# CT-Guided Biopsy of Thoracic and Abdominal Lesions in Dogs and Cats ## Key Takeaways - CT-guided biopsy is indicated for thoracic or abdominal lesions when ultrasound guidance is inadequate or contraindicated, offering superior visualization of lesions obscured by bone or gas, or those requiring precise needle placement. - Combining fine-needle aspiration (FNA) for cytology with tissue-core biopsy (TCB) for histopathology significantly improves diagnostic accuracy, achieving up to 98.4% for thoracic masses, compared to either method alone (cytology ~69%, histopathology ~95%). - Careful pre-procedural assessment, including coagulation testing, and meticulous needle path planning to avoid major vascular and airway structures are critical for minimizing complications such as pneumothorax and hemorrhage. - Common complications include pneumothorax (up to 26% in one series, often mild and self-limiting) and hemorrhage, necessitating immediate post-biopsy imaging and appropriate monitoring and intervention protocols. - Needle selection is crucial: 22-25 G needles are used for cytology (FNA), while 18-20 G automated devices are used for histopathology (TCB), with sample handling tailored to the intended diagnostic method (air-dried smears for cytology, formalin for histopathology). - Anesthetic management requires controlled ventilation, including apneic holds to eliminate respiratory motion artifact during needle advancement, particularly for thoracic lesions. --- Computed tomography-guided biopsy provides a precise, minimally invasive method for obtaining cytologic and histopathologic samples from thoracic and abdominal lesions in dogs and cats. This article addresses the procedural framework for CT-guided sampling, including patient selection, imaging protocols, needle selection, tissue acquisition technique, and complication management. It is written for practicing veterinarians who have access to CT and who seek a structured approach to percutaneous sampling when ultrasound guidance is inadequate or contraindicated. The clinical question this article answers is straightforward: when a thoracic or abdominal lesion is identified on CT, how does the operator plan and execute a safe, diagnostically productive biopsy? The answer depends on lesion location, proximity to vascular and airway structures, patient respiratory motion, and the expected diagnostic yield of cytology versus histopathology. CT-guided fine-needle aspiration and tissue-core biopsy are complementary techniques, and their combined use improves diagnostic accuracy compared with either method alone. In one series of 62 dogs and cats with thoracic masses, combined fine-needle aspiration and tissue-core biopsy achieved an overall diagnostic accuracy of 98.4%, whereas histopathology alone was diagnostic in 95.2% of cases and cytology alone in 69.4% [CT-guided fine needle aspiration and tissue-core biopsy of thoracic masses in the dog and cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). CT guidance offers distinct advantages over fluoroscopic or ultrasound-guided sampling. CT provides cross-sectional anatomic detail that permits avoidance of major vessels, bronchi, and other critical structures. It also allows sampling of lesions that are obscured by bone, gas, or overlying soft tissue, and it enables accurate needle placement in lesions that are small, deeply located, or poorly visualized with other modalities. The technique is applicable to both thoracic and abdominal targets, and the same fundamental principles of image acquisition, needle selection, and sample handling apply across body regions. ## At a Glance | Parameter | Consideration | |---|---| | Primary indications | Thoracic or abdominal lesions requiring cytologic or histopathologic diagnosis when ultrasound guidance is not feasible | | Contraindications | Uncorrectable coagulopathy, severe respiratory compromise, inaccessible lesion, lack of a safe needle path | | Imaging protocol | Pre- and post-contrast CT, thin slices through the lesion, lung window for thoracic targets | | Needle types | Fine-needle aspiration (22-25 G) for cytology, tissue-core biopsy (18-20 G) for histopathology | | Sample handling | Air-dried smears for cytology, formalin fixation for histopathology, culture media if infection suspected | | Common complications | Pneumothorax, pulmonary hemorrhage, hemoptysis, hemoperitoneum | | Diagnostic yield | Combined FNA and core biopsy approximately 98% for thoracic masses in one series | | Post-procedure monitoring | Serial thoracic radiographs or CT for pneumothorax, ultrasound for abdominal hemorrhage | ## Scientific Basis of CT-Guided Sampling ### Diagnostic Yield of Cytology Versus Histopathology The diagnostic value of CT-guided biopsy depends on the sampling method and the nature of the target lesion. Fine-needle aspiration yields cellular material for cytologic evaluation, which is rapid and inexpensive but limited by sample cellularity and the interpreter's ability to diagnose on cytomorphology alone. Tissue-core biopsy provides architecturally intact samples that permit histopathologic diagnosis, including immunohistochemistry when needed. The two methods are not interchangeable, and their diagnostic performance differs measurably. In the thoracic mass series cited above, cytology from CT-guided fine-needle aspiration was diagnostic in 69.4% of cases, while tissue-core biopsy was diagnostic in 95.2%. The sensitivity of cytology was 67.7% and that of core biopsy was 96.7%, with positive predictive values of 100% and 98.3%, respectively. Combining both techniques raised overall accuracy to 98.4% [CT-guided fine needle aspiration and tissue-core biopsy of thoracic masses in the dog and cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). These figures support a dual-sampling strategy whenever the lesion is large enough and safely accessible for both procedures. ### CT Characteriztics of Target Lesions The CT appearance of a lesion informs both the differential diagnosis and the biopsy approach. Thoracic neoplasia in cats frequently appears as a lobar hyperdensity that may involve the main bronchus, invade the mediastinum, or cross to the contralateral lung [computed tomography in the diseased feline thorax](https://pubmed.ncbi.nlm.nih.gov/12622469/). Such lesions are often amenable to CT-guided sampling, although the presence of associated atelectasis or mediastinal shift must be accounted for during needle planning. Muscular metastatic lesions, which may be encountered during whole-body CT staging, show characteriztic post-contrast patterns including ring enhancement, heterogeneous enhancement, or homogeneous enhancement [whole body CT characteriztics of skeletal and cardiac muscular metastatic neoplasia in dogs and cats](https://pubmed.ncbi.nlm.nih.gov/23441584/). These lesions are typically well-demarcated and oval to round, and they can be sampled with CT guidance when they are identified incidentally or when confirmation of metastatic disease is required for staging decisions. ### Limitations of Alternative Guidance Modalities Ultrasound-guided biopsy is often the first-line sampling method for thoracic and abdominal lesions because it is widely available, inexpensive, and does not involve ionizing radiation. However, ultrasound has important limitations. Air-filled lung parenchyma reflects the ultrasound beam, making intrapulmonary lesions inaccessible unless they abut the pleural surface or are surrounded by consolidated lung. Similarly, lesions deep within the abdomen may be obscured by gas-filled bowel loops. Ultrasound-guided thoracic sampling has been reported to yield diagnostic samples in approximately 91% of cases in one series of 75 dogs and cats [non-cardiac thoracic ultrasound in 75 feline and canine patients](https://pubmed.ncbi.nlm.nih.gov/10779076/), but this figure reflects a selected population of lesions that were visible ultrasonographically. Contrast-enhanced thoracic ultrasound has been investigated as a means of improving biopsy targeting, but the evidence base remains limited and heterogeneous [clinical applications of contrast-enhanced thoracic ultrasound compared to standard reference tests](https://pubmed.ncbi.nlm.nih.gov/32259873/). CT guidance overcomes many of these limitations by providing a complete, three-dimensional view of the lesion and its surrounding structures. ## Patient Selection and Pre-Procedural Assessment ### Indications CT-guided biopsy is indicated when a thoracic or abdominal lesion requires tissue diagnosis and ultrasound guidance is not feasible or has failed. Specific indications include intrapulmonary nodules or masses that do not contact the pleura, lesions obscured by bone or gas, small lesions requiring precise needle placement, and lesions in patients where a concurrent CT study has already been performed for staging or surgical planning. CT guidance is also valuable for sampling multiple lesions during a single anesthetic episode, as the entire thorax or abdomen can be imaged and each target can be approached systematically. ### Contraindications and Risk Assessment Absolute contraindications to CT-guided biopsy are uncommon but include uncorrectable coagulopathy and the absence of a safe needle path. Relative contraindications include severe respiratory compromise, where even a small pneumothorax may be poorly tolerated, and lesions that are intimately associated with major vascular structures where hemorrhage would be catastrophic. The operator must weigh the diagnostic benefit of sampling against the risk of complications in each individual patient. Pre-procedural assessment should include a complete blood count, serum biochemistry profile, and coagulation testing when clinically indicated. Platelet count and function are particularly relevant, as thrombocytopenia or thrombopathia increases the risk of hemorrhage. ### Anesthetic Considerations General anesthesia is required for CT-guided biopsy in dogs and cats. The anesthetic protocol must account for the need to control ventilation during needle placement. Apneic holds, during which the ventilator is paused for 15 to 30 seconds, are used to eliminate respiratory motion artifact and to stabilize the target lesion during needle advancement. This technique is especially important for thoracic lesions, where diaphragmatic and chest wall motion can shift the target by several millimeters between image acquisitions. The anesthetic plan should also include provisions for rapid recovery and monitoring for complications such as pneumothorax or hemorrhage. ## Imaging Protocol and Procedural Planning ### Image Acquisition The CT protocol begins with a helical acquisition through the region of interest. Slice thickness should be 1 to 3 mm for thoracic lesions and 2 to 5 mm for abdominal lesions, with thinner slices preferred for small targets. Both pre- and post-contrast images should be obtained when the lesion's vascularity or relationship to adjacent vessels is relevant to biopsy planning. Post-contrast imaging is particularly useful for identifying necrotic or cystic regions within a lesion that should be avoided during sampling, as these areas often yield non-diagnostic material. Images should be reviewed in multiple window settings. Lung windows are essential for thoracic lesions, as they delineate the pulmonary parenchyma and allow identification of the needle path through aerated lung. Soft tissue windows are used for mediastinal, chest wall, and abdominal targets. The operator must identify the lesion, determine its exact location relative to the skin surface, and plan a needle trajectory that avoids major vessels, bronchi, and other critical structures. ### Needle Path Planning The needle path is planned on the CT images before the patient is positioned for biopsy. The shortest path from skin to lesion is not always the safest path. The trajectory must avoid interposed lung fissures, large pulmonary vessels, the heart, and the great vessels in the thorax, and it must avoid the gallbladder, major abdominal vessels, and hollow viscera in the abdomen. An extrapleural or extraperitoneal approach may be preferable in some cases, even if it requires a longer needle path, because it reduces the risk of pneumothorax or peritoneal contamination. The planned trajectory should be marked on the skin with the patient in the same position used for the CT acquisition. Radiolucent markers, such as a grid or a radiopaque catheter taped to the skin, can be used to correlate the CT coordinates with the external anatomy. The depth from skin to lesion is measured on the CT images, and the needle is advanced to that depth in a single pass whenever possible. Multiple passes through the same tract increase the risk of hemorrhage and pneumothorax. ## Needle Selection and Sample Handling The choice of needle determines both diagnostic yield and complication profile. For thoracic lesions, fine-needle aspiration (FNA) using 22 to 25 gauge needles provides cytologic material with a lower risk of hemorrhage and pneumothorax, while tissue-core biopsy (TCB) using 18 to 20 gauge automated biopsy devices yields histopathologic samples with higher diagnostic accuracy. In a study of 62 dogs and cats undergoing CT-guided thoracic sampling, histopathology was diagnostic in 95.2% of samples compared with 69.4% for cytology, and the combination of both techniques achieved an overall accuracy of 98.4% [Clinical Value of CT-Guided Fine Needle Aspiration and Tissue-Core Biopsy of Thoracic Masses in the Dog and Cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). The same study reported a 30.6% complication rate, with mild pneumothorax accounting for 16 of 19 complications. | Needle Type | Gauge Range | Sample Type | Best Indications | Limitations | |---|---|---|---|---| | Spinal needle | 22 to 25 | Cytology | Small or deeply located lesions, lesions adjacent to vessels | Limited architectural information | | Chiba needle | 22 | Cytology | Soft tissue and mediastinal masses | May deflect in fibrous tissue | | Tru-Cut automated biopsy needle | 18 to 20 | Histopathology | Solid masses, suspected lymphoma, sarcoma, or carcinoma | Higher hemorrhage risk, requires larger target | | Coaxial introducer needle | 17 to 19 | Access sheath | Multiple sampling through one pleural puncture | Larger pleural defect, increased pneumothorax risk | | Menghini aspiration needle | 18 to 20 | Histopathology | Pulmonary parenchymal lesions | Sample fragmentation possible | Sample handling differs by technique. Cytologic smears should be prepared immediately from FNA material, air-dried, and stained with Romanowsky-type stains. Fluid aspirates should be collected into EDTA tubes for cell counts and cytocentrifugation. Tissue cores should be gently rolled on a glass slide for impression cytology before placement in 10% neutral buffered formalin. If infection is suspected, a second core should be placed in a sterile container without fixative for aerobic and anaerobic culture. Lesions with suspected endocrine or mast cell neoplasia may require special handling, including electron microscopy fixative or rapid fixation protocols, so the laboratory should be consulted before the procedure when such diagnoses are considered. ## Thoracic Biopsy Technique Patient positioning depends on lesion location. Sternal recumbency is preferred for dorsal and central pulmonary lesions, while lateral recumbency allows access to peripheral lesions and reduces the distance from the skin surface to the target. The planned needle path should avoid the heart, great vessels, bronchi, and intercostal vessels that run along the caudal border of each rib. A coaxial technique, in which an introducer needle is advanced to the lesion margin and the biopsy device is passed through it, reduces the number of pleural punctures and is recommended when multiple samples are required. The skin is clipped and aseptically prepared over the planned entry site. A small stab incision facilitates needle passage. The needle is advanced in increments of 5 to 10 mm with repeat CT images confirming tip position relative to the lesion. Respiratory motion can displace the target, particularly for lesions in the caudal lung lobes, so imaging should be acquired during the same phase of respiration for planning and needle confirmation. Apneic ventilation during general anesthesia, if available, markedly improves accuracy. After needle removal, a final CT scan through the thorax is performed to assess for pneumothorax, pulmonary hemorrhage, or pleural effusion. Mild pneumothorax may be managed conservatively with oxygen supplementation and monitoring. Larger pneumothoraces, or those causing respiratory compromise, require thoracocentesis or temporary chest tube placement. In the study of 62 thoracic biopsies, all 16 cases of mild pneumothorax were managed without surgical intervention [Clinical Value of CT-Guided Fine Needle Aspiration and Tissue-Core Biopsy of Thoracic Masses in the Dog and Cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). ## Abdominal Biopsy Technique Abdominal CT-guided biopsy follows the same general principles but with different risk considerations. The needle path must avoid the stomach, intestines, gallbladder, and major abdominal vessels. For hepatic lesions, a right-sided approach through the intercostal space or a ventral approach may be used depending on the lobe affected. Renal biopsies are typically performed with the patient in lateral recumbency, sampling the caudal pole to avoid the renal hilus and medulla. Adrenal masses require careful assessment of the relationship to the caudal vena cava and aorta, and a dorsal approach may be necessary for pheochromocytomas or masses with vascular invasion. Splenic lesions are often accessible through a ventral approach, but the spleen is mobile and may move with respiration. The needle path should traverse a margin of normal splenic tissue before entering the lesion to reduce the risk of capsular tearing. Gastrointestinal wall lesions are sampled with caution because full-thickness penetration can cause peritonitis. When a gastrointestinal mass is suspected, the needle path should be planned to enter the lesion tangentially, and the sample should be obtained from the thickened wall instead of the lumen. For abdominal procedures, the complication profile differs from thoracic sampling. Hemorrhage is the primary concern, particularly for hepatic, renal, and adrenal lesions. Coagulation status should be assessed before biopsy, and patients with thrombocytopenia, prolonged clotting times, or suspected disseminated intravascular coagulation should be managed with appropriate blood product support before sampling. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides reference ranges and interpretation guidance for coagulation testing in dogs and cats. Post-biopsy CT imaging should be evaluated for contrast extravasation or peritoneal fluid accumulation. ## Monitoring and Complication Management | Parameter | Detection Target | Action Threshold | Response | |---|---|---|---| | SpO₂ | Hypoxemia from pneumothorax or hemorrhage | Below 94% | Supplemental oxygen, thoracic imaging, thoracocentesis if indicated | | End-tidal CO₂ | Ventilation-perfusion mismatch | Rising or falling trend | Assess airway, consider chest drain | | Invasive or oscillometric blood pressure | Hemorrhagic shock | Mean below 60 mm Hg | Fluid resuscitation, blood products, surgical consultation | | Heart rate and rhythm | Pain, hemorrhage, vagal response | Tachycardia or bradycardia | Analgesia, vagolytic if bradycardic, hemorrhage assessment | | Capillary refill time and mucous membrane color | Hypovolemia | Prolonged CRT, pale membranes | Fluid therapy, reassess blood loss | | Respiratory rate and pattern | Pneumothorax, pleural effusion | Tachypnea, restrictive pattern | Thoracic ultrasound or CT, drainage | Patients should be monitored for at least 2 hours after thoracic biopsy and 4 hours after abdominal biopsy. Repeat imaging is indicated if clinical signs suggest a complication. Owners should be advised to restrict activity for 24 hours and to monitor for lethargy, inappetence, respiratory difficulty, or abdominal distension. The [American College of Veterinary Radiology](https://acvr.org/) publishes practice standards that address image-guided intervention safety and quality assurance. ## Documentation and Reporting The procedure report should include the patient identification, lesion location and CT characteriztics, needle type and gauge, number of samples obtained, sample handling and submission details, and any complications encountered. Representative CT images showing the needle tip within the lesion should be archived. The report should also document the anesthetic events, including any changes to cardiovascular or respiratory parameters during the procedure. This documentation supports accurate interpretation of histopathologic results and provides a baseline for comparison if repeat biopsy is required. The final cytologic and histopathologic results should be correlated with the CT findings. Discrepancies between cytology and histopathology are well recognized, and a negative cytologic result does not exclude neoplasia. In the thoracic biopsy study, cytology was falsely negative in a substantial proportion of cases that were subsequently diagnosed by histopathology [Clinical Value of CT-Guided Fine Needle Aspiration and Tissue-Core Biopsy of Thoracic Masses in the Dog and Cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). When cytology and histopathology disagree, the histopathologic diagnosis should generally be considered definitive, and the case should be reviewed with the pathologist if the discrepancy affects treatment decisions. ## Recognized Complications and Early Detection Pneumothorax is the most frequently reported complication of CT-guided thoracic sampling. In a series of 62 dogs and cats undergoing CT-guided fine-needle aspiration and tissue-core biopsy of thoracic masses, mild pneumothorax occurred in 16 cases, with an overall complication rate of 30.6% [Clinical value of CT-guided fine needle aspiration and tissue-core biopsy of thoracic masses in the dog and cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). Most pneumothoraces are small and self-limiting, but they can progress to tension physiology in patients with positive-pressure ventilation or pre-existing pulmonary disease. Detection relies on acquiring a limited helical scan through the thorax immediately after needle withdrawal, before the patient is moved from the table. Compare pre-biopsy and post-biopsy images in both lung and mediastinal windows. A visible pleural line with absent vascular markings between the lung edge and the thoracic wall confirms the diagnosis. Hemorrhage is the second most common complication. It may present as parenchymal alveolar infiltrate along the needle tract, mediastinal widening, or free pleural fluid. Contrast-enhanced CT performed before biopsy identifies vascular structures along the planned path, and the needle trajectory should be adjusted to avoid them. Post-procedural scans should be evaluated for new hyperattenuating fluid. Mild hemorrhage along the tract is usually inconsequential, but hemothorax with progressive opacification of the pleural space requires intervention. Other recognized complications include hemoptysis, transient bacteremia, and inadvertent puncture of non-target structures such as the esophagus, stomach, colon, gallbladder, or renal pelvis. In abdominal sampling, the risk of bile peritonitis after gallbladder puncture or septic peritonitis after bowel penetration justifies a mandatory post-procedural scan through the biopsy region. Delayed complications, including pneumothorax developing after extubation or hemorrhage becoming clinically apparent during recovery, are detected by monitoring respiratory effort, mucous membrane color, and serial thoracic auscultation in the immediate post-anesthetic period. ## Common Errors and Corrective Actions | Observation | Likely Cause | Discriminating Check | |---|---|---| | Non-diagnostic cytology, diagnostic histopathology | Sampling heterogeneity within a necrotic or cavitated lesion | Compare CT appearance of the sampled region with the histopathology report, target the enhancing periphery, not the hypoattenuating center | | Diagnostic cytology, non-diagnostic histopathology | Tissue-core obtained from necrotic or fibrotic zone, or sample lost during processing | Review the CT images to confirm the biopsy notch engaged the intended region, request serial sectioning of the core | | Repeated needle deflection during thoracic sampling | Lesion is small, deep, or adjacent to fissures, patient movement between acquisition and puncture | Confirm breath-hold technique is consistent, use a shorter, stiffer needle and re-scan immediately before sampling | | Hemorrhage obscuring the target on post-biopsy CT | Needle path crossed an intercostal vessel or pulmonary artery branch | Review the pre-biopsy contrast study for vessels along the tract, in future cases, angle the needle to cross the smallest possible lung volume | | Pneumothorax detected only on recovery | Small pleural breach sealed during positive-pressure ventilation, then opened during spontaneous breathing | Perform a post-biopsy scan before extubation, if equivocal, repeat a single slice through the most dependent portion of the thorax | Less experienced operators commonly underestimate the importance of patient positioning. The patient must be positioned so that the planned needle path is perpendicular to the CT gantry and the lesion is in the most dependent or most accessible position. A second common error is selecting a target region based on a single acquisition without accounting for respiratory motion. The lung moves several millimetres with each breath, and a lesion that appears accessible on an end-expiratory scan may shift beyond the needle tip during sampling. Re-scanning immediately before needle placement and using a breath-hold technique coordinated with the anesthetist reduces this error. ## Limitations of the Current Evidence The veterinary literature on CT-guided biopsy is dominated by retrospective case series with modest sample sizes. The largest relevant study, reporting on 62 thoracic masses in dogs and cats, found a combined diagnostic accuracy of 98.4% when cytology and histopathology were used together, but the same study reported cytology alone was diagnostic in only 69.4% of cases [Clinical value of CT-guided fine needle aspiration and tissue-core biopsy of thoracic masses in the dog and cat](https://pubmed.ncbi.nlm.nih.gov/33808888/). This discrepancy underscores the need for both sample types, but it also reflects selection bias: cases referred for CT-guided biopsy are typically those in which ultrasound-guided sampling has failed or is not feasible. Earlier work on CT-guided sampling of feline thoracic lesions reported that a cytological diagnosis of inflammation was later revised to carcinoma on lobectomy, illustrating that inflammatory aspirates from a suspected neoplastic lesion do not exclude malignancy [Use of computed tomography in the diseased feline thorax](https://pubmed.ncbi.nlm.nih.gov/12622469/). Expert opinion still differs on whether a non-diagnostic or inflammatory cytological result should prompt immediate repeat biopsy or proceed directly to surgical resection. The decision depends on the CT appearance, the clinical index of suspicion, and the owner's willingness to accept the morbidity of surgery. Comparative data on complication rates between CT-guided and ultrasound-guided thoracic sampling are limited. Studies of contrast-enhanced thoracic ultrasound have reported improved diagnostic accuracy for ultrasound-guided biopsy, but the evidence base is heterogeneous and of high risk of bias [Clinical applications of contrast-enhanced thoracic ultrasound compared to standard reference tests: a systematic review](https://pubmed.ncbi.nlm.nih.gov/32259873/). No prospective randomised trial has directly compared CT-guided and ultrasound-guided biopsy in veterinary patients, and such a trial would be difficult to design given the different patient populations typically referred for each modality. ## Referral, Consultation, and Reporting Referral to a board-certified radiologist or a specialty center is appropriate when the lesion is small, deeply located, or adjacent to major vascular structures, when the patient has a coagulopathy that cannot be corrected, or when a previous biopsy attempt has failed. The American College of Veterinary Radiology maintains resources on diagnostic imaging practice and specialty standards, and consultation with a radiologist before the procedure is advisable whenever the planned needle path crosses a structure that cannot be positively identified on the pre-biopsy study [American College of Veterinary Radiology resources](https://acvr.org/). Laboratory involvement is required when samples are intended for culture, flow cytometry, or molecular diagnostics. The laboratory should be contacted before the procedure to confirm sample handling requirements, including whether tissue should be placed in sterile saline, culture transport medium, or fixative. Cytology samples for flow cytometry must be collected into anticoagulant and transported promptly. Regulatory reporting obligations vary by jurisdiction. In most regions, complications that result in death or require surgical intervention are reportable to the relevant veterinary licensing body, and suspected adverse reactions to anesthetic drugs should be reported through the national pharmacovigilance scheme. Where a biopsied lesion is subsequently confirmed as a notifiable disease, the local animal health authority must be informed in accordance with applicable animal health standards [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). Practitioners should be familiar with the reporting requirements of their own jurisdiction and should document the procedure, the samples obtained, and any complications in the medical record without delay. ## Frequently Asked Questions ### How Should I Prioritize CT-Guided Biopsy When Ultrasound or Fluoroscopy Is Available? CT guidance is preferred when the lesion is small, deeply located, surrounded by bone or gas, or poorly visualized with ultrasound. Thoracic lesions, particularly pulmonary nodules, are often inaccessible to ultrasound unless they contact the chest wall or are associated with pleural effusion. CT provides superior spatial resolution and allows precise needle trajectory planning around vascular structures, which is especially valuable for mediastinal and hilar lesions. When ultrasound can clearly visualize the target and a safe needle path, it remains a faster and less expensive option. However, for lesions that are difficult to characterize on pre-procedural imaging, CT-guided sampling offers higher diagnostic confidence and should be selected when available. ### What Is the Minimum Equipment Needed to Perform CT-Guided Biopsy Safely? A helical or multislice CT scanner with a gantry aperture large enough to accommodate the patient is essential. A biopsy needle holder or freehand technique can be used, but a laser alignment system or grid marker improves accuracy. You need a selection of fine needles for aspiration and spring-loaded core biopsy devices. A sterile biopsy kit, local anesthetic, and sedation or general anesthesia equipment are required. For thoracic biopsies, an induction agent, oxygen source, and equipment for thoracocentesis and chest tube placement must be immediately available. Ultrasound can serve as a complementary tool for real-time needle visualization, but it is not required for CT-guided procedures. ### How Do I Decide Between Fine-Needle Aspiration and Core Biopsy for a Given Lesion? Fine-needle aspiration provides cytologic samples and is appropriate for lesions suspected to be cystic, vascular, or highly cellular, such as lymphoma. Core biopsy provides histopathologic architecture and is preferred for suspected carcinoma, sarcoma, or inflammatory disease where cytology may be nondiagnostic. In a study of thoracic masses in dogs and cats, cytology was diagnostic in 69.4% of cases while histopathology was diagnostic in 95.2%, and combining both techniques increased overall accuracy to 98.4%. For small or necrotic lesions, core biopsy may yield more representative tissue. When the lesion is adjacent to major vessels, fine-needle aspiration carries a lower risk of hemorrhage and may be attempted first. ### What Should I Do When a Pneumothorax Develops During or After Thoracic Biopsy? Mild pneumothorax is the most common complication of CT-guided thoracic biopsy, occurring in approximately 26% of cases in one study. If the patient remains stable and the pneumothorax is small, conservative management with oxygen supplementation and serial monitoring is appropriate. If respiratory effort increases or oxygen saturation declines, perform immediate thoracocentesis. Place a chest tube if air reaccumulates rapidly or if the patient requires repeated aspiration. Obtain a post-biopsy CT or thoracic radiograph before recovery to quantify the pneumothorax. Patients with pre-existing pulmonary disease or those undergoing multiple needle passes are at higher risk and should be monitored more intensively during the recovery period. ### How Should I Document the Procedure and Communicate Results to the Referring Veterinarian? Document the indication, lesion location and size, needle type and gauge, number of passes, and any complications. Record the imaging findings, including the exact needle path and final needle tip position. Note the samples obtained, their appearance, and how they were handled and submitted. Include post-procedural imaging findings and any interventions performed. Communicate preliminary results to the owner and referring veterinarian within 24 hours, and provide the final histopathology or cytology report when available. Include images of the needle in situ in the medical record and in the referral communication, as these are valuable for treatment planning and for future comparison. ### How Do I Approach CT-Guided Biopsy in a Cat With a Small Thoracic Lesion? Feline thoracic lesions often present with diffuse lobar involvement instead of discrete nodules, and CT is particularly useful for characterizing these patterns. In one case series, CT-guided fine-needle aspiration of lobar lung lesions in cats revealed carcinoma in three of four cases, although one cat with a cytologic diagnosis of inflammation was subsequently found to have carcinoma on lobectomy. This highlights the risk of sampling error in feline pulmonary disease. Use smaller gauge needles and limit the number of passes to reduce the risk of pneumothorax. Consider core biopsy when cytology is nondiagnostic, but weigh the increased complication risk. Feline patients require careful anesthetic management, and recovery should be closely monitored for respiratory compromise. ## Related Clinical & Scientific Guides * [MRI Monitoring of Brain Tumor Response to Therapy in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/mri-monitoring-brain-tumor-response-therapy-dogs) * [Ultrasound-Guided Drainage of Abscesses in Small Animals](/knowledge/veterinary-medicine/diagnostic-imaging/ultrasound-guided-drainage-abscesses-small-animals) * [Radiographic Monitoring of Total Hip Replacement in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/radiographic-monitoring-total-hip-replacement-dogs) ## References and Further Reading - [Use of computed tomography in the diseased feline thorax.](https://pubmed.ncbi.nlm.nih.gov/12622469/). 2003. - [Clinical Applications of Contrast-Enhanced Thoracic Ultrasound (CETUS) Compared to Standard Reference Tests: A Systematic Review.](https://pubmed.ncbi.nlm.nih.gov/32259873/). 2022. - [Clinical Value of CT-Guided Fine Needle Aspiration and Tissue-Core Biopsy of Thoracic Masses in the Dog and Cat.](https://pubmed.ncbi.nlm.nih.gov/33808888/). 2021. - [Non-cardiac thoracic ultrasound in 75 feline and canine patients.](https://pubmed.ncbi.nlm.nih.gov/10779076/). 2000. - [Whole body computed tomographic characteriztics of skeletal and cardiac muscular metastatic neoplasia in dogs and cats.](https://pubmed.ncbi.nlm.nih.gov/23441584/). 2013. - [High yield of bronchoscopic transparenchymal nodule access real-time image-guided sampling in a novel model of small pulmonary nodules in canines.](https://pubmed.ncbi.nlm.nih.gov/25275338/). 2015. - [American College of Veterinary Radiology Resources](https://acvr.org/). American College of Veterinary Radiology. - [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual. - [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association. ## Related Articles - [CT-Guided Biopsy of Bone Lesions in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/ct-guided-biopsy-bone-lesions-dogs-cats) - [Ultrasound-Guided Cystocentesis for Therapeutic Drainage in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/ultrasound-guided-cystocentesis-therapeutic-drainage-dogs-cats) - [Systematic Interpretation of Thoracic Radiographs in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/systematic-interpretation-thoracic-radiographs-dogs-cats) - [CT-Guided Stereotactic Radiosurgery Planning for Brain Tumors in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/ct-guided-stereotactic-radiosurgery-planning-brain-tumors-dogs) - [Ultrasound-Guided Aspiration of Cystic Lesions in Small Animals](/knowledge/veterinary-medicine/diagnostic-imaging/ultrasound-guided-aspiration-cystic-lesions-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.