AJR ARRS: Your Link to CME
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 QUICK SEARCH:   [advanced]


     


This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sandrasegaran, K.
Right arrow Articles by Maglinte, D. T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sandrasegaran, K.
Right arrow Articles by Maglinte, D. T.
Social Bookmarking
 Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?
AJR 2005; 184:475-480
© American Roentgen Ray Society


Original Report

Distinguishing Gelatin Bioabsorbable Sponge and Postoperative Abdominal Abscess on CT

Kumaresan Sandrasegaran1, Chandana Lall1, Arumugam Rajesh2 and Dean T. Maglinte1

1 Department of Radiology, Indiana University School of Medicine, 550 N University Blvd., Indianapolis, IN 46202.
2 Department of Radiology, University Hospitals of Leicester NHS Trust, Leicester General Hospital, Leicester, United Kingdom LE5 4PW.

Received January 20, 2004; accepted after revision May 17, 2004.

 
Address correspondence to K. Sandrasegaran (ksandras{at}iupui.edu).


Abstract
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
 
OBJECTIVE. The objective of our study was to differentiate the CT findings of gelatin bioabsorbable sponges used as hemostatic agents from postoperative abdominal abscess.

CONCLUSION. Gelatin absorbable sponge may mimic a postoperative abscess on CT. Findings that may help differentiate the hemostatic agent from abscess include linear arrangement of tightly packed gas bubbles, fixed position of gas bubbles on subsequent examinations, shape, lack of air–fluid level, and lack of enhancing wall.


Introduction
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
 
With the increasing number of surgical innovations, the radiologist is often faced with postoperative CT examinations for which the findings can be difficult to interpret. To differentiate between postoperative complications and the expected postsurgical appearance, the radiologist must be aware of the surgical technique. Hemostatic agents have been used for many years to help control intraoperative bleeding. These bioabsorbable agents are intentionally placed in the surgical field, unlike nondegradable sponges that may be left inadvertently during surgery. In most cases, the bioabsorbable agents blend with tissue in the surgical bed and are not differentiated from postsurgical scar on CT scans. However, we have seen several cases in which bioabsorbable gelatin sponge (Gelfoam, Pharmacia) used for intraoperative hemostasis was misdiagnosed as postoperative abscess on CT. To our knowledge, the initial and follow-up CT appearances of gelatin bioabsorbable sponge have not been addressed in the radiology literature. We present the CT findings in 18 patients in whom this hemostatic agent was used in a variety of surgical procedures.


Materials and Methods
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
 
A retrospective search of reports of abdominal CT examinations performed at our institution between December 2002 and September 2003 revealed 23 patients with suspected presence of gas-containing foreign body in the surgical field. The surgical notes mentioned the use of gelatin absorbable sponge during operation in 15 of these patients. In the operative reports for two patients who had undergone liver transplantation, the use of hemostatic agents was not mentioned. The operating surgeon confirmed that gelatin bioabsorbable sponge was routinely used for securing hemostasis. In one patient, who was transferred from an outside institution after undergoing hysterectomy for cervical cancer, the operative notes were not available. However, the admitting records made note of considerable problems with intraoperative hemorrhage in this patient. These 18 patients formed the study group. Five patients were excluded from the study because we were unable to obtain supportive data for the intraoperative use of hemostatic agents.

CT studies were performed using a 4-MDCT scanner (Mx8000, Philips Imaging), a 16-MDCT scanner (IDT, Philips Imaging), or a 2-slice scanner (CT Twin, Philips [formerly Elscint]). Contrast medium was given orally on the initial CT examination in 17 patients (500–750 mL of 2% diatrizoate meglumine, Gastrografin, Bracco). Contrast medium was given IV to all patients (150 mL of iopamidol, Isovue-300, Bracco). The effective slice width was 6.5 mm for the 2-slice scanner and 5 mm for the MDCT scanners with longitudinal reconstructions of 3 and 2.5 mm, respectively.

The CT images were reviewed by two abdominal radiologists to confirm the presence of low-density material at the operative bed (density, ≤–100 H). The size, shape, Hounsfield density, homogeneity, presence of air–fluid levels, and appearance of surrounding fat were recorded by the radiologists blinded to the postoperative course of the patients. Soft-copy images were viewed on an MxView Station (Philips Imaging). The clinical findings in all patients were reviewed from the hospital information system. Patient demographics, type of surgery, date of operation, and postsurgical progress were recorded.


Results
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
 
The study group was composed of seven men and 11 women with mean age of 56.2 years (range, 45–84 years). The types of surgery performed in these patients are given in Table 1. The initial postoperative CT examinations were performed between 1 and 29 days after surgery (mean, 9.4 days) and were performed to assess for postoperative complications. Eleven patients underwent a total of 16 follow-up CT examinations performed 4–156 days after surgery. Thirty-four initial and follow-up CT examinations were reviewed.


View this table:
[in this window]
[in a new window]

 
TABLE 1 Types of Surgery Performed

 

On the initial CT examinations, the size of the gelatin sponge ranged from 1.5 to 7.4 cm (mean, 3.2 cm). The density of the sponges measured from –104 to –458 H, with a mean of –245 H. The overall density of gelatin sponges was between that of gas and fluid. The shape of the sponges was variable. In eight patients, the sponge appeared predominantly polygonal, principally as rectangular strips (Fig. 1A, 1B, 1C). In 10 patients, the sponge was predominantly rounded (Fig. 2A, 2B). In all patients, the gas bubbles within the sponge were tightly packed and were not dispersed randomly (Fig. 3). No intervening fluid or soft-tissue density was present between gas pockets. The gas pockets within the gelatin sponge were uniform in size without discrete dominant bubbles.



View larger version (140K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 1A. CT images show gelatin bioabsorbable sponge. Axial CT images of 45-year-old woman who had cystectomy and creation of Hartmann's pouch show lower pelvis. These images, which were obtained using soft-tissue (A) and lung (B) window settings, show gas-filled structure with stripelike configuration (arrow), which is consistent with gelatin bioabsorbable sponge.

 


View larger version (119K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 1B. CT images show gelatin bioabsorbable sponge. Axial CT images of 45-year-old woman who had cystectomy and creation of Hartmann's pouch show lower pelvis. These images, which were obtained using soft-tissue (A) and lung (B) window settings, show gas-filled structure with stripelike configuration (arrow), which is consistent with gelatin bioabsorbable sponge.

 


View larger version (134K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 1C. CT images show gelatin bioabsorbable sponge. Axial CT image of mid abdomen of 55-year-old man after undergoing orthotopic liver transplantation shows typical linear stripelike appearance of gelatin bioabsorbable sponge (straight arrow). High-attenuation fluid collection (curved arrow) surrounds sponge. Patient did not have clinical or laboratory evidence of infection. Appearances are suggestive of intraoperative hematoma.

 


View larger version (120K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 2A. 51-year-old man who underwent partial right nephrectomy for renal carcinoma. CT images obtained using soft-tissue (A) and lung (B) window settings show rounded gas pockets in gelatin bioabsorbable sponge (arrow). Note that Gelfoam (Pharmacia) has Hounsfield density between that of fat and air.

 


View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 2B. 51-year-old man who underwent partial right nephrectomy for renal carcinoma. CT images obtained using soft-tissue (A) and lung (B) window settings show rounded gas pockets in gelatin bioabsorbable sponge (arrow). Note that Gelfoam (Pharmacia) has Hounsfield density between that of fat and air.

 


View larger version (138K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 3. 47-year-old woman who underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy for infarcted myoma. CT image depicts fluid collection with enhancing rim (curved arrow), which is suggestive of abscess. Patient had fever, and purulent material subsequently was aspirated from collection. On anterior aspect of abscess is a gelatin bioabsorbable sponge (straight arrow). Unlike gas bubbles in abscess, which are discrete and rounded (arrowhead), gas pockets within gelatin bioabsorbable sponge are tightly packed.

 

Five patients in the series had clinical and CT evidence of infection at the operative site. In four of these five patients, a drainage catheter was placed and purulent material was aspirated. These patients showed the presence of a well-defined low-density region, the hemostatic sponge, surrounded by fluid (Fig. 3). One of these five patients had a low-grade fever (up to 39.5°C), and hemorrhagic fluid was detected at aspiration. Results for the fluid and blood cultures were negative in this patient.

A gelatin sponge was visible on all follow-up CT scans obtained less than 38 days after surgery. The sponge was not seen on scans obtained 56, 74, and 156 days after surgery. In all patients with serial CT examinations, the gelatin sponge was smaller on subsequent scans. This change is best illustrated in a patient who had three CT examinations at postoperative day 6, 15, and 22 (Fig. 4A, 4B, 4C). The gas pockets in the gelatin sponge maintained their close spatial arrangement without dispersion on subsequent scans (Fig. 5A, 5B). This appearance was disparate from that of abscesses in which discrete gas bubbles were seen in different and random positions relative to each other on follow-up examinations.



View larger version (133K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 4A. 45-year-old woman who underwent cystectomy. Axial CT images of lower pelvis obtained on postoperative days 5 (A), 15 (B), and 26 (C) show gradual resorption of gelatin bioabsorbable sponge (arrow).

 


View larger version (138K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 4B. 45-year-old woman who underwent cystectomy. Axial CT images of lower pelvis obtained on postoperative days 5 (A), 15 (B), and 26 (C) show gradual resorption of gelatin bioabsorbable sponge (arrow).

 


View larger version (136K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 4C. 45-year-old woman who underwent cystectomy. Axial CT images of lower pelvis obtained on postoperative days 5 (A), 15 (B), and 26 (C) show gradual resorption of gelatin bioabsorbable sponge (arrow).

 


View larger version (132K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 5A. 52-year-old man who underwent partial left nephrectomy. Serial CT scans show reabsorption of gelatin bioabsorbable sponge (arrows). Despite resorption, tightly packed gas configuration is maintained without bubbles dispersing.

 


View larger version (127K):
[in this window]
[in a new window]
[as a PowerPoint slide]
 
Fig. 5B. 52-year-old man who underwent partial left nephrectomy. Serial CT scans show reabsorption of gelatin bioabsorbable sponge (arrows). Despite resorption, tightly packed gas configuration is maintained without bubbles dispersing.

 


Discussion
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
 
Bioabsorbable hemostatic agents are commonly used to stop intraoperative bleeding that is not controlled by cautery or suture ligation. Types of surgery in which gelatin absorbable sponge is used in our institution include vascular surgery, transplantation, hysterectomy, and partial nephrectomy. Gelatin bioabsorbable sponge also has been used extensively as an intravascular embolization agent. In this article, we deal with surgically placed and not catheter-injected gelatin bioabsorbable sponge. The four commonly used hemostatic agents are collagen sponges, gelatin sponge (Gelfoam), oxidized regenerated cellulose (Surgicel, Johnson and Johnson Medical), and microfibrillar collagen [1].

Gelatin bioabsorbable sponge is a purified porcine skin product that is water-insoluble. It aids in rapid hemostasis by forming an artificial clot and by its physical property of providing a mechanical matrix for platelet aggregation. Gelatin absorbable sponge contains numerous gas pockets that are not displaced immediately by interstitial body fluids. The presence of a gas-containing structure on early postoperative scans raises the possibility of abscess. It is interesting to note that researchers of original CT studies mentioned the presence of a gas-containing structure consistent with an abscess in 27 of the 34 scans. In 14 cases, the possibility of hemostatic agent was raised; such cases were the more recent studies when our radiologists became more aware of the CT appearances of gelatin sponge.

Our results show that it is possible to differentiate between these entities using CT. Gas pockets in gelatin sponge are packed tightly and are not discrete. They often are lined up in a linear fashion. Air–fluid levels, which typify abscess, usually are not seen in gelatin sponge without coexisting infection. Rim enhancement of the gelatin sponge generally is not seen in the absence of coexisting abscess, although rare exceptions occur. In one of 14 patients who did not clinically exhibit any signs of infection, the site of gelatin bioabsorbable sponge packing showed rim enhancement. The CT examination was performed 12 days after surgery. It is not clear if the enhancement was due to a foreign-body reaction or if there was subclinical infection.

Gelatin sponge usually is cut in geometric shapes to be placed against the bleeding surface during surgery; its shape may help differentiate it from an abscess. Follow-up CT examinations can reveal useful information. The gas bubbles in gelatin bioabsorbable sponge maintain their spatial position, which would be unusual in an abscess. CT performed for up to 38 days after surgery shows the sponge as a predominantly gas-containing structure. Over time, blood and interstitial fluid penetrate the sponge and a more homogeneous appearance of soft-tissue rather than gas-containing structure is seen.

The presence of gelatin sponge does not preclude an abscess, and the two can coexist. As seen in some of our cases, a well-defined geometric-shaped gas-containing structure within a fluid collection may be seen. Other CT findings of abscess such as scattered discrete large gas bubbles, rim enhancement, and air–fluid levels may be seen in this collection.

Surgical sponges are made of materials such as cellulose that do not become oxidized. They are nonabsorbable and must be removed from the surgical field [2]. In contrast, gelatin sponges are absorbed eventually and are left intentionally in the surgical field after surgery to continue to function as a hemostatic agent. The mechanism of absorption is not clear. Macrophages have been implicated in the absorption of other bioabsorbable hemostatic agents [3]. Of the eight patients for whom we had serial CT examinations, gelatin bioabsorbable sponge was seen as an identifiable structure on CT for up to 38 days after surgery. Our review shows that eventually gelatin sponges become resorbed at a reasonably rapid pace after the first week of surgery.

The use of hemostatic gelatin sponge is not without complications. The incidence of infection, which may be due to presence of a foreign body or superinfection of hemorrhage, is increased. In our series, 22.2% of the patients had superadded infection. Foreign-body granulomas can occur with excess use of gelatin sponges, particularly in the cranial cavity [46]. Neurologic dysfunction including quadriparesis may be caused by the use of these agents in the spinal canal [7]. Toxic shock syndrome has been reported after nasal surgery in which bioabsorbable gelatin sponges were used [8, 9].

A literature review reveals sparse information about the CT appearances of these hemostatic agents. Two groups have reviewed the CT examinations of a total of six patients [10, 11] who had hemostasis achieved with the use of oxidized cellulose (Surgicel) during neurologic and abdominal surgery. Like our findings, their findings suggest that linear arrangement of gas bubbles that maintain their position on subsequent scans should raise the possibility of hemostatic agents in contradistinction from abscess. It is probable that the CT findings seen with gelatin absorbable sponges are common to other hemostatic bioabsorbable agents. In a case report, researchers suggested the use of indium-labeled WBC scanning to differentiate a sterile mediastinal air collection associated with the use of a gelatin bioabsorbable sponge from abscess in a patient after aortic surgery [12]. However, careful evaluation of the CT findings can help differentiate gelatin sponge from abscess in most cases. We believe that such an analysis and a review of operative notes or consultation with the referring surgical team could prevent unnecessary antibiotic therapy or drainage catheter placement.

We are aware of the limitations of our study. The study was retrospective and depended on postoperative CT examinations reporting a foreign body containing gas. Many patients with the appropriate CT examinations probably were not included in this series. It is our experience that the gelatin sponge frequently is mistaken for abscess. Indeed, in many patients, the CT images from a second or third examination raised the possibility of gelatin sponge when the finding had been overlooked or misinterpreted on the initial CT examination. Consequently, the number of patients in this series was modest. Only a proportion of patients in our series had serial CT examinations to assess the natural history of gelatin sponge; it would not have been ethical to perform additional examinations without clinical need. Nevertheless, we were able to describe the CT features of gelatin absorbable sponge and determine criteria that may help in differentiation from postoperative abscess.


References
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
 

  1. Wagner WR, Pachence JM, Ristich J, Johnson PC. Comparative in vitro analysis of topical hemostatic agents. J Surg Res1996; 66:100 –108[Medline]
  2. Kokubo T, Itai Y, Ohtomo K, Yoshikawa K, Iio M, Atomi Y. Retained surgical sponges: CT and US appearance. Radiology1987; 165:415 –418[Abstract/Free Full Text]
  3. Pierce A, Wilson D, Wiebkin O. Surgicel: macrophage processing of the fibrous component. Int J Oral Maxillofac Surg1987; 16:338 –345[Medline]
  4. Knowlson GT. Gel-foam granuloma in the brain. J Neurol Neurosurg Psychiatry 1974;37:971 –973[Abstract/Free Full Text]
  5. Kothbauer KF, Jallo GI, Siffert J, Jimenez E, Allen JC, Epstein FJ. Foreign body reaction to hemostatic materials mimicking recurrent brain tumor: report of three cases. J Neurosurg2001; 95:503 –506[Medline]
  6. Guerin C, Heffez DS. Inflammatory intracranial mass lesion: an unusual complication resulting from the use of Gelfoam. Neurosurgery1990; 26:856 –859[Medline]
  7. Alander DH, Stauffer ES. Gelfoam-induced acute quadriparesis after cervical decompression and fusion. Spine1995; 20:970 –971[Medline]
  8. Kotlarz JP, Crane JK. Toxic shock syndrome after mastoidectomy. Otolaryngol Head Neck Surg1998; 118:701 –702[Medline]
  9. Younis RT, Gross CW, Lazar RH. Toxic shock syndrome following functional endonasal sinus surgery: a case report. Head Neck 1991;13:247 –248[Medline]
  10. Turley BR, Taupmann RE, Johnson PL. Postoperative abscess mimicked by Surgicel. Abdom Imaging1994; 19:345 –346[Medline]
  11. Young ST, Paulson EK, McCann RL, Baker ME. Appearance of oxidized cellulose (Surgicel) on postoperative CT scans: similarity to postoperative abscess. AJR1993; 160:275 –277[Abstract/Free Full Text]
  12. Black CM, Rockoff SD, Alyono D. Sterile mediastinal gas mimicking abscess in aortic aneurysm repair. Chest1992; 102:1911 –1913[Abstract/Free Full Text]

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
RadioGraphicsHome page
G. M. Israel, E. Hecht, and M. A. Bosniak
CT and MR Imaging of Complications of Partial Nephrectomy
RadioGraphics, September 1, 2006; 26(5): 1419 - 1429.
[Abstract] [Full Text] [PDF]


This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sandrasegaran, K.
Right arrow Articles by Maglinte, D. T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sandrasegaran, K.
Right arrow Articles by Maglinte, D. T.
Social Bookmarking
 Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS