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DOI:10.2214/AJR.04.1791
AJR 2006; 186:535-538
© American Roentgen Ray Society

Case Report

Inverted Appendiceal Stumps Simulating Large Pedunculated Polyps on Screening CT Colonography

Tyler M. Prout1, Andrew J. Taylor1 and Perry J. Pickhardt1

1 All authors: Department of Radiology, University of Wisconsin Medical School, E3/311 Clinical Science Center, 600 Highland Ave., Madison, WI 53792-3252.

Received November 18, 2004; accepted after revision January 14, 2005.

 
Address correspondence to P. J. Pickhardt.

Keywords: appendix • colon • colonography • CT • screening


Introduction
Top
 Introduction
Case Reports
 Discussion
 References
 
The finding of a polypoid or mass lesion at the cecal tip after an appendectomy has been previously described at optical colonoscopy and barium enema examination. We present two cases where an appendiceal stump simulated a large pedunculated polyp in asymptomatic adults undergoing CT colonography (CTC) for screening. In a patient with a prior appendectomy, the specific location and appearance of this entity at CTC may be sufficient for diagnosis, but the possibility of a significant neoplasm may be difficult to exclude in some cases.


Case Reports
Top
 Introduction
 Case Reports
Discussion
 References
 
A 63-year-old asymptomatic woman was referred to our CTC program for routine colorectal screening. Surgical history was significant only for remote appendectomy. The day before the examination, she underwent our standard CTC preparation of oral sodium phosphate (45 mL), 2% barium sulfate suspension (250 mL), and water-soluble iodinated contrast material (diatrizoate, 60 mL). Colonic distention was achieved by automated CO2 delivery (PROTOCO2L, E-Z-EM). Supine and prone CT images were obtained on an MDCT scanner (LightSpeed Ultra, GE Healthcare) using an 8 x 1.25 detector configuration, 1-mm reconstruction interval, 120 kVp, and 50 mAs. The study was interpreted by an experienced gastrointestinal radiologist using commercial CTC software (V3D Colon, Viatronix). At our institution, a biphasic interpretive approach, consisting of primary 3D polyp detection combined with secondary 2D detection and correlation of suspicious 3D findings, is used.

The CTC examination revealed a discrete 10-mm pedunculated polypoid lesion at the medial base of the cecum (Figs. 1A, 1B, and 1C). No other colorectal lesions were identified. Despite the location of the lesion and history of previous appendectomy, a true neoplastic polyp could not be confidently excluded. Therefore, the patient went on to same-day optical colonoscopy for potential polypectomy, which confirmed the cecal lesion and showed no other abnormality. The endoscopic appearance of the polypoid cecal lesion was thought to be most compatible with an inverted appendiceal stump (Fig. 1D). Colonoscopic biopsies were taken, which revealed benign colonic mucosa with underlying lymphoid tissue.


Figure 1
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  		Fig. 1A —Inverted appendiceal stump in 63-year-old asymptomatic woman referred to CT colonography (CTC) for routine colorectal cancer screening. Three-dimensional endoluminal view from prone CTC data set shows discrete 10-mm pedunculated polypoid lesion located at medial aspect of cecal tip.

 

Figure 2
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  		Fig. 1B —Inverted appendiceal stump in 63-year-old asymptomatic woman referred to CT colonography (CTC) for routine colorectal cancer screening. Prone transverse (B) and coronal (C) 2D images from CTC confirm pedunculated lesion (arrow) detected on 3D view and show its soft-tissue composition. Lesion is located at or near appendectomy site, but this does not completely exclude possibility of neoplasm.

 

Figure 3
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  		Fig. 1C —Inverted appendiceal stump in 63-year-old asymptomatic woman referred to CT colonography (CTC) for routine colorectal cancer screening. Prone transverse (B) and coronal (C) 2D images from CTC confirm pedunculated lesion (arrow) detected on 3D view and show its soft-tissue composition. Lesion is located at or near appendectomy site, but this does not completely exclude possibility of neoplasm.

 

Figure 4
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  		Fig. 1D —Inverted appendiceal stump in 63-year-old asymptomatic woman referred to CT colonography (CTC) for routine colorectal cancer screening. Digital photograph from optical colonoscopy performed same day as CTC shows same cecal lesion. Given endoscopic appearance, an inverted appendiceal stump was favored, which was further supported by biopsies that were negative for neoplasm.

 
Our second case involved a 58-year-old asymptomatic woman with a history of appendectomy. On a routine screening, CTC showed a large pedunculated polypoid lesion in the cecum (Figs. 2A, 2B, and 2C). In addition to being in the expected location of the appendiceal region, the lesion showed a subtle focus of internal fat attenuation on the 2D images (Fig. 2B). An inverted stump was prospectively suggested, but the patient still went on to same-day optical colonoscopy because a significant neoplasm could not be absolutely excluded. The polyp was confirmed and snared at endoscopy and the polyp site was cauterized. Although not suspected at optical colonoscopy, at pathologic evaluation the lesion was found to be an appendiceal stump.


Figure 5
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  		Fig. 2A —Inverted appendiceal stump in 58-year-old asymptomatic woman referred for screening CT colonography (CTC). Three-dimensional endoluminal view from CTC shows a large pedunculated cecal polyp arising near expected location of appendiceal orifice.

 

Figure 6
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  		Fig. 2B —Inverted appendiceal stump in 58-year-old asymptomatic woman referred for screening CT colonography (CTC). Transverse 2D image with soft-tissue window settings shows a punctate focus of apparent fat attenuation within polyp head (arrow). Although low-dose technique precluded confident exclusion of an adenomatous polyp based on this finding, possibility of inverted appendiceal stump was suggested.

 

Figure 7
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  		Fig. 2C —Inverted appendiceal stump in 58-year-old asymptomatic woman referred for screening CT colonography (CTC). Digital photograph from optical colonoscopy performed same day as CTC shows same cecal lesion, which was thought to represent a true polyp and removed by snare with cautery. Inverted appendiceal stump was confirmed at pathologic evaluation.

 

Discussion
Top
 Introduction
 Case Reports
 Discussion
References
 
Historically, the technique of inversion-ligation appendectomy was used by some surgeons to theoretically reduce the risk of peritoneal contamination in the setting of acute appendicitis [1-4]. This technique has also been used for incidental appendectomy performed during laparotomy for unrelated problems. The resultant appendiceal stump usually necroses and sloughs into the colonic lumen after several days, but remnant tissue may persist in some patients. A more recent review of this surgical technique concluded that the additional step of stump inversion is not necessary [1]. At the present time, the inversion-ligation technique is seldom used during an open procedure and is not used in the laparoscopic approach. Nevertheless, many adults currently presenting for CTC screening have undergone appendectomy decades earlier when this procedure was common practice.

Intraluminal projections simulating a cecal neoplasm after appendectomy are well known, both in the gastroenterology and radiology literature [2-4]. The most common appearance of the inverted appendiceal stump consists of a raised prominence at the cecal tip. In less prominent cases, correlating this finding with the patient's history of appendectomy allows confident diagnosis at CTC. The postoperative appearance at the appendiceal orifice, however, can be quite variable. The appendiceal stump may be enlarged by postoperative hemorrhage or by stump appendicitis. The entire cecal tip may also become flattened as a result of surgery in this area.

On barium enema examination, prominent postappendectomy filling defects may be difficult to distinguish from true neoplasms. In a series of barium enemas in six patients, the diagnosis of an appendiceal stump was made prospectively in only two cases, both of which involved complete inversion of the appendix [3]. At optical colonoscopy, the typical appearance of an inverted appendix or appendiceal stump consists of an oblong mass, which, in one colonoscopic series, was seen in 1.5% of cases [2].

Colorectal neoplasms, particularly advanced adenomas, are the primary target for colorectal cancer screening, but a wide array of additional entities can present as a polypoid lesion at CTC [5]. In addition to mucosal-based neoplasms, other broad categories include nonneoplastic mucosal lesions, submucosal lesions, impression from extrinsic lesions, and a variety of CTC pitfalls and artifacts [5]. Appendiceal causes, such as a mucocele or intussusception, represent a special subset of extrinsic lesions and make this a more difficult area of evaluation at CTC.

When a focal lesion is identified near the cecal tip at CTC, it is important to first identify the appendix or confirm its absence. The 2D multiplanar reformatted images are indispensable for this task. Correlation with surgical history is important; we obtain this information in all patients undergoing CTC evaluation as part of the routine intake and scheduling process. We do not routinely administer IV contrast material for screening CTC because we believe that any incremental benefit would likely be offset by the added risks, expense, and time. Furthermore, many of the polypoid lesions that can mimic mucosal-based neoplasms (appendiceal stumps included) show at least some contrast enhancement, making distinction difficult.

In the two cases presented here, despite the characteristic location of the lesion and the surgical history of the patient, the large, pedunculated appearance of the appendiceal stump caused enough concern about the possibility of a significant neoplasm that optical colonoscopy was recommended. If the lesions had measured less than 10 mm, noninvasive CTC surveillance would have been a reasonable option under our institutional review board-approved protocol [6], thus avoiding the need for immediate optical colonoscopy.

In conclusion, although the specific location and appearance of an appendiceal stump generally allow its recognition at CTC, in some cases the possibility of a significant neoplasm cannot be completely excluded.


References
Top
 Introduction
 Case Reports
 Discussion
 References
 

  1. Engstrom L, Fenyo G. Appendicectomy: assessment of stump invagination versus simple ligation—a prospective, randomized trial. Br J Surg 1985;72 : 971-972[Medline]
  2. Jarvensivu P, Lehtola J, Karvonen AL, Rinne A, Suramo I. Colonoscopic appearance of the remnant of the appendix after total inversion. Endoscopy 1982;14 : 66-68[Medline]
  3. Myllarniemi H, Perttala Y, Peltokallio P. Tumor-like lesions of the cecum following inversion of the appendix. Am J Dig Dis 1974; 19:547 -556[Medline]
  4. Vaughn AM, Widran J. Inverted appendical stump simulating cancer of the cecum. JAMA 1954;154 : 996-997
  5. Pickhardt PJ. Differential diagnosis of polypoid lesions seen at CT colonography (virtual colonoscopy). RadioGraphics2004; 24:1535 -1559[Abstract/Free Full Text]
  6. Pickhardt PJ, Taylor AJ, Johnson GL, et al. Building a CT colonography program: necessary ingredients for reimbursement and clinical success. Radiology 2005;235 : 17-20[Free Full Text]

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