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By H. Rendell. LeMoyne-Owen College.

Selective The instructive theory (of antibody formation) was a theories included the side chain theory of Paul Ehrlich hypothesis that postulated acquisition of antibody speci- proposed in 1899 cheap viagra 75 mg with amex zma impotence, the natural selection theory proposed by fcity after contact with a specifc antigen (Figure 7 cheap 75 mg viagra visa erectile dysfunction hypertension drugs. Niels Jerne in 1955, and the cell selection theory proposed According to one template theory of antibody formation, it by Talmage and by Burnet in 1957. Burnet termed his ver- was necessary that the antigen be present during the process sion of the theory the clonal selection theory of acquired of antibody synthesis. The basic tenets of the clonal selection theory theory, uncommitted and specifc globulins could become have been substantiated by the scientifc evidence. The selective theories maintained that cells are genetically pro- cell released the complementary antibodies, which rigidly grammed to react to certain antigenic specifcities prior to retained their shape through disulfde bonding. They are in sharp contrast to the instruc- had to be abandoned when it was shown that the specifcity of tive theories which postulated that antigen was necessary to antibodies in all cases is due to the particular arrangement of serve as a template around which polypeptide chains were their primary amino acid sequence. This template theory was plate theories that recognized the necessity for antibodies to abandoned when antibody was demonstrated in the absence be synthesized by amino acids, in the proper and predeter- of antigen (Figure 7. Instructive theories were abandoned comprised of parallel membranes that are connected to the when immunologic tolerance was demonstrated and when nuclear membranes. Lipids and selected proteins are syn- antigen was shown not to be necessary for antibody synthe- thesized in this organelle. Electron microscopy reveals rough endoplasmic anamnestic (memory) immune response. Antibody speci- reticulum, which contains ribosomes on the side exposed to fcity depends on the variable region amino acid sequence, the cytoplasm, and smooth endoplasmic reticulum without especially the complementarity-determining or hypervari- ribosomes. Selected membrane and organelle proteins, as well as secreted pro- B teins, are synthesized in the rough endoplasmic reticulum. They take part specialized secretory proteins have abundant rough endo- in transmembrane targeting of selected proteins. Following formation, hold some proteins that are to be inserted into membranes in proteins move from the rough endoplasmic reticulum to the intermediate conformation in the cytoplasm until they inter- Golgi complex. Besides BiP, they include heat from the endoplasmic reticulum and fuse with Golgi complex shock protein 70 and 90 and nucleoplasmins. Once secreted proteins reach the endoplasmic reticulum lumen, they do not have to cross any further barri- Somatic hypermutation is the induced increase in fre- ers prior to exit from the cell. This increase leads to the synthesis of variant antibod- important step toward understanding the generation of diver- ies, some of which have a higher affnity for antigen. Somatic sity in the production of antibody molecules, a puzzle fnally mutation may occur in germinal centers. T cell receptor genes do not The unitarian hypothesis was the view that one type of undergo somatic hypermutation. This view was in contrast to the earlier belief that tion enhances diversity of an antibody molecule’s light and separate antibodies accounted for every type of serological heavy chain variable regions. Usually, more than one class of somatic mutations more often than do IgM antibodies. It is immunoglobulin may manifest a particular serological reac- a mechanism whereby point mutations are introduced into tivity such as precipitation. BiP is a chaperonin that binds unassembled heavy and light chains after they are synthesized in the endoplasmic reticu- Switch refers to the change within an immunologically com- lum. The signal hypothesis is a proposed mechanism for selection Isotype switching does not alter the antigen-binding variable of secretory proteins by and for transport through the rough region of the chain at the N-terminus. The free heavy and light chain leader peptide is postulated to facilitate the joining of polyribosomes Switch cells are a subset of T lymphocytes that governs forming these molecules to the endoplasmic reticulum. It also isotype differentiation of B lymphocytes exiting the Peyer’s refers to the release of heavy and light polypeptide chains patches to ensure that they become IgA-producing plasma through the endoplasmic reticulum membrane into the cis- cells when they home back to the lamina propria of the intes- ternal space followed by immunoglobulin secretion once the tine from the systemic circulation. This refers to the pathways whereby proteins reach their proper cellular des- Leader sequence: See leader peptide. Important to protein targeting is the signal sequence, which is a short amino acid sequence at the amino terminus of Switch defect disease: See hyperimmunoglobulin M syn- a polypeptide chain. A transfectoma is comprised of antibody-synthesizing cells that are generated by introducing antibody genes that Signal sequence: See signal hypothesis. Chaperones are a group of proteins that includes BiP, a pro- tein that binds the immunoglobulin heavy chain. Chaperones The switch region is the amino acid sequence between the aid the proper folding of oligomeric protein complexes. They constant and variable portions of light and heavy polypeptide prevent incorrect conformations or enhance correct ones. This amino acid segment is encoded Chaperones are believed to combine with the surfaces of by D and J genes. Immunoglobulin Synthesis, Properties, Structure, and Function 267 Specifc switch region sequences are critical for switching of hypermutability early in the animal’s life. Also early in from one immunoglobulin isotype to another and from one life, the “forbidden” clones of antibody-forming cells (i. During isotype switching, the active heavy the cells that make antibody to the animal’s own antigen) chain V-region exon undergoes somatic recombination with a are still destroyed after encountering these autoantigens. Antigen would have no effect on most lymphoid Switch site refers to breakage points on a chromosome cells, but it would selectively stimulate those cells already where gene segments unite during gene rearrangement. It serves as and proliferate into a clone of cells, producing antibody an identifcation site for V region gene translocation in the of that specifcity. Burnet introduced the forbidden clone process of switching gene expression from one immunoglob- concept to explain autoimmunity. There are numerous switch antibody against a normal self antigen were forbidden and sites for each gene encoding the C region. During fetal develop- ment, clones that react with self antigens are destroyed or Clonal selection refers to antigen-mediated activation and suppressed. Talmage proposed a cell selection the- tides derived from the antigen in the case of T lymphocytes.

The onset of radial tunnel syndrome can be acute following twisting injuries to the elbow or as a result of direct trauma to the area overlying the radial tunnel generic 50 mg viagra with mastercard importance of water. More commonly discount viagra 100mg fast delivery erectile dysfunction blood pressure medications side effects, the onset of radial tunnel syndrome is insidious and is usually the result of misuse of overuse of the elbow joint and proximal forearm from repetitive pronation and supination. Radial tunnel syndrome has been reported in orchestra conductors, Frisbee 390 players, and swimmers. A ganglion cyst is shown at the level of the radial in cross-sectional ultrasound image. Ganglion cyst of radiocapitellar joint mimicking lateral epicondylitis: role of ultrasonography. A Tinel sign will be present at the point where the radial nerve passes through the radial tunnel and the nerve will be tender to palpation. Patients suffering from radial tunnel syndrome exhibit pain on active resisted supination of the forearm and a positive radial tunnel compression test. The radial tunnel compression test is performed by tightly compressing the area over the radial tunnel for 30 seconds (Fig. The test is considered positive if the patient experience dysesthesias in the distribution of the radial nerve and increasing weakness of finger extension. Patients suffering from radial tunnel syndrome will exhibit a positive radial tunnel compression test is performed by tightly compressing the area over the radial tunnel for 30 seconds. The test is considered positive if the patient experience dysesthesias into the distribution of the radial nerve and increasing weakness of grip strength. As the deep branch of the radial nerve exits the confines of the radial tunnel beneath the distal margin of the arcade of Frohse as the smaller posterior interosseous nerve, it is subject to compression and entrapment in a manner analogous to the compromise of the deep branch of the radial nerve at the proximal margin of the arcade. Compromise of the posterior interosseous nerve as it exits beneath the distal arch and at points distal is more properly termed posterior interosseous syndrome rather than radial tunnel syndrome. Compromise of the posterior interosseous nerve along its course will produce dysesthesias and aching pain similar to that seen in radial tunnel syndrome, although functional disability may be more limited to finger drop due to the more distal compromise of the nerve. If complete wrist drop commonly seen in radial nerve or Saturday night palsy is identified, the clinician should realize that the site of radial nerve compromise is more proximal as the common radial nerve provides innervation to the extensor carpi radialis longus muscle responsible for the majority of wrist extension functionality (Fig. As with radial tunnel syndrome, the posterior interosseous nerve is subject to compression and entrapment by soft tissue masses, direct trauma, bony excrescences, aberrant fibrous bands, and vascular abnormalities (Fig. Wrist drop commonly seen radial nerve or Saturday night palsy is caused by more proximal compromise of the common radial nerve. Ganglion cyst of radiocapitellar joint mimicking lateral epicondylitis: role of ultrasonography. With the patient in the above position, at a point approximately 4 in above the lateral epicondyle, the intermuscular septum separating the bellies of the brachialis and brachioradialis muscles is identified by palpation. A high-frequency linear ultrasound transducer is placed in a transverse position over the previously identified intermuscular septum (Fig. An ultrasound survey image is obtained and the intermuscular septum separating the bellies of the brachialis and brachioradialis muscles and the radial nerve is identified (Fig. The ultrasound transducer is turned to the longitudinal plane and the path of the radial nerve is traced distally until the bifurcation of the nerve is identified (Figs. Once the bifurcation of the nerve is identified, the ultrasound transducer is turned back to the transverse position and the superficial and deep nerves will begin to separate appearing on transverse ultrasound scan as two eyes behind spectacles (Fig. The deep branch of the radial nerve then passes beneath the proximal margin of the arcade of Frohse (Fig. The deep branch is then followed distally through the radial tunnel until it exits beneath the distal margin of the arcade and becomes the smaller posterior interosseous nerve (Figs. Color ultrasound is then used to identify any adjacent blood vessels that might be injured during the injection procedure (Fig. The deep branch of the radial nerve is carefully evaluated along their course for compression and entrapment by the arcade of Frohse, soft tissues masses, ganglia, tumors, bone spurs, aberrant fibrous bands, and direct trauma (Figs. The continuation of the deep radial nerve, the posterior interosseous nerve is then evaluated for pathologic conditions that are producing the patients symptomatology (Figs. Proper placement of the ultrasound transducer for ultrasound evaluation of the radial nerve at and below the elbow. Transverse ultrasound view of the intermuscular septum between the brachioradialis and brachial muscles with the radial nerve nestled between. Longitudinal view of the radial nerve within the intermuscular septum between the brachioradialis and brachialis muscles. Longitudinal view of the radial nerve demonstrating the bifurcation of the deep and superficial branches of the radial nerve. Once the bifurcation of the nerve is identified, the ultrasound transducer is turned back to the transverse position and the superficial and deep nerves will begin to separate appearing on transverse ultrasound scan as two eyes behind spectacles. Ultrasound image of the deep branch of the radial nerve immediately proximal to the arcade of Frohse. Ultrasound image demonstrating the relationship of the relationship of the deep branch of the radial nerve and the arcade of Frohse. Transverse ultrasound scan of the deep branch of the radial nerve as it travels beneath the proximal portion of the arcade of Frohse through the radial tunnel. Longitudinal ultrasound view of the posterior interosseous nerve exiting beneath the distal margin of the arcade of Frohse. Color Doppler will aid in the identification of adjacent vessels when performing ultrasound evaluation of the radial nerve for radial tunnel syndrome.

Antibodies against microflariae facilitate adherence to resolution of lesions in animals that remain refractory to of granulocytes in vitro viagra 50 mg free shipping erectile dysfunction viagra does not work, and eosinophils and neutrophils further challenge viagra 75mg amex erectile dysfunction treatment south florida. Infected subjects Malaria is a disease induced by protozoan parasites develop elevated IgE which may worsen ocular lesions by (Plasmodium species) with a complex life cycle in a mos- contributing to acute infammation. Cell-mediated immu- teins are formed at each morphologically distinct stage in the nity is downregulated to antigens that are specifc and non- life cycle. The asexual stage in the blood stream causes the specifc for the infectious agent. Metronidazole is the drug of choice to treat intestinal and Ocular pathology is the most serious effect of this disease extraintestinal amebiasis and neurogenital trichomoniasis, affecting both anterior and posterior segments of the eye. Even though egg identifca- tal control but development of a protective vaccine would be tion in human excreta has long been the method of diagno- a better solution. Schistosome- derived carbohydrate antigens in the blood are also helpful in Sabin-Feldman dye test is an in vitro diagnostic test for tox- immunodiagnosis. Serial dilutions of patient’s serum are combined schistosomiasis in humans, yet irradiated larvae have been with Toxoplasma gondii microorganisms, and complement is used to immunize cattle. If specifc antibodies against Toxoplasma organisms are present in the serum, complement interrupts the integ- Antigen masking is the ability of some parasites (e. That dilution of patient’s serum in which one half of the Toxoplasma organisms have been fatally injured Strongyloides immunity: Immunoglobulin G (IgG), IgA, and is the titer. IgE classes of immunoglobulin form in response to antigens of Strongyloides stercoralis flariform larvae. The principal Schistosoma immunity: The immune response to the blood humoral responses by the IgG4 subclass may be directed to fukes classifed as schistosomes is complex. The remain- sure to schistosome larval antigens may lead to hypersensitiv- ing IgG subclasses recognize fewer than 20 antigens. Exposure to large endopeptidase together with 31- and 28-kDa proteins are numbers of S. Immunocompromised patients with changes in schistosome infections are linked to deposition disseminated infection may manifest high titers of parasite- of eggs which induce granulomatous reactions in the tissues specifc antibodies. The granuloma is a delayed-type hyper- been claimed by some to facilitate parasite dissemination, sensitivity reaction that is T cell dependent. Multiple immune parameters are activated Strongyloides hyperinfection: Strongyloides stercoralis lar- by these eggs and their antigens leading to a modulation in vae may invade the tissues of immunosuppressed patients with chronically infected individuals. Egg antigens may induce enteric strongyloides infection to produce this condition. Adult worms from a primary infection can continue acid) is a therapeutic agent for African sleeping sickness to survive in individuals resistant to reinfection with fresh produced by trypanosomes. The drug also blocks lysis mediated by experimental animals against cercarial challenge. The main complement by preventing attachment of the membrane target of destructive immunological attack is the migrating attack complex of complement to the membranes of cells. Resistance is correlated with peripheral blood eosino- Taenia solium immunity: Preencystment immunity (early philia in S. Infection-protective immunity) refers to the immune response at the onco- immunity may be associated in elderly persons with IgE sphere penetration site. More than 90% of ment immunity refers to the immune response at the fnal the surface antigens of the young schistosomulum are car- establishment site. Anti-egg antibodies may cross-react with these attacks invading oncospheres since it is resistant to intes- antigens. This would ally not susceptible to immune attack either by coating them- permit IgG antibodies to reach the invading site. Eosinophils selves with host-derived macromolecules that mask parasite also surround invading oncospheres but there is no evi- surface antigens or the worms may shed antigenic macro- dence that they induce injury. When oncospheres that are molecules from the outer tegument, rendering their outer newly hatched reach their establishment site, they transform Immunity against Microorganisms 767 from a stage in which they are highly vulnerable to attack host during acute infection. Tachyzoites in the acute stage of infection are against challenge infection, but there is only a limited supply the principal targets for the protective immune response. This has been remedied by the development of a Tachyzoites induce both antigen-specifc and nonspecifc recombinant taeniid vaccine antigens which have been able to suppressor cells to inhibit induction of the immune response induce protection in animals. Theileria immunity: Immunity against these tick-transmitted Toxoplasmosis is the disease induced by the protozoan par- intracellular protozoan parasites of domestic animals depend asite Toxoplasma gondii. Humoral immune responses directed against schizonts and piroplasms Trichuris trichiura immunity: Immune responses against are insignifcant in the development of natural protective these worm infections of humans include specifc IgG, IgA, immunity. The IgG level increases with the gous challenge and developing immunity that persists for 3 level of the infection, but elevated IgA levels may be associ- to 5 years. Infection with sporozoites and the development of ated with diminished worm burdens. The cellular response schizonts are critical for the development of natural immunity. Primary infections are followed by 70% of immunized cattle against experimental challenge. Infammatory responses are not believed to contribute humans to the domestic dog roundworm or Toxocara canis to immunity. The immune response is also charac- Tropical eosinophilia is a hypersensitivity to flarial worms terized by development of eosinophilic granulomata which manifested in the lungs. It has been reported in the Near East may appear throughout the body except for the brain. Trypanosome immunity: Vaccination against African Toxoplasma gondii immunity: Both humoral and sleeping sickness known as trypanosomiasis has thus far cell-mediated responses follow infection with T. Even though the antigen that induces a cellular immune response is the principal mediator of resis- protective humoral response is well known as a surface gly- tance to infection, although both cellular and humoral confer coprotein that covers the entire trypanosome, the organism resistance.

Velchuru operations cheap viagra 25 mg on line impotence nasal spray, the incidence of sphincter-cutting procedures Introduction such as fistulotomy decreased from 98 cheap 25 mg viagra mastercard erectile dysfunction treatment chennai. Management depends on the etiology, such following sphincter-sacrificing procedures with anorectal as cryptoglandular pathology (commonest), Crohn’s dis- physiology testing and anal ultrasonography. Patients present as an emergency with anorec- than one procedure in patients from 1. Management of anal fistulae is complex and few employed as cutting and a non-cutting seton, i. In this chapter we discuss, a cutting seton, Ayurvedic-medicated setons have been described for non-cutting seton (or a loose seton) and a chemical seton. Hippocrates in fourth century bc has fibrosis, this in turn creates a fibrosed track for a definite pro- described the use of horsehair and lint to cut the muscle to cedure on a later date. In the last few decades, ksharasutra, the aim is to facilitate controlled transection of sphincter-saving procedures have been increasingly used the sphincter muscle to heal the fistula. However, initial drainage of sepsis and seton placement as a temporary or a permanent remedy still has a role. Seton Material High trans-sphincteric fistula remains a challenge even in the twenty-first century, as curative treatment involves mus- The type of seton used is usually typical to the individual cle cutting leading to potential incontinence. Seton means “thick, stiff hair” in Latin in the a 25-year single-institutional review of 2,267 fistula Webster’s dictionary. A few of the type of setons used are the Ayurvedic-medicated thread [6], braided sutures [7], thread, rubber band [8], penrose drains [9], cable tie seton [10 ], etc. Velchuru Loose Seton and Staged Fistulotomy Technique of Seton Insertion A staged fistulotomy is carried out in high trans-sphincteric Patient can be prone (North America) or lithotomy (United or supra-sphincteric fistulas, when single stage fistulotomy is Kingdom) depending on the surgeon’s preference. Hydrogen in situ for the remaining track to prevent it from closing and peroxide injection into the external opening can help to iden- forming a source of sepsis. Initially, the same study, hydrogen peroxide-enhanced ultrasound the deep sphincter complex was divided and a loose seton increased the accuracy from 62 to 95 % compared to a stan- placed at the remainder distal sphincter. Grooved Lockhart–Mummery healed forming a track around the seton, laying open of the or malleable lacrimal probes have been used to negotiate and track was undertaken with fair results. Sepsis is drained, track is curetted, sec- and only one patient had mild incontinence [20]. Railroad Another large series (n=89) with the same technique in technique has been employed both to insert the seton [18] or patients with complex fistula and anterior fistula in women changing the medicated seton weekly [19] and for regularly concluded that staging fistulotomy was preferable to cutting tightening the cutting seton. In another series It is vital to document a detailed and exact anatomy in the (n=34) of patients with trans-sphincteric and extra- pictorial form in the operative note for future reference. Sitz sphincteric fistulas, recurrence was seen in 6 %, however baths are advised in the immediate postoperative period to nearly 60 % had abnormal incontinence [24]. Loose Seton Similar technique was employed in 47 patients, the recur- rence rates was 9 %, with an overall incontinence of 66 %, The purpose of a loose seton is not to damage or cut the with 25 % having major incontinence [25]. The healing rates sphincter and as the name implies it is placed in the tract and of staged fistulotomy are acceptable, however the inconti- tied loosely. It acts as a Loose Seton Alone drainage and prevents further recurrence of sepsis. For definitive treatment of trans-sphincteric fistula with- ter has also been reported. The sphincter is divided in two and the seton was left to migrate out spontaneously, or if stages, and the seton is used to allow the healing of the the track was superficial a fistulotomy was performed. At the initial presentation of perianal abscess, an experi- enced colorectal surgeon can identify the track and consider primary treatment of the fistula. Primary fistulotomy can be Seton and High Fistulas undertaken with good success rates if the fistula is superficial [21]. If it is a high fistula, or the sphincter muscle thickness Few studies have shown that high trans-sphincteric fistulas unclear, which is often the case due to acute suppuration a can be treated with drainage of inter-sphincteric space, seton should tied loosely for drainage and as a marker for internal sphincterotomy, complete preservation of external definitive surgery in the future [20 ]. Recurrence 8 Seton (Loose, Cutting, Chemical) 47 rates ranged from 15 to 56 % in these studies. In Thomson’s become an important tool in the surgeon’s armamentarium study [29], recurrence (56 %) was treated with laying open from the initial management of fistula-in-ano to complex of fistulas leading to significant major incontinence (47 %). As dis- Incontinence when external sphincter is completely pre- cussed it can be used at the time of initial drainage of abscess served is usually mild (36–62 %) [28, 30 ]. Loose setons as a Seton and Sphincter-Saving Procedures staged fistulotomy have good healing rates, however the incontinence rates can be high. Only a few case studies have used loose draining sepsis and maturing the track due to fibrosis. There setons without transection of muscle, with good healing rates were no increased recurrence rates because of seton [32]. Cutting Seton Seton in Crohn’s The main objective of fistula-in-ano treatment is to get rid of fistulous tract with a good functional outcome. A third of on the etiology, extent of muscle involvement, and propor- Crohn’s patients present with fistulas [34]. Acute suppurative is used for a controlled division of the sphincter to aid in abscess should be treated with incision and drainage. Inflammatory reaction and fibrosis of placement is done to identify the track, drain sepsis, and the transection site prevents retraction of the sphincter most importantly stabilize the disease [5, 28 , 36 – 38 ]. In severe refractory disease, defunction- Appropriate patient selection and identifying the type of ing the bowel might be necessary. Crohn’s proctitis is a fistula is important [46], as a fistulotomy will help heal the contraindication for any local procedures such as rectal fistula, nevertheless this will lead to incontinence.

Posterior secondaries passes through the levators rendering them amongst the most follow a curvilinear trajectory into a posterior midline primary cheap viagra 25 mg overnight delivery erectile dysfunction protocol book review. On the right is an uncom- (b) low transphincteric; (c) supralevator; (d) two variations of mon variant of cryptglandular origin extrasphincteric fistula cheap viagra 50 mg line erectile dysfunction pills viagra. On the left is a variant seen in iatrogenic recurrent 6 Clinical Assessment and Imaging Modalities of Fistula in Ano 33 The concept “complex fistula” is a common term in the In the absence of any complicating factors, most colorectal surgical vernacular, albeit not a part of Park’s classification. The term further may be used to describe those that erative imaging has been debated. It remains unclear that this include multiple tracks, anterior location in females, recur- adds any additional information to the skilled practitioner. It is termed complex because the treat- allowing the practitioner to proceed with an appropriate ment requires a more complicated approach and cannot be definitive procedure at the first operation [13, 14]. The “complex fistula” has been argue that even with complex fistula tracts, definitive a catalyst of much innovation, although no single approach has management at the first procedure is not always possible. The primary goal should be control of anorectal sepsis, with Infections tracking above the levator muscles may ultimately definitive procedure reserved for a time when there is form suprasphincteric or extrasphincteric fistula. The former decreased infection and inflammation of surrounding tissues course between the sphincter muscles; the latter course lateral [15]. Although imaging can serve to correctly identify the to the external sphincter muscle. Abdominal pelvic infections course of the fistula tract in the majority of patients, it may disseminate into the retrorectal and supralevator spaces remains unclear whether the time and expense to perform as well as the ischioanal fossae via Alcock’s canals acutely. They are important to recog- niques are reserved for those whose anatomy is unclear at the nize, because they are often mismanaged due to a failure to time of surgery. A review of 101 patients showed that pri- identify the underlying source—infection in one of the post- mary crypt identification was possible 93 % of the time with anal or posterior space(s): superficial, deep, supralevator, surgery alone. Palpation of the intersphincteric groove with an index finger often reveals palpable induration or a divot in the area Anal fistula arising in the setting of specific diseases should of the originating crypt. Superficial fistula tracts can also be be investigated according to the clinical context in which they palpable from their external opening into the anal canal. The classic example is chronic inflammatory bowel Some authors employ a crochet-type hooked probe to iden- disease—particularly Crohn’s. Others apply a clamp lateral to the mentation of the state of the rectal mucosa assessed by endo- external opening in order “to straighten” the tract. Palpation of the intersphincteric groove and the tissues should be assigned to these patients. All procedures for the surrounding the external opening(s) surgical correction of anal fistula have the potential of altering 3. Injection of the external opening(s) with hydrogen perox- nence are important to document preoperatively. This case underscores the peroxide emanates from two adjacent cypts via radial trajectories. Therefore, passage of the probe as an initial maneuver deeper areas of infection and suggest an origin (such as a may be misleading as well as potentially iatrogenic if a false supralevator, pure intersphincteric, extrasphincteric, or horse- opening is created. This additional information is useful to know Failure to identify a primary internal opening is not before proceeding to the operating room to deal with an uncommon. The most traditional approach in this setting is abscess with appropriate aggressiveness. It is eminently reasonable to back out and obtain enhancement using hydrogen peroxide. Further experience of anatomy, it does depend to a large degree on the examin- is necessary. For this reason, it is ideally use of imaging techniques should be strongly considered. It suited for ultrasound within the anal canal, but may not be as should be noted that the most common reason for extrasphinc- well suited for deeper fistula tracks passing at some distance teric fistula tract development is iatrogenic probing and cre- from the rectum [22]. Moreover, situa- delineate or control the entire fistula tract at the time of the tions in which the interpreter may not have been present at index operation, it is advisable to control what can be identi- the time of the examination implies an additional and signifi- fied and investigate the anatomy further with advanced imag- cant handicap. An exception may be in the acute setting There are several “tricks” to properly performing injec- with suspected abscess. Gas bubbles define the location of an infection where there is a paucity of can create artifact and obscure anatomy. This allows the practitioner to define any amount of hydrogen peroxide should be used during the 6 Clinical Assessment and Imaging Modalities of Fistula in Ano 35 examination. Pressure must be applied to the external opening at the time of injection to prevent retrograde extravasation and increased bubbling. The fistula probe is then passed into and out of the fistulous trajectory following the tract. The internal opening of a fistula tract is defined by the presence of a hyperechoic breach at the level of the internal sphincter. It varies by fistula type, and is most accurate for intersphincteric and transphincteric trajectories. More complex fistulas are more difficult to interpret, and require greater skill on the part of the endosonographer. It has the advan- tage of not being user-dependent for interpretation, as well as the ability to evaluate fistula tracts that course distant from the anus. It may be performed with or without contrast medium, and/or using an endorectal coil.

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