[Renal Biopsy]

Abstract

The extent of renal biopsy indication is being widened because of the increasing incidence of incidental renal masses; the increasing treatment options for renal cell carcinoma, including ablation therapy and novel targeted treatment; and the increasing incidence of kidney transplantation. However, percutaneous renal biopsy is technically difficult, particularly for beginners, because the skin-to-organ distance is relatively longer than those associated with other organs. In the present review, we will discuss the indications, technical considerations, efficacy, and complications of renal biopsy. Furthermore, we share practical tips of renal biopsy through many examples to help radiologists perform renal biopsy safely and effectively in various situations.

Fig. 1. A 59-year-old female presented with renal mass.

A, B. Axial CT reveals a 3.3 cm exophytic hypervascular mass in the right kidney. The mass demonstrates mushroom shape, suggestive of angiomyolipoma, but no definite fat is found in precontrast image. C. On US, the mass exhibits hypoechogenecity (arrowheads), which is inconsistent with angiomyolipoma. However, percutaneous biopsy revealed that the mass was angiomyolipoma.

Fig. 2. A 54-year-old female presented with ill-defined enhancing mass in right kidney.

A. During the follow up, the size of the mass (arrowheads) spontaneously decreased. The differential diagnoses were inflammatory pseudotumor and renal cell carcinoma. Axial CT helped us plan the approach to the mass through the paraspinal muscle (arrow). B. In an oblique axial US image in the same patient, we could see the same mass in medial aspect of right kidney (arrowheads). As intervening vessels were absent in the approach route (arrow), we could assume that biopsy would be safe. C. Percutaneous biopsy was performed through the paraspinal muscle without complications. Histopathology confirmed tubulointerstitial nephritis with interstitial fibrosis, without evidence of carcinoma.

Fig. 3. A 79-year-old male presented with an infiltrative soft tissue mass involving the left perirenal space and renal sinus highly suggestive of lymphoma.

A. Approaching the renal sinus directly (dashed arrow) would have been dangerous because of a risk of injuring the main renal vessels and collecting system. Instead, approaching the perirenal space was considered safer (arrow). B. US reveals a hypoechoic perirenal mass surrounding the kidney (arrowheads). Biopsy was taken from the inside of the mass without penetrating the renal cortex or renal sinus. The final pathological diagnosis was extranodal marginal zone B cell lymphoma of mucosa-associated lymphoid tissue type.

Fig. 4. A 50-year-old female had a history of leiomyosarcoma.

A. A solid and cystic mass newly appeared in the left kidney during the follow-up. Metastasis was suspected, and the clinician planned percutaneous biopsy. B. The endophytic mass was biopsied (arrowheads) without penetrating the renal sinus. A histopathological diagnosis of metastatic leiomyosarcoma was confirmed.

Fig. 5. A 63-year-old female demonstrated ill-defined soft tissue mass in the right kidney.

A. Because the mass is located on the anterior aspect of the kidney, a posterior approach would have required a longer route and might have penetrated the renal sinus (dashed arrow). In this situation, an anterior approach (arrow) would have been safer and shorten the skin-to-target distance unless an intervening bowel was present. B. In the supine position, we confirmed that no intervening bowel was present between the abdominal wall and kidney. Biopsy was successfully performed via the transabdominal approach. The final pathology was confirmed as urothelial carcinoma with squamous differentiation.

Fig. 6. A 62-year-old male with enhancing mass in left pelvicalyces.

A. Percutaneous biopsy of the collecting system is usually not recommended because a risk of renal vessel injury and collecting system rupture. However, in the present case, we could plan the biopsy from within the mass (arrowheads) without touching the renal vessels or penetrating the collecting system (arrow). B. Doppler US confirms no large vessels in the biopsy trajectory (arrow). C. We inserted the needle with the same angle to the targeted renal calyx to prevent the needle tip from penetrating the opposite side of calyceal wall after firing. After penetrating the renal parenchyma, biopsy was performed from within the mass. The mass was confirmed as papillary urothelial carcinoma.

Fig. 7. A 24-year-old male with solid and cystic mass in the left kidney.

A. Metastatic lymph nodes are identified in paraaortic area (arrowheads), which is uncommon for renal cell carcinoma. B. To obtain adequate tissue for a diagnosis, we avoided performing a biopsy in the cystic portion. The needle was targeted to the hyperechoic solid area of the mass (arrowheads). Histopathology confirmed a diagnosis of fumarate hydratase deficient renal cell carcinoma.

Fig. 8. A 66-year-old male presented with a necrotic mass in left kidney.

A. There is confusion whether the mass is a renal mass with severe necrosis or urothelial mass with calyceal dilatation and renal parenchymal invasion. The viable tumor is present in the peripheral portion of the mass (arrowheads). B. The needle was targeted towards the peripheral portion of the mass (arrowheads). If the biopsy was performed in the central portion of the mass, only necrotic tissue would have been obtained. The final pathological diagnosis was urothelial carcinoma.

Fig. 9. An example of cortical tangential biopsy.

A. The needle is inserted parallel to the outer capsule (dashed line), just beyond the edge of medullary pyramid. The advantage of the cortical tangential approach is that it is not limited to any one region of the renal parenchyma. The operator can choose the needle insertion site and angle depending on the preference and the transplant position (line). No acute rejection was evident in the final pathology. B-D. CT and US of the transplanted kidney biopsy using cortex-only view. The lateral cortex of interpolar or lower pole of the transplanted kidney is usually targeted because the skin-to-target distance is the shortest (arrows). However, the biopsy site is not limited to any particular region in the kidney (dashed arrows), like the cortical tangential approach. The needle trajectory can avoid the inferior epigastric artery (arrowhead), but the superficial branch of the superficial circumflex iliac artery (dashed circle) and the iliac branch of the iliolumbar artery (circle) should not be penetrated. The final diagnosis was active antibody-mediated rejection of transplanted kidney.

Fig. 10. An example of arteriovenous fistula after renal biopsy.

A. A 71-year-old female who underwent biopsy of a transplanted kidney using the cortex-only view. B. After the biopsy, a focal lesion with an aliasing artifact is detected along the needle pathway (arrowhead). C. The waveform confirms an arterialized draining vein, suggestive of a post-biopsy arteriovenous fistula.

Fig. 11. A 21-year-old female with a history of transplanted kidney biopsy.

A. Grayscale US reveals an anechoic round lesion (arrowheads), mimicking a renal cyst. B. On Doppler US, the lesion exhibits vascular flow with an aliasing artifact, confirming the lesion as pseudoaneurysm. C. On angiography, the pseudoaneurysm is demonstrated as a contrast-filling sac (arrowhead). The lesion was treated by coil embolization.