The differential diagnosis of small bowel fold thickening is broad. Diffuse fold thickening may be "regular and smooth" or "irregular and nodular".
Regular, smooth generalized thickening
congestive cardiac failure (CCF)
Single layer (or lamellar) periosteal reaction is a uniformly dense, single thin layer of new bone about 1-2 mm from the cortical surface. It usually denotes an acute or subacute pathological process. Passive hyperemia causes increased osteoblastic activity and production of new bone.
Shortening of the fourth/fifth metacarpals (brachymetacarpia) and less commonly metatarsals (brachymetatarsia) is seen in a variety of apparently disparate conditions.
Common causes 2:
post-infective (e.g. osteomyelitis, yaws, tuberculosis dactylitis)
Glenohumeral instability is the tendency of the glenohumeral joint to sublux or dislocate due to loss of its normal functional or anatomical stabilizers.
Glenohumeral instability can be divided into:
lack of alignment at rest position, which can be depicted using...
Salivary gland tumors are variable in location, origin, and malignant potential.
In general, the ratio of benign to malignant tumors is proportional to the gland size; i.e. the parotid gland tends to have benign neoplasms, the submandibular gland 50:50, and the sublingual glands and...
Reverse bat wing pulmonary opacities refer to peripheral opacities of the lungs, sparing the perihilar region. It is a relatively unusual appearance with a fairly narrow differential 1:
chronic eosinophilic pneumonia
organizing pneumonia (formerly bronchiolitis obliterans with organizing pneum...
Pyometrium refers to infection of the endometrial cavity with resulting expansion due to accumulated pus (pyometra).
The postmenopausal demographic are most commonly affected due to the association with uterine malignancy.
endometritis / pelvic inflammatory disease
Peritoneal calcification is seen in a limited number of conditions that result in calcification of peritoneal structures. Therefore, the differential diagnosis is small:
psammoma bodies in malignancy (most frequently cystadenocarcinoma of the ovary): fine sand-like calcification
Periosteal reaction is a nonspecific radiographic finding that indicates new bone formation in reaction to the abnormal stimulants. Periosteal reactions may be broadly characterized as benign or aggressive, or more specifically categorized by pattern.
Periosteal reaction is the rec...
Pear-shaped (or teardrop-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 inc...
There are numerous primary pancreatic neoplasms, in part due to the mixed endocrine and exocrine components.
Classification based on function
exocrine: ~99% of all primary pancreatic neoplasms
pancreatic ductal adenocarcinoma ~90-95%
intraductal papillary muc...
Pediatric renal tumors 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 tumor: common in older children 1-8 years old
Omental cake refers to infiltration of the omental fat by material of soft-tissue density. The appearances refer to the contiguous omental mass simulating the top of a cake. Masses on the peritoneal surfaces and malignant ascites may also be present.
The most common cause is metasta...
Nodular filling defects due to mucosal lesions in the duodenum are due to a number of processes. For a differential list which includes non-mucosal lesions see duodenal filling defects.
The differential diagnosis for mucosal lesions includes:
heterotopic gastric mucosa
Nephrocalcinosis, previously known as Anderson-Carr kidney or Albright calcinosis, refers to the deposition of calcium salts in the parenchyma of the kidney. It is divided into several types, with differing etiologies, based on the distribution:
medullary nephrocalcinosis: 95%
Twin pregnancies are the most common multifetal pregnancies.
Multifetal pregnancies account for ~1% of all pregnancies but are seen in much higher numbers in populations where in vitro fertilisation (IVF) is a common practice.
A twin pregnancy can be broadly cate...
Multilayered periosteal reaction, also known as a lamellated or onion skin periosteal reaction, demonstrates multiple concentric parallel layers of new bone adjacent to the cortex, reminiscent of the layers on an onion. The layers are thought to be the result of periods of variable growth 2 and ...
The term miliary opacities refers to innumerable, small 1-4 mm pulmonary nodules scattered throughout the lungs. It is useful to divide these patients into those who are febrile and those who are not.
Additionally, some miliary opacities are very dense, narrowing the differential - see multiple...
There are a range of middle ear tumors, which are more likely to be benign than malignant.
The three most common middle ear tumors are (not in any particular order as there are differences in the literature) 1-3:
glomus tympanicum paraganglioma
Mandibular lesions are myriad and common. The presence of teeth results in lesions that are specific to the mandible (and maxilla) and a useful classification that defines them as odontogenic or non-odontogenic. While it may often not be possible to make a diagnosis on imaging alone, this classi...
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
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...
Hypervascular liver lesions are findings that enhance more or similarly to the background hepatic parenchyma in the late arterial phase, on contrast-enhanced CT or MRI.
hepatocellular carcinoma (HCC)
most common hypervascular primary liver malignancy
Hypertrophic osteoarthropathy (HOA) is a syndrome characterized by periosteal reaction of the long bones without an underlying bone lesion. There are a broad range of manifestations, although typically there is symmetrical involvement of the appendicular skeleton. Accompanying abnormal soft tiss...
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
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...
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...
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...
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
Erlenmeyer flask deformity (EFD), also known as metaphyseal flaring, refers to a radiographic appearance typically on a femoral radiograph demonstrating relatively reduced constriction of the diaphysis and flaring of the metaphysis as a result of undertubulation.
The name refers to the resembl...
Endobronchial metastases are an uncommon form of intrathoracic metastases. They are much less common than intrapulmonary metastases.
The clinical presentation varies and includes:
post-obstructive pneumonitis from distal obstruction
Empty gestational sacs can be due to a number of causes:
anembryonic pregnancy (also known as "blighted ovum")
early pregnancy (intrauterine): by 5.5 weeks gestational age, a yolk sac should be identifiable by transvaginal ultrasound
pseudogestational sac with an ectopic pregnancy
An elevated hemidiaphragm may result from direct and indirect causes which include:
above the diaphragm 1
decreased lung volume
prior lobectomy or pneumonectomy
phrenic nerve palsy
contralateral stroke: ...
Disorganized or complex periosteal reaction has spicules with random orientation and appearance. It is often seen in highly aggressive processes.
It has been associated with:
malignant fibrous h...
Erosion or absence of the distal ends of the clavicles may be seen in a wide range of conditions.
atraumatic distal clavicular osteolysis: due to repetitive microtrauma; classically described in weightlifters, but can affect anyone performing repetiti...
Discrete colonic ulcerations are nonspecific findings, and can be due to:
Erosion of the odontoid peg can result from a number of pathological entities:
rheumatoid arthritis: classic 1,2
systemic lupus erythematosus
calcium pyrophosphate arthropathy (CPPD): relatively common
non-inflammatory arthropathy: osteoar...
The differential diagnosis for multiple cystic neck lesions is different to that for a solitary cystic neck mass.
Cystic neck lesions are seen in:
metastatic squamous cell carcinoma: older patient, M>F
metastatic papillary thyroid carcinoma: usually a younger patient, ...
The differential for cystic lesions of the pancreas includes:
intraductal papillary mucinous neoplasm (IPMN)
serous cystadenoma uncommonly uni/macrolocular
simple pancreatic cyst
cystic neuroendocrine tumor of the pancreas
diffuse pancreatic cysts
The differential for cystic parotid lesions includes:
bilateral cystic parotid lesions
benign lymphoepithelial lesions of HIV
dysgenetic polycystic disease of salivary glands
unilateral cystic parotid lesion(s)
Cystic or necrotic appearing lymph nodes can be caused by a number of infectious, inflammatory or malignant conditions:
squamous cell carcinoma metastases
plasmacytoid T-cell leukemia
acute myeloid leukemia
herpes simplex lymphadenit...
The differential diagnosis for cystic masses of the mediastinum include:
foregut duplication cysts
esophageal duplication cyst
cystic teratoma of mediastinum
cystic degeneration of an intrathoraci...
Crazy paving refers to the appearance of ground-glass opacities with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT or standard CT chest. It is a non-specific finding that can be seen in a number of conditions.
Colonic strictures can be long (>10 cm) or short.
scirrhous colorectal carcinoma (apple core sign)
post surgical (anastamotic stricture)
scirrhous colorectal carcinoma
inflammatory bowel disease
A Codman triangle is a type of periosteal reaction seen with aggressive bone lesions. The periosteum does not have time to ossify with shells of new bone (e.g. as seen in a single layer and multilayered periosteal reaction) in aggressive lesions, so only the edge of the raised periosteum will os...
Chronic unilateral airspace opacification is a subset of the differential diagnoses for airspace opacification. An exhaustive list of all possible causes of chronic unilateral airspace opacities is long, but a useful framework is as follows:
Chronic bilateral airspace opacification is a subset of the differential diagnosis for airspace opacification. An exhaustive list of all possible causes of chronic bilateral airspace opacities is long, but a useful framework is as follows:
granulomatosis with polyangi...
Chondrocalcinosis (plural: chondrocalcinoses) is a descriptive term indicating the presence of gross calcium deposition within articular cartilage, i.e. both hyaline and fibrocartilage.
Chondrocalcinosis articularis was an early term for calcium pyrophosphate dihydrate deposition d...
Cerebrovascular malformations are vascular malformations related to the vessels that supply the brain and other cranial structures.
Over the years, cerebrovascular malformations have been classified in a variety of ways by different authors.
Over the years cerebral vascular mal...
Brain herniation, also referred to as acquired intracranial herniation, refers to shift of brain tissue from its normal location, into an adjacent space as a result of mass effect. It is a life-threatening condition that requires prompt diagnosis.
There are a number of different pat...
Cerebellopontine angle (CPA) masses are relatively common. Although a diverse range of pathologies may be seen in this region, the most common by far is vestibular schwannoma.
Cerebellopontine angle masses can be divided into four groups, based on imaging characteristics:
Distribution of bronchiectasis can help in narrowing the differential diagnosis. Central bronchiectasis is typically seen in:
allergic bronchopulmonary aspergillosis (ABPA)
congenital tracheobronchomegaly (also known as Mounier Kuhn syndrome)
Williams Campbell syndrome (rare)...
Calcification of the globe has many causes, varying from the benign to malignant. When calcification is seen of the posterior half of the globe, it could relate to any of the layers (scleral, choroidal or retinal), as it is not possible to separate them out on CT.
drusen: 1% population...
Bat wing opacities, also known as butterfly opacities, refer to a pattern of bilateral perihilar lung shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3,4.
Bat wing pulmonary opacities can be caused by:
The causes of basal ganglia T2 hyperintensity can be remembered using the mnemonic LINT:
venous infarction (internal cerebral vein thrombosis)
autoimmune encephalitis (e.g. anti-D2 dopamine antibody encephalitis)
Basal ganglia T2 hypointensities can be caused by any of the following and is commonly remembered using the mnemonic ChOMP.
Parkinson disease: more in globus pallidus
Parkinson-plus syndrome: more in putamen
deoxyhemoglobin of hemorrhage
Basal ganglia calcification is common and is seen in approximately 1% of all CT scans of the brain, depending on the demographics of the scanned population. It is seen more frequently in older patients and is considered a normal incidental and idiopathic finding in an elderly patient but should ...
There are many causes of basal ganglia T1 hyperintensity, but the majority relate to deposition of T1-intense elements within the basal ganglia such as:
calcium and phosphate abnormalities
acquired non-Wilsonian hepatocerebral degeneration
An anterosuperior mediastinal mass can be caused by neoplastic and non-neoplastic pathology. As their name suggests, they are confined to the anterior mediastinum, that portion of the mediastinum anterior to the pericardium and below the level of the clavicles.
The differential diagnosis for a...
The differential for air space opacities is extensive, and needs to be interpreted in context of chronicity (previous imaging) and clinical context. It is therefore useful to divide airspace opacities as follows:
acute airspace opacities with lymph node enlargement
acute airspace opacities: un...
Acute unilateral airspace opacification is a subset of the differential diagnosis for airspace opacification.
The exhaustive list of all possible causes would be huge, but a useful framework includes:
pus, i.e. pulmonary infection
Acute airspace opacification with lymphadenopathy is a subset of the differential diagnosis for generalized airspace opacification and includes:
post-obstructive causes (usually chronic, but 'new' changes can occur)
primary lung cancer
Acute bilateral airspace opacification is a subset of the larger differential diagnosis for airspace opacification. An exhaustive list of all possible causes of acute bilateral airspace opacities is long, but a useful way to consider the huge list is via the material within the airways:
Venous thromboembolism covers a wide spectrum of diseases. Individual conditions and complicating condition include:
head and neck
cerebral vein thrombosis
dural venous sinus thrombosis
cavernous sinus thrombosis
deep cerebral vein thrombosis
cortical vein thrombosis
superior ophthalmic v...