Detection of radiolucent wooden foreign bodies: diagnostic insights for computed tomography imaging

Introduction

Foreign bodies retained in the body are commonly encountered in the emergency department (ED). Kudo et al. reported a case in which a wooden stick had penetrated a boy’s right nasal cavity, highlighting the difficulty of detecting wooden foreign bodies on imaging (1). A foreign body in the soft tissue is difficult to detect due to being radiolucent but may be identified via sonography (2-6). Another method for detection is the direct regulation of the window levels (Hounsfield units), after which the wooden material may become visible (7). Ingraham et al. noted the value of computed tomography (CT) window adjustments and were the first to propose an optimal Hounsfield unit range for enabling consistent detection (3).

Here, we present a case that highlights the diagnostic difficulty caused by the radiolucency of wood rather than the anatomical location of the foreign body. The solution to detection lies in adjusting the CT window settings toward lung window parameters.

Case presentation

A 42-year-old male arrived at the ED in MacKay Memorial Hospital, Taipei, seeking assistance for the removal of a wooden object retained in his rectum. He admitted to inserting the object, described as a Y-shaped wooden massager typically used for shoulder and neck massage, for sexual stimulation approximately 8 hours prior to his ED visit. The object measured approximately 10 cm × 4.5 cm and weighed 35 g, as per the product description on a shopping website. The patient denied experiencing fever, nausea, vomiting, abdominal pain, diarrhea, or bloody stool. Initial imaging with kidney-ureter-bladder (KUB) X-ray revealed only nonspecific findings of bowel gas and stool collection (Figure 1). All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Figure 1 Plain abdominal radiograph (KUB) showing nonspecific findings of bowel gas and stool collection. No obvious foreign body is visible on initial X-ray imaging. KUB, kidney-ureter-bladder.

Laboratory investigations indicated mild leukocytosis (11,000/µL), and subsequent abdominal CT revealed no evidence of bowel wall thickening, pericolonic fat stranding, or fluid collection, suggesting no acute inflammation or perforation was present (Figure 2A). An abnormal low-absorption image (air-like image) was observed, although the foreign body could not be clearly identified within the colon.

Figure 2 Standard abdominal CT showed no free air or detectable foreign body. After adjusting the lung window (−270 to −300 HU), a radiolucent object ~10 cm long was identified in the rectum and sigmoid colon. Emergent sigmoidoscopy confirmed a foreign body measuring 11.5 cm. (A) Abdominal CT yielded no evidence of free air in the abdomen and no obvious foreign body within the colon. (B) Upon adjustment of the lung window to a window level of −270 to −300 Hounsfield units, a radiolucent hypodense foreign body measuring nearly 10 cm in length was identified in the rectum and sigmoid colon. (C) After detection of the foreign body, a proctologist was consulted, and an emergent flexible sigmoidoscopy was performed, revealing the foreign body measuring 11.5 cm in the greatest dimension. CT, computed tomography.

However, upon adjustment to lung window settings, a radiolucent hypodense foreign body measuring nearly 10 cm in length was identified in the rectum and sigmoid colon with a window level ranging from −270 to −300 Hounsfield units (Figure 2B).

Consequently, a proctologist was consulted, and an emergent flexible sigmoidoscopy was performed, in which the foreign body was grasped with a flexible sigmoidoscope and a large endoscopic retrieval snare and extracted transanally. The foreign body measured 11.5 cm in the greatest dimension (Figure 2C). Successful removal of the object was achieved without complications.

Discussion

This case indicates that a CT window level range of −270 to −300 Hounsfield units may be optimal for the visualization of wooden foreign bodies—a quantitative parameter that has not previously been proposed. Several reports have described wooden material as a foreign body involved in various conditions such as chest trauma (8) and perforated Meckel’s diverticulum (9) and located in the renal pelvis (10), thigh (11), head (12), knee (13), and nasal cavity (14). A foreign body in the head can sometimes be difficult to visualize, if there is no neurological deficit, as the wood material may not be detectable on plain X-ray (15). In some reports, the wooden foreign bodies were found via surgical exploration after initial negative findings on X-ray (16-18). The most common locations of foreign bodies are the limbs, with 31% of these cases involving a wood material (5), and the second most common site is the feet (19). The surgeon should maintain a high index to detect radiolucent foreign bodies even if the initial X-ray is a negative (20). Another option is the direct regulation of the window levels so that the wooden material appears on CT. Suggested protocol: if a foreign body is suspected but not clearly visualized in the standard abdominal window, a secondary review using the lung window should be performed.

Our findings confirmed that visibility is dependent on Hounsfield level adjustments regardless of the anatomical location. Table 1 summarizes and compares the findings of the relevant literature.

Conclusions

A wooden foreign body is easily misdiagnosed by plain film X-ray CT unless the Hounsfield unit is appropriately downregulated for detection. We recommend adjusting CT window levels between −270 and −300 Hounsfield units when a radiolucent foreign body is suspected.

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-85/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Kudo S, Takei T. Computed tomography settings for optimal detection of wooden foreign bodies. Am J Emerg Med 2016;34:2237-8. [Crossref] [PubMed]
2. Lewis D, Jivraj A, Atkinson P, Jarman R. My patient is injured: identifying foreign bodies with ultrasound. Ultrasound 2015;23:174-80. [Crossref] [PubMed]
3. Ingraham CR, Mannelli L, Robinson JD, Linnau KF. Radiology of foreign bodies: how do we image them? Emerg Radiol 2015;22:425-30. [Crossref] [PubMed]
4. Nazwar TA, Bal'afif F, Wardhana DW, Panjaitan C. Penetrating Neck Injury Involving Wooden Foreign Bodies: Case Report. Korean J Neurotrauma 2023;19:502-8. [Crossref] [PubMed]
5. White RZ, Rezaian P, Parasuramar A, Sampson MJ. Ultrasound-assisted foreign body extraction (U-SAFE): Review of technique and technical pearls. J Med Imaging Radiat Oncol 2022;66:362-9. [Crossref] [PubMed]
6. Matsuno H, Watanabe T, Tada S, Sekine A, Nohisa Y, Shinoda K, Furuta N, Ito H, Shu E, Seishima M. Sonographic Detection of Subcutaneous Foreign Bodies in 3 Cases. Acta Dermatovenerol Croat 2016;24:299-302.
7. Shiraki Y, Takahashi T, Ogi M, Horii A. Changes in CT values of wood in the body: pitfalls in detecting a wooden foreign body. BMJ Case Rep 2024;17:e259348. [Crossref] [PubMed]
8. Suciu BA, Bud V, Strat A, Copotoiu AC. Large piece of wood board removal and long term survival in a patient with stabbed thoracic wound - case report. Chirurgia (Bucur) 2014;109:682-4.
9. Anyfantakis D, Kastanakis M, Papadomichelakis A, Kokinos I, Katsougris N, Petrakis G, Karona P, Bobolakis E. Perforation of Meckel's diverticulum by a wood splinter in a 4-year-old child: a case report. J Med Life 2013;6:195-7.
10. Tüdös Z, Čtvrtlík F, Kratochvíl P, Král M. Wooden Foreign Body in the Renal Pelvis. Urology 2016;94:e7-8. [Crossref] [PubMed]
11. Kumar K, Hegazy A. Rare presentation of a wooden foreign body in the thigh. Eur J Orthop Surg Traumatol 2012;22:155-9. [Crossref] [PubMed]
12. Sanli AM, Kertmen H, Yilmaz ER, Sekerci Z. A retained wood penetrating the superior orbital fissure in a neurologically intact child. Turk Neurosurg 2012;22:393-7. [Crossref] [PubMed]
13. O'Connell RL, Fageir MM, Addison A. Be aware of wood in the knee. BMJ Case Rep 2011;
14. Park TH. Penetration of a Wooden Foreign Body into the Zygomaticomaxillary Bone to the Nasal Cavity: Navigation-Guided Successful Treatment. J Craniofac Surg 2023;34:e403-4. [Crossref] [PubMed]
15. Kim DH, Park ES, Seong HY, Park JB, Kwon SC, Sim HB, Lyo IU. A Case of Intracranial Wooden Foreign Body: Mimicking Pneumocephalus. Korean J Neurotrauma 2016;12:144-7. [Crossref] [PubMed]
16. Armstrong D, Owens R, Carlson T, Ching B. Retained foreign body misdiagnosed as a low flow vascular malformation: A case report. Radiol Case Rep 2024;19:164-71. [Crossref] [PubMed]
17. Hwang K, Park CY. Intraorbital Wooden Foreign Body in a Soldier. J Craniofac Surg 2023;34:e592-3. [Crossref] [PubMed]
18. Gamble JG. Late Presentation of a Retained Wood Foreign Body as an Expanding Soft-Tissue Mass in an Adolescent's Foot: A Case Report. JBJS Case Connect 2023;
19. Abdelbaki A, Assani S, Bhatt N, Karol I, Feldman A. Retained Wooden Foreign Body in the Second Metatarsal. J Am Podiatr Med Assoc 2018;108:168-71. [Crossref] [PubMed]
20. Vaishnav YJ, Portelli D, Migliori ME. Delayed Diagnosis of an Occult Wooden Orbital Foreign Body. R I Med J (2013) 2020;103:49-51.