marrow cavity is narrowed by endosteal new bone
patchy lucencies due to the persist...
The causes of generalized increased bone density in pediatric patients can be divided according to a broad category of causes:
dense metaphyseal bands
cortex and flat bones may also be slight...
Causes of generalized increased liver echogenicity include:
diffuse fatty infiltration
cirrhosis: can be coarsened as well
chronic hepatitis 3: can be coarsened as well
diffuse infiltration or deposition
Generalized osteopenia refers to osteopenia diffusely affecting the bones.
The differential diagnosis is wide and includes:
osteoporosis: decreased osteoid production
osteomalacia: undermineralisation of osteoid
The list of causes of a generalized periosteal reaction overlaps that of symmetrical periosteal reaction, and includes 1,2:
vascular stasis (common)
infantile cortical hyp...
Causes of generalized reduction of liver echogenicity on ultrasound include:
diffuse malignant infiltration
generalized increase in liver echogenicity
hepatic attenuation on CT
A gibbus deformity is a short-segment structural thoracolumbar kyphosis resulting in sharp angulation.
There are a number of causes which can be divided into congenital and acquired.
cretinism (congenital hypothyroidism)
Gracile bones refer to changes in the skeleton in which the bones are more slender than usual (over-tubulated) and occasionally deformed in other ways such as being abnormally curved. This may occur in a number of disorders and can occur with or without fractures.
Granular mucosal pattern of the esophagus represents very fine nodularity of the esophageal mucosal surface. This finding is non-specific and may represent:
reflux esophagitis (most common)
superficial spreading esophageal carcinom...
Granulomatous lung disease refers to a broad group of infectious and non-infections conditions characterized by the formation of granulomas.
The spectrum includes
pulmonary non-tuberculous mycobacterial infection
Ground-glass opacification/opacity (GGO) is a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings. It is a non-specific sign with a wide etiology including infection, chronic interstitial disease an...
The term grouped calcifications is used in mammography when relatively few breast microcalcifications reside within a small area. There must be at least five calcifications present within 1 cm of each other 3. At the most, it may refer to a larger number of calcifications present within 2 cm of ...
Gynecomastia refers to a benign excess of the male breast tissue, that is usually reversible. It is not a risk factor per se for developing male breast cancer.
While it can occur at any age, it tends to have greater prevalence in two groups: adolescent boys and older men (some pub...
Gyral enhancement, also known as gyriform, cortical, or grey matter enhancement, is a pattern of contrast enhancement in the superficial brain parenchyma that conforms to the serpentine morphology of the cerebral gyri. It should be distinguished from leptomeningeal enhancement, which is also ser...
Hematospermia (less commonly hemospermia) refers to the presence of blood in semen or ejaculatory fluid. It is a symptom that can cause great anxiety in patients despite usually being of benign etiology.
urogenital infections including sexually transmitted disease, ...
Hemobilia refers to the presence of blood in the biliary tree.
The classical clinical triad, only seen in ~50% of cases, consists of:
melena (i.e. upper gastrointestinal bleeding)
iatrogenic: surgical or percutaneous proced...
Hemolytic anemia is a form of anemia where red blood cells (RBCs) are destroyed either intravascularly or extravascularly.
The patient presents with anemia and jaundice. Diagnosis is based on several laboratory parameters 1:
increased unconjugated biliru...
Hemopericardium refers to the presence of blood within the pericardial cavity, i.e. a sanguineous pericardial effusion. If enough blood enters the pericardial cavity, then a potentially fatal cardiac tamponade can occur.
There is a very long list of causes 1,4 but some of ...
Hemoperitoneum (plural: haemoperitoneums) is the presence of blood within the peritoneal cavity.
penetrating or non-penetrating abdominal trauma (often with associated organ injury) 1
ruptured ectopic pregnancy
ovarian cyst rupture
aneurysm or pseudoaneurysm rupture
A hemopneumothorax (plural: hemopneumothoraces) (or, less commonly, haematopneumothorax or pneumohemothorax) is a term given when there is concurrent presence of a hemothorax and pneumothorax. It is a variant of a hydropneumothorax.
Approximately 5% of patients with pneumothorax ...
Hemoptysis (plural: hemoptyses) refers to coughing up of blood. Generally, it appears bright red in color as opposed to blood from the gastrointestinal tract which appears dark red. It is considered an alarming sign of a serious underlying etiology.
Massive hemoptysis is referred t...
Hemorrhagic intracranial metastases are considered to represent between 3-14% of all cerebral metastases (cf. 1-3% of gliomas are hemorrhagic).
These classically originate from:
renal cell carcinoma
thyroid carcinoma: papillary carcinoma of the thyroid has the highe...
A hemothorax (plural: hemothoraces), or rarely hematothorax, literally means blood within the chest, is a term usually used to describe a pleural effusion due to accumulation of blood. If a hemothorax occurs concurrently with a pneumothorax it is then termed a hemopneumothorax.
A tension hemot...
There are many thoracic complications that can occur following hematopoietic stem cell transplantation. These can precipitate during various stages following transplantation and can be either infectious or noninfectious.
Complete white-out of a hemithorax on the chest x-ray has a limited number of causes. The differential diagnosis can be shortened further with one simple observation: the position of the trachea. Is it central, pulled or pushed from the side of opacification? Is there pulmonary volume loss or vo...
Hepatic attenuation on CT, reflected by Hounsfield values, depends on a combination of factors including the presence or absence, as well as the phase, of IV contrast administration.
Allowing for all these factors, the mean unenhanced attenuation value is around 55 HU 4.
Hepatic vascular and perfusion disorders are a broad group of conditions that radiologists should be familiar with, as some of them are quite frequently seen in the daily practice. The aim of this article is to be a collection of articles that represent the core knowledge in the matter.
Hepatolithiasis is the presence of bile duct stones within the intrahepatic bile ducts, specifically before the confluence of the right and left hepatic ducts.
Hepatolithiasis is common in Asia and the Pacific, with a prevalence of ~40%. It is rare in the West with a prevalence o...
Hepatosplenomegaly is simply the simultaneous presence of a pathologically-enlarged liver (hepatomegaly) and spleen (splenomegaly).
Many, many infections can produce a mild concurrent enlargement of the liver and spleen. This list is by no means exhaustive!
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 (also associated with angiomyolipoma)
Heterogeneous echogenicity of the thyroid gland is a non-specific finding and is associated with conditions diffusely affecting the thyroid gland. These include:
Hiccups (or hiccoughs), medical term singultus (rarely used), are an unpleasant phenomenon, experienced by everyone on occasion, and usually self-limiting. However the much rarer intractable chronic form can be extremely debilitating.
Hiccups are a symptom that has probably been e...
High arched palates are a facial feature of many syndromes, although the classic association is Marfan syndrome. There are hundreds of conditions associated with high arched palates, with some of the radiologically-more important including:
High attenuation lymphadenopathy (or adenopathy) variably refers to abnormal lymph nodes with attenuation on CT usually higher compared to muscle, either on a noncontrast exam or following contrast administration (i.e., hyperenhancement) 5.
High attenuation nodes may be due to calcifications or...
A high bone mineral density is one where the bone mineral density (BMD) is usually greater than two standard deviations above what is expected for age. This can sometimes be seen on routine DXA scan assessment. Some authors advocate a definition of a high BMD where the Z-score is >+2.5 to highli...
High output cardiac failure refers to a state of cardiac failure that is associated with a higher than normal cardiac output which is still not sufficient for body tissue demands.
Patients can present with a number of symptoms of varying degrees which include tachycardia,...
A high-riding shoulder refers to the superior displacement/subluxation of the humeral head with resultant decrease in the acromiohumeral distance.
The differential for a high-riding shoulder is:
rotator cuff tear with or without rotator cuff arthropathy
The term high-risk breast lesion is given to a breast lesion that carries an increased risk for the future development of breast cancer or carries suspicion of a more sinister pathology around or in association with the lesion. The term has some overlap with borderline breast disease. Many radio...
Cardiovascular manifestations are seen with increased frequency in the HIV/AIDS adult population, and include:
dilated cardiomyopathy (prevalence 8-30%)
endocarditis: either infective or non-bacterial thrombotic (marantic) which is associated with malignancy or HIV wasti...
The CNS manifestations of HIV/AIDS (neuroAIDS) occur secondary to a wide range of neurodegenerative, infectious, inflammatory, or neoplastic processes.
Since the introduction of highly active antiretroviral therapy (HAART) in 1996, there has been a shift in the epidemiology of CN...
Gastrointestinal manifestations of AIDS are protean and can be broadly divided into opportunistic infections and tumors:
herpes simplex virus (HSV)
primary infection with HIV
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:
Musculoskeletal manifestations of HIV/AIDS are not as common as CNS or pulmonary complications. Nonetheless, their prevalence is high.
Depending on the condition, etiology may be related to the HIV infection itself, the resultant immunodeficiency, or antiretroviral therapy (HAART).
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:
Holocord presentation refers to a process which involves the spinal cord, from cervicomedullary junction to the tip of the conus. It does not relate to a specific condition nor does it distinguish between involvement by cystic expansion or solid tumor, or by a combination of both. It merely deno...
Distinguishing primary hydrocephalus from atrophy resulting in compensatory enlargement of the CSF spaces as the cause of ventriculomegaly can be, at times, challenging in image interpretation.
Features that favor hydrocephalus include:
dilatation of the temporal horns
Hydronephrosis (plural: hydronephroses) is defined as dilatation of the urinary collecting system of the kidney (the calyces, the infundibula, and the pelvis) 1.
Hydronephrosis in fetuses and newborns has specific causes that are covered in a separate article.
The term hydroureter...
Hydroxyapatite crystal deposition disease (HADD) is a disease of uncertain etiology characterized by periarticular and intra-articular deposition of hydroxyapatite (HA) crystals.
The shoulder is the most frequently involved site with classic calcific tendinitis presentation.
Hyperattenuating cerebral metastases on CT can be due to hemorrhage, calcium, or highly cellular tumors.
There is overlap between the entities, with some cerebral metastases appearing in more than one list 1-6:
hemorrhagic cerebral metastases (mnemonic)
Hyperattenuating paranasal sinus opacification can arise in a number of situations:
fungal sinus disease
acute hemorrhage into sinus (hemosinus)
In some situations can consider early calcification within the sinus - intrasinus calcification.
Hyperattenuating pulmonary abnormalities refer to lung parenchymal opacities/lesions that are generally higher attenuation on CT than most soft tissues. An exact definition is usually not provided 1-3, while some authors focus on abnormalities that are as subjectively opaque as bony structures 4...
Hyperattenuating pulmonary consolidation refers to a region of lung parenchyma with air space opacification that has higher attenuation on CT than muscle or than expected with typical causes of consolidation such as pneumonia (fluid attenuation) or cancer (soft tissue attenuation).
There are only a few causes of a pulmonary mass with internal calcification. They include:
granuloma: most common
mucoid calcification of mucinous adenocarcinoma
gastrointestinal tract aden...
Hyperdense pulmonary nodules are a subset of pulmonary nodules that have relatively increased attenuation, usually caused by calcification within the nodule. Here, we broadly refer to a nodule as a pulmonary opacity <30 mm.
calcified pulmonary nodules are a specific grou...
There are a number of lesions that appear hyperechoic on ultrasound. Such lesions can be either completely or partly hyperechoic and include both benign and malignant entities.
fat containing breast lesions
lipoma of the breast
fibroadenolipoma (hamartoma) of the breast
Hyperostosis of the skull has many causes, broadly divided into focal or diffuse.
Paget disease of bone
metastatic disease, especially prostate carcinoma
chronic, severe anemia
hyperostosis frontalis interna
long-term phenytoin use
Hyperreninaemic hypertension may have many causes including:
renal artery stenosis
renal secreting tumor, e.g. renal cell carcinoma, reninoma
renal compression: large renal mass, subcapsular hemorrhage (Page kidney)
Hypertrophic osteoarthropathy (HPOA) is a syndrome characterized by periosteal reaction of the long bones without underlying bone lesion. There are a broad range of manifestations, although typically there is symmetrical involvement of the appendicular skeleton. Accompanying abnormal soft tissue...
Hypertrophy of the caudate lobe is seen in a number of conditions, including:
cirrhosis: most common
primary sclerosing cholangitis (end stage)
congenital hepatic fibrosis
cavernous transformation of the portal vein
The caudate-right lobe ratio m...
Hypervascular liver lesions may be caused by primary liver pathology or metastatic disease.
hepatocellular carcinoma (HCC)
most common hypervascular primary liver malignancy
early arterial phase enhancement and then rapid wash out
rim enhancement of c...
There are several tumors which are noted to cause hypervascular metastases. The list of differential diagnoses includes:
renal cell carcinoma (RCC)
breast cancer: homogeneously hypervascular liver metastases from breast are considered rare 3
Hypoglobus refers to the inferior displacement of the globe in the orbit. It may or may not be associated with enophthalmos.
fracture of the orbital floor (most common)
silent sinus syndrome
orbital foreign bodies
Hypomyelinating disorders are a heterogeneous subset of white matter disorders characterized by abnormally low amounts of myelination.
In distinction to other myelin disorders, hypomyelination is a permanent deficiency in myelin deposition rather than myelin destruction (i.e. demyelination) or ...
Hypotelorism refers to an abnormal decrease in distance between any two organs although some authors use the term synonymously with orbital hypotelorism meaning an abnormal decrease in the distance between the two eyes (the eyes appear too close together). The article mainly focuses on the latte...
Hypothalamic lesions are numerous representing some entities that are unique to the hypothalamus, as well as many lesions that can be seen elsewhere within the brain. Additionally, due to its proximity to the optic chiasm, third ventricle and pituitary region, many lesions of these locations can...
The idiopathic interstitial pneumonias (IIPs) are diffuse interstitial lung diseases of unknown cause. They are characterized by cellular infiltration of the interstitial compartment of the lung with varying degrees of inflammation and fibrosis.
Over the years many attempts have...
Iliac vein occlusion can be due to a variety of causes including:
catheter dissection injuries
IVC filter insertion
direct tumor invasion
enlarged lymph nodes
The incomplete border sign is useful to depict an extrapulmonary mass on chest radiograph.
An extrapulmonary mass will often have an inner well-defined border and an ill-defined outer margin 1-3. This can be attributed to the inner margin being tangential to the x-ray beam and has good inherent...
A generalized acceleration in bone maturation can result from a number of etiological factors. They include:
idiopathic isosexual precocious puberty
hypothalamic or parathalamic lesion with sexual precocity: e.g.
A mnemonic that can be used to remember the causes of increased heel pad thickness is:
D: phenytoin therapy
P: peripheral edema
Increased renal echogenicity is a non-specific finding but can represent a number of underlying conditions.
chronic kidney disease: increased cortical echogenicity
sickle cell disease 4
echogenic renal pyramids - pediatric
It is important to have a systematic way of approaching a case with subfertility in the exam.
Ultrasound is the initial examination of choice. Always say that you would further assess the uterus with 3D ultrasound. You may also say that in my department we would perform a sonohysterogram or HS...
Interstitial lung disease (ILD) is an umbrella term that encompasses a large number of disorders that are characterized by diffuse cellular infiltrates in a periacinar location. The spectrum of conditions included is broad, ranging from occasional self-limited inflammatory processes to severe de...
An interstitial lung pattern is a regular descriptive term used when reporting a plain chest radiograph. It is the result of the age-old attempt to make the distinction between an interstitial and airspace (alveolar) process to narrow the differential diagnosis.
A re-read of the timeless work o...
Intervertebral disc calcification is a non-specific finding seen in numerous conditions.
It may be observed in pediatric 5 as well as adult populations.
degenerative: relatively common and may occur in up to 6% of routine abdominal radiographs in adults
Intestinal failure is when a patient's native bowel is unable to digest and absorb the food, electrolytes, and fluids needed for normal growth and development.
This often includes intractable diarrhea, weight loss, dehydration, electrolyte imbalance, and malnutrition.
Intra-abdominal calcification is common and the causes may be classified into four broad groups based on morphology:
These are discrete precipitates in a vessel or organ. They are sharp in outline but the density and shape vary but in some cases they may be virtually pathognomonic:...
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 ...
Intra-articular gas or air (pneumarthrosis) can occur from a number of varied pathologies and should be interpreted according to the clinical context.
compound injury with gas entering from the outer surface
can occur in with a pneumolipohaemarthrosis
Intraconal orbital lesions are broadly divided into two main groups; those with or without involvement of the optic nerves:
Lesions with optic nerve involvement:
optic nerve glioma
optic nerve meningioma
lymphoma and leukemia
Intracranial arterial beading represents alternating areas of constriction in the intracranial arteries that gives the appearance of beads strung together.
The various conditions where this may be seen are:
cerebral vasospasm post...
Intracranial cystic lesions in the perinatal period can carry a relatively wide differential which includes:
Supratentorial cystic lesions
choroid plexus cyst
The following intracranial lesions may show high signal on diffusion-weighted imaging (DWI):
lesions with intense high signal
cytotoxic cerebral edema
intracranial epidermoid cyst
lesions with variable or moderately high signal
Intracranial metastases from non-CNS primary neoplasms are becoming more common due to significant advances in cancer treatment over the last few decades. Increasing numbers of patients live longer and present with metastasis in locations considered unusual previously:
brain (parenchymal) metas...
A variety of intracranial tumors exhibit different forms of calcification. Some lesions commonly show calcification while in some tumors, calcification is seen only in few number of cases. In this article these tumors are classified on the basis of frequency of calcification.
Intraductal papillary neoplasm of the bile duct (IPNB) is a pre-invasive biliary tree neoplasm considered to be a precursor of cholangiocarcinoma.
Biliary papillary adenoma and non-invasive papillary carcinoma of the biliary tract were terms used to refer to localized low-grade an...
Intraductal tubulopapillary neoplasms of the bile ducts are rare intraluminal mass forming pre-invasive biliary neoplasms with no mucin production.
ITPNs of the bile ducts are rare tumors of unknown incidence, found more frequently in women at their 60s 1,2.
Intradural extramedullary neoplasms are located outside the spinal cord but within the dural sheath.
The majority (70-80%) of spinal canal tumors are intradural extramedullary 1.
Patients present with signs and symptoms of spinal cord or nerve root compres...
Intrahepatic arteriovenous shunts, also referred to as intrahepatic arteriovenous malformations (AVMs) or hepatic arteriosystemic venous shunts, represent a spectrum of abnormal communications between the hepatic arterial system and the hepatic veins.
Please note that arterioportal shunts, whi...
Intralaminar dural hematomas in the intracranial space, are exceedingly rare, and represent hemorrhage between the two layers of the dura mater. As a result, it has distinctive features allowing it to be distinguished from extradural hematomas but mimics subdural hematomas. They are equivalent t...