Experimental model of fistula-in-ano.
OBJECTIVE
This study was designed to create and evaluate an experimental porcine model of fistula-in-ano.


METHODS
Initial cadaveric dissection enabled refinement of the technique for fistula formation and histoanatomical study of the porcine anal canal. Subsequently, three surgically created fistulas were treated by seton drainage in each of eight male pigs (weight, 38-41 kg). After 26 days, magnetic resonance imaging at 1.5 Tesla was performed and setons removed under general anesthesia, enabling clinical and microbiologic track assessment. Two pigs were killed for histologic fistula track assessment.


RESULTS
Histoanatomical assessment noted a rudimentary internal anal sphincter, together with structures resembling anal glands. Artificial fistulas persisted during seton drainage and were more often associated with fecal than skin-derived organisms compared with both perineal and anal canal swabs (P = 0.002). All six fistulas assessed histologically had a lumen, and abundant surrounding granulation tissue similar to that seen in human fistula-in-ano. Epithelialization was not evident in any track. Fistulas were visualized as high signal tracks using magnetic resonance imaging.


CONCLUSIONS
Porcine anal anatomy resembles that of humans, and an experimental model proved suitable when assessed by magnetic resonance imaging, microbiology, and histologically, which demonstrated abundant granulation tissue. This model could be further used to investigate fistula treatments.
Buchanan
Gordon N
GN
Department of Surgery, St. Mark's Hospital, Harrow, United Kingdom.
Sibbons
Paul
P
Osborn
Mike
M
Bartram
Clive I
CI
Ansari
Tahera
T
Halligan
Steve
S
Cohen
C Richard G
CR
D000818:Animals; D004195:Disease Models, Animal; D005401:Fissure in Ano; D008279:Magnetic Resonance Imaging; D008297:Male; D012003:Rectal Fistula; D013552:Swine