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DOI:10.2214/AJR.04.1628
AJR 2006; 186:110-113
© American Roentgen Ray Society

Clinical Observations

CT Findings for Postsurgical Blind Pouch of Small Bowel

Kumaresan Sandrasegaran1, Dean D. T. Maglinte1, Arumugam Rajesh2, Mark Tann1 and Kenyon K. Kopecky3

1 Department of Radiology, Indiana University School of Medicine, UH 0279, 550 N University Blvd., Indianapolis, IN 46202-5253.
2 Department of Radiology, Leicester Royal Infirmary, Leicester, England.
3 Department of Radiology, Community North Hospital, Indianapolis, IN.

Received October 17, 2004; accepted after revision January 10, 2005.

 
Address correspondence to K. Sandrasegaran.


Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
OBJECTIVE. Our objective was to define the CT criteria for blind pouches formed after enteric anastomosis.

CONCLUSION. Familiarity with the CT appearance of blind pouches avoids the mistaking of these entities for bowel obstruction or abscesses.

Keywords: blind pouch • CT • enteric anastomosis • enteroclysis • postoperative complication


Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
With the increasing complexity of surgical procedures, the radiologist often is faced with postoperative CT examinations on which findings can be difficult to interpret. At our institution, we found several CT reports that misinterpreted postoperative changes because the radiologist was unaware of the type of surgery performed or regarded an expected postoperative phenomenon as a complication. In some cases, blind pouches have been reported as bowel obstruction or postoperative abscesses.

The formation of blind pouches has been described previously in the gastrointestinal [1–3] and surgical [4–8] literature as a complication of bowel anastomosis. Blind pouches resulting from enteric anastomosis have abnormal peristalsis that causes filling rather than emptying of the pouch (Fig. 1). As a result there may be bacterial overgrowth with diarrhea and reduced vitamin B12 absorption. This clinical picture is termed blind-pouch syndrome. Bacterial overgrowth (stagnant-bowel syndrome) may also occur after other conditions causing bowel dysmotility, including scleroderma, amyloidosis, diabetic autonomic neuropathy, jejunal diverticulosis, and surgical bypass procedures resulting in blindly ending bowel loops (such as afferent loops) [9]. A blind pouch is not created surgically by intention, unlike a blind loop, which is fashioned purposefully by the surgeon.



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  		Fig. 1 —Blind pouch formation. Drawing shows development of blind pouch after side-to-side enteroenterostomy. Arrows show direction of peristalsis, which fills rather than empties pouch. Dotted line shows contour of bowel immediately after surgery, before development of blind pouch. (Reprinted with permission from Indiana University Trustees, Office of Visual Media).

 
Prior radiologic reports of blind pouches have been case reports focusing on small-bowel contrast studies [10–13]. We are not aware of recent reports on the CT features of this complication. This study was undertaken to describe the CT findings of small-bowel blind pouches to help radiologists avoid errors in anatomic interpretation.


Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Patients
A retrospective search of reports of abdominal CT examinations at our institution between January 2001 and July 2004 revealed 30 patients with at least one report mentioning a blind pouch. The clinical records were reviewed to determine the type of surgery performed and the interval between surgery and imaging examinations. All conventional CT and CT enteroclysis examinations available on soft copy were downloaded onto an Mx8000 workstation (Philips Medical Systems) for review. Hard copies were also reviewed if no digital images were available. We were unable to review the imaging studies of two patients because the studies had been performed elsewhere (n = 1) or the images could not be located (n = 1). The remaining 28 patients formed the study group (11 men and 17 women; age range, 28–75 years; mean, 46.8 years). The prior operative records were not available for two patients who had undergone abdominal surgery at least 12 years earlier. In the other 26 patients, enteric anastomosis after resection of bowel had been performed because of Crohn's disease (n = 6), adhesions resulting from a wide variety of surgeries (n = 8), the Whipple procedure (n = 3), orthotropic liver transplantation (n = 3), bariatric gastric bypass (n = 1), lymphoma (n = 1), gastrointestinal stromal tumor (n = 1), melanoma metastases (n = 1), posttraumatic jejunal perforation (n = 1), or ileal bladder reconstruction (n = 1). Multiple bowel surgeries had been performed on nine patients. The time between the abdominal operations and the imaging studies varied from 2 weeks to more than 12 years. In the 26 patients for whom the exact dates of operations were known, the mean and median time between the most recent surgery and the imaging studies were 49.4 and 32.2 months, respectively.

CT and CT Enteroclysis Examinations
The indications for the CT and CT enteroclysis examinations in the study patients were abdominal pain (n = 23), cancer follow-up (n = 4), nausea and vomiting (n = 7), anemia (n = 3), and diarrhea (n = 2). Some patients had more than one symptom over the period of follow-up. A total of 85 CT examinations and 24 CT enteroclysis studies performed on these patients were available for review.

CT studies were performed using Mx8000 (4-MDCT) or IDT (16-MDCT) CT scanners (Philips Medical Systems). At least one CT examination was performed on 22 patients; six patients underwent only CT enteroclysis examinations. Oral contrast medium was given in 83 examinations in 22 patients (500–750 mL of 2% meglumine diatrizoate [Gastrografin, Bracco]). IV contrast medium was given in 75 CT examinations in 20 patients (150 mL of iopamidol [Isovue-300, Bracco]). The effective slice width was 6.5 mm for the 4-MDCT scanner and 5 mm for the 16-MDCT scanner, with longitudinal reconstruction increments of 3.0 and 2.5 mm, respectively.

CT enteroclysis examinations were performed on 18 patients while they were under conscious sedation, with topical anesthesia applied to the nasopharynx. A nasoenteric tube (Maglinte tube, Cook) was placed in the descending duodenum under fluoroscopic guidance. CT enteroclysis was performed using techniques described previously [14].

Image Review
Two abdominal radiologists who knew that a blind pouch had been mentioned in at least one radiology report for each patient retrospectively evaluated all available CT (n = 85) and CT enteroclysis (n = 24) examinations. The images were reviewed initially to confirm the presence of a distended segment of small bowel consistent with a blind pouch. The size, position, and wall thickness of these lesions and the appearance of the proximal and distal small bowel and adjacent mesentery were recorded. The serial change in size was measured when follow-up studies were available. Note was made of any enteric complications. Low-grade obstruction was defined as a caliber change of 1–3 cm between proximal and distal segments on CT examination and transient obstruction to passage of infused contrast medium during the fluoroscopic portion of the CT enteroclysis examination. High-grade obstruction was defined as a caliber change of at least 3 cm between the proximal and distal segments. Nonobstructive adhesions were considered to be present if there were adherence of small bowel to anterior parietal peritoneum, kinking of bowel loops, mesenteric interloop bands, or tethering of loops during enteroclysis and a caliber change of less than 1 cm between proximal and distal loops.


Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Appearance of Blind Pouch
A total of 34 blind pouches were studied. One patient had three blind pouches, and four other patients had two blind pouches each. All pouches were in the small bowel. The mean orthogonal transverse diameters of all blind pouches were 5.6 x 6.2 cm. The maximum transverse diameters varied from 3.7 to 11.2 cm. All blind pouches were visible as focally distended segments of bowel. Surgical clips were visible adjacent to 29 of the 34 blind pouches (Fig. 2). Air and fluid (n = 22) or air and solid (fecal) material (n = 12) were the predominant contents of the blind pouches.



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  		Fig. 2 —Typical CT appearance of blind pouch, as shown on axial CT image of 51-year-old woman with small-bowel resection and anastomosis for gastrointestinal stromal tumor. Image shows ovoid loop of distended small bowel (black arrow), adjacent to surgical sutures (arrowheads). There is no dilatation of proximal bowel (white arrows).

 
One patient showed high-grade partial small-bowel obstruction with a mean luminal diameter of 4.3 cm proximal to the pouch and a diameter of 1.4 cm distal to the pouch. This patient subsequently underwent laparotomy with resection of the blind pouch, which was found to have an ulcer. In the other 27 patients, the mean luminal diameters were 1.5 and 1.6 cm proximal and distal, respectively, to the pouches.

The thickness of the wall of the blind pouch was less than 3 mm in all patients. Extraluminal fluid collections adjacent to blind pouches or pneumoperitoneum were not evident on any examinations. Edema of the adjacent mesentery was seen on at least one imaging examination in four patients. Two of these patients underwent subsequent resection of the blind pouches. Pathologic findings for these resected pouches were unremarkable. No patient had a mass in the blind pouch.



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  		Fig. 3A —Multiple blind pouches, as shown on axial CT images of 34-year-old woman with lymphoproliferative disorder after bone marrow transplantation for Fanconi anemia. She had multiple prior intestinal resections and anastomoses. Two blind pouches (arrows) are adjacent to surgical clips (arrowheads). CT scans 7 (A) and 13 (B) months after last surgical procedure show enlargement of blind pouch with time.

 



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  		Fig. 3B —Multiple blind pouches, as shown on axial CT images of 34-year-old woman with lymphoproliferative disorder after bone marrow transplantation for Fanconi anemia. She had multiple prior intestinal resections and anastomoses. Two blind pouches (arrows) are adjacent to surgical clips (arrowheads). CT scans 7 (A) and 13 (B) months after last surgical procedure show enlargement of blind pouch with time.

 
Change on Serial Studies
Twenty patients with a total of 26 blind pouches underwent serial CT or CT enteroclysis. The size and shape of the blind pouches varied with time. In general, blind pouches enlarged over several months, though this change usually was not progressive. Between consecutive scans the pouch size may increase, decrease, or remain the same; the exact size depended partly on the amount of air within the pouch. Seventeen of the blind pouches showed an increase of at least 25% in maximum transverse dimension between the earliest and last available studies (Figs. 3A and 3B). No unresected blind pouch reduced in transverse dimension by more than 25% between the first and last scans.

Ancillary Findings
Other postoperative findings were seen in 18 patients. The most common was nonobstructive adhesions (n = 11). Low-grade partial obstruction at sites other than the blind pouch was seen in six other patients. Ventral hernia was seen in two patients. No patient had an abscess, although in one patient the original report showed that the blind pouch had been mistaken for an abscess.

CT Versus CT Enteroclysis
The appearance of blind pouches on positive and neutral contrast CT enteroclysis did not significantly differ. Of the 20 patients with serial scans, 17 underwent both CT enteroclysis and CT (at least one each). On retrospective review, all blind pouches were equally visible with both examination techniques. However, the original CT reports mistook the blind pouches for diverticula (n = 2), abscesses (n = 1), or bowel obstructions (n = 4) on at least one of the serial CT examinations. Seventeen other reports mentioned the presence of a distended loop of small bowel of uncertain cause or significance.

CT enteroclysis was superior to CT in detecting ancillary findings. Only one of the nine cases of nonobstructive adhesions (two patients with adhesions underwent only CT enteroclysis, without comparison CT) and two of the five cases of low-grade small-bowel obstruction (one patient with low-grade obstruction underwent only CT enteroclysis) were identified prospectively on CT.

Surgical–Pathologic Correlation
The blind pouch was resected surgically in four patients, including the patient who presented with bowel obstruction. In this patient, resection of the blind pouch showed mucosal ulceration and congestion. In another patient, with iron deficiency anemia, suspected gastrointestinal bleeding from the blind pouch was considered the indication for surgery; pathologic examination of the resected specimen did not show ulceration, ischemia, or significant inflammation. In two patients, blind pouches were clinically thought to be the source of otherwise unexplained abdominal pain; pathologic examination did not show significant abnormality of the pouch.


Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The predominant CT finding of a blind pouch is a focally dilated loop of small bowel adjacent to surgical clips. Clips are visible if an automated gun stapler was used, as is the current surgical practice. These stainless-steel staples are small and may be difficult to detect, especially if relatively dense intestinal contrast medium is present within the pouch. It may be necessary to widen the CT viewing windows to examine the wall of a pouch for the presence of a staple line. In the past, hand sewing with sutures, usually of silk, was performed to ensure bowel integrity. These sutures are invisible on CT. The enlarged bowel segment may measure up to 11 cm. Unless the pouch is complicated, there is no proximal bowel dilatation, bowel-wall thickening, or significant mesenteric stranding. There is usually a history of enteric resection with anastomosis, though this may not be elicited if the surgery was performed several years earlier. It is useful to obtain an operative history because a blind pouch without a visible adjacent staple line is radiologically indistinguishable from an intestinal diverticulum. In the first few months after surgery, growth of the blind pouch is likely to be seen on serial CT examinations. An air–fluid level or fecal matter may be seen within this loop of bowel. Because a blind pouch is associated with prior surgery, other postsurgical complications may be seen. In our study, the most common of these was adhesions without obstruction (n = 11) or with partial low-grade obstruction (n = 6). In all patients except one, the obstruction was remote from the blind pouch. In one patient, the blind pouch was thought to be the site of obstruction and was subsequently resected. More immediate postoperative complications such as abscess were not seen in our patients, probably because blind pouch formation was a late postoperative complication.

The development of a blind pouch is related to the type of enteric anastomosis. Though pouches may occur with end-to-side anastomosis, they are much more common with side-to-side anastomosis [3–5, 11]. A blind pouch does not occur after end-to-end anastomosis. The incidence of blind pouch could not be elicited from a literature search. In our experience of daily reporting several postoperative CT studies, the incidence of this entity is likely to be low.

Identification of a blind pouch is important for two reasons. First, the entity may be misdiagnosed if the radiologist is unaware of its imaging appearances. Differential diagnosis includes abscess and bowel obstruction. Lack of inflammatory changes or proximal bowel dilatation should favor diagnosis of a blind pouch. A small-bowel diverticulum may be difficult to distinguish on CT. Blind pouches are solitary unless multiple anastomoses have been performed (Figs. 3A and 3B). An adjacent line of surgical clips helps to differentiate a blind pouch from a diverticulum. Original CT reports of the examinations we reviewed showed that blind pouches had been mistaken for these conditions. In some cases, the radiologist detected the dilated loop of bowel but was unable to ascribe its cause or significance.

Second, blind pouches are not always clinically irrelevant incidental findings. In addition to bacterial overgrowth, multiple complications of this condition have been described. Enteroliths have been noted in longstanding blind pouches [8, 10] and may be a source of small-bowel obstruction [2]. Ulceration and bleeding have been reported to occur within blind pouches, sometimes several years after surgery [1, 12, 15]. Vitamin B12 and iron-deficiency anemia can occur [1]. Rarely, tumors may develop in a blind pouch [13]. However, there are no data suggesting that tumors are more prevalent in patients with blind pouches than in the general population. We saw such a complication in only one patient, who had a high-grade small-bowel obstruction. CT is not sensitive in detecting mucosal ulceration. Small enteroliths may be missed when positive oral contrast medium is used. However, we have seen patients in whom enteroliths or ulceration of blind pouches had been shown on upper gastrointestinal contrast studies. If symptomatic, blind pouches may be surgically excised—a procedure that can be performed laparoscopically [6]. In our series, four of the 28 patients underwent resection of blind pouches.

Our study had the limitations of a retrospective survey, including bias in case selection and the lack of a masked comparison between CT and CT enteroclysis. A prospective study in a reasonable time frame is impracticable given the relative rarity of this condition. The number of cases in our review is small, and we believe that the lack of awareness by radiologists may have contributed to underreporting of this condition. Surgical proof of a blind pouch was available in only four patients. However, we are confident that the CT appearances are clear enough for this diagnosis to be made without surgical confirmation in most cases. We believe that knowledge of the CT findings for blind pouches may help in identifying this potential source of postoperative symptoms.


References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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This Article
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