Original article
Multicentre study of non-surgical management of diverticulitis
with abscess formation
D. P. V. Lambrichts1,4 , H. E. Bolkenstein6 , D. C. H. E. van der Does1 , D. Dieleman1 ,
R. M. P. H. Crolla7 , J. W. T. Dekker8 , P. van Duijvendijk9 , M. F. Gerhards5 , S. W. Nienhuijs10 ,
A. G. Menon2,3 , E. J. R. de Graaf3 , E. C. J. Consten6 , W. A. Draaisma11 , I. A. M. J. Broeders6 ,
W. A. Bemelman4 and J. F. Lange1,2,3
1
Departments of Surgery, Erasmus Medical Centre, 2 Havenziekenhuis and 3 IJsselland Hospital, Rotterdam, 4 Academic Medical Centre and 5 Onze Lieve
Vrouwe Gasthuis, Amsterdam, 6 Meander Medical Centre, Amersfoort, 7 Amphia Hospital, Breda, 8 Reinier de Graaf Gasthuis, Delft, 9 Gelre Hospitals,
Apeldoorn, 10 Catharina Hospital, Eindhoven, and 11 Jeroen Bosch Hospital, ‘s-Hertogenbosch, the Netherlands
Correspondence to: Mr D. P. V. Lambrichts, Room Ee-173, Department of Surgery, Erasmus Medical Centre, PO Box 2040, 3000 CA Rotterdam, the
Netherlands (e-mail: d.lambrichts@erasmusmc.nl;
@dplambr)
Background: Treatment strategies for diverticulitis with abscess formation have shifted from (emer-
gency) surgical treatment to non-surgical management (antibiotics with or without percutaneous
drainage (PCD)). The aim was to assess outcomes of non-surgical treatment and to identify risk factors
for adverse outcomes.
Methods: Patients with a first episode of CT-diagnosed diverticular abscess (modified Hinchey Ib or II)
between January 2008 and January 2015 were included retrospectively, if initially treated non-surgically.
Baseline characteristics, short-term (within 30 days) and long-term treatment outcomes were recorded.
Treatment failure was a composite outcome of complications (perforation, colonic obstruction and fistula
formation), readmissions, persistent diverticulitis, emergency surgery, death, or need for PCD in the
no-PCD group. Regression analyses were used to analyse risk factors for treatment failure, recurrences
and surgery.
Results: Overall, 447 patients from ten hospitals were included (Hinchey Ib 215; Hinchey II 232), with a
median follow-up of 72 (i.q.r. 55–93) months. Most patients were treated without PCD (332 of 447,
74⋅3 per cent). Univariable analyses, stratified by Hinchey grade, showed no differences between no PCD
and PCD in short-term treatment failure (Hinchey I: 22⋅3 versus 33 per cent, P = 0⋅359; Hinchey II: 25⋅9
versus 36 per cent, P = 0⋅149) or emergency surgery (Hinchey I: 5⋅1 versus 6 per cent, P = 0⋅693; Hinchey
II: 10⋅4 versus 15 per cent, P = 0⋅117), but significantly more complications were found in patients with
Hinchey II disease undergoing PCD (12 versus 3⋅7 per cent; P = 0⋅032). Multivariable analyses showed that
treatment strategy (PCD versus no PCD) was not independently associated with short-term treatment
failure (odds ratio (OR) 1⋅47, 95 per cent c.i. 0⋅81 to 2⋅68), emergency surgery (OR 1⋅29, 0⋅56 to 2⋅99) or
long-term surgery (hazard ratio 1⋅08, 95 per cent c.i. 0⋅69 to 1⋅69). Abscesses of at least 3 cm in diameter
were associated with short-term treatment failure (OR 2⋅05, 1⋅09 to 3⋅86), and abscesses of 5 cm or larger
with the need for surgery during short-term follow-up (OR 2⋅96, 1⋅03 to 8⋅13).
Conclusion: The choice between PCD with antibiotics or antibiotics alone as initial non-surgical
treatment of Hinchey Ib and II diverticulitis does not seem to influence outcomes.
Presented to a meeting of the Dutch Surgical Society, Veldhoven, the Netherlands, May 2015
Paper accepted 10 January 2019
Published online in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.11129
Introduction
Diverticulosis is common in the Western world and is
estimated to affect more than half of the population
over the age of 65 years1 . Diverticulosis might lead to
diverticulitis in approximately 4⋅3–7 per cent of patients2,3 ,
of which 25 per cent present with acute complicated diverticulitis; this can consist of severe complications, such as
abscess, perforation, stenosis or fistula4 . Abscess formation
occurs in approximately 15 per cent of patients with acute
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BJS 2019; 106: 458–466
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in
any medium, provided the original work is properly cited and is not used for commercial purposes.
Non-surgical management of diverticulitis with abscess formation
complicated diverticulitis5 – 7 . It can be classified according
to the modified Hinchey classification as type Ib (confined
pericolic abscess smaller than 5 cm) or Hinchey II (pelvic,
distant intra-abdominal or retroperitoneal abscess at least
5 cm in size)8,9 .
Over the years, treatment strategies for diverticulitis with
abscess formation have gradually shifted from (emergency)
surgical treatment to non-surgical management comprising antibiotics with or without percutaneous drainage
(PCD)10 . Currently, guidelines11 – 13 advise that small
pericolic abscesses can be treated with antibiotics, whereas
distant (pelvic) or larger abscesses, usually defined as those
with a diameter of 3–5 cm or larger, should be treated with
PCD, if possible. As patients undergoing non-surgical
treatment are at risk of adverse outcomes such as emergency surgery, disease recurrence, readmission and even
death (both in the short and long term)10,14 , adequate
patient selection for the optimal choice of treatment has
come to play an important role in the management of
these patients.
However, the clinical course of complicated diverticulitis
with abscess formation after non-surgical treatment, as well
as the risk factors for adverse outcomes, have not been
analysed adequately10,12 . Most of the existing studies15 – 22
addressing these topics are limited by a short follow-up,
small and single-institution study populations and a lack of
time-to-event analysis.
Therefore, the primary aim of this multicentre retrospective study was to assess both the short- and long-term outcomes of initial non-surgical treatment strategies for acute
complicated diverticulitis with abscess formation (Hinchey
Ib and II) in a large number of patients. The second aim was
to identify risk factors associated with adverse outcomes,
to help facilitate adequate patient selection and assess the
optimal treatment strategy.
Methods
This multicentre retrospective study was conducted in two
academic and eight teaching hospitals in the Netherlands.
The study was approved by the institutional review boards
of all participating hospitals. This article was written
in accordance with the STROBE statement and checklist23 .
All patients aged 18 years and older, who had a first
episode of CT-diagnosed complicated diverticulitis with
abscess formation (modified Hinchey Ib or II8 ), and who
had initial non-surgical treatment, being either antibiotic
treatment (no PCD) or antibiotic treatment with PCD,
were eligible for inclusion in the cohort. Patients with
perforated diverticulitis with peritonitis (Hinchey III or
IV) and those with signs of sepsis or concurrent fistula
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
459
formation were excluded. Potentially eligible patients who
presented between 1 January 2008 and 31 January 2015
were sought by using a diagnosis-specific code (Diagnose
Behandeling Combinatie or Diagnosis Related Group),
ICD-9 or ICD-10 codes in all hospital databases. In Gelre
Hospital, patients could only be identified between 1 January 2012 and 31 January 2015. Subsequently, patients’
medical records were screened for inclusion and exclusion
criteria before definitive inclusion in the study cohort.
Data collection
All medical records were reviewed retrospectively. Baseline patient characteristics were collected, such as age,
BMI, co-morbidities, medical and surgical history, previous episodes of uncomplicated diverticulitis, medication,
smoking, alcohol consumption and ASA fitness grades.
Radiological details of the number, location and size
of abscesses were recorded, as well as clinical signs
and symptoms (nausea, vomiting, bowel complaints, rectal blood loss), and laboratory parameters (C-reactive
protein (CRP) and white blood cell count (WBC)). The
largest reported size of the abscess was used as the measure of abscess size. Details of treatment were recorded,
including type and duration of antibiotic treatment, PCD
(approach, type of drain and duration of drainage) and surgical procedures (for example, elective or emergency
resection or stoma reversal surgery).
Outcomes
Short-term outcomes were: treatment failure, complications (colonic obstruction, perforation and fistula
formation), clinical deterioration/progression of disease,
emergency surgery (all unscheduled operations), readmissions, persistent diverticulitis (complaints lasting more
than 30 days) and death. Long-term outcomes were:
recurrent (un)complicated diverticulitis episodes, sigmoid
resection and death. Short term was defined as the first
30 days after diagnosis of abscess, or during the primary
admission if a patient was still in hospital after 30 days,
whereas long term was defined as the period thereafter.
Treatment failure was defined as the composite outcome
of complications, readmissions, persistent diverticulitis,
emergency surgery, death or need for PCD in the no-PCD
group. Recurrent diverticulitis was registered as complicated in the presence of a phlegmon, abscess, fistula,
stenosis or perforation, whereas uncomplicated diverticulitis was registered if it was mentioned in the medical record
as recurrent disease, in the absence of the abovementioned
complications.
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BJS 2019; 106: 458–466
460
D. P. V. Lambrichts, H. E. Bolkenstein, D. C. H. E. van der Does, D. Dieleman, R. M. P. H. Crolla, J. W. T. Dekker et al.
Statistical analysis
Results
Multiple imputation techniques were used to impute missing data to avoid selection bias. Data were assumed to be
missing at random. All reported results are based on the
imputed data, where the estimates of interests at the final
computational step were combined across the imputed data
sets using Rubin’s rules24 . Continuous variables are presented as mean(s.d.) or median (i.q.r.), depending on the
normality of data distribution, and compared using the
independent t test or Mann–Whitney U test, as appropriate. Categorical variables are presented as numbers with
percentages, and were analysed using Pearson’s χ2 test and
Fisher’s exact test.
Differences in patient and disease characteristics between
patients with and without treatment failure and emergency
surgery were assessed to identify risk factors for these
outcomes. Univariable logistic regression analyses were
used to calculate crude odds ratios (ORs) with 95 per
cent confidence intervals. Inclusion of relevant diagnostic
items in the multivariable model, to identify independent
predictors, was based on clinical knowledge and P values
(P < 0⋅200 or P < 0⋅050, depending on the event rate).
Recurrence and sigmoid resection in the long term were
assessed by means of Kaplan–Meier estimates, stratified by Hinchey classification and treatment (no PCD
versus PCD), with censoring at the end of study follow-up
or death. The effect of Hinchey classification and treatment on the outcome was assessed by means of the
Mantel–Cox log rank test. Cox proportional hazards
regression was used to analyse risk factors for recurrence and sigmoid resection in the long term. Hazard
ratios (HRs) with 95 per cent confidence intervals are
presented for co-variables associated with recurrence or
sigmoid resection during long-term follow-up. Differences
between hospitals could have an effect on treatment outcomes; to test for this bias by clustering of data, the shortand long-term analyses were also adjusted for hospital.
Short-term outcomes were adjusted by fitting a generalized linear mixed model for each outcome, using a logistic
regression mixed model. Hinchey classification and PCD
were entered separately as fixed effects and hospital as a
random effect. For the short-term multivariable logistic
regression analyses, hospital was entered as a co-variable
in each multivariable model. Long-term Cox regression
analyses were adjusted by entering hospital as a co-variable
in each multivariable model. Finally, sensitivity analyses of
the non-imputed data set were undertaken to test whether
the imputation technique had any influence on the outcomes of interest. All analyses were done using SPSS®
version 24.0 (IBM, Armonk, New York, USA).
Patient and disease characteristics are shown in Table 1.
A total of 447 patients with CT-proven Hinchey type
Ib (215 patients) or II (232) diverticulitis were included.
The Academic Medical Centre contributed 20 patients
(4⋅5 per cent), Erasmus University Medical Centre 11 (2⋅5
per cent), Meander Medical Centre 69 (15⋅4 per cent),
Havenziekenhuis 4 (0⋅9 per cent), IJsselland Hospital 24
(5⋅4 per cent), Amphia Hospital 84 (18⋅8 per cent), Reinier
de Graaf Gasthuis 32 (7⋅2 per cent), Onze Lieve Vrouwe
Gasthuis 99 (22⋅1 per cent), Gelre Hospital 51 (11⋅4 per
cent) and Catharina Hospital 53 (11⋅9 per cent).
The mean(s.d.) age of the patients was 61(13) years and
40⋅7 per cent were men. The mean BMI of the total cohort
was 27⋅8(5⋅7) kg/m2 . Some 271 patients (60⋅6 per cent) had
co-morbidities and 123 (27⋅5 per cent) had an ASA fitness
grade above II. The mean CRP level was 168(106) mg/l for
the total cohort and mean WBC was 14⋅8(5⋅2) × 109 /l.
Most patients were treated with amoxicillin–clavulanic
acid (90 of 289, 31⋅1 per cent), cefuroxime and metronidazole (88 of 289, 30⋅4 per cent), ceftriaxone and metronidazole (41 of 289, 14⋅2 per cent), or other antibiotics (70
of 289, 24⋅2 per cent) such as clindamycin, co-trimoxazole
or piperacillin tazobactam; median duration of antibiotic
treatment was 7 (i.q.r. 5–12) days. Information on route
of antibiotic administration was available for 174 of 332
patients in the no-PCD group and 67 of 115 in the PCD
group; 36 (20⋅6 per cent) and six (9 per cent) patients
respectively received oral antibiotics. Most patients (332,
74⋅3 per cent) were initially treated without PCD; the
remaining 115 patients (26⋅7 per cent) underwent PCD
for a median of 6 (3–16) days. The PCD approach was
mainly transabdominal (86 of 115, 74⋅8 per cent), guided
by either ultrasound imaging (49 of 115, 42⋅6 per cent) or
CT (63 of 115, 54⋅8 per cent). Median duration of hospital stay was 7 (5–13) days and median follow-up was 72
(55–93) months.
Levels of inflammatory parameters were higher in the
PCD group, with a mean CRP concentration of 222(114)
mg/l compared with 149(96) mg/l in the no-PCD group,
and mean WBC of 16⋅3(5⋅6) versus 14⋅3(4⋅9) × 109 /l respectively. A larger proportion of patients in the PCD group
were classified as having Hinchey II disease (84⋅3 versus
40⋅7 per cent), and with multiple abscesses (20⋅0 versus 12⋅0
per cent). Of 63 patients with multiple abscesses, four were
known to use corticosteroids, one to use mycophenolic
acid, and one patient had undergone renal transplantation,
whereas none of these patients received chemotherapy
around the time of presentation. Median abscess diameter
was 6⋅4 (5⋅0–8⋅5) cm in the PCD group compared with 3⋅6
(2⋅5–5⋅1) cm in the group treated without PCD. Median
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
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BJS 2019; 106: 458–466
Non-surgical management of diverticulitis with abscess formation
Table 1
461
Baseline characteristics
Patient demographics
Age (years)*
Sex ratio (M : F)
BMI (kg/m2 )*
Smoking
Alcohol consumption
Co-morbidities
ASA fitness grade > II
Patients with registered co-morbidity
Medical history
History of diverticulitis
History of abdominal surgery
Medication
NSAIDs
Steroids
Clinical symptoms
Duration of symptoms (days)†
Nausea
Vomiting
Diffuse abdominal pain
Change in bowel habit
Rectal blood loss
Clinical signs
Rebound tenderness
Local muscular guarding/resistance
Diffuse muscular guarding
Temperature (∘ C)*
Laboratory parameters*
C-reactive protein (mg/l)
White blood cell count (× 109 /l)
Radiological parameters
Hinchey II‡
Largest abscess diameter (cm)†
Distant location of abscess
No. of patients with multiple abscesses
Free peridiverticular air
Free air in abdomen
Free fluid
Duration of hospital stay (days)†
Total cohort
(n = 447)
No PCD
(n = 332)
PCD
(n = 115)
61 (13)
182 : 265
27⋅8 (5⋅7)
228 (51⋅0)
232 (51⋅9)
60 (13)
139 : 193
27⋅6 (5⋅5)
167 (50⋅3)
178 (53⋅6)
63 (13)
43 : 72
28⋅4 (6⋅3)
61 (53⋅0)
54 (47⋅0)
0⋅140¶
0⋅400
0⋅404¶
0⋅603
0⋅274
123 (27⋅5)
271 (60⋅6)
84 (25⋅3)
201 (60⋅5)
39 (33⋅9)
70 (60⋅9)
0⋅075
0⋅952
137 (30⋅6)
151 (33⋅8)
93 (28⋅0)
119 (35⋅8)
44 (38⋅3)
32 (27⋅8)
0⋅035
0⋅130
182 (40⋅7)
43 (9⋅4)
133 (40⋅1)
35 (10⋅5)
49 (42⋅6)
8 (7⋅0)
0⋅573
0⋅239
7 (3–14)
236 (52⋅8)
108 (24⋅2)
61 (13⋅6)
294 (65⋅8)
70 (15⋅7)
7 (3–12)
163 (49⋅1)
65 (19⋅6)
44 (13⋅3)
221 (66⋅6)
44 (13⋅3)
8 (4–14)
73 (63⋅5)
43 (37⋅4)
16 (13⋅9)
73 (63⋅5)
26 (22⋅6)
0⋅062#
0⋅018
0⋅001
0⋅704**
0⋅548
0⋅044
141 (31⋅5)
115 (25⋅7)
50 (11⋅2)
37⋅7 (0⋅9)
104 (31⋅3)
81 (24⋅4)
32 (9⋅6)
37⋅7 (0⋅9)
37 (32⋅1)
34 (29⋅6)
18 (15⋅7)
37⋅8 (1⋅0)
0⋅602
0⋅259
0⋅255**
0⋅319¶
168 (106)
14⋅8 (5⋅2)
149 (96)
14⋅3 (4⋅9)
222 (114)
16⋅3 (5⋅6)
< 0⋅001¶
0⋅001¶
232 (51⋅9)
4⋅2 (2⋅7–6⋅1)
106 (23⋅7)
63 (14⋅1)
143 (32⋅0)
56 (12⋅5)
90 (20⋅1)
7 (5–13)
135 (40⋅7)
3⋅6 (2⋅5–5⋅1)
71 (21⋅4)
40 (12⋅0)
106 (31⋅9)
36 (10⋅8)
61 (18⋅4)
7 (4–10)
97 (84⋅3)
6⋅4 (5⋅0–8⋅5)
35 (30⋅4)
23 (20⋅0)
37 (32⋅2)
20 (17⋅4)
29 (25⋅2)
10 (7–18)
< 0⋅001
< 0⋅001#
0⋅046
0⋅035
0⋅925
0⋅252
0⋅187
< 0⋅001#
P§
Values in parentheses are percentages, unless indicated otherwise; values are *mean(s.d.) and †median (i.q.r.). ‡Abscess 5 cm or larger in diameter and/or
distant abscess. PCD, percutaneous drainage; NSAID, non-steroidal anti-inflammatory drug; §Pearson χ2 test, except ¶independent t test,
#Mann–Whitney U test and **Fisher’s exact test.
duration of hospital stay was longer in the PCD group: 10
(7–18) versus 7 (4–10) days.
Missing data
All candidate predictors had missing data, except age,
sex and ASA classification. Most variables had between 1
and 20 per cent missing data. Three variables had a large
amount of missing data: BMI (47⋅9 per cent), smoking (60⋅6
per cent) and alcohol consumption (64⋅2 per cent). For
abscess size, 31⋅5 per cent of data were missing. In total,
2140 data items (14⋅9 per cent) were imputed.
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
Short- and long-term outcomes
Short-and long-term outcomes are summarized in Table 2.
Of the total cohort, 120 patients (26⋅8 per cent) experienced treatment failure and 40 (8⋅9 per cent) required
emergency surgery within 30 days after first presentation.
One patient had operative drainage and a stoma was constructed in three patients, two of whom also underwent
sigmoid resection in a second stage. Seventy-one patients
(15⋅9 per cent) were readmitted to hospital within 30 days
after first presentation and 63 (14⋅1 per cent) had persistent diverticulitis. Overall, 16 patients in the no-PCD
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462
Table 2
D. P. V. Lambrichts, H. E. Bolkenstein, D. C. H. E. van der Does, D. Dieleman, R. M. P. H. Crolla, J. W. T. Dekker et al.
Short- and long-term outcomes
Total cohort (n = 447)
Short-term outcomes
Treatment failure
Complications†
Clinical deterioration/
disease progression
Readmission
Persistent diverticulitis
Emergency surgery
(sigmoid resection)
Death
Long-term outcomes
Complications†
Overall recurrence
Sigmoid resection
Death
Hinchey Ib (n = 215)
Hinchey II* (n = 232)
Total
(n = 447)
No PCD
(n = 332)
PCD
(n = 115)
P‡
No PCD
(n = 197)
PCD
(n = 18)
P
No PCD
(n = 135)
PCD
(n = 97)
P‡
120 (26⋅8)
25 (5⋅6)
95 (21⋅3)
79 (23⋅8)
13 (3⋅9)
59 (17⋅8)
41 (35⋅7)
12 (10⋅4)
36 (31⋅3)
0⋅013
0⋅009
0⋅002
44 (22⋅3)
8 (4⋅2)
30 (15⋅2)
6 (33)
0 (0)
6 (33)
0⋅359§
0⋅908§
0⋅091§
35 (25⋅9)
5 (3⋅7)
29 (21⋅5)
35 (36)
12 (12)
30 (31)
0⋅149
0⋅032§
0⋅147
71 (15⋅9)
63 (14⋅1)
40 (8⋅9)
49 (14⋅8)
42 (12⋅7)
24 (7⋅2)
22 (19⋅1)
21 (18⋅3)
16 (13⋅9)
0⋅253
0⋅130
0⋅030
27 (13⋅7)
23 (11⋅7)
10 (5⋅1)
5 (28)
5 (28)
1 (6)
0⋅178§
0⋅100§
0⋅693§
22 (16⋅3)
19 (14⋅1)
14 (10⋅4)
17 (18)
16 (16)
15 (15)
0⋅714
0⋅583
0⋅117
5 (1⋅1)
3 (0⋅9)
2 (1⋅7)
0⋅607§
3 (1⋅5)
0 (0)
1⋅000§
0 (0)
2 (2)
0⋅332§
74 (16⋅6)
122 (27⋅3)
124 (27⋅7)
28 (6⋅3)
46 (13⋅9)
93 (28⋅0)
87 (26⋅2)
16 (4⋅8)
28 (24⋅3)
29 (25⋅2)
37 (32⋅2)
12 (10⋅4)
0⋅009§
0⋅474¶
0⋅07¶
0⋅048¶
25 (12⋅7)
54 (27⋅4)
57 (28⋅9)
8 (4⋅1)
7 (39)
7 (39)
6 (33)
2 (11)
0⋅016§
0⋅623¶
0⋅474¶
0⋅263¶
21 (15⋅6)
39 (28⋅9)
30 (22⋅2)
8 (5⋅9)
21 (22)
22 (23)
31 (32)
10 (10)
0⋅245
0⋅349¶
0⋅046¶
0⋅270¶
Values in parentheses are percentages. *Abscess 5 cm or larger in diameter and/or distant abscess. †Colonic obstruction/ileus, fistula or perforation. PCD,
percutaneous drainage. ‡Pearson χ2 test, except §Fisher’s exact test and ¶Mantel–Cox log rank test.
group (4⋅8 per cent) underwent PCD during short-term
follow-up and two in the PCD group (1⋅7 per cent) had
a second PCD procedure. Five patients (1⋅1 per cent)
died from severe sepsis caused by perforated diverticulitis.
Three of these patients died after undergoing emergency
surgery, whereas two did not have surgery or receive further treatment owing to co-morbidity. In all, 122 patients
(27⋅3 per cent) experienced one or more episodes of
recurrent diverticulitis. In total, 166 episodes of recurrent diverticulitis were recorded, of which 94 (56⋅6 per
cent) were uncomplicated and 72 (43⋅4 per cent) were
complicated. Median time to recurrence was 8 (3–24)
months. Eighteen patients (14⋅8 per cent) had a first
recurrence within 1 month after the end of short-term
follow-up.
During long-term follow-up, 13 patients (2⋅9 per cent)
underwent PCD, seven in the no-PCD and six in the PCD
group. A total of 124 patients (27⋅7 per cent) required sigmoid resection, 14 in an emergency setting. Median time
to operation was 5 (3–13) months. Twenty-eight patients
died (6⋅3 per cent) during long-term follow-up, two from
diverticulitis-related causes. One of these patients died
from severe sepsis caused by anastomotic leakage after
Hartmann reversal surgery, and one from severe sepsis
owing to intestinal ischaemia after sigmoid resection for
diverticular stenosis. Overall, data on colonic evaluation
was available for 394 patients, of whom 239 (PCD 58,
no PCD 181) underwent colonoscopy during follow-up
after a median of 10⋅9 (7⋅0–21⋅6) weeks. A malignancy
was found in 12 of these patients, including nine in the
no-PCD group (P = 1⋅000).
During short-term follow-up, patients in the PCD group
had significantly more emergency resections (13⋅9 versus
7⋅2 per cent; P = 0⋅030), as well as complications, treatment
failure and clinical deterioration/disease progression. In
analyses stratified by Hinchey grade, among patients with
Hinchey II disease, significantly more complications were
found in the PCD group (12 versus 3⋅7 per cent; P = 0⋅032).
Figs 1 and 2 show the time-to-event analyses of recurrence
and surgery during long-term follow-up; there were no significant differences in recurrence (P = 0⋅544) or surgery
(P = 0⋅088). Overall, patients in the PCD group had significantly more complications during long-term follow-up
(24⋅3 versus 13⋅9 per cent; P = 0⋅009), which was also evident in the Hinchey Ib subgroup (39 versus 12⋅7 per cent;
P = 0⋅016). The mortality rate was higher in the PCD
group (10⋅4 versus 4⋅8 per cent; P = 0⋅048). In the subgroup
with Hinchey II disease, there were more sigmoid resections among patients who underwent PCD (32 versus 22⋅2
per cent; P = 0⋅046). No other differences between treatment groups were found in short- and long-term outcomes.
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
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Risk factors for treatment failure and emergency
surgery during short-term follow-up
Univariable analyses of all possible predictors for treatment failure and emergency surgery are shown in Table S1
(supporting information). Different cut-off sizes for abscess
diameter were reviewed univariably to analyse which could
best predict outcome. A cut-off size of 3 cm seemed to
be the best predictor of treatment failure (univariable OR
2⋅33, 95 per cent c.i. 1⋅32 to 4⋅11), and a cut-off size of
5 cm the best predictor of emergency surgery (univariable
BJS 2019; 106: 458–466
Non-surgical management of diverticulitis with abscess formation
Multivariable logistic regression analysis of risk factors
for short-term treatment failure and emergency surgery
1·0
Recurrence-free survival (%)
463
Table 3
0·8
0·6
No PCD
PCD
0·4
0·2
0
1000
2000
3000
4000
Time after CT diagnosis of abscess (days)
No. at risk
No PCD 308
PCD
106
233
85
142
55
43
15
0
0
Kaplan–Meier analysis of recurrence-free survival
according to whether the patient underwent percutaneous
abscess drainage
PCD, percutaneous drainage. P = 0⋅544 (log rank test).
Treatment failure
Age (per year)
BMI (per kg/m2 )
Alcohol consumption
Co-morbidity
NSAID prescription
Nausea
C-reactive protein (mg/l)
Abscess ≥ 3 cm
Percutaneous drainage
Emergency surgery
History of abdominal surgery
Rebound tenderness
Abscess ≥ 5 cm
Percutaneous drainage
Odds ratio
P
1⋅001 (0⋅98, 1⋅02)
0⋅94 (0⋅89, 0⋅997)
0⋅63 (0⋅36, 1⋅10)
1⋅40 (0⋅85, 2⋅29)
0⋅58 (0⋅21, 1⋅57)
1⋅32 (0⋅83, 2⋅12)
1⋅001 (0⋅998, 1⋅003)
2⋅05 (1⋅09, 3⋅86)
1⋅47 (0⋅81, 2⋅68)
0⋅955
0⋅041
0⋅099
0⋅183
0⋅242
0⋅245
0⋅656
0⋅027
0⋅185
2⋅05 (1⋅04, 4⋅05)
2⋅03 (0⋅98, 4⋅21)
2⋅96 (1⋅08, 8⋅13)
1⋅29 (0⋅56, 2⋅99)
0⋅038
0⋅058
0⋅036
0⋅554
Values in parentheses are 95 per cent confidence intervals. NSAID,
non-steroidal anti-inflammatory drug.
Fig. 1
1⋅08 to 8⋅13). No other variable had an effect on the risk of
treatment failure or emergency surgery.
Two separate subgroup analyses were performed to assess
the effect of PCD on the outcome for different abscess
sizes (at least 3 cm and at least 5 cm). The first included
only the 324 patients with an abscess of 3 cm or larger.
In this subgroup, there were no differences in rate of
treatment failure between patients treated with (109) or
without (215) PCD (35⋅7 versus 28⋅4 per cent respectively;
P = 0⋅200), or in rate of emergency surgery (14⋅3 versus
9⋅3 per cent; P = 0⋅198). The second subgroup analysis
included only the 185 patients with an abscess size of at least
5 cm. In this subgroup, there were also no differences in
rate of treatment failure between patients treated with (94)
and without (91) PCD (35 versus 28 per cent respectively;
P = 0⋅409), or in rate of emergency surgery (16 versus 12
per cent; P = 0⋅416).
Resection-free survival (%)
1·0
0·8
0·6
0·4
No PCD
PCD
0·2
0
1000
2000
3000
4000
Time after CT diagnosis of abscess (days)
No. at risk
No PCD 331
PCD
113
217
59
133
34
37
14
0
0
Kaplan–Meier analysis of resection-free survival according
to whether the patient underwent percutaneous abscess drainage
PCD, percutaneous drainage. P = 0⋅088 (log rank test).
Fig. 2
OR 2⋅97, 1⋅28 to 6⋅85). The results of multivariable analysis
are shown in Table 3. A higher BMI slightly decreased the
risk of treatment failure (OR 0⋅94, 0⋅89 to 0⋅997), whereas
an abscess size of at least 3 cm increased the risk (OR 2⋅05,
1⋅09 to 3⋅86). With regard to emergency surgery, history
of abdominal surgery increased the risk (OR 2⋅05, 1⋅04 to
4⋅05), as did an abscess size of 5 cm or larger (OR 2⋅96,
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
Risk factors for recurrence and sigmoid resection
during long-term follow-up
Univariable analyses of all possible predictors for treatment
failure and emergency surgery during long-term follow-up
are shown in Table S2 (supporting information) and results
of the subsequent multivariable analysis in Table 4. A history of diverticulitis increased the risk of recurrence (HR
1⋅71, 95 per cent c.i. 1⋅17 to 2⋅48). A history of abdominal
surgery (HR 0⋅63, 0⋅42 to 0⋅98) and sigmoid resection (HR
0⋅15, 0⋅05 to 0⋅48) decreased the risk of recurrence. Older
patients seemed to be at slightly higher risk of sigmoid
resection during long-term follow-up (HR 1⋅02, 1⋅001 to
1⋅03) and the symptoms vomiting (HR 1⋅82, 1⋅13 to 2⋅93)
and nausea (HR 1⋅72, 1⋅03 to 2⋅85) also increased this risk.
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BJS 2019; 106: 458–466
464
D. P. V. Lambrichts, H. E. Bolkenstein, D. C. H. E. van der Does, D. Dieleman, R. M. P. H. Crolla, J. W. T. Dekker et al.
Multivariable Cox regression analysis of risk factors for
recurrence and surgery during long-term follow-up
Table 4
Recurrence
Age (per year)
History of diverticulitis
History of abdominal
surgery
Rebound tenderness
Sigmoid resection during
short-term follow-up
Surgery
Age (per year)
Alcohol consumption
Co-morbidity
History of diverticulitis
Duration of symptoms
(per day)
Nausea
Vomiting
Diffuse abdominal pain
Distant abscess
Free peridiverticular air
Percutaneous drainage
Hazard ratio
P
0⋅995 (0⋅98, 1⋅01)
1⋅71 (1⋅17, 2⋅48)
0⋅63 (0⋅42, 0⋅98)
0⋅481
0⋅005
0⋅040
0⋅72 (0⋅46, 1⋅13)
0⋅15 (0⋅05, 0⋅48)
0⋅152
0⋅001
1⋅02 (1⋅001, 1⋅03)
0⋅64 (0⋅29, 1⋅39)
1⋅49 (0⋅96, 2⋅31)
1⋅30 (0⋅88, 1⋅93)
1⋅01 (0⋅996, 1⋅03)
0⋅042
0⋅218
0⋅078
0⋅190
0⋅136
1⋅72 (1⋅03, 2⋅85)
1⋅82 (1⋅13, 2⋅93)
0⋅60 (0⋅29, 1⋅25)
0⋅72 (0⋅42, 1⋅23)
1⋅39 (0⋅91, 2⋅12)
1⋅08 (0⋅69, 1⋅69)
0⋅037
0⋅014
0⋅161
0⋅221
0⋅129
0⋅736
Values in parentheses are 95 per cent confidence intervals.
No other variable had an effect on the occurrence of sigmoid resection during long-term follow-up.
Sensitivity analyses
Overall, sensitivity analyses of the non-imputed data set
showed similar results for short- and long-term outcomes,
and short-term complications and emergency resection
were not significantly different in hospital-adjusted analyses (Table S3, supporting information). Stratified analyses
by Hinchey grade showed significant differences in the
non-imputed data for short-term readmission and persistent diverticulitis (Table S4, supporting information). In
addition, sensitivity analyses of the non-imputed data set
and hospital-adjusted analyses were undertaken for multivariable logistic regression and Cox regression analyses
(Tables S5 and S6, supporting information).
Discussion
In the present study, multivariable analysis showed that
initial non-surgical treatment of Hinchey Ib and II diverticular abscesses (antibiotics alone versus PCD in combination with antibiotics) had no independent effect on
short- and long-term outcomes. Abscess size of at least 3 cm
was identified as an independent risk factor for short-term
treatment failure, and 5 cm or more as an independent risk
factor for short-term emergency surgery. Previous studies
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
of treatment outcomes of diverticular abscesses have been
limited by factors such as small and single-institution study
populations, a lack of time-to-event analysis and short
follow-up10,12 . The cohort study of 3148 patients with
Hinchey stage Ib and II disease investigated by Gregersen
and colleagues25,26 remains the largest reporting on both
short- and long-term treatment outcomes. However, an
important limitation of that study was the absence of data
on the clinical condition of the patients, as well as data
on abscess size and location. This complicates comparison of treatment modalities because, owing to the introduction of selection bias and confounding, differences in
outcomes may primarily reflect disease and clinical severity. The present study, with a total of 447 patients, took
these patient and disease characteristics into account, and
also assessed long-term outcomes.
The comparison of PCD and no PCD in this cohort
showed that patients who underwent PCD seemed to
have worse outcomes, in terms of a greater likelihood
of short-term emergency resections, complications, disease progression and treatment failure, as well as more
long-term complications. However, confounding by indication cannot be excluded from this analysis and differences
may primarily reflect disease and clinical severity. Indeed,
patients undergoing PCD had more advanced disease than
those in the no-PCD group, with the majority of patients
having Hinchey stage II disease (84⋅3 versus 40⋅7 per cent;
P < 0⋅001). Patients in the PCD group had larger abscesses,
as well as significantly more distant abscesses or multiple abscesses. Hence, when the patients were stratified by
Hinchey grade, most short- and long-term outcomes did
not differ between the PCD and no-PCD groups, with
the exception of short-term complications and long-term
resections among patients with Hinchey II disease, and
long-term complications in those with Hinchey Ib diverticulitis. More importantly, in the multivariable analyses,
the initial treatment strategy did not seem to be a predictor with regard to treatment failure, emergency surgery,
or sigmoid resection in long-term follow-up, strengthening the conclusion that treatment strategy has no effect on
the outcome.
The short-term mortality rate in the present study ranged
between 0 and 2 per cent across the groups analysed, which
is comparable to pooled average mortality rates derived
from previous studies of treatment with antibiotics (0⋅6
per cent) and PCD (1⋅6 per cent)14 . Short-term emergency surgery rates ranged from 5⋅1 to 15 per cent, which
is also largely in accordance with the pooled average of
12⋅1 per cent14 . Reported rates of diverticulitis recurrence
vary from 3 to 68 per cent, with an average of 28 per
cent; recurrent disease consists mostly of uncomplicated
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BJS 2019; 106: 458–466
Non-surgical management of diverticulitis with abscess formation
or locally complicated diverticulitis10 . Although rates may
vary between studies because of differences in median
follow-up or in definitions, the recurrence rates reported in
the present study seem to be in line with earlier reports27,28 .
In light of the long-term surgery and recurrence rates
in the present study, which were relatively low (and the
recurrences mostly uncomplicated), it can be questioned
whether elective surgery is indicated in conservatively managed patients, as surgery comes with an inherent risk of
complication and most patients seem to fare well with conservative management alone.
The rates of adverse and unwanted outcomes in patients
with diverticular abscess remain high and present a major
burden to the patient, as well the healthcare system. Therefore, an aim of the present study was to identify potential
risk factors related to these adverse outcomes in order to
help improve individual patient management. Abscess size
was shown to be an independent predictor of adverse outcome; an abscess diameter of at least 3 cm increased the risk
of short-term treatment failure, whereas an abscess of 5 cm
or larger increased the risk of emergency surgery. These
results indicate that, for abscesses larger than 3 cm, and
particularly those larger than 5 cm, it can still be debated
which treatment strategy is most appropriate, as the results
show no definite advantage of one strategy over the other
in short-term outcomes. Treatment should not be based
solely on abscess size, but other patient and disease characteristics should also be considered. However, no other significant predictors were found in the multivariable analyses
for treatment failure or emergency surgery, making it difficult to select a subpopulation of patients who would benefit
from PCD. The findings do seem to acknowledge that
a cut-off value of 3 cm is appropriate for differentiating
between small and large abscesses11,13,17,29,30 .
An important limitation of this study is its retrospective
design, which introduces the potential for selection bias
and confounding by indication. However, registration of
a wide range of baseline patient and disease characteristics
allowed correction for potential known confounders in
multivariable logistic and Cox regression analyses. Another
inevitable consequence of retrospective observational
research is the potential risk of missing data, as the availability of baseline and outcome data is largely dependent
on the completeness of medical records. It was hypothesized that re-evaluation of CT images by one or more
radiologists could have led to the introduction of (hindsight) bias, as a result of the radiologists’ foreknowledge of
the reasons for and outcomes of reviewing the images. To
prevent selection bias introduced by missing data, multiple
imputation methods were used to handle the missing data.
Sensitivity analyses of the non-imputed data set did not
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
465
significantly change the results. With regard to outcome
data, it is possible that patients might have received care at a
general practitioner or in other hospitals during follow-up,
creating the potential for an underestimation of disease
recurrences and readmissions. Finally, the multicentre
setting of this study could have introduced heterogeneity
through between-hospital differences in treatment, such
as reasons for choosing PCD or criteria for drain removal.
However, these differences were considered small, because
all hospitals base their practice on the national guideline
for treatment of acute diverticulitis and hospital-adjusted
analyses showed comparable outcomes. In addition, the
multicentre setting had beneficial effects by increasing
both the study’s generalizability and sample size.
This study of a large cohort of patients with Hinchey
stage Ib and II abscesses has provided evidence that patients
with abscesses of at least 3 or 5 cm are at a higher risk of
short-term treatment failure or emergency surgery respectively, regardless of the choice of non-surgical treatment
strategy. As no clear difference between the two treatment
strategies was found, it remains debatable how to treat
these patients appropriately. Nevertheless, these data help
facilitate informed and shared decision-making, as well
as providing valuable information for future prospective
studies regarding PCD treatment in patients with abscess
formation.
Acknowledgements
D.P.V.L and H.E.B. are joint first authors of this article.
Disclosure: The authors declare no conflict of interest.
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Supporting information
Additional supporting information can be found online in the Supporting Information section at the end of the
article.
© 2019 The Authors. BJS published by John Wiley & Sons Ltd
on behalf of BJS Society Ltd.
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