DISCUSSION
Cystica profunda is a rare benign non-neoplastic disease that can occur
throughout the gastrointestinal tract, mostly in the rectum, followed by
the colon, and more rarely in the stomach and small intestine. It is
also known as gastritis cystica profunda (GCP), enteritis cystica
profunda (ECP), and colitis cystica profunda (CCP)[4]. CCP is a rare benign disease occurring in the
rectum or colon, most commonly in the anterior wall of the rectum. The
pathogenesis of CCP is unknown and is thought to be due to congenital or
acquired mucosal muscle weakness caused by inflammation, infection,
trauma or ischemia resulting in embedding of the mucosal epithelium in
the submucosa [5]. The main histological features
are the presence of multiple cysts of varying size and morphology in the
submucosa lined with a single layer of flattened or columnar epithelial
cells, which are filled with mucus, and the disappearance of some of the
covered epithelium of the cyst wall, forming a mucus lake[6].
CCP can occur at any age, most common in young and middle-aged people
aged 30-40 years, and is more common in men. The clinical manifestations
of CCP are diverse and nonspecific, mainly including abdominal pain,
diarrhea, constipation, blood in stool, mucus stool, urgency, rectal
pain, change in stool habit, internal rotation, abdominal mass and
intestinal obstruction [7-9]. According to the
extent of invasion, there are diffuse and local types[10]. The diffuse type involves the entire colon
with villous or tipped polypoid lesions or even ulcers, mostly due to
intestinal inflammation and ulceration. It is associated with Crohn’s
disease, ulcerative colitis, infectious colitis and radiation enteritis[11,12]. The local type is mostly seen in the
anterior wall of the rectal 5-12 cm from the anal verge, presenting as
nodules or polyps, which is associated with rectal prolapse and isolated
rectal ulcer syndrome. The local type is the most common, while the
diffuse type accounts for less than 15% of cases reported in the
literature [1,3,13,14]. Both of the two cases in
this paper were young and middle-aged patients with clinical
characteristics of mucous excretion. The locations of all cases were
located in the anterior rectal wall of 5-12cm from the anal verge, which
was consistent with the location reported in the literature. Both cases
showed nodularity and belonged to the local type.
The imaging findings of CCP are characteristic. X-rays are normal or
nonspecific in the early stage, or show luminal narrowing and
irregularity due to multiple submucosal cystic structures. Barium enema
shows single or multiple filling defects or shows thickened folds. CT
images show a non-infiltrating submucosal mass with well-defined borders
and an unenhanced cystic lumen of variable sizes. The perirectal adipose
tissue was absent and the levator anus muscle was thickened[2,15]. MRI showed a homogeneous low signal on
T1WI and a submucosal high signal nodule on T2WI, with no significant
enhancement on contrast-enhanced images, high signal on DWI, no
diffusion restriction on ADC, and significant high signal on T2WI
suggesting that the presence of mucin in the lesion[4,16]. In both cases in this paper, CT showed
non-enhancing hypodense lesions with clear borders, calcifications at
the margins, smooth mucosa, intact rectal wall, clear surrounding fatty
spaces, and no enlarged lymph nodes. MRI presentations were also
consistent with the above imaging manifestations. However, the
thickening of the levator anus muscle described in the literature was
not present. In addition, the presence of calcification of the cyst wall
was described in our case, which suggests a chronic benign disease and
not associated with rectal cancer where calcification usually inside the
tumor [17].
Colonoscopy in CCP shows tipped or villous polypoid lesions covered by
normal, edematous or ulcerated mucosa, or shows polypoid or nodular
mucosal thickening with or without ulceration, which can be easily
confused with colorectal cancer [8]. In contrast,
colonoscopy allows biopsy and therefore has the dual advantage of
obtaining both imaging and pathology at the same time. However, due to
insufficient depth of biopsy and limited sampling, it is easy to missed
diagnosis and misdiagnosis. In case 2, the results of the first external
colonoscopy biopsy only showed chronic inflammation of the mucosa with
erosion, which may be related to the shallow and limited sampling.
ERUS showed multiple hypoechoic or anechoic cysts in the submucosal
layer of the rectum with a small amount of internal echogenicity, no
involvement of the mucosal layer, no lymphadenopathy, and no penetration
or invasion of the muscular layer beyond the submucosal layer[4,9]. In this paper, ERUS showed cystic lesions
in the submucosal layer in both cases, with the mucosal and serous
layers intact. The difference between the two cases is that the lesion
was located in the submucosal layer and the intrinsic muscular layer,
with invasion of the muscular layer in case 1. While in case 2, the
lesion was located only in the submucosa, and the intrinsic muscle layer
was not invaded outside the submucosa. ERUS can clearly localize the
different layers of the intestinal wall and can assess whether the
mucosal layer, intrinsic muscular layer, and serous layer of the
intestinal wall are intact. Although ERUS cannot confirm the diagnosis,
it is of great importance to exclude malignant tumors in the deeper
layers of the intestinal wall. Moreover, ERUS is safe, noninvasive,
nonradioactive, easy to perform, well tolerated, and can be repeated as
a follow-up examination.
CCP is similar to benign and malignant colorectal tumors and
inflammatory bowel disease, and the diagnosis of CCP also requires the
identification of any colon or rectal polypoid or intramural benign or
malignant masses (adenomatous polyps, polypoid inflammatory granulomas,
leiomyomas, lipomas, adenocarcinomas, mucinous carcinomas, sarcomas),
inflammatory lesions (ulcerative colitis, Crohn’s disease, and ischemic
colitis or proctitis), and endometriosis [10].
The goal of treatment for CCP is to prevent or reduce symptoms.
Depending on the severity of symptoms, treatment can be either
conservative medical or surgical. Patient education and behavior
modification are the primary treatments for patients with CCP.
Conservative treatment includes bowel habits, postural correction,
avoidance of stress and strain, and increased dietary fiber can
alleviate symptoms in the majority of patients. Conservative treatment
is ineffective and surgical resection is required when symptoms are
persistent or severe, such as bowel obstruction, bleeding, or rectal
prolapse[18,19]. In recent years, endoscopic
submucosal dissection (ESD), with the advantages of rapid recovery,
minimal trauma, and preservation of colonic integrity, has been widely
used in the treatment of CCP [20].
In conclusion, CCP is a rare disease that is difficult to diagnose and
easily misdiagnosed as other occupying lesions of the intestine because
of its low incidence, lack of specificity in clinical and endoscopic
manifestations, and lack of awareness among physicians in various
disciplines. Once misdiagnosed, it not only brings unnecessary painful
surgical resection to patients, but also poses risks to physicians. In
contrast, imaging study plays a crucial role in both disease detection
and differentiation from malignant diseases, helping to initially
determine the benignity and malignancy of the lesion and avoiding
erroneous radical resection surgery.
ACKNOWLEDGMENT
Supported by the program of Guangdong Provincial Clinical Research
Center for Digestive Diseases (2020B1111170004).