SINUS AND FISTULA

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SINUS AND FISTULA

Definition: -

Fistula is an abnormal tract connecting between two cavities (as the recto-vaginal fistula) or between a cavity and the outer surface (as fistulous withers) or between a canal and the exterior (as milk and salivary fistulae). When the end of the tract is closed (has one opening), it is called a sinus which is a blind purulent tract showing no tendency to heal.

Classification: -

I-CONGENITAL or ACQUIRED

1-Hereditary (congenital)

The urachus is an example of congenital fistula, in such affection the umbilical cord is closed except the urachus from which the urine comes out from it as well as from the natural external urethral orifice in the penis in males and in the vagina in females, or recto vaginal fistula that sometimes seen in female sheep suffered from atresia ani.

2-Pathologic (acquired)

This fistula results from a pathological condition as a dental fistula, (caused by a diseased tooth) or quittor (caused by necrosis of the lateral cartilage of the hoof).

A-Purulent:  -

It is a fistula discharging pus, like quitter that frequently seen on the coronet corresponding to the lateral cartilage in equine hoof

B-Non-purulent fistula (specific):  -

It is a fistula discharging any secretion rather than pus and these non-purulent fistulae are subdivided into;

i-Excretory fistula: -

As intestinal fistula, anal fistula and urethral fistula

ii-Secretory fistula: -

As milk and salivary fistulae

iii-Specific fistula: -

A fistula caused by a specific infection as actinomycotic fistula and botryomycotic fistula

II-ACCORDING TO NUMBER OF OPENINGS

1-Complete fistula

It has two openings

2-Incomplete or blind fistula

It has one opening (sinus)

Etiology: -

1-Improper drainage of the pus that predisposes to accumulation of pus in the bottom of the abscess preventing its healing. The presence of a foreign body or necrotic tissue at the depth of the fistula

2-Specific affections as actinomycosis and carcinomas

3-Abscesses of the parotid region and parotid duct

4-Faulty incision of an abscess either via incising it from its upper part or insufficient draining

5- Movement of the wall of the sinus prevents healing and predisposes to fistula formation

Signs:-

1-Presence of an opening that varies greatly in diameter and varies in number

2-The orifice of recent fistula is surrounded by granulation tissue while elder ones has hard fibrous borders

3-Long standing fistulae undergo cicatrisation and excessive fibrosis and contraction so that the opening of the fistula presented as if it is in depression

4-Presence of cicatrized spots representing old opening that closed following the formation of new one

5-Probing the duct may or not permits reaching to the cavity of the sinus according to the course of the duct (strait or tortuous), and may indicates presence of more than one sinus communicating by many ducts

6-Injection of fluid into the sinus indicates its volume and whether the orifices communicating or not

Composition of fistula: -

The fistula is composed of an opening, a canal and a depth. Typical opening is a small opening that is usually small in size denuded from hair and discharging pus of bad odor or discharging non-purulent exudates (according to the type of the fistula), and this opening is surrounded by an unhealthy granulation tissue. The skin around the opening epithelializes gradually until the opening is closed by a scar (presence of several scars around the fistula opening is an indication that the fistula is old), sooner or later pus accumulates in the depth forming a new abscess which bursts by a new opening beside the old one and in many cases more than one opening may be present. Some inflammatory reactions may accompany the fistula.

The canal connects the fistulous opening with the depth and it may be straight and short (as in cases of quittor or picked-up nail) or long and tortuous (as in cases of fistulous withers). Insertion of a probe from the opening of the fistula can detect the depth of the fistula and whether there are collateral canals or not.

The depth usually contains the real cause of the fistula which may be a foreign body, as a nail, suture material, piece of gauze, a necrotic tendon or a necrotic piece of bone (sequestrum).

Diagnosis: -

1-History

2-Signs and clinical examination

3-Radiography

Treatment: -

In fistulae with short canals, it is enough to curette the canal and its depth but when it is impossible, an incision is made including the whole tract, then irrigate the wound with antiseptic solution and the foreign body is extracted from the depth if present, while fistulae with long canals are treated by

1-Providing for good drainage when improper drainage is the main cause of formation of fistula. This can be adopted via incising the fistula in down ward direction or via creating counter opening

2-The interior of the fistula can be swapped with caustic substance (silver nitrate or copper sulfate) to facilitate sloughing of its lining that permits faster healing via widening of the lumen of the duct and elimination of necrotic tissue at the depth. However this procedure is not recommended to be used near joint to avoid the possibility of sloughing into the joint

3-Inserting hot iron, in the form of a rod heated till it becomes red, inside the fistula to stimulate separation of necrotic tissues

4-Surgical opening of the fistula through its the whole length till its depth with curetting and removal of necrotic parts and foreign bodies. When the depth of the fistula can't be reached surgically, it is enough to perform curetting and washing with antiseptics

  1. Surgical excision of the fistula (fistulectomy)

6-Some secretory fistulae can be treated either by a purse string suture after freshening the lips or when they have small orifice,  injection of some drugs which have the power to enhance connective tissue formation may be useful. This can be performed by injection of 0.1 cc at 6 places around the orifice, subcutaneously and 2 injections inside the fistula orifice under the mucous membrane.

7-Cases of secretory fistula which do not respond to one of the previous treatments as parotid fistula must be treated by preventing salivary secretion by injecting Tr. iodine or paraffin (heated up to 40°C) inside the parotid duct 3-4 times.

Recto-vaginal or Recto-vestibular Fistula

Congenital recto-vaginal fistula is characterized by the communication between the dorsal wall of the vagina and the ventral portion of the rectum, so that the vulva functions as a common opening to the urogenital and gastrointestinal tracts. Usually, the abnormality is associated with a rectum that ends as a blind pouch immediately cranial to the imperforated anus.

Clinical signs: -

1-Passage of feces through the vulva, with vulvar irritation and tenesmus

2-Cystitis

3-Mega-colon

4-Pneumo-vagina that results from stretched, ruptured, deformed and horizontal vulva which may introduce fecal material, urine and air into the vagina (particularly in older cows) leading to vaginitis, cervicitis, endometritis

5-Failure of conception and repeated breeding

Otherwise the condition occurs as an acquired event in mares (wind. sucking, gill-flirter) because of the precipitate nature of the equine birth process. Perforation of the recto-vaginal shelf occurs at foaling. The lesion does not extend to include the perineum and feces accumulate in the rectum, more over chronic vaginitis ensues.

Diagnosis of such condition radiographically can be performed by retrograde infusion of the rectum with barium sulfate and if the animal suffers from atresia ani, the infusion can be conducted via the vagina.

The condition can be aggravated when the animal couldn't evacuate the rectum leading to mega-colon, however the condition is treated surgically by restoring the lumen of both the rectum and the vagina via linear incision along the median raphe just ventral to the anal sphincter extending to the dorsal vulva then after the fistula is located and isolated by blunt dissection. The dorsal communication with the rectum is ligated with absorbable suture placed around the fistula and the fistula is incised. Then the dorsal ligature subjected to over-sewing to ensure tight seal. The tract is also severed where it joins the vagina and the stoma is sutured with absorbable suture material in a line perpendicular on that created at the rectal side to make cross like.

Treatment: -

Two surgical techniques are frequently used in the treatment of recto-vaginal fistula and atresia ani

1-The fistula is isolated, transected, and the rectum and vulvae defects are closed separately, followed by reconstruction of the anus or

2-The rectum is transected cranial to the fistulous opening, the affected segment is removed, and the terminal part of the rectum is sutured to the anus. Closing the recto-vaginal fistula by numerous purse-string sutures along its length

Fistula of the Parotid Duct

The parotid duct, or duct of Stenson, is the vessel or canal by which saliva is conveyed from the salivary gland into the mouth. On leaving the gland the parotid duct passes along the inner surface of the lower jaw, and then winds round its lower border in front of the great muscle of the cheek in company with the inferior maxillary artery and vein, and finally opens into the mouth opposite to the junction of the second with the third molar tooth of the upper jaw in the horse. In its course round the jaw-bone and along the side of the face it becomes exposed to injury, and as the result of blows from the kicks of horses and other mishaps as well as from the ulcerating effects of calculi (stones) which sometimes form within it, an opening is made through its walls at the seat of injury by which the saliva is allowed to escape instead of passing into the mouth. The duct may be completely divided, as sometimes occurs from external violence, in which case one portion of the vessel is separated from the other, or it may only be punctured. Obviously the former condition is the more serious of the two, since the divided ends draw away from each other and are with difficulty brought together under the most favorable circumstances; and if allowed to remain apart for any length of time that portion connected with the mouth closes up, owing partly to no saliva being able to enter it, but more immediately as the result of inflammation excited in it by the accident. Fistula of the parotid duct may also result from the formation of an abscess in some part of its course giving rise to ulceration of its walls.

Symptoms: -

The existence of this disease is known when a watery fluid is found to discharge through an opening in the skin at or near the lower border of the jaw. The quantity will depend a good deal upon the size of the opening and also upon the act of mastication. When feeding, the secretion of saliva is most active and the flow is very considerable, but becomes comparatively slight when food ceases to be taken.

Treatment: -

The indications here are to close the external wound promptly, so the saliva will flow along its proper channel. Success will greatly depend upon:

1-Whether the vessel is partially or completely divided

2-Upon the period of time which is allowed to elapse between the injury and recourse to treatment

3-The state of the duct itself

When the duct is cut through, or its walls are involved in an ulcerative condition, the prospects of cure are remote; when, however, the duct is simply perforated it is more favorable. Whatever treatment is undertaken, solid food must be altogether withheld for three or four days, or more if necessary, and the patient supported on liquid aliment such as thin oatmeal and maltmeal gruel mixed with eggs, beef-tea, and milk alternately, the object being to keep the jaws at rest and the secretion of the saliva as far as possible in abeyance.

The hair must now be removed from about the wound and the part thoroughly cleansed with soap and water and afterwards freely irrigated with a solution of carbolic acid. With a small needle and catgut-thread the lips of the wound are then to be carefully and completely drawn together, in doing which a sufficient hold should be taken of the skin to guard against tearing out. The part is then to be covered by a thick dressing of styptic-colloid and covered with a thick pad of antiseptic wool or absorbent lint.

When necessary both should be renewed but not otherwise, and the animal is to be so secured that he may not rub or otherwise disturb the application. By some, closure of the wound is attempted to be brought about by the production of a scab, and for this purpose it is freely dressed with caustic, such as nitrate of silver, nitric acid, or the hot iron.

In old-standing cases, where the wound has become callous and that part of the duct near the mouth closed up and impermeable, the salivary gland should be destroyed, and the formation and discharge of saliva from it altogether arrested. This is accomplished by injecting some irritant along the duct into the gland. For this purpose a solution of one of the following drugs is employed, silver nitrate, caustic ammonia, or tincture of iodine. The immediate effect of this course is to cause inflammation and swelling of the gland, sometimes also the production of an abscess; the ultimate result, however, is that the organ is spoiled, ceases to secrete saliva, and wastes away. Defect in mastication will be observed for a short time, and it may cause indigestion, but with care in feeding and management this will soon cease.

Fistulous Withers

This is an abscess above the vertebrae, at the withers, which extends down between the shoulder blades. It is caused by a blow, a bite from another horse, or an ill-fitting collar or saddle.

Symptoms: -

The first symptom is pain over the withers, followed by a swelling which may assume a large dimension. In most cases the swelling bursts, but in a few cases it will subside. If the swelling bursts, the skin may heal after the discharge has ceased, but this will be only temporary, and the abscess is sure to recur. Owing to the position of the abscess, it is extremely difficult to secure drainage, and the ligaments above the vertebrae are apt to be affected by the poison from the pus in the abscess.

Treatment: -

Fistulous withers is a very serious condition, and the veterinary surgeon should be called in immediately. He may be able to remove all diseased tissue by operation. Neglected cases are often impossible to cure. The external application of poultices or blisters is useless.

Ruminal Fistula

However mot all types of fistula are disease condition and require treatment, even sometimes we induce fistula for treatment of the animal. An example of such condition is the ruminal fistula that is created for treatment of cases of diaphragmatic hernia in pregnant animals to avoid fatal tympany during pregnancy, after which the animal can be slaughtered.

 The condition is not only recommended in pregnant animals having diaphragmatic hernia, but also in chronic recurrent ruminal tympany that usually occurs in calves of 3-9 months. It causes unthriftiness resulting from reduced feed intake. Fistula affords symptomatic relief and is rapidly produced. Alternatively, self-retaining disposable calf trocar may be used for a few days, but requires to be cleaned regularly with metallic trocar to avoid blockage.

Technique: -

Once the site has been cleaned and disinfected, and the local anesthetic injected, an incision about 5 cm for sheep and about 10 cm for cattle is made in the ventro-caudal direction through the skin, following the line identified previously.

The underlying abdominal muscles and peritoneum are separated by blunt dissection to form an opening in the abdominal wall. This requires considerable physical strength with large animals such as buffaloes and the bold use of the scalpel to cut to the peritoneum is less traumatic to the animal.

On reaching the peritoneum, this is cut and the rumen wall which lies immediately below is drawn to the exterior to form a fold and held with two “Alice” forceps. The brass clamp is applied and the screws tightened. Sutures should be placed through the skin and under the clamp and are tied to the clamp at both ends. These sutures hold the clamp to the skin and also prevent accidents which can occur if the rods catch on the sides of the pen. Stitching the skin is one of the most difficult aspects of the operation, particularly with buffaloes, and a sharp cutting needle is needed.

In ten to fourteen days the rumen fold held by the clamps will slough off and can be removed quite easily. A flexible rubber cannula or rigid cannula prepared is inserted and clamped into position.