Widespread use of routine imaging techniques has led to an increase in detection of small (< 4 cm), solid, asymptomatic renal masses. The exact aetiology of these masses is difficult to establish preoperatively, but the general consensus is that solid renal masses should be considered malignant or potentially malignant and treated accordingly.1

It is a common practice for radiologist to recommend a CT guided fine needle aspiration cytology (FNAC) in such cases to arrive at a diagnosis. The dilemma faced by the referring doctor or the urologist is whether to get the FNAC done or proceed directly with surgery based on X-ray findings. In an attempt to answer this question, we evaluated our experience in such a situation.

Aim

The aim of our study was to evaluate the accuracy and clinical utility of CT guided FNAC for small, solid renal masses.

Material and Methods

We retrospectively assessed 12 patients with focal solid renal masses of less than 6 cm size who were seen over a period of one year. Out of the 12, three patients were referred to us for further management after undergoing CT guided FNAC elsewhere.

Results

The renal mass size in these 3 patients was less than 4 cm and all were incidentally detected. Metastatic work up in all the patients was negative. The CT scan picture below shows less than 4 cm size renal mass with FNAC needle in-situ (Fig. 1).

Histology report in these 3 patients was inconclusive. With the CT picture showing a solid renal mass, partial nephrectomy was contemplated in all three patients. The surgery was performed less than 7 days after biopsy. Partial nephrectomy was planned, but ultimately we did a total nephrectomy due to the distorted surgical planes and perinephric haematoma post FNAC procedure. It was very difficult to identify tumour free surgical margins on account of extensive perinephric haematoma extending upto the mesocolon (Fig. 2). Histology report in all the patients was renal cell carcinoma, low grade variety.

Out of the remaining nine patients who did not had FNAC procedure, 7 patients underwent radical nephrectomy for tumour between 4-6 cm and in 2 patients partial nephrectomy for tumour < 4 cm was performed.

Discussion

The differential diagnosis of renal masses on CT scan can be renal malignancy, oncocytoma, angiomyolipoma, renal abscess, complex renal cyst or lymphoma. The accuracy of CT scan in establishing a diagnosis for solid renal masses is around 95-97%.2 Nowadays, for small < 4 cm solid renal masses partial nephrectomy is advocated.2 In our study 25% cases were subjected to preoperative FNAC for < 6 cm renal masses and all underwent radical nephrectomy instead of partial nephrectomy due to distorted surgical planes and perinephric haematoma.

Sensitivity and specificity of FNAC for determination of malignancy in renal masses is between 80-85%.2 Negative predictive value is also around 80%. Core biopsies would always be more informative than FNAC but are usually associated with more complications of bleeding.

General complications of CT guided FNAC procedure are2:

1. Haemorrhage - perinephric haematoma
2. Infection
3. Lung complications like pneumothorax
4. Tumour seeding of the needle tract (0.01%)
5. More false negative results due to insufficient material3

1. 1. Renal abscess/Infected cyst
2. Lymphoma
3. Suspected non renal cancer metastatic to the kidney
4. Widespread metastatic/inoperable disease to establish the diagnosis of renal cancer.

Solitary small renal masses should be treated as potentially malignant tumours and a partial nephrectomy (nephron sparing surgery) is indicated in such cases. FNAC does not help in diagnostic workup in such cases and can be misleading. Additionally it causes significant local haematoma resulting in a planned partial nephrectomy being converted to a total nephrectomy.

Conclusion

From our study we can say that FNAC for small solid renal masses has no beneficial effect in most cases. It has also been found to cause more local damage thus preventing a conservative operation from being performed.

References

1. Truang LD, Todd TD, Dhurandhar B, et al. Fine needle aspiration of renal masses in adults: analysis of results and diagnostic problems in 108 cases. Diagn Cytopathol 1999; 20 (6) : 339-49.
2. Campbell’s Textbook of Urology : 8th Edition, Volume 4, 2701-2.
3. Juul N, Pederson S, Granvall S, et al. Ultrasonically guided fine needle aspiration biopsy of renal masses. J Urol 1985; 133 (4) : 579-81.