Effectiveness of Treatment with Antibiotics Alone in Patients with Acute Diverticulitis and Pelvic Abscesses

Abstract

Introduction:

The available evidence regarding the treatment of acute diverticulitis (AD) with pelvic abscess using antibiotics alone is very limited. The objective of this study was to determine whether the short- and long-term outcomes of AD with pelvic abscesses treated exclusively with antibiotics are comparable to those of pericolic abscesses.

Methods:

A retrospective study was conducted on patients diagnosed with AD and either pelvic or pericolic abscesses, as confirmed by computed tomography, who were treated solely with antibiotic therapy between 2011 and 2021. Cases involving percutaneous drainage as part of conservative treatment were excluded.

Results:

Fifty-eight patients met the inclusion criteria, comprising 12 with pelvic abscesses and 46 with pericolic abscesses. Both groups exhibited similar baseline characteristics and radiological findings, except for a more frequent presence of free fluid in pelvic abscesses. The success rate of antibiotic therapy was 91.7% for pelvic abscess cases and 96.7% for pericolic cases (p = 0.508). No significant differences were observed in recurrence or elective surgery. In the subgroup of abscesses with a diameter ≥4 cm, the evolution was similar in both locations (treatment success rate of 87.5% in pelvic and 94.4% in pericolic; p = 0.529), although recurrence was slightly higher for pericolic abscesses (38.4% vs. 14.3%; p = 0.362).

Conclusions:

Antibiotic therapy alone proves to be effective and safe for pelvic abscesses, demonstrating a course similar to pericolic abscesses, even in the case of large abscesses. Although the analyzed patient cohort is small, this study provides additional evidence that percutaneous drainage is not always essential for treating this complication.

Introduction

Abscess formation in patients with acute diverticulitis (AD) occurs in 10–20% of cases.¹ The therapeutic approach to this complication can be surgical or medical, the latter based on antibiotic (AB) therapy with or without percutaneous drainage (PD). Most guidelines recommend treating only small abscesses with AB and adding percutaneous drainage in case of larger abscesses (3–5 cm) .^2,3 PD is an interventional procedure that is not always technically feasible, has a specific risk of morbidity, and, if it can be carried out, is associated with failure rates that range between 15% and 30%, being higher in patients with distant abscesses.⁴

Limited data exists regarding the efficacy of using AB alone to treat patients with large abscesses, and the existing studies suffer from a notable bias in patient selection as they only focus on individuals who are not susceptible to PD.^4,5

Conversely, the success rate of conservative treatment (AB with or without PD) is lower in Hinchey II AD compared with type IB.^1,6 However, Hinchey II AD encompasses a diverse range of distant abscesses, and it remains unclear if these poorer outcomes are specific to a particular subgroup.

In our center, we conduct PD of fluid collections by utilizing a transabdominal method. However, in cases of pelvic abscesses where loops hinder this approach, an alternative transgluteal access becomes necessary. Currently, our Interventional Radiology Service does not perform this type of access. This allows for the opportunity to examine the response of pelvic abscesses to initial AB treatment without utilizing PD, even when the abscess sizes exceed the recommended limits.

Our suggestion is that the management of patients with pelvic abscesses is comparable to that of pericolic abscesses, indicating that they can be treated similarly without requiring PD. Our main aim was to assess the efficacy of AB treatment in patients with AD and pelvic abscesses by comparing them to those with pericolic abscesses who underwent the same treatment. Additionally, we aimed to compare the progression of patients who were successfully managed conservatively in both the short and long term.

Materials and Methods

Study population

We conducted a retrospective review of all cases of AD in the left colon accompanied by an abscess between January 2011 and August 2021. The diagnosis of AD, size, and location of the abscess was determined by computed tomography (CT), and all patients had a follow-up of at least one year after discharge from the index episode. We used the modified Hinchey classification by Wasvary to assess the severity of the cases.⁷

Our study included patients who developed an abscess during the first episode of AD as well as those who experienced a recurrence after an initial uncomplicated episode. We only considered patients who received AB therapy as their first treatment option after at least 24 hours of medical therapy.

We excluded cases of AD with underlying colon neoplasia or abscesses not caused by diverticular pathology. We also did not study patients who underwent emergency surgery or received PD within the first 24 hours.

In our hospital, patients were managed according to a standardized protocol. Those who were hemodynamically stable were eligible for conservative treatment with hospital admission. This included an intravenous AB regimen and digestive rest. Commencing improved, enteral nourishment and altering the method of AB administration to oral were initiated until the 7–15-day cycle was concluded. In instances where a percutaneous approach was feasible, percutaneous drainage was recommended for abscesses larger than 4–5 cm, at the discretion of the interventional radiologist.

The study examined demographic information, medical history, Charlson comorbidity index (CCI), age-adjusted Charlson comorbidity index (ACCI), anesthesia risk based on the American Society of Anesthesiology (ASA), CT radiological findings, initial and secondary treatment, surgical procedure type, postoperative complications within the first 30 days, inpatient mortality, and recurrence of new episodes of AD in each patient group.

Medical records and digital imaging tests were reviewed to extract the data. Each case was assigned a number in compliance with data protection regulations. The Research Ethics Committee of the University Hospital of Badajoz approved the study.

Definitions of interest

Treatment success was defined as cases that exhibited favorable progression without relapse, the necessity for surgery, percutaneous drainage, or mortality within the initial 30 days. If an abscess recurred or the patient experienced a new episode of AD beyond the initial 30 days post-discharge, it was considered a new episode and thus categorized as a recurrence. To qualify as a new episode, radiological confirmation by CT was imperative.

The largest abscess diameter was measured in the axial or coronal plane of the CT scan, depending on its abdominal location. In instances of multiple abscesses, the measurement of the largest collection was chosen. All images underwent scrutiny by the investigating surgeons to identify any findings not documented in the radiological report.

A pericolic abscess was defined as one developing in the mesocolon or within 5 cm of the diverticulitis-affected area. Pelvic abscesses were categorized as those situated in a peritoneal recess within the lesser pelvis.

Narrow-spectrum AB therapy was considered when employing amoxicillin–clavulanate or the ciprofloxacin–metronidazole combination. Treatment was classified as broad spectrum if carbapenems or piperacillin–tazobactam were used.

Statistical analysis

Qualitative data were presented as absolute numbers and percentages, whereas quantitative data were reported as mean and standard deviation (SD) if the distribution was normal. For non-uniform distributions, median and range were used.

To test hypotheses related to categorical variables, the Chi-square test and Fisher exact test were employed. For quantitative variables, a comparison of means was conducted using the Student’s t-test, and the comparison of medians was performed using the Mann–Whitney U test. Statistical significance was established at p < 0.05.

Data were processed with SPSS 25.0 statistical software (Armonk, NY: IBM Corp.).

Results

During the study period, 77 patients (19.5%) presented with acute diverticulitis (AD) complicated by an abscess at some point in its course. The median age of these patients at the time of abscess development was 52 years (ranging from 30 to 88 y), with 45 being male and 32 female. Considering the type of abscess that initially developed, based on the modified Hinchey classification, 55 were classified as type IB (71.4%), and 22 were grade II (28.6%). Among the Hinchey II patients, the abscess location was pelvic in 13 cases, distant intra-abdominal in 5, and retroperitoneal in 4.

Baseline characteristics

Table 1 provides details and comparisons of demographic, clinical, and radiological characteristics associated with abscess in the study populations. Both groups appeared comparable in their baseline characteristics. Pelvic abscesses exhibited a slightly higher mean diameter compared with pericolic abscesses (4.34 cm vs. 3.5 cm), although this difference was not statistically significant. The proportion of abscesses greater than or equal to 4 cm also did not differ significantly. The only notable difference in radiological characteristics between the groups was a higher frequency of free fluid in collections located in the pelvis.

Table 1.

Baseline Characteristics

	Pericolic	Pelvic	Overall	P-value
	N = 46	N = 12	N = 58
	(%/SD)	(%/SD)	(%/SD)
Age	52.07 (11.70)	58.25 (15.54)	53.34 (12,69)	0.134
Sex: Male	28 (60.9)	7 (58.3)	35 (60.3)	1^a
Diabetes	2 (4.3)	0 (0)	2 (3.4)	1^a
Arterial hypertension	9 (1.6)	1 (8.3)	10 (17.2)	0.670^a
Smoking	18 (39.1)	6 (50)	24 (41.4)	0.527^a
Cardiophaty	6 (13)	0 (0)	6 (103)	0,328^a
Respiratory disease	7 (15.2)	2 (16.2)	9 (15.5)	1^a
Anesthesia risk
ASA 1–2	38 (76)	12 (100)	50 (87.2)	0.185^a
ASA 3–4	(17.4)	0 (0)	8 (13.8)
CCI
0	28 (60.9)	9 (75)	37 (63.8)	0.506^a
1–6	18 (39.1)	3 (25)	21 (36.2)
ACCI
0–2	38 (82.6)	9 (75)	47 (81)	0.681^a
3–9	8 (17.4)	3 (25)	11 (19)
Length of inflamed colon (cm)	7.74 (2.75)	7.88 (2.68)	7.77 (2.72)	0.878^b
Abscess diameter (cm)	3.5 (1.49)	4.34 (1.55)	3.68 (1.53)	0.091
Abscess ≥4 cm	18 (39.1)	8 (66.7)	26 (44.8)	0.088
Number of abscesses
Single	43 (93.5)	10 (83.3)	53 (91.4)	0.273
Multiple	3 (6.5)	2 (16.7)	5 (8.6)
Pneumoperitoneum	9 (19.6)	1 (8.3)	10 (17.2)	0.670
Free fluid	10 (21.7)	7 (58.3)	17 (29.3)	0.028^a
Fistula	4 (8.7)	1 (8.3)	5 (8.6)	1^a
Colon stenosis	2 (4.3)	1 (8.3)	3 (5.2)	0.508^a
Episode type
First episode	36 (78.3)	9 (75)	45 (77.6)
Recurrence	10 (21.7)	3 (25)	13 (22.4)	1^a

Fisher exact test.

Mann–Whitney U test.

SD, Standard deviation; ASA, Anesthesia risk on the basis of the American Society of Anesthesiology; CCI, Charlson comorbidity index; ACCI, Age-adjusted Charlson comorbidity index.

Treatment of pelvic abscesses

With the exception of one patient, all individuals with pelvic abscesses were managed with AB therapy without drainage (92.3%). The patient, for whom surgery was the initial treatment option, had a 5.5 cm abscess with no other indicators of poor clinical or radiological prognosis. The success rate of AB therapy reached 91.7% (Fig. 1). One patient required surgical intervention because of the clinical and analytical deterioration with signs of sepsis on the tenth day of admission. Fecaloid peritonitis was observed during surgery, and a Hartmann intervention was performed. During follow-up, four patients (36.4%) experienced recurrence, with two of them having a new episode of AD with abscess (50%). Four patients were scheduled for preventive sigmoidectomy (34.6%).

FIG. 1.

Clinical results of patients with pelvic abscess. AB, Antibiotics alone.

Treatment of pericolic abscesses

Of the 55 patients with pericolic abscesses, 6 underwent a surgical procedure, whereas 3 had percutaneous drainage (PD) performed within the initial 24-hour period. The reasons for surgery were pneumoperitoneum associated with the abscess in four cases, signs of intestinal obstruction in another case, and peritoneal irritation discovered during physical examination in the remaining case. The largest diameter of the abscess was greater among cases undergoing percutaneous drainage (7.3 cm; SD 1.7) compared with patients who underwent surgery as the initial treatment option (3.5 cm; SD 1.4).

The remaining 46 (83.6%) patients were initially managed with AB therapy, which was unsuccessful in two cases: one patient necessitated Hartmann surgery due to progression to purulent peritonitis, whereas another underwent PD following an increase in collection size (Fig. 2). PD was performed 16 days after the initiation of antibiotic therapy. Therefore, the success rate of the initial treatment with AB therapy in the group of patients with pericolic abscess was 96.7%. Of the 45 patients who survived the first episode without resection surgery, 13 (28.9%) experienced a new outbreak of the disease, with four of them developing a new abscess during follow-up (30.7% of recurrent cases). Nine patients (23.1%) underwent elective sigmoidectomy.

FIG. 2.

Clinical results of patients with pericolic abscess. AB, Antibiotics alone; PD, Percutaneous drainage.

Evolution of treatment by location and size

In total, 46 pericolic and 12 pelvic abscesses were initially treated with AB therapy without PD. The overall success rate of this approach was 94.8%, with only one patient experiencing failure in the pelvic group and two in the pericolic group. Although the AB success rate was slightly higher in the pericolic group (96.7% vs. 91.7%), it did not reach statistical significance.

Among 44.8% (26 patients), the size of the abscess was greater than or equal to 4 cm. In these cases, the success of conservative treatment was 92.3%. For patients with pelvic abscesses larger than 4 cm, the success of AB treatment was 87.5% (7 out of 8 patients), and in the pericolic abscess group with this size, it was 94.4% (17 out of 18) (p = 0.529).

Table 2 provides a detailed comparative analysis of the type of AB used, evolution during hospital admission, and long-term outcomes.

Table 2.

Short- and Long-Term Evolution

	Pericolic	Pelvic	Overall
	N = 46	N = 12	N = 58
	(%/range)	(%/range)	(%/range)	P-value
Antibiotic
Narrow-spectrum	15 (32.6)	1 (8.3)	16 (27.6)	0.149
Broad-spectrum	31 (67.4)	11 (91.7)	42 (72.4)
Treatment failure	2 (4.3)	1 (8.3)	3 (5.2)	0.508
Postoperative morbidity	0 (0)	1 (100)	1 (50)	1^a
Mortality	0 (0)	0 (0)	0 (0)	—
Length of hospital stay (days)	8 (3–25)	10 (7–25)	8 (3–25)	0.083^b
Recurrence	13 (28.9)	4 (36.4)	17 (30.4)	0.719^a
Elective sigmoidectomy	9 (23.1)	4 (36.4)	13 (22.4)	0.370
Definitive stoma	2 (4.3)	0 (0)	2 (3.4)	0.300^a

Fisher exact test.

Mann–Whitney U test.

Seventeen patients (30.4%) experienced a new episode. Recurrence rates were similar between the study groups during a comparable follow-up period: 60 months (SD: 36 mo) for the pericolic group and 49 months (SD: 26 mo) for the pelvic group (p = 0.09). No differences were observed in morbidity and mortality, hospital stay, rate of elective surgery, or definitive stomas.

Discussion

Despite being classified as a more complicated condition according to the modified Hinchey classification, pelvic abscesses follow a similar course of progression to pericolic abscesses after AB treatment, with comparable rates of failure and recurrence.

In our study, conservative treatment for pelvic abscesses had a success rate of 91.7%, whereas pericolic abscesses had a success rate of 96.7%. We compared both groups and found no differences in their baseline characteristics. The radiological findings were also similar, except that pelvic abscesses tended to have a slightly larger abscess diameter and a higher frequency of associated free fluid. These factors have been linked to a poorer prognosis in the conservative management of AD with abscesses^1,6,8 but despite these unfavorable findings, the evolution of pelvic abscesses was not worse. Some studies have suggested that conservative management is less successful for AD patients with distant abscesses compared with pericolic abscesses.

Several authors have noted that the failure rate of conservative management appears to be higher in patients with AD who have distant abscesses compared with those with pericolic abscesses. Ambrosetti analyzed the failure rate of conservative treatment (AB and PD) on the basis of the type of abscess, reporting a failure rate of 39% in patients with pelvic abscesses compared with 15% in patients with mesocolic abscesses.⁹ However, the study did not analyze the outcomes of patients who underwent drainage versus those treated specifically with AB therapy.

Lee’s systematic review revealed that pelvic collections have a higher risk of conservative management failure compared with pericolic abscesses.¹ Nevertheless, both patients treated with AB and drainage and those treated with AB alone were considered part of the conservative treatment. In contrast, a recent multicenter study found a higher need for surgical intervention in non-pericolic locations (27.5% in patients with Hinchey II AD and 9.3% for type IB).⁶ The study distinguished between AB and PD within conservative treatment but did not compare the success of each treatment based on the specific location of the abscess. Our research showed a lower failure rate for ABS in conservative treatment compared with the literature: 8.3% in patients with pelvic abscesses and 4.3% in patients with pericolic abscesses, without statistically significant differences between the two groups. We opted to separately analyze pelvic abscesses and exclude the remaining cases of Hinchey II because of a more aggressive initial presentation observed in our series. Although this decision reduces the overall number of patients, it enhances the homogeneity of the sample. Currently, there are no studies determining the success of conservative treatment for remote retroperitoneal and intra-abdominal abscesses. However, their occurrence is much less frequent, making it challenging to draw definitive conclusions.

The AB treatment is firmly established for abscesses smaller than 3 cm; however, for larger abscesses, current guidelines recommend PD.^2,3 These recommendations are grounded in the observation that abscesses larger than 4 cm exhibit a less favorable outcome with medical treatment.¹⁰ Limited published patient series analyze the efficacy of conservative treatment with AB alone in patients with AD. Elagili et al. selectively studied abscesses larger than 3 cm.⁵ Among 164 patients with an abscess surpassing this size, 32 received AB therapy alone, whereas the remainder underwent PD. Despite the AB group having a smaller mean abscess diameter (5.9 cm for the AB-only group vs. 7.1 cm for the drainage group), no differences in the percentage of therapeutic failure, defined as the necessity for urgent surgery, were observed between the two groups (25% for the AB-only group vs. 18% for drainage). This study is subject to a significant selection bias as it includes in the AB treatment group only those cases ineligible for PD because of technical infeasibility or medical decision. Furthermore, long-term data for successfully treated patients, who did not ultimately require urgent surgery and were scheduled for elective surgery, remains unknown. Comparable results were identified in abscesses larger than 3 cm in AD Hinchey II, with even greater success in the group undergoing AB therapy without percutaneous drainage, although statistical significance was not surpassed (19% in the no-drainage group vs. 33% in the drainage group).⁴ Once again, the results are confined by a larger median diameter in the PD group.

The omission of transgluteal drainage in our center facilitated the study of the evolution of major abscesses treated with AB, eliminating the confounding bias between PD and abscess diameter, a limitation prevalent in most studies. Similarly, the initial management with PD in the pericolonic abscess group was exceptional, enhancing the similarity of pelvic abscesses with the control group.

A Finnish study thoroughly investigated both methods of treating abscesses and found that as the size of the abscess increased, the likelihood of treatment failure also increased for all groups. No discernible differences in outcomes were detected for abscesses ≥4 cm treated with AB (failure rate of 27%) compared with those treated with PD (35%).¹¹ Once again, a higher failure rate was noted, specifically for large abscesses with AB, exceeding that of our cohort (7.7%). The lower failure rate observed may be attributed to the size of the abscesses in our series, none of which exceeded a maximum value of 8 cm. Our study offered a distinct advantage compared with the previously mentioned research. We had the opportunity to precisely identify the location of the abscess and its impact on the failure rate. Our findings demonstrate that for abscesses larger than 4 cm, the failure rate with AB management was 5.6% for pericolic abscesses and 12.5% for pelvic abscesses. Although pelvic abscesses showed worse outcomes, the difference with pericolic abscesses did not reach statistical significance.

Notwithstanding the unequivocal recommendations favoring PD, instances arise where this procedure is not technically feasible, primarily because of loop interposition, and is associated with its own morbidity (combined average of 2.5%). Achieving puncture may necessitate catheter replacement in 15.5% of cases or result in unresolved infection in 23% of patients.^12,13 Consequently, treatment with ABS emerges as a viable alternative in cases where drainage cannot be performed or is unavailable.

Our recurrence rate was 28.9% in patients with pericolic abscess and 36.4% in patients with pelvic abscesses, the majority presenting with uncomplicated AD. Notably, treatment without drainage did not worsen long-term results, aligning with outcomes described in the literature for abscesses.^10,13,14 During follow-up, elective surgery was undertaken in 23.1% of patients with pericolic abscess and 36.4% of patients with pelvic abscess. The primary indication for elective surgery was the history of abscess and the presence of colovesical fistula. Recommendations regarding elective surgery after abscess development lack specificity and should be considered on a case-by-case basis; however, more than a third of patients undergo colon resection after overcoming the episode complicated by abscess with conservative treatment.¹⁵

To the best of our knowledge, this is the inaugural article to specifically scrutinize the efficacy of conservative AB treatment in distinct subgroups of patients with AD. We posit that patients with pelvic abscesses may progress similarly to those with pericolic abscesses, given their proximity to the initial perforation, and their clinical presentation might be less severe than other Hinchey II AD subtypes.

The retrospective nature of our study presents inherent limitations that should be acknowledged. Additionally, the relatively small number of patients studied should be taken into account, despite the infrequent occurrence of abscesses. Because of the low incidence of adverse events, we were unable to identify risk factors related to the failure of conservative treatment during the progression of the condition. To achieve sufficient statistical power, a multicenter design would be necessary and compelling.

Our findings contribute new evidence to the latest recommendations of scientific societies regarding the conservative management of AD with abscess. They affirm the safety of non-surgical treatment based on AB for this type of complication, even in cases of larger and pelvic abscesses. This treatment option is dependent on the patient’s clinical condition and requires close monitoring. Surgical intervention is proposed if the patient’s physical condition deteriorates or if the infectious condition does not resolve.

Conclusion

Using AB as initial management for patients with AD and pelvic abscesses is a secure option that has a high success rate. Furthermore, it does not increase the incidence of recurrences, elective surgery, or the possibility of a permanent stoma compared with patients with pericolonic abscesses. The findings of this study, although based on a small sample size, offer valuable insights that can be applied in routine medical practice for patients with pelvic abscesses caused by AD. This is particularly helpful in cases where DP is not an option.

Footnotes

Authors’ Contributions

María Carmona Agúndez: This author collected the data, did the statistical analysis and wrote the article. Isabel María Gallarín Salamanca: This author wrote and reviewed the article. Jesús Salas Martínez: This author reviewed the article.

Author Disclosure Statement

No conflicts of interest exist.

Funding Information

No specific grants have been obtained for this research from public sector agencies, commercial entities, or non-profit organizations.

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