Anorectal Fistula Surgery: Sphincter Sparing Operations



Fig. 3.1
Surgical technique for fibrin sealant injection. a The dual lumen catheter is inserted through the external opening towards the internal opening. b The fibrin sealant is injected at the internal fistula opening. c The catheter is withdrawn through the fistula as the fibrin sealant fills the entire space. Adapted from Singer et al. [21]





Results


A variety of retrospective and prospective trials have been conducted examining the success of fibrin sealant to treat anal fistula. Table 3.1 includes a data from a sampling of trials. Nearly all trials are relatively small, and most are retrospective, institutional experiences. It is clear that the success rates of fibrin sealant injection are highly variable, with success ranging from 14 to 84% in this group. Although not a formal weighted average, it can be seen that the largest number of trials suggest success rates in the range of 50–70%.


Table 3.1
Results of selected trials of fibrin sealant injection for anal fistula






















































































































Author

Number patients

Healing rate (%)

Incontinence rate

Complications

Jurczak [7]

31

84

0

0 complications

Tinay [8]

19

78

NR

0 complications

Haim [9]

60

74

0

0 complications

Vitton [10]

14

71

NR

0 complications

Mishra [11]

30

70

0

1 itching

Sentovich [12]

48

69

0

1 new fistula

De Oca [13]

28

68

0

0 complications

Lindsey [14]

19

63

0

1 abscess

Maralcan [15]

46

63

0

0 complications

Adams [16]

36

61

0

10% abscess

Cintron [17]

79

61

NR

NR

Zmora [18]

60

57

0

4 pruritus, 1 rash, 1 draining sinus, 1 abscess

Hjortrup [19]

23

52

NR

0 complications

Yeung [20]

40

50

NR

0 complications

Singer [21]

75

35

0

1 abscess

Lougnarath [22]

42

31

0

0 complications

Buchanan [23]

22

14

NR

NR


NR Not reported


Incontinence


Although most of the retrospective and prospective trials have failed to formally assess continence with validated survey instruments or anal physiology, there are no reports, even anecdotal, of postoperative incontinence. This in fact, is consistent with clinical experience. There is minimal manipulation of the tissues, and no injury to the sphincter fibers or pudendal nerves, therefore incontinence would be unlikely. Aggressive debridement of the fistula could potentially injure muscle fibers, however, careful manipulation of the curette or fistula brush should avoid this complication. Another potential source of incontinence would be a robust fibrotic reaction to the fibrin sealant. Fortunately, the inflammatory reaction to the sealant is minimal. Many authors do not report incontinence rates, although most report a zero rate (see Table 3.1).


Abscess


Postoperative abscess is a known complication of nearly all anorectal operations, including fibrin sealant injection. Most trials report zero infections, and some trials report a rate <5% [14, 18, 21]. One trial [16] reports a 10% rate of abscess. It should be noted the external opening was closed in most of these patients. This practice is generally not shared by other authors and the external opening is specifically left open to drain. New fistulas have been reported after fibrin sealant injection [12]. This may be related to a postoperative abscess, or possibly to overzealous probing of the existing fistula.


Unique Complications


There are several potential complications unique to fibrin sealant injection. Early expulsion of the clot is one suspected cause of failure. The exact incidence of early expulsion of the clot is unknown, as this specific complication is difficult to capture in clinical trials. Patients may not identify the fibrin clot on the dressings or after bowel movements.

Another unique complication of this procedure is a reaction to one or more of the specific components of the sealant. Currently available commercial products such as Evicel® (Ethicon, Somerville, NJ) or Tisseel® (Baxter Healthcare Corporation, Deerfield, IL), contain human products. Hypersensitivity to aprotinin is a potential complication, although there are no reports of patients having sustained this complication related to treatment of anal fistula. Another potential complication includes transmission of infectious agents, such as prions causing Creutzfeldt–Jakob disease. Most manufacturers of fibrin sealant have removed bovine components due to concern for hypersensitivity to bovine proteins or transmission of infectious diseases such as bovine spongiform encephalopathy. Again, these have never been reported as consequences of the treatment of anal fistula, but remain potential complications of the fibrin sealant itself.


Implications for Further Treatment


As fibrin sealant injection does not require any incisions or tissue transfer, there is almost no deformity of the anus, injury to the sphincter, or fibrosis of the soft tissues. This means the procedure is repeatable, although rates of healing with repeat treatment are diminished, except in one series, [21] compared to initial treatment. Additionally, there is little or no effect on subsequent treatment by other techniques. This makes it a safe and reasonable choice as an initial treatment option. This is especially true in high risk patients, such as those with Crohn’s disease or impaired continence. Fibrin sealant injection can be performed with essentially no risk of incontinence or negative effects on subsequent treatments if necessary.



Anal Fistula Plugs



Brief Description


The success of fibrin sealant, even if modest, to treat anal fistulas established the concept of treating anal fistula by insertion of a material into the fistula in order to promote healing. Fibrin glue was used to provide a biologic scaffolding, which promoted fibroblast ingrowth and scar formation. This treatment strategy became the basis for application of newer materials, such as anal fistula plugs. The first commercially available product was the Biodesign® anal fistula plug, formerly Surgisis® anal fistula plug (Cook Medical, Bloomington, IN). The Biodesign® material is made from porcine small intestine submucosa. The manufacturing process removes the cells from the material, leaving a collagen rich extracellular matrix which facilitates ingrowth of vascularized tissue. Biodesign® had been used for abdominal wall reconstruction in the setting of contaminated wounds. It appeared to be relatively resistant to infection, which suggested that it would be a suitable choice for obviously contaminated anal fistula. The plug is simply inserted into the fistula, secured at the internal opening, and it then functions as a biologic scaffolding for scar ingrowth. The Biodesign® is replaced by scar tissue in the months following implantation.

The successful application of the Biodesign® anal fistula plug confirmed the viability of the fistula plug strategy. However, its success was not uniform. Surgeons believed that some of the failures were due to early plug extrusions, mismatch between the size of the plug and the diameter of the fistula, and performance of the Biodesign® material in the setting of heavy bacterial contamination. In order to address these specific concerns, a second anal fistula plug was developed. The GORE® BIO-A® Fistula Plug (W.L Gore & Associates, Newark, DE) is made from a non-woven web of polyglycolic acid: trimethylene carbonate fibers that form a 3D matrix of open, highly interconnected pores. This entirely synthetic material is hydrolyzed within 3–6 months following implantation. After the material is hydrolyzed, no prosthetic material remains in the fistula. In addition, rather than a simple conical design, the BIO-A® fistula plug was designed with two significant changes. First, a disk of the material was placed at the internal opening. This facilitated a more secure anchoring of the internal aspect of the plug to the internal sphincter. Second, the body of the plug is composed of six tubes of material. This allows the surgeon to remove a number of tubes so as to approximate the overall girth of the plug to the diameter of the fistula tract.

Fistulas treated with plugs are most often drained with a loose seton for 6–12 weeks preoperatively. The fistula is managed as with fibrin sealant injection: careful probing, gentle debridement, and flushing. The Biodesign® plug is dragged with a suture from the internal opening to the external opening. The body is conical, and so gentle traction is applied until the plug fits snugly within the fistula. It is secured with absorbable sutures at the internal sphincter. The BIO-A® plug is also pulled through the internal opening with a suture. The disk of material at the internal aspect can either be secured with simple suturing, or buried in a small submucosal pocket. Patients are typically discharged home postoperatively with instructions for light activity. Sitz baths avoided so as not to promote hydrolysis of the BIO-A® material.


Results


Results of treatment with anal fistula plugs have been variable. The publications referenced in Table 3.2 reveal healing rates from 14 to 80% for the Biodesign® fistula plug, and 16–73% for the GORE BIO-A® fistula plug. Initial reports were quite promising, [25, 26, 28] however these data were generated by a single institution, and subsequent results have been less successful. O’Riordan [24] published a systematic review of 20 trials, including 530 patients, demonstrating healing with the Biodesign® fistula plug to be from 20 to 86%. The weighted mean rate of healing in non-Crohn’s patients was 54% and in patients with Crohn’s disease was 55%. As it is relatively newer, there are fewer publications documenting the success rate with the BIO-A® fistula plug. Most publications suggest the efficacy of the BIO-A® plug is similar to the Biodesign® plug [4045].


Table 3.2
Results of selected trials of anal fistula plug to treat anal fistula
























































































































































Author

Number patients

Healing rate (%)

Incontinence rate (%)

Other complications

Biodesign ®

Johnson [25]

15

87

NR
 

Champagne [26]

46

83

NR

9% early extrusion

Ellis [27]

63

81

0

1% early extrusion

O’connor [28]

20

80

NR

0

Schwander [29]

60

62

0

3% early extrusion

Ky [30]

45

55

0

11% abscess

Han [31]

114

54

NR

10% early extrusion

Thekkinkattil [32]

43

44

NR

22% early extrusion

McGee [33]

42

43

0

0

Van Koperen [34]

17

41

0

41% early extrusion

Cintron [35]

73

38

0

9% early extrusion, 5% abscess

Hyman [36]

43

32

NR

NR

Christoforidis [37]

37

32

0

19% early extrusion, 14% antibiotics for pain and drainage

El-Gazzaz [38]

33

25

0

9% early extrusion

Safar [39]

35

14

0

9% early extrusion; 14% abscess

GORE BIO-A ®

Ratto [40]

11

73

0

0 early extrusion

Heydari [41]

48

69

0

0 early extrusion

Ommer [42]

40

58

0

5% early extrusion, 3% abscess

Buchberg [43]

10

55

0

NR

Herold [44]

60

52

0

10% early extrusion

Stamos [45]

93

49

11

9% early extrusion, 12% infections, 2% new fistula

De la Portilla [46]

19

16

5

5% early extrusion, 5% infection


NR Not reported


Incontinence


As the fistula plug procedures do not involve division of sphincter fibers, the risks of incontinence should be minimal. In fact, there is little evidence that either type of fistula plug causes postoperative incontinence. As with fibrin sealant, most publications do not document formal evaluation with validated survey instruments or physiologic testing, but the number of patients with postoperative incontinence is minimal. O’Riordan et al. identified 0 patients with worsening continence in their review of 8 trials including 196 patients. Narang [47] performed a systematic review of 6 trials including 221 patients treated with BIO-A® fistula plug and identified worsening continence in 5.8% of patients. Interestingly, Stamos [45] et al. evaluated patients with the Wexner Score, and found that postoperative scores improved after treatment with the BIO-A® plug in the overall population. However, 11% of patients documented a worsening score. The authors speculate that patients may not be capable of accurately differentiating true incontinence from fistula drainage.


Abscess


Fistula plugs have been associated with postoperative abscess. The external fistula opening is specifically left open to drain; in fact, should be further opened to promote drainage of the contaminated tract. Trials included in Table 3.2 report abscesses to occur 5–14% [30, 35, 39, 42, 45, 46] Garg [48] conducted a systematic review of 25 publications including 317 patients, which identified 10% rate of abscess in trials reporting complications.


Unique Complications


Both types of anal fistula plugs are at risk for early postoperative extrusion of the plug itself. Part or the entire plug may expel prior to adequate tissue ingrowth. The exact time required for the plugs to remain in place is unknown, however patients presenting with part or the entire plug within the first 2 weeks postoperatively seem very unlikely to obtain the full benefit of the operation. In the case of partial plug fallout, it is unclear if the benefit of the operation persists if the plug remains at the internal opening. This is likely to be the pathologic part of the fistula, the abnormality that keeps the fistula patent, however, so few such cases are reported that no conclusions may be drawn. Early fallout may be related to inadequate techniques of securing the plug at the internal opening. A consensus conference was convened in order to standardize best practices related to the Biodesign® plug [49]. The BIO-A® plug may be directly sutured or buried in a submucosal pocket. Inadequate evidence exists to recommend one technique over the other. Most of the trials represented in Table 3.2 suggest a 5–10% rate of early plug extrusion. Van Koperen [34] reports a fallout rate of 41%, however this was in a small number of patients. The trial was prematurely closed due to unacceptable results. The systematic reviews of patients treated with Biodesign® document an extrusion rate of 19% in 432 patients [48] and 8.7% in 530 patients [46]. The systematic review of patients treated with BIO-A® reveals an extrusion rate of 5% in 221 patients [47].

Some patients experience a significant inflammatory response to the plug material. This is a risk factor related to any foreign material implantation. This may be an allergy in the case of porcine tissue, or a simple inflammatory response to the BIO-A® material. This has not been formally characterized enough to understand the relationship to healing rates.


Implications for Further Treatment


Similar to fibrin sealant, the insertion of an anal fistula plug is a low risk procedure. Typically, if the plug fails, the wound simply continues to drain. There is some degree of inflammatory response to either material, and this may be variable between patients, but there is not significant disruption of the sphincter muscle fibers or the nerves. There is minimal disfigurement of the normal anatomy of the anus. Therefore, insertion of anal fistula plugs may be considered a first line therapy, provided the surgeon appropriately counsels the patient regarding the expected healing rate. It is also an excellent first line therapy in patients with marginal or impaired continence, chronic diarrhea, or Crohn’s disease.


Flaps (Endorectal Advancement Flap and Dermal Advancement Flap)



Brief Description


Flap coverage of a chronic wound is a commonly employed wound closure strategy. This principle of transfer of normal tissue to an abnormal, nonhealing tissue bed has also been applied to anal fistula. The internal fistula opening is believed to be the pathological site. If healthy tissue can be transferred onto and subsequently heal the internal opening, then the remainder of the tract should eventually heal. This may be accomplished by transfer of tissue from within the rectum, as endorectal advancement flap, or from the perianal skin, as a dermal flap. Flaps are technically more challenging to perform than fibrin sealant or fistula plugs. Thorough knowledge of the relevant anatomy, and precise dissection of the appropriate tissue plans are critical to perform a safe procedure. This can be particularly difficult in patients that have undergone previous operative procedures. Fibrosis surrounding the fistula can make dissection of the flap quite challenging.

Endorectal advancement flaps were the initial flaps described to treat anal fistula, and have been widely adopted. Clinical experience, and therefore published data, are extensive. The endorectal advancement flap is designed as a broad based flap originating well proximal to the internal fistula opening. The endorectal advancement flap is often called a mucosal flap, which is somewhat of a misnomer, as the flap is generally thicker than mucosa alone. A purely mucosal flap is at high risk to become ischemic and retract. The flap should in fact incorporate the submucosa and even a small amount of muscle. Injection of an epinephrine containing solution into the submucosal space can facilitate this dissection and aid hemostasis. A broad based flap is prepared and generously mobilized. The internal opening should be debrided, and sutured closed with absorbable sutures. The distal aspect of the flap is debrided and finally secured just distal to the internal opening.

The dermal flap (also called dermal island flap, island flap, or anocutaneous flap), described by Nelson et al. [73], also transfers normal tissue to the internal opening. This flap however utilizes perianal skin. The fistula is flushed, and the internal opening closed as with endorectal advancement flaps. Either a “U” shaped, or teardrop-shaped incision is then created at the perianal skin in order to create a broad based flap of skin and subcutaneous fat, including the fistula tract itself. This tissue is then advanced into the anal canal, and sutured overlying the internal opening. The external wound may be closed, or left open to avoid tension on the flap.


Results


The results of flaps are more consistent than the results of fibrin sealant or anal fistula plugs. Table 3.3 details selected publications with healing rates mostly in the range of 60–80% for both endorectal advancement flaps and dermal flaps. Soltani [50] published a systematic review of 35 studies including 2065 patients who underwent mucosal advancement flaps. Successful closure was achieved in 76% (37–99%) of patients. Recurrences were noted up to 2 years postoperatively.


Table 3.3
Results of selected trials of endorectal advancement flaps and dermal flaps


































































































Author

Number patients

Healing rate (%)

Incontinence rate (%)

Other complications

Endorectal advancement flap

Aguilar [51]

189

99

10

1% anal stenosis, 1% bleeding

Golub [52]

164

97

15

8% urinary retention, 1% bleeding

Wedell [53]

30

97

28
 

Uribe [54]

60

93

20
 

Ortiz [55]

103

93

8
 

Ortiz [56]

91

82

12
 

Roig [57]

71

82

28
 

Dubsky [58]

54

76

29
 

Schouten [59]

44

75

35
 

Van Koperen [60]

80

74

NR
 

Koehler [61]

42

74

32
 

Jarrar [62]

98

72

43
 

Mitalas [63]

87

69

3
 

Ellis [64]

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Oct 18, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Anorectal Fistula Surgery: Sphincter Sparing Operations
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