A 27 year old female, former intravenous substance user on methadone replacement therapy, who had underwent caesarean 5 months previous, presented with inflammatory signs over the suture and localized pain. These did not improve with medical therapy.
An ultrasound (US) of the abdominal wall was performed.
High frequency US of the abdominal wall reveals fluid surrounding a hyperechoic structure, 7mm deep in the abdominal wall. This appears to be a hollow, tubular thin solid structure (56mm long) eliciting inflammatory reaction.
US showed hyper-echoic structure suggestive of foreign body (FB). The hypothesis raised was that of a lost surgical drain (or part) within the abdominal wall. However, such a drain had not been employed. Surgical exploration revealed a coiled portion of thin transparent plastic sheet.
In caesareans (and other surgeries) an incise drape is commonly used. It consists in a clear adhesive surgical drape of flexible film that provides a sterile surface to the wound edge. Incision of skin and more profound layers towards the uterus is preceded by cutting the incise drape.
On this case we hypothesize that a small portion of the cut plastic was lost during the intervention. Inside the abdominal wall the sheet coiled and presented on US as a thin tubular, arcuate hyperechoic image.
US technique involves high-frequency (7.5MHz or higher) linear-array transducer. US permits accurate location of the superficial FB, estimation of size, shape and orientation, as well as skin marking and guidance for excision [1-4]. It allows evaluation of surrounding tissues, assessment of fluid collections, injury to tendons, vascular or neurologic structures.
The degree of echogenicity of a given foreign body (FB) relates to the differences in acoustic impedance at the interface between the FB and surroundings [4]. FBs present as hyperechoic [4-6] at least initially, as wooden FBs can become less echogenic with time [7].
FBs present with different posterior artefacts, depending on the surface attributes. Flat, smooth surfaces with large radiuses cast dirty shadows, while irregular surfaces or those with small radiuses cast clean shadows [8].
The presence of hypoechoic rim surrounding the FB represents inflammatory reaction and can be found when the FB is present in the soft tissues for over 24 hours. This finding is reported to improve sensitivity and specificity of the US examination. [9-11]
US is the ideal modality to evaluate superficial FBs, being more effective than computed tomography (CT) [6,11,12]. Multiple studies have shown US to have high sensitivity and specificity (90.0% and 96.7% respectively on Jacobson’s series [11]).
US limitations include operator dependence (studies show low sensitivity and specificity for those “relatively inexperienced” [13,14]). Furthermore, effectiveness of US is only valid for superficial FBs, and these may not be accessible to US when deep to bone or gas [5,6]. US is prone to false positive findings, benefiting from correlation with conventional radiography (CR). US may underestimate FB size when imaged end on, parallel to the beam [15].
CR may detect up to 80% of FBs [16]. Some FBs are not radiopaque - particularly those of vegetable origin as wood splinters: up to 85% of these cannot be identified on radiographs [3,11]. Plastic FBs such as the one described are reported to be radiolucent [7].
CT is reported to be about 15 times more sensitive than CR [9], but less sensitive than US and MR. It requires ionizing radiation, is less available and more costly than US, and in some cases (such as paediatric) requires sedation.
MR does not require radiation but is more costly, less available and may not offer good differentiation between a FB with low signal intensity and surrounding tissue of inherent low signal (scar tissue, tendons, calcifications) [11,16].
Foreign body (surgical material): incise drape.
The patient is a 27-year-old female who underwent a cesarean section 5 months ago. Ultrasound examination was performed using a high-frequency linear probe (≥7.5 MHz). At the postoperative incision site of the abdominal wall, a slender, curved, high-echo linear structure was observed, with inflammatory changes in the surrounding area (including decreased echogenicity of surrounding tissues and possible small amounts of fluid-filled dark areas). This high-echo structure is thin in shape, suggesting it is caused by the boundary between high acoustic impedance and the surrounding tissues. During the examination, manipulation can further locate the depth and direction of the foreign body.
Considering the patient’s past surgical history, local inflammatory symptoms, and the high-echo linear structure seen on ultrasound, the most likely diagnosis is a retained plastic film foreign body (incision drape fragment). This foreign body causes a chronic inflammatory reaction locally, leading to repeated pain, redness, and poor healing at the incision site.
Since the abdominal wall area is prone to tension and pulling after surgery, a proper exercise plan should be arranged during the wound healing period, following the FITT-VP principle, to avoid placing excessive stress on the incision.
Individual Considerations: Given the patient’s history of intravenous medication use and surgical background, special attention should be paid to nutritional status and overall physical condition. If pain worsens, swelling increases at the incision site, or any signs of suspected infection appear, re-evaluation should be done promptly.
Disclaimer: This report is a reference analysis based on current information and does not replace in-person consultation or professional medical guidance. Specific treatment plans should be further confirmed in conjunction with the patient’s actual condition and professional medical opinions.
Foreign body (surgical material): incise drape.
