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%.

This is based on MRI scan, magnetic resonance angiography and CT scan. A cerebral digital subtraction angiography (DSA) enhances visualization of the fistula.

- CT scans classically show an enlarged superior ophthalmic vein, cavernous sinus enlargement ipsilateral (same side) as the abnormality and possibly diffuse enlargement of all the extraocular muscles resulting from venous engorgement.

- Selective arteriography is used to evaluate arteriovenous fistulas.

- High resolution digital subtraction angiography may help in classifying CCF into dural and direct type and thus formulate a strategy to treat it either by a balloon or coil or both with or without preservation of parent ipsilateral carotid artery.

Treatment for fistula varies depending on the cause and extent of the fistula, but often involves surgical intervention combined with antibiotic therapy.

Typically the first step in treating a fistula is an examination by a doctor to determine the extent and "path" that the fistula takes through the tissue.

In some cases the fistula is temporarily covered, for example a fistula caused by cleft palate is often treated with a palatal obturator to delay the need for surgery to a more appropriate age.

Surgery is often required to assure adequate drainage of the fistula (so that pus may escape without forming an abscess). Various surgical procedures are commonly used, most commonly fistulotomy, placement of a seton (a cord that is passed through the path of the fistula to keep it open for draining), or an endorectal flap procedure (where healthy tissue is pulled over the internal side of the fistula to keep feces or other material from reinfecting the channel). Treatment involves filling the fistula with fibrin glue; also plugging it with plugs made of porcine small intestine submucosa have also been explored in recent years, with variable success. Surgery for anorectal fistulae is not without side effects, including recurrence, reinfection, and incontinence. High rate of recurrence and more chances of complications like incontinence are always there in fistula surgeries (Anal Fistula).

It is important to note that surgical treatment of a fistula without diagnosis or management of the underlying condition, if any, is not recommended. For example, surgical treatment of fistulae in Crohn's disease can be effective, but if the Crohn's disease itself is not treated, the rate of recurrence of fistula is very high (well above 50%).

The procedure was invented by doctors James Cimino and M. J. Brescia in 1966. Before the Cimino fistula was invented, access was through a Scribner shunt, which consisted of a Teflon tube with a needle at each end. Between treatments, the needles were left in place and the tube allowed blood flow to reduce clotting. But Scribner shunts lasted only a few days to weeks. Frustrated by this limitation, James E. Cimino recalled his days as a phlebotomist (blood drawer) at New York City's Bellevue Hospital in the 1950s when Korean War veterans showed up with fistulas caused by trauma. Cimino recognized that these fistulas did not cause the patients harm and were easy places to get repeated blood samples. He convinced surgeon Kenneth Appell to create some in patients with chronic kidney failure and the result was a complete success. Scribner shunts were quickly replaced with Cimino fistulas, and they remain the most effective, longest-lasting method for long-term access to patients' blood for hemodialysis today.

"Diagnosis" is by examination, either in an outpatient setting or under anaesthesia (referred to as — Examination Under Anaesthesia). The fistula may be explored by using a fistula probe (a narrow instrument). In this way, it may be possible to find both openings. The examination can be an anoscopy. Diagnosis may be aided by performing a fistulogram, proctoscopy and/or sigmoidoscopy.

Possible findings:

- The opening of the fistula onto the skin may be observed

- The area may be painful on examination

- There may be redness

- An area of induration may be felt — thickening due to chronic infection

- A discharge may be seen

CLASSIFICATIONS of ANAL FISTULA

- Park's Classification: This was done in 1976 by Parks et al from UK. This was done in the era when MRI or Endoanal Ultrasound was not there. It classified the fistula in four grades

- St James University Hospital Classification: This was done by Morris et al in the year 2000. This classification was improvement over Parks classification as it was based on MRI studies. It classified the fistula in five grades.

- Garg Classification: This was done by Pankaj Garg in 2017. This classification is improvement over both Parks and St James University Hospital Classification. This was based on MRI studies and operative findings in 440 patients. It classified the fistula in five grades. The grades of this classification correlate quite well with the severity of the disease. Grade I & II are simpler fistulas and can be managed by Fistulotomy whereas grade III-V are complex fistulas in which fistulotomy should be not be done. They should be managed by Fistula experts. Unlike Park's and St James University Hospital Classification, this correlation is quite accurate with Garg's classification. Therefore this new classification is useful to both surgeons and radiologists

Cerebral angiography is the diagnostic standard. MRIs are usually normal.

Other conditions in which infected perianal "holes" or openings may appear include Pilonidal cysts/sinuses.

Low-output fistula: < 200 mL/day

Moderate-output fistula: 200-500 mL/day

High-output fistula: > 500 mL/day

Various types of fistulas include:

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

The mainstay of treatment for CCF is endovascular therapy. This may be transarterial (mostly in the case of direct CCF) or transvenous (most commonly in indirect CCF). Occasionally, more direct approaches, such as direct transorbital puncture of the cavernous sinus or cannulation of the draining superior orbital vein are used when conventional approaches are not possible. Spontaneous resolution of indirect fistulae has been reported but is uncommon. Staged manual compression of the ipsilateral carotid has been reported to assist with spontaneous closure in selected cases.

Direct CCF may be treated by occlusion of the affected cavernous sinus (coils, balloon, liquid agents), or by reconstruction of the damaged internal carotid artery (stent, coils or liquid agents).

Indirect CCF may be treated by occlusion of the affected cavernous sinus with coils, liquid agents or a combination of both.

Low-output fistula: < 500 mL/day

High-output fistula: > 500 mL/day

Manual carotid self compression is a controversial treatment for DAVF. Patients using this method are told to compress the carotid with the opposite hand for approximately 10 minutes daily, and gradually increasing the frequency and duration of compression. Currently, it is unclear whether this method is an effective therapy.

Imaging by ultrasonography, MRCP, or CT scan usually make the diagnosis. MRCP can be used to define the lesion anatomically prior to surgery.

Occasionally Mirizzi's syndrome is diagnosed or confirmed on ERCP when requested to alleviate obstructive jaundice or cholangitis by means of an endoscopically placed stent, or when USS has been wrongly reported as choledocolithiasis.

TIF is a rare condition with a .7% frequency, and an mortality rate approaching 100% without surgical intervention. Immediate diagnosis and intervention of an TIF is critical for the surgical intervention success. 25-30% of TIF patients who reach the operating room survive. Recently, the incidence of TIF may have declined due to advances in tracheostomy tube technology and the introduction of the bedside percutaneous dilatational tracheostomy (PDT).

Various modalities of diagnosis are available:

- Cystoscopy

- Colonoscopy

- Poppy seed test

- Transabdominal ultrasonography

- Abdominopelvic CT

- MRI

- Barium enema

- Bourne test

- Cystogram

A definite algorithm of tests is followed for making the diagnosis.

To prevent an TIF, intubation time should be limited to less than 2 weeks and proper techniques should be used when performing tracheotomies. The occurrence of an TIF can be reduced by using more flexible and blunt tracheostomy tubes and insuring that the tubes are properly aligned in the patients. Placing the tracheostomy between the second and third tracheal rings can minimize the risk of an TIF. Repetitive head movements, especially, hyperextension of the neck should be avoided as since this movement results in contact between the innominate artery and the underside of the tube.

Clinical features can be found in the subhyoid portion of the tract and 75% present as midline swellings. The remainder can be found as far lateral as the lateral tip of the hyoid bone.

Typically, the cyst will move upwards on protrusion of the tongue, given its attachment to the embryonic duct, as well as on swallowing, due to attachment of the tract to the foramen caecum.

Diagnosis of a thyroglossal duct cyst requires a medical professional, and is usually done by a physical examination. It is important to identify whether or not the thyroglossal cyst contains any thyroid tissue, as it can define the degree of cyst that is being dealt with.

Diagnostic procedures for a thyroglossal cyst include:

Pleural or ascitic fluid should be sent for analysis. An elevated amylase level, usually > 1,000 IU/L, with protein levels over 3.0 g/dL is diagnostic. Serum amylase is often elevated as well, due to enzyme diffusion across the peritoneal or pleural surface. Contrast-enhanced computed tomography and endoscopic retrograde cholangiopancreatography (ERCP) may also assist in diagnosis, with the latter an essential component of treatment.

Diagnosis is often suspected in patients "in extremis" (close to death) with abdominal trauma or with relevant risk-factors. Diagnosis is confirmed quickly in the Emergency room by ultrasound or CT scan.

Mortality from aortic rupture is up to 90%. 65–75% of patients die before they arrive at hospital and up to 90% die before they reach the operating room.

It is surgically corrected, with resection of any fistula and anastomosis of any discontinuous segments.

Vesicovaginal fistulae are typically repaired either transvaginally or laparoscopically, although patients who have had multiple transvaginal procedures sometimes attempt a final repair through a large abdominal incision, or laparotomy.

The laparoscopic (minimally invasive) approach to VVF repair has become more prevalent due to its greater visualization, higher success rate, and lower rate of complications.

Simple cholecystectomy is suitable for type I patients. For types II–IV, subtotal cholecystectomy can be performed to avoid damage to the main bile ducts. Cholecystectomy and bilioenteric anastomosis may be required. Roux-en-Y hepaticojejunostomy has shown good outcome in some studies.

After diagnosing rectovaginal fistula, it is best to wait for around 3 months to allow the inflammation to subside. For low fistulae, a vaginal approach is best, while an abdominal repair would be necessary for a high fistula at the posterior fornix.

A circular incision is made around the fistula and vagina is separated from the underlying rectum with a sharp circumferential dissection. The entire fistulous tract, along with a small rim of rectal mucosa is incised. The rectal wall is then closed extramucosally.

Most rectovaginal fistuals will need surgery to fix. Medications such as antibiotics and Infliximab might be prescribed to help close the rectovaginal fistula or prepare for surgery.