CT-Guided Biopsy of Bone Lesions in Dogs and Cats

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• CT-guided bone biopsy is a minimally invasive technique for obtaining diagnostic samples from osseous lesions in dogs and cats, indicated for suspected neoplasia, osteomyelitis, or sterile inflammatory bone disease when imaging alone is insufficient.
• Precise needle placement is achieved through CT guidance, offering superior spatial resolution for targeting heterogeneous lesions and enabling sampling of the most biologically active regions, typically the periphery of lytic lesions.
• Jamshidi-type core biopsy needles (11-gauge for dogs, 13-gauge for cats/small dogs) are commonly used, with three to five samples recommended from different lesion areas, including transition zones, for histopathology and culture.
• Major complications include hemorrhage, fracture through the biopsy tract, iatrogenic neurovascular injury, infection, and nondiagnostic sampling, necessitating careful patient selection and post-procedure monitoring.
• Sample handling is critical, with core samples placed immediately in 10% neutral buffered formalin for histopathology and separate sterile samples submitted for aerobic and anaerobic culture to ensure diagnostic yield.
• Post-procedure care involves CT verification of the needle tract, radiographs to assess for fracture, analgesia, and monitoring for hemorrhage or neurologic deficits, with strict rest advised for weight-bearing bones.

Computed tomography-guided biopsy is a minimally invasive technique for obtaining diagnostic samples from osseous lesions in dogs and cats. This article describes the procedural framework for CT-guided bone biopsy, including patient selection, imaging protocols, needle selection, sampling technique, and sample handling. It serves the practicing veterinarian who has access to CT and who seeks a structured approach to diagnosing suspected neoplastic, infectious, or inflammatory bone disease without resorting to surgical biopsy.

The central clinical question addressed is how to obtain a diagnostic-quality bone specimen with acceptable morbidity and a defined complication profile. CT guidance offers superior spatial resolution of cortical and medullary bone compared with fluoroscopy or ultrasound, and it permits precise needle placement within a selected region of a heterogeneous lesion. The technique is applicable to the appendicular skeleton, the axial skeleton, and selected flat bones, although the approach and needle choice vary by location.

This article assumes familiarity with CT image interpretation, sterile surgical technique, and basic interventional principles. It does not cover radiographic diagnosis of bone lesions, nor does it describe open surgical biopsy techniques. Where the evidence base is limited, particularly regarding comparative diagnostic yield across needle types in veterinary patients, this is stated explicitly.

At a Glance

Rationale for CT Guidance in Bone Biopsy

Percutaneous biopsy of bone lesions can be performed under fluoroscopic, ultrasound, or CT guidance. CT offers three-dimensional localization of the lesion, precise measurement of the distance from skin to periosteum, and direct visualization of the needle within the bone during acquisition. This is particularly valuable for lesions of the axial skeleton, where overlying soft tissue and critical structures limit the safety of blind or fluoroscopic approaches.

The accuracy of CT-guided needle placement has been documented in veterinary stereotactic systems. In a series of 50 dogs undergoing CT-guided brain biopsy using a modified stereotactic frame, mean needle placement error was 3.5 mm, and error was not significantly related to operator experience, body weight, or needle path length, although lesion location did affect accuracy. While that study addressed intracranial biopsy, the principle of CT-based targeting accuracy applies to musculoskeletal sampling, and it supports the use of CT when millimeter-level precision is required.

CT guidance also permits sampling of the most biologically active region of a lesion. Bone lesions are often heterogeneous, with areas of necrosis, hemorrhage, reactive bone, and viable neoplastic tissue. Selecting the target region on the basis of CT characteriztics, such as the most aggressive periosteal reaction or the least mineralized medullary component, improves the likelihood of obtaining diagnostic tissue.

Patient Selection and Preparation

Indications

CT-guided bone biopsy is indicated when a definitive diagnosis cannot be made from imaging alone and when the result will alter treatment. Typical indications include solitary or multiple lytic bone lesions, aggressive periosteal reactions, pathologic fractures with an unidentified underlying process, and suspected osteomyelitis that has not responded to empirical antimicrobial therapy. The technique is also used to confirm suspected metastatic disease before staging or treatment decisions.

Contraindications and Risk Assessment

Uncorrectable coagulopathy is a relative contraindication. A platelet count and coagulation profile should be assessed before the procedure, particularly for lesions of the axial skeleton or when the biopsy tract passes through vascular soft tissue. The risk of iatrogenic fracture must be weighed against the diagnostic benefit, especially in weight-bearing bones with extensive cortical lysis. In such cases, the biopsy tract should be placed to minimize stress riser effects, and the limb should be protected after sampling.

The patient's respiratory motion must be considered. General anesthesia with controlled ventilation allows the operator to pause respiration during needle advancement, which is essential for lesions of the ribs, sternum, or vertebrae. The American College of Veterinary Radiology provides professional resources on imaging practice and radiation safety that are relevant to planning interventional procedures, and these should be consulted for facility-specific protocols.

Imaging Protocol and Target Selection

A helical CT study of the affected bone is performed before biopsy. Thin slices, typically 1 to 2 mm, are acquired through the lesion using both bone and soft tissue reconstruction algorithms. Intravenous contrast is administered when there is suspected soft tissue extension, a surrounding abscess, or a need to distinguish the lesion from adjacent vascular structures.

Target selection follows a defined logic. The center of a lytic lesion is often necrotic and may yield nondiagnostic material. The periphery of the lesion, where active tumor or inflammation abuts normal bone, is more likely to contain diagnostic cells. When a lesion has both lytic and blastic components, the lytic region is generally preferred because it is softer and easier to penetrate, and it more often contains viable tissue. The biopsy tract should traverse the shortest safe path from skin to bone, avoiding major vessels, nerves, and joint spaces.

The planned trajectory is reviewed on the CT console in axial, sagittal, and dorsal planes. The entry point, angle, and depth are recorded, and a radiopaque marker or grid is placed on the skin to align the needle with the planned path. The distance from skin to periosteum is measured, and the depth of the lesion within the bone is estimated to determine the required needle length.

Needle Selection and Instrumentation

The choice of biopsy needle depends on lesion location, bone density, and the volume of tissue required for histopathology, culture, or ancillary testing. For lytic lesions with cortical destruction, a soft tissue biopsy needle such as a Tru-Cut or Temno device may suffice, as the needle can pass through the disrupted cortex into the medullary cavity. For sclerotic or intramedullary lesions with an intact cortex, a bone biopsy needle with a serrated cutting tip and stylet is required.

Jamshidi needles are the most commonly used bone biopsy instruments in small animal practice. They are available in 8, 11, and 13 gauge sizes and produce a core sample approximately 1 to 2 cm in length. The 11 gauge needle is a reasonable default for most appendicular and axial lesions in dogs, while the 13 gauge is better suited to cats and small dogs. For larger dogs or lesions requiring substantial tissue for culture and histopathology, an 8 gauge needle may be appropriate, although the larger diameter increases the risk of fracture through the biopsy tract.

Trephine needles, such as the Michele trephine, are reserved for very dense cortical bone. They require a twisting motion for advancement and carry a higher risk of thermal injury to the sample if excessive speed generates heat. For flat bones such as the ilium, scapula, or ribs, an 11 gauge Jamshidi needle is usually adequate.

Needle length should be selected so that at least 2 to 3 cm of the needle remains outside the patient when the tip is at the target. This allows for computed tomography (CT) confirmation of needle position before sampling and provides leverage for the biopsy stroke. Longer needles are more prone to deflection, particularly when passing through dense cortical bone at an angle.

The following table summarizes needle selection criteria:

Positioning and Approach Planning

Patient positioning is determined by the lesion location and the shortest safe path from skin to bone. The patient is placed in dorsal, ventral, or lateral recumbency depending on the target. The limb or body region of interest should be positioned so that the planned needle path avoids major neurovascular structures, joint spaces, and the thoracic or abdominal cavities.

A planning CT study is acquired before needle placement. Thin slices, typically 1 to 2 mm, are recommended through the region of interest. The CT images are used to select the skin entry point, the angle of approach, and the target site within the lesion. The target should be the most diagnostic region of the lesion, which is usually the periphery of a lytic lesion where viable neoplastic cells are more likely to be present. The center of a large lytic lesion often contains necrotic debris, hemorrhage, or reactive fibrous tissue that yields a nondiagnostic sample.

The needle path should be planned to traverse the shortest distance through normal tissue while avoiding critical structures. For appendicular lesions, a direct approach through the thinnest portion of the overlying soft tissue envelope is preferred. For axial lesions, the approach may need to be angled to avoid the spinal cord, major vessels, or the pharynx. CT fluoroscopy, where available, allows real-time confirmation of needle position during advancement. In its absence, intermittent CT images are obtained after each incremental advancement of the needle.

Biopsy Technique

The skin over the entry site is clipped and aseptically prepared. A small stab incision is made with a number 11 scalpel blade to facilitate passage of the biopsy needle through the skin and subcutaneous tissue. The needle with stylet in place is advanced to the periosteum under CT guidance. The stylet is removed once the needle tip contacts the cortex, and the needle is advanced into the bone using a steady twisting or pushing motion.

For Jamshidi needles, the needle is advanced 1 to 2 cm into the lesion. The needle is then rotated 360 degrees to detach the core from the surrounding bone before withdrawal. The sample is expelled from the needle using the stylet, taking care to handle the core gently to avoid crush artefact. The sample is placed immediately into 10% neutral buffered formalin for histopathology. If osteomyelitis is suspected, a second sample should be obtained and placed in a sterile container for aerobic and anaerobic culture.

Multiple samples are often required to achieve a diagnostic yield. Two to three cores from different regions of the lesion are generally recommended. For lytic lesions, sampling the peripheral rim of viable tissue and the transition zone between normal and abnormal bone improves the diagnostic yield. For sclerotic lesions, the densest region may be sampled, although the yield of neoplastic cells is often lower in densely mineralised tissue.

After the biopsy, the needle tract is not routinely closed. Pressure is applied to the skin entry site for several minutes to control hemorrhage. A single skin suture may be placed if the incision is larger than the needle diameter.

Sample Handling and Diagnostic Yield

The quality of the sample determines the diagnostic value of the procedure. Bone biopsy cores are fragile and easily crushed during handling. The core should be expelled from the needle by inserting the stylet from the cutting end and pushing the sample out through the hub, instead of by grasping the sample with forceps. The sample should be placed on a piece of sterile gauze or paper to allow orientation before immersion in fixative.

Decalcification is required before paraffin embedding of bone samples. This process can take several days and may affect the quality of immunohistochemistry. The pathologist should be informed that the sample is from a bone lesion so that appropriate decalcification protocols are used. Molecular testing, such as polymerase chain reaction for infectious agents, may be performed on a separate sample that is frozen or placed in a specific transport medium.

The diagnostic yield of CT-guided bone biopsy in small animals is generally high, but nondiagnostic samples occur. Causes of nondiagnostic samples include sampling of necrotic or hemorrhagic tissue, failure to penetrate dense cortical bone, and excessive crush artefact. If the sample is nondiagnostic, the procedure may be repeated with a different target site or a larger needle. The risk of complications from a second biopsy is low, and the benefit of a definitive diagnosis usually outweighs the additional risk.

Monitoring and Aftercare

Patients are monitored for complications during and after the procedure. The most common complications are hemorrhage, fracture through the biopsy site, and inadvertent damage to adjacent structures. Hemorrhage is usually minor and self-limiting, but significant bleeding can occur if a major vessel is punctured. The CT images obtained after needle removal should be reviewed for evidence of hemorrhage, such as a new soft tissue opacity along the needle tract.

Pathologic fracture through the biopsy site is a recognized complication, particularly in lytic lesions of weight-bearing bones. The risk is highest in the femur and tibia of large dogs. The biopsy tract creates a stress riser in bone that is already weakened by the lesion. Patients should be strictly rested for 24 to 48 hours after the procedure, and the limb should be bandaged or supported if the lesion involves a weight-bearing bone. Owners should be advised to restrict activity for 7 to 10 days to allow the biopsy tract to begin healing.

Neurologic deficits can occur after biopsy of vertebral or paravertebral lesions. The risk is reduced by careful planning of the needle path and by using CT guidance to confirm needle position before advancement. If a neurologic deficit is detected after the procedure, immediate imaging is indicated to assess for hemorrhage or needle tract injury.

Analgesia is provided as needed for post-procedural discomfort. Most patients require only mild sedation or a short course of nonsteroidal anti-inflammatory drugs. The use of analgesic agents should follow current formulary and label references, and the choice of agent should account for the patient's renal and hepatic status.

Documentation and Reporting

The procedure report should include the patient identification, the lesion location and imaging characteriztics, the needle type and gauge, the number of samples obtained, the target site, and any complications encountered. The CT images showing the needle tip at the target site should be archived as part of the permanent medical record. The report should also state the destination of each sample, such as histopathology, culture, or molecular testing.

Communication with the pathologist is essential. The pathologist should receive a summary of the imaging findings, the suspected differential diagnosis, and the specific questions the biopsy is intended to answer. This information allows the pathologist to select appropriate stains and ancillary tests. The referring veterinarian and the owner should be informed of the procedure outcome and the expected timeline for results.

The use of robotic assistance for needle placement has been described in human interventional radiology, with systems designed for CT and MRI guidance offering stable needle positioning and access to lesions that are difficult to reach within the gantry robotic systems for percutaneous needle-guided interventions. Similar systems are not yet widely available in veterinary practice, but the principles of accurate needle placement and confirmation of tip position before sampling apply equally to manual techniques. The accuracy of CT-guided needle placement in veterinary patients has been documented in stereotactic brain biopsy, where mean needle placement error was 3.5 mm in a series of 50 dogs CT-guided stereotactic brain biopsy in dogs. This level of accuracy is acceptable for most bone lesions, where the target is typically larger than an intracranial lesion.

Professional guidance on imaging standards and radiation safety in veterinary practice is available from the American College of Veterinary Radiology ACVR professional resources. Practitioners should ensure that their CT biopsy protocols comply with current radiation safety recommendations and that personnel are appropriately trained in CT-guided interventional techniques.

Complications and Failure Modes

Hemorrhage is the most common clinically significant complication of CT-guided bone biopsy. Bleeding usually originates from the periosteal vessels or the nutrient artery of the affected bone. Early detection relies on serial CT images obtained immediately after needle withdrawal, comparing the pre-biopsy and post-biopsy series for new soft tissue swelling, joint effusion, or retroperitoneal fluid accumulation. Most hemorrhage is self-limiting, but substantial bleeding can occur when the biopsy tract crosses a major vessel or when the lesion is highly vascular. Patients with thrombocytopenia or coagulopathy should have a platelet count and coagulation profile reviewed before the procedure, and the biopsy should be deferred if values fall below the laboratory reference interval.

Pneumothorax is a recognized complication when sampling lesions of the ribs, sternum, or proximal humerus. The pleural space can be entered even when the needle path appears extrapleural on planning images, particularly in thin patients where the visceral pleura lies close to the inner rib cortex. Post-procedural CT through the thorax, or at minimum a targeted image series over the biopsy site, will identify small pneumothoraces before clinical signs develop. A tension pneumothorax requires immediate thoracocentesis or chest drain placement.

Nerve injury is uncommon but can occur when sampling the vertebral bodies, sacrum, or proximal femur. The sciatic nerve, femoral nerve, and spinal nerve roots lie close to these targets. Patients should be assessed for new pelvic limb paresis, proprioceptive deficits, or signs of pain on limb manipulation in the recovery period. Needle tract seeding of neoplastic cells is a theoretical concern with aggressive sarcomas, although the reported incidence is low. The biopsy tract should be planned so that it can be excised en bloc if a subsequent curative resection is performed.

Pathological fracture through the biopsy site is a rare but serious complication. It is more likely in lytic lesions of the appendicular skeleton that already compromise cortical integrity. The biopsy should be planned to avoid creating a stress riser, and the limb should be supported during recovery. Serial radiographs or CT at the recheck examination will identify progressive cortical thinning or fissure formation.

Common Errors and Corrective Actions

The most frequent error in CT-guided bone biopsy is selecting a target that is not representative of the lesion. Sclerotic bone often yields insufficient material, while necrotic or cystic regions produce acellular debris. The biopsy should target the most aggressive margin of the lesion, typically the interface between abnormal and normal bone, where viable neoplastic cells are most concentrated. Reviewing the pre-contrast and post-contrast images before needle placement will identify enhancing regions that are more likely to yield diagnostic tissue.

Inadequate needle length is a common planning error. The needle must be long enough to traverse the soft tissue and reach the bone surface with the stylet fully seated. A needle that is too short forces the operator to angle the approach, which increases the risk of skiving along the cortex and displacing the target. The needle path should be measured on the planning images and the needle length confirmed before the patient is positioned.

Skiving, where the needle tip slides along the bone surface instead of engaging the cortex, occurs when the approach angle is too shallow. The needle should enter the bone at an angle as close to perpendicular as the anatomy allows. If the needle skives, it should be withdrawn and repositioned instead of forced, as repeated attempts create a wider periosteal defect and increase hemorrhage.

Students and less experienced clinicians often underestimate the importance of patient positioning. A slight rotation of the patient between the planning scan and the biopsy can shift the target by several millimetres. The position should be verified with a localizer image immediately before needle placement, and the table coordinates should be rechecked against the planning images.

Limitations of the Evidence and Areas of Disagreement

The veterinary literature on CT-guided bone biopsy consists largely of case series and expert opinion instead of prospective comparative trials. There is no published consensus on the optimal needle type, gauge, or number of cores for specific bone lesions in dogs and cats. Some operators favour trephine needles for dense cortical bone, while others report comparable diagnostic yield with Jamshidi needles. The choice is often based on personal experience and the specific characteriztics of the lesion.

The role of robotic-assisted needle placement in veterinary practice remains undefined. Robotic systems for CT-guided interventions have been developed and tested in human medicine, with reported accuracy that is acceptable for clinical use, but these systems have not been evaluated in veterinary patients MRI-safe robot for endorectal prostate biopsy. The cost and complexity of these systems currently limit their application to research settings interventional robotic systems and their applications.

Expert opinion differs on the management of suspected osteomyelitis. Some clinicians recommend empirical antimicrobial therapy before biopsy results are available, while others prefer to withhold antibiotics until culture and susceptibility results are obtained. The latter approach avoids the risk of false-negative cultures but delays treatment in patients with confirmed infection. The decision should be made on a case-by-case basis, considering the patient's clinical status and the likelihood of sepsis.

Referral and Escalation

Referral to a veterinary radiologist or a specialty center should be considered when the lesion is located in an anatomically complex region, such as the vertebral bodies, skull, or sacrum, where the risk of iatrogenic injury is high. Patients with suspected pathological fracture, significant hemorrhage, or neurological signs after the procedure should be referred for further evaluation and management.

Laboratory involvement is required when the biopsy specimen is insufficient for diagnosis, when cultures are requested, or when histopathology results are discordant with the imaging findings. The laboratory should be contacted before the procedure to confirm the required sample handling and transport conditions. Regulatory reporting may be required if the biopsy reveals a notifiable disease, and the local veterinary authority should be consulted in accordance with WOAH terrestrial animal health standards. Professional guidance on biopsy complications and patient safety is available from American College of Veterinary Radiology resources and American Veterinary Medical Association practice resources.

Frequently Asked Questions

What is the minimum CT hardware and software needed to perform CT-guided bone biopsy safely?

A helical or multi-slice CT scanner with at least 16 detector rows is practical for most appendicular and axial bone lesions. You need a laser localizer for slice positioning, a table capable of precise incremental movement, and software that displays slice coordinates. Standard bone and soft tissue reconstruction algorithms are sufficient. For most practices, a single-slice scanner can work but requires more manual table positioning and longer procedure times. The limiting factor is usually gantry aperture and table clearance when the patient is positioned for a dorsal or oblique approach. Review the American College of Veterinary Radiology resources for equipment standards and quality assurance expectations before establishing this service.

How should I proceed when a CT-guided biopsy is indicated but the practice lacks CT capability?

Referral is the safest option when CT is unavailable. Transport the patient with the lesion already radiographed and, ideally, with a prior CT study on disk. The receiving facility will need the complete signalment, lesion location, and any prior cytology or histopathology. If referral is declined for financial or logistical reasons, ultrasound-guided biopsy is a reasonable alternative for lytic lesions with cortical disruption and a soft tissue component, but it carries a higher risk of nondiagnostic sampling for sclerotic or intramedullary lesions. The MSD Veterinary Manual provides general guidance on biopsy principles and sample handling that applies across imaging modalities.

What are the cost considerations that should be discussed with owners before the procedure?

The major cost drivers are the CT study itself, anesthesia time, biopsy needles, and histopathology. Core biopsy needles are single-use and can cost substantially more than standard hypodermic needles. Histopathology with decalcification adds several days and a separate laboratory fee. Owners should also be quoted for potential complications, including fracture through a lytic lesion, hemorrhage, and infection, each of which may require additional hospitalization. A written estimate should separate imaging, procedure, anesthesia, and pathology charges. The American Veterinary Medical Association practice resources offer guidance on informed consent and fee transparency that can help structure these discussions.

How does the biopsy approach differ between dogs and cats?

Cats have thinner cortices and smaller medullary cavities, so a smaller gauge needle, typically 14 gauge or less, is preferred to reduce fracture risk. Feline bone is more prone to iatrogenic fracture during needle manipulation, particularly in the distal radius and tibia. Cats also have a higher prevalence of primary bone neoplasia relative to metastatic disease, which may influence the number of cores taken. The axial skeleton in cats is smaller, so the distance from skin to lesion is shorter, but the margin for error in angle deviation is correspondingly tighter. Recovery from anesthesia is generally faster in cats, but they require more careful analgesia monitoring after the procedure.

What documentation is required in the medical record after a CT-guided bone biopsy?

The record must include the indication, the CT protocol, the exact coordinates and angle of each needle pass, the needle type and gauge, the number of cores, and the appearance of the samples. Record the target lesion dimensions, the distance from skin to lesion, and any deviation from the planned trajectory. Note the anesthetic events, including any changes in heart rate or blood pressure during needle placement. Document the post-procedure CT images and any complications observed. The pathology submission form should include the lesion location, the imaging differentials, and the decalcification request. The WOAH terrestrial animal health standards provide a framework for traceability that applies to laboratory sample documentation.

What should I tell the referring veterinarian when the histopathology result is nondiagnostic?

Explain that nondiagnostic results occur in a measurable proportion of CT-guided bone biopsies, particularly for sclerotic lesions, small lesions, or those with extensive necrosis. The sample may contain only reactive bone, fibrous tissue, or blood. Offer a clear plan: review the original CT images to confirm the needle trajectory, consider a repeat biopsy with a larger gauge needle or a different approach, or proceed to surgical biopsy if the lesion is accessible. If the clinical and imaging features strongly suggest neoplasia, a nondiagnostic result does not exclude malignancy. The MSD Veterinary Manual notes that repeat sampling is often required when the first attempt yields inadequate tissue.

Related Clinical & Scientific Guides

• MRI Monitoring of Brain Tumor Response to Therapy in Dogs
• Ultrasound-Guided Drainage of Abscesses in Small Animals
• Radiographic Monitoring of Total Hip Replacement in Dogs

References and Further Reading

• Needle-shaped ultrathin piezoelectric microsystem for guided tissue targeting via mechanical sensing.. 2018.
• Sonographically guided microwave coagulation treatment of liver cancer: an experimental and clinical study.. 1998.
• Interventional robotic systems: applications and technology state-of-the-art.. 2006.
• MRI-Safe Robot for Endorectal Prostate Biopsy.. 2013.
• Robotic systems for percutaneous needle-guided interventions.. 2015.
• Modification and application of a Pelorus Mark III stereotactic system for CT-guided brain biopsy in 50 dogs.. 1999.
• American College of Veterinary Radiology Resources. American College of Veterinary Radiology.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

Related Articles

• CT-Guided Biopsy of Thoracic and Abdominal Lesions in Dogs and Cats
• Ultrasound-Guided Cystocentesis for Therapeutic Drainage in Dogs and Cats
• CT-Guided Stereotactic Radiosurgery Planning for Brain Tumors in Dogs
• Radiographic Monitoring of Pacemaker Implantation in Dogs
• Ultrasound-Guided Aspiration of Cystic Lesions in Small Animals

This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.