Keywords
anal - rectal - abscess - treatment - evaluation
Introduction
Rectal abscesses are initiated by an irritated and infected cavity located in the crypts and glands at the dentate line of the rectum. These typically occur due to a collection of bacteria, fecal, and/or foreign material that clogs a gland proximal to the anus. Located at the anal verge, perianal abscesses are the most common type of anal abscesses.[1] There are an estimated 100,000 patients in the United States diagnosed with anal abscesses per year. The mean age at diagnosis is 40 years, with men being twice as likely to develop an abscess as compared with women.[2] Most pathogens cultured from anal abscesses are mixed aerobic-anaerobic organisms.[3] While rectal abscesses are a result of an infected rectal gland, 10% of perirectal abscesses are thought to be a consequence of more specific causes such as Crohn's disease, trauma, human immunodeficiency virus (HIV), sexually transmitted diseases (STD), radiation/ chemotherapy, or foreign bodies.[4] These abscesses cause irritation, pain, and discomfort for patients. Delayed diagnosis and treatment can lead to complications, including anal fistulas, sepsis, or necrotizing soft tissue infection (Fournier's Gangrene). It has been estimated that 30 to 70 percent of anorectal abscesses present with a concomitant anorectal fistula. Furthermore, 30 to 40 percent of patients who undergo treatment for anorectal abscess develop an anorectal fistula.[5]
In patients with a suspected anorectal abscess, imaging should be utilized to confirm and localize any suspicious or atypical abscess cavities. Patient presentation typically includes complaints of pain in the anal area, which may be dull, sharp, aching, or throbbing. This may be accompanied by fever, chills, constipation, or diarrhea. Purulent discharge and blood per rectum may also be reported. An ultrasound (US), magnetic resonance imaging (MRI), or computed tomography (CT) scan can confirm the presence or possible progression of an abscess. Ultrasound may be helpful in patients who are immunocompromised, patients who present with unexplained significant anorectal pain, or those at an increased risk of developing abscesses.[6] Ultrasound is utilized to diagnose the extent of the infection by identifying occult abscesses that may, in turn, develop into a more severe infection requiring hospitalization.[6] Surgical treatment of a rectal abscess is common as antibiotics alone cannot fully treat the infection. Once diagnosed, the patient is usually taken to surgery where, under local anesthesia, a cruciate incision is made as close as possible to the anal verge.[6] Following this, blunt instrumentation is utilized to disrupt loculations and ensure no occult abscess pockets remain. Finally, an excisional skin flap is created to provide adequate drainage and prevent premature skin healing over the abscess pocket, which may cause postoperative re-infection.[6]
The passage of time is also essential in the overall treatment of anorectal abscesses. The timing of surgery is dictated by the patient's clinical condition, length of time since initial symptoms, and comorbidities, such as the presence of sepsis, immunosuppression, diabetes mellitus, and diffuse cellulitis.[7] These additional components suggest a prompt surgical drainage. Even in the absence of these factors, surgical drainage should be performed within 24 hours.[7] The diagnosis and treatment of anorectal abscesses are aided by diagnostic imaging, such as ultrasound, followed by surgical incision and drainage (I&D).
As mentioned previously, 30 to 40 percent of patients who undergo treatment for anorectal abscess develop an anorectal fistula, which can increase the chance of further complications and lead to an increased length of stay at the hospital. One retrospective cohort study reported that risk factors associated with chronic anal fistula or recurrent anal sepsis after a first-time episode of perianal abscess include age under forty and being nondiabetic.[8] Hamadani et al. reported that gender, smoking history, perioperative antibiotic treatment, and HIV status were not risk factors for anal fistula or sepsis after rectal abscess treatment.[8] Our study aimed to investigate whether prompt surgery of anorectal abscess led to the mitigation of postoperative complications. Our secondary objective was to assess the role of diagnostic imaging in shortening the time to surgical treatment and evaluate whether the size of a rectal abscess was a factor in recurrence.
Methods
We conducted a retrospective study at Jersey Shore University Medical Center (JSUMC) and Ocean University Medical Center (OUMC) in New Jersey, USA. Patients diagnosed with an anorectal abscess who underwent a surgical procedure between January 1, 2019, and December 31, 2022, were eligible. All procedures were performed by Dr. Glenn Parker, a colorectal surgeon at the institution. Approval from the Institutional Review Board (IRB) (Pro2023–0064) was obtained for an electronic chart review in Epic®. Study data were collected and managed using REDCap electronic data capture tools. Data were to be collected on 54 across four years of emergency room (ER) and outpatient clinic visits. Due to insufficient demographic and chart data, the study excluded six patients. Medical records of patients who had been evaluated by an emergency medicine physician and a colorectal surgeon (GP) were reviewed.
The following data was collected from patient charts in the electronic health record (Epic®): demographics, the patient's history of anal abscess, and pertinent past medical history. Additional data collected from the emergency department's physician notes included the length of time the patient waited before coming into the ER, date and time of admission to ER, date and time of admission to the hospital, length of stay in the ER, length of time from the entry into ER before entry into the operating room (OR), symptoms at the time of admission, wound culture results, blood work on admission and two days postoperatively, and any diagnostic imaging ordered. The following was collected from the colorectal surgeon's note: date seen in the outpatient clinic (if applicable), date of surgery, operation time, presence of fistula at time of surgery, length of hospital stays post-operatively, presence and recurrence of abscess and fistula. The data that was collected from the radiology report included the imaging modality, along with the presence of abscess, size, and location.
Patients who came to the ED presenting with anorectal pain associated with an abscess had undergone an immediate incision and drainage procedure. Subsequently, in cases where an opening in the anal crypt was identified, an anal fistulotomy was performed in the OR; with a seton placed in selected patients. Purulent drainage acquired during the initial drainage or fistulotomy was sent to the microbiology laboratory for wound cultures and anti-bacterial sensitivity. After being discharged, patients were instructed to schedule follow-up appointments with the surgeon to monitor the status of the wound and to check for any potential complications or recurrence.
The data was divided into two cohorts: the recurrent abscess group and the nonrecurrent abscess group. The recurrent group, comprising eleven patients, represented patients who were diagnosed with an anorectal abscess, received treatment, later returned for reassessment, and were found to have a recurrence. On the other hand, the nonrecurrent group, with 37 patients, included all patients who were diagnosed with an anorectal abscess, received treatment and did not return for medical evaluation with symptoms of a recurrent anorectal abscess.
Statistical tests were used to determine which variables were significant factors for recurrence. A non-parametric Savage test was used to detect the differences in time-to-event among the two groups in select outcome variables (length of time between ER admission and OR admission, length of hospital stays post-operatively, and length of time patient felt symptoms of an abscess before coming in for evaluation). The Wilcoxon rank sum test was used to test for the differences in continuous variables between the groups (age, BMI, length of ER stay). The Wilcoxon Rank Sum Exact Test was used to analyze abscess size and mean time from the outpatient clinic to the OR. To compare proportions in categorical variables between the groups, either Pearson's Chi-squared test (for initial diagnosis made by physical exam) or Fischer's exact test (for sex, past medical history, autoimmune disease, symptoms, and initial diagnosis made by US and CT scans) was used. A risk rate of less than 5% was taken to indicate a significant statistical difference.
Results
As depicted in [Table 1], most of the patients (39 of 48; 81%) were men. A total of eleven (23%) patients developed a recurrent abscess after receiving surgical treatment. The recurrent abscess patients were significantly younger than the noncurrent group of patients (35.45 years vs 46.03 years). Many patients (88%; 42 of 48) presented anorectal pain or discomfort. Moreover, 75% of patients (36 of 48) were presented with an anal fistula at the time of initial surgery. All patients (11 of 48; 30%) that reported the presence of hemorrhoids before evaluation did not develop any further complications or recurrent abscesses after receiving surgical abscess treatment. As seen in [Fig. 1], ∼63% of patients (30 of 48) who presented for evaluation were diagnosed with a perianal abscess. The abscesses in the other 18 patients were found in differing areas of the anorectal region ([Figs. 1] and [2]).
Table 1
Patient information of recurrent and nonrecurrent patients, including sex, age, BMI, and past medical history
|
Patient Information
|
|
Recurrent Group (n = 11)
|
Non-Recurrent Group (n = 37)
|
p-value
|
|
Sex
|
|
|
|
>0.99[b] (NS)
|
|
Male
|
9 (82%)
|
30 (81%)
|
|
|
Female
|
2 (18%)
|
7 (19%)
|
|
|
Demographics
|
|
|
|
|
|
Age Range (years)
|
18–54
|
20–89
|
|
|
Mean Age (years)
|
35.45 ± 11.92
|
46.03 ± 18.13
|
0.088[a] (NS)
|
|
Average BMI (kg/m2)
|
25.52 ± 6.46
|
29.77 ± 7.78
|
0.1[a] (NS)
|
|
Symptoms in Anorectal Area
|
|
|
|
|
|
Discomfort, irritation, or pain
|
11 (100%)
|
31 (84%)
|
0.31[b] (NS)
|
|
Swelling
|
3 (27%)
|
14 (38%)
|
0.72[b] (NS)
|
|
Discharge
|
2 (18%)
|
14 (38%)
|
0.29[b] (NS)
|
|
Autoimmune Disease
|
|
|
|
0.63[b] (NS)
|
|
Crohn's Disease
|
3 (27%)
|
3 (8%)
|
|
|
Gastroesophageal reflux disease (GERD)
|
0
|
3 (8%)
|
|
|
Other Medical History
|
|
|
|
|
|
Smoking
|
2 (18%)
|
16 (44%)
|
0.16[b] (NS)
|
|
Hemorrhoids
|
0
|
11 (30%)
|
0.12[b] (NS)
|
|
Anal fistula (at time of initial surgery)
|
10 (91%)
|
26 (70%)
|
0.25[b] (NS)
|
Abbreviation: NS, not statistically significant.
a Wilcoxon rank sum test.
b Fisher's exact test.
Fig. 1 Classification of anorectal abscess. Anal rectal abscesses are classified by their location about the structures comprising and surrounding the anus and rectum: perianal, ischioanal, intersphincteric, and supralevator. (Reprinted with permission from the American Society of Colon & Rectal Surgeons.)
Fig. 2 Anatomical distribution of anorectal abscess location for all patients.
All patients were presented for evaluation at either the Emergency Department (ED) or an outpatient clinic. Fourteen patients (29%) visited an outpatient clinic only before being admitted for surgery, while 71% of patients (34 of 48) went to the ED for evaluation. A physical examination, including a rectal examination, was performed by a resident, or attending physician for those seen in the ED. As depicted in [Table 2], 52% of patients (25 of 48) had only a physical examination without any diagnostic imaging, either in the ED or at an outpatient clinic. Approximately 48% (23 of 48) received diagnostic imaging to rule out other diagnoses. Patients either had a US or CT performed at initial diagnosis. Two of the patients initially had an ultrasound done, however, a CT scan was subsequently performed for further testing.
Table 2
Initial diagnostic technique, imaging vs physical examination. All recurrent abscesses were evaluated using CT
|
Patient Information
|
|
Recurrent Group (n = 11)
|
Non-Recurrent Group (n = 37)
|
p-value
|
|
Initial Diagnosis
|
|
|
|
|
|
Ultrasound
|
1 (9%)
|
2 (6%)
|
0.55[a] (NS)
|
|
CT
|
4 (36%)
|
16 (43%)
|
0.73[a] (NS)
|
|
Physical Exam Only
|
6 (55%)
|
19 (51%)
|
0.85[b] (NS)
|
|
|
Recurrent Group (
n
= 3)
|
Non-Recurrent Group (
n
= 7)
|
p
-value
|
|
Abscess Size (two-dimensional)
|
|
|
|
0.38[c] (NS)
|
|
Size Range in cm2
|
6.21 - 31.05
|
2.17 - 11.07
|
|
|
Mean Size Initial Diagnosis by US or CT in cm2
|
15.69 ± 13.43
|
6.34 ± 3.30
|
|
|
Mean Recurrent Size by CT in cm2
|
27.45 ± 37.25
|
–
|
|
|
|
Recurrent Group (
n
= 2)
|
Non-Recurrent Group (
n
= 10)
|
p
-value
|
|
Abscess Size (three- dimensional)
|
|
|
|
0.86[c] (NS)
|
|
Size Range in cm3
|
11.76 - 121.94
|
21.28 - 1365.84
|
|
|
Mean Size Initial Diagnosis by CT in cm3
|
66.85 ± 855.73
|
233.38 ± 438.55
|
|
|
Mean Recurrent Size by CT in cm3
|
120.50 ± 37.05
|
–
|
|
Abbreviation: NS, not statistically significant.
a Fisher's exact test
b Pearson's Chi-squared test.
c Wilcoxon rank sum exact test.
The size of the rectal abscesses was retrieved from the radiology reports. A small majority of imaging reports (52%; 12 of 23) measured the abscess three-dimensionally. In one patient who received CT imaging, no deep-seated abscess was found, however, the patient's abscess was seen on physical examination and treated with an I&D procedure. Of the patients who received diagnostic imaging, 22% (5 of 23) later returned to the ED for evaluation of a recurrent abscess due to complaints of pain and discomfort. When a CT scan was taken to measure the recurrent abscess, the mean recurrent size was greater than the size during initial diagnosis, in both 2D (15.69 cm2 vs 27.45 cm2) and 3D (66.85 cm3 vs 120.50 cm3) measurements ([Table 2]).
As shown in [Table 3], a statistically significant finding (p < 0.05) was that patients who received imaging spent more time in the ER than patients who did not receive imaging (7.58 hours vs 3.72 hours). Additionally, patients who were initially evaluated at the outpatient clinic and did not have imaging performed waited, on average, 11.65 times longer than those who received imaging ([Table 3]). Similarly, patients who developed a recurrent abscess after initial evaluation at the clinic waited 3.41 times longer than those who did not develop a recurring abscess ([Table 4]). Of note, after initial evaluation in the ED, recurrent patients received surgical treatment more quickly than their nonrecurrent counterparts ([Table 4]).
Table 3
Hospital time versus imaging/no imaging
|
|
Imaging (CT or US) (n = 23)
|
No Imaging (only physical exam) (n = 25)
|
p-value
|
|
Mean Time (hours)
|
|
|
|
|
|
Length of ER Stay
|
7.58 ± 3.04
|
3.72 ± 2.34 *
|
0.002[a] (SS)
|
|
Time from ER to OR
|
33.60 ± 49.31
|
36.28 ± 66.17
|
0.051[b] (NS)
|
|
Time from clinic to OR
|
23.22
|
270.56 ± 309.30
|
0.35[a] (NS)
|
|
Post-Op Hospital Stay
|
61.02 ± 137.68
|
22.76 ± 46.01
|
0.36[b] (NS)
|
Abbreviations: NS, not statistically significant; SS, statistically significant.
* n = 11; remaining patients visited an outpatient clinic only.
a Wilcoxon rank sum exact test.
b Approximate Savage test.
Table 4
Hospital time vs recurrent/nonrecurrent groups
|
|
Recurrent Group (n = 11)
|
Non-Recurrent Group (n = 37)
|
p-value
|
|
Mean Time (hours)
|
|
|
|
|
|
Length of ER Stay
|
6.37 ± 3.07
|
6.32 ± 3.50 **
|
0.97[a] (NS)
|
|
Time from ER to OR
|
17.57 ± 12.09
|
40.84 ± 62.61
|
0.57[b] (NS)
|
|
Time from clinic to OR
|
681.52 ± 46.90
|
199.28 ± 277.75
|
0.088[a] (NS)
|
|
Post-Op Hospital Stay
|
36.95 ± 71.45
|
42.56 ± 110.15
|
0.91[b] (NS)
|
Abbreviation: NS, not statistically significant.
** n = 26; remaining patients visited an outpatient clinic only.
a Wilcoxon rank sum exact test.
b Approximate Savage test.
As per [Table 5], there was a statistically significant difference (p < 0.05) between recurrent and nonrecurrent patients with symptoms waiting to come in for primary evaluation. The recurrent group waited at home for ∼58.9 days until their first presentation, while the nonrecurrent group waited for 21.33 days ([Table 5], [Fig. 3]). Data was available for n = 34 patients; however, one patient was an outlier and was removed from this dataset due to their uncertainty of how long they waited before coming in for evaluation ([Fig. 3]).
Table 5
Days with symptoms until initial evaluation vs recurrent/nonrecurrent groups
|
|
Recurrent Group (n = 10)
|
Non-Recurrent Group (n = 23)
|
p-value
|
|
Length of Time Patient Felt Symptoms Before Initial Evaluation (days)
|
|
|
|
0.005[a] (SS)
|
|
Range of Time
|
2 - 180
|
1 - 21
|
|
|
Mean Time
|
58.90 ± 73.80
|
21.33 ± 73.42
|
|
|
Median Time
|
18.50 ± 101.50
|
5.00 ± 4.50
|
|
Abbreviation: SS, statistically significant.
a Approximate Savage test.
Fig. 3 Length of time patients waited at home after developing initial symptoms before seeking evaluation.
Of all 48 patients, 33% (16 of 48) had a seton placement during the initial incision and drainage procedure, two (13%) of whom developed a recurrent abscess. Of the 32 patients who did not receive a seton placement at the initial presentation, eight (25%) presented with a recurrent abscess.
Discussion
We analyzed data from 48 charts seen over four years at JSUMC and OUMC to evaluate factors that led to rectal abscess and recurrence after treatment. Data was collected on patient demographics, length of time from initial symptoms until seeking medical care, diagnostic information, and patient outcomes.
Our study identified a delay in patients seeking primary treatment resulted in an increased chance of recurrence. Potential factors contributing to this delay include experiencing partial or intermittent symptom relief from spontaneous drainage, the gradual progression of the infectious process, and hesitancy in seeking medical attention. In other studies, patients who waited to see a physician for a longer period were more likely to develop a recurrent abscess after primary treatment.[9]
[10] Delay in diagnosis and treatment may also lead to severe pain and complications such as fistulas, infection, and sepsis.[6]
Anorectal pain is the most common symptom of an anorectal abscess. When patients exhibit severe, ongoing anorectal discomfort without an obvious cause, physicians should remain vigilant for the possibility of an anorectal abscess. Patients with an anorectal abscess may present with anorectal pain, swelling, and redness of the anus. Obtaining a thorough history and physical examination, including an external perianal and digital rectal examination, can usually establish the diagnosis of perirectal abscess.[11] In our study, all recurrent patients had initially presented with anorectal discomfort or pain. Complaints of anorectal pain should serve as a primary indication of the presence of an abscess. Although this was not the case within our study, it is important to note that perirectal abscesses are often misdiagnosed as hemorrhoids.[9] If a physical examination fails to indicate its presence or if a complex abscess is suspected, further CT imaging should be performed.[12]
Once the diagnosis of a perirectal abscess is made, incision and drainage should take place as soon as possible. It is suggested that patients with a small, superficial abscess are more likely to undergo abscess drainage under local anesthesia in the ED.[9]
[11] For patients with a deep or more complicated abscess, it is advisable to seek surgical consultation for a thorough rectal exam under anesthesia, followed by incision and drainage in the operating room.[9]
[11]
Furthermore, patients scheduled for abscess drainage under local anesthesia should be evaluated for fistulas. As in our study, if a fistula was identified, surgical intervention such as primary fistulotomy,[11] seton placement,[13] or ligation of the intersphincteric fistula tract[14] is typically recommended. A seton is a thin silicone string that is inserted into the fistula tract, serving as the first line of therapy to prevent abscess and perianal sepsis.[13] Patients with Crohn's disease who develop fistulas are challenging because treatment of complex fistulas carries higher risks of recurrence and failure of or delayed healing.[4]
[13] The ligation of the intersphincteric fistula tract (LIFT) technique is also an alternative treatment of fistula-in-ano. This procedure involves the secure closure of the internal and external opening and removal of infected cryptoglandular tissue through an intersphincteric approach.[14] Selecting the appropriate surgical technique, based on specific pathological characteristics of the lesion, is crucial for effective treatment and minimizing the risk of recurrence.
In many of the cases of recurrence, a fistula was already present at the time of initial abscess drainage. Experts point out that less than half of patients experience recurrence, while only one-third progress to develop a fistula.[15]
[16] However, seeking timely evaluation, and prompt diagnosis, with subsequent treatment decreases the chances of worsening conditions and recurrence. Even after an abscess drainage, a fistula may form between the drainage site and anal crypt, which may then cause a recurrent abscess to develop. There is a high possibility that recurrent abscess formation is related to fistula-in-ano formation after abscess drainage.[10]
Diagnostic imaging is recommended when a deep anorectal abscess is suspected.[12] CT scans of the pelvis are frequently employed in acute scenarios to assess for anorectal abscesses. There has been no recent literature regarding the accuracy of modern CT technology for the detection of anorectal abscesses. The reported sensitivity for CT in detecting anorectal abscesses stands at 77%, as discussed by Levy et al.[17] The abscess found in one of our patients was not detected by a CT scan, but by a digital rectal examination. Endoanal ultrasounds are also used for establishing an initial diagnosis of perianal fistulae and abscesses. However, its practical factors such as patient discomfort restrict its initial use in evaluating suspected abscesses.[17] In our study, only three patients were initially diagnosed using ultrasound.
Similar to another retrospective study by Gnanadev et al.,[12] no differences in our study were found in the ultimate diagnosis of an anorectal abscess between patients who underwent imaging, and those who did not have imaging, even when variables such as age, sex, race, and other risk factors, including diabetes mellitus, hypertension, and Crohn's disease, were considered. In terms of clinical management, however, differences were noted for patients who received imaging and patients who did not. Like in our study, patients who received imaging spent less time waiting to receive surgical treatment compared with those who did not receive imaging and were diagnosed based on physical examination and history.
Additionally, obesity has been linked with gastrointestinal diseases. However, our study indicated that obesity did not affect abscess recurrence. No significant effects were observed for sex or age.
This study has several limitations, including the small sample size of patients with rectal abscesses, incomplete demographic information, incomplete chart information, and inconsistencies in performing and documenting diagnostic screening results.
Conclusion
Based on the results of our retrospective study, we conclude that patients with anorectal abscesses often postpone seeking medical attention. On average, patients who delayed evaluation were almost three times more likely to develop a recurrent abscess. Pain and discomfort in the anorectal area is a common symptom in those diagnosed with an anorectal abscess. Patients presenting with a suspected superficial anorectal abscess may still be successfully diagnosed using only clinical history and physical examination. Moreover, patients who had diagnostic imaging performed received surgery more quickly than patients who received only a physical examination. Most anorectal abscesses are localized in the perianal region and can be discerned via an external examination. A digital rectal examination may prove necessary to identify deep abscesses, which may then further require diagnostic imaging. Following diagnosis, prompt incision and drainage are the fundamental treatments for an anorectal abscess. Lastly, there is no correlation between abscess size and rate of recurrence. Overall, it is crucial for individuals experiencing pain in the anorectal area to promptly consult a doctor to rule out the possibility of an abscess, thereby reducing the risk of recurrence.
