Biliary atresia seems to affect females slightly more often than males, and Asians and African Americans more often than Caucasians. It is common for only one child in a pair of twins or within the same family to have the condition. There seems to be no link to medications or immunizations given immediately before or during pregnancy. Diabetes during pregnancy particularly during the first trimester seems to predispose to a number of distinct congenital abnormalities in the infant such as sacral agenesis and the syndromic form of biliary atresia.

Frisch & Simonsen (2016) carried out a very large scale study in Denmark, which compared the incidence of meatal stenosis in Muslim males (mostly circumcised) with the incidence of meatal stenosis in ethnic Danish males (mostly non-circumcised). The risk of meatal stenosis in circumcised males was found to be as much 3.7 times higher than in the intact, non-circumcised males.

Involutional stenosis is probably the most common cause of NLD obstruction in older persons. It affects women twice as frequently as men. Although the inciting event in this process is unknown, clinicopathologic study suggests that compression of the lumen of the NLD is caused by inflammatory infiltrates and edema. This may be the result of an unidentified infection or possibly an autoimmune disease.

Sinus disease often occurs in conjunction with, and in other instances may contribute to the development of NLD obstruction. Patients should be asked about previous sinus surgery, as the NLD is sometimes damaged when the maxillary sinus ostium is being enlarged anteriorly.

Pancreas divisum in individuals with no symptoms does not require treatment. Treatment of those with symptoms varies and has not been well established. A surgeon may attempt a sphincterotomy by cutting the minor papilla to enlarge the opening and allow pancreatic enzymes to flow normally. During surgery, a stent may be inserted into the duct to ensure that the duct will not close causing a blockage. This surgery can cause pancreatitis in patients, or in rare cases, kidney failure and death.

An association with adenoma of the minor papilla has been reported.

Numerous studies over a long period of time clearly indicate that male circumcision contributes to the development of urethral stricture. Among circumcised males, reported incidence of meatal stricture varies. Griffiths "et al". (1985) reported an incidence of 2.8 percent. Sörensen & Sörensen (1988) reported 0 percent. Cathcart "et al". (2006) reported an incidence of 0.55 percent. Yegane "et al". (2006) reported an incidence of 0.9 percent. Van Howe (2006) reported an incidence of 7.29 percent. In Van Howe's study, all cases of meatal stenosis were among circumcised boys. Simforoosh "et al". (2010) reported an incidence of 0.55 percent. According to Emedicine (2016), the incidence of meatal stenosis runs from 9 to 20 percent. Frisch & Simonsen (2016) placed the incidence at 5 to 20 percent of circumcised boys.

In one report, about 20% of individuals with mealtime syndrome had strictures upon sialography. For unknown reasons, strictures seem to be more common in females.

Subglottic stenosis is a congenital or acquired narrowing of the subglottic airway. Although it is relatively rare, it is the third most common congenital airway problem (after laryngomalacia and vocal cord paralysis). Subglottic stenosis can present as a life-threatening airway emergency. It is imperative that the otolaryngologist be an expert at dealing with the diagnosis and management of this disorder. Subglottic stenosis can affect both children and adults.

Subglottic stenosis can be of three forms, namely congenital subglottic stenosis, idiopathic subglottic stenosis (ISS) and acquired subglottic stenosis. As the name suggests, congenital subglottic stenosis is a birth defect. Idiopathic subglottic stenosis is a narrowing of the airway due to an unknown cause. Acquired subglottic stenosis generally follows as an after-effect of airway intubation, and in extremely rare cases as a result of gastroesophageal reflux disease (GERD).

Subglottic stenosis is graded according to the Cotton-Meyer classification system from one to four based on the severity of the blockage.

Grade 1 – <50% obstruction

Grade 2 – 51–70% obstruction

Grade 3 – 71–99% obstruction

Grade 4 – no detectable lumen

Treatments to alleviate the symptoms of subglottic stenosis includes a daily dose of steroids such as prednisone, which reduces the inflammation of the area for better breathing. Other medications such as Methotrexate is also being tested by patients but results are pending.

The incidence of urethral diverticulum has been increasing in the 2000s, likely due to increasing diagnosis and detection of the condition. It is estimated to be present in as low as 0.02% of all women and as high as 6% of all women, and 40% of women with lower urinary tract symptoms. Most symptomatic urethral diverticula are present in women from 30–60 years old.

84% of periurethral masses are due to urethral diverticula.

Urethral diverticulum can occur in men, and can cause complications including kidney stones and urinary tract infections.

The resulting syndrome depends on the structure affected.

Examples of vascular stenotic lesions include:

- Intermittent claudication (peripheral artery stenosis)

- Angina (coronary artery stenosis)

- Carotid artery stenosis which predispose to (strokes and transient ischaemic episodes)

- Renal artery stenosis

The types of stenoses in heart valves are:

- Pulmonary valve stenosis, which is the thickening of the pulmonary valve, therefore causing narrowing

- Mitral valve stenosis, which is the thickening of the mitral valve (of the left heart), therefore causing narrowing

- Tricuspid valve stenosis, which is the thickening of the tricuspid valve (of the right heart), therefore causing narrowing

- Aortic valve stenosis, which is the thickening of the aortic valve, therefore causing narrowing

Stenoses/strictures of other bodily structures/organs include:

- Pyloric stenosis (gastric outflow obstruction)

- Lumbar, cervical or thoracic spinal stenosis

- Subglottic stenosis (SGS)

- Tracheal stenosis

- Obstructive jaundice (biliary tract stenosis)

- Bowel obstruction

- Phimosis

- Non-communicating hydrocephalus

- Stenosing tenosynovitis

- Atherosclerosis

- Esophageal stricture

- Achalasia

- Prinzmetal angina

- Vaginal stenosis

A majority of individuals born with pancreas divisum will not have symptoms. In some cases, pancreas divisum is only detected during autopsy. A small group of individuals will develop symptoms which commonly include abdominal pain, nausea, vomiting, and acute and chronic pancreatitis.

The radiocephalic arteriovenous fistula (RC-AVF) is a shortcut between cephalic vein and radial artery at the wrist. It is the recommended first choice for hemodialysis access. Possible underlying causes for failure are stenosis and thrombosis especially in diabetics and those with low blood flow such as due to narrow vessels, arteriosclerosis and advanced age. Reported patency of fistulae after 1 year is about 62.5%.

Dacryocystocele or timo cyst is a benign, bluish-gray mass in the inferomedial canthus that forms as a result of a narrowing or obstruction of the nasolacrimal duct, usually during prenatal development. The prevalence of dacryocystocele is 1 in 3884 live births.

Choledochal cysts are treated by surgical excision of the cyst with the formation of a roux-en-Y anastomosis hepaticojujenostomy/ choledochojujenostomy to the biliary duct.

Future complications include cholangitis and a 2% risk of malignancy, which may develop in any part of the biliary tree. A recent article published in Journal of Surgery suggested that choledochal cysts could also be treated with single-incision laparoscopic hepaticojejunostomy with comparable results and less scarring. In cases of saccular type of cyst, excision and placement of T-shaped tube is done.

Currently, there is no accepted indication for fetal intervention in the management of prenatally suspected choledochal cysts.

The epidemiology of pulmonary valve stenosis can be summed up by the congenital aspect which is the majority of cases, in broad terms PVS is rare in the general population.

The nasolacrimal ducts drain the excess tears from our eyes into the nasal cavity. In dacryocystocele there this tube gets blocked on either end and as a result when mucoid fluid collects in the intermediate patent section it forms a cystic structure.

Strictures tend to be diagnosed based on difficulty with insertion and manipulation during sialendoscopy, or by sialography or ultrasound.

Some cases of biliary atresia may result from exposure to aflatoxin B1, and to a lesser extent aflatoxin B2 during late pregnancy. Intact maternal detoxification protects baby during intrauterine life, yet after delivery the baby struggles with the aflatoxin in its blood and liver. Moreover, the baby feeds aflatoxin M1 from its mom, as aflatoxin M1 is the detoxification product of aflatoxin B1. It is a milder toxin that causes cholangitis in the baby.

There are isolated examples of biliary atresia in animals. For instance, lambs born to sheep grazing on land contaminated with a weed (Red Crumbweed) developed biliary atresia at certain times. The plants were later found to contain a toxin, now called biliatresone Studies are ongoing to determine whether there is a link between human cases of biliary atresia and toxins such as biliatresone. There are some indications that a metabolite of certain human gut bacteria may be similar to biliatresone.

Laryngotracheal stenosis refers to abnormal narrowing of the central air passageways. This can occur at the level of the larynx, trachea, carina or main bronchi.

In a small number of patients narrowing may be present in more than one anatomical location.

A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure. It is also sometimes called a stricture (as in urethral stricture).

Stricture as a term is usually used when narrowing is caused by contraction of smooth muscle (e.g., achalasia, prinzmetal angina); stenosis is usually used when narrowing is caused by lesion that reduces the space of lumen (e.g., atherosclerosis). The term coarctation is another synonym, but is commonly used only in the context of aortic coarctation.

Restenosis is the recurrence of stenosis after a procedure. The term is from Ancient Greek στενός, "narrow".

Mirizzi's syndrome occurs in approximately 0.1% of patients with gallstones. It is found in 0.7 to 2.5 percent of cholecystectomies.

It affects males and females equally, but tends to affect older people more often. There is no evidence of race having any bearing on the epidemiology.

Choledochal cysts (a.k.a. bile duct cyst) are congenital conditions involving cystic dilatation of bile ducts. They are uncommon in western countries but not as rare in East Asian nations like Japan and China.

A persistent thyroglossal duct is a usually benign medical condition in which the thyroglossal duct, a structure usually only found during embryonic development, fails to atrophy. The duct persists as a midline structure forming an open connection between the back of the tongue and the thyroid gland.This opening can lead to fluid accumulation and infection, which necessitate the removal of the duct.

Nasolacrimal duct cysts are a cutaneous condition that is a developmental defect present at birth.