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How to precisely identify the position of a needle accidentally inserted into the perineal area?

  • francoisbiquillon
  • Feb 22
  • 3 min read

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To precisely locate a needle (or a metallic foreign body) accidentally inserted into the perineal area, medical imaging is generally used. The perineum is an anatomically complex area (rich in soft tissues, vascularization and close to sensitive organs), hence the importance of a reliable investigation method. Here are the main methods and advice for identifying the exact position of the needle:


1. Initial clinical assessment


  1. Visual examination and palpation


  • Look for a possible needle protrusion or an insertion orifice.

  • Gently palpate the area for a localized painful point or abnormal induration.


  1. Risk assessment


  • Check whether the patient has neurovascular signs (tingling, motor disorders, extensive hematoma, etc.), indicating a deeper lesion or proximity to critical structures.


However, palpation alone is not enough to precisely locate the position of a metal fragment, especially if it is deeply buried or has moved. This is why imaging is essential.



  1. Basic imaging: standard radiography


  1. Simple radiography (X-rays)


  • A first standard radiography (ideally in two incidences: face and profile, or even three incidences) is often performed to locate the metallic foreign body.


  • Since metals are radio-opaque, the needle generally appears clearly on the image.


  1. Limitations of radiography


  • The superposition of the bony structures of the pelvis and the complexity of the perineal region can hinder very precise localization.


  • The radiography gives an idea of ​​the height (cranio-caudal) and part of the depth, but it may lack finesse if the needle is very thin or hidden by other plans.



  1. More advanced imaging: ultrasound and especially CT (scanner)


3.1. Ultrasound


  • Interest


  • Useful for locating a superficial metal fragment or in shallow soft tissues (e.g.: labia majora in women, scrotal or subcutaneous region in men).


  • Ultrasound can sometimes identify a hyperechoic artifact (bright white point) with a posterior shadow cone characteristic of a metal object.


  • Limitations


  • Less accurate for deep objects in the pelvis or in the anorectal area.


  • The presence of intestinal gas or the patient's morphology (obesity, etc.) can complicate the examination.


3.2. CT scan


  • The reference technique for precise localization


  • CT scan (or computed tomography) is the most reliable method for locating a metallic foreign body in the perineal region with great precision, thanks to cross-sectional imaging and the possibility of three-dimensional reconstruction.


  • It allows the exact distance between the needle and neighboring anatomical structures (urethra, rectum, vessels, nerves, etc.) to be determined.


  • Advantages


  • Speed ​​of acquisition.


  • 3D visualization facilitating the planning of an extraction procedure (aid for surgical location).


  • Better sensitivity for metallic objects than ultrasound when they are deep or in areas of bone superposition.



4. Interventional techniques and guidance


  1. Intraoperative guidance


  • If the foreign body must be surgically removed, the surgeon can use:


  • A real-time image intensifier (fluoroscopy) in the operating room.


  • Intraoperative ultrasound, if ultrasound localization is possible (for a superficial foreign body).


  • This allows the progress of the instruments to be followed and the exact position of the needle to be checked during extraction.


  1. Preoperative marking


  • In some cases, before the procedure, a radiologist can perform a marking (injection of a locatable product or placement of a guide wire under scanner or ultrasound) to help the surgeon quickly locate the object during surgery.



5. Summary and course of action


  1. Standard X-ray


  • First images (2 to 3 incidences) to confirm the presence of a metallic foreign body and obtain a rough localization (height, lateralization).


  1. Scanner


  • Examination of choice for anatomical precision, surgical planning and 3D visualization.


  1. Ultrasound


  • Possible complement in the event of superficial localization or for simple interventional guidance.


  1. Surgical or guided extraction


  • The decision depends on the depth, location (proximity to vital structures), risk of infection or injury, and clinical context (pain, complications, etc.).


Conclusion


To precisely identify the position of a needle accidentally inserted into the perineal region, the typical procedure consists of:

1. Confirm the presence and metallic nature via an x-ray (multiple incidences).

2. Specify the exact location using a scanner to visualize the relationship with the organs and vascular/nervous structures.

3. If necessary, consider guidance (fluoroscopy, ultrasound) to facilitate extraction, especially if the fragment is difficult to access.

This multidisciplinary approach (radiology-surgery) guarantees the best safety for the patient and the most exact localization possible of the foreign body.

 
 
 

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