# Image-Guided Biopsy: Principles and Complication Recognition

## Introduction

Image-guided percutaneous biopsy is one of the most important procedures performed by diagnostic and interventional radiologists. It provides tissue diagnosis with high accuracy while minimizing surgical morbidity. The choice of imaging guidance -- **ultrasound**, **CT**, or **fluoroscopy** -- depends on lesion visibility, location, and operator experience. Understanding needle types, biopsy techniques, and potential complications is essential for safe practice.

## Indications and Contraindications

### Common Indications

Common indications include tissue characterization of indeterminate masses (lung, liver, kidney, lymph node, bone), staging of known malignancy, diagnosis of infection or inflammatory disease, and assessment of diffuse parenchymal disease (such as liver fibrosis grading).

### Absolute Contraindications

Absolute contraindications include **lack of a safe access route** (interposed vital structure), an **uncooperative patient** who cannot maintain position or breath-hold, and **suspected hydatid cyst** or **vascular lesion** (such as hemangioma), where biopsy carries risk of anaphylaxis or hemorrhage.

### Relative Contraindications

**Coagulopathy** with INR greater than 1.5 or platelets less than 50,000/microL (thresholds vary by site; SIR guidelines provide specific recommendations) is a relative contraindication. **Anticoagulant/antiplatelet therapy** must be managed per institutional and SIR periprocedural guidelines. **Severe pulmonary hypertension** is a relative contraindication for transthoracic biopsy.

## Imaging Guidance Selection

| Modality | Strengths | Limitations |
|----------|-----------|-------------|
| Ultrasound | Real-time, portable, no radiation, low cost | Limited by air, bone, depth; operator dependent |
| CT | Excellent spatial resolution, deep lesions, bone | Radiation, not real-time (intermittent) |
| CT fluoroscopy | Near real-time CT guidance | Higher radiation to operator and patient |
| MRI | Superior soft tissue contrast, no radiation | Expensive, limited availability, MRI-compatible needles required |

**Ultrasound** offers real-time visualization, portability, no radiation, and low cost, but is limited by air, bone, depth, and operator dependence. **CT** provides excellent spatial resolution for deep lesions and bone but involves radiation exposure and is not real-time (intermittent). **CT fluoroscopy** provides near real-time CT guidance but delivers higher radiation to operator and patient. **MRI** offers superior soft tissue contrast with no radiation but is expensive, has limited availability, and requires MRI-compatible needles.

## Needle Types

### Fine-Needle Aspiration (FNA)

FNA uses **20-25 gauge** needles and yields cytology specimens (individual cells). It has a lower complication rate and is suitable for deep or vascular lesions. It is commonly used for thyroid, lymph node, and pancreatic lesions.

### Core Needle Biopsy (CNB)

CNB uses **14-20 gauge** needles with a cutting mechanism and yields histology specimens with preserved tissue architecture. It provides a higher diagnostic yield for lymphoma, fibrosis staging, and lesions requiring architectural assessment. **Spring-loaded automated** or **semi-automated** devices are most commonly used.

### Coaxial Technique

In the coaxial technique, an outer introducer needle is positioned near the target, and multiple core samples are obtained through the coaxial sheath without re-traversing normal tissue. This reduces the number of pleural punctures in lung biopsy and allows tract embolization.

![Diagram of coaxial biopsy technique showing outer introducer needle and inner cutting biopsy needle obtaining core specimens from a lung nodule](coaxial-biopsy-technique.png)

## Site-Specific Considerations

### Lung Biopsy

CT guidance is standard for pulmonary nodules. Patient positioning with the lesion-side down (dependent) when possible reduces pneumothorax risk. The number of pleural passes and traversal of fissures or bullae should be minimized, and large vessels should be avoided. The **pneumothorax rate** is 15-25%, with chest tube required in approximately 5-15%.

### Liver Biopsy

Ultrasound guidance is preferred for focal lesions. An intercostal approach should avoid the **inferior margin of the rib** to protect the intercostal neurovascular bundle. A transpleural approach is acceptable but increases pneumothorax risk. For diffuse disease staging, a **16-gauge core** with 2 cm or greater specimen length and 11 or more portal tracts is adequate.

### Kidney Biopsy

Native renal biopsies typically target the **lower pole** to minimize risk to the hilum. The patient is positioned prone with real-time ultrasound guidance. An **18-gauge automated core needle** is standard. Post-biopsy monitoring with ultrasound for perinephric hematoma is performed.

### Bone Biopsy

CT guidance with **bone biopsy needles** (such as Ostycut or Bonopty) is standard. Coaxial systems allow obtaining multiple specimens. The approach should avoid neurovascular structures, and for vertebral body lesions, a transpedicular approach is standard.

## Complications and Their Recognition

### Hemorrhage

Hemorrhage is the most common serious complication. Risk increases with larger needle gauge, number of passes, and coagulopathy. **Imaging findings** include an expanding hematoma on post-biopsy imaging, perinephric or perihepatic fluid, and hemothorax. Management involves observation for small hematomas and embolization or surgery for hemodynamically significant bleeding.

### Pneumothorax

Pneumothorax is specific to thoracic biopsies. A **post-procedure CXR** is mandatory, typically 1-4 hours after lung biopsy. A small pneumothorax (less than 2 cm apex-to-cupola distance) that is stable and asymptomatic can be observed with serial CXRs. An enlarging or symptomatic pneumothorax requires aspiration or chest tube placement.

### Infection

Infection is rare with proper sterile technique (less than 1%) and presents as abscess formation at the biopsy site.

### Tumor Tract Seeding

Tract seeding is rare but has been reported with hepatocellular carcinoma, mesothelioma, and renal cell carcinoma. The coaxial technique and tract ablation/embolization reduce this risk.

### Organ-Specific Complications

Organ-specific complications include **pancreatitis** after pancreatic biopsy, **bile leak/biloma** after liver biopsy, and **air embolism** after lung biopsy (rare but potentially fatal).

![Post-biopsy chest radiograph showing a moderate right-sided pneumothorax following CT-guided lung biopsy](post-biopsy-pneumothorax-cxr.png)

![CT image demonstrating perinephric hematoma following renal biopsy](perinephric-hematoma-post-biopsy.png)

## Key Clinical Pearls

Always review **coagulation parameters** (INR, platelets, PTT) and medication list before any biopsy; follow SIR consensus guidelines for anticoagulant management. The **coaxial technique** is strongly recommended for lung biopsies to reduce pneumothorax and enable tract embolization (such as with blood patch or gelatin sponge). For suspected **lymphoma**, core biopsy is preferred over FNA because architectural assessment is required for accurate subtyping. After lung biopsy, position the patient **biopsy-site down** for the observation period to tamponade the pleural puncture site. **Air embolism** after lung biopsy presents with acute neurological symptoms or cardiovascular collapse; place the patient in left lateral decubitus and Trendelenburg position immediately.

## References

1. Patel IJ, Davidson JC, Nikolic B, et al. Consensus Guidelines for Periprocedural Management of Coagulation Status and Hemostasis Risk in Percutaneous Image-Guided Interventions. *J Vasc Interv Radiol*. 2019;30(8):1168-1184.
2. DiBardino DM, Yarmus LB, Semaan RW. Transthoracic Needle Biopsy of the Lung. *J Thorac Dis*. 2015;7(Suppl 4):S304-S316.
3. Rockey DC, Caldwell SH, Goodman ZD, et al. Liver Biopsy. *Hepatology*. 2009;49(3):1017-1044.
4. Wu CC, Maher MM, Shepard JO. Complications of CT-Guided Percutaneous Needle Biopsy of the Chest. *Radiographics*. 2011;31(6):1737-1749.