Key words diverticulitis - diverticulosis - CDD - CT - diverticular disease
Introduction
Diverticulosis is a widespread disease seen in increasingly younger patients in Western countries in particular [1 ]. To date, the stages have typically been stratified according to Hinchey et al. as modified by Wasvary et al. [2 ]
[3 ] (Hinchey-Wasvary classification) in Anglo-America and according to Hansen & Stock in Germany [4 ]. None of these classification systems fully reflects the current state of knowledge of the courses of diverticular disease and its prognosis, diagnosis, and treatment options.
The Classification of Diverticular Disease (CDD) has been available since the publication of the S2k Guidelines on Diverticular Disease/Diverticulitis [5 ] in 2014. The classification system based on these modern guideline recommendations is intended to combine the descriptive-morphological qualities of the earlier systems and to better reflect currently available interdisciplinary treatment options. Schreyer at al. reviewed these guidelines with respect to their significance for radiology and their effect on diagnostic and therapeutic algorithms for diverticular disease [6 ].
Computed tomography (CT) has largely become established as the method of choice for radiological diagnosis [7 ]. The present article discusses the different categories with the individual CDD types of this classification with a focus on application in computed tomographic diagnosis. For every stage the article provides typical image material and references to practice-oriented commonalities and differences with respect to previous classification systems.
Basic information
Colonic diverticula are pseudodiverticula. They are defined in the guidelines as “acquired outpouchings of the mucosa and submucosa through weak spots in the colon wall” [5 ]
[8 ]
[9 ]
[10 ]. Points of passage of vessels are hypothesized to be a structural correlate of these weak spots. Age, genetic variables, and a low-fiber diet are defined as risk factors [10 ]
[11 ]
[12 ]
[13 ]
[14 ]
[15 ]
[16 ]
[17 ]
[18 ]
[19 ]
[20 ]. Additional factors such as medication and comorbidities are the subject of current research [21 ]
[22 ]
[23 ]
[24 ]
[25 ]
[26 ]. In this country, the majority of diverticula are seen in the sigmoid colon.
Non-irritated diverticula do not require treatment.
According to the S2k guidelines, treatment is first required in the case of diverticular disease, defined by the occurrence of symptoms or complications. Typical courses starting with type 2 of the CDD include diverticulitis/peridiverticulitis, abscess formation, a covered or open perforation with peritonitis, bleeding, and stenosis, conglomerate and fistula formation.
Differential diagnoses
In addition to sigmoid diverticulitis, there are a number of other differential diagnoses that also need to be considered during examination and evaluation. Due to the often non-specific symptoms, medical-surgical, gynecological, and urological diseases must be taken into consideration. This includes all types of colitis (infectious, ischemic, chronic inflammatory, non-inflammatory, medication-induced, radiation-induced, neutropenic), neoplastic processes such as colorectal carcinomas and abdominal and retroperitoneal abscesses and hematomas. In addition, the entire spectrum of differential diagnoses of abdominal pain must be considered, such as appendicitis, irritable bowel syndrome, herniations and adhesions, aneurysms, cystitis, urolithiasis, endometriosis, extrauterine pregnancy, adnexitis, and tubo-ovarian abscess [5 ]
[27 ].
Classifications
Various systems for the classification of diverticular disease have been proposed in the past [12 ]
[28 ]. From today's standpoint, the most commonly used classification systems, the Hinchey-Wasvary classification and the Hansen & Stock classification, are suboptimal for different reasons [2 ]
[3 ]:
The Hinchey classification system commonly used in Anglo-America was originally created with a limited surgical scope. It was intended to allow stratification of macroscopically perforated courses of diverticulitis according to the correspondingly indicated surgical procedure. Therefore, the differentiation of these courses is good. In the modified version according to Wasvary et al. [3 ], an attempt was made to expand the Hinchey classification to include courses treated on an outpatient basis (creation of the category “mild clinical diverticulitis”). However, mild diverticulosis, chronic courses, and diverticular bleeding are not included.
In contrast, the Hansen & Stock classification system used in Germany was designed primarily as a comprehensive taxonomy of the different courses of diverticular disease. It includes categories for mild diverticulosis and for acute, uncomplicated, and complicated diverticulitis and for chronic recurrent courses. However, the Hansen & Stock classification system does not provide more detailed differentiation between courses with abscess formation, courses with perforations, chronic courses, and courses with bleeding.
The CDD addresses this problem and includes all important courses of the disease on an interdisciplinary basis. At the same time, it differentiates between subtypes that are stratified by therapy according to the current state of knowledge. In this regard, it combines and expands the positive qualities of the earlier systems.
CT acquisition technique
Other than a reference to the minimization of radiation exposure, the guidelines do not provide an explicit recommendation regarding the CT acquisition technique. The technique can be selected based upon the clinical situation. According to Schreyer et al., high-quality, current comparative studies regarding the diagnostic value of intravenously (i. v.), orally or rectally administered contrast agent are not yet available [6 ]. The use of intravenous contrast agent is not mandatory to make a diagnosis [29 ] but intravenously administered contrast agent increases the value of the examination with respect to possible differential diagnoses. The formation of abscesses in acute diverticulitis (CDD type 2: enhancement of the abscess capsule), increased vascularization (starting with CDD type 1a) and phlegmonous reaction of the surrounding tissue (starting with CDD type 1b) are visualized effectively with i. v. contrast agent. Particularly in obese patients, there are initial indications that contrast agent is not necessary needed [27 ].
The use of orally and rectally administered water-soluble contrast agent is a controversial topic of discussion and is also not defined in the guidelines: There is general consensus that enteral contrast agent administration facilitates the visualization of the intestinal wall and diverticula. Also in the differentiation between intestinal lumen and abscesses or air inclusions and for the visualization of fistulas, stenoses, and perforations with leakage, rectally administered contrast agent can be helpful and provide an indication for surgical treatment. Moreover, luminal masses can be better visualized. Due to a lack of definitive evidence regarding the benefit of enteral contrast enhancement, the design of available studies as well as the implemented examination protocol are highly heterogeneous [5 ]
[6 ]
[29 ]
[30 ]
[31 ]
[32 ]
[33 ]
[34 ]
[35 ]
[36 ]
[37 ]
[38 ]
[39 ]
[40 ].
CDD classification in CT diagnosis
[Table 1 ] presents the types of the CDD with brief explanations and allows comparison of the individual categories of the three discussed classification systems. It also provides an overview of the current treatment options stratified according to CDD type (the article by Schreyer et al. [6 ] provides a more detailed explanation).
Table 1
Classification systems of diverticular disease and stratified therapy: Overview of the Classification of Diverticular Disease (CDD) and therapies stratified by CDD type. The left part of the table shows the categories of Hansen & Stock Classification (column “HSK”) and of Hinchey Classification modified by Wasvary et al. (column “HWK”) corresponding to the respective CDD types. Inexact matches are marked with “~”. The lack of an equivalent category is marked with “ – “.
HSK
HWK
CDD
description/finding
explanation
treatment
0
–
0 – asymptomatic diverticulosis
mild diverticulosis without signs of inflammation
Incidental finding, asymptomatic, no disease
–
1 – acute uncomplicated diverticular disease/diverticulitis
uncomplicated local inflammation
1
0
1a
diverticulitis/diverticular disease without reaction of surrounding tissue
symptoms related to diverticula, optional: signs of inflammation (lab), optional: typical cross‐sectional imaging
outpatient: primarily conservative without antibiotic treatment, surgery not required in the interval
2a
1a
1b
diverticulitis with phlegmonous reaction in surrounding tissue
obligatory: Signs of inflammation (lab), obligatory: cross‐sectional imaging: phlegmonous diverticulitis
2 – acute complicated diverticulitis
as in 1b, additionally:
2b
~1b
2a
microabscess
covered perforation, small abscess (≤ 1 cm); minimal paracolic air
inpatient: primary antibiotic therapy, parenteral fluid substitution when necessary, abscess drainage if possible, surgery in interval if necessary
~2
2b
macroabscess
para‐ or mesocolic abscess (> 1 cm)
2c
2c
free perforation
free perforation, free air/fluid, generalized peritonitis
inpatient: Emergency surgery
3
2c1
purulent peritonitis
4
2c2
fecal peritonitis
–
3 – chronic diverticular disease
recurrent or chronic symptomatic diverticular disease
~3
3a
symptomatic uncomplicated diverticular disease (SUDD)
typical symptoms, optional: signs of inflammation (lab)
possibly mesalazine (off‐label)
3
3b
recurrent diverticulitis without complications
signs of inflammation (lab), typical crosssectional imaging
decision on individual basis, no general recommendation regarding elective surgery in the interval
3c
recurrent diverticulitis with complications
detection of stenoses/fistulas/conglomerate
inpatient: Elective surgery
–
4 – Diverticular bleeding
diverticular bleeding
detection of a diverticula as source of bleeding
inpatient: Endoscopic hemostasis if possible, otherwise angiographic embolization or surgery
Asymptomatic diverticulosis
CDD type 0 ([Fig. 1 ]) refers to asymptomatic diverticulosis and corresponds to stage 0 of the Hansen & Stock classification. It is not included in the Hinchey-Wasvary classification system. After the 40th year of life, it is a common incidental finding without immediate clinical significance in industrialized nations. Non-irritated, thin-walled air figures near the wall are visualized.
Fig. 1 CDD type 0: Abdominal post-contrast CT scan of a 76-year-old woman. Axial a , coronal b , sagittal c and enlarged axial plane d . This diverticular disease was an incidental finding. The non-irritated diverticula can be perceived as round figures of air on the side of the bowel measuring 5 – 10 mm (see arrows). No increased vascularization or stranding of the adjacent fat can be seen.
Acute uncomplicated diverticular disease/diverticulitis
CDD types 1a-b refer to acute, uncomplicated courses that can be primarily conservatively treated on an outpatient basis with frequent clinical follow-up.
However, presentation usually only occurs in advanced stages of diverticulitis requiring hospitalization.
CDD type 1a ([Fig. 2 ]) includes acute symptoms and possibly elevated inflammatory markers in the blood analysis. The detection of CDD type 1a is challenging in CT diagnosis due to the only slight morphological deviation from normal findings and is more successful with knowledge of the patient's symptoms. The guidelines define an intestinal wall thickness of up to 3 mm as normal. If this value is exceeded near a diverticulum and/or increased vascularization is seen, diverticulitis CDD type 1a is present from a morphological standpoint. This corresponds to stage 1 of the Hansen & Stock classification and category 0 of the Hinchey-Wasvary classification.
Fig. 2 CDD type 1a: Abdominal CT scan of a 73-year-old woman with intravenous contrast agent. Axial a , coronal b , sagittal c and enlarged axial plane d . The inflamed diverticula show a tailed, thickened wall (see arrows) and lightly increased vascularization. No stranding of the adjacent fat can be seen.
Diagnosis of phlegmonous peridiverticulitis is more common and easier due to the detection of bleeding into the surrounding tissue ([Fig. 3 ]). Its presence defines CDD type 1b on CT. Phlegmonous peridiverticulitis corresponds to stage 1a of the Hinchey-Wasvary classification system. In the Hansen & Stock classification system, it was defined as a low-grade complicated course (stage 2a) while the CDD now interprets it as a higher-grade uncomplicated course. This categorization as uncomplicated CDD type 1 reflects today's more conservative treatment regimen for peridiverticulitis without abscesses due to the improved antibiotic options ([Table 1 ]).
Fig. 3 CDD type 1b: Abdominal CT scan of a 71-year-old man with intravenous, oral, and rectal positive contrast agents. Axial a , coronal b , sagittal c and enlarged axial plane d . In addition to the thickened bowel wall and the increased vascularization, CDD type 1b is defined by a phlegmonous reaction of the surrounding tissue.
Acute complicated diverticulitis
CDD types 2a-c include the complicated courses of acute diverticulitis.
In addition to meeting the criteria for CDD 1b, CDD types 2a and 2b refer to a covered perforation with an abscess with a diameter ≤ 1 cm (CDD type 2a, [Fig. 4 ]) or > 1 cm (CDD type 2b, [Fig. 5 ]).
Fig. 4 CCD type 2a: Abdominal CT scan of a 37-year-old man with intravenous contrast agent. Axial a , coronal b , sagittal c and enlarged axial plane d . In addition to the criteria of type 1b, this CT shows an abscess with peripheral contrast medium enhancement. Measuring 8 mm, it corresponds to CDD type 2a (diameter < 1 cm).
Fig. 5 CDD type 2b: Abdominal CT scan of a 59-year-old woman with intravenous, oral, and rectal positive contrast agents. Axial a , coronal b , sagittal c and enlarged axial plane d . The criteria of CDD type 1b are met, but the abscess measures 50 mm, so it corresponds to CDD type 2b (diameter > 1 cm).
The microabscess of CDD type 2a corresponds most closely to stage 1b of the Hinchey-Wasvary classification system. However, abscesses near the focus with a diameter of up to 5 cm are included in this category in the Hinchey-Wasvary classification system. Abscesses > 5 cm (category 2 of the Hinchey-Wasvary classification system) correspond to the next higher CDD type (2b). In contrast, stage 2b of the Hansen & Stock classification system defines only a single, not further differentiated category for courses with abscess formation. The inpatient treatment concept for courses with covered perforation is currently largely based on the administration of antibiotics and interventional abscess drainage. Surgery is directly indicated in the case of a lack of response to treatment or disease progression, while surgery is first indicated in the inflammation-free interval in the case of response to treatment.
It must be taken into consideration in the diagnosis that covered perforated CDD stages 2a and 2b are often associated with minimal paracolic air and CDD type 2c is only indicated in the case of the detection of free abdominal air and/or fluid with peritonitis. CDD type 2c differentiates between purulent peritonitis (CDD 2c1, [Fig. 6 ]) and fecal peritonitis (CDD 2c2) and requires emergency surgical intervention. Stage 2c of the Hansen & Stock classification system includes free perforations without further differentiation, while categories 3 (purulent peritonitis) and 4 (fecal peritonitis) of the Hinchey-Wasvary classification correspond to CDD types 2c1 and 2c2.
Fig. 6 CDD type 2c: Abdominal CT scan of a 51-year-old man. Axial a , coronal b , sagittal c and enlarged axial plane d . It shows diverticulitis with free perforation (white arrows: diverticulitis with reasonable spot of perforation) and detection of free air (black arrows). This corresponds to CDD type 2c. There are no findings of generalized peritonitis.
Chronic diverticular disease
CDD types 3a-c differentiate between chronic types of diverticular disease. The Hinchey-Wasvary classification system does not include chronic courses. Stage 3 of the Hansen & Stock classification system is an undifferentiated category for all chronic courses of the disease.
CDD type 3a, i. e., Symptomatic Uncomplicated Diverticular Disease (SUDD), presents on CT as CDD type 0 and does not have its own morphological characteristics. However, in contrast to CDD type 0, SUDD is characterized by the persistence of clinical symptoms even though there are no longer indications of inflammation on imaging and macroscopically. This patient group and the underlying pathomechanism have not yet been characterized in detail. Strate et al. describe neuropeptidergic mucosal changes, slightly elevated calprotectin values, and histological indications of chronic persistent inflammation of the intestinal wall [41 ]. Off-label treatment with mesalazine can be attempted [42 ]. However, changes in treatment recommendations can be expected in coming years.
CDD type 3b, i. e., recurrent uncomplicated diverticulitis, corresponds morphologically to non-perforated CDD type 1a or 1b and can only be correctly detected and described on CT with clinical case knowledge.
With stenosis, conglomerate, or fistula formation ([Fig. 7 ] for example of stenosis), the complicated courses of CDD type 3c have distinct morphological characteristics. Onur et al. provided a current description of these complications [43 ].
Fig. 7 CDD type 3c: Abdominal CT scan of a 63-year-old man with intravenous contrast agent. Axial a , coronal b and sagittal plane c and additional curved planar reformation d . Postinflammatory stenosis with clear distension of the preceding intestinal loops, visible especially in the coronal plane. Along with fistula and conglomeration, these findings correspond to CDD type 3c.
Diverticular bleeding
CT is not primarily used to diagnose diverticular bleeding (CDD type 4). It is diagnosed by detecting a diverticulum as the source of bleeding typically on the basis of endoscopic images ([Fig. 8 ]). It is not included in the systems prior to the CDD. It is usually primarily treated today by endoscopic hemostasis. In the case of continued bleeding, angiographic embolization or surgery is performed.
Fig. 8 CDD type 4: Endoscopic images of different patients with bleeding into the intestinal lumen (see arrows).
Summary
The CDD is an updated system for categorizing the stages of diverticular disease that is included in the current S2k guidelines for treating this disease. Its categories, i. e., the CDD types, combine the descriptive morphological qualities of the earlier systems as well as facilitate stratified indication determination for hospitalization and treatment in accordance with the guidelines. As a widespread disease with an increasingly younger age at onset in this country, diverticular disease is a constant in routine CT diagnosis with growing significance. CDD in connection with the current guidelines allows targeted communication and decision-making for treatment.
