A Cimino fistula, also Cimino-Brescia fistula, surgically created arteriovenous fistula and (less precisely) arteriovenous fistula (often abbreviated AV fistula or AVF), is a type of vascular access for hemodialysis. It is typically a surgically created connection between an artery and a vein in the arm, although there have been acquired arteriovenous fistulas which do not in fact demonstrate connection to an artery.

Fistulas can develop in various parts of the body. The following list is sorted by the International Statistical Classification of Diseases and Related Health Problems.

Surgically created AV fistulas work effectively because they:

- Have high volume flow rates (as blood takes the path of least resistance; it prefers the (low resistance) AV fistula over traversing (high resistance) capillary beds).

- Use native blood vessels, which, when compared to synthetic grafts, are less likely to develop stenoses and fail.

Various types of fistulas include:

Although most fistulas are in forms of a tube, some can also have multiple branches.

CCF symptoms include bruit (a humming sound within the skull due to high blood flow through the arteriovenous fistula), progressive visual loss, and pulsatile proptosis or progressive bulging of the eye due to dilatation of the veins draining the eye. Pain is the symptom that patients often find the most difficult to tolerate.

Patients usually present with sudden or insidious onset of redness in one eye, associated with progressive proptosis or bulging.

They may have a history of similar episodes in the past.

The most common signs/symptoms of DAVFs are:

1. Pulsatile tinnitus

2. Occipital bruit

3. Headache

4. Visual impairment

5. Papilledema

Pulsatile tinnitus is the most common symptom in patients, and it is associated with transverse-sigmoid sinus DAVFs. Carotid-cavernous DAVFs, on the other hand, are more closely associated with pulsatile exophthalmos. DAVFs may also be asymptomatic (e.g. cavernous sinus DAVFs).

Carotid cavernous fistulae may form following closed or penetrating head trauma, surgical damage, rupture of an intracavernous aneurysm, or in association with connective tissue disorders, vascular diseases and dural fistulas.

Just like berry aneurysm, an intracerebral arteriovenous fistula can rupture causing subarachnoid hemorrhage.

Anal fistulae can present with the following symptoms:

- skin maceration

- pus, serous fluid and/or (rarely) feces discharge — can be bloody or purulent

- pruritus ani — itching

- depending on presence and severity of infection:

Symptoms include hemoptysis, and/or massive hemorrhage which result from the formation of a fistula between the trachea and the brachiocephalic artery. The primary threat is respiratory compromise leading to dyspnea and cyanosis. Patients can later present with hypovolemic shock which include symptoms of tachycardia, cyanosis, cold and clammy skin, dizziness, confusion, and fatigue. Patients may also develop septicemia.

Low-output fistula: < 500 mL/day

High-output fistula: > 500 mL/day

Depending on their relationship with the internal and external sphincter muscles, fistulae are classified into five types:

- Extrasphincteric fistulae begin at the rectum or sigmoid colon and proceed downward, through the levator ani muscle and open into the skin surrounding the anus. Note that this type does not arise from the dentate line (where the anal glands are located). Causes of this type could be from a rectal, pelvic or supralevator origin, usually secondary to Crohn's disease or an inflammatory process such as appendiceal or diverticular abscesses.

- Suprasphincteric fistulae begin between the internal and external sphincter muscles, extend above and cross the puborectalis muscle, proceed downward between the puborectalis and levator ani muscles, and open an inch or more away from the anus.

- Transphincteric fistulae begin between the internal and external sphincter muscles or behind the anus, cross the external sphincter muscle and open an inch or more away from the anus. These may take a 'U' shape and form multiple external openings. This is sometimes termed a 'horseshoe fistula.'

- Intersphincteric fistulae begin between the internal and external sphincter muscles, pass through the internal sphincter muscle, and open very close to the anus.

- Submucosal fistulae pass superficially beneath the submucosa and do not cross either sphincter muscle.

A dural arteriovenous fistula (DAVF), is an abnormal direct connection (fistula) between a meningeal artery and a meningeal vein or dural venous sinus. In cases where there are multiple fistulas, the related term dural arteriovenous malformation (DAVF) is used.

Diagnosis is typically via a CT angiography, esophagogastroduodenoscopy, or arteriography. It is part of the differential diagnosis of gastrointestinal bleeding.

Thyroglossal duct cysts most often present with a palpable asymptomatic midline neck mass above the level of the hyoid bone. The mass on the neck moves during swallowing or on protrusion of the tongue because of its attachment to the tongue via the tract of thyroid descent. Some patients will have neck or throat pain, or dysphagia.

The persistent duct or sinus can promote oral secretions, which may cause cysts to become infected. Up to half of thyroglossal cysts are not diagnosed until adult life. The tract can lie dormant for years or even decades, until some kind of stimulus leads to cystic dilation. Infection can sometimes cause the transient appearance of a mass or enlargement of the cyst, at times with periodic recurrences. Spontaneous drainage may also occur. Differential diagnosis are ectopic thyroid, enlarged lymph nodes, dermoid cysts and goiter.

Thyroglossal cyst usually presents as a midline neck lump (in the region of the hyoid bone) that is usually painless, smooth and cystic, though if infected, pain can occur. There may be difficulty breathing, dysphagia (difficulty swallowing), or dyspepsia (discomfort in the upper abdomen), especially if the cyst becomes large.

The most common location for a thyroglossal cyst is midline or slightly off midline, between the isthmus of the thyroid and the hyoid bone or just above the hyoid bone. A thyroglossal cyst can develop anywhere along a thyroglossal duct, though cysts within the tongue or in the floor of the mouth are rare.A thyroglossal cyst will move upwards with protrusion of the tongue.Thyroglossal cysts are associated with an increased incidence of ectopic thyroid tissue. Occasionally, a lingual thyroid can be seen as a flattened strawberry-like lump at the base of the tongue.

Two-thirds of TIF occurs within three weeks of a tracheotomy. A TIF should be on the top of the differential diagnosis in patients with a tracheostomy followed by bleeding. Most effective diagnostic tool is a rigid bronchoscopy, although this may be unnecessary as a massive arterial hemorrhage from the tracheostomy likely indicates the formation of an TIF. However, a rigid brochoscopy can clear the tracheobronchial tree of aspirated blood and may be used to terminate blood flow.

Only 35% of TIF patients exhibit the pathognomonic warning signs which include sentinel bleeding, a small bleed from the tracheostomy in the preceding the TIF, and pulsations of the tracheostomy tube that coincides with the heartbeat.

An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm.

An aortoenteric fistula is a connection between the aorta and the intestines, stomach, or esophageus. There can be significant blood loss into the intestines resulting in bloody stool and death. It is usually secondary to an abdominal aortic aneurysm repair.

An infected thyroglossal duct cyst can occur when it is left untreated for a certain amount of time or simply when a thyroglossal duct cyst hasn't been suspected. The degree of infection can be examined as major rim enhancement has occurred, located inferior to the hyoid bone. Soft tissue swelling occurs, along with airway obstruction and trouble swallowing, due to the rapid enlargement of the cyst.

With infections, there can be rare cases where an expression of fluid is projected into the pharynx causing other problems within the neck.

An enterocutaneous fistula (ECF) is an abnormal communication between the small or large bowel and the skin that allows the contents of the stomach or intestines to leak through an opening in the skin.

A biliary fistula is a type of fistula in which bile flows along an abnormal connection from the bile ducts into nearby hollow structure. Types of biliary fistula include:

- bilioenteric fistula: abnormal connection to small bowel, usually duodenum.

- thoracobiliary fistula: abnormal connection to pleural space or bronchus (rare).

These may be contrasted to a bile leak, in which bile escapes the bile ducts through a perforation or faulty surgical anastomosis into the abdominal cavity. Damage to a bile duct may result in a leak, which may eventually become a biliary fistula.

Mirizzi's syndrome has no consistent or unique clinical features that distinguish it from other more common forms of obstructive jaundice. Symptoms of recurrent cholangitis, jaundice, right upper quadrant pain, and elevated bilirubin and alkaline phosphatase may or may not be present. Acute presentations of the syndrome include symptoms consistent with cholecystitis.

Surgery is extremely difficult as Calot's triangle is often completely obliterated and the risks of causing injury to the CBD are high.

An atrioventricular fistula is a fistula between an atrium and a ventricle of the heart.

Clinically, thrills can be felt on the arm of the patient if palpated at the fistula.

If fecal matter passes through the fistula into the bladder, the existence of the fistula may be revealed by pneumaturia or fecaluria.

Mirizzi's syndrome is a rare complication in which a gallstone becomes impacted in the cystic duct or neck of the gallbladder causing compression of the common bile duct (CBD) or common hepatic duct, resulting in obstruction and jaundice. The obstructive jaundice can be caused by direct extrinsic compression by the stone or from fibrosis caused by chronic cholecystitis (inflammation). A cholecystocholedochal fistula can occur.