Tissue reactions of abdominal integuments to surgical sutures in sonography

Abstract

Classical abdominal surgeries usually require long incisions of the abdominal integuments followed by tight closure with adequate suturing material. Nonabsorbable sutures may cause various reactions, including granuloma reactions, both sterile and inflammatory.

The aim of the study

The aim of the study was to analyze prospective ultrasound examinations of the abdominal integuments in order to detect tissue reactions to surgical sutures.

Material and methods

For 10 years, ultrasound examinations of the abdominal integuments involved the assessment of surgical scars in all patients who underwent open or closed surgeries for various reasons (in total 2254 patients). Ultrasound examinations were performed only with the use of linear probes with the frequency ranging from 7 to 12 MHz. Each scar in the abdominal integuments was scanned in at least two planes. When a lesion was detected, the image was enlarged and the transducer was rotated by approximately 180° in order to capture the dimensions of the granuloma and the most characteristic image of the suture. Moreover, vascularization of the lesion was also assessed with the use of color Doppler mode set to detect the lowest flows.

Results

All granulomas (19 lesions, two in one patient) created hypoechoic oval or round nodules, were relatively well-circumscribed and their size ranged from 8 × 4 mm to 40 × 14 mm. In the center of the lesion, it was possible to notice a thread that was coiled to various degrees and presented itself as a double, curved hyperechoic line. In 9 out of 19 granulomas, slight peripheral vascularization was observed. The substantial majority of the lesions (n = 15) were in contact with the fascia. In seven patients, compression with the transducer induced known local pain (n = 4) or intensified pain that had already been present (n = 3); all of these granulomas infiltrated the fascia and showed slight peripheral vascularization. Cutaneous fistulae developed in two patients with purulent reactions to the running stitch (in one patient – two fistulae).

Conclusions

Suture granulomas in the abdominal integuments manifest themselves as nodular hypoechoic lesions, usually localized at the edge of the fascia – subcutaneous fat. A pathognomonic sign of this type of granulomas is the presence of a thread in their center that usually manifests itself as a chaotically shaped, double hyperechoic line. In some granulomas, particularly those with clinical presentation, slight peripheral vascularization is observed.

A surgical incision of the abdominal integuments is associated with a risk of various complications which may be divided into early and late ones. The former include infection, hematoma, abscess, wound dehiscence and eventration. Late consequences of postoperative wounds are hernias, visceroperitoneal adhesions, cutaneous fistulae, granulomas and chronic infections. The last two frequently occur toget her. A gra nuloma is a nodula r response of giant cells to a foreign body which is usually a nonabsorbable surgical suture. This type of suturing material is frequently used when closing a wound after laparotomy. In studies conducted on rats, it was demonstrated that slight granulomas around nonabsorbable sutures persisted for 150 days following their placement⁽¹⁾. Sometimes, however, a reaction to implanted material may be tumor-like, thus causing a diagnostic difficulty. There are reports of granulomas that formed after various surgical interventions in multiple organs (from the head to the feet) and were erroneously diagnosed as a recurrence of a neoplasm^(2–12).

The aim of the study was to analyze prospective ultrasound (US) examinations of the abdominal integuments in order to detect tissue reactions to surgical sutures.

Material and methods

Within 10 years (2003–2012), ultrasound examinations of the abdominal integuments involved the assessment of surgical scars in all patients who underwent open or closed surgeries for various reasons. The clinical material comprised 2254 subjects, including 1552 patients who underwent laparoscopic procedures and 702 patients after classical laparotomy. In the latter group, 18 patients (10 women and 8 men aged from 30 to 80, the mean age was 53) had a tumor-like granuloma in the postoperative scar. In two of them, the wound was purulent due to the presence of surgical sutures (2.6%). The basic sonographic criterion in diagnosing granulomas was the image of chaotically shaped sutures in the center of a hypoechoic nodule localized within the postoperative scar⁽¹³⁾. Moreover, it was attempted to determine the localization of the lesion in relation to the superficial fascia and assess its vascularization. The presence of cutaneous fistula and the presence of content within it were also noted. The US examinations were performed using only linear transducers with the frequency of 7–12 MHz and with the use of the following systems: Nemo 30 and Xario by Toshiba, Sonoace Pico X8 by Medison as well as HD11 XE by Philips. Each scar in the abdominal integuments was scanned in at least two planes. This concerned all the subjects irrespective of the presence of local symptoms associated with the postoperative scar. When a lesion was detected, the image was enlarged and the transducer was rotated by approximately 180° in order to capture the dimensions of the granuloma and the most characteristic image of the suture. Moreover, vascularization of the lesion was also assessed with the use of color Doppler mode set to detect the lowest flows. Furthermore, by compressing the site of the lesion with the transducer, it was attempted to induce pain and observe flow of contents in the cutaneous fistulae. Eight patients with granulomas and two with purulent wounds underwent surgeries, which confirmed the diagnoses. The remaining subjects without evident symptoms were followed-up sonographically in the period from 6 to 24 months. The tissue reactions to surgical sutures were diagnosed 29 months (mean) after the surgery (range from 6 months to 14 years).

Results

All relevant clinical and sonographic data are presented in tab. 1. The tissue reactions to surgical sutures were diagnosed 29 months (mean) after the surgery (range from 6 months to 14 years). The reactions were observed within the scars after appendectomy (n = 6) and more rarely after hysterectomy (n = 3), cholecystectomy (n = 2) and gastrectomy (n = 2). In the scars after Whipple procedure, pancreatic necrosectomy, prostatectomy, transverse colon resection and surgery of inguinal hernia, granulomas were observed only in single cases. All granulomas (19 lesions, two in one patient) created hypoechoic oval or round nodules, were relatively well-circumscribed and their size ranged from 8 × 4 mm to 40 × 14 mm. In the center of the lesion, it was possible to notice a thread that was coiled to various degrees and presented itself as a double, curved hyperechoic line (fig. 1) or a double dashed line (fig. 2). In 9 out of 19 granulomas, slight vascularization was observed (fig. 3). The substantial majority of the lesions (n = 15) were in contact with the fascia (fig. 4), but four nodules were connected only in the layer of the subcutaneous fat (fig. 5). In seven patients, compression with the transducer induced known local pain (n = 4) or intensified pain that had already been present (n = 3); all of these granulomas infiltrated the fascia and showed slight peripheral vascularization. Cutaneous fistulae developed in two patients (case 17 and 18 in tab. 1) with purulent reactions to the running stitch (in one patient – two fistulae). There was fluid around the surgical suture that showed slight flow when compression with the transducer was applied (fig. 6).

Tab. 1.

Clinical and sonographic data of 18 patients with tissue reaction to surgical sutures

No	Patient sex	Age	Greatest lesion size	Suture image	Contact of the lesion with the fascia	Present vascularization	Scar after	Time from surgery
1	W	60	25 × 15 mm	+	+	+	appendectomy	5 years
2	W	80	27 × 14 mm	+	+	+	appendectomy	14 years
3	W	66	40 × 13 mm 12 × 10 mm	+ +	+ −	+ −	transverse colon resection	6 years
4	M	56	10 × 8 mm	+	−	−	gastrectomy	4 years
5	M	30	40 × 14 mm	+	+	+	appendectomy	3 years
6	W	57	25 × 9 mm	+	+	+	cholecystectomy	3 years
7	M	59	28 × 9 mm	+	+	−	gastrectomy	2 years
8	W	68	12 × 10 mm	+	+	−	hysterectomy	19 months
9	W	57	12 × 8 mm	+	+	−	hysterectomy	25 months
10	M	50	8 × 4 mm	+	+	−	appendectomy	15 months
11	W	37	12 × 8 mm	+	+	+	appendectomy	18 months
12	W	62	13 × 8 mm	+	+	+	cholecystectomy	22 months
13	M	65	15 × 7 mm	+	+	+	appendectomy	38 months
14	M	64	22 × 13 mm	+	−	−	prostatectomy	18 months
15	M	52	25 × 11 mm	+	+	+	Whipple procedure	21 months
16	M	45	28 × 24 mm	+	−	−	hernia procedure	6 months
17	W	68	88 × 7 mm	+	+	−	hysterectomy	26 months
18	W	54	48 × 4 mm	+	+	−	pancreatic necrosectomy	15 months

Fig. 1.

Hypoechoic lesion corresponding to a granuloma in two planes: tissue reaction to an untangled knot of a single suture that manifests itself as a double hyperechoic line (arrows)

Fig. 2.

Granuloma around an untangled suture following hysterectomy, two planes. Sonographic signs of a braided suture (arrow)

Fig. 3.

Suture granuloma following appendectomy with peripheral vascularization, two planes

Fig. 4.

Granuloma with visible suture thread (arrows) infiltrates the fascia

Fig. 5.

Suture granuloma (arrows) localized in the subcutaneous fat, two planes

Fig. 6.

The combined image shows a running stitch surrounded with hypoechoic purulent material (arrows)

Discussion

A rejection reaction to implanted organs or tissues is an inherent feature of living organisms and a problem in the field of transplantology. When suturing material is used, a similar reaction may be expected, but to a lower extent^{(1, 12, 13)}. Bielecki⁽¹⁴⁾ lists the following types of these materials depending on their origin: non-organic (metal wire, Michel clips, staples), organic (silk, Florence sutures, flax) and synthetic (synthetic material: nylon, prolene, polytetra). With respect to the structure of sutures, they are divided into: mono filament, multifilament, twisted, braided, coated and uncoated sutures. Rettenbacher et al.⁽¹³⁾ investigated the sonographic appearance of monofilament and braided surgical sutures in a water bath (in vitro examinations). It was demonstrated that a monofilament thread manifests itself as a double hyperechoic line in the longitudinal plane and it was described as a “rail-like line.” In the transverse plane, it appears as double dots. A braided thread also gives the appearance of a double line, but its surface is uneven and broken in multiples places.

In the subjects analyzed in this study, the substantial majority of granulomas (14 out of 19) gave a typical appearance of a monofilament thread (fig. 1), but in five remaining lesions, the US image corresponded to a braided suture (fig. 2). It is worth emphasizing that symptomatic granulomas always infiltrated the fascia and were accompanied by slight hyperemia, which was not observed in previous publications. Moreover, all lesions developed around an untangled knot which suggests irritation associated with the suture becoming more movable.

As far as abdominal integuments are concerned, sonography fulfils the requirements of not only the initial, but also final examination in diagnosing tissue reactions to the suturing material. The authors of the study⁽¹⁵⁾ demonstrated this by analyzing 20 cases of granulomas that formed in children following surgeries of inguinal hernias. US correctly identified the cause of nodule formation in 19 patients in the period from one year to 10 years after abdominal wall reconstruction, which was a much better outcome than in computed tomography. Rettenbacher et al.⁽¹³⁾ obtained similar results. With the use of sonography, they managed to correctly identify 20 out of 22 granulomas (91%). The two mistakes are explained with the use of a 5 MHz transducer in the first stage. This methodical error was avoided in this study by applying solely transducers with a higher frequency (7–12 MHz), which in all cases, enabled to visualize sutures in the lesions – a pathognomonic sign of a foreign body granuloma. Such a specific presentation of granulomas is not usually possible to obtain using computed tomography or even magnetic resonance imaging^{(9, 10, 15–17)}. Positron emission tomography, in turn, sometimes gives false positive results, particularly in oncological patients followed-up to detect a relapse^(4–6). In the case of uncertainties, biopsy may be performed^{(5, 16–18)}.

Granulomas constitute the greatest diagnostic problem in oncological patients who are followed-up after surgical procedures. Kim et al.⁽¹⁹⁾ specified the differences between a recurrence and granuloma in their comparative studies of the thyroid bed after thyroidectomy in oncological patients. In the case of granulomas, the centrally or paracentrally located hyperechoic points, which were paired and usually larger than 1 mm, were observed more frequently. Microcalcifications in recurrent tumors, however, were localized mainly at the periphery of the lesion and were smaller. When scanning the lesions, we applied rotation, which enabled capturing the most representative images of the sutures. It appears that 3D imaging would be an optimal solution, but so far no information on this technique has been found in available literature.

Rettenbacher et al.⁽¹³⁾ suggest including infected epidermoid cysts in the differential diagnosis since hair may mimic the presence of a suture. It should be remembered that sometimes absorbable sutures may cause granulomas^{(13, 16)} – in such cases, the typical image of a suture inside the lesion is not present. Furthermore, an untangled suture is more likely to move beyond the scar in the inguinal region; this results from the connection of the torso (which does not move much) to the lower limbs (characterized by considerable movability)^{(11, 17)}. Time that lapsed from suturing does not help in establishing a correct diagnosis of granulomas; the situations in which lesions are identified after many years following suturing are nor rare^{(2, 5, 10, 13, 16)}.

Conclusions

1. Suture granulomas in the abdominal integuments manifest themselves as nodular hypoechoic lesions, usually localized at the edge of the fascia – subcutaneous fat.

2. A pathognomonic sign of this type of granulomas is the presence of a suture in their center that usually manifests itself as a chaotically shaped, double hyperechoic line.

3. In some granulomas, particularly those with clinical presentation, slight peripheral vascularization is observed.

Conflict of interest

Authors do not report any financial or personal links with other persons or organizations, which might affect negatively the content of this publication and/or claim authorship rights to this publication.