One year prior to presentation to AMC, the dog had a stick removed from her mouth by the owner.
10 days after this stick was removed, drainage from the right pre-scapular region was first noted. This led to three unsuccessful surgeries attempting to relieve the drainage. Medical therapy (antibiotics and prednisone) was also unsuccessful. Chronic diffuse skin disease (alopecia, pruritus, lichenification) developed during this same time period. On presentation to AMC, a draining tract cranial to the right humeral head remained present.
Dorsal and transverse STIR and T2-weighted images include the shoulders, cranial thorax, and neck in the field of view. Transverse fat-saturated (SPIR) T1-weighted images were made before and after IV contrast administration. The dorsal T1W_SPIRs were incompletely fat-suppressed and were therefore omitted from this presentation. An approximately 4.6cm foreign body is noted; it is surrounded by T2/STIR hyperintense fluid, within the soft tissues medial to an enlarged (2.6cm) superficial cervical lymph node. The tract could be followed dorsal to the lymph node to exit the skin cranial to the shoulder. A small branch of the tract was noted to extend craniodorsally, lateral to the trachea and medial to the right external jugular vein. It appeared to end adjacent to the cranialmost extent of the esophagus. Soft tissues surrounding the foreign body and lining the fluid-filled tract contrast enhance.
- Focal large linear foreign body, cranial to the right shoulder with fistulous tract communicating with the skin.
- Secondary reactive superficial cervical lymphadenopathy.
Comment: We suspect the foreign body pierced the larynx/cranial esophagus (oral ingestion) and migrated ventrally
Surgery: MRI helped to guide an 8Fr red rubber catheter into the fistula leading to the foreign body (a 4.0 cm long wooden stick). The foreign material was subsequently removed. Surrounding tissues were debrided, and the superficial cervical lymph node was excised. Deep cultures were performed, and tissue was submitted for histopathology.
Histopathology: A fistulous tract with associated severe pyogranulomatous dermatitis and panniculitis, hyperplasia of adjacent epidermis, chronic dermatitis, and hydradenitis was noted. The lymph node was markedly hyperplastic, consistent with reaction to regional inflammation. Culture: Enterococcus (resistant to Marbofloxacin); patient treated with Clavamox (previously treated with Marbofloxacin)
Follow-up: The site of previous draining tract was fully healed with no recurrence of a draining tract.
MRI imaging of a cervical wooden foreign body has been previously described.1 T2 and pre/post-contrast T1-weight imaging sequences were performed. The lining of the tract is nicely enhanced in both the present study and in this case report. For both CT and MRI, the surrounding tissue inflammatory reaction may constitute the most visible abnormality.1,2 In another case report, sequential MR imaging showed the temporal progression of fibrous encapsulation of a retrobulbar grass awn abscess.2 T1-, T2-, and PD weighted imaging sequences were performed in that case study. Finally, a study comparing unenhanced CT, MR, and ultrasound for detection of manually placed wooden foreign bodies into canine cadavers showed that CT was the most accurate modality for detecting the foreign bodies overall.3 However, cadaveric studies don’t replicate the generally conspicuous surrounding tissue inflammation.
We present this case for the purpose of discussion regarding sequence selection. “Fishing expeditions” with MR can be very time consuming. This case is a perfect example of how we, as radiologists, may be asked to scan a large area of anatomy. Indeed, the T1 and T2-weighted images helped localize the foreign body. However, we were able to hone our region of interest from the initial thick sliced dorsal STIR images. Starting a study like this with large field of view STIR sequences gives us a global appreciation of anatomy to help localize any abnormalities. We use this approach in cases where multiple joints may be affected, neurolocalization is nebulous, or when searching for the small nerve sheath tumor. What do you do?
As a final note, frequency selected fat suppression (SPIR) was probably not a great selection for this case. Frequency selected fat suppression works best on linear structures and close to isocenter (which a large FOV neck is neither). Pure inversion recovery (STIR) is probably a better strategy for fat suppression. T1-weighted images without fat suppression would have been just fine and probably would have had better image quality. Live and learn.
- Young B, Klopp L, Albrecht M, et al. Imaging Diagnosis: MRI of a cervical wooden foreign body in a dog. Vet Radiol Ultrasound, 45:6, 2004, 538-41
- Hoyt L, Greenberg M, MacPhail C, et al. Imaging Diagnosis: MRI of an organizing abscess secondary to a retrobulbar grass awn. Vet Radiol Ultrasound, 50:6, 2009, 646-648.
- Ober CP, Jones JC, Larson MM, et al. Comparison of ultrasound, CT, and MRI in detection of acute wooden foreign bodies in the canine manus. Vet Radiol Ultrasound, 49:5, 2008, 411-18