Hydrocoele of the canal of Nuck is a rare condition in female children caused by a failure of complete obliteration of the canal of Nuck 1. The canal of Nuck is an abnormal patent pouch of peritoneum extending anterior to the round ligament of the uterus into the labia majora 2. Incomplete oblit...
Hydrops fetalis is excessive extravasation of fluid into the third space in a fetus which could be due to heart failure, volume overload, decreased oncotic pressure, or increased vascular permeability. Hydrops fetalis is defined as accumulation of fluid +/- oedema involving at least two fetal co...
Hydroxyapatite crystal deposition disease (HADD) is a disease of uncertain aetiology characterised by periarticular and intra-articular deposition of hydroxyapatite (HA) crystals.
The shoulder is the most frequently involved site with classic calcific tendinitis presentation.
Hyperimmunoglobulin E (hyper IgE) syndrome (HIES), also known as Job syndrome, consists of heterogeneous group of complex hereditary combined B- and T-cell immune deficiency diseases characterised by recurrent Staph aureus chest infections, characteristic coarse facial appearance and dental prob...
Hypersensitivity reactions are the immunological response to both exogenous and endogenous antigens, and forms the basis for many diseases.
There are four types of hypersensitivity reactions, each mediated by a different mechanism 1-4:
type 1 hypersensitivity: immed...
Hypersplenism is a cytopaenia resulting from blood pooling in the spleen, and is almost always associated with splenomegaly.
There is an almost overwhelming list, some more common causes are given below 1,3,4:
congestive splenomegaly: cirrhosis, Budd-Chiari syndrome, por...
Hypertensive intracerebral haemorrhages are common. In fact hypertension is the most common cause of intracerebral haemorrhages. They can be conveniently divided according to their typical locations which include, in order of frequency:
basal ganglia haemorrhage (especially the putamen)
Hypertensive microangiopathy, also referred to as chronic hypertensive encephalopathy (not to be confused with acute hypertensive encephalopathy, better known as PRES) results for the sustained effects of elevated systemic blood pressure on the brain.
The key findin...
Hypertrophic olivary degeneration (HOD) is a rare condition characterised by unique pattern of trans-synaptic degeneration. It is caused by a lesion in the triangle of Guillain and Mollaret, resulting in hypertrophy of the inferior olivary nucleus. The three corners of the triangle are:
Hypertrophic pachymeningitis is a condition where there is localised inflammatory thickening of the dura. It can result from a number of causes which include:
CNS tuberculosis: tuberculous pachymeningitis
Hypoglycaemic encephalopathy is a brain injury that results from prolonged or severe hypoglycaemia.
On imaging, it can manifest on MRI as bilateral areas of increased signal on both T2 and FLAIR affecting the posterior limb of the internal capsule, cerebral cortex (in particular parieto-occipi...
Hypoparathyroidism results from reduced secretion of parathyroid hormone by the parathyroid glands. It results in hypocalcaemia.
tetany: peripheral paresthesia, carpopedal spasm, seizures
emotional lability, depression and anxiety, psychosis
Squamous cell carcinoma of the hypopharynx is relatively uncommon, carries the worst prognosis of any head and neck squamous cell carcinoma (HNSCC), and is a challenge to diagnose and treat.
Hypopharyngeal carcinoma is relatively uncommon representing only 10% of all proximal aerodigestive tra...
Hypospadias refers to type of congential malformation affecting the male external genitalia.
The estimated prevalence is ~2 (range 0.2-4.1) per 1000 live births.
The urethral meatus is abnormally positioned proximally and ventrally to its normal position.
It is though...
Hypovitaminosis A results from inadequate intake of vitamin A, fat malabsorption, or liver disorders and produces a variety of epithelial alterations.
The World Health Organization currently estimates that 45-122 countries have a vitamin A deficiency of public health significanc...
Scurvy (also known as Barlow disease in infants) is a condition characterised by an increased bleeding tendency and impaired collagen synthesis resulting in osteoporosis and impaired wound healing. It is caused by a dietary lack of vitamin C (ascorbic acid).
Scurvy in adults is ra...
Hyrtl's fissure (also known as tympanomeningeal fissure) is a congenital infra-labyrinthic fissure. It is a very rare cause of spontaneous CSF ottorhoea.
this can be diagnosed on axial slices and coronal reformations
CT cisternography and radionuclide cisternography ...
Idiopathic dilatation of the pulmonary trunk is a rare congenital anomaly comprising of pulmonary trunk enlargement with or without dilatation of the right and left pulmonary arteries.
For this diagnosis, exclusion of pulmonary and cardiac diseases (mainly pulmonary valve stenosis) and confirma...
Idiopathic dilated cardiomyopathy is a subtype of dilated cardiomyopathy. It is a type of non-ischaemic cardiomyopathy where no underlying cause can be found.
This form of cardiomyopathy may account for up to 50% of all dilated cardiomyopathies 4. Patients usually ranging around 2...
Idiopathic giant bullous emphysema, also known as vanishing lung syndrome (VLS), is characterised by giant emphysematous bullae, which commonly develop in the upper lobes and occupy at least one-third of a hemithorax. It is a progressive condition that is also associated with several forms of em...
Idiopathic intracranial hypertension (IIH), also historically known as pseudotumour cerebri, is a syndrome with signs and symptoms of increased intracranial pressure but where a causative mass or hydrocephalus is not identified.
The older term benign intracranial hypertension is ge...
Idiopathic portal hypertension (noncirrhotic portal hypertension or Banti syndrome) is a term that has been given to portal hypertension occurring without hepatic cirrhosis, parasitic infection, or portal venous thrombosis.
Rare condition. More common in India and Japan.
Idiopathic pulmonary fibrosis (IPF) is a clinical syndrome and considered the most common and the most lethal form of pulmonary fibrosis corresponding to the histologic and imaging pattern of UIP. It is more common in middle age or elderly men and diagnosed by:
histological or imaging pattern ...
Idiopathic pulmonary haemosiderosis (IPH) is an uncommon form of pulmonary haemosiderosis. It is characterised by the triad of
iron deficiency anemia
diffuse pulmonary infiltrates, usually represented by diffuse pulmonary haemorrhage
The diagnosis is usually made by exclusion 1.
Idiopathic retroperitoneal fibrosis (IRF) is a subtype of retroperitoneal fibrosis where no obvious cause is found. It includes a spectrum of diseases which are characterized by fibroinflammatory tissue encasing the abdominal aorta and the iliac arteries. This process may extend into the retrope...
Idiopathic scrotal calcinosis (ISC), sometimes called dystrophic scrotal calcinosis, is a rare benign condition characterized by superficial calcifications within the skin of the scrotum of unclear etiology, typically affecting men aged 20-40. The condition is primarily cosmetic, but may recur ...
IgG4-related lung disease is a recently described condition. It may occur with or without systemic involvement. It is considered part of the spectrum of IgG-4 related disease.
On HRCT of the chest, it may be categorised into four major subtypes 5:
solid nodular type
Iliofemoral deep vein thrombosis occurs when a thrombus in the iliac vein (common, external or internal) or common femoral vein obstructs the venous outflow from the lower limb leading to marked oedema.
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Immature ovarian teratomas are uncommon ovarian germ cell tumours. They differ from mature ovarian teratomas (dermoid cysts) both histologically by the presence of immature tissue, and clinically by their more malignant behaviour.
They are considerably less common than mature ovar...
The human body regularly encounters harmful microorganisms, and because of this it has developed a system of defences to help identify and eliminate infective pathogens in the body, known as the Immune system.
Humans have two types of immunity: innate immunity and acquired immunity.
Immunohistochemistry is a method of assessing histology with the use of antibodies to specific antigens. It is complementary to the older technique of chemical staining of tissues but is often combined with a counter-stain for context (e.g. haematoxylin to stain cell nuclei blue).
The process ...
Imperforate hymen is a congenital condition in which the hymen is without a normal central opening.
It happens in 0.1% of the female population, usually an isolated finding.
Primary amenorrhea with cyclic lower abdominal pain during menarche age. An imperforat...
An incarcerated uterus or trapped uterus describes an extremely rare situation where a retroverted or retroflexed gravid uterus fails to ascend into the abdominal cavity.
This is an uncommon presentation and is said to occur in 1 in 3000 pregnancies. Uncomplicated retroversion may...
Incisional hernias are relatively common and along with parastomal hernias, umbilical hernias, paraumbilical hernias and spigelian hernias, they are usually anterior abdominal hernias.
Usually develop within a few months of surgery but a small proportion can remain clinically sile...
Incomplete double aortic arch is a rare vascular ring anomaly wherein a segment of the minor aortic arch, usually the left, is atretic.
As in the case of other vascular rings, this anomaly can cause 1:
Some patients may reach adulthood with...
Incomplete miscarriage is a term given to miscarriage where there are retained products of conception still within the uterus.
Ultrasound appearance is variable, ranging from visible fetal parts to a mass of mixed echogenicity. The presence of a prominent vasc...
Infantile haemangiomas are benign vascular neoplasms that correspond to the most common tumours of infancy. They virtually can occur anywhere, but the majority has a head and neck distribution. Characteristic growth and subsequent involution observed during the early childhood is the usual natur...
Infantile hepatic haemangiomas (IHH) are a liver lesion composed of large endothelial-lined vascular channels seen in fetuses and neonates. It should not be confused with a hepatic epithelioid haemangioendothelioma, which occurs in older patients.
Those benign tumours were previous...
Infectious bronchiolitis refers to subtype of bronchiolitis where there is an definite infective precipitant. It falls under the sub group in inflammatory bronchiolitides and by some authors is considered a type of cellular bronchiolitis 3. It tends to be more clinically severe in children than ...
Infectious colitis refers to inflammation of the colon due to an infective cause, including bacterial, viral, fungal, or parasitic infections.
In Western countries, bacterial infection is the most common cause, while in developing countries parasitic infection is much more common....
Infectious myositis is an infection of skeletal muscle, and can be acute, subacute, or chronic. Pyomyositis refers specifically to a bacterial infection of skeletal muscle.
It is most often seen in young adults. Pyomyositis, or bacterial myositis, was once considered a tropical d...
Infective endocarditis is defined as infection of the endocardium. It commonly affects the valve leaflets and chordae tendineae, as well as prosthetic valves and implanted devices.
Infective endocarditis has an estimated general prevalence of 3 to 9 cases per 100,000. Intravenous ...
Inferior mesenteric artery aneurysms are among the rarest of all visceral artery aneurysms.
Aneurysms of the inferior mesenteric artery (IMA) only account for <1% of all visceral artery aneurysms 1,2. These aneurysms are more common in men than in women 3.
Inferior vena caval (IVC) thrombosis is an essential diagnosis while evaluating any neoplastic lesion, or portal hypertension. It is also important to differentiate bland thrombus from tumour thrombus.
Patient can present with many features which include
bilateral pedal oede...
Inferior vena cava (IVC) webs are an uncommon condition characterised by obstruction of the hepatic segment of the inferior vena cava by a membrane or fibrous band. This is often associated with occlusion of one or more of the hepatic veins.
If there is hepatic vein invol...
Infiltrating syringomatous adenoma of the nipple is a relatively rare, benign dermal neoplasm in the areola and nipple.
Syringomatous adenomas of the nipple usually present as unilateral 1 to 3 cm firm lesion in the subareolar or nipple region of the breast. Tenderness, i...
Inflammation is a response to a noxious stimuli which can be either be acute or chronic.
The cardinal signs of inflammation include:
loss of tissue function
Acute inflammation occurs within the first few hours after an injury.
Inflammatory abdominal aortic aneurysm (IAAA) is a variant of abdominal aortic aneurysm (AAA) characterised by inflammatory thickening of the aneurysm wall, perianeurysmal fibrosis and adherence to surrounding structures.
They account for ~5 to 10% of all AAAs.
Inflammatory carcinomas of the breast also referred as inflammatory breast cancers, are a relatively uncommon but aggressive form of invasive breast carcinoma which has a characteristic clinical presentation and unique radiographic appearances.
Inflammatory carcinomas account f...
Inflammatory hepatic adenomas are a genetic and pathological subtype of hepatic adenoma. Their appearance and prognosis is different than other subtypes and has highest incidence of haemorrhage amongst hepatic adenoma subtypes.
Most common subtype of hepatic adenoma (40-50%). Occu...
Inflammatory myofibroblastic tumours (IMT), also known as plasma cell granulomas, are rare neoplasms that have a diverse spectrum of biological behaviour.
It can occur at any age and there is currently no recognised gender predilection.
Composed of spindle cells (key ...
Inflammatory myofibroblastic tumours of the lungs are a location specific type of inflammatory myofibroblastic tumours.
They are very rare with their incidence reported at approximately 0.04-1% of all the pulmonary neoplasms 1. While it can affect any age group, around 25% of case...
Inguinal herniation is a type of abdominal wall hernia 1.
They are the commonest type abdominal wall herniation (up to 80% 3) and are most often acquired. There is recognised male predilection with a M:F ratio of up to 7:1 3.
It is broadly divided into two types:
Insulinomas are the most common sporadic endocrine tumour of the pancreas.
Account for 40% of syndromic pancreatic endocrine tumours. Overall incidence of ~0.0003%.
Typically insulinomas present with Whipple's triad consisting of:
fasting hypoglycemia (<50...
The inter-arterial course of the left coronary artery, also known as the malignant course of the left coronary artery, is defined as the origin of the left main or left anterior descending coronary artery from the right coronary sinus of Valsalva with a course between the ascending aorta and the...
Interatrial septal aneurysm or atrial septal aneurysm (ASA) is defined as an abnormal protrusion of the interatrial septum. The exact length of the protrusion that defines an interatrial septal aneurysm varies in the literature, ranging from >11 mm to >15 mm beyond normal excursion in adults 4-5...
Intercostal lung hernia is defined as protrusion of the lung beyond the confines of the thoracic cage. It is an uncommon entity.
Hernias which are symptomatic may cause dyspnoea, chest wall pain or a visible or palpable chest bulge (most common in intercostal lung hernias...
Intercostal nerve neurilemmomas, also known as intercostal nerve schwannoma or neurinoma, are nerve sheaths encapsulated tumours affecting intercostal nerves.
Please refer to the article on schwannomas for a broad discussion about these tumours.
They account for less than 10% ...
Intermediary injuries affect the basal ganglia and/or thalami and are associated with diffuse axonal injury and poor prognosis.
They are a shearing injury of the lenticulostriate arteries and result in haemorrhagic contusions, which are often bilateral.
Interrupted aortic arch (IAA) is an uncommon congenital cardiovascular anomaly where there is a separation between the ascending and descending aorta. It can either be complete or connected by a remnant fibrous band. An accompanying large ventricular septal defect (VSD) and/or patent ductus arte...
Interstitial ectopic pregnancy (also known as an intramural) is an important type of ectopic pregnancy with higher risks of rupture and haemorrhage compared to usual tubal ectopic pregnancies.
The term interstitial pregnancy is sometimes interchangeably used with cornual pregnancy...
Interstitial oedematous pancreatitis is one of the two subtypes of acute pancreatitis. It is normally referred to as "acute pancreatitis" or "uncomplicated pancreatitis" in day-to-day use. Please refer to the article on acute pancreatitis for further details.
Interstitial thickening is pathological thickening of the pulmonary interstitium and can be divided into:
interlobular septal thickening
intralobular septal thickening
secondary pulmonary lobules
Intervertebral osteochondrosis represents the pathologic degenerative process involving the intervertebral disc and the respective vertebral body endplates (not necessarily symptomatic). It is believed to be different and a further stage of spondylosis deformans, which is a consequence of normal...
Intestinal angioedema is oedema into the submucosal space of the bowel wall following protein extravasation from "leaky" vessels. It can affect both the small and large bowel.
Patients often present with nonspecific findings of abdominal pain, nausea, and vomiting.
Intestinal malrotation is a congenital anatomical anomaly that results from an abnormal rotation of the gut as it returns to the abdominal cavity during embryogenesis.
Although some individuals live their entire life with malrotated bowel without symptoms, the abnormality does predispose to mid...
Intracranial dermoid cysts are uncommon lesions with characteristic imaging appearances. They can be thought of as along the spectrum: from epidermoid cysts at one end (containing only desquamated squamous epithelium) and teratomas at the other (containing essentially any kind of tissue from all...
Neurenteric cysts are developmental CNS lesions arising from endoderm.
They result from incomplete resorption of the neurenteric canal, a temporary connection between yolk sac and amnion during early embryogenesis. Intracranial neuroentric cysts are extra axial and in 80% of cases a...
Intracranial tuberculous abscesses are an uncommon manifestation of CNS tuberculosis, far less frequently encountered than tuberculous meningitis or tuberculomas.
The epidemiology of patients with tuberculous abscesses is essentially the same as that of other CNS manifestations of...
Intracranial tuberculous granulomas (also known as CNS tuberculomas) are common in endemic areas, and may occur either in isolation or along with with tuberculous meningitis.
The epidemiology of patients with tuberculomas is the same as that of other CNS manifestations of tubercul...
Intracystic carcinoma of the breast refers to a breast cancer located within a cyst.
They represent ~0.2-1.3% of all breast cancers.
Often they tend to represent papillary breast cancer 2:
intracystic papillary breast carcinoma (ICPC)
cystic degeneration of ductal c...
An intracystic papillary carcinoma of the breast is a type of papillary carcinoma of the breast. It accounts for a significant proportion of intracystic breast cancers.
As with papillary carcinomas in general, it tends to occur in postmenopausal women.
Intradiploic epidermoid cysts represent epidermoid cysts that occur in the intradiploic space of the skull.
Painless slowly progressive scalp swelling.
epidermoid cysts may be congenital (most common, arising from ectodermal inclusion during neural tube closur...
Intraductal papillary mucinous neoplasms or tumours (IPMNs or IMPTs) are cystic tumours of the pancreas.
These tumours are most frequently identified in older patients (50-60 years of age) 6. Main duct type (see below) appears to present a decade or so earlier on average than bran...
Intraductal papillomas, or more specifically solitary intraductal papillomas of the breast, are benign breast lesions. Papillomas are the most common intraductal mass lesions of the breast.
Typically present in women in their late reproductive or postmenopausal years (with an aver...
Intradural disc herniations (IDH) occur when disc material related to an intervertebral disc hernia penetrate the spinal dura and lies in an intradural extramedullary location.
IDH correspond to a rare presentation of a common pathology, comprising ~0.28% of all disc herniations 2...
Intradural extramedullary metastases are rare and only account for approximately 5% of spinal metastases.
Please refer on leptomeningeal metastases (brain) to a general discussion focused on the brain's subarachnoid space involvement.
The age at presentation depends on tumour typ...
Intramedullary spinal metastases are rare, occurring in ~1% of autopsied cancer patients, and are less common than leptomeningeal metastases.
Intramedullary lesions may result from:
growth along the Virchow-Robin spaces
direct extension from leptomeninges
Intramuscular myxomas are a rare benign type of soft tissue myxoma most commonly seen in women in the middle adulthood. On imaging, they are often seen in large muscles from thigh, buttocks, or shoulder girdle, and present as well-defined cystic-like lesions with a surrounding rim of fat.
Intraosseous meningioma, also referred as primary intraosseous meningioma, is a rare subtype of meningioma that accounts for less than 1% of all osseous tumours. They fall under the subgroup of primary extradural meningiomas.
It is important to note that it has been argued by some ...
Intraosseous pneumatocysts are gas containing cystic structures seen inside the bone.
They are of uncertain aetiology. These cysts do not communicate with the joint.
Most common site of involvement is sacroiliac joints. Other sites involved are cervical spine, scapula and ...
Intraperitoneal focal fat infarction (IFFI) refers to a group of self-limiting abdominal diseases where the primary insult is acute inflammation of intraperitoneal fat. They commonly mimic the more common causes of acute abdomen such as acute diverticulitis and acute appendicitis. The group incl...
Intrapulmonary lipomas are rare fat containing benign lung lesions.
They mostly occur in the adult population, with occurence in the paediatric population is extremely rare.
As with all lipomas they are composed of adipose tissue. The origin of the peripheral intrapulm...
Intrarenal reflux (IRR) involves intrarenal extension of vesicoureteral reflux (VUR) into the tubular system of the kidney.
IRR occurs in 3-10% of cases and can lead to renal injury, which may eventually result in renal scarring. The condition can be diagnosed by micturating cystourethrography ...
Intrasphenoidal encephaloceles represent encephaloceles which extend into the sphenoid sinus yet confined by its floor 1.
Patients present with spontaneous cerebral spinal fluid (CSF) rhinorrhea.
Intrasphenoidal encephaloceles are divided into medial perisell...
Intratesticular varicocele is a rare entity, occurring in ~2% of symptomatic population.
It is defined as dilated intratesticular veins seen in relation to the mediastinum testis and extending peripherally. It is usually seen in the presence of ipsilateral extratesticular varicocele....
Intrauterine growth restriction (IUGR) is commonly defined as an estimated fetal weight (EFW) at one point in time during pregnancy being at or below the 10th percentile for gestational age 2.
Some authors define the term IUGR when fetal biometric parameters fall under the 5th percentile or fal...
Intravascular lymphoma (IVL), also known as intravascular lymphomatosis, corresponds to a rare variant of extranodal diffuse large B cell lymphoma that affects small and medium sized vessels, and has no specific clinical or laboratory findings. CNS and skin manifestations are the most common for...
Intraventricular metastases are a very rare finding. A few intracranial tumours and some extracranial tumours metastasize to the ventricles. The most common site of intraventricular metastasis is the trigone of the lateral ventricles due to high vascularity of the choroid plexuses. The next most...
Intussusception occurs when one segment of bowel is pulled into itself or a neighbouring loop of bowel by peristalsis. It is also known as bowel telescoping into itself.
It is an important cause of an acute abdomen in children and merits timely ultrasound examination and reduction to preclude s...
Invasive ductal carcinoma is a subset of ductal carcinoma. It is an infiltrating, malignant and abnormal proliferation of neoplastic cells in the breast tissues. It is the most frequently seen breast malignancy.
Peak age of presentation is about 50 to 60 years.
Infiltrating or invasive lobular carcinoma (ILC) of the breast is the second most common type of invasive breast cancer after invasive ductal carcinoma (IDC) "not otherwise specified" (NOS).
They represent 5-10% of all breast cancer. The mean age at presentation may be higher than...
Invasive mucinous adenocarcinoma of lung is a subtype of invasive adenocarcinoma of the lung. It was formerly known as mucinous bronchoalveolar carcinoma.
Mucinous carcinomas originate from columnar mucus-containing cells (c.f. non-mucinous tumours which arise from Clara cells or typ...