Ángel Caunedo Álvarez, MD, Gastroenterology Service, “Virgen Macarena” University Hospital, Avda. Dr. Fedriani, Seville 41071, Spain. acaunedoa@meditex.es
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Ángel Caunedo-Álvarez, Javier Romero-Vazquez, Juan M Herrerias-Gutierrez, Gastroenterology Service, “Virgen Macarena” University Hospital, Av Dr. Fedriani, Seville 41071, Spain
ORCID number: $[AuthorORCIDs]
Correspondence to: Ángel Caunedo Álvarez, MD, Gastroenterology Service, “Virgen Macarena” University Hospital, Avda. Dr. Fedriani, Seville 41071, Spain. acaunedoa@meditex.es
Telephone: +34-955-008801 Fax: +34-955-008805
Received: February 15, 2008 Revised: July 26, 2008 Accepted: August 2, 2008 Published online: September 14, 2008
Figure 2 Schematic drawing of AGILE® patency Capsule.
Since Iddan et al[1] reported the new wireless endoscopy system the capsule endoscopy (CE) has become one of the most significant technical innovations of Gastroenterology in recent years. Regarding the complications of the techniques, some incidental cases of impaction in a Meckel´s diverticulum[2], a Zenker´s diverticulum[3], or in the cricopharyngeal muscle[4], as well as aspiration of the capsule[5-7], solved without complications, have been reported. However, the most frequent side effect is undoubtedly the non-natural excretion (NNE) of the capsule due to a stricture or a tumor in the small bowel. The retrospective analysis of some series indicates that the incidence of NNE depends on the indication for the capsule exam: 0% in healthy controls[8], 1.4% in obscure gastrointestinal bleeding[9-13], 1.48% in suspected Crohn´s disease[14-17], 5%-13% in known Crohn´s disease[17-19] and 21% in suspected small bowel obstruction[20].
In the vast majority of cases, capsule retention, regardless of its cause, is asymptomatic, being evidenced by the absence of excretion and confirmed by means of radiology. On the other hand, capsule retention frequently allows for the identification of the bowel pathology which caused the symptoms in the patient and which could not have been diagnosed by means of standard methods, furthermore facilitating the location of the stricture or the tumor for the surgeon after “milking” the capsule through the bowel. For these reasons, many authors have described NNE as a “therapeutic complication” of the CE[21-23]. However, although this consideration is valid for patients with tumors or those with stricture due to NSAIDs, radiotherapy or previous abdominal surgery, it may not be valid in patients with stenoses secondary to Crohn’s disease. Unlike the previously mentioned groups, in patients with Crohn’s disease, surgery is not curative and may present more complications, thus in this case, NNE of the capsule can become more an “undesirable circumstance” than a “therapeutic complication”. The same can be said of those patients showing high surgical risk or who would not be willing to undergo surgery in the event that NNE occurs.
Current imaging techniques can show long or medium stenoses, with great reduction of the lumen size; however, short stenoses usually cannot be detected by standard methods. This fact explains that in most of the reported cases of non-natural excretion (NNE) of the capsule, the previous performance of the usual radiological studies was not capable of diagnosing the intestinal strictures which the capsule clearly showed[9,11-13,19-21]. It is, therefore, proven that the lack of findings in radiological techniques does not rule out the existence of a bowel stenosis.
The manufacturing company of the PillCamSB has recently developed a new system (Given® M2A Patency System) which has as an objective of checking the patency of digestive tract, in a non-invasive manner. The Patency Capsule (PC) consists of a small identification tag (RFID), detectable by radiofrequency, which is surrounded by an absorbable material with a small amount of barium, all this covered by an external cover (Figure 1). PC has the same dimensions (11.4 mm × 26.4 mm) and the same shape as the standard capsule. PC is designed to remain intact in the gastrointestinal tract for about 80 h. After this period, if still within the body, it spontaneously disintegrates, except for the identification tag, whose small size (3 mm × 13 mm) allows it to pass through a stenosis of a very reduced lumen size. The persistence of the PC inside the organism can be verified by means of radiology, or with a radiofrequency emitting external detector device locating the identification tag.
CLINICAL TRIALS WITH PATENCY CAPSULE
Clinical experience with PC is still limited. A prospective, multi-center trial was designed to assess the clinical usefulness and safety of the PC capsule in patients with intestinal strictures suspected from clinical and/or radiological data. The global data of this trial have not been published, but the results of four of these centers have been reported (Table 1)[24-27]. In the series reported by Spada et al[24], 30 out of 34 (88.2%) patients with known or suspected small bowel stricture retrieved the capsule in the stool. After the excretion, the PC was intact in 20 cases (median transit time 22 h), and disintegrated in 10 patients (median transit time 53 h). Ten patients underwent video capsule endoscopy following the patency capsule examination. In all of these the video capsule passed through the small-bowel stricture without complication. The rate of patients with the PC excreted intact was similar in the seria of Boivin et al[25] (16/22, 73%), Delvaux et al[26] (16/22, 73%), Signorelli et al[27] (26/32, 81%). In our center, the percentage of cases with PC excreted intact was significant lower (13/29, 45%), probably because of patient selection[28]. In all the seria, the patency system scanner showed a good agreement (94%-100%) with fluoroscopy findings in identifying the presence of the tag in the body and may be used to detect the presence of the patency capsule without the need for radiology.
All these authors conclude that PC was unable to detect the presence of a small bowel stricture as previously defined by radiological techniques, but it added crucial information on the functional patency of the stenoses, and this information could allow a distinction between rigid fibrotic strictures and flexible ones. Boivin et al[25] found that passage of an intact capsule that is accompanied by severe pain, similar to disintegration of the capsule with or without pain, seems indicative of a clinically relevant small-bowel stricture and is associated with a high probability of surgery. This observation seems to be confirmed by a recent retrospective analysis of 42 patients who underwent PC with known or suspected small bowel stricture[29]. In this study, the rate of patients who need to be operated in a period of three months was significantly higher in those with a delayed excretion, with the capsule excreted deformed, or with pain during the procedure. Moreover, in patients where painless natural expulsion of the intact PC occurred, CE could be applied without problems despite radiographic evidence of small-bowel strictures. This is an important finding since it might open the path to CE for about 60% of patients where video capsule investigation would otherwise be denied on grounds of history and radiological findings.
Abdominal pain during the procedure seems to be the main complication of PC (Table 2), observed in almost 20% of the cases reported to date. Probably, this pain is secondary to symptomatic intestinal occlusion, and it resolves spontaneously when the disintegration process concludes. However, at least four cases of occlusion did not respond adequately to conservative treatment and needed surgery. According to Gay et al[30], the problem could be that when the PC entrapped in a very tight stenosis it might not have been in contact with fluids and, therefore, only started to dissolve 48 h later, after moving back to the enlarged intestinal loop where it encountered fluids. Another possible factor is proposed by Gay et al[30]; PC is mainly made of lactose and the presence of lactase, an enzyme produced by intestinal mucosal cells, may be of importance in initiating the dissolution process. As lactase is mainly produced in the jejunum, one may also assume the enzyme is massively destroyed before the intestinal content reaches the ileum and that in the cases of occlusion, the enzyme could not have interacted with the capsule material. These authors[26,31] conclude that the start of dissolution at 40 h after ingestion is too slow to prevent episodes of intestinal occlusion, and so, it should be used cautiously under clinical surveillance in patients with Crohn´s disease.
In summary, the AGILE Patency capsule seems to be a useful, non-invasive tool to identify which patients with suspected strictures could safely ingest the standard video capsule. It has been designed to minimize the risk of intestinal occlusion.
Footnotes
Peer reviewer: Amado S Peña, Professor, Department of Pathology, Immunogenetics, VU University Medical Centre, De Boelelaan 1117, PO Box 7057, Amsterdam 1007 MB, The Netherlands
S- Editor Zhong XY L- Editor Rippe RA E- Editor Lin YP
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