Retained Fibrin Sheaths: Chest Computed Tomography Findings and Clinical Associations

Krausz, David J. MD*,†; Fisher, Jessica S. MD*; Rosen, Galia MD; Haramati, Linda B. MD, MS*,§; Jain, Vineet R. MD*; Burton, William B. PhD; Godelman, Alla MD*; Levsky, Jeffrey M. MD, PhD*; Taragin, Benjamin H. MD*; Cynamon, Jacob MD*; Aviram, Galit MD

Journal of Thoracic Imaging:
doi: 10.1097/RTI.0b013e318299ff22
Original Articles

Purpose: Fibrin sheaths may develop around long-term indwelling central venous catheters (CVCs) and remain in place after the catheters are removed. We evaluated the prevalence, computed tomographic (CT) appearance, and clinical associations of retained fibrin sheaths after CVC removal.

Materials and Methods: We retrospectively identified 147 adults (77 men and 70 women; mean age 58 y) who underwent CT after CVC removal. The prevalence of fibrin sheath remnants was calculated. Bivariate and multivariate analyses were performed to assess for associations between sheath remnants and underlying diagnoses leading to CVC placement; patients’ age and sex; venous stenosis, occlusion, and collaterals; CVC infection; and pulmonary embolism.

Results: Retained fibrin sheaths were present in 13.6% (20/147) of cases, of which 45% (9/20) were calcified. Bivariate analysis revealed sheath remnants to be more common in women than in men [23% (16/70) vs. 5% (4/77), P=0.0018] and to be more commonly associated with venous occlusion and collaterals [30% (6/20) vs. 5% (6/127), P=0.0001 and 30% (6/20) vs. 6% (7/127), P=0.0003, respectively]. Other variables were not associated. Multivariate analysis confirmed the relationship between fibrin sheaths and both female sex (P=0.005) and venous occlusion (P=0.01).

Conclusions: Retained fibrin sheaths were seen on CT in a substantial minority of patients after CVC removal; nearly half of them were calcified. They were more common in women and associated with venous occlusion.

Author Information

Departments of *Radiology


Family and Social Medicine, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx

Department of Radiology, Staten Island University Hospital, Staten Island, NY

Department of Radiology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel

G.A. is a consultant at Activiews Ltd and Algotec - a Carestream Company. J.C. is a consultant at Foresight imaging, lectures for Genentech and receives royalties from angiodynamics; his daughter is employed by Delcath. L.B.H.'s husband is a board member of Orthospace Kryon and Bioprotect. The remaining authors declare no conflicts of interest.

Reprints: Linda B. Haramati, MD, MS, Department of Radiology and Medicine, Albert Einstein College of Medicine, Montefiore Medical Center, 111 East 210 Street, Bronx, NY 10467 (e-mail:

Article Outline

Fibrin sheaths form around long-term indwelling central venous catheters (CVCs) with a reported frequency of 42% to 100%.1–3 The pathogenesis is related to a dynamic process of cellular and noncellular deposition, which occurs within 7 days of long-term indwelling CVC implantation.4,5 This process is initiated by endothelial damage and involves a complex series of events including thrombus formation, smooth muscle activation, collagen deposition, and sometimes calcification.6 Histologic investigations describe several appearances, including a mesh-like thrombus that bridges the vein wall and catheter, a sleeve-related thrombus found on the distal aspect of the catheter, and a mural thrombus on the vein wall.4,5

During catheter removal, these sheaths, or sleeves, may remain within the vein.7,8 Histologic analysis reveals the retained sheaths to be adherent to the venous wall with the presence of additional clots intraluminally.9 Venographic studies demonstrate sleeve thrombosis in a majority of cases and mural veno-occlusive thrombosis in a minority.3

Fibrin sheaths can lead to complications in catheter function,10,11 and remnants may be associated with complications arising from long-term indwelling CVCs, including venous stenosis or occlusion, pulmonary embolism, and infection.12–17 The computed tomographic (CT) appearance of a retained sheath was described in a case report as a cord-like hypodense filling defect forming a ghost image of the removed indwelling catheter.18 As there are, to our knowledge, no serial studies describing fibrin sheath remnants on CT, there is a low awareness of their CT appearances. This has led to misinterpretation of CT findings, resulting in unnecessary intervention. For example, several case reports describe instances in which fibrin sheaths were misdiagnosed as retained catheter fragments.7,8,19 In another report, an infant underwent surgical exploration of a presumed foreign body, which was later found to be a calcified fibrin sheath.20 The calcified nature of the fibrin sheath was singled out as a misleading factor.

We conducted the present study to evaluate the prevalence of retained fibrin sheaths on chest CT in adults who had undergone removal of a long-term indwelling CVC in order to describe their CT appearance and identify the patient-specific characteristics and complications that may be associated with retained fibrin sheaths.

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This retrospective study was performed at 2 academic medical centers, 1 in the United States and 1 in Israel, and was approved by the Institutional Review Boards at both institutions. Informed consent was not required.

We retrospectively identified 147 adults who underwent chest CT after removal of a long-term indwelling CVC between January 2008 and July 2009. Only patients with long-term indwelling CVCs including tunneled catheters, implantable ports, and peripherally inserted central catheters (PICCs) were studied. Patients with long-term indwelling CVCs in place at the time of CT were included in the study population provided they had undergone prior removal of at least 1 long-term indwelling CVC. Patients with only short-term central lines such as small-diameter multilumen catheters typically used in the intensive care unit setting or with long-term catheters that had been inserted for <7 days were excluded.

Patients at 1 institution were identified using Clinical Looking Glass, a software application developed to evaluate health-care quality, effectiveness, and efficiency using clinical and administrative data sets. Seventy-two patients (31 men and 41 women; mean age 62 y) were selected by consecutive medical record numbers. A manual chart review was then conducted to ensure that all inclusion criteria were met. Indwelling catheter duration was verified to ensure it exceeded 7 days by reviewing sequential radiographs. Catheter insertion and removal dates were not consistently available.

At the second institution, chart records were reviewed in the Radiology Information System database for all patients with a history of long-term indwelling CVC placement and removal between January 2008 and July 2009. A manual chart review was then performed to determine which patients underwent chest CT after catheter removal. Duration of indwelling catheter placement and time from removal to CT, when available, was recorded. Seventy-five patients (46 men and 29 women; mean age 54 y) met the inclusion criteria, 3 of whom had 2 catheter placements recorded.

Our combined study population consisted of 77 men and 70 women, with a mean age of 58 years (range, 21 to 91 y). Indications for long-term indwelling CVC placement are listed in Table 1.

All study patients were screened for evidence of catheter infection. At the first institution, study subjects were screened for positive cultures of the catheter tip. All patients with positive cultures were considered infected if the organism was not coagulase-negative staphylococcus. In such instances, the positive culture was deemed a contaminant. In the second institution, Radiology Information System database was used to identify all patients who had their long-term indwelling CVC removed secondary to the clinical diagnosis of infection. Culture data were not available.

Chest CT scans for each study patient were reviewed on PACS workstations. When multiple studies were performed, the initial study after long-term indwelling CVC removal was reviewed, followed by subsequent studies. In patients who had undergone numerous CTs after catheter removal, subsequent CT scans were reviewed at monthly intervals.

Each chest CT was reviewed by 2 board-certified radiologists in consensus for the presence and location of a retained fibrin sheath, which was defined as a central or mural filling defect with a linear or tubular appearance within the venous system, whether calcified or noncalcified. Sheath location and original catheter position were correlated in patients with a record of a single-catheter placement. Additional findings such as venous occlusion or stenosis, venous collaterals, and pulmonary embolism were noted when possible. Scout and axial images were reviewed for all patients, as were sagittal and coronal reformats, when stored on PACS. Fifty patients underwent noncontrast CT, 83 had contrast-enhanced scans, and 14 patients had CTs both with and without contrast. For noncontrast scans in which veins were visible, an obvious decrease in venous caliber was considered positive for stenosis.

Although the study population comprised patients who had a history of prior long-term indwelling CVC removal, subsequently placed catheters were sometimes present at the time of CT; in those circumstances, if an indwelling catheter prevented evaluation of a particular venous segment, it was not assessed.

The prevalence of calcified and noncalcified fibrin sheath remnants was calculated. Bivariate analyses using the χ2 or Fisher exact test, as appropriate, were performed for dichotomous variables and the Student t test for continuous variables to assess for a relationship between fibrin sheath remnants and coexisting complications, age, sex, and diagnosis leading to long-term indwelling CVC placement, as well as catheter dwell time and duration between removal and CT, when available. Multivariate logistic regression analysis was then performed. Variables with a P value ≤0.2 on bivariate analysis were included in the regression model. A P value ≤0.05 was considered statistically significant.

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The prevalence of retained fibrin sheaths on chest CT after long-term indwelling CVC removal was 13.6% (20/147). In 9 patients (45%), the sheath remnants were calcified. One patient had 2 sheaths. The most common location was the right internal jugular vein (n=8), followed by the brachiocephalic veins (right, n=4; left, n=3), left internal jugular vein (n=2), and the right subclavian, left subclavian/left brachiocephalic veins, superior vena cava, and right atrium (n=1 each). The majority of noncalcified remnants [58% (7/12)] were located in the right internal jugular vein (Table 2). Calcified remnants showed a predilection for the brachiocephalic veins: right brachiocephalic vein and left subclavian/brachiocephalic vein (n=3 each).

The most common appearance for a retained fibrin sheath was an irregular linear or tubular filling defect (calcified, noncalcified, or both) within the central venous system (Figs. 1, 2). Fibrin sheath lengths varied, with the majority measuring between 1.5 and 5 mm; many were discontinuous. Sheath remnants spanned multiple veins in 35% of patients (7/20) in either a continuous or discontinuous manner. One patient had a remnant with a mixed morphology and a length of 16 cm (Fig. 3).

The CT appearance varied and depended on whether the scans were performed without or with intravenous contrast. Noncalcified sheaths were generally less conspicuous, whereas calcified sheaths were more conspicuous, on noncontrast CT (Fig. 4). Most CTs demonstrated formed sheaths after catheter removal; however, in 1 instance, evolution of infected pericatheter thrombus into a noncalcified sheath was observed (Fig. 5).

Bivariate analysis demonstrated that women had a significantly higher prevalence of retained fibrin sheaths compared with men: 23% (16/70) versus 5% (4/77), respectively (P=0.0018). No association was detected between retained sheath presence and patient age. The underlying diagnosis in the majority of patients with retained sheaths was end-stage renal disease [21% (8/38), compared with 11% (12/109) for the remaining diagnoses leading to catheter placement; P=0.1199].

Multiple long-term indwelling CVC–associated complications were detected in our patient population (Table 3). Venous occlusions [30% (6/20) vs. 5% (6/127), P=0.0001] and collaterals [30% (6/20) vs. 6% (7/127), P=0.0003] (Fig. 6) were both significantly more prevalent among patients with retained fibrin sheaths compared with patients without evidence of sheath remnants.

The mean catheter dwell time for the subset of patients with adequate dwell time documentation (n=78; 3 patients had a second catheter; only the interval between removal and CT was known for 2 patients) was 281 (SD 270) days (n=11) for patients with retained fibrin sheaths compared with 313 (SD 348) days (n=65) for patients without retained sheaths (t=0.30, P=0.77). There was a nonsignificantly longer dwell time of 472 (SD 342) days for the 4 patients with calcified remnants compared with 172 (SD 158) days for the 7 patients with noncalcified remnants (t=2.03, P=0.07). The interval between catheter removal and CT was nonsignificantly shorter for the 11 patients with retained fibrin sheaths [131 (SD 181) d] than for the 67 without [255 (SD 233) d] (t=1.68, P=0.10). Similarly, the patients with noncalcified remnants had a nonsignificantly shorter mean interval between catheter removal and CT compared with those whose remnants were calcified: 98 (SD 158) days versus 188 (SD 228) days (t=0.78, P=0.45), respectively.

Multivariate logistic regression analysis demonstrated a persistent significant relationship between the presence of fibrin sheath remnants, female sex (P=0.005), and venous occlusion (P=0.01) (Table 4).

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The present study demonstrates that fibrin sheath remnants are identified on chest CT in a substantial minority of patients after long-term indwelling CVC removal. This study showed a prevalence of 13.6% (20/147) and nearly half were calcified [45% (9/20)]. Fibrin sheath remnants occurred significantly more often in women than in men and were associated with venous occlusion. The most frequent location was the right internal jugular vein.

Venographic studies conducted at the time of catheter removal report a higher prevalence of retained fibrin sheaths, ranging from 48% to 65%.3,13 The discrepancy between venographic and CT prevalence may be attributed to several factors. As this was a retrospective review, the CT scans in the present series were performed at various times after catheter removal, and some of the remnants may have undergone lysis or embolization. In addition, the CT scans were performed using various techniques for varied clinical indications unrelated to the occurrence of retained fibrin sheaths. Therefore, some of the remnants may not have been detected. Generally, we noted noncalcified sheath remnants to be inconspicuous on noncontrast CT and calcified sheath remnants to be inconspicuous on contrast-enhanced scans.

The present study adds to the body of literature describing the CT appearances of fibrin sheath remnants and, to our best knowledge, is the largest to date. The most common appearance was a small irregular linear filling defect within the central venous system, which could be calcified, noncalcified, or both and which sometimes contained gas. Fibrin sheath lengths varied, with the majority measuring between 1.5 and 5 mm; the longest measured 16 cm. Several sheaths appeared discontinuous on CT. Given the retrospective nature of this study, we were not able to consistently follow the evolution of sheath remnants. However, we did observe calcification of a previously noncalcified sheath in 1 instance. In other cases, sheath remnants were measurably smaller on subsequent examinations, particularly in the case of a retained sheath containing gas after catheter removal for infection. This is consistent with the progressive process of cellular deposition noted in histologic studies,4–6 which continues to evolve after catheter removal. Although we did not confirm our results with venography, the similarity of our findings to the descriptions of fibrin sheaths in both prior histologic and prior venographic data serves to reinforce the validity of our findings.

In light of reports documenting calcified fibrin sheaths misdiagnosed as catheter fragments,7,8,19,20 understanding that calcified fibrin sheaths are often irregular in morphology, contain discontinuous foci of hyperattenuation representing calcification, and are frequently contiguous with noncalcified portions may help distinguish them from a retained catheter fragment. The latter would appear uniform in morphology with continuous areas of hyperattenuation corresponding to the catheter wall. Further, catheter fragmentation and retention is an exceedingly rare occurrence compared with a CT prevalence of fibrin sheath remnants of 13.6%.

The majority of remnants [67% (8/12)] were located within the right internal jugular vein. This finding is unlikely due to the biological effects of a particular vein. Rather, a right internal jugular approach is favored for central line placement as it is easier to access than the left internal jugular vein and has fewer complications than the subclavian approach.21

We found venous occlusion in 30% (6/20) of patients with retained fibrin sheaths on CT. Causation cannot be inferred from a retrospective design; therefore, we were unable to determine whether the presence of a fibrin sheath leads to venous occlusion or whether venous occlusion is a risk factor for the development of a retained fibrin sheath. However, knowledge of this association has practical implications. CT scans of patients who have venous occlusion and a history of long-term indwelling CVC removal should be carefully scrutinized for the presence of a retained fibrin sheath. Correctly differentiating a retained sheath from a thrombus has management implications. Anticoagulation is generally not recommended for retained fibrin sheaths,22 but this remains controversial and requires further study in a prospective clinical trial.

The present study identified a statistically significantly higher incidence of sheath remnants in women. This result matches similar observations made in a prospective venography study by Oguzkurt et al.23 One explanation is that women’s veins are smaller than men’s and that the same-sized catheters are used in both populations. In animal studies by Xiang et al,5 a smaller ratio between vein and catheter diameter was associated with a higher incidence of sheath formation. They proposed that this results from increased contact between the catheter and venous wall, which promotes the development of sheaths. Further animal studies by Kohler and Kirkman24 demonstrated that stabilizing the catheter tip reduces chronic venous wall injury and resulting thrombosis. This may also explain the fact that fibrin sheaths were present more often in patients who had catheters placed for end-stage renal disease and less often in patients whose catheters were placed for long-term antibiotic administration. Dialysis catheters are typically large-bore catheters and thus more likely to come in contact with the venous wall. In contrast, PICCs typically have a narrow diameter (between 5 and 6 Fr) and are therefore less likely to provoke venous injury. In addition, hemodialysis catheters are typically left in place for longer periods compared with PICCs, which may predispose them to sheath formation.

The variations in sheath prevalence on the basis of indication for catheter placement, catheter dwell time, and the interval between catheter removal and CT did not achieve statistical significance in the present study. It is logical to assume that, over time, noncalcified remnants may calcify or disintegrate.23 However, a larger sample size is needed to confirm or refute these associations.

The true prevalence of pulmonary embolism related to fibrin sheath remnants is uncertain because of lack of systematic investigation. We detected only a single case of pulmonary embolism in a patient with a retained fibrin sheath, although the majority of CT scans were not protocolled to evaluate for suspected pulmonary embolism. In a prospective study using venography during removal of indwelling long-term CVCs, Oguzkurt et al13 demonstrated that fibrin sheaths remain adherent to the vein wall and do not embolize upon catheter removal, although pulmonary embolism was not specifically excluded. Brismar et al3 demonstrated symptomatic pulmonary embolism on a V/Q scan in 3 of 60 patients after long-term CVC removal. In addition, 2 case reports describe the development of pulmonary embolism due to fibrin sheath embolization; 1 followed a stripping procedure and was not spontaneous.16,25

We did not find an association between retained fibrin sheaths and catheter infection, although prior studies have demonstrated a correlation between thrombosis and infection. In a cohort of patients in the intensive care unit, Timsit et al26 demonstrated a 2.62-fold higher risk for catheter-related sepsis when thrombosis occurred. Similarly, Raad et al12 demonstrated an association between mural thrombosis and catheter sepsis in cancer patients. A larger cohort of patients may be needed to confirm or refute this association in patients with retained fibrin sheaths.

A main limitation of the present study is its retrospective nature. Therefore, we could not draw causal inferences. The CT protocols were not optimized for detection of fibrin sheath remnants. In addition, our sample size was insufficient to reach definitive conclusions on the relationship between the development of fibrin sheaths and infection, pulmonary embolism, catheter dwell time, or time interval between removal and CT. Some venous segments could not be evaluated because of the presence of indwelling catheters, which may have resulted in an underestimation of the prevalence of fibrin sheath remnants. However, the inclusion of both noncontrast and contrast-enhanced studies, as well as of patients with current indwelling catheters, reflects daily clinical practice in which various CT protocols are acquired, which are based on patients’ renal function and appropriate clinical context.

In conclusion, retained fibrin sheaths are present in a substantial minority of patients after long-term indwelling CVC removal and can be identified on standard CT imaging. Sheath remnants are found more frequently in women and are associated with venous occlusion. The results of this study may serve to increase awareness of this underreported phenomenon and adds to the sparse literature describing the CT appearance of fibrin sheath remnants, which should not be mistaken for catheter fragments.

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computed tomography; catheters; veins

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