**5.1 Park's classification**

Park's classification of fistula-in ano remains popular as the standard terminology used by surgeons. It was published in 1976, based on operative findings of 400 patients over a span of 15 years [5]. The 4 main types are commonly used and reproduced in literatures. However, minimal attention was actually paid to the 14 sub-types in his original report (refer to **Figure 2**). Park's classification relied on intra-operative findings as it presented, and focused on the position or configuration of the fistula tract in relation to the external sphincter [5]. There were several disadvantages of this classification.

a. It does not stratify the complexity of each type of fistula, e.g. low or high fistula, single or multiple tracts.

#### **Figure 2.**

*Park's Classification in 1976. 4 main types with its sub-types (diagrams obtained from Park et al, 1976. A classification of fistula-in-ano. Br J Surg. 1976;63[1]:1–12). [5]*


## **5.2 Eisenhammer's classification**

Eisenhammer published his final evaluation (refer to **Table 4**) based on low or high fistula, location of infection and pattern of spread. It was a useful guide for surgeons to predict the location of internal opening (intersphincteric infection) and course of fistula tract [6]. Eisenhammer stated that his series was mainly from private practice where all the patients presented to him were new cases, thus reporting the actual natural progression and patterns [6]. It is by far the most complete set of classification and focused on patterns of fistula, while stratifying each type by complexity. However, it did not gain popularity due to its' complex terminologies.

#### **5.3 St James University Hospital classification**

In year 2000, St James University Hospital improved Park's classification using Magnetic Resonant Imaging (MRI) studies. They analyzed 300 cases and classified fistula to five grades [16]. Essentially an anatomical classification, this classification refined the findings of Parks based on MRI (as shown in **Table 1**), splitting each of Park's type I (intersphincteric fistulas) & II (transphincteric fistulas) in two further grades (grade I into I & II and grade II into III & IV) and fused grade III & IV into one grade (grade V) [16]. This classification attempts to stratify fistula into simple or complex, allowing clinicians to judge the use of simple fistulotomy or more complex strategies/expert referrals. However, like Park's classification, it does not guide clinicians on the location of intersphincteric sepsis nor if the fistula is low or high. Furthermore, recent publications showed that not all intersphincteric fistulas are simple, and not all transphincteric fistulas are complex [7, 12].


#### **Table 1.**

*Comparison of St James Classification and Park's Classification. The former recognizes the need to stratify Park's Type 1 and 2 into simple and complex (information extracted from Morris et al, 2000. MR imaging classification of perianal fistulas and its implications for patient management, Radiographics 20 [2000] 623-635 discussion 635-7) [16].*
