Intraoperative identification of adrenal-renal fusion.

Adrenal - renal fusion is a rare entity defined as incomplete encapsulation of the adrenal gland and kidney with histologically adjacent functional tissue. This report describes the first published intraoperative identification of this anomaly during laparoscopic adrenalectomy. The patient was a 59-year-old man with chronic hypertension refractory to multiple antihypertensives found to be caused by a right-sided aldosterone-producing adrenal adenoma in the setting of bilateral adrenal hyperplasia. During laparoscopic adrenalectomy, the normal avascular plane between the kidney and adrenal gland was absent. Pathologic evaluation confirmed adrenal - renal fusion without adrenal heterotopia. Identified intraoperatively, this may be misdiagnosed as invasive malignancy, and thus awareness of this anomaly may help prevent unnecessarily morbid resection.

INTRODUCTION

Adrenal - renal fusion is a rare entity infrequently described, usually as an incidental pathologic or radiologic finding. We describe intraoperative identification of this anomaly and discuss its implications in patient management.

CASE REPORT

The patient is a 59-year-old man from Bosnia with a two decade history of hypertension refractory to a combination of four high-dose antihypertensive medications. He had concomitant hypokalemia, reaching a nadir of 2.2 mEq/L in 2009, requiring significant daily supplementation. Computed tomography (CT) of the abdomen at that time identified multiple bilateral low-attenuating adrenal lesions. Elevated plasma aldosterone-to-renin concentration ratio (PAC/PRC) confirmed primary hyperaldosteronism. The PAC/PRC worsened, and in 2013, it reached a peak of 281. A repeat CT at that time revealed an enlarging right adrenal lesion [Figure 1]. Adrenal venous sampling (AVS) revealed an aldosterone to cortisol ratio of 1.4 and 12.2 in the left and right adrenal veins, respectively, for a cortisol-corrected aldosterone ratio of approximately nine. The patient was referred to surgery given that the workup suggested a right aldosterone-producing adrenal adenoma in the setting of bilateral adrenal hyperplasia.

Figure 1

CT Abdomen revealing a smooth round low-attenuating lesion of the right adrenal gland with close approximation of the inferolateral aspect of the right adrenal gland and superior pole of the right kidney

In May 2014, the patient underwent laparoscopic right adrenalectomy. During dissection along the inferolateral portion of the adrenal gland it became apparent that the normally avascular plane between the adrenal and renal capsule was absent. Instead, there appeared to be a dense fibrotic adhesion between the surfaces of the two organs. Electrocautery dissection to include a portion of the superior pole of the kidney into the specimen was required for complete excision of the adrenal gland [Figure 2]. The patient tolerated the procedure well, postoperative laboratories revealed normokalemia without supplementation, and a 24-hour urine aldosterone level of less than 1.5 mcg/24 h confirmed the resolution of hyperaldosteronism. The patient's blood pressure was within normal limits with decreasing antihypertensive administration 1 month after excision. Pathologic evaluation of the specimen confirmed multinodular adrenal cortical hyperplasia and partial adrenal - renal fusion [Figure 3] without evidence of adrenal heterotopia.

Figure 2

Gross specimen of adrenal gland with adjacent renal tissue from the superior pole of the right kidney

Figure 3

Hematoxylin and eosin staining revealing normal appearing adrenal cortical cells (left) and renal cells, including glomeruli (right), fused, without intervening fibrous capsule

DISCUSSION

Rokitansky first described adrenal - renal fusion in 1855,[1] differentiating congenital lesions from those acquired secondary to postinflammatory fibrosis of perirenal fat. Its true incidence remains unknown as most reported cases are incidental findings on autopsy. In 1976, Honoré et al. presented the first and only case report other than this one in the surgical literature of isolated adrenal - renal fusion, proposing that the congenital lesion is likely due to failure of the retroperitoneal mesenchymal tissue to stimulate capsule formation.[2] To date, only four other cases have been reported, though all were in the setting of synchronous heterotopias.[3456] Distinction should be noted between adrenal heterotopia and adrenal - renal fusion. The former describes ectopic adrenal tissue whereas the latter describes incomplete encapsulation of those two organs involved with histologically adjacent functional tissue.

The case presented is, to our knowledge, the only published account in English literature of in vivo identification of adrenal - renal fusion. This is only the second case in the literature to describe isolated adrenal - renal fusion. From a surgical perspective, unexpected loss of plane between the two organs may be concerning for invasive malignancy, which would require a more extensive resection. Intraoperative frozen section of the fused adrenal tissue may appear similar to cystic renal cell carcinoma, leading to conversion to open radical nephrectomy, as in one previous report.[4] Ideally, the surgeon would be able to preoperatively identify which patients undergoing laparoscopic adrenalectomy may have renal - adrenal fusion. In our case, in retrospect, the adrenal gland abutted the superior pole of the kidney on CT in the area that was fused in a way that suggested the fusion that we encountered at the time of surgery. This mirrors the CT finding in the only other case of isolated adrenal - renal fusion. Further study is required to determine if this is a reliable indicator of renal - adrenal fusion. Regardless, awareness of this anomaly, during preoperative imaging and during intraoperative dissection, may help avoid the morbidity of unnecessary total or partial nephrectomy.